Atmospheric Environment (v.45, #28)

Short-term variability of experimental ultraviolet and total solar irradiance in Southeastern Spain by M. Antón; J.E. Gil; A. Cazorla; J. Fernández-Gálvez; I. Foyo-Moreno; F.J. Olmo; L. Alados-Arboledas (4815-4821).
This paper quantifies the very short-term variability of the total solar irradiance and the ultraviolet erythemal irradiance (UVER) averaged over 1-min intervals at Granada (Southeastern Spain). A statistical analysis for a four-year period (January 2006–December 2009) under different cloudiness and characterized by the amount of cloud cover (oktas) retrieved from an All-Sky Imager located next to the radiometers is presented. Very short-term variability of the total solar irradiance was larger than UVER fluctuations under cloudy conditions (above three oktas), in accordance with previous works found in the literature. Nevertheless, for cloud cover bellow three oktas the opposite was true; the median relative 1-min fluctuation was larger for UVER than for total solar irradiance. Moreover, while the coefficient of variation (CV) for UVER presented a clear dependence on the solar zenith angle (SZA) under completely cloud-free conditions (from 1.5% for SZA = 20° to 9.5% for SZA = 65°), the CV of the total solar irradiance was under 1.3% with a more stable behaviour for the entire range of SZA. Large differences were found for cloud cover of seven oktas, where the median diurnal 1-min variability for total solar irradiance was 3.9% min−1 compared to 2.5% min−1 for UVER data. Additionally, an episode with surface total solar irradiance higher than its corresponding extraterrestrial value is analyzed.► One-minute changes for UV and total irradiance increase with the cloud fraction. ► One-minute changes could reach pick values larger than 100% min−1. ► The very short-term fluctuations slightly decrease for overcast conditions.
Keywords: Ultraviolet irradiance; Total solar irradiance; Broadband UV radiometer; Short-term variability;

Using advanced dispersion models and mobile monitoring to characterize spatial patterns of ultrafine particles in an urban area by Leonard M. Zwack; Steven R. Hanna; John D. Spengler; Jonathan I. Levy (4822-4829).
In urban settings with elevated bridges, buildings, and other complex terrain, the relationship between traffic and air pollution can be highly variable and difficult to accurately characterize. Atmospheric dispersion models are often used in this context, but incorporating background concentrations and characterizing emissions at high spatiotemporal resolution is challenging, especially for ultrafine particles (UFPs). Ambient pollutant monitoring can characterize this relationship, especially when using continuous real-time monitoring. However, it is challenging to quantify local source contributions over background or to characterize spatial patterns across a neighborhood. The goal of this study is to evaluate contributions of traffic to neighborhood-scale air pollution using a combination of regression models derived from mobile UFP monitoring observations collected in Brooklyn, NY and outputs from the Quick Urban & Industrial Complex (QUIC) model. QUIC is a dispersion model that can explicitly take into account the three-dimensional shapes of buildings. The monitoring-based regression model characterized concentration gradients from a major elevated roadway, controlling for real-time traffic volume, meteorological variables, and other local sources. QUIC was applied to simulate dispersion from this same major roadway. The relative concentration decreases with distance from the roadway estimated by the monitoring-based regression model after removal of background and by QUIC were similar. Horizontal contour plots with both models demonstrated non-uniform patterns related to building configuration and source heights. We used the best-fit relationship between the monitoring-based regression model after removal of background and the QUIC outputs (R 2 = 0.80) to estimate a UFP emissions factor of 5.7 × 1014 particles/vehicle-km, which was relatively consistent across key model assumptions. Our joint applications of novel techniques for analyzing mobile monitoring data and the advanced dispersion model QUIC provide insight about source contributions above background levels and spatiotemporal air pollution patterns in urban areas.► Used mobile monitoring and dispersion modeling to examine spatial patterns of UFPs. ► Mobile-monitoring data and outputs from QUIC model displayed similar patterns. ► Used QUIC model to back-calculate an emissions factor for UFPs in urban area. ► Estimated UFP emissions factor of 5.7 × 1014 particle #/vehicle-km for New York City.
Keywords: Ultrafine particles; QUIC; Urban air quality; Dispersion modeling; Regression modeling; New York City;

Global emission projections of particulate matter (PM): I. Exhaust emissions from on-road vehicles by Fang Yan; Ekbordin Winijkul; Soonkyu Jung; Tami C. Bond; David G. Streets (4830-4844).
We present global emission projections of primary particulate matter (PM) from exhaust of on-road vehicles under four commonly-used global fuel use scenarios from 2010 to 2050. The projections are based on a dynamic model of vehicle population linked to emission characteristics, SPEW-Trend. Unlike previous models of global emissions, this model incorporates more details on the technology stock, including the vehicle type and age, and the number of emitters with very high emissions (“superemitters”). However, our estimates of vehicle growth are driven by changes in predicted fuel consumption from macroeconomic scenarios, ensuring that PM projections are consistent with these scenarios. Total emissions are then obtained by integrating emissions of heterogeneous vehicle groups of all ages and types. Changes in types of vehicles in use are governed by retirement rates, timing of emission standards and the rate at which superemitters develop from normal vehicles. Retirement rates are modeled as a function of vehicle age and income level with a relationship based on empirical data, capturing the fact that people with lower income tend to keep vehicles longer. Adoption dates of emission standards are either estimated from planned implementation or from income levels.We project that global PM emissions range from 1100 Gg to 1360 Gg in 2030, depending on the scenario. An emission decrease is estimated until 2035 because emission standards are implemented and older engines built to lower standards are phased out. From 2010 to 2050, fuel consumption increases in all regions except North America, Europe and Pacific, according to all scenarios. Global emission intensities decrease continuously under all scenarios for the first 30 years due to the introduction of more advanced and cleaner emission standards. This leads to decreasing emissions from most regions. Emissions are expected to increase significantly in only Africa (1.2–3.1% per year). Because we have tied emission standards to income levels, Africa introduces those standards 30–40 years later than other regions and thus makes a remarkable contribution to the global emissions in 2050 (almost half). All Asian regions (South Asia, East Asia, and Southeast Asia) have a decreasing fractional contribution to global totals, from 32% in 2030 to around 22% in 2050. Total emissions from normal vehicles can decrease 1.3–2% per year. However, superemitters have a large effect on emission totals. They can potentially contribute more than 50% of global emissions around 2020, which suggests that they should be specifically addressed in modeling and mitigation policies. As new vehicles become cleaner, the majority of on-road emissions will come from the legacy fleet. This work establishes a modeling framework to explore policies targeted at that fleet.► Projections of PM emissions from on-road vehicles from a global vehicle fleet model. ► Fleet dynamics linked to income levels under four economic scenarios. ► Lower emission intensity dominates increasing fuel use, resulting in lower emission. ► With possible contribution over 50% after 2020, superemitters may dominate emission.
Keywords: Emission; Projection; Transportation; On-road vehicle; Particulate matter (PM); Technology;

The importance of stratospheric–tropospheric transport in affecting surface ozone concentrations in the western and northern tier of the United States by Allen S. Lefohn; Heini Wernli; Douglas Shadwick; Sebastian Limbach; Samuel J. Oltmans; Melvyn Shapiro (4845-4857).
Stratospheric–tropospheric exchange (STE) processes contribute at both high and low-elevation monitoring sites to background ozone (O3) concentrations. This study addresses the importance of stratospheric intrusions contributing to enhanced hourly average surface O3 concentrations (i.e., ≥50 ppb) at 12 O3 monitoring stations in the western and northern tier of the US for 2006, 2007, and 2008. The Lagrangian Analysis Tool (LAGRANTO) trajectory model identified specific days when stratosphere-to-troposphere transport was optimal to elevate surface O3 levels. The coincidences between the number of days with a daily maximum hourly average O3 concentration ≥ 50 ppb and stratosphere-to-troposphere transport to surface (STT-S > 0) were quantified. The high-elevation site at Yellowstone National Park (NP) in Wyoming exhibited the most coincidences (i.e., more than 19 days a month) during the spring and summer for hourly average O3 concentrations ≥ 50 ppb with STT-S > 0 of the 12 monitoring sites. At this site, the daily maximum hourly springtime average O3 concentrations were usually in the 60–70 ppb range. The maximum daily 8-h average concentrations mostly ranged from 50 to 65 ppb. At many of the lower-elevation sites, there was a preference for O3 enhancements to be coincident with STT-S > 0 during the springtime, although summertime occurrences were sometimes observed. When statistically significant coincidences occurred, the daily maximum hourly average concentrations were mostly in the 50–65 ppb range and the daily maximum 8-h average concentrations were usually in the 50–62 ppb range. For many cases, the coincidences between the enhancements and the STT-S events occurred over a continuous multiday period. Supplementary observations, such as (1) the greater frequency of O3 concentration enhancements occurring during the springtime versus other times of the year, (2) the elevation dependency of the frequency of enhancements, (3) the year-to-year variability, (4) the timing of the hour-by-hour occurrences of the O3 concentration enhancements within and across monitoring sites, and (5) the detailed analyses of O3 enhancement events at specific sites, provide additional support for our modeling and statistical results. Our analysis provides an important step in better understanding the variability of natural background O3 concentrations. The study has provided insight into stratospheric intrusions, with emphasis on the combined role of quasi-isentropic large-scale advection and mesoscale boundary layer turbulence for stratospheric air influencing enhanced surface O3.► This study addresses the importance of STT with enhanced ozone. ► A trajectory model was used in the study. ► Many sites exhibited frequent coincidences between enhanced ozone and STT.
Keywords: Background ozone; Stratosphere–troposphere exchange; Stratosphere-to-troposphere transport; Surface ozone;

Exposures to volatile organic compounds (VOCs) are ubiquitous due to emissions from personal, commercial and industrial products, but quantitative and representative information regarding long term exposure trends is lacking. This study characterizes trends from 1988 to 2004 for the 15 VOCs measured in blood in five cohorts of the National Health and Nutrition Examination Survey (NHANES), a large and representative sample of U.S. adults. Trends were evaluated at various percentiles using linear quantile regression (QR) models, which were adjusted for solvent-related occupations and cotinine levels. Most VOCs showed decreasing trends at all quantiles, e.g., median exposures declined by 2.5 (m,p-xylene) to 6.4 (tetrachloroethene) percent per year over the 15 year period. Trends varied by VOC and quantile, and were grouped into three patterns: similar decreases at all quantiles (including benzene, toluene); most rapid decreases at upper quantiles (ethylbenzene, m,p-xylene, o-xylene, styrene, chloroform, tetrachloroethene); and fastest declines at central quantiles (1,4-dichlorobenzene). These patterns reflect changes in exposure sources, e.g., upper-percentile exposures may result mostly from occupational exposure, while lower percentile exposures arise from general environmental sources. Both VOC emissions aggregated at the national level and VOC concentrations measured in ambient air also have declined substantially over the study period and are supportive of the exposure trends, although the NHANES data suggest the importance of indoor sources and personal activities on VOC exposures. While piecewise QR models suggest that exposures of several VOCs decreased little or any during the 1990’s, followed by more rapid decreases from 1999 to 2004, questions are raised concerning the reliability of VOC data in several of the NHANES cohorts and its applicability as an exposure indicator, as demonstrated by the modest correlation between VOC levels in blood and personal air collected in the 1999/2000 cohort. Despite some limitations, the NHANES data provides a unique, long term and direct measurement of VOC exposures and trends.► Concentrations of volatile organic compounds (VOCs) in blood are exposure biomarkers. ► VOC biomarkers were measured in NHANES, a population-based study, from 1988 to 2004. ► Trend analysis of the NHANES VOC data show exposures declining by 2.5–6.4% per year. ► Emissions and ambient concentrations of VOCs are supportive of the exposure trends. ► Some of the VOC data in the earlier NHANES cohorts appear unreliable.
Keywords: Air sampling; Blood; Exposure; NHANES; Quantile regression; Trends; Volatile organic compounds;

Data assimilation obtains improved estimates of the state of a physical system by combining imperfect model results with sparse and noisy observations of reality. In the four dimensional variational (4D-Var) framework data assimilation is formulated as an optimization problem, which is solved using gradient based optimization methods. The 4D-Var gradient is obtained by forcing the adjoint model with observation increments. The construction of the adjoint model requires considerable development effort. In the continuous approach the adjoint differential equations are discretized. In the discrete approach the numerical solution of the forward equations is differentiated. The two routes lead to different gradients.In this paper we investigate numerically the effect of using discrete and continuous adjoints of the advection equation in chemical transport modeling. Continuous advection adjoints are easily implemented by calling the same advection subroutines as the forward model, with a sign change for the winds, and with rescaling the solution. Discrete advection adjoints involve the differentiation of a nonlinear, monotonic advection scheme like the piecewise parabolic method. The numerical experiments are carried out with CMAQ-ADJ. The results show that, while discrete advection adjoints are more accurate in point-to-point comparisons against finite differences, the continuous adjoints of advection perform better as gradients for optimization in 4D-Var data assimilation.► The implementation and validation of the discrete advection adjoints in CMAQ-ADJ are presented. ► The discrete advection adjoints are more accurate in point-to-point validation tests against finite differences. ► The continuous advection adjoints lead to superior performance of the optimization in 4D-Var data assimilation.
Keywords: Chemical data assimilation; Continuous adjoint; Discrete adjoint;

As of 2010, the Taipei mass rapid transit (MRT) comprised 8 rapid transit lines stretching 90.5 km and linking 82 stations. Currently, over 1.4 million commuters a day travel on the Taipei MRT system. However, information related to the characteristics of indoor air quality at ground-level and in underground stations in the Taipei MRT system is limited. This study used portable monitors to measure the PM10, PM2.5, particle number (PN), CO, and CO2 levels at an underground (UG) and two ground-level (AG1 and AG2) MRT stations on the same rapid transit line. All measurements were taken between August 20 and November 12, 2010. The mean PM10 and PM2.5 levels in underground environments (underground ticket hall and platform of the UG and underground platform of the AG1) are approximately 51–65 μg m−3 and 25–40 μg m−3, respectively. Additionally, the mean PM10 and PM2.5 levels in ground-level indoor environments (ground-level ticket halls of the AG1 and AG2) are approximately 44–48 μg m−3 and 26–29 μg m−3, respectively. Measurement results reveal that PM levels in underground environments are greater than those in ground-level indoor environments. PM levels in ground-level indoor environments are strongly associated with outdoor ambient PM levels, while PM levels in underground environments are less influenced by outdoor ambient conditions. The presence of coarse PM in the underground environments may have been generated internally through the mechanical friction processes or re-suspended by the movement of commuters, and fine PM is likely transferred from its source outside the station. The mean PM2.5-to-PM10 ratios in underground environments are 0.45–0.79, and at ground-level indoor environments are approximately 0.58. Based on differences in the environment conditions among these selected locations, it is reasonable to assume that PM2.5-to-PM10 ratios in underground and ground-level MRT stations will not be consistent, even those on the same metro line. Furthermore, low PN and CO levels are observed in underground environments. Mean PN and CO levels in underground environments are 9.5 × 103–1.7 × 104 particles cm−3 and 0.30–0.48 ppm, respectively, and significantly lower than those in outdoor environments by approximately 0.3–0.6 times. However, the CO2 levels in underground environments are 574–1051 ppm and significantly higher than those in outdoor environments, by approximately 1.3–2.4 times. The CO2 in underground environments is likely elevated by the exhalation of commuters.► Coarse PM in the underground environments may have been generated internally. ► Fine PM is likely transferred from its source outside the station. ► Low PN and CO levels are observed in underground environments.
Keywords: PM10; PM2.5; Particle number; CO; CO2; Taipei mass rapid transit system;

A numerical study, used for particle size distributions of several classical aerosol types, is conducted in this paper. By improving the log-normal distribution model in previous paper, we employ the stochastic particle swarm optimization (SPSO) algorithm associated with a multi-lognormal distribution model. The nonambiguity and robustness of SPSO with this model is validated. We recover particle size distributions of two classical aerosol types using the measured AOT data (at wavelengths λ  = 0.400, 0.690, 0.870, 1.020 μm) obtained from AERONET at different time. The results show that the model of this paper presents characteristics of aerosol particle size distributions at different regions and time. And this model shows good practicability to distinguish aerosol types and calculate particle size distributions.► Retrieving particle size distribution using multi-lognormal distribution model by SPSO. ► Calculating the particle size distributions and distinguishing the aerosol type with this model. ► Comparing the different characteristics of different aerosol types in two typical regions.
Keywords: Aerosol; Particle size distribution; SPSO; Multi-lognormal distribution model;

Procuring the regional urbanization and industrialization effect on ozone pollution in Pearl River Delta of Guangdong, China by Y.N. Zhang; Y.R. Xiang; L.Y. Chan; C.Y. Chan; X.F. Sang; R. Wang; H.X. Fu (4898-4906).
The decade before 2006 was a period of growing regional urbanization and industrialization. Also, the 5-year plan period (2001–2005) is a half decade of fast regional urban expansion with high population growth within the PRD city clusters, At the same time, the PRD region becomes a leading manufacturing center of the world. Industrial expansion in this region of GD was characterized by the spread of industrial activities from hot spots in GZ city and around Foshan and Dongguan to widely distributed patches of industrial active districts, mostly in the seven newly agglomerate formed and urbanizing prefectural municipalities. To provide transportation communication between GZ city and the municipal cities, a system of highways was built and a region road-network surfaced for the connection of the expanding municipal cities and their sub-urban areas as well as the patches of industrial districts, within their municipalities Also, a network of power plants was built at its periphery. As a result, the ozone precursors, NOx and VOC emission from vehicles, industries and power plants increased region wide, and in particular in the newly formed prefectural municipalities. Hence, the whole region was undergoing a redistribution of O3 precursors and ozone pollution, following the path of redistribution of population and industrial activity in the Pearl River Delta region of Guangdong.Study and report on O3 pollution before 2000 is rare and there were only a few case studies in 2000 and 2004. By 2006, O3 data supplied by the newly established PRD Regional Air Quality Monitoring Network become available for the study of regional O3 pollution. Also relevant information on the new dimension of regional urbanization and industrialization for the PRD region of GD, as well as a highly resolved temporal and spatial PRD region NOx and VOC emission inventory surfaced. Thus, 2006 is a good year to procure the regional urbanization and industrial effect, and to produce a snapshot of the regional and area specific ozone pollution in the PRD region of GD. Patterns of annual ozone variation and seasonal ozone diurnal cycles for urban/sub-urban areas, for metropolitan city, for rural areas and for special area in the PRD region of Guangdong are presented for future reference.► A vast regional road-network prompted regional wide urban, sub-urban and rural agglomeration and traffic. ► Redistribution of NOx and VOC due to increase and spread of road traffic, power plant and industrial emissions. ► Effect of increasing regional urbanization and industrialization on O3 pollution patterns in PRD. ► A common ‘urban’ O3 pollution pattern for a majority of newly agglomerate formed prefectural municipalities. ► Area specific moderation of urban pattern in metropolitan, rural and regional sites and its impacting factors.
Keywords: Ozone; Urbanization; Industrialization; Regional; Pearl River Delta;

Ultrafine particles pollution in urban coastal air due to ship emissions by Yenny González; Sergio Rodríguez; Juan Carlos Guerra García; Juan Luis Trujillo; Rosa García (4907-4914).
Two years of experimental data (2008–2009) of particle number (≥2.5 nm diameter) and black carbon concentrations and of gaseous pollutants recorded in the ambient air of a coastal city were analysed in order to assess the impact of ship emissions on the ultrafine particles (UFPs, diameter <100 nm) concentrations in urban ambient air. The observed relationship between particle number and the other air pollutants, allowed segregating the contribution of vehicle exhaust and of ship emissions to the UFP concentrations in the urban ambient air. Vehicle exhausts resulted in high concentrations of UFP, black carbon and NOx during the early morning, when UFPs showed concentrations 15–30 × 103 cm−3. Pollutants linked to this source rapidly decreased when inland sea breeze started to flow. However, this airflow resulted in inland transport of ship plumes (emitted in the harbour and in the sea) into the city and in high concentrations of SO2, NOx and UFP from mid morning to the evening. In this context, UFPs showed concentrations 35–50 × 103 cm−3, being the 65–70% of these linked to ship emissions mostly related to SO2 (gas phase precursor). UFPs pollution is a matter of concern due to adverse effects on human health. Up to the date, most of studies on urban air quality and UFPs have focused on vehicle exhaust emissions. This study shows how inland transport of ship plumes due to sea breeze blowing results in UFPs pollution in coastal cities.Display Omitted► Urban ambient air quality. ► Ultrafine particles emissions by ships. ► Inland transport of ship plumes by sea breeze. ► Ultrafine particles emissions by vehicle exhausts. ► Sources and processes contributing to ultrafine particles.
Keywords: Ultrafine particles; Ship emissions; Vehicle exhaust; Urban air quality;

Non-microbial methane emissions from fresh leaves: Effects of physical wounding and anoxia by Zhiping Wang; Frank Keppler; Markus Greule; John T.G. Hamilton (4915-4921).
Non-microbial methane (CH4) emissions from plants might be widespread in nature. However, this unexpected source and its global strength still remain controversial. Very recently it has been suggested that CH4 release by plants may be linked to environmental stress. Using fresh leaves of 73 plants, including those from trees, shrubs and herbaceous species, a series of laboratory experiments have been employed to quantify CH4 emissions and to examine the effect of physical wounding and anoxia. Approximately half of the plants investigated emitted CH4 at rates ≥0.2 ng gdw−1h−1. Emissions from detached intact fresh leaves were in the ranges of 0.20–2.25 and 0.38–2.14 ng gdw−1h−1 when incubated under air and anoxic conditions, respectively. Strongly enhanced emissions were monitored when leaves were physically wounded and/or incubated under anoxia. Several experiments were conducted to verify in-situ emissions of CH4 and exclude microbial activity as the source. Average short-lived pulsed CH4 emissions of 53.4 ng gdw−1h−1, with a range of 0–687 ng gdw−1h−1, were observed from ground fresh leaves of the 60 plant species investigated, indicating that pulse emissions from plants immediately following environmental stress such as wounding need consideration to constrain global CH4 emissions from vegetation. This type of emission may also assist with the delineation of the mechanism involved in non-microbial CH4 formation.► Methane emissions were investigated from fresh leaves of plants. ► The emissions were strongly enhanced by physical wounding and anoxia. ► The emissions were confirmed to be non-microbial. ► Pulse emissions immediately following environmental stress were important.
Keywords: Greenhouse gas; Environmental stress; Kinetics; Lavandula angustifolia; Plant; Global change;

Methane emissions in India: Sub-regional and sectoral trends by Amit Garg; Bhushan Kankal; P.R. Shukla (4922-4929).
This paper uses the 2006 IPCC Guidelines and latest country specific emission factors to estimate Indian methane emissions at sectoral and district level for the years 1990, 1995, 2005 and 2008. The estimates show that while methane emissions have increased steadily over past two decades, their share in India’s aggregate GHG emissions has declined from 31% in 1985 to 27% in 2008 mainly due to relatively higher growth CO2 emissions from the fossil fuels. The estimates for the year 2008 show that: i) agriculture sector, which employed two-thirds of India’s population and contributed 17% of GDP, accounted for 23% of India’s GHG emissions ii) 83% of country’s methane emissions are contributed by enteric fermentation, manure use and rice production, and iii) methane emissions from urban solid waste are steadily rising over the past two decades; their share in aggregate methane emissions has reached 8%. Resting on the disaggregated emissions estimates, the paper argues for using geographical and sectoral flexibilities to develop a roadmap for mitigation of methane emissions for India.► Indian methane emissions have grown from 18.85 Tg in 1985 to 20.56 Tg in 2008. ► Enteric fermentation contributes 50–60% over the years. ► Uttar Pradesh and Andhra Pradesh are the hotspot methane emitting states of India. ► The mean and variability of methane emissions per district per year have increased over 1990–2008.
Keywords: Methane; Sectoral; Sub-regional; India;

This paper examines the effects of near-field pollutant dispersion characteristics of upstream buildings in the built environment and compares them to the ASHRAE 2007 model. Wind tunnel simulations were performed for nine different building configurations for three exhaust momentum ratios (M) and three stack heights (h s). The effect of spacing (S) between the buildings and stack location from the upwind edge of the emitting building (X) were also investigated. Measurements of gas concentrations were performed on the roof and leeward wall of the emitting and upstream buildings. Data show that within the recirculation zone a change in along wind dimension of the upstream building has a negligible effect on the dilution of emissions from the downwind building. However, spacing between buildings and the height of the upstream building were found to be critical parameters in assessing plume dilution. The plume geometry is largely governed by the upwind dimensions of the upstream building. predicts lower dilution for all cases examined, leading to conservative or very conservative design. However, the ASHRAE 2007 cannot model the effect of upstream buildings, thus further investigation of its formulations is required. Guidelines for placement of intake and stack on the roof of the building to avoid problems of re-ingestion are discussed.► Effect of near-field pollutant dispersion characteristics of upstream buildings. ► Pollutants released from rooftop stacks affect both buildings. ► Plume geometry is different for upstream cases. ► Height of upstream building primarily affects the Plume geometry. ► Design guidelines for placement of stack and intake are presented.
Keywords: Dispersion; Wind tunnel; Upstream building; Recirculation zone; Stack; ASHRAE 2007;

Decoupled direct sensitivity analysis of regional ozone pollution over the Pearl River Delta during the PRIDE-PRD2004 campaign by Xuesong Wang; Yuanhang Zhang; Yongtao Hu; Wei Zhou; Limin Zeng; Min Hu; Daniel S. Cohan; Armistead G. Russell (4941-4949).
High-order decoupled direct method is applied to investigate O3-precursor sensitivity during the Program of Regional Integrated Experiments of Air Quality over the Pearl River Delta (PRD) Region, China in October 2004 (PRIDE-PRD2004). First-order sensitivity coefficients of O3 show a NOx-inhibited chemistry along the polluted plumes in central and southern PRD areas, and a NOx-limited condition over larger areas of the western, eastern and northern PRD. A nonlinearity ratio derived from O3 sensitivity coefficients clearly describes the nonlinear feature of O3 chemistry over PRD. The distributions of NOx- and VOC-sensitive regimes are determined by near-ground flow conditions, and O3 sensitivity is found to shift from VOC-sensitive conditions to NOx-sensitive conditions from morning to afternoon in central and western areas of the PRD. Elevated surface O3 around mid-afternoon in October mainly occurred in VOC-sensitive regions or those NOx-limited areas in close vicinity of the VOC-sensitive regions. Ratios of H2O2/HNO3 and peroxides/HNO3 for indicating O3-precursor sensitivity are evaluated and the transition values of 0.45 for H2O2/HNO3 and 0.80 for peroxides/HNO3 were found, with an overall accuracy of about 92% for sensitivity identification at elevated O3 hours in afternoons during the campaign.► HDDM-3D is applied to assess O3–NOx–VOC sensitivities for the first time in the PRD. ► A spatially non-uniform & temporally dynamic O3 sensitivity is characterized in PRD. ► A revised nonlinearity ratio illustrates nonlinear features of O3 chemistry in PRD. ► A new method is proposed to identify the transition value of photochemical indicator. ► A transition value of 0.45 for H2O2/HNO3 is determined with overall accuracy of 92%.
Keywords: Ozone; CMAQ; Decoupled direct method; Photochemical indicator; Pearl River Delta;

Recent lead deposition trends in the Czech Republic as recorded by peat bogs and tree rings by Milan Zuna; Martin Mihaljevič; Ondřej Šebek; Vojtěch Ettler; Michael Handley; Tomáš Navrátil; Viktor Goliáš (4950-4958).
The lead (Pb) content and 206Pb/207Pb ratio were studied in three peat profiles dated by 210Pb from the border-area mountains of the Czech Republic and in the tree rings of spruce trees located in their immediate vicinity. Both archives document a similar progress in Pb pollution levels and Pb accumulation in the 1950’s–1990’s. The deposition rate (DR) of Pb in peat bogs attained maximum values of 40 mg Pb m−2  y−1 in the “Black Triangle” area and 15 mg Pb m−2  y−1 in more distant areas in this period. The Pb isotopic record of both archives from the contaminated area exhibit a similar trend in the presence of the individual sources of Pb, in which Pb derived from combustion of coal predominates. The peat cores in more distant areas document well the effect of automobile Pb in the atmosphere and its substantial reduction after 2000. The two archives differ in individual patterns following from the differences in the rates of formation of their biomass and different means of deposition of Pb in the two archives.► Peat cores and tree rings document similar variations in Pb emissions. ► The Pb contents in the tree rings and peats document well the decrease in Pb emissions. ► Changes in the 206Pb/207Pb ratio reflect the different characters of the two archives.
Keywords: Lead; Deposition; Peat deposit; Tree ring; Pb isotopes;

Tobacco smoke aging in the presence of ozone: A room-sized chamber study by Lauren M. Petrick; Mohamad Sleiman; Yael Dubowski; Lara A. Gundel; Hugo Destaillats (4959-4965).
Exposure to tobacco pollutants that linger indoors after smoking has taken place (thirdhand smoke, THS) can occur over extended periods and is modulated by chemical processes involving atmospheric reactive species. This study investigates the role of ozone and indoor surfaces in chemical transformations of tobacco smoke residues. Gas and particle constituents of secondhand smoke (SHS) as well as sorbed SHS on chamber internal walls and model materials (cotton, paper, and gypsum wallboard) were characterized during aging. After smoldering 10 cigarettes in a 24-m3 room size chamber, gas-phase nicotine was rapidly removed by sorption to chamber surfaces, and subsequently re-emitted during ventilation with clean air to a level of ∼10% that during the smoking phase. During chamber ventilation in the presence of ozone (180 ppb), ozone decayed at a rate of 5.6 h−1 and coincided with a factor of 5 less nicotine sorbed to wallboard. In the presence of ozone, no gas phase nicotine was detected as a result of re-emission, and higher concentrations of nicotine oxidation products were observed than when ventilation was performed with ozone-free air. Analysis of the model surfaces showed that heterogeneous nicotine-ozone reaction was faster on paper than cotton, and both were faster than on wallboard. However, wallboard played a dominant role in ozone-initiated reaction in the chamber due to its large total geometric surface area and sink potential compared to the other substrates. This study is the first to show in a room-sized environmental chamber that the heterogeneous ozone chemistry of sorbed nicotine generates THS constituents of concern, as observed previously in bench-top studies. In addition to the main oxidation products (cotinine, myosmine and N-methyl formamide), nicotine-1-oxide was detected for the first time.► Ozone reactions with tobacco smoke constituents under realistic indoor conditions. ► Heterogeneous chemistry of nicotine leads to formation of surface-bound and gas phase byproducts. ► Oxidation byproducts also found in suspended particulate matter. ► Evaluated the reactivity of nicotine sorbed on various surfaces (papel > cotton > gypsum wallboard). ► Ozone decayed at a rate of 5.6 h−1 and coincided with a factor of 5 less nicotine sorbed to wallboard.
Keywords: Nicotine; Heterogeneous chemistry; SVOC; Indoor surfaces; Sorption; Thirdhand tobacco smoke;

Mass size distributions of soluble sulfate, nitrate and ammonium in the Madrid urban aerosol by J. Plaza; M. Pujadas; F.J. Gómez-Moreno; M. Sánchez; B. Artíñano (4966-4976).
This paper analyzes the mass size distribution of some inorganic species present in the atmospheric aerosol from a field campaign carried out in Madrid throughout a complete year (February 2007–February 2008). Samplings were performed by means of a micro-orifice uniform deposit impactor (MOUDI). Ambient air was sampled during consecutive nocturnal and diurnal periods, and diurnal/nocturnal behaviors were compared for the twenty night-day sampling pairs that were gathered. Annual and seasonal averages were obtained, and some case studies under specific atmospheric conditions are discussed in the paper.Results have shown that the sulfate and ammonium mass was concentrated in the accumulation mode, between 0.18 and 0.56 μm, so that gas-phase and condensation processes for secondary aerosol formation prevailed during the sampling periods in this area. An exception to this behavior was found during a fog event when distributions for these two species were centered in the 0.56–1 and 1–1.8 μm size stages, corresponding to the droplet mode. In most of the samples, the ammonium mass measured in these size ranges was enough or almost enough to neutralize inorganic acidity by formation of ammonium sulfate and nitrate. However, a significant sulfate mass not neutralized by ammonium was found in the impactor backup quartz filter (aerodynamic diameter < 0.056 μm). The concentration of this sulfate and its contribution to the ultrafine fraction mass was higher under good dispersive conditions, prevailing in summer, when particle growth processes are not so favored due to the higher atmospheric dilution factors. The origin of this ultrafine sulfate has been attributed to direct emissions from traffic, associated to the nucleation mode.Regarding the nitrate concentration, it was found higher in the coarse mode than in the accumulation mode on an annual basis. The highest concentrations were measured in winter episodic situations. The marked seasonal variability shown in the accumulation mode by this species is related to the volatility of ammonium nitrate. Among all the studied ions, nitrate also presented the highest differences between the diurnal and nocturnal concentrations in all size ranges. This is probably related to the short time scale required for its formation from gaseous precursors.► Particulate nitrate, sulfate and ammonium are concentrated in the accumulation range. ► Particulate nitrate has a marked seasonal effect, with maximum value in winter. ► In-cloud sulfate formation and ammonium uptake was observed during a fog event. ► Ultrafine particles (<0.056 μm) were acidic due to a significant mass of sulfate.
Keywords: Urban aerosol; Mass size distribution; Particulate nitrate; Particulate sulfate; Particulate ammonium; MOUDI;

An understanding of the complexity of spatial-temporal variations in regional air quality and its respective source contributors is one of the priority research areas due to the adverse effects of air pollution on human health and the environment. In this paper, we integrate air dispersion modeling and Geographic Information System (GIS) based spatial analysis methods to characterize regional ambient air quality at a relatively fine geographical scale (1 km × 1 km) while ascertaining source contributors. The temporal variation analysis shows that sulfur dioxide (SO2) pollution in Dallas County, Texas did not consistently increase or decrease from 1996 to 2002. The lowest and highest mean levels of annual SO2 concentrations at all the receptors (n  = 2000) were 0.39 μg m−3 and 2.32 μg m−3 in 2001 and 2002, respectively. Meanwhile, analysis results suggest that the annual SO2 concentrations in a small part of Dallas County slightly declined with the highest value of −1.00 μg m−3 over the 1996–2002 period, while most of the county experienced increased SO2 concentration levels from 0.00 to 0.25 μg m−3. In addition, the source apportionment analysis demonstrated that the variations in total annual SO2 concentrations in Dallas County from 1996 to 2002 were significantly different from those by source classification. That is, compared to industrial emission sources, on-road vehicle emission sources caused variations in annual SO2 concentrations with relatively larger extents (power of determinant = 0.42). However, extreme variations in concentrations were due to industrial emission sources (3.45% vs. 0.00%). Based on these observations, it can be concluded that the combination of air dispersion modeling and GIS-based spatial analysis shows promise to overcome the drawbacks of sparse intraurban air quality monitoring in characterizing the spatial-temporal micro-variations in regional ambient air quality and ascertaining roles of source contributors over long-term periods.► A dispersion-GIS model of regional source contributors to air pollution. ► Spatial-temporal variations were not consistent over varying time periods. ► The variations in air quality were markedly different by source classification. ► Source contributors of micro-variations in regional air quality can be ascertained.
Keywords: Air pollution; AERMOD; SO2; Environmental exposure; GIS; Intraurban air quality;

Diagnosis of surface damage induced by air pollution on 20th-century concrete buildings by I. Ozga; A. Bonazza; E. Bernardi; F. Tittarelli; O. Favoni; N. Ghedini; L. Morselli; C. Sabbioni (4986-4995).
The present work focuses on the impact of anthropogenic multi-pollutants on modern concrete buildings exposed in two different European urban areas: Centennial Hall in Wroclaw (Poland) and Casa Galleria Vichi in Florence (Italy). Through a range of analytical techniques the complete characterization of the damage layer collected from the buildings under study has been achieved for the first time, including quantitative measurements of the carbon content. The experimental results allow the identification and prioritization of the air pollutants responsible for the surface deterioration, finding gypsum to be the main damage product on surfaces sheltered from rain runoff, with embedded particulate matter, especially carbonaceous particles, responsible for darkening of the building walls. The discrimination of carbon fractions shows different concentrations of elemental and organic carbon within the damage layers, depending on the location of the buildings. This step is essential for identifying the anthropogenic sources causing deterioration on the buildings, including the aesthetic impairment of surfaces. The contribution of air pollutants is also reflected by the elements found in the damage layers, while the evaluation of the enrichment factors is useful for identifying the elements of anthropogenic origin.► The research focused on the impact of multi-pollutants on concrete buildings. ► SO2 and particles emitted by combustion sources have priority in damage formation. ► Results show the correlation between building location and damage layer composition. ► Carbon fractions analyses was a key in finding pollutant sources causing damage. ► Elemental data processing allowed the identification of the origin of elements.
Keywords: Concrete building; Black crust; Carbon fraction; Enrichment factor; Combustion sources;

A decision making framework for assessing control strategies for ground level ozone by Neelesh V. Sule; Victoria Chen; Melanie Sattler (4996-5004).
This paper presents a decision-making framework (DMF) for selecting ozone control strategies based on reductions of precursor emissions that are targeted by time and location. Conventional across-the-board reductions are uniform throughout the region and throughout the day. The DMF is comprised of four phases: (1) Initialization, (2) Experimental Design and Data Mining, (3) Metamodeling, and (4) Optimization. This paper details the first three and presents an example for selecting strategies in the optimization phase. Specifically, to enable an efficient optimization phase, metamodels for maximum 8-h averaged ozone are employed to represent the output from an advanced photochemical model, such as CAMx. The process for each phase is presented for a Dallas Fort Worth (DFW) 2009 future emission scenario, based on a 10-day meteorological episode from August 13–22, 1999. Over 600 emission variables were identified in three source categories viz. point, area (includes non-road) and line (on-road). The DFW application demonstrates how control measures can be efficiently explored in a targeted manner instead of using the conventional “trial and error” approach.► We developed a decision-making framework (DMF) for reducing ozone. ► It uses statistical, data mining, and optimization methods to explore control measures. ► DMF identifies key sources, time periods, and ozone control strategies. ► DMF can be used to explore control strategies in a targeted manner. ► DMF is a valuable tool for policy makers to identify sensitive control strategies.
Keywords: Metamodeling; Optimization; Ozone; Decision-making framework; Air quality;

A literature review of concentrations and size distributions of ambient airborne Pb-containing particulate matter by Seung-Hyun Cho; Jennifer Richmond-Bryant; Jonathan Thornburg; Jeff Portzer; Robert Vanderpool; Kevin Cavender; Joann Rice (5005-5015).
The final 2008 lead (Pb) national ambient air quality standards (NAAQS) revision maintains Pb in total suspended particulate matter as the indicator. However, the final rule permits the use of low-volume PM10 (particulate matter sampled with a 50% cut-point of 10 μm) Federal Reference Method (FRM) monitors in lieu of total suspended particulate (TSP) monitors for some non-source-oriented monitoring. PM10 FRM monitors are known to provide more reliable concentration measurements than TSP samplers because they are omni-directional samplers and so are not biased by wind conditions. However, by design they exclude the upper tail of the particle size distribution. Hence, each monitor produces uncertainties about measured concentrations of Pb-bearing PM. Uncertainties in reported Pb data are also related to spatiotemporal variation of the concentration and size distribution of Pb-bearing PM. Therefore, a comprehensive literature review was performed to summarize the current knowledge regarding the concentration and size distribution of Pb particles in the atmosphere. The objectives of this review were to compile data that could shed light on these uncertainties, to provide insights useful during future Pb NAAQS reviews, and to identify areas where more research is needed.Results of this review indicated that Pb size distribution data are relatively limited and often outdated. Thirty-nine articles were found to have sufficiently detailed information regarding airborne Pb concentrations, study location, sample collection methods, and analytical techniques; only 16 of those papers reported Pb concentration data for multiple size fractions. For the most part, U.S. and European studies from the last forty years illustrate that the largest mode of the size distribution of airborne particle-bound Pb has shifted to larger sizes while airborne Pb concentrations have decreased in urban areas. This shift occurred as tetraethyl Pb additives in gasoline were phased out and industrial emissions and resuspended road dust became more important sources of Pb. Several studies also suggested the occurrence of long-range transport of Pb-bearing PM from industrial emissions. Uncertainties associated with these studies include influence of wind speed and direction on captured concentrations and variability in analytical techniques used to quantify Pb concentrations on the reported size distributions.► Comprehensive literature review of airborne Pb concentration and size distribution. ► Shift from mobile to industrial sources reduced primary mode of Pb size distribution. ► This review indicated Pb size distribution data are relatively limited and outdated.
Keywords: Lead; Pb; Particulate matter; PM; Particle size distribution; Concentrations;

Carbon sequestration and annual increase of carbon stock in a mangrove forest by R. Ray; D. Ganguly; C. Chowdhury; M. Dey; S. Das; M.K. Dutta; S.K. Mandal; N. Majumder; T.K. De; S.K. Mukhopadhyay; T.K. Jana (5016-5024).
Here we show carbon stock is lower in the tropical mangrove forest than in the terrestrial tropical forest and their annual increase exhibits faster turn over than the tropical forest. Variable for above ground biomass are in decreasing order of importance, breast height diameter (d), height (H) and wood density (ρ). The above ground biomass (AGB) and live below ground biomass (LBGB) held different biomass (39.93 ± 14.05 t C ha−1 versus 9.61 ± 3.37 t C ha−1). Carbon accrual to live biomass (4.71–6.54 Mg C ha−1 a−1) is more than offset by losses from litter fall (4.85 Mg C ha−1 a−1), and carbon sequestration differs significantly between live biomass (1.69 Mg C ha−1 a−1) and sediment (0.012 Mg C ha−1 a−1). Growth specific analyses of taxon density suggest that changes in resource availability and environmental constrains could be the cause of the annual increase in carbon stocks in the Sundarbans mangrove forest in contrast to the disturbance – recovery hypotheses.► Mixed species mangrove biomass regression models have been developed. ► This model can be applied to estimate spatial variation of carbon sequestration. ► Annual increase of carbon stock exhibits faster turn over than the tropical forest. ► Carbon sink in terms of live biomass is several fold greater than that of sediment. ► Resource availability is more important over recovery from a significant disturbance.
Keywords: Carbon stock; Tropical mangrove forest; Above ground biomass; Live below ground biomass; Taxon density; Environmental constrains;

A photochemical source of peroxypropionic and peroxyisobutanoic nitric anhydride by Amanda Furgeson; Levi H. Mielke; Dipayan Paul; Hans D. Osthoff (5025-5032).
A method to photochemically generate stable outputs of peroxyacetic, peroxypropionic, or peroxyisobutanoic nitric anhydride (PAN, PPN, or PiBN) in dilute gas streams is described. The PANs are generated by photolysis of excess acetone, diethyl ketone, or diisopropyl ketone in the presence of oxygen and either nitric oxide or nitrogen dioxide. The source output was characterized using a commercial NOy monitor, an in-house constructed thermal dissociation cavity ring-down spectrometer (TD-CRDS) equipped with a heated inlet for quantification of NO2, total peroxyacyl nitrates (∑PAN), and total alkyl nitrates (∑AN), and a thermal dissociation chemical ionization mass spectrometer (TD-CIMS) operated with iodide reagent ion. The TD-CIMS was calibrated (against TD-CRDS) using diffusion sources containing synthetic PAN standards. Response factors of 21, 19, and 5 counts per pptv, normalized to 1 million counts of iodide reagent ion, were found for PAN (monitored at m/z 59), PPN (m/z 73), and PiBN (m/z 87), respectively. The photo source was found to generate the three PANs in high yield. CIMS response factors derived using the photo source and TD-CRDS were identical to those derived from synthetic standards for PAN and PPN; hence, the photochemical PAN and PPN sources may be used to calibrate TD-CIMS (against TD-CRDS). For PiBN, the response factor derived using the photo source was 60% larger than that derived using the synthetic standard, limiting its use to deliver a calibrated stream of PiBN.► A photochemical source for generation of PPN and PIBN has been developed. ► The source output was calibrated against TD-CRDS. ► The calibrated source output was used to calibrate a TD-CIMS.
Keywords: Peroxycarboxylic nitric anhydrides (PAN); Peroxypropionic nitric anhydride (PPN); Peroxyisobutanoic nitric anhydride (PiBN); In situ photolysis source; Thermal dissociation chemical ionization mass spectrometry (TD-CIMS); Thermal dissociation cavity ring-down spectroscopy (TD-CRDS); Calibration;

Atmospheric ammonia and particulate ammonium from agricultural sources in the North China Plain by Jianlin Shen; Xuejun Liu; Ying Zhang; Andreas Fangmeier; Keith Goulding; Fusuo Zhang (5033-5041).
Atmospheric ammonia (NH3) and particulate ammonium (NH4 +) were measured using passive samplers and particulate samplers at four rural and two suburban sites in the North China Plain (NCP) from August 2006 to September 2009. The annual mean concentrations of NH3 and NH4 + in PM10 across the sites were 15.6 and 12.4 μg m−3, respectively. Higher concentrations of NH3 and NH4 + were found at the rural sites compared with the suburban sites. NH3 concentrations were highest in summer and lowest in winter, showing positive correlations with N fertilizer application rates and temperature in each season. Particulate NH4 + showed significant positive correlations with particulate SO4 2− and NO3 at the six sites. The annual mean concentrations of secondary inorganic particles (sum of NH4 +, SO4 2− and NO3 ) accounted for 26.1–41.3% of the PM10 concentration across all sites. The formation of inorganic NH4 + particles was limited mainly by the availability of H2SO4 and HNO3 and partly by NH3. The total NHx deposition in the NCP averaged 43.5 kg N ha−1 yr−1, accounting for 84.1% of the mean NH3 emission intensity. The serious particulate NH4 + pollution and high NHx deposition suggest the urgency of reducing NH3 emission from agricultural sources in the NCP.► Very high NH3 and particulate NH4 + concentrations were found in NCP. ► NH3 and particle NH4 + concentrations showed distinct spatio-temporal variations. ► Reducing NH3 loss from agriculture is key to improving air quality in NCP. ► NHx dry and wet deposition (44 kg N ha−1 yr−1) is a nutrient source in NCP.
Keywords: Ammonia emission; Secondary particle; PM10; Nitrogen deposition;

Wet deposition loadings of organic contaminants to Lake Ontario: Assessing the influence of precipitation from urban and rural sites by Lisa Melymuk; Matthew Robson; Miriam L. Diamond; Lisa E. Bradley; Sean Backus (5042-5049).
Wet deposition to Lake Ontario has been examined through a comparison of concentrations of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and brominated flame retardants (BFRs) in precipitation at three sites on the north shore of Lake Ontario: one rural, one suburban, and one urban site. Concentrations of ΣPAHs, BFRs, ΣPCBs, Σchlordanes and γ-HCH in precipitation are highest at the urban site, while concentrations of other OCPs were similar across all three sites. Loadings via wet deposition range from 0.42 kg year−1 for Σchlordanes to 1900 kg year−1 for ΣPAHs. The distribution of concentrations reflects the use/emission pattern of the persistent organic pollutants (POPs), and indicates that concentrations in precipitation are predominantly the result of local sources rather than long-range transport from other regions. While elevated urban concentrations increase wet deposition in the urban region itself, this influence decreases rapidly downwind of the urban area. Chemical loads in precipitation from the highly urbanized regions bordering the Great Lakes are estimated to increase wet deposition loadings to lake areas adjacent to the urban areas. Estimates of annual wet deposition loadings of POPs to Lake Ontario indicate that when considering the influence of elevated loadings from Toronto, loadings via precipitation are 2.5%–42% higher depending on the compound, with the greatest relative increase in loadings resulting from PCBs and Σchlordanes.► Wet-only deposition of organic compounds to Lake Ontario has been examined. ► Three sites representing one rural, one suburban, and one urban site were studied. ► Concentrations of ΣPAHs, BFRs, ΣPCBs, Σchlordanes and γ-HCH in precipitation are highest at the urban site. ► Loadings via wet deposition range from 0.42 kg year−1 for Σchlordanes to 1900 kg year−1 for ΣPAHs. ► Elevated urban concentrations increase wet deposition in the urban region, however this influence decreases rapidly downwind of the urban area.
Keywords: Precipitation; Persistent organic pollutants; Urban areas; Great Lakes;

Free amino acids in atmospheric particulate matter of Venice, Italy by Elena Barbaro; Roberta Zangrando; Ivo Moret; Carlo Barbante; Paolo Cescon; Andrea Gambaro (5050-5057).
The concentrations of free amino acids were determined in atmospheric particulate matter from the city of Venice (Italy) in order to better understand their origin. The analysis of aerosol samples was carried out via high-performance liquid chromatography coupled to a triple quadrupole tandem mass spectrometric detector (HPLC/ESI-MS/MS). The internal standard method was used and the analytical procedure was validated by evaluating the trueness, the precision, the recovery, the detection and the quantification limits.The particulate matter was collected using quartz fiber filters and extracted in methanol; after filtration the extract was directly analyzed. Forty samples were collected from April to October 2007 and the average concentrations of free amino acids in the aerosol were: alanine 35.6 pmol m−3, aspartic acid 31.1 pmol m−3, glycine 30.1 pmol m−3, glutamic acid 32.5 pmol m−3, isoleucine 2.4 pmol m−3, leucine 2.7 pmol m−3, methionine, cystine and 3-hydroxy-proline below the limit of detection, phenylalanine 2.8 pmol m−3, proline 43.3 pmol m−3, serine 8.6 pmol m−3, threonine 2.8 pmol m−3, tyrosine 1.7 pmolm−3, valine 3.8 pmol m−3, asparagine 70.2 pmol m−3, glutamine 38.0 pmol m−3, 4-hydroxy-proline 2.5 pmol m−3, methionine sulfoxide 1.1 pmol m−3, and methionine sulfone 0.1 pmol m−3. The total average concentration of these free amino acids in aerosol samples of Venice Lagoon was 334 pmol m−3. The temporal evolution and multivariate analysis indicated the photochemical origin of 4-hydroxy-proline and methionine sulfoxide and for other compounds an origin further away from the site of sampling, presumably reflecting transport from terrestrial sources.► Determination of amino acids in atmospheric aerosol of Venice by HPLC/ESI-MS/MS. ► To confirm the photochemical origin of MetSO and MetSO2. ► To link the presence of 4-Hyp to the oxidation of Pro. ► To hypothesize the main sources in Venice of amino acids. ► To hypothesize that amino acids such as Ala and Gly come from distant sources.
Keywords: Amino acids; Aerosol; Venice; HPLC-MS/MS;

Chemical characteristics of spring rainwater of Xi’an city, NW China by Xinwei Lu; Loretta Y. Li; Nan Li; Guang Yang; Dacheng Luo; Jinghui Chen (5058-5063).
A comprehensive study on the chemical composition of spring rainwater was carried out in Xi’an, northwestern China. All samples were analyzed for pH, electrical conductivity and main ions (SO4 2−, NO3 , Cl, F, Ca2+, Mg2+, K+, Na+ and NH4 +). The pH varied from 5.14 to 7.45, with a volume-weighted mean pH of 6.64. The volume-weighted mean equivalent concentration of rainwater components followed the order SO4 2−  > Ca2+  > NH4 +  > NO3  > Cl  > Mg2+  > Na+  > F  > K+. The dominant ions, SO4 2−, Ca2+, NH4 + and NO3 , accounted for 88% of the total ions. Significant positive correlation of SO4 2−, NO3 with Ca2+ and NH4 + and the calculated neutralization factors show that Ca2+ and NH4 + are the main neutralizing constituents. Sources of major ions were assessed based on the enrichment factor. Ca2+, K+ and Mg2+ mainly originated from crust, whereas SO4 2− and NO3 are mostly attributable to anthropogenic sources. The major likely source of NH4 + was agricultural activities.► SO4 2−, Ca2+, NH4 + and NO3 are the predominant ions in the rainwater of Xi’an. ► The pH value of rainwater in Xi’an is 6.64 which neutralized by Ca2+ and NH4 +. ► About 21% of acidy of Xi’an rainwater was due to NO3 and 79% due to SO4 2−. ► Total ions concentration shows atmospheric environment of Xi’an is severe polluted. ► The major ions of Xi’an rainwater originated from anthropogenic and soil sources.
Keywords: Rainwater; Chemical composition; Neutralization factor; Correlation analysis; Enrichment factor;

New stomatal flux-based critical levels for ozone effects on vegetation by Gina Mills; Håkan Pleijel; Sabine Braun; Patrick Büker; Victoria Bermejo; Esperanza Calvo; Helena Danielsson; Lisa Emberson; Ignacio González Fernández; Ludger Grünhage; Harry Harmens; Felicity Hayes; Per-Erik Karlsson; David Simpson (5064-5068).
The critical levels for ozone effects on vegetation have been reviewed and revised by the LRTAP Convention. Eight new or revised critical levels based on the accumulated stomatal flux of ozone (POD Y , the Phytotoxic Ozone Dose above a threshold flux of Y nmol m−2 PLA s−1, where PLA is the projected leaf area) have been agreed. For each receptor, data were combined from experiments conducted under naturally fluctuating environmental conditions in 2–4 countries, resulting in linear dose–response relationships with response variables specific to each receptor (r 2 = 0.49–0.87, p < 0.001 for all). For crops, critical levels were derived for effects on wheat (grain yield, grain mass, and protein yield), potato (tuber yield) and tomato (fruit yield). For forest trees, critical levels were derived for effects on changes in annual increment in whole tree biomass for beech and birch, and Norway spruce. For (semi-)natural vegetation, the critical level for effects on productive and high conservation value perennial grasslands was based on effects on important component species of the genus Trifolium (clover species). These critical levels can be used to assess protection against the damaging effects of ozone on food security, important ecosystem services provided by forest trees (roundwood production, C sequestration, soil stability and flood prevention) and the vitality of pasture.
Keywords: Ozone; Flux; Critical levels; Food security; Ecosystem services; Trees; Grasslands;