Atmospheric Environment (v.145, #C)

Insights into different nitrate formation mechanisms from seasonal variations of secondary inorganic aerosols in Shanghai by Ye Tao; Xingnan Ye; Zhen Ma; Yuanyuan Xie; Ruyu Wang; Jianmin Chen; Xin Yang; Shuqin Jiang (1-9).
The dominant mechanisms for the formation of fine particulate nitrate during four seasons were proposed by evaluating the correlations between [NO3 ]/[SO4 2−] and [NH4 +]/[SO4 2−]. Size-resolved aerosols were collected in Shanghai from April 2013 to January 2014. The concentration of fine particulate nitrate was below one tenth of the concentration of sulfate in summer, whereas fine particulate nitrate dominated over sulfate in winter. Influenced by aged sea salt aerosols, the molar ratio of [Na+]/[NH4 +] reached 53 ± 49% and the depletion of chloride was very significant (0.83) during autumn. In spring, the increase of nitrate concentration became evident for [NH4 +]/[SO4 2−]>2, indicating that sulfate is fully neutralized. During summertime, nighttime hydrolysis of N2O5 dominated the fine particulate nitrate formation. The thresholds of [NH4 +]/[SO4 2−] for nitrate formation in autumn and winter were wrongly characterized by the linear regression between [NO3 ]/[SO4 2−] and [NH4 +]/[SO4 2−], because considerable amounts of Na2SO4 and NH4Cl were present. Replaced by free ammonium in the function equation, it was established that the winter and spring aerosols shared the same nitrate formation mechanism. On the basis of free sulfate, it was evident that both homogeneous neutralization and hydrolysis of N2O5 mechanisms were involved during autumn.Display Omitted
Keywords: Nitrate formation; Chloride depletion; Free sulfate; N2O5;

Estimating ship emissions based on AIS data for port of Tianjin, China by Dongsheng Chen; Yuehua Zhao; Peter Nelson; Yue Li; Xiaotong Wang; Ying Zhou; Jianlei Lang; Xiurui Guo (10-18).
A detailed exhaust emission inventory of ships by using Automatic Identification System (AIS) data was developed for Tianjin Port, one of the top 10 world container ports and the largest port in North China. It was found that in 2014, ship emissions are 2.93 × 104, 4.13 × 104, 4.03 × 103, 3.72 × 103, 1.72 × 103 and 3.57 × 103 tonnes of SO2, NOx, PM10, PM2.5, NMVOC and CO respectively, which are equivalent to 11.07%, 9.40%, 2.43%, 3.10%, 0.43% and 0.16% respectively of the non-ship anthropogenic totals in Tianjin. The total CO2 emissions is approximately 1.97 × 106 tonnes. The container ships and dry bulk cargo ships contributed about 70% of the total ship emissions of NOx, SO2 and PM10. Pollutants were mainly emitted during cruise and hotelling modes, and the highest intensities of emissions located in the vicinity of fairways, berth and anchorage areas in Tianjin Port. Distinctive difference between the lowest (February) and the highest (September) monthly emissions is due to the adjustment of freight volume during the Chinese New Year and the months before and after it.
Keywords: Ship emissions; Automatic identification system; Tianjin port;

Near-source grid-based measurement of CO and PM2.5 concentration during a full-scale fire experiment in southern European shrubland by J.H. Amorim; J. Valente; P. Cascão; L.M. Ribeiro; D.X. Viegas; R. Ottmar; A.I. Miranda (19-28).
There is limited research on the exposure of wildland firefighters to smoke because of the operational obstacles when monitoring air pollutants in the field. In this work, a grid of portable sensors was used to measure PM2.5 and CO concentrations in the near-source region during the burn of two shrubland research blocks in Central Portugal. Strong spatial variability of smoke levels was observed in the analysis of the ratios between mean concentrations of neighbouring sensors, with values as high as 4.4 for PM2.5 and 7.4 for CO. These large gradients were registered at a distance of only 5 m suggesting that considerable differences on individual exposure can occur depending on the location of that individual in relation to the smoke plume trajectory. Also, peak events of 2–3 times the mean were observed in periods exceeding 6 min. In the two experiments, the average concentrations of both PM2.5 and CO were higher during smouldering, which represents a risk of acute exposure due to the closer proximity of firefighters to the emission source during mop-up, stressing the importance of wearing portable gas detectors for managing critical exposure. The collected data constitutes a step forward in the effort to understand the mechanisms controlling the exposure during firefighting operations, by providing a source of information on near-ground concentration fluctuations within a biomass-burning smoke plume at a fine spatial-temporal resolution.
Keywords: Fire experiments; Smoke emissions; Smoke plume; Firefighter exposure; Fire safety; Portable sensor;

A comprehensive approach for the evaluation and comparison of emission inventories in Madrid by Michel Vedrenne; Rafael Borge; Julio Lumbreras; María Encarnación Rodríguez; David de la Paz; Javier Pérez; Juan Manuel de Andrés; Christina Quaassdorff (29-44).
Emission inventories provide a description of the polluting activities that occur across a specific geographic domain, and are widely used as input for air quality modelling for the assessment of compliance with environmental legislation. The spatial scale to which these inventories are referred has an influence in the representativeness of the emission estimates, as these are underpinned by a number of considerations and data with different levels of granularity. This study proposes a comprehensive framework for the evaluation of emission inventories that allows identifying methodological issues by examining differences in performance to a chemical transport model (CTM) when such inventories are used as input. To demonstrate the approach, a comparison between the national and regional emissions inventories for the Autonomous Community of Madrid (ACM) was carried out (NEI and REI respectively). The analysis revealed discrepancies in compilation methodologies for the domestic sector (SNAP 02), industrial combustion (SNAP 03), road traffic (SNAP 07) and other mobile sources (SNAP 08); most of the differences were originally caused by taking into account different activity variables, fuel mixes, and spatial disaggregation and allocation proxies. The granularity of the base data (statistics, fuel consumption, facilities, etc.) proved to be an essential limiting factor, which means that whenever bottom-up approaches were followed, the description of emission sectors tended to be more accurate.
Keywords: Air quality modelling; Urban emission inventory; Scale interaction; Harmonisation; Uncertainties; Madrid;

Anthropogenic sulphur dioxide load over China as observed from different satellite sensors by M.E. Koukouli; D.S. Balis; Ronald Johannes van der A; N. Theys; P. Hedelt; A. Richter; N. Krotkov; C. Li; M. Taylor (45-59).
China, with its rapid economic growth and immense exporting power, has been the focus of many studies during this previous decade quantifying its increasing emissions contribution to the Earth's atmosphere. With a population slowly shifting towards enlarged power and purchasing needs, the ceaseless inauguration of new power plants, smelters, refineries and industrial parks leads infallibly to increases in sulphur dioxide, SO2, emissions. The recent capability of next generation algorithms as well as new space-borne instruments to detect anthropogenic SO2 loads has enabled a fast advancement in this field. In the following work, algorithms providing total SO2 columns over China based on SCIAMACHY/Envisat, OMI/Aura and GOME2/MetopA observations are presented. The need for post-processing and gridding of the SO2 fields is further revealed in this work, following the path of previous publications. Further, it is demonstrated that the usage of appropriate statistical tools permits studying parts of the datasets typically excluded, such as the winter months loads. Focusing on actual point sources, such as megacities and known power plant locations, instead of entire provinces, monthly mean time series have been examined in detail. The sharp decline in SO2 emissions in more than 90%–95% of the locations studied confirms the recent implementation of government desulphurisation legislation; however, locations with increases, even for the previous five years, are also identified. These belong to provinces with emerging economies which are in haste to install power plants and are possibly viewed leniently by the authorities, in favour of growth. The SO2 load seasonality has also been examined in detail with a novel mathematical tool, with 70% of the point sources having a statistically significant annual cycle with highs in winter and lows in summer, following the heating requirements of the Chinese population.
Keywords: Sulphur dioxide; China; Satellite remote sensing; OMI; SCIAMACHY; GOME2A; Trends; Seasonality;

This study examines the contribution of 20% reduction in anthropogenic emissions from the energy, industry and transport sectors in South Asia to global distribution of ozone (O3) during summer and winter monsoon seasons. We used Model for Ozone and Related chemical Tracers (MOZART-4) and Hemispheric Transport of Air Pollution version-2 (HTAP-v2) emission inventory to simulate global O3 for five different sensitivity simulations. Contribution from different emission sectors is identified on the basis of the differences between model calculations with unperturbed emissions (Base-case) and the emissions reduced by 20% by different sectors over South Asia. During the summer season, 20% reduction in emissions from transportation sector contributes maximum decrease in O3 of the order of 0.8 ppb in the center of Asian Summer Monsoons (ASM) anticyclone at 200 hPa. Response to Extra Regional Emission Reduction (RERER) is found to vary between 0.4 and 0.7 inside the ASM, indicating that 40–70% of O3 trapped inside the anticyclone is influenced by the emission from non-Asian emissions, and the remaining O3 is influenced by South-Asian emissions. During winter, 20% reduction in emissions from transport sector contributes decrease in O3 at surface up to 0.5 ppb over South Asia and outflow region (the Arabian Sea and the Bay of Bengal). RERER values vary between 0 and 0.2 over South Asia indicating the predominant impact of local emissions reduction on surface O3 concentration than reduction in foreign emissions. We have also examined the health benefits of reduction in regional, global and sectoral emissions in terms of decrease in excess number of COPD (Chronic Obstructive Pulmonary Disease) cases due to O3 exposure. We find that more health benefits can be achieved if global emissions are decreased by 20%.
Keywords: Chemical transport modeling; HTAP; Ozone; Emissions; Health;

The polar iodine paradox by Alfonso Saiz-Lopez; Christopher Shawn Blaszczak-Boxe (72-73).

Optimum quantification temperature for total, organic, and elemental carbon using thermal-coulombimetric analysis by Harry Alvarez-Ospina; Oscar Peralta; Telma Castro; María I. Saavedra (74-80).
The quantification of total (TC), organic (OC), elemental carbon (EC), and OC/TC, EC/TC ratios is useful to determine the original sources of carbonaceous particles, so the importance of using appropriate standards is often crucial in atmospheric sciences, and the National Institute of Standards and Technology (NIST) offers good analytes. The Standard Reference Material (SRM) Urban Particulate Matter has a similar matrix as in the airborne aerosols of urban atmospheres and a well-known composition. The optimum quantification temperature analysis for carbon content of SRM 1648a and 1649b using a coulometric method (CM5300 and CM5014) is 500 °C for OC and 700 °C for TC. We also evaluated the repeatability and reproducibility provided by the instrument. It should be pointed out that SRM 1649b has no OC or TC quantification in its Certificate of Analysis, so this study may serve as a basis for future analysis of carbon content of atmospheric aerosols.
Keywords: Total carbon; Organic carbon; SRM 1648a; SRM 1649b; Coulometric method;

A Portable Emissions Measurement System (PEMS) study of NOx and primary NO2 emissions from Euro 6 diesel passenger cars and comparison with COPERT emission factors by Rosalind O'Driscoll; Helen M. ApSimon; Tim Oxley; Nick Molden; Marc E.J. Stettler; Aravinth Thiyagarajah (81-91).
Real world emissions of oxides of nitrogen (NOx) often greatly exceed those achieved in the laboratory based type approval process. In this paper the real world emissions from a substantial sample of the latest Euro 6 diesel passenger cars are presented with a focus on NOx and primary NO2. Portable Emissions Measurement System (PEMS) data is analysed from 39 Euro 6 diesel passenger cars over a test route comprised of urban and motorway sections. The sample includes vehicles installed with exhaust gas recirculation (EGR), lean NOx traps (LNT), or selective catalytic reduction (SCR). The results show wide variability in NOx emissions from 1 to 22 times the type approval limit. The average NOx emission, 0.36 (sd. 0.36) g km−1, is 4.5 times the Euro 6 limit. The average fraction primary NO2 (fNO2) is 44 (sd. 20) %. Higher emissions during the urban section of the route are attributed to an increased number of acceleration events. Comparisons between PEMS measurements and COPERT speed dependent emissions factors show PEMS measurements to be on average 1.6 times higher than COPERT estimates for NOx and 2.5 times for NO2. However, by removing the 5 most polluting vehicles average emissions were reduced considerably.
Keywords: Euro 6 emission standards; NOx; Primary NO2; Diesel exhaust aftertreatment; COPERT;

Organic fertilizer may not only improve soil quality but may also contribute to climate protection by increasing carbon sequestration in agricultural ecosystems. A 3-yr study was conducted with ten consecutive vegetable crops in intensively managed vegetable cropping systems in southeastern China to examine the effects of organic fertilizer application (ORGA) on net global warming potential (net GWP) after accounting for carbon dioxide equivalent emissions from all sources including methane (CH4) and nitrous oxide (N2O) emissions, agrochemical inputs and farm operations and sinks (i.e., soil organic carbon (SOC) sequestration derived from the net ecosystem carbon budget). Results indicated that ORGA significantly increased ecosystem respiration by 13.9% without obvious effects on CH4 and N2O emissions as compared to local conventional chemical fertilization (CHEM). The SOC sequestration rates during the 3-year observation period were estimated at −0.52 t C ha−1 for the control, −0.42 t C ha−1 for the CHEM plot and 0.27 t C ha−1 for the ORGA plot, respectively, and thus contributed significantly to the net GWP. Overall, compared with CHEM, the ORGA significantly decreased net GWP and greenhouse gas intensity by 15.3% and 27.4%, respectively. Our findings suggest that higher yields and lower greenhouse gas intensities and carbon costs can be achieved by substituting chemical nitrogen fertilizers with organic fertilization strategies.
Keywords: Intensive vegetable production; Organic fertilizer; Net ecosystem carbon budget; Net global warming potential; Greenhouse gas intensity;

Characteristics of PM2.5 concentrations across Beijing during 2013–2015 by Stuart Batterman; Lizhong Xu; Feng Chen; Fang Chen; Xuefen Zhong (104-114).
High concentrations of particulate matter (PM2.5) and frequent air pollution episodes in Beijing have attracted widespread attention. This paper utilizes data from the new air pollution network in China to examine the current spatial and temporal variability of PM2.5 at 12 monitoring sites in Beijing over a recent 2-year period (April 2013 to March 2015). The long term (2-year) average concentration was 83 μg m−3, well above Chinese and international standards. Across the region, annual average concentrations varied by 20 μg m−3 (25% of the average level), with lower levels in suburban areas compared to periurban and urban areas, which had similar concentrations. The spatial variation in PM2.5 concentrations was associated with several land use and economic variables, including the fraction of vegetated land and building construction activity, which together explained 71% of the spatial variation. Daily air quality was characterized as “polluted” (above 75 μg m−3) on 36–47% of days, depending on site. There were 77 pollution episodes during the study period (defined as two or more consecutive days with Beijing-wide 24-hour average concentrations over 75 μg m−3), and 2 to 5 episodes occurred each month, including summer months. The longest episode lasted 9 days and daily concentrations exceeded 450 μg m−3. Daily PM2.5 levels were autocorrelated (rlag1 = 0.516) and associated with many meteorological variables, including barometric pressure, relative humidity, hours of sunshine, surface and ambient temperature, precipitation and scavenging coefficient, and wind direction. Parsimonious models with meteorological and autoregressive terms explained over 60% of the variation in daily PM2.5 levels. The first autoregressive term and hours of sunshine were the most important variables in these models, however, the latter variable is PM2.5-dependent and thus not an explanatory variable. The present study can serve as a baseline to compare the improved air quality in Beijing expected in future years.
Keywords: Particulate matter; PM2.5; Spatial variation; Temporal variation; Beijing; Episode;

Size distribution of particle-phase sugar and nitrophenol tracers during severe urban haze episodes in Shanghai by Xiang Li; Li Jiang; Le Phuoc Hoa; Yan Lyu; Tingting Xu; Xin Yang; Yoshiteru Iinuma; Jianmin Chen; Hartmut Herrmann (115-127).
In this study, measurements of size-resolved sugar and nitrophenol concentrations and their distributions during Shanghai haze episodes were performed. The primary goal was to track their possible source categories and investigate the contribution of biological and biomass burning aerosols to urban haze events through regional transport. The results showed that levoglucosan had the highest concentration (40–852 ng m−3) followed by 4-nitrophenol (151–768 ng m−3), sucrose (38–380 ng m−3), 4-nitrocatechol (22–154 ng m−3), and mannitol (5–160 ng m−3). Size distributions exhibited over 90% of levoglucosan and 4-nitrocatechol to the total accumulated in the fine-particle size fraction (<2.1 μm), particularly in heavier haze periods. The back trajectories further supported the fact that levoglucosan was linked to biomass-burning particles, with higher values of associated with air masses passing from biomass burning areas (fire spots) before reaching Shanghai. Other primary saccharide and nitrophenol species showed an unusually large peak in the coarse-mode size fraction (>2.1 μm), which can be correlated with emissions from local sources (biological emission). Principal component analysis (PCA) and positive matrix factorization (PMF) revealed four probable sources (biomass burning: 28%, airborne pollen: 25%, fungal spores: 24%, and combustion emission: 23%) responsible for urban haze events. Taken together, these findings provide useful insight into size-resolved source apportionment analysis via molecular markers for urban haze pollution events in Shanghai.
Keywords: Sugars; Nitrophenols; Size distributions; Source apportionment; Urban haze; Shanghai;

Source apportionment advances using polar plots of bivariate correlation and regression statistics by Stuart K. Grange; Alastair C. Lewis; David C. Carslaw (128-134).
This paper outlines the development of enhanced bivariate polar plots that allow the concentrations of two pollutants to be compared using pair-wise statistics for exploring the sources of atmospheric pollutants. The new method combines bivariate polar plots, which provide source characteristic information, with pair-wise statistics that provide information on how two pollutants are related to one another. The pair-wise statistics implemented include weighted Pearson correlation and slope from two linear regression methods. The development uses a Gaussian kernel to locally weight the statistical calculations on a wind speed-direction surface together with variable-scaling. Example applications of the enhanced polar plots are presented by using routine air quality data for two monitoring sites in London, United Kingdom for a single year (2013). The London examples demonstrate that the combination of bivariate polar plots, correlation, and regression techniques can offer considerable insight into air pollution source characteristics, which would be missed if only scatter plots and mean polar plots were used for analysis. Specifically, using correlation and slopes as pair-wise statistics, long-range transport processes were isolated and black carbon (BC) contributions to PM2.5 for a kerbside monitoring location were quantified. Wider applications and future advancements are also discussed.
Keywords: Air quality; Relationships; Robust regression; Particulate matter; Black carbon;

Impact of meteorology on fine aerosols at Lucas Heights, Australia by Jagoda Crawford; Scott Chambers; David D. Cohen; Alastair Williams; Alan Griffiths; Eduard Stelcer; Leisa Dyer (135-146).
Ion Beam Analysis (IBA) techniques were used to assign nine years of PM2.5 observations to seven source types, at Lucas Heights, a topographically complex urban fringe site of Sydney. The highest contributions to total PM2.5 were from motor vehicles (Autos, 26.3%), secondary sulfur (2ndryS, 23.7%), a mixture of industry and aged sea air (IndSaged, 20.6%), and smoke (Smoke, 13.7%). The Autos contribution was highest in winter, whereas 2ndryS was highest in summer, indicating that mitigation measures targeting SO2 release in summer and vehicle exhaust in winter would be most effective in reducing the PM2.5 concentrations at this site. Since concentrations of particulate matter can be significantly affected by local meteorology, generalised additive model (GAM) techniques were employed to investigate relationships between PM2.5 source types and meteorological conditions. The GAM predictors used included: time (seasonal to inter-annual variations), mixing layer depth, temperature, relative humidity, wind speed, wind direction, and atmospheric pressure. Meteorological influences on PM2.5 variability were found to be 58% for soil dust, 46% for Autos, 41% for total PM2.5, and 35% for 2ndryS. Effects were much smaller for other source types. Temperature was found to be an important variable for the determination of total PM2.5, 2ndryS, IndSaged, Soil and Smoke, indicating that future changes in temperature are likely to have an associated change in aerosol concentrations. However, the impact on different source types varied. Temperature had the highest impact on 2ndryS (sometimes more than a factor of 4 increase for temperatures above 25 °C compared to temperatures under 10 °C) and IndSaged, being predominantly secondary aerosols formed in the atmosphere from precursors, whereas wind speed and wind direction were more important for the determination of vehicle exhaust and fresh sea salt concentrations. The marginal effect of relative humidity on 2ndryS increased up to relative humidity of 70–80% and then plateaued, confirming previous findings that (NH4)2SO4 is present in the solid phase below relative humidity of about 80%.
Keywords: Aerosols; Generalised additive models; Positive matrix factorisation; Secondary aerosols;

7Be air concentrations were measured at the Universitat Politècnica de Valencia campus (in the east of Spain) during the period 2007–2014. The mean values of monthly 7Be concentrations ranged from 2.65 to 8.11 mBq/m3, showing significant intra and interannual variability. A seasonal-trend decomposition methodology was applied to identify the trend-cycle, seasonal and irregular components of the 7Be time series. The decomposition model makes it possible to estimate the influence of solar activity and atmospheric factors on the independent components, in order to find the different sources of 7Be variability. The results show that solar activity is a factor with a high inverse influence on the trend-cycle pattern of 7Be variability. Solar radiation, temperature and relative humidity are positive influential factors on the seasonal 7Be variation with a regular pattern over the years. Finally, the irregular component presents a significant negative correlation with precipitation and wind speed parameters, which have an irregular behavior over the years and seasons.
Keywords: 7Be; Solar activity; Sunspots number; Atmospheric factors; Seasonal-trend decomposition; Time series;

Transition metals in coarse, fine, very fine and ultra-fine particles from an interstate highway transect near Detroit by Thomas A. Cahill; David E. Barnes; Jonathan A. Lawton; Roger Miller; Nicholas Spada; Robert D. Willis; Sue Kimbrough (158-175).
As one component of a study investigating the impact of vehicle emissions on near-road air quality, human exposures, and potential health effects, particles were measured from September 21 to October 30, 2010 on both sides of a major roadway (Interstate-96) in Detroit. Traffic moved freely on this 12 lane freeway with a mean velocity of 69 mi/hr. with little braking and acceleration. The UC Davis DELTA Group rotating drum (DRUM) impactors were used to collect particles in 8 size ranges at sites nominally 100 m south, 10 m north, 100 m north, and 300 m north of the highway. Ultra-fine particles were continuously collected at the 10 m north and 100 m north sites. Samples were analyzed every 3 h for mass (soft beta ray transmission), 42 elements (synchrotron-induced x-ray fluorescence) and optical attenuation (350–800 nm spectroscopy). A three day period of steady southerly winds along the array allowed direct measurement of freeway emission rates for coarse (10 > Dp > 1.0 μm), PM2.5, very fine (0.26 > Dp > 0.09 μm), and ultra-fine (Dp < 0.09 μm) particles. The PM2.5 mass concentrations were modeled using literature emission rates during the south to north wind periods, and averaged 1.6 ± 0.5 μg/m3, versus the measured value of 2.0 ± 0.7 μg/m3. Using European freeway emission rates from 2010, and modeling them at the I-96 site, we would predict roughly 3.1 μg/m3 of PM2.5 particles, corrected from the 4.9 PM10 value by their measured road dust contributions. Using California car and truck emission rates of 1973, this value would have been about 16 μg/m3, corrected down from the 19 μg/m3 PM5.0 using measured roadway dust contributions. This would have included 2.7 μg/m3 of lead, versus the 0.0033 μg/m3 measured. Very fine particles were distributed across the array with a relatively weak falloff versus distance. For the ultra-fine particles, emissions of soot and metals seen in vehicular braking studies correlated with traffic at the 10 m site, but only the soot was statistically significant at the 100 m north site. Otherwise, the 10 m north and 100 m north sites were essentially identical in mean concentration and highly correlated in time for most of the 5 week study. This result supports earlier publications showing the ability of very fine and ultra-fine particles to transport to sites well removed from the freeway sources. The concentrations of very fine and ultra-fine metals from brake wear and zinc in motor oil observed in Detroit have the potential of being a significant component in statistically established PM2.5 mortality rates.
Keywords: Aerosols; Highway; Size profiles; Lateral transects; Ultra fine metals;

Urban – Wetland contrast in turbulent exchange of methane by Włodzimierz Pawlak; Krzysztof Fortuniak; Mariusz Siedlecki; Mariusz Zieliński (176-191).
Continuous eddy-covariance measurements of turbulent methane exchange between the ground and the atmosphere were carried out during the period from July 2013 to September 2015. The measurement sites were located in areas characterized by different types of use: the city (Łódź, central Poland) and the wetlands of Biebrza National Park (northeastern Poland). Regardless of the type of surface, such long-term, continuous measurements of the turbulent fluxes of methane are rare. Our aim was to investigate the temporal variability of the turbulent methane exchange in the surface–atmosphere system, while considering the impact of land use. Because cities are a huge source of atmospheric carbon dioxide, we compared the intensity of methane emissions from the city as compared to the wetland, which is considered to be the most intense natural source atmospheric methane. In both cases, the results show a clear prevalence of positive as compared with negative fluxes. This shows that both areas are net sources of methane to the troposphere. The measurements also demonstrated the existence of a clear annual cycle of turbulent methane flux in the centre of the city (average values in winter ranged from ∼40 to 60 nmol m−2·s−1 and were significantly greater than values measured in summer) as well as in the wetlands, where maximum values were observed during the warm part of the year (approximately 80 nmol m−2·s−1 or more). The different times of maximum CH4 flux (FCH4) occurrence resulted from the differentiation of processes that determine methane emissions: in the city these are anthropogenic emissions (strongest in winter); in the wetland, natural processes dominate. The diurnal variability of FCH4 was faintly detectable, except for the cold half of the year in the city and the warm half of the year in the wetland. The studied area of the centre of Łódź, in turn, is also characterized by a weekly cycle of methane exchange: the values measured on working days were higher by 6.6% (winter) to 5.6% (summer) than those observed on weekends. Differences in the annual exchange of methane in 2014 were insignificant: the centre of Łódź emitted 17.4 g m−2 net, while the wetland emitted about 18.7 g m−2 net. The results of the measurements performed during the period from January to September 2015, however, suggest that a very dry summer, drying of the soil and, consequently, a reduced water level in the fen significantly reduced the ability of the wetland to emit methane. This pattern was not observed in the city.Display Omitted
Keywords: Methane; Urban area; Wetland; Eddy covariance; Carbon cycle;

According to the meteorological long-term variability pattern, year 2015 was influenced by El Niño and PDO (Pacific Decadal Oscillation; causes weakening of Indian Summer Monsoon). These conditions facilitate the assessment of chemical characteristics of fine-mode ambient aerosols (PM2.5; n = 48) and individual rain waters (pH: 6.4–7.6; n = 15) during the South-west monsoon (July–September 2015) in the central Indo-Gangetic Plain (IGP; Kanpur). Water-soluble ionic species (WSIS) have been measured to assess the undergoing processes (neutralization, formation and below-cloud scavenging) and estimate their dry and wet deposition fluxes. The ∑WSIS varies from 4 to 32 μg/m3 in PM2.5, whereas it ranges from 32 to 102 mg/L in rain waters. The NH4 + and SO4 2− are found to be predominant in PM2.5 (16–120 μg/m3), whereas HCO3 and Ca2+ are predominant in rain water samples. The difference in chemical composition of PM2.5 and rain water is largely attributed to additional contribution of coarse-mode mineral dust in rain water. The Ca2+ and Mg2+ in both aerosols and rain water samples are associated with HCO3 . The NO3 and SO4 2− are neutralized predominantly by NH4 + and ∑/∑+ ratio is ≈ 1 in both aerosols and rain waters. Furthermore, co-variability of NO3 with nss-Ca2+ in PM2.5 indicates role of fine-mode mineral dust surface in the formation of ammonium nitrate. Characteristic mass ratios (HCO3 /Ca2+ and SO4 2−/NH4 +) in rain water look quite similar to those in aerosols (PM2.5). This suggests that below-cloud scavenging is predominant mechanism of aerosols wash-out. Dry deposition fluxes of Mg2+, NH4 + and SO4 2− are ∼13% of their wet deposition fluxes, whereas for K+, Ca2+ and NO3 it is <6%.Display Omitted
Keywords: Indo-Gangetic Plain; Heterogeneous-phase chemistry; Rain water characteristics; Below-cloud scavenging; Dry and wet deposition fluxes;

In this paper the Bayesian methodology, known as Approximate Bayesian Computation (ABC), is applied to the problem of the atmospheric contamination source identification. The algorithm input data are on-line arriving concentrations of the released substance registered by the distributed sensors network. This paper presents the Sequential ABC algorithm in detail and tests its efficiency in estimation of probabilistic distributions of atmospheric release parameters of a mobile contamination source. The developed algorithms are tested using the data from Over-Land Atmospheric Diffusion (OLAD) field tracer experiment. The paper demonstrates estimation of seven parameters characterizing the contamination source, i.e.: contamination source starting position (x,y), the direction of the motion of the source (d), its velocity (v), release rate (q), start time of release (ts) and its duration (td). The online-arriving new concentrations dynamically update the probability distributions of search parameters. The atmospheric dispersion Second-order Closure Integrated PUFF (SCIPUFF) Model is used as the forward model to predict the concentrations at the sensors locations.
Keywords: Bayesian inference; Stochastic reconstruction; Approximate Bayesian Computation; Sequential Monte Carlo; OLAD field tracer experiment; Reconstruction of the mobile contamination source;

Near-road enhancement and solubility of fine and coarse particulate matter trace elements near a major interstate in Detroit, Michigan by Michelle M. Oakes; Janet M. Burke; Gary A. Norris; Kasey D. Kovalcik; J. Patrick Pancras; Matthew S. Landis (213-224).
Communities near major roadways are disproportionately affected by traffic-related air pollution which can contribute to adverse health outcomes. The specific role of particulate matter (PM) from traffic sources is not fully understood due to complex emissions processes and physical/chemical properties of PM in the near-road environment. To investigate the spatial profile and water solubility of elemental PM species near a major roadway, filter-based measurements of fine (PM2.5) and coarse (PM10-2.5) PM were simultaneously collected at multiple distances (10 m, 100 m, and 300 m) from Interstate I-96 in Detroit, Michigan during September–November 2010. Filters were extracted in water, followed by a hot acid extraction, and analyzed by magnetic sector field high resolution inductively coupled plasma mass spectrometry (HR-ICPMS) to quantify water-soluble and acid-soluble trace elements for each PM size fraction. PM2.5 and PM10-2.5 species measured in the near-road samples included elements associated with traffic activity, local industrial sources, and regional pollution. Metals indicative of brake wear (Ba, Cu) were dramatically enriched near the roadway during downwind conditions (factor of 5 concentration increase), with the largest increase within 100 m of the roadway. Moderate near-roadway increases were observed for crustal elements and other traffic-related PM (Fe, Ca), and the lowest increases observed for regional PM species (S). Water solubility varied by PM species and size, and for PM2.5 included highly (S, K, Ca, Mg, Zn, Ba), moderately (Cu, Mn, Sb, Pb), and minimally (Fe, Ti) water-soluble species, with lower water solubility for most species in PM10-2.5. Results from this study indicate that water-soluble PM2.5 and PM10-2.5 metals, particularly from brake/tire wear, were enhanced in the near-roadway environment which may have human health implications.Display Omitted
Keywords: Air pollution; PM; Trace metals; Traffic sources; Brake wear;

The prediction of the dispersion of air pollutants in urban areas is of great importance to public health, homeland security, and environmental protection. Computational Fluid Dynamics (CFD) emerges as an effective tool for pollutant dispersion modelling. This paper reports and quantitatively validates the shear stress transport (SST) k-ω turbulence closure model and its transitional variant for pollutant dispersion under complex urban environment for the first time. Sensitivity analysis is performed to establish recommendation for the proper use of turbulence models in urban settings. The current SST k-ω simulation is validated rigorously by extensive experimental data using hit rate for velocity components, and the “factor of two” of observations (FAC2) and fractional bias (FB) for concentration field. The simulation results show that current SST k-ω model can predict flow field nicely with an overall hit rate of 0.870, and concentration dispersion with FAC2 = 0.721 and FB = 0.045. The flow simulation of the current SST k-ω model is slightly inferior to that of a detached eddy simulation (DES), but better than that of standard k-ε model. However, the current study is the best among these three model approaches, when validated against measurements of pollutant dispersion in the atmosphere. This work aims to provide recommendation for proper use of CFD to predict pollutant dispersion in urban environment.
Keywords: Pollutant dispersion; CFD; RANS; SST k-ω turbulence model; Urban environment;

Net global warming potential and greenhouse gas intensity of conventional and conservation agriculture system in rainfed semi arid tropics of India by G. Pratibha; I. Srinivas; K.V. Rao; Arun K. Shanker; B.M.K. Raju; Deepak K. Choudhary; K. Srinivas Rao; Ch. Srinivasarao; M. Maheswari (239-250).
Agriculture has been considered as one of the contributors to greenhouse gas (GHG) emissions and it continues to increase with increase in crop production. Hence development of sustainable agro techniques with maximum crop production, and low global warming potential is need of the hour. Quantifying net global warming potential (NGWP) and greenhouse gas intensity (GHGI) of an agricultural activity is a method to assess the mitigation potential of the activity. But there is dearth of information on NGWP of conservation agriculture under rainfed conditions. Hence in this study two methods such as crop based (NGWPcrop) and soil based (NGWPsoil) were estimated from the data of the experiment initiated in 2009 in rainfed semiarid regions of Hyderabad, India with different tillage practices like conventional tillage (CT), reduced tillage (RT), zero tillage (ZT) and residue retention levels by harvesting at different heights which includes 0, 10 and 30 cm anchored residue in pigeonpea-castor systems. The results of the study revealed that under rainfed conditions CT recorded 24% higher yields over ZT, but CT and RT were on par with each other. However, the yield gap between the tillage treatments is narrowing down over 5 years of study. ZT and RT recorded 26 and 11% lower indirect GHG emissions (emissions from farm operations and input use) over CT, respectively. The percent contribution of CO2 eq. N2O emission is higher to total GHG emissions in both the crops. Both NGWPcrop, NGWPsoil, GHGIcrop, and GHGIsoil based were influenced by tillage and residue treatments. Further, castor grown on pigeonpea residue recorded 20% higher GHG emissions over pigeonpea grown on castor residues. The fuel consumption in ZT was reduced by 58% and 81% as compared to CT in pigeonpea and castor, respectively. Lower NGWP and GHGI based on crop and soil was observed with increase in crop residues and decrease in tillage intensity in both the crops. The results of the study indicate that, there is scope to reduce the NGWP emissions by reducing one tillage operation as in RT and increase in crop residue by harvesting at 10 and 30 cm height with minimal impact on the crop yields. However, the trade-off between higher yield and soil health versus GHG emissions should be considered while promoting conservation agriculture. The NGWPcrop estimation method indicated considerable benefits of residues to the soil and higher potential of GHG mitigation than by the NGWPsoil method and may overestimate the potential of GHG mitigation in agriculture system.
Keywords: Greenhouse gas emissions; Net global warming potential; Tillage; Greenhouse gas intensity; Anchored residue;

The Lagrangian atmospheric dispersion model NAME (Numerical Atmospheric-dispersion Modelling Environment), has been used to simulate the formation and transport of PM10 over North-West Europe in 2008. The model has been evaluated against UK measurement data and been shown to adequately represent the observed PM10 at rural and urban sites on a daily basis. The Lagrangian nature of the model allows information on the origin of pollutants (and hence their secondary products) to be retained to allow attribution of pollutants at receptor sites back to their sources. This source apportionment technique has been employed to determine whether the different components of the modelled PM10 have originated from UK, shipping, European (excluding the UK) or background sources. For the first time this has been done to evaluate the composition during periods of elevated PM10 as well as the annual average composition. The episode data were determined by selecting the model data for each hour when the corresponding measurement data was >50 μg/m3. All the modelled sites show an increase in European pollution contribution and a decrease in the background contribution in the episode case compared to the annual average. The European contribution is greatest in southern and eastern parts of the UK and decreases moving northwards and westwards. Analysis of the speciated attribution data over the selected sites reveals that for 2008, as an annual average, the top three contributors to total PM10 are UK primary PM10 (17–25%), UK origin nitrate aerosol (18–21%) and background PM10 (11–16%). Under episode conditions the top three contributors to modelled PM10 are UK origin nitrate aerosol (12–33%), European origin nitrate aerosol (11–19%) and UK primary PM10 (12–18%).
Keywords: Speciated PM10; Source apportionment; Episode; Air quality;

Assessment of the Olea pollen and its major allergen Ole e 1 concentrations in the bioearosol of two biogeographical areas by S. Moreno-Grau; M.J. Aira; B. Elvira-Rendueles; M. Fernández-González; D. Fernández-González; A. García-Sánchez; M.J. Martínez-García; J.M. Moreno; L. Negral; A. Vara; F.J. Rodríguez-Rajo (264-271).
The Olea pollen is currently an important allergy source. In some regions of Southern Spain, olive pollen is the main cause of allergic sensitization exceeding 40% of the sensitized individuals. Due to the scarce presence of olive trees in Northern Spain, limited to some cultivated fields in the South of the Galicia region where they also grow wild, only 8% of the sensitized individuals showed positive results for Olea pollen. The aim of the paper was to assess the behaviour pattern of the Olea pollen and its aeroallergens in the atmosphere, as this information could help us to improve the understanding and prevention of clinical symptoms.Airborne Olea pollen and Ole e 1 allergens were quantified in Cartagena (South-eastern Spain) and Ourense (North-western Spain). A volumetric pollen trap and a Burkard Cyclone sampler were used for pollen and allergen quantification.The Olea flowering took place in April or May in both biometeorological sampling areas. The higher concentrations were registered in the Southern area of Spain, for both pollen and Ole e 1, with values 8 times higher for pollen concentrations and 40 times higher for allergens. An alternate bearing pattern could be observed, characterized by years with high pollen values and low allergen concentrations and vice versa. Moreover, during some flowering seasons the allergen concentrations did not correspond to the atmospheric pollen values. Variations in weather conditions or Long Distance Transport (LDT) processes could explain the discordance. The back trajectory analysis shows that the most important contributions of pollen and allergens in the atmosphere are coincident with air masses passing through potential source areas. The exposure to olive pollen may not be synonym of antigen exposure.
Keywords: Olea; Pollen; LDT; Aerobiology; Allergens; Ole e 1;

Physicochemical characterization of winter PM10 aerosol impacted by sugarcane burning from São Paulo city, Brazil by Sofia E.S. Caumo; Magda Claeys; Willy Maenhaut; Reinhilde Vermeylen; Shabnam Behrouzi; Mohammad Safi Shalamzari; Pérola C. Vasconcellos (272-279).
Atmospheric particulate matter samples (PM10) were collected at an urban site in São Paulo (SPA) city in winter episodes of 2012 and 2013. Several organic compounds were determined in the samples to characterize the composition of the particulate matter with emphasis on marker compounds for biomass burning. Organic carbon (OC), elemental carbon (EC), monosaccharide anhydrides, monosaccharides, nitroaromatic compounds, isoprene secondary organic aerosol markers, and polyols were measured. The PM10, OC and EC median concentrations were higher for samples collected in 2013 than in 2012, with the contribution of OC to the PM10 mass being 17% and 11% in 2012 and 2013. The three anhydrosugars, levoglucosan, mannosan and galactosan together, accounted, on average, for 2.0 and 2.2% of the OC mass in 2012 and 2013, whereas the nitro-aromatic compounds, including 4-nitrophenol, 4-nitrocatechol, isomeric methyl nitrocatechols and dimethyl catechols, showed the same trend, contributing, on average, for 0.28% and 0.35% to the OC mass in 2012 and 2013, and thus indicating a higher contribution from biomass burning in 2013 compared to 2012. The methyl nitrocatechols were substantially correlated with levoglucosan, consistent with their proposed origin from biomass burning. The results demonstrate that biomass burning compounds are important contributors to the OC mass, especially in winter. Furthermore, it is suggested that a levoglucosan/galactosan ratio smaller than about 30 may be indicative for regional sugarcane burning and not for advected air from sites that are impacted by tropical forest fires.
Keywords: Biomass burning markers; Atmospheric chemistry; Nitrocathecols; Atmospheric particulate matter;

Facing the challenge of meeting emissions reduction targets of China, this paper employed the logarithmic mean Divisia index (LMDI) method to study the changes of energy-related carbon emissions in high energy-consumption sectors (HES), mid energy-consumption sectors (MES) and low energy-consumption sectors (LES) from 1996 to 2012. The decomposition results revealed that the economic growth was the most significant factor to increase carbon emissions of three subgroups while the decrease in energy intensity was the dominant factor to reduce carbon emissions of MES and LES. Considering the important roles economic growth and energy intensity played in carbon emissions, three scenarios were set based on the different growth rates of these two factors to identify whether the emissions reduction targets of 40–45% in 2020 and 60–65% in 2030 can be achieved using the co-integration technique. It was indicated that the emissions targets both in 2020 and 2030 can be achieved by LES in the base scenario. In stark contrast to LES, the carbon intensity of HES reduced only 10.03% in 2020 and 14% in 2030 compared to the 2005 level. Therefore, more attentions should be focused on the economic activity and energy intensity of HES. Finally, according to the results obtained, policy implications were provided to further mitigate the carbon intensity of China's industrial sector.
Keywords: Carbon emissions; Decomposition analysis; Different energy-consumption sectors; Co-integration relationships; Scenario analysis;

Current science and policy requirements have focused attention on the need to expand and improve particulate matter (PM) sampling methods. To explore how sampling filter type affects artifacts in PM composition measurements, size-resolved particulate SO4 2−, NO3 and NH4 + (SNA) were measured on quartz fiber filters (QFF), glass fiber filters (GFF) and cellulose membranes (CM) concurrently in an urban area of Beijing on both clean and hazy days. The results showed that SNA concentrations in most of the size fractions exhibited the following patterns on different filters: CM > QFF > GFF for NH4 +; GFF > QFF > CM for SO4 2−; and GFF > CM > QFF for NO3 . The different patterns in coarse particles were mainly affected by filter acidity, and that in fine particles were mainly affected by hygroscopicity of the filters (especially in size fraction of 0.65–2.1 μm). Filter acidity and hygroscopicity also shifted the peaks of the annual mean size distributions of SNA on QFF from 0.43–0.65 μm on clean days to 0.65–1.1 μm on hazy days. However, this size shift was not as distinct for samples measured with CM and GFF. In addition, relative humidity (RH) and pollution levels are important factors that can enhance particulate size mode shifts of SNA on clean and hazy days. Consequently, the annual mean size distributions of SNA had maxima at 0.65–1.1 μm for QFF samples and 0.43–0.65 μm for GFF and CM samples. Compared with NH4 + and SO4 2−, NO3 is more sensitive to RH and pollution levels, accordingly, the annual mean size distribution of NO3 exhibited peak at 0.65–1.1 μm for CM samples instead of 0.43–0.65 μm. These methodological uncertainties should be considered when quantifying the concentrations and size distributions of SNA under different RH and haze conditions.
Keywords: SNA; Size distribution; Haze; Glass fiber filters; Quartz fiber filters; Cellulose membranes;

Characterization of volatile organic compounds from different cooking emissions by Shuiyuan Cheng; Gang Wang; Jianlei Lang; Wei Wen; Xiaoqi Wang; Sen Yao (299-307).
Cooking fume is regarded as one of the main sources of urban atmospheric volatile organic compounds (VOCs) and its chemical characteristics would be different among various cooking styles. In this study, VOCs emitted from four different Chinese cooking styles were collected. VOCs concentrations and emission characteristics were analyzed. The results demonstrated that Barbecue gave the highest VOCs concentrations (3494 ± 1042 μg/m3), followed by Hunan cuisine (494.3 ± 288.8 μg/m3), Home cooking (487.2 ± 139.5 μg/m3), and Shandong cuisine (257.5 ± 98.0 μg/m3). The volume of air drawn through the collection hood over the stove would have a large impact on VOCs concentration in the exhaust. Therefore, VOCs emission rates (ER) and emission factors (EF) were also estimated. Home cooking had the highest ER levels (12.2 kg/a) and Barbecue had the highest EF levels (0.041 g/kg). The abundance of alkanes was higher in Home cooking, Shandong cuisine and Hunan cuisine with the value of 59.4%–63.8%, while Barbecue was mainly composed of alkanes (34.7%) and alkenes (39.9%). The sensitivity species of Home cooking and Hunan cuisine were alkanes, and that of Shandong cuisine and Barbecue were alkenes. The degree of stench pollution from cooking fume was lighter.
Keywords: Cooking styles; Volatile organic compounds; Chemical profiles; Ozone formation potential;

Blending forest fire smoke forecasts with observed data can improve their utility for public health applications by Weiran Yuchi; Jiayun Yao; Kathleen E. McLean; Roland Stull; Radenko Pavlovic; Didier Davignon; Michael D. Moran; Sarah B. Henderson (308-317).
Fine particulate matter (PM2.5) generated by forest fires has been associated with a wide range of adverse health outcomes, including exacerbation of respiratory diseases and increased risk of mortality. Due to the unpredictable nature of forest fires, it is challenging for public health authorities to reliably evaluate the magnitude and duration of potential exposures before they occur. Smoke forecasting tools are a promising development from the public health perspective, but their widespread adoption is limited by their inherent uncertainties. Observed measurements from air quality monitoring networks and remote sensing platforms are more reliable, but they are inherently retrospective. It would be ideal to reduce the uncertainty in smoke forecasts by integrating any available observations. This study takes spatially resolved PM2.5 estimates from an empirical model that integrates air quality measurements with satellite data, and averages them with PM2.5 predictions from two smoke forecasting systems. Two different indicators of population respiratory health are then used to evaluate whether the blending improved the utility of the smoke forecasts. Among a total of six models, including two single forecasts and four blended forecasts, the blended estimates always performed better than the forecast values alone. Integrating measured observations into smoke forecasts could improve public health preparedness for smoke events, which are becoming more frequent and intense as the climate changes.
Keywords: Forest fire smoke; Blended models; Fine particulate matter; Exposure assessment; Epidemiology; Public health;

Atmospheric molecular hydrogen (H2) at the Shangdianzi regional background station in China by Tian Luan; Shuangxi Fang; Bo Yao; Hongyang Wang; Fan Dong; Qingfeng Shi; Liyan Zhou; Huaigang Zhou (318-325).
Atmospheric molecular hydrogen (H2) mole fractions have been continuously measured at the Shangdianzi regional station in China. In this study, we present the atmospheric H2 time series from January 2015 to April 2016, and investigate the diurnal and seasonal cycles, and the impact of meteorological factors on the observed values. Atmospheric H2 mole fractions at Shangdianzi vary from a minimum of 381 ppb (parts per billion, 10−9 dry air mole fraction) to a maximum of 1535 ppb, with a median of 510 ppb and a mean (± standard deviation) of 555 ± 113 ppb during the observation period. The results indicate that H2 mole fractions at Shangdianzi are frequently influenced by local sources and sinks. Regionally representative conditions account for 44.7% of the total records with a mean mole fraction of 488 ± 20 ppb. The highest regionally representative H2 mole fraction is observed in July, while the lowest is observed in October. Peak-to-trough amplitude in the seasonal cycle is 63 ± 3 ppb. H2 mole fractions show nighttime depletion in all seasons, with the lowest values in the morning (7:00–10:00 local time). The H2 mole fractions are also influenced by local surface wind direction at Shangdianzi. Winds from NW-NNW-N-NNE-NE-ENE-E directions are always associated with negative contribution to atmospheric H2 loading, whereas winds from SSW-SW-WSW-W directions generally enhance the H2 values. The results of trajectory clustering analysis demonstrate that air masses from a southerly direction induce high H2 mole fractions. Conversely, mean H2 mole fractions are low when air masses are from the north, northwest, and east directions.
Keywords: Atmospheric H2; Diurnal cycle; Seasonal cycle; Wind direction; Cluster analysis;

Ozone formation in California in year 2017 was simulated using three chemical mechanisms: the Statewide Air Pollution Research Center 2007 mechanism with updated toxics and isoprene chemistry (S07TIC); the Carbon Bond 6, revision 2 (CB6r2) mechanism; a modified CB6r2 mechanism with increased hydroxyl radical (OH) production from isoprene oxidation at low nitrogen oxide (NOx) concentrations (CB6r2OH). The simulations with a photochemical grid model (PGM) showed little difference in ozone between CB6r2 and CB6r2OH. Further analysis with a box model found little sensitivity of ozone to OH production in the isoprene chemistry of all three mechanisms under conditions representative of California. The S07TIC generally predicts greater ozone than the CB6r2, and the difference in the predicted concentrations exceeds the uncertainty estimated from uncertainties in the emissions inventory. The sensitivity of ozone to anthropogenic volatile organic compound (VOC), NOx and carbon monoxide (CO) emissions and to isoprene emissions was also calculated with the PGM. Accounting for uncertainties in the emissions inventory, the sensitivity to NOx emissions is significantly different between S07TIC and CB6r2 in central and northern California; the sensitivity to isoprene emissions is significantly different in southern California. All mechanisms give a negative sensitivity of ozone to isoprene emissions in areas of northern California where NOx emissions are small. The CB6r2 and S07TIC differ in the sensitivity of ozone to organic nitrate (ON) formation from isoprene oxidation, likely because all ONs recycle to NOx in the S07TIC mechanism but only first-generation ONs do so in the CB6r2. For current California conditions, uncertainties in OH production from isoprene have little impact on ozone, but the extent to which isoprene ONs recycle NOx does impact ozone concentration and ozone sensitivity to NOx emissions.Display Omitted
Keywords: Isoprene chemistry; Ozone; Central California; Sensitivity analysis; Emissions; Organic nitrates;

Impact of the 0.1% fuel sulfur content limit in SECA on particle and gaseous emissions from marine vessels by Maria Zetterdahl; Jana Moldanová; Xiangyu Pei; Ravi Kant Pathak; Benjamin Demirdjian (338-345).
Emissions were measured on-board a ship in the Baltic Sea, which is a sulfur emission control area (SECA), before and after the implementation of the strict fuel sulfur content (FSC) limit of 0.1 m/m% S on the 1st of January 2015. Prior to January 2015, the ship used a heavy fuel oil (HFO) but switched to a low-sulfur residual marine fuel oil (RMB30) after the implementation of the new FSC limit. The emitted particulate matter (PM) was measured in terms of mass, number, size distribution, volatility, elemental composition, content of organics, black and elemental carbon, polycyclic aromatic hydrocarbons (PAHs), microstructure and micro-composition, along with the gaseous emissions at different operating conditions. The fuel change reduced emissions of PM mass up to 67%. The number of particles emitted remained unchanged and were dominated by nanoparticles. Furthermore, the fuel change resulted in an 80% reduction of SO2 emissions and decreased emissions of total volatile organic compounds (VOCs). The emissions of both monoaromatic and lighter polyaromatic hydrocarbon compounds increased with RMB30, while the heavy, PM-bound PAH species that belong to the carcinogenic PAH family were reduced. Emissions of BC remained similar between the two fuels. This study indicates that the use of low-sulfur residual marine fuel oil is a way to comply with the new FSC regulation and will reduce the anthropogenic load of SO2 emissions and secondary PM formed from SO2. Emissions of primary particles, however, remain unchanged and do not decrease as much as would be expected if distilled fuel was used. This applies both to the number of particles emitted and some toxic components, such as heavy metals, PAHs or elemental carbon (EC). The micro-composition analyses showed that the soot particles emitted from RMB30 combustion often do not have any trace of sulfur compared with particles from HFO combustion, which always have a sulfur content over 1%m/m. The soot sulfur content can impact aging and cloud condensation properties. This study is an in-depth comparison of the impact of these two fuels on the emissions of particles as well as their composition and microstructure. To evaluate the impact of the use of low-sulfur residual marine fuel oils on emissions from ships, additional research is needed to investigate the varied fuel types and compositions as well as the wide range of engine conditions and properties.Display Omitted
Keywords: Particle emission; SECA; Marine fuel; Gas emission; Emission factor;

A European aerosol phenomenology-5: Climatology of black carbon optical properties at 9 regional background sites across Europe by M. Zanatta; M. Gysel; N. Bukowiecki; T. Müller; E. Weingartner; H. Areskoug; M. Fiebig; K.E. Yttri; N. Mihalopoulos; G. Kouvarakis; D. Beddows; R.M. Harrison; F. Cavalli; J.P. Putaud; G. Spindler; A. Wiedensohler; A. Alastuey; M. Pandolfi; K. Sellegri; E. Swietlicki; J.L. Jaffrezo; U. Baltensperger; P. Laj (346-364).
A reliable assessment of the optical properties of atmospheric black carbon is of crucial importance for an accurate estimation of radiative forcing. In this study we investigated the spatio-temporal variability of the mass absorption cross-section (MAC) of atmospheric black carbon, defined as light absorption coefficient (σ ap ) divided by elemental carbon mass concentration (m EC). σ ap and m EC have been monitored at supersites of the ACTRIS network for a minimum period of one year. The 9 rural background sites considered in this study cover southern Scandinavia, central Europe and the Mediterranean. σ ap was determined using filter based absorption photometers and m EC using a thermal-optical technique. Homogeneity of the data-set was ensured by harmonization of all involved methods and instruments during extensive intercomparison exercises at the European Center for Aerosol Calibration (ECAC). Annual mean values of σ ap at a wavelength of 637 nm vary between 0.66 and 1.3 Mm−1 in southern Scandinavia, 3.7–11 Mm−1 in Central Europe and the British Isles, and 2.3–2.8 Mm−1 in the Mediterranean. Annual mean values of m EC vary between 0.084 and 0.23 μg m−3 in southern Scandinavia, 0.28–1.1 in Central Europe and the British Isles, and 0.22–0.26 in the Mediterranean. Both σ ap and m EC in southern Scandinavia and Central Europe have a distinct seasonality with maxima during the cold season and minima during summer, whereas at the Mediterranean sites an opposite trend was observed. Annual mean MAC values were quite similar across all sites and the seasonal variability was small at most sites. Consequently, a MAC value of 10.0 m2 g−1 (geometric standard deviation = 1.33) at a wavelength of 637 nm can be considered to be representative of the mixed boundary layer at European background sites, where BC is expected to be internally mixed to a large extent. The observed spatial variability is rather small compared to the variability of values in previous literature, indicating that the harmonization efforts resulted in substantially increased precision of the reported MAC. However, absolute uncertainties of the reported MAC values remain as high as ± 30–70% due to the lack of appropriate reference methods and calibration materials.The mass ratio between elemental carbon and non-light-absorbing matter was used as a proxy for the thickness of coatings around the BC cores, in order to assess the influence of the mixing state on the MAC of BC. Indeed, the MAC was found to increase with increasing values of the coating thickness proxy. This provides evidence that coatings do increase the MAC of atmospheric BC to some extent, which is commonly referred to as lensing effect.Display Omitted
Keywords: Black carbon; Europe; Mass absorption cross-section; MAC; Light absorption; Elemental carbon; Radiative forcing; Photometer; Thermal optical analysis; Atmosphere; ACTRIS; Ebas;

Prediction of ground-level ozone concentration in São Paulo, Brazil: Deterministic versus statistic models by G. Hoshyaripour; G. Brasseur; M.F. Andrade; M. Gavidia-Calderón; I. Bouarar; R.Y. Ynoue (365-375).
Two state-of-the-art models (deterministic: Weather Research and Forecast model with Chemistry (WRF-Chem) and statistic: Artificial Neural Networks: (ANN)) are implemented to predict the ground-level ozone concentration in São Paulo (SP), Brazil. Two domains are set up for WRF-Chem simulations: a coarse domain (with 50 km horizontal resolution) including whole South America (D1) and a nested domain (with horizontal resolution of 10 km) including South Eastern Brazil (D2). To evaluate the spatial distribution of the chemical species, model results are compared to the Measurements of Pollution in The Troposphere (MOPITT) data, showing that the model satisfactorily predicts the CO concentrations in both D1 and D2. The model also reproduces the measurements made at three air quality monitoring stations in SP with the correlation coefficients of 0.74, 0.70, and 0.77 for O3 and 0.51, 0.48, and 0.57 for NOx. The input selection for ANN model is carried out using Forward Selection (FS) method. FS-ANN is then trained and validated using the data from two air quality monitoring stations, showing correlation coefficients of 0.84 and 0.75 for daily mean and 0.64 and 0.67 for daily peak ozone during the test stage. Then, both WRF-Chem and FS-ANN are deployed to forecast the daily mean and peak concentrations of ozone in two stations during 5–20 August 2012. Results show that WRF-Chem preforms better in predicting mean and peak ozone concentrations as well as in conducting mechanistic and sensitivity analysis. FS-ANN is only advantageous in predicting mean daily ozone concentrations considering its significantly lower computational costs and ease of development and implementation, compared to that of WRF-Chem.
Keywords: Air quality modeling; WRF-Chem; Neural networks; Southeastern Brazil; Tropospheric ozone; São Paulo;

Quantifying stability influences on air pollution in Lanzhou, China, using a radon-based “stability monitor”: Seasonality and extreme events by Fenjuan Wang; Scott D. Chambers; Zhenyi Zhang; Alastair G. Williams; Xiaodong Deng; Hua Zhang; Giovanni Lonati; Jagoda Crawford; Alan D. Griffiths; Antonietta Ianniello; Ivo Allegrini (376-391).
A recently-developed radon-based technique is modified to quantify the seasonal influences of atmospheric stability on urban emissions in Lanzhou, China, based on 11 months of observations at three sites with contrasting pollution characteristics. Near-surface concentrations of primary (CO, SO2, NOx) and secondary (O3) gas phase pollutants responded to changing atmospheric stability in markedly different ways in winter and summer, primarily because monsoonal fetch changes strongly influenced the distance between measurement sites and their nearest upwind pollutant sources, but also due to mean diurnal changes in mixing depth. Typically, morning peak primary pollution concentrations increased by a factor of 2–5 from the most well-mixed to stable conditions, whereas nocturnal ozone concentrations reduced with increasing stability due to surface loss processes and the progressively reduced coupling between the nocturnal boundary layer and overlying free atmosphere. The majority of pollution exceedance events (cf. China National Air Quality Standard guideline values) occurred in winter, when all measurement stations were downwind of the city's main pollution sources, and were directly attributed to morning periods and stable atmospheric conditions. In the sheltered valley region of Lanzhou, extremes of winter nocturnal stability states represented a change in mean nocturnal wind speed of only 0.25 m s−1 (from 0.6 to 0.85 m s−1). Daily-integrated PM10 concentrations increased by a factor of 2 in winter from the most well-mixed to stable conditions, and were usually above guideline values at the industrial and residential sites for all atmospheric stability conditions. In summer, however, daily mean PM10 exceedances usually only occurred at the industrial site, under stable conditions. Finally, a simple model – based on mean radon concentrations between 1900 and 0400 h – is proposed to predict haze conditions in the city prior to commencement of the peak morning commuting time.
Keywords: Atmospheric stability; Air pollution; Radon; Extreme events; Haze prediction;

This study evaluates the performance of the German dispersion model Austal2000 according to the technical instructions on air quality control (TA Luft), a Lagrangian model, in four real-world particulate matter test cases against ENVI-met, a microclimate model featuring a pollutant dispersion module that bases on the Eularian approach. The four test cases include different traffic induced area sources of PM10, complex terrain with varying ground surfaces and different urban obstacles i.e. buildings. A comparison is made between the calculated concentrations of both models. Furthermore, predictions are compared with field data. Particle measurements are conducted with an optical particle counter. For evaluation, quantile-quantile plots as well as further performance measures i.e. the fractional bias and the robust highest concentration that focuses on the important high-end concentrations are applied. Both models underpredicted observed PM(0.25;10) concentrations for all test cases. All datasets show that predictions of both simulation tools were closer to field observations in the high-end concentration range. Model calculation results show mostly better agreement to observations under neutral stability classes of the atmosphere. With the exception of ENVI-met in one test case predictions of simulation runs of both models lead to results closer to observations when initiated with local meteorological measurement data, where wind speed as one of the key drivers of dispersion models was lower. In almost all of the test cases, Austal2000's predictions were closer to the field observations than those of ENVI-met. The latter model undercut predicted PM10 concentrations of Austal2000 by the factor of around two. This evaluation indicates that Austal2000 is the stronger model compared with ENVI-met considering the distribution of PM10 in complex and urban terrain.
Keywords: ENVI-Met; Austal2000; Micro-scale simulations; Particle dispersion; Model performance; Particulate matter;

Seasonal variations of fine particulate organosulfates derived from biogenic and anthropogenic hydrocarbons in the mid-Atlantic United States by L. Edward Meade; Matthieu Riva; Max Z. Blomberg; Amanda K. Brock; Elisa Marie Qualters; Richard A. Siejack; Kumar Ramakrishnan; Jason D. Surratt; Kathryn E. Kautzman (405-414).
Organosulfates (OSs) are an important and ubiquitous class of organic compounds found in ambient fine particulate matter (PM2.5) that serves as markers for multiphase chemical processes leading to secondary organic aerosol (SOA) formation. In this study, high-volume filter sampling was implemented to collect PM2.5 samples during the August 2012–June 2013 time period in suburban Towson, MD. By utilizing ultra-performance liquid chromatography coupled with high-resolution quadrupole time-of-flight mass spectrometry employing an electrospray ionization source (UPLC/ESI-HR-QTOFMS), 58 OSs were characterized and quantified in PM2.5 collected across all seasons. The selection of the extraction solvent was also found to be important for OS characterization. Seasonal trends demonstrate that the atmospheric oxidation of biogenic volatile organic compounds (VOCs) dominates OS formation in early fall and spring, with substantial contributions from isoprene OS (∼15 ng/m3), and limonene and α-pinene OS (∼5 ng/m3). From November to March anthropogenic OSs, including polycyclic aromatic hydrocarbon (PAH)- and alkane-derived OSs recently characterized in laboratory-generated SOA, reached their highest levels averaging 4 ng/m3. Nitrogen-containing OSs derived from terpene chemistry remain consistent over the sampling period averaging 2 ng/m3 and do not demonstrate strong seasonal fluctuations. Correlations between the identified OSs and known organic acids that arise from either the atmospheric oxidation of biogenic or anthropogenic VOCs assist in source apportionment. Meteorological data coupled with air mass back-trajectory analyses using HYSPLIT provide insight into meteorological and transport conditions that promote the formation/occurrence of OSs within the mid-Atlantic U.S. region.
Keywords: Multiphase chemistry; Secondary organic aerosol; HYSPLIT; Acid-catalyzed chemistry; Filter sampling;

Airborne observations of mercury emissions from the Chicago/Gary urban/industrial area during the 2013 NOMADSS campaign by L.E. Gratz; J.L. Ambrose; D.A. Jaffe; C. Knote; L. Jaeglé; N.E. Selin; T. Campos; F.M. Flocke; M. Reeves; D. Stechman; M. Stell; A.J. Weinheimer; D.J. Knapp; D.D. Montzka; G.S. Tyndall; R.L. Mauldin; C.A. Cantrell; E.C. Apel; R.S. Hornbrook; N.J. Blake (415-423).
Atmospheric emissions from the Chicago/Gary urban/industrial area significantly enhance ambient mercury (Hg) concentrations and lead to increased levels of atmospheric Hg deposition within the Lake Michigan Basin. We use airborne observations collected over Lake Michigan during the 2013 Nitrogen, Oxidants, Mercury, and Aerosol Distributions, Sources, and Sinks (NOMADSS) campaign to quantify the outflow of total Hg (THg) emissions from the Chicago/Gary urban/industrial area. We use concurrent airborne measurements of THg, carbon monoxide (CO), nitrogen oxides (NOx = NO + NO2), and sulfur dioxide (SO2) to calculate measured enhancement ratios and to characterize Chicago/Gary emissions with respect to the 2011 U.S. EPA National Emissions Inventory. We determine the observed THg/CO enhancement ratio in outflow from Chicago/Gary to be 0.21 ± 0.09 × 10−6 mol mol−1 (ppqv/ppbv), which is comparable to observations reported for other major U.S. urban/industrial areas. We also employ the FLEXPART Lagrangian transport and dispersion model to simulate air mass transport during plume encounters and to compare our observations to inventoried emission ratios. We find that our observed THg/CO enhancement ratios are 63–67% greater than the transport-corrected emission ratios for the Chicago/Gary area. Our results suggest that there are many small emission sources that are not fully accounted for within the inventory, and/or that the re-emission of legacy Hg is a significant source of THg to the atmosphere in this region.
Keywords: Mercury; Airborne observations; Enhancement ratio; Emission inventory; Urban area;

The role of local urban traffic and meteorological conditions in air pollution: A data-based case study in Madrid, Spain by Ibai Laña; Javier Del Ser; Ales Padró; Manuel Vélez; Carlos Casanova-Mateo (424-438).
Urban air pollution is a matter of growing concern for both public administrations and citizens. Road traffic is one of the main sources of air pollutants, though topography characteristics and meteorological conditions can make pollution levels increase or diminish dramatically. In this context an upsurge of research has been conducted towards functionally linking variables of such domains to measured pollution data, with studies dealing with up to one-hour resolution meteorological data. However, the majority of such reported contributions do not deal with traffic data or, at most, simulate traffic conditions jointly with the consideration of different topographical features. The aim of this study is to further explore this relationship by using high-resolution real traffic data. This paper describes a methodology based on the construction of regression models to predict levels of different pollutants (i.e. CO, NO, NO2, O3 and PM10) based on traffic data and meteorological conditions, from which an estimation of the predictive relevance (importance) of each utilized feature can be estimated by virtue of their particular training procedure. The study was made with one hour resolution meteorological, traffic and pollution historic data in roadside and background locations of the city of Madrid (Spain) captured over 2015. The obtained results reveal that the impact of vehicular emissions on the pollution levels is overshadowed by the effects of stable meteorological conditions of this city.Display Omitted
Keywords: Urban air pollution; Traffic flow; Meteorological conditions; Supervised learning; Random forests;

Synergic estimation of columnar integrated aerosol properties and their vertical resolved profiles in respect to the scenarios of dust intrusions over Granada by Florian Mandija; Juan Luis Guerrero-Rascado; Hassan Lyamani; María José Granados-Muñoz; Lucas Alados-Arboledas (439-454).
In this paper, we present a study of the columnar and vertically resolved aerosol optical properties over Granada (Spain) during dust events detected during July-August in the period 2012–2013. For this purpose, we classified the events according to their origins and pathways. The analyzed aerosol properties include; columnar aerosol optical properties like aerosol optical depth (AOD) and Angstrom exponent (AE), as well as the lidar products, like backscatter-related Angstrom exponent and linear particle depolarization ratio (LDPR). The lidar profiles are used for determination of the geometrical structure of dust layers and the aerosol optical parameters inside dust layers.There are identified 58 dusty days over Granada during the periods July-August, 2012–2013. In 71% of the dust, event analyzed the dust plume over Granada is located between 3000 and 4000 m a.g.l. Mean values of AOD500 according to the Atlantic and Mediterranean pathway were 0.28 ± 0.10 and 0.93 ± 0.17. Meanwhile, the mean values of AE440-870 were 0.57 ± 0.25 and 0.43 ± 0.20. Three region are identified as the main dust sources affecting the dust intrusions over Granada. Two principal pathways of air masses during dust intrusion over Granada were observed: through Atlantic (52.7%) and through Mediterranean (47.3%). Air masses which come through the Mediterranean present larger AOD and lower Angstrom exponent values than those air masses coming through Atlantic.Lidar measurements show different vertical distributions on particle backscatter coefficient, during different scenarios of dust intrusions. The lidar profiles indicate that average base and top heights of all dust during the investigation period were 2.1 ± 0.7 and 4.8 ± 0.9 km, and their center of mass and thickness were 3.3 ± 0.7 and 2.8 ± 1.0 km a.g.l. The AE355/532 profiles for the dust intrusions present some differences depending on the source regions and path followed by the dust. On the other hand, the profiles of LPDRat 532 nm were more similar for all scenarios.
Keywords: Dust intrusion scenarios; Aerosol optical properties; Sunphotometer and lidar measurements;

The gas-phase reactions of unsaturated alcohols with O3 were investigated in FEP Teflon film chamber at 298 K and 760 torr of atmosphere pressure. The rate constants of the reactions of C6-C8 alkenols with O3 were determined using both the absolute and the relative rate method, and the measured values were (5.96 ± 0.35) × 10−17 cm3 molecule−1 s−1 for (Z)-3-hexen-1-ol, (5.12 ± 0.30) × 10−17 cm3 molecule−1 s−1 for (Z)-3-hepten-1-ol, and (5.66 ± 0.52) × 10−17 cm3 molecule−1 s−1 for (Z)-3-octen-1-ol, respectively. The gas-phase products of these reactions mentioned above were detected using proton-transfer-reaction mass spectrum (PTR-MS). HOCH2CH2CHO, CH2CH2CHO, HCHO and CH3CHO were identified as the main gas products for (Z)-3-hexen-1-ol. HOCH2CH2CHO and CH3(CH2)2CHO dominated the gaseous products for (Z)-3-hepten-1-ol. And for (Z)-3-octen-1-ol, CH3(CH2)3CHO, CH3(CH2)2CHO and HOCH2CH2CHO were the main gaseous products. The SOA yields were monitored at the same time, which were 0.184 ± 0.013, 0.213 ± 0.017, 0.232 ± 0.021 for (Z)-3-hexen-1-ol, (Z)-3-hepten-1-ol and (Z)-3-octen-1-ol, respectively. The possible reaction mechanisms were proposed and discussed. The kinetic data presented here has been used to estimate their atmosphere lifetimes and the reaction reactivity. The atmosphere implication of these reactions has also been discussed.Display Omitted
Keywords: (Z)-3-hexen-1-ol; (Z)-3-hepten-1-ol; (Z)-3-octen-1-ol; Rate coefficients; Gas-phase products; Secondary organic aerosol;