Study on dissolved organic carbon in precipitation in Northern China

Dissolved organic carbon (DOC) was measured in 483 precipitation samples collected at 10 sites in Northern China from December 2007 to November 2008. The annual volume-weighted mean (VWM) concentrations and wet deposition fluxes of DOC for 10 sites ranged from 2.4 to 3.9 mg C/L and 1.4 to 2.7 g C m^?2 yr^?1, respectively. The proportion of DOC to total organic carbon (TOC) was 79% on average, suggesting that a significant fraction of TOC was present as insoluble particulate organic carbon. Due to intensive domestic coal use for house heating and smaller dilution of scavenged organic carbon, higher VWM concentrations of DOC were observed during winter and spring than during summer and autumn. When precipitation events were classified via air mass back-trajectories, the mixed trajectories from SE and NW always corresponded to significantly higher DOC than those from SE or NW alone, coinciding with the centre of a low pressure system moved eastward and the wind direction changed from southeast to northwest. The results also showed that each site had a similar seasonal variation for DOC wet deposition flux. The largest flux occurred during the rainy season, and the lowest flux appeared during winter months. The product of the TC/DOC ratio and the DOC flux yielded an average TC wet deposition flux of 3.2 g C m^?2 yr^?1 in Northern China, accounting for 8.6% and 22% of the carbon sink magnitude (37 g C m^?2 yr^?1) in terrestrial ecosystems and anthropogenic carbon emissions (14 g C m^?2 yr^?1), respectively. This indicates that atmospheric wet deposition of TC is a significant carbon flux that cannot be neglected in regional models of the carbon cycle, and should be considered along with dry deposition in the removal mechanism for carbon from regional atmosphere.     

Reducing carbonyl emissions from a heavy-duty diesel engine at US transient cycle test by use of paraffinic/biodiesel blends

Formaldehyde and acetaldehyde are toxic carcinogens so their reductions in diesel-engine emissions are desirable. This study investigated emissions of carbonyl compounds (CBCs) from an HDDE (heavy-duty diesel engine) at US transient cycle test, using five test fuels: premium diesel fuel (D100), P100 (100% palm-biodiesel), P20 (20% palm-biodiesel + 80% premium diesel fuel), PF80P20 (80% paraffinic fuel + 20% palm-biodiesel), and PF95P05 (95% paraffinic fuel + 5% palm-biodiesel). Experimental results indicate that formaldehyde was the major carbonyl in the exhaust, accounting for 70.1–76.2% of total CBC concentrations for all test fuels. In comparison with D100 (172 mg BHP^?1 h^?1), the reductions of formaldehyde and acetaldehyde emission factor for P100, P20, PF80P20, and PF95P05 were (?16.8%, ?61.8%), (?10.0%, ?39.0%), (21.3%, 1.10%), and (31.1%, 19.5%), respectively. Using P100 and P20 instead of D100 in the HDDE increased CBC concentrations by 14.5% and 3.28%, respectively, but using PF80P20 and PF95P05 significantly reduced CBC concentrations by 30.3% and 23.7%, respectively. Using P100 and P20 instead of D100 (2867 ton yr^?1) in the HDDE increased CBC emissions by 240 and 224 ton yr^?1, respectively, but using PF80P20, and PF95P05 instead of D100 in the HDDE decreased CBC emissions by 711 and 899 ton yr^?1, respectively. The above results indicate that the wide usage of paraffinic–palmbiodiesel blends as alternative fuels could protect the environment.     

Global scale emission and distribution of sea-spray aerosol: Sea-salt and organic enrichment

The chemical composition of marine aerosols as a function of their size is an important parameter for the evaluation of their impact on the global climate system. In this work we model fine particle organic matter emitted by sea spray processes and its influence on the aerosol chemical properties at the global scale using the off-line global Chemistry-Transport Model TM5. TM5 is coupled to a microphysical aerosol dynamics model providing size resolved information on particle masses and numbers. The mass of the emitted sea spray particles is partitioned between water insoluble organic matter (WIOM) and sea salt components in the accumulation mode using a function that relates the emitted organic fraction to the surface ocean chlorophyll-a concentrations. The global emission in the sub-micron size range of organic matter by sea spray process is 8.2 Tg yr^?1, compared to 24 Tg fine yr^?1 sea-salt emissions. When the marine sources are included, the concentrations of modelled primary particulate organic matter (POM) increase mainly over the oceans. The model predictions of WIOM and sea salt are evaluated against measurements carried out at Mace Head (Northern Hemisphere) and Amsterdam Island (Southern Hemisphere), showing that in clean marine conditions WIOM marine emissions contribute significantly to POM values.     

Simulation of global warming potential (GWP) from rice fields in the Tai-Lake region,China by coupling 1:50,000 soil database with DNDC model

Quantifying greenhouse gas (GHG) emissions from wetland ecosystems is a relatively new issue in global climate change studies. China has approximately 22% of the world's rice paddies and 38% of the world's rice production, which are crucial to accurately estimate the global warming potential (GWP) at regional scale. This paper reports an application of a biogeochemical model (DeNitrification and DeComposition or DNDC) for quantifying GWP from rice fields in the Tai-Lake region of China. For this application, DNDC is linked to a 1:50,000 soil database, which was derived from 1107 paddy soil profiles compiled during the Second National Soil Survey of China in the 1980–1990s. The simulated results show that the 2.34 Mha of paddy soil cultivated in rice–wheat rotation in the Tai-Lake region emitted about ?1.48 Tg C, 0.84 Tg N and 5.67 Tg C as CO₂, N₂O, and CH₄ respectively, with a cumulative GWP of 565 Tg CO₂ equivalent from 1982 to 2000. As for soil subgroups, the highest GWP (26,900 kg CO₂ equivalent ha^?1 yr^?1) was linked to gleyed paddy soils accounting for about 4.4% of the total area of paddy soils. The lowest GWP (5370 kg CO₂ equivalent ha^?1 yr^?1) was associated with submergenic paddy soils accounting for about 0.32% of the total area of paddy soils. The most common soil in the area was hydromorphic paddy soils, which accounted for about 53% of the total area of paddy soils with a GWP of 12,300 kg CO₂ equivalent ha^?1 yr^?1. On a regional basis, the annual averaged GWP in the polder, Tai-Lake plain, and alluvial plain soil regions was distinctly higher than that in the low mountainous and Hilly soil regions. As for administrative areas, the average annual GWP of counties in Shanghai city was high. Conversely, the average annual GWP of counties in Jiangsu province was low. The high variability in soil properties throughout the Tai-Lake region is important and affects the net greenhouse gas emissions. Therefore, the use of detailed soil data sets with high-resolution digital soil maps is essential to improve the accuracy of GWP estimates with process-based models at regional and national scales.     

Impacts of boundary layer mixing on pollutant vertical profiles in the lower troposphere: Implications to satellite remote sensing

Mixing in the planetary boundary layer (PBL) affects vertical distributions of air tracers in the lower troposphere. An accurate representation of PBL mixing is critical for chemical-transport models (CTMs) for applications sensitive to simulations of the vertical profiles of tracers. The full mixing assumption in the widely used global CTM GEOS-Chem has recently been supplemented with a non-local PBL scheme. This study analyzes the impact of the non-local scheme on model representation of PBL mixing, consequences for simulations of vertical profiles of air tracers and surface air pollution, and implications for model applications to the interpretation of data retrieved from satellite remote sensing. The non-local scheme significantly improves simulations of the vertical distributions for NO₂ and O₃, as evaluated using aircraft measurements in summer 2004. It also reduces model biases over the U.S. by more than 10 ppb for surface ozone concentrations at night and by 2–5 ppb for peak ozone in the afternoon, as evaluated using ground observations. The application to inverse modeling of anthropogenic NO_x emissions for East China using satellite retrievals of NO₂ from OMI and GOME-2 suggests that the full mixing assumption results in 3–14% differences in top–down emission budgets as compared to the non-local scheme. The top–down estimate combining the non-local scheme and the Lin et al. inverse modeling approach suggests a magnitude of 6.6 TgN yr^?1 for emissions of NO_x over East China in July 2008 and 8.0 TgN yr^?1 for January 2009, with the magnitude and seasonality in good agreement with bottom–up estimates.     

Effect of land-use change on CH4 and N2O emissions from freshwater marsh in Northeast China

The wetlands play an important role in global carbon and nitrogen storage, and they are also natural sources of greenhouse gases such as methane (CH₄) and nitrous oxide (N₂O). Land-use change is an important factor affecting the exchange of greenhouse gases between wetlands and the atmosphere. However, few studies have investigated the effect of land-use change on CH₄ and N₂O emissions from freshwater marsh in China. Therefore, a field study was carried out over a year to investigate the seasonal changes of the emissions of CH₄ and N₂O at three sites (Deyeuxia angustifolia marsh, dryland and rice field) in the Sanjiang Plain of Northeast China. Marsh was the source of CH₄ showing a distinct temporal variation. Maximum fluxes occurred in June and the highest value was 20.69 ± 2.57 mg CH₄ m^?2 h^?1. The seasonal change of N₂O fluxes from marsh was not obvious, consisted of a series of emission pulses. The marsh acted as a N₂O sink during winter, while became a N₂O source in the growing season. The results showed that gas exchange between soil/snow and the atmosphere in the winter season contributed greatly to the annual budgets. The winter season CH₄ flux was about 3.24% of the annual flux and the winter uptake of N₂O accounted for 13.70% of the growing-season emission. Conversion marsh to dryland resulted in a shift from a strong CH₄ source to a weak sink (from 199.12 ± 39.04 to ?1.37 ± 0.68 kg CH₄ ha^?1 yr^?1), while increased N₂O emissions somewhat (from 4.07 ± 1.72 to 4.90 ± 1.52 kg N₂O ha^?1 yr^?1). Conversion marsh to rice field significantly decreased CH₄ emission from 199.12 ± 39.04 to 94.82 ± 9.86 kg CH₄ ha^?1 yr^?1 and N₂O emission from 4.07 ± 1.72 to 2.09 ± 0.79 kg N₂O ha^?1 yr^?1.     

Agricultural ammonia emissions inventory and spatial distribution in the North China Plain

An agricultural ammonia (NH₃) emission inventory in the North China Plain (NCP) on a prefecture level for the year 2004, and a 5 × 5 km² resolution spatial distribution map, has been calculated for the first time. The census database from China's statistics datasets, and emission factors re-calculated by the RAINS model supported total emissions of 3071 kt NH₃-N yr⁻¹ for the NCP, accounting for 27% of the total emissions in China. NH₃ emission from mineral fertilizer application contributed 1620 kt NH₃-N yr⁻¹, 54% of the total emission, while livestock emissions accounted for the remaining 46% of the total emissions, including 7%, 27%, 7% and 5% from cattle, pigs, sheep and goats, and poultry, respectively. A high-resolution spatial NH₃ emissions map was developed based on 1 × 1 km land use database and aggregated to a 5 × 5 km grid resolution. The highest emission density value was 198 kg N ha⁻¹ yr⁻¹.     

Characteristics of atmospheric speciated mercury concentrations (TGM,Hg(II) and Hg(p)) in Seoul,Korea

Ambient speciated mercury concentrations including total gaseous mercury (TGM), gaseous divalent mercury (Hg(II)), and particulate mercury (Hg(p)) were measured on the roof of the Graduate School of Public Health building in Seoul, Korea from February 2005 to February 2006. The average concentrations were 3.22 ± 2.10 ng m^?3, 27.2 ± 19.3 pg m^?3, and 23.9 ± 19.6 pg m^?3 for TGM, Hg(II), and Hg(p), respectively. Hg(II) and Hg(p) concentrations were higher during the daytime than during the nighttime, probably because of high photochemical activity. Hg⁰ concentrations were not significantly correlated with ozone however a positive correlation between ozone and Hg(II) was found during periods of high humidity. Eighteen days were characterized as pollution events with 24 h average PM_2.5 concentrations >65 μg m^?3. The average concentrations of TGM and Hg(p) during these events were 1.4–2 times higher than those during non-pollution events. In order to identify the contribution of long-range transported mercury to the enhanced mercury concentrations in Korea, an episode was defined as a period with hourly average TGM and CO concentrations higher than the monthly average TGM and CO concentrations and with significant enhancement of both TGM and CO concentrations for at least 10 h. A total of 70 episodes were identified during the sampling period: 36 local episodes and 34 long-range transport episodes. The mean ΔTGM/ΔCO slope for all episodes was 0.0063 ng m^?3 ppbv^?1 which agreed well with the slope (0.0036–0.0074 ng m^?3 ppbv^?1) found in previous studies that identified long-range transport of TGM from China. The mean slope during non-events was 0.0011 ng m^?3 ppbv^?1. Back-trajectory analysis showed that during episodes, air parcels arrived mostly from the major industrial areas in China (n = 25, 73%), followed by Japan (n = 4, 12%), Yellow Sea (n = 3, 9%), and Russia (n = 2, 6%).     

Historical deposition of mercury and selected trace elements to high-elevation National Parks in the Western U.S. inferred from lake-sediment cores

Atmospheric deposition of Hg and selected trace elements was reconstructed over the past 150 years using sediment cores collected from nine remote, high-elevation lakes in Rocky Mountain National Park in Colorado and Glacier National Park in Montana. Cores were age dated by ²¹⁰Pb, and sedimentation rates were determined using the constant rate of supply model. Hg concentrations in most of the cores began to increase around 1900, reaching a peak sometime after 1980. Other trace elements, particularly Pb and Cd, showed similar post-industrial increases in lake sediments, confirming that anthropogenic contaminants are reaching remote areas of the Rocky Mountains via atmospheric transport and deposition. Preindustrial (pre-1875) Hg fluxes in the sediment ranged from 5.7 to 42 μg m^?2 yr^?1 and modern (post-1985) fluxes ranged from 17.7 to 141 μg m^?2 yr^?1. The average ratio of modern to preindustrial fluxes was 3.2, which is similar to remote lakes elsewhere in North America. Estimates of net atmospheric deposition based on the cores were 3.1 μg m^?2 yr^?1 for preindustrial and 11.7 μg m^?2 yr^?1 for modern times. Current-day measurements of wet deposition range from 5.0 to 8.6 μg m^?2 yr^?1, which are lower than the modern sediment-based estimate of 11.7 μg m^?2 yr^?1, perhaps owing to inputs of dry-deposited Hg to the lakes.     

Comparative study on indoor air quality in Japan and China: Characteristics of residential indoor and outdoor VOCs

We conducted a comparative study on the indoor air quality for Japan and China to investigate aromatic volatile organic compounds (VOCs) in indoor microenvironments (living room, bedroom, and kitchen) and outdoors in summer and winter during 2006–2007. Samples were taken from Shizuoka in Japan and Hangzhou in China, which are urban cities with similar latitudes. Throughout the samplings, the indoor and outdoor concentrations of many of the targeted VOCs (benzene, toluene, ethylbenzene, xylenes, and trimethylbenzenes) in China were significantly higher than those in Japan. The indoor concentrations of VOCs in Japan were somewhat consistent with those outdoors, whereas those in China tended to be higher than those outdoors. Here, we investigated the differences in VOC concentrations between Japan and China. Compositional analysis of indoor and outdoor VOCs showed bilateral differences; the contribution of benzene in China was remarkably higher than that in Japan. Significant correlations (p < 0.05) for benzene were observed among the concentrations in indoor microenvironments and between the outdoors and living rooms or kitchens in Japan. In China, however, significant correlations were observed only between living rooms and bedrooms. These findings suggest differences in strengths of indoor VOC emissions between Japan and China. The source characterizations were also investigated using principal component analysis/absolute principal component scores. It was found that outdoor sources including vehicle emission and industrial sources, and human activity could be significant sources of indoor VOC pollution in Japan and China respectively. In addition, the lifetime cancer risks estimated from unit risks and geometric mean indoor concentrations of carcinogenic VOCs were 2.3 × 10^?5 in Japan and 21 × 10^?5 in China, indicating that the exposure risks in China were approximately 10 times higher than those in Japan.     

Carbonyl sulfide,dimethyl sulfide and carbon disulfide in the Pearl River Delta of southern China: Impact of anthropogenic and biogenic sources

Reduced sulfur compounds (RSCs) such as carbonyl sulfide (OCS), dimethyl sulfide (DMS) and carbon disulfide (CS₂) impact radiative forcing, ozone depletion, and acid rain. Although Asia is a large source of these compounds, until now a long-term study of their emission patterns has not been carried out. Here we analyze 16 months of RSC data measured at a polluted rural/coastal site in the greater Pearl River Delta (PRD) of southern China. A total of 188 canister air samples were collected from August 2001 to December 2002. The OCS and CS₂ mixing ratios within these samples were higher in autumn/winter and lower in summer due to the influence of Asian monsoon circulations. Comparatively low DMS values observed in this coastal region suggest a relatively low biological productivity during summer months. The springtime OCS levels in the study region (574 ± 40 pptv) were 25% higher than those on other East Asia coasts such Japan, whereas the springtime CS₂ and DMS mixing ratios in the PRD (47 ± 38 pptv and 22 ± 5 pptv, respectively) were 3–30 times lower than elevated values that have been measured elsewhere in East Asia (Japan and Korea) at this time of year. Poor correlations were found among the three RSCs in the whole group of 188 samples, suggesting their complex and variable sources in the region. By means of backward Lagrangian particle release simulations, air samples originating from the inner PRD, urban Hong Kong and South China Sea were identified. The mean mixing ratio of OCS in the inner PRD was significantly higher than that in Hong Kong urban air and South China Sea marine air (p < 0.001), whereas no statistical differences were found for DMS and CS₂ among the three regions (p > 0.05). Using a linear regression method based on correlations with the urban tracer CO, the estimated OCS emission in inner PRD (49.6 ± 4.7 Gg yr^?1) was much higher than that in Hong Kong (0.32 ± 0.05 Gg yr^?1), whereas the estimated CS₂ and DMS emissions in the study region accounted for a very few percentage of the total CS₂ and DMS emission in China. These findings lay the foundation for better understanding sulfur chemistry in the greater PRD region of southern China.     

Seasonal variability of radon-derived fetch regions for Sado Island,Japan, based on 3 years of observations: 2002–2004

Three years of hourly atmospheric radon measurements at Sado Island (Japan) are discussed and compared with corresponding measurements at Gosan (South Korea), and Hok Tsui (China). In conjunction with back trajectory analysis, Sado radon data are used to characterise the seasonal variability in fetch regions of air masses subject to extremes of terrestrial influence. In winter, fetch regions of air masses that have experienced the greatest terrestrial influence covered southern Siberia; in summer, the terrestrial fetch was dominated by Japan; throughout the remaining months the terrestrial fetch encompassed the Korean Peninsula and far eastern China. Summer radon data are then used to estimate the radon flux from central Honshu (23.5 mBq m^?2 s^?1), which varied regionally between 10.6 and 47.9 mBq m^?2 s^?1. The Sado radon record reported here completes a 4-site, multi-year dataset of hourly radon concentrations across East Asia and the central Pacific (spanning 16° of latitude), which constitutes a unique evaluation tool for transport and mixing schemes of atmospheric and chemical transport models.     

Impact of mercury emissions from historic gold and silver mining: Global modeling

We compare a global model of mercury to sediment core records to constrain mercury emissions from the 19th century North American gold and silver mining. We use information on gold and silver production, the ratio of mercury lost to precious metal produced, and the fraction of mercury lost to the atmosphere to calculate an a priory mining inventory for the 1870s, when the historical gold rush was at its highest. The resulting global mining emissions are 1630 Mg yr^?1, consistent with previously published studies. Using this a priori estimate, we find that our 1880 simulation over-predicts the mercury deposition enhancements archived in lake sediment records. Reducing the mining emissions to 820 Mg yr^?1 improves agreement with observations, and leads to a 30% enhancement in global deposition in 1880 compared to the pre-industrial period. For North America, where 83% of the mining emissions are located, deposition increases by 60%. While our lower emissions of atmospheric mercury leads to a smaller impact of the North American gold rush on global mercury deposition than previously estimated, it also implies that a larger fraction of the mercury used in extracting precious metals could have been directly lost to local soils and watersheds.     

Mercury emission trend influenced by stringent air pollutants regulation for coal-fired power plants in Korea

Regulatory control of mercury emission from anthropogenic sources has become a global concern in the recent past. Coal-fired power plants are one of the largest sources of anthropogenic mercury emission into the atmosphere. This paper summarizes the current reducing trend of mercury emission as co-beneficial effect by more stringent regulation changes to control primary air pollutants with introducing test results from the commercial coal-fired facilities and suggesting a guideline for future regulatory development in Korea. On average, mercury emission concentrations ranged 16.3–2.7 μg Sm^?3, 2.4–1.1 μg Sm^?3, 3.1–0.7 μg Sm^?3 from anthracite coal-fired power plants equipped with electrostatic precipitator (ESP), bituminous coal-fired power plants with ESP + flue gas desulphurization (FGD) and bituminous coal-fired power plants with selective catalytic reactor (SCR) + cold side (CS) ? ESP + wet FGD, respectively. Among the existing air pollution control devices, the best configuration for mercury removal in coal-fired power plants was SCR + CS ? ESP + wet FGD, which were installed due to the stringent regulation changes to control primary air pollutants emission such as SO₂, NOx and dust. It was estimated that uncontrolled and controlled mercury emission from coal-fired power plants as 10.3 ton yr^?1 and 3.2 ton yr^?1 respectively. After the installation of ESP, FGD and SCR system, following the enforcement of the stringent regulation, 7.1 ton yr^?1 of mercury emission has been reduced (nearly 69%) from coal-fired power plants as a co-benefit control. Based on the overall study, a sample guideline including emission limits were suggested which will be applied to develop a countermeasure for controlling mercury emission from coal-fired power plants.     

Spatial distribution and source identification of wet deposition at remote EANET sites in Japan

Wet deposition of major ions was discussed from the viewpoint of its potential sources for six remote EANET sites in Japan (Rishiri, Happo, Oki, Ogasawara, Yusuhara, and Hedo) having sufficiently high data completeness during 2000–2004. The annual deposition for each site ranged from 12.1 to 46.6 meq m⁻² yr⁻¹ for nss-SO₄²⁻, from 5.0 to 21.9 meq m⁻² yr⁻¹ for NO₃⁻. The ranges of annual deposition of the two ions for the sites were lower than those for urban and rural sites in Japanese Acid Deposition Survey by Ministry of the Environment, Japan, and higher than those for global remote marine sites. Factor analysis was performed on log-transformed daily wet deposition of major ions for each site. The obtained two factors were interpreted as (1) acid and soil source (or acid source for some sites), and (2) sea-salt source for all the sites. This indicates that wet deposition of ions over the remote areas in Japan has a similar structure in terms of types of sources. Factor scores of acid and soil source were relatively high during Kosa (Asian dust) events in spring in western Japan. Back-trajectories for high-deposition episodes of acid and soil source (or acid source) for the remote sites showed that episodic air masses frequently came from the northeastern area of Asian Continent in spring and winter, and from central China in summer and autumn. This indicates a large contribution of continental emissions to wet deposition of ions over the remote areas in Japan.     

The characteristics of Asian-dust storms during 2000–2002: From the source to the sea

About 42 Asian-dust storms influenced the mainland and China during 2000–2002. Based on the Micaps meteorology data provided by China Meteorological Administration, the basic characteristics, including the source, movement route and influenced areas were studied for each case. It was shown that about 70% Asian-dust storms that influence China came from Mongolia, and were strengthened during the way from west to east. In 2000–2002, there was about 63.9% Asian-dust weather that might have affected China seas through three different routes. The probability is affecting the Bohai Sea was 27.4%, the Yellow Sea 30.9%, the East China Sea 12.3%, the Korea Channel 20.2% and the Japan Sea 9.2%. Annual dry deposition flux to the Yellow Sea was about 0.13 g m⁻² d⁻¹, and in spring was ∼0.20 g m⁻² d⁻¹. The total amount of dry deposition to the Yellow Sea was ∼17.9 Tg yr⁻¹.     

An integrated tool to assess the role of new planting in PM10 capture and the human health benefits: A case study in London

The role of vegetation in mitigating the effects of PM₁₀ pollution has been highlighted as one potential benefit of urban greenspace. An integrated modelling approach is presented which utilises air dispersion (ADMS-Urban) and particulate interception (UFORE) to predict the PM₁₀ concentrations both before and after greenspace establishment, using a 10 × 10 km area of East London Green Grid (ELGG) as a case study. The corresponding health benefits, in terms of premature mortality and respiratory hospital admissions, as a result of the reduced exposure of the local population are also modelled. PM₁₀ capture from the scenario comprising 75% grassland, 20% sycamore maple (Acer pseudoplatanus L.) and 5% Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) was estimated to be 90.41 t yr⁻¹, equating to 0.009 t ha⁻¹ yr⁻¹ over the whole study area. The human health modelling estimated that 2 deaths and 2 hospital admissions would be averted per year.     

Spatial distribution of wet deposition of nitrogen in South Korea

A method is developed to estimate wet deposition of nitrogen in a 11×14 km (0.125°Lon.×0.125°Lat.) grid scale using the precipitation chemistry monitored data at 10 sites scattered over South Korea supplemented by the routinely available precipitation rate data at 65 sites and the estimated emissions of NO₂ and NH₃ at each precipitation monitoring site. This approach takes into account the contributions of local NO₂ and NH₃ emissions and precipitation rates on wet deposition of nitrogen. Wet deposition of nitrogen estimated by optimum regression equations for NO₃⁻ and NH₄⁺ derived from annual total monitored wet deposition and that of emissions of NO₂ and NH₃ is incorporated to normalize wet deposition of nitrogen at each precipitation rate class, which is divided into 6 classes. The optimum regression equations for the estimation of wet deposition of nitrogen at precipitation monitoring sites are developed using the normalized wet deposition of nitrogen and the precipitation rate at 10 precipitation chemistry monitoring sites. The estimated average annual total wet depositions of NO₃⁻ and NH₄⁺ are found to be 260 and 500 eq ha⁻¹ yr⁻¹ with the maximum values of 400 and 930 eq ha⁻¹ yr⁻¹, respectively. The annual mean total wet deposition of nitrogen is found to be about 760 eq ha⁻¹ yr⁻¹, of which more than 65% is contributed by wet deposition of ammonium while, the emission of NH₃ is about half of that of NO₂, suggesting the importance of NH₃ emission for wet deposition of nitrogen in South Korea.     

On-road comparison of a portable emission measurement system with a mobile reference laboratory for a heavy-duty diesel vehicle

On-road comparisons were made between a mobile emissions laboratory (MEL) meeting federal standards and a portable emissions measurement system (PEMS). These comparisons were made over different conditions; including road grade, vibration, altitude, electric fields, and humidity with the PEMS mounted inside and outside of the tractor's cab. Brake-specific emissions were calculated to explore error differences between the MEL and PEMS during the Not-To-Exceed (NTE) engine operating zone. The PEMS brake-specific NOx (bsNOx) NTE emissions were biased high relative to the MEL and, in general, were about 8% of the 2007 in-use NTE NO_x standard of 2.68 g kW^?1 h^?1 (2.0 g hp^?1 h^?1). The bsCO₂ emissions for the PEMS were also consistently biased high relative to the MEL, with an average deviation of +4% ± 2%. NMHC and CO emissions were very low and typically less than 1% of the NTE threshold. This research was part of a comprehensive program to determine the “allowance” when PEMS are used for in-use compliance testing of heavy-duty diesel vehicles (HDDVs).     

Influence of ship emissions on ozone concentrations around coastal areas during summer season

The influence of ship emissions on ozone (O₃) concentrations in a coastal area (CA) including Busan port, Korea was examined based on a numerical modeling approach during a high O₃ episode. The analysis was performed by two sets of simulation scenarios: (1) with ship emissions (e.g., TOTAL case) and (2) without ship emissions (e.g., BASE case). A process analysis (PA) (the integrated processes rate (IPR) and integrated reaction rate (IRR) analyses) was used to evaluate the relative contributions of individual physical and chemical processes in O₃ production in and around the CA (e.g., sites of Dong Sam (DS) and Dae Yeon (DY)). The model study suggested the possibility that pollutant gases emitted from the ships traversing Busan port can exert a direct impact on the O₃ concentration levels in the CA. Largest impacts of ship emissions on the O₃ concentrations were predicted at the coast (up to 15 ppb) and at inland locations (about 5 ppb) due to both the photochemical production of pollutant gases emitted from the ships and meteorological conditions. From the PA, the photochemical production of O₃ (P(O₃)) due to ship emissions in the CA was found to increase by a mean of 1.5 ppb h^?1 (especially by ≥10 ppb h^?1 at the DS site) during the day.