Atmospheric Environment (v.43, #19)

Emissions of isoprene, monoterpene and short-chained carbonyl compounds from Eucalyptus spp. in southern Australia by Anthony J. Winters; Mark A. Adams; Tim M. Bleby; Heinz Rennenberg; Dominik Steigner; Rainer Steinbrecher; Jürgen Kreuzwieser (3035-3043).
Eucalypts are among the highest emitters of biogenic volatile organic compounds, yet there is relatively little data available from field studies of this genus. Emissions of isoprene, monoterpenes and the short-chained carbonyls formaldehyde, acetaldehyde and acetone were determined from four species (Eucalyptus camaldulensis, Eucalyptus globulus, Eucalyptus grandis, and Eucalytpus viminalis) in Australia. A smaller comparative study was conducted on E. camaldulensis in south-eastern Australia. Carbonyl emissions, reported here for the first time from eucalypts, were generally comparable with rates reported for other species, with diurnal emissions peaking at about 4, 75 and 34 nmol m−2 min−1 for acetone, formaldehyde and acetaldehyde respectively. There was wide variation in diurnal isoprene and monoterpene emissions between species, but under standard conditions, isoprene emissions were much lower than previous reports. Conversely, standard emission rates of monoterpenes were as much as six times greater than previous reports for some species. Emission of each carbonyl was correlated with its ambient concentration across different species, but more weakly related to temperature. Acetaldehyde emission in particular was significantly correlated with transpiration, but not with sap flow or with ethanol concentrations in xylem sap, suggesting fermentation within the leaf and stomatal conductance are primary controlling processes. Differences in acetaldehyde exchange velocities between sites, in addition to transpiration differences, suggest stomata may indeed exert long term emission regulation, in contrast to compounds for which no biological sink exists.
Keywords: Volatile organic compounds; VOC emission; Eucalyptus; Isoprene; Monoterpene; Acetaldehyde; Acetone; Formaldehyde; Carbonyl;

Influence of transport and trends in atmospheric CO2 at Lampedusa by F. Artuso; P. Chamard; S. Piacentino; D.M. Sferlazzo; L. De Silvestri; A. di Sarra; D. Meloni; F. Monteleone (3044-3051).
The study of the CO2 15-year records at Lampedusa (35° 31′N, 12° 37′E) is presented in this work. Short- and long-term CO2 variability has been investigated. No significant diurnal variations are observable thus remarking the background character and representativeness of the observation site. The CO2 long-term trend shows a mean linear growth rate (GR) of 1.9 ppm yr−1. The periodic behaviour of the time series has been analysed and the mean seasonal cycle amplitude has been found to be 8.72 ppm. The seasonal cycle amplitude shows a marked interannual variability. The lowest value of the seasonal cycle amplitude has been detected in 2003, in concomitance with the strong anomalous heat wave recorded in Europe. CO2 GR behaviour has been related to global processes such as El Niño Southern Oscillation (ENSO) and global temperature (Tg). The influence of ENSO event on GR is remarkable only during 1998. CO2 GR curve shows peaks in the periods 1995, 2001 and 2005 (1.9, 3.7, 3.2 ppm yr−1 respectively) that are characterized by high Tg values and by intense biomass burning events. The anomalous decrease in the GR during the warm 2003 has been attributed to changes in the atmospheric circulation regime. Evaluation of the influence of transport on CO2 variability has been carried out using backward air-mass trajectory analysis and highlights the effect of the regional distribution of sources and sinks. The industrial activities and forests located in the Eastern European and Russian sector strongly affect the CO2 mixing ratio. The CO2 content of air-masses originating from this region is influenced in summertime by the high efficiency of the vegetation sink while in the winter period prevails the effect of industrial emissions.
Keywords: Atmospheric CO2; Interannual variability; Seasonal cycle amplitude; Backward trajectory;

Evaluation of the European population intake fractions for European and Finnish anthropogenic primary fine particulate matter emissions by Marko Tainio; Mikhail Sofiev; Mika Hujo; Jouni T. Tuomisto; Miranda Loh; Matti J. Jantunen; Ari Karppinen; Leena Kangas; Niko Karvosenoja; Kaarle Kupiainen; Petri Porvari; Jaakko Kukkonen (3052-3059).
The intake fraction (iF) has been defined as the integrated incremental intake of a pollutant released from a source category or region summed over all exposed individuals. In this study we evaluated the iFs in the population of Europe for emissions of anthropogenic primary fine particulate matter (PM2.5) from sources in Europe, with a more detailed analysis of the iF from Finnish sources. Parameters for calculating the iFs include the emission strengths, the predicted atmospheric concentrations, European population data, and the average breathing rate per person. Emissions for the whole of Europe and Finland were based on the inventories of the European Monitoring and Evaluation Programme (EMEP) and the Finnish Regional Emission Scenario (FRES) model, respectively. The atmospheric dispersion of primary PM2.5 was computed using the regional-scale dispersion model SILAM. The iFs from Finnish sources were also computed separately for six emission source categories. The iFs corresponding to the primary PM2.5 emissions from the European countries for the whole population of Europe were generally highest for the densely populated Western European countries, second highest for the Eastern and Southern European countries, and lowest for the Northern European and Baltic countries. For the entire European population, the iF values varied from the lowest value of 0.31 per million for emissions from Cyprus, to the highest value of 4.42 per million for emissions from Belgium. These results depend on the regional distribution of the population and the prevailing long-term meteorological conditions. Regarding Finnish primary PM2.5 emissions, the iF was highest for traffic emissions (0.68 per million) and lowest for major power plant emissions (0.50 per million). The results provide new information that can be used to find the most cost-efficient emission abatement strategies and policies.
Keywords: Intake fraction; Fine particulate matter; PM2.5; Exposure; Dispersion model;

In 2007, the European limit values for annual average nitrogen dioxide (NO2) concentration and for daily average particulate matter (PM10) concentration were exceeded along motorways and city streets in the Netherlands. While the road length along which the exceedance occurred is uncertain, model calculations show that the NO2 concentration was likely to have been exceeded (chance >66%) along about 300 km and PM10 concentration along about 75 km. In addition, the limit values were exceeded ‘about as likely as not’ (chance 33–66%) along a total of 1000 km for NO2 and 1600 km for PM10. PM10 and NO2 concentrations must be below the limit values everywhere in Europe, ultimately by 2011 and 2015, respectively. Since estimates of future local concentrations have an uncertainty of about 15–20%, no absolute statements can be made whether concentrations will be below the limit values within the specified time. Model calculations accounting for the effects of current and proposed national and European legislation, and using average meteorology for large-scale and local traffic contributions show strong decreases in likely limit value exceedances in the Netherlands. However, limit value exceedances are still possible (chance >33%) along about 350 km for PM10 by 2011, and about 150 km for NO2, by 2015. These possible exceedances depend not only on the uncertainties and on national and European policies and their effectiveness, but also on contributions by specific additional local measures. The Netherlands Government has proposed a plan, which includes local measures to meet the limit values everywhere, in time. Although not assessed here due to their specific character, such local measures could reduce exceedances. As the effects of local measures and estimates of concentrations are uncertain, continuous monitoring – possibly together with additional measures – will be needed to adhere to the limit values.
Keywords: Air quality; Nitrogen dioxide; Particulate matter; Modelling; Uncertainty;

Study of metal concentrations in the environment near diesel transport routes by Chung-Yih Kuo; Jing-Ya Wang; Shih-Hsien Chang; Mei-Chun Chen (3070-3076).
In recent years, a river-dredging project has been executed in Nantou, Taiwan. A large number of diesel vehicles carrying gravel and sand shuttle back and forth on the main traffic roads (Tai-16 and Tai-21). The purpose of this study is to figure out the levels of metals contributed by those vehicles to the surrounding environment. Eight stations along the roadside of diesel transport routes were selected as exposure sites, while a small village located about 9 km away from the diesel transport routes was selected as the control site. The mass concentrations of coarse and fine particulate matter indicated that contributions from traffic fleets resulted in a higher percentage of coarse particulate matter in the ambient air at exposure sites in comparison with that at control site. Significantly higher values of EC (elemental carbon) concentrations and ratios of EC/OC (organic carbon) at exposure sites indicate that diesel vehicles at exposure sites contributed a greater amount of pollutants than gasoline vehicles. Exposure site concentrations for all metals measured (Fe, Al, Mn, Pb, Zn, Cu, Ni, Mo and As) for fine and coarse particulate matter were all higher than those at the control site. Recorded levels of metal contents in road dust and riverside soil near Tai-16 and Tai-21 showed that while the traffic fleet did not increase the metal contents of crustal elements in the road dust, it did significantly increase the metal contents of traffic-related elements. Enrichment factors (EFs) were calculated with respect to road dust (EFroad) and with respect to the samples of riverside soil (EFriver). Among these metals, Mo was the most highly-enriched metal. The extremely high EFriver value (4300) of Mo indicates that these stations were highly polluted by diesel emission. Whereas the significantly high EFroad value (810) of Mo implies that a considerable of Mo was emitted from tailpipe of diesel vehicles.
Keywords: Metals; Diesel emission; Resuspension; Tailpipe emission;

Climate forcing by the on-road transportation and power generation sectors by Nadine Unger; Drew T. Shindell; James S. Wang (3077-3085).
The on-road transportation (ORT) and power generation (PG) sectors are major contributors to carbon dioxide (CO2) emissions and a host of short-lived radiatively-active air pollutants, including tropospheric ozone and fine aerosol particles, that exert complex influences on global climate. Effective mitigation of global climate change necessitates action in these sectors for which technology change options exist or are being developed. Most assessments of possible energy change options to date have neglected non-CO2 air pollutant impacts on radiative forcing (RF). In a multi-pollutant approach, we apply a global atmospheric composition-climate model to quantify the total RF from the global and United States (U.S.) ORT and PG sectors. We assess the RF for 2 time horizons: 20- and 100-year that are relevant for understanding near-term and longer-term impacts of climate change, respectively. ORT is a key target sector to mitigate global climate change because the net non-CO2 RF is positive and acts to enhance considerably the CO2 warming impacts. We perform further sensitivity studies to assess the RF impacts of a potential major technology shift that would reduce ORT emissions by 50% with the replacement energy supplied either by a clean zero-emissions source (S1) or by the PG sector, which results in an estimated 20% penalty increase in emissions from this sector (S2). We examine cases where the technology shift is applied globally and in the U.S. only. The resultant RF relative to the present day control is negative (cooling) in all cases for both S1 and S2 scenarios, global and U.S. emissions, and 20- and 100-year time horizons. The net non-CO2 RF is always important relative to the CO2 RF and outweighs the CO2 RF response in the S2 scenario for both time horizons. Assessment of the full impacts of technology and policy strategies designed to mitigate global climate change must consider the climate effects of ozone and fine aerosol particles.
Keywords: Radiative forcing; Ozone; Aerosols; Transportation; Electric power; PHEV;

Growing season methane budget of an Inner Mongolian steppe by Chunyan Liu; Jirko Holst; Zhisheng Yao; Nicolas Brüggemann; Klaus Butterbach-Bahl; Shenghui Han; Xingguo Han; Bart Tas; Andreas Susenbeth; Xunhua Zheng (3086-3095).
We present a methane (CH4) budget for the area of the Baiyinxile Livestock Farm, which comprises approximately 1/3 of the Xilin river catchment in central Inner Mongolia, P.R. China. The budget calculations comprise the contributions of natural sources and sinks as well as sources related to the main land-use in this region (non-nomadic pastoralism) during the growing season (May–September). We identified as important CH4 sources floodplains (mean 1.55 ± 0.97 mg CH4–C m−2 h−1) and domestic ruminants, which are mainly sheep in this area. Within the floodplain significant differences between investigated positions were detected, whereby only positions close-by the river or bayous emitted large amounts of CH4 (mean up to 6.21 ± 1.83 mg CH4–C m−2 h−1). Further CH4 sources were sheepfolds (0.08–0.91 mg CH4–C m−2 h−1) and pasture faeces (1.34 ± 0.22 mg CH4–C g−1 faeces dry weight), but they did not play a significant role for the CH4 budget. In contrast, dung heaps were not a net source of CH4 (0.0 ± 0.2 for an old and 0.0 ± 0.3 μg CH4–C kg−1 h−1 for a new dung heap). Trace gas measurements along two landscape transects (volcano, hill slope) revealed expectedly a mean CH4 uptake (volcano: 76.5 ± 4.3; hill: 28.3 ± 5.3 μg CH4–C m−2 h−1), which is typical for the aerobic soils in this and other steppe ecosystems. The observed fluxes were rarely influenced by topography.The CH4 emissions from the floodplain and the sheep were not compensated by the CH4 oxidation of aerobic steppe soils and thus, this managed semi-arid grassland did not serve as a terrestrial sink, but as a source for this globally important greenhouse gas. The source strength amounted to 1.5–3.6 kg CH4–C ha−1 during the growing season, corresponding to 3.5–8.7 kg C ha−1 yr−1.
Keywords: Methane; MAGIM; Grazing; Sheepfold; Floodplain;

Biomass burning smoke constituents are worthy of concern due to its influence on climate and human health. The organic constituents and distributions of molecular tracers emitted from burning smoke of six natural vegetations including monsoon evergreen broad-leaf trees and shrubs in South China were determined in this study. The gas and particle samples were collected and analyzed by gas chromatography–mass spectrometry. The major organic components in these smoke samples are methoxyphenols from lignin and saccharides from cellulose. Polycyclic aromatic hydrocarbons (PAHs) are also present as minor constituents. Furanose, pyranose and their dianhydrides are the first reported in the biomass burning smoke. Some unique biomarkers were detected in this study which may be useful as specific tracers. The corresponding tracer/OC ratios are used as indicators for the two types of biomass burning. U/R (1.06–1.72) in the smoke samples may be used as parameters to distinguish broad-leaf trees and shrubs from fossil fuel. Other useful diagnostic ratios such as methylphenanthrene to phenanthrene (MPhe/Phe), phenanthrene to phenanthrene plus anthracene (Phe/(Phe + Ant)) and fluoranthene to fluoranthene plus pyrene (Flu/(Flu + Pyr)) and octadecenoic acid/OC are also identified in this study. These results are useful in efforts to better understand the emission characterization of biomass burning in South China and the contribution of regional biomass burning to global climate change.
Keywords: Biomass burning; Broad-leaf trees; Shrubs; Natural vegetations; Molecular tracers; China;

The stable-carbon kinetic isotope effects (KIEs) for the gas-phase reactions of isoprene, methacrolein (MACR), and methyl vinyl ketone (MVK) with OH radicals were studied in a 25 L reaction chamber at (298 ± 2) K and ambient pressure. The time dependence of both the stable-carbon isotope ratios and the concentrations was determined using a gas-chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The volatile organic compounds (VOCs) used in the KIE experiments had natural-abundance isotopic composition thus KIE data obtained from these experiments can be directly applied to atmospheric studies of isoprene chemistry. All 12C/13/C KIE values are reported as ɛ values, where ɛ = (KIE − 1) × 1000‰, and KIE = k 12/k 13. The following average stable-carbon KIEs were obtained: (6.56 ± 0.12)‰ (isoprene), (6.47 ± 0.27)‰ (MACR), and (7.58 ± 0.47)‰ (MVK). The measured KIEs all agree within uncertainty to an inverse molecular mass (MM) dependence of OH ɛ(‰) = (487 ± 18)MM−1, which was derived from two previous studies [J. Geophys. Res. 2000, 105, 29329–29346; J. Phys. Chem. A 2004, 108, 11537–11544]. Upon adding the isoprene, MACR, and MVK OH ɛ values from this study, the inverse MM dependence changes only marginally to OH ɛ(‰) = (485 ± 14)MM−1. The addition of these isoprene OH ɛ values to a recently measured set of ɛ O 3 values in an analogous study [Atmos. Environ. 2008, 42, 8728–8737] allows for estimates of the average change in the 12C/13C ratio due to processing in the troposphere.
Keywords: Kinetic isotope effect; Isoprene; Methacrolein; Methyl vinyl ketone; GC-IRMS;

City ventilation of Hong Kong at no-wind conditions by Lina Yang; Yuguo Li (3111-3121).
We hypothesize that city ventilation due to both thermally-driven mountain slope flows and building surface flows is important in removing ambient airborne pollutants in the high-rise dense city Hong Kong at no-wind conditions. Both spatial and temporal urban surface temperature profiles are an important boundary condition for studying city ventilation by thermal buoyancy. Field measurements were carried out to investigate the diurnal thermal behavior of urban surfaces (mountain slopes, and building exterior walls and roofs) in Hong Kong by using the infrared thermography. The maximum urban surface temperature was measured in the early noon hours (14:00–15:00 h) and the minimum temperature was observed just before sunrise (5:00 h). The vertical surface temperature of the building exterior wall was found to increase with height at daytime and the opposite occurred at nighttime. The solar radiation and the physical properties of the various urban surfaces were found to be important factors affecting the surface thermal behaviors. The temperature difference between the measured maximum and minimum surface temperatures of the four selected exterior walls can be at the highest of 16.7 °C in the early afternoon hours (15:00 h). Based on the measured surface temperatures, the ventilation rate due to thermal buoyancy-induced wall surface flows of buildings and mountain slope winds were estimated through an integral analysis of the natural convection flow over a flat surface. At no-wind conditions, the total air change rate by the building wall flows (2–4 ACH) was found to be 2–4 times greater than that by the slope flows due to mountain surface (1 ACH) due to larger building exterior surface areas and temperature differences with surrounding air. The results provide useful insights into the ventilation of a high-rise dense city at no-wind conditions.
Keywords: Surface temperature; Thermal buoyancy; City ventilation rate; Wall flow; Slope flow;

Sensitivity of surface characteristics on the simulation of wind-blown-dust source in North America by S.H. Park; S.L. Gong; W. Gong; P.A. Makar; M.D. Moran; C.A. Stroud; J. Zhang (3122-3129).
Recently, a wind-blown-dust-emission module has been built based on a state-of-the-art wind erosion theory and evaluated in a regional air-quality model to simulate a North American dust storm episode in April 2001 (see Park, S.H., Gong, S.L., Zhao, T.L., Vet, R.J., Bouchet, V.S., Gong, W., Makar, P.A., Moran, M.D., Stroud, C., Zhang, J. 2007. Simulation of entrainment and transport of dust particles within North America in April 2001 (“Red Dust episode”). J. Geophys. Res. 112, D20209, doi:10.1029/2007JD008443). A satisfactorily detailed assessment of that module, however, was not possible because of a lack of information on some module inputs, especially soil moisture content. In this paper, the wind-blown-dust emission was evaluated for two additional dust storms using improved soil moisture inputs. The surface characteristics of the wind-blown-dust source areas in southwestern North America were also investigated, focusing on their implications for wind-blown-dust emissions. The improved soil moisture inputs enabled the sensitivity of other important surface characteristics, the soil grain size distribution and the land-cover, to dust emission to be investigated with more confidence. Simulations of the two 2003 dust storm episodes suggested that wind-blown-dust emissions from the desert areas in southwestern North America are dominated by emissions from dry playas covered with accumulated alluvial deposits whose particle size is much smaller than usual desert sands. As well, the source areas in the northwestern Texas region were indicated to be not desert but rather agricultural lands that were “activated” as a wind-blown-dust sources after harvest. This finding calls for revisions to the current wind-blown-dust-emission module, in which “desert” is designated to be the only land-cover category that can emit wind-blown dust.
Keywords: Soil dust; Simulation; Surface parameters; Dust sources; Southwestern North America;

The effect of clouds on total and UV-B irradiance in Córdoba, Argentina, was studied employing the TUV 4.1 model and measurements obtained with YES UVB-1 and YES TSP-700 radiometers, and a spectral radiometer Ocean Optics USB-4000. The experimental measurements were selected from a 10 years dataset (1999–2008). Clouds were classified by direct observation as cirrus, cumulus, and stratocumulus. The broadband Cloud Modification Factors (CMFs) have been calculated in the range of the total and the UV-B radiation for these types of clouds. The relations between them were analyzed for a significant number of days. The broadband CMF values range from around 0.1 up to 1.25, depending on the wavelength interval and on the cloud type. The CMFUVB versus CMFT plots for different clouds have shown good adjustments and significant differences, which allows the distinction between them.Stratocumulus clouds show large attenuations and a linear relation with larger slopes as the solar zenith angle (SZA) increases. For this type of clouds an average slope of (1.0 ± 0.2) was found. The relation between the CMF for cumulus clouds is linear with an average slope of (0.61 ± 0.01). No dependence with the SZA was observed. Cirrus clouds plots show an exponential behavior with fit parameters equal to (0.48 ± 0.08) and (0.68 ± 0.15). However, when small SZA intervals are analyzed a linear relation is found. When the relations between the CMF were similar (cumulus and cirrus), the spectral variation in the UV range (320–420 nm) of a modified CMF (CMFm) was used to distinguish them. Hence, the spectral differences among the three types of clouds have been also analyzed for several days and SZA. Here, it was found that the effect of cirrus is essentially wavelength independent while cumulus and stratocumulus clouds show exponential decay relations but with different ordinates.In the analyzed relations the microphysical properties of the clouds seem to determine its behavior while the optical thickness leads to the different degrees of attenuation.The results obtained in this work are in agreement with those found for other authors.
Keywords: Clouds properties; Cloud modification factor; Córdoba; Radiative transfer model; Irradiance measurements;

Anthropogenic contribution of magnetic particulates in urban roadside dust by Wonnyon Kim; Seong-Jae Doh; Yongjae Yu (3137-3144).
Environmental magnetism parameters have been optimized as qualitative proxy indicators of the distribution of anthropogenic particulates, heavy metals and/or organic materials. In the present study, we propose a quantitative magnetic proxy which is suitable for the monitoring of spatial and temporal pollution patterns in urban areas. A total of 1353 roadside dust samples were collected from Seoul, Korea for 13 months. Thermomagnetic data and intensive electron microscopy identified a predominance of carbon-bearing iron-oxides, indicating that anthropogenic particulates mostly originated from fossil fuel combustions. To quantify anthropogenic particulates, an apparent magnetic concentration [ AMC Fe 3 O 4 = observed saturation magnetization ( M s ) / M s of Fe 3 O 4 ( = 92.36 Am 2 kg − 1 ) ] was calculated. AMC Fe 3 O 4 showed distinctive spatial and seasonal dependences: highest in industrial areas and lowest in park areas; and maximum in winter and minimum in summer. Seasonal mapping using AMC Fe 3 O 4 illustrated that industries in southwestern Seoul were the major pollution source. In addition, dominant westerly winds possibly transported pollutants along topographically lower areas in Seoul.
Keywords: Apparent magnetic concentration; Carbon-bearing iron-oxide; Environmental pollution; Magnetic pollution map;

Speciated mercury in size-fractionated particles in Shanghai ambient air by Guangli Xiu; Ji Cai; Wenying Zhang; Danian Zhang; Andreas Büeler; Shuncheng Lee; Yan Shen; Lihang Xu; Xuejuan Huang; Ping Zhang (3145-3154).
Size-fractionated particles were collected at two sites from July 2004 to April 2006 in Shanghai. The mercury in particles was extracted and divided operationally into four species: exchangeable particulate mercury (EXPM), HCl-soluble particulate mercury (HPM), elemental particulate mercury (EPM) and residual particulate mercury. The total particulate Hg concentration during the study period ranged from 0.07 ng m−3 to 1.45 ng m−3 with the average 0.56 ± 0.22 ng m−3 at site 1, while 0.20 ng m−3–0.47 ng m−3 with the average 0.33 ± 0.09 ng m−3 at site 2, which is far higher than some foreign cities and comparable to some cities with heavy air pollution in China. The Hg mass content also displayed evident size distribution, with higher value in PM1.6–3.7, somewhat higher or lower than the source profile. EXAM was only found in the summer, HPM have higher percentage in summer and fall rather than in winter and spring. The different mercury species showed different correlation to temperature, relative humidity, wind speed. HPM positively depends on temperature at both sites which implies the importance of mercury transformation on particles. In foggy days TPM increased greatly, but HPM didn't vary greatly as anticipated. Instead, RPM gained a distinguished increase. It demonstrated that aqueous reaction and complex heterogenic reactions in droplet might happen in acidic environment. The correlation of mercury with other pollutants including SO2, NO2, CO and PM10 varies with the different mercury forms. Hybrid single-particle lagrangian integrated trajectories (HYSPLIT) model was used to back trace air mass at different representative days and results indicated that transportation from Huabei Plain will increase mercury concentration in winter and fall to some extent. The possible existing compounds and their atmospheric behavior of HPM, EPM and RPM were calculated and the compared to analyze its implication on atmospheric mercury cycle.
Keywords: Particulate mercury; Speciation analysis; HYSPLIT; Mercury; Shanghai;