EPA Model Research Articles

Contribution of biogenic emissions to the atmospheric composition of the Balkan Region and Bulgaria

The present work aims at studying the local to regional atmospheric pollution transport and transformation processes over the Balkan Peninsula and Bulgaria. The US EPA models-3 system is chosen as a modelling tool. As the NCEP global analysis data with one degree resolution is used as meteorological background, the models nesting capabilities are applied for downscaling the simulations to a 9 km resolution over Balkans and 3 km over Bulgaria. The TNO emission inventory is used as emission input. Special pre-processing procedures are created for introducing temporal profiles and speciation of the emissions. The study is based on a large number of numerical simulations carried out for two emission scenarios – with all the emissions and with biogenic emissions excluded. Some results from both emission scenarios which make it possible to evaluate the contribution of biogenic emissions are demonstrated in the paper.

Reassessment of Life Cycle Greenhouse Gas Emissions for Soybean Biodiesel

This study updates the life cycle greenhouse gas (GHG) emissions for soybean biodiesel with revised system boundaries and the inclusion of indirect land use change using the most current set of agricultural data. The updated results showed that life cycle GHG emission from biodiesel use was reduced by 81.2% compared to 2005 baseline diesel. When the impacts of lime application and soil N2O emissions were excluded for more direct comparison with prior results published by the National Renewable Energy Laboratory (NREL), the reduction was 85.4%. This is a significant improvement over the 78.5% GHG reduction reported in the NREL study. Agricultural lime accounted for 50.6% of GHG from all agricultural inputs. Soil N2O accounted for 18.0% of total agricultural emissions. The improvement in overall GHG reduction was primarily due to lower agricultural energy usage and improved soybean crushing facilities. This study found that soybean meal and oil price data from the past ten years had a significant positive correlation (R2 = 0.73); hence, it is argued that soybean meal and oil are both responsible for indirect land use change from increased soybean demand. It is concluded that when there is a strong price correlation among co-products, system boundary expansion without a proper co-product allocation for indirect land use change produces erroneous results. When the emissions associated with predicted indirect land use change were allocated and incorporated using U.S. EPA model data, the GHG reduction for biodiesel was 76.4% lower than 2005 baseline diesel.

A study on the aerosol optical properties over East Asia using a combination of CMAQ-simulated aerosol optical properties and remote-sensing data via a data assimilation technique

Abstract. To more accurately estimate direct radiative forcing (DRF) by aerosols, and better investigate particulate pollution over East Asia, precise calculations of the optical properties of aerosols, such as aerosol optical depth (AOD), single scattering albedo (SSA) and aerosol extinction coefficient (σext), are of primary importance. The aerosol optical properties over East Asia were investigated in this study, based on US EPA Models-3/CMAQ v4.5.1 model simulations. The CMAQ model simulations in this study were improved in several ways compared to those in a previous study (Song et al., 2008). Although the details of the improvements were described in the manuscript, the following points should be emphasized: (1) two data assimilation techniques were employed for producing more accurate AOD products and meteorological fields over East Asia; (2) updated/upgraded emission inventories were used in the CMAQ model simulations with a fine grid resolution of 30 × 30 km2; and (3) the 4-D particulate composition calculated from the CMAQ model simulations was converted into 3-D or 4-D aerosol optical products, using the Malm and Hand (2007) algorithm with significant further modifications. The results from the CMAQ model simulations (without assimilation) showed great improvements compared to those from a previous study. For example, in terms of the regression coefficients (R), R values were increased from 0.48–0.68 (previous study) to 0.62–0.79 (this study). The monthly-averaged CMAQ-simulated single scattering albedo (SSA) also agreed well with the AERONET SSA, with the exceptions of the Hong Kong and Taipei sites, where the air qualities were strongly influenced by active biomass burning events from January to April. There were also excellent matches between the vertical profiles of the CMAQ-simulated σext and LIDAR-retrieved σext. It was also found that the contributions of (NH4)2SO4 during summer, NH4NO3 during winter, sea-salt particles during winter and dust particles during spring to the total AOD were large over East Asia. In particular, the largest contribution of NH4NO3 to the total AOD was found over East Asia during winter. Therefore, it was suggested that this contribution of NH4NO3 should not be neglected. In order to produce more accurate AOD products, the CMAQ-simulated AODs were further assimilated with the MODIS-retrieved AODs. Both of the assimilated and AERONET AODs were better correlated with each other than the CMAQ-simulated and AERONET AODs. The obvious benefits from this study would be that with these improved aerosol optical properties, the particulate pollution (e.g. AOD can be served as a proxy to PM2.5 or PM10) and DRF by aerosols over East Asia can be more satisfactorily investigated in future.

Modelled and measured arsenic exposure around a power station in Slovakia

In 1999-2000 an epidemiological study was carried out to investigate arsenic exposure and risk of nonmelanoma skin cancer in the population around a power station in Slovakia. As part of the exposure assessment for that study, markers of physiological exposure to arsenic (urinary arsenic and nail arsenic) and measures of environmental arsenic were taken. Residential history and arsenic emissions were combined in a measure used to classify the study population's exposure. Here, we take a model designed to estimate the daily arsenic absorption and urinary arsenic excretion developed by the US EPA and compare its output to the values for measured urinary arsenic, measured environmental arsenic and modelled food arsenic used in the previous study. We found that the US EPA model underestimated arsenic exposure in this population. Potential misclassification compared to the exposure used previously was also quantified, with poor agreement between a measured biomarker of current arsenic exposure and modelled estimates of arsenic uptake and excretion. (C) 2011 Published by Elsevier Ltd.

Utilization of satellite observation of ozone and aerosols in providing initial and boundary condition for regional air quality studies

[1] To demonstrate the efficacy of satellite observations in the realization of the background and transboundary transport of pollution in regional air quality modeling practices, satellite observations of ozone and aerosol optical depth were incorporated in the EPA Models-3 Community Multiscale Air Quality (CMAQ) model (http://www.cmascenter.org). Observations from Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite and AOD products from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra (EOS AM) and Aqua (EOS PM) satellites were used to specify initial and lateral boundary conditions (IC/BC) for a simulation that spanned over August 2006. The tools and techniques using the satellite data were tested in the context of current regulatory air quality modeling practices. Daily satellite observations were remapped onto the modeling domain and used as IC/BC for daily segments of a month-long simulation and the results were evaluated against surface and ozonesonde observations. Compared to the standard application of CMAQ, OMI O3 profiles significantly improved model performance in the free troposphere and MODIS aerosol products substantially improved PM2.5 predictions in the boundary layer. The utilization of satellite data for BC helped in the realization of transboundary transport of pollution and was able to explain the recirculation of pollution from Northeast Corridor to the southeastern region. Ozone in the mid- to upper-troposphere was largely dominated by transport and thus benefited most from satellite provided BC. The ozone within the boundary layer was mostly affected by fast production/loss mechanisms that are impacted by surface emissions, chemistry and removal processes and was not impacted as much. A case study for August 18–22 demonstrated that model errors in the placement of a stationary front were the main reason for errors in PM2.5 predictions as the front acted as a boundary between high and low PM2.5 concentrations.

Groundwater Vulnerability Assessment in Shallow Aquifer in Linfen Basin, Shanxi Province, China Using DRASTIC Model

Groundwater pollution is one of the most serious environmental problems in the world. Human activities, e.g. industrial, agricultural and household represent a real threat for groundwater quality. In areas where Groundwater constitutes the main drinking water resources, its vulnerability assessment, to delineate areas that are more susceptible to contamination has become an important element for water resource management and land use planning. Hence, maps of groundwater vulnerability to pollution are becoming more in demand because this essential resource for life represents the main source of drinking water in many parts of the world and particularly in northern China where there is insufficient surface water.This study used the ArcGIS 9.2 software and geographical information system (GIS) techniques to apply an EPA model for determining intrinsic vulnerability of groundwater to pollution in Linfen Basin, Shanxi Province, China. The model is called DRASTIC, representing hydrogeological parameters such as Depth to Aquifer, Net Recharge, Aquifer Media, Soil Media, Topography, Impact of vadose Zones, and Hydraulic Conductivity. The DRASTIC model uses environmental parameters to characterize the hydrogeological setting of any area and to evaluate the aquifer vulnerability. The DRASTIC scores obtained from the model vary from 59 to 147, where the higher value implies the relative greater vulnerability. These values were reclassified into three classes: very low, low and moderate vulnerable zones. The moderate vulnerability zones of Linfen Basin are located in the north and southeastern part of the basin. The moderate vulnerable zones cover around 16.38% of the study area. Huozhou City in the north, Yicheng County, Qu Wo County in the south east are concerned by moderate vulnerability zones.The very low vulnerable zones are well distributed and are mainly located in the middle and south parts of the basin. Some very low vulnerable zones can also be seen in the north east and extreme east parts. Very low vulnerable zones cover about 40.13% of the study area. The remaining parts of the Linfen basin are under low vulnerable zones (43.49%) which are located in the west and Middle West parts of the region.The results of this study can be used to determine where communities should undertake aggressive protection of the groundwater. Regional development planners will benefit from knowledge of local sensitive aquifers.

Use of a process analysis tool for diagnostic study on fine particulate matter predictions in the U.S. – Part I: Model evaluation

Regional ozone (O3) and fine particles (PM2.5) modeling for both research–grade and regulation applications is important due to their known impacts on human health, air quality, and climate change. In this study, the fifth– generation Penn State/NCAR Mesoscale Model (MM5) and the U.S. EPA Models–3/Community Multiscale Air Quality (CMAQ) modeling system are applied to simulate the major air pollutants during the 1999 Southern Oxidants Study episode for the period of 12–28 June 1999. As Part I of two companion papers describing CMAQ performance, process analysis, and sensitivity simulations, this paper presents results from an operational evaluation for meteorological and chemical predictions using the available surface, aircraft, and satellite data. Both MM5 and CMAQ show reasonable performance for major meteorological variables (i.e., temperature, relative humidity, wind direction, planetary boundary layer height) with normalized mean biases (NMBs) of 0.4–24.2%, surface concentrations O3, PM2.5, SO42–, and NH4+ with NMBs of –39% to 24.2%, and vertical profiles of temperature and sulfur dioxide. Relatively poor performance is found in the simulated precipitation (NMBs of –16.3% to 37.4%), the concentrations of NO3–, EC, and OC (NMBs of –77.8% to –22%) and total O3 column mass. The evaluation identifies several research areas that are needed to improve model performance for nitrate, organic carbon, and black carbon at surface, vertical profiles of relative humidity, carbon monoxide, and nitrogen oxides, and tropospheric O3 column abundance.

Use of a process analysis tool for diagnostic study on fine particulate matter predictions in the U.S.–Part II: Analyses and sensitivity simulations

Following the Part I paper that describes an application of the U.S. EPA Models–3/Community Multiscale Air Quality (CMAQ) modeling system to the 1999 Southern Oxidants Study episode, this paper presents results from process analysis (PA) using the PA tool embedded in CMAQ and subsequent sensitivity simulations to estimate the impacts of major model uncertainties identified through PA. Aerosol processes and emissions are the most important production processes for PM2.5 and its secondary components, while horizontal and vertical transport and dry deposition contribute to their removal. Cloud processes can contribute the production of PM2.5 and SO42– and the removal of NO3– and NH4+. The model biases between observed and simulated concentrations of PM2.5 and its secondary inorganic components are found to correlate with aerosol processes and dry deposition at all sites from all networks and sometimes with emissions and cloud processes at some sites. Guided with PA results, specific uncertainties examined include the dry deposition of PM2.5 species and its precursors, the emissions of PM2.5 precursors, the cloud processes of SO42–, and the gas–phase oxidation of SO2. Adjusting the most influential processes/factors (i.e., emissions of NH3 and SO2, dry deposition velocity of HNO3, and gas–phase oxidation of SO2 by OH) is found to improve the model overall performance in terms of SO42–, NO3–, and NH4+ predictions.

Numerical study of some high PM10 level episodes

The study examines the ability of US EPA Models-3 system to reproduce air pollution episodes and to evaluate the role of different processes in the PM10 pattern formation. The case study focuses on three major PM10 episodes, that occurred over Germany in February and March of 2003. The emission input is prepared on the basis of the TNO inventory. The simulated PM10 concentrations are compared with measurements from the EMEP stations in Germany. The Integrated Process Rate Analysis function of CMAQ is applied for clarifying the role of different processes in forming PM10 concentration peaks.

A system for assessment of climatic air pollution levels in Bulgaria: description and first steps towards validation

The EC FP6 project CECILIA (http://www.cecilia-eu.org) aims at climate change impacts and vulnerability assessment in targeted areas of Central and Eastern Europe. Emphasis is given to regional climate change modeling at resolution of 10 km. The respective weather patterns influence local air quality. For its assessment EPA Models-3 (MM5, CMAQ, SMOKE) is used. The meteorological input is produced by the climatic version of ALADIN weather forecast system. TNO emission inventory for 2000 is exploited. The boundary conditions are extracted from 50-km runs over Europe made in Aristotle University of Thessaloniki, Greece. Calculations for the period 1991–2000 are performed, results presented.

Temporal and spatial changes in mixed layer properties and atmospheric net heat flux in the Nordic Seas

The Nordic Seas are an important area of the World Ocean where warm Atlantic waters penetrate far north forming the mild climate of Northern Europe. These waters represent the northern rim of the global thermohaline circulation. Estimates of the relationships between the net heat flux and mixed layer properties in the Nordic Seas are examined. Oceanographic data are derived from the Oceanographic Data Base (ODB) compiled in the Arctic and Antarctic Research Institute. Ocean weather ship 'Mike' (OWS) data are used to calculate radiative and turbulent components of the net heat flux. The net shortwave flux was calculated using a satellite albedo dataset and the EPA model. The net longwave flux was estimated by Southampton Oceanography Centre (SOC) method. Turbulent fluxes at the air-sea interface were calculated using the COARE 3.0 algorithm. The net heat flux was calculated by using oceanographic and meteorological data of the OWS 'Mike'. The mixed layer depth was estimated for the period since 2002 until 2009 by the 'Mike' data as well. A good correlation between these two parameters has been found. Sensible and latent heat fluxes controlled by surface air temperature/sea surface temperature gradient are the main contributors into net heat flux. Significant correlation was found between heat fluxes variations at the OWS 'Mike' location and sea ice export from the Arctic Ocean.

Reconciling International Investment Law and Sustainable Development: Necessity or Luxury?

The paper aims at studying the potential accommodation of the concept of sustainable development within the regime of international law regulating foreign direct investment (FDI). Reconciliation of international investment law and sustainable development is part of the current awareness of necessity to broaden interests involved in the international investment regime responding to such tensions as possible “regulatory chill”, negative effect of FDI on development of host States and global commitment to promote sustainable development in every level of decision-making. The paper consists of two main parts and focuses on: (1) the notion of sustainable development and its legal character, and (2) proposed methods of accommodation of sustainable development in the international investment law regime through normative integration of sustainable development or its elements in the IIAs texts and judicial reasoning methods available to adjudicators. Detailed analysis of such recent IIAs as CARIFORUM EPA and various Model BITs will be provided to resemble the current successful incorporation of sustainable development concerns in investment regime which will possibly influence the drafting of future IIAs.The paper is designed to offer solutions for rebalancing FDI and to contribute to the formulation of international investment law in a more integrated, principled manner in the context of fragmentation versus unity of international law.Presented at the SIEL 2010 Conference in Barcelona.

Understanding of regional air pollution over China using CMAQ, part I performance evaluation and seasonal variation

The U.S. EPA Models-3 Community Multiscale Air Quality (CMAQ) modeling system with the process analysis tool is applied to China to study the seasonal variations and formation mechanisms of major air pollutants. Simulations show distinct seasonal variations, with higher surface concentrations of sulfur dioxide (SO 2), nitrogen dioxide (NO 2), and particulate matter with aerodynamic diameter less than or equal to 10 μm (PM 10), column mass of carbon monoxide (CO) and NO 2, and aerosol optical depth (AOD) in winter and fall than other seasons, and higher 1-h O 3 and troposphere ozone residual (TOR) in spring and summer than other seasons. Higher concentrations of most species occur over the eastern China, where the air pollutant emissions are the highest in China. Compared with surface observations, the simulated SO 2, NO 2, and PM 10 concentrations are underpredicted throughout the year with NMBs of up to −51.8%, −32.0%, and −54.2%, respectively. Such large discrepancies can be attributed to the uncertainties in emissions, simulated meteorology, and deviation of observations based on air pollution index. Max. 1-h O 3 concentrations in Jan. and Jul. at 36-km are overpredicted with NMBs of 12.0% and 19.3% and agree well in Apr. and Oct. Simulated column variables can capture the high concentrations over the eastern China and low values in the central and western China. Underpredictions occur over the northeastern China for column CO in Apr., TOR in Jul., and AODs in both Apr. and Jul.; and overpredictions occur over the eastern China for column CO in Oct., NO 2 in Jan. and Oct., and AODs in Jan. and Oct. The simulations at 12-km show a finer structure in simulated concentrations than that at 36-km over higher polluted areas, but do not always give better performance than 36-km. Surface concentrations are more sensitive to grid resolution than column variables except for column NO 2, with higher sensitivity over mountain and coastal areas than other regions.

Comparison of AERMOD and EIAA with respect to the Alaska tracer data

This paper inter-compares the performance of AERMOD and EIAA (the current Chinese regulatory model) against the Alaska tracer field experiment. The predicted maximum arc-wise Ground Level Concentrations (GLC) are compared with the observed tracer field data. The scatter plots, QQ plots, and residual plots are examined. EIAA frequently underestimates the GLC because it lacks any downwash algorithm. AERMOD with downwash shows significant improvement over the performance of EIAA. This work was initiated by a need for updating the Chinese regulatory guidelines, and to examine the suitability of US EPA models for use in China.

Developing ontology-based EPA for representing accounting principles in a reusable knowledge component

This study proposed an ontological EPA model (Event, Principle and Account) for describing accounting principles using a reusable knowledge component. The essential characteristics of the model include: (1) based on traditional accounting definitions for typical accounts ( A ) and business events ( E ), where the ontological properties of A and E can be identified. These characteristics can be further used to create a knowledge hierarchy for both A and E ; (2) identifies the element P (accounting principle), which in turn can be used to measure the economic effects of events on accounts; (3) creates a relationship between E – P , which identifies how to adopt suitable principles for classifying events; and (4) the inferential ( E – P )– A relationship, which identifies the effect of a classified event on resources (or accounts). Following typical knowledge engineering processes, hierarchical knowledge of accounting principles can be represented, stored and reused. EPA examples are demonstrated using OWL-based ontology. This study claims that the knowledge framework developed in EPA can provide a basis for full accounting knowledge creation, storage and sharing.

Investigation of NO<sub>x</sub> emissions and NO<sub>x</sub>-related chemistry in East Asia using CMAQ-predicted and GOME-derived NO<sub>2</sub> columns

Abstract. In this study, NO2 columns from the US EPA Models-3/CMAQ model simulations carried out using the 2001 ACE-ASIA (Asia Pacific Regional Aerosol Characterization Experiment) emission inventory over East Asia were compared with the GOME-derived NO2 columns. There were large discrepancies between the CMAQ-predicted and GOME-derived NO2 columns in the fall and winter seasons. In particular, while the CMAQ-predicted NO2 columns produced larger values than the GOME-derived NO2 columns over South Korea for all four seasons, the CMAQ-predicted NO2 columns produced smaller values than the GOME-derived NO2 columns over North China for all seasons with the exception of summer (summer anomaly). It is believed that there might be some error in the NOx emission estimates as well as uncertainty in the NOx chemical loss rates over North China and South Korea. Regarding the latter, this study further focused on the biogenic VOC (BVOC) emissions that were strongly coupled with NOx chemistry during summer in East Asia. This study also investigated whether the CMAQ-modeled NO2/NOx ratios with the possibly overestimated isoprene emissions were higher than those with reduced isoprene emissions. Although changes in both the NOx chemical loss rates and NO2/NOx ratios from CMAQ-modeling with the different isoprene emissions affected the CMAQ-modeled NO2 levels, the effects were found to be limited, mainly due to the low absolute levels of NO2 in summer. Seasonal variations of the NOx emission fluxes over East Asia were further investigated by a set of sensitivity runs of the CMAQ model. Although the results still exhibited the summer anomaly possibly due to the uncertainties in both NOx-related chemistry in the CMAQ model and the GOME measurements, it is believed that consideration of both the seasonal variations in NOx emissions and the correct BVOC emissions in East Asia are critical. Overall, it is estimated that the NOx emissions are underestimated by ~57.3% in North China and overestimated by ~46.1% in South Korea over an entire year. In order to confirm the uncertainty in NOx emissions, the NOx emissions over South Korea and China were further investigated using the ACE-ASIA, REAS (Regional Emission inventory in ASia), and CAPSS (Clean Air Policy Support System) emission inventories. The comparison between the CMAQ-calculated and GOME-derived NO2 columns indicated that both the ACE-ASIA and REAS inventories have some uncertainty in NOx emissions over North China and South Korea, which can also lead to some errors in modeling the formation of ozone and secondary aerosols in South Korea and North China.

The Use of Modern Third-Generation Air Quality Models (MM5-EMIMO-CMAQ) for Real-Time Operational Air Quality Impact Assessment of Industrial Plants

In many cases, a substantial proportion of large industrial emissions are located in the surrounding areas of cities and are the cause of an important part of air concentrations over the city and surrounding areas. The need to have a tool to analyze and manage these concentrations is the main objective of this contribution. In this paper, we show the implementation of an adapted version of the MM5-CMAQ (Byun et al. 1998, Description of the Models-3 Community Multiscale Air Quality (CMAQ) model. Proceedings of the American Meteorological Society 78th Annual Meeting Phoenix, AZ, Jan. 11–16, 264–268, 1998)—PSU/NCAR and EPA (US) models—modeling system for a large combined cycle power plant located near Madrid city (Spain). The system called TEAP (EUREKA project)—a Tool to Evaluate the Air Quality Impact of Industrial Plants—allows the assessment of the impact of each individual power group (400 MW) in real-time and forecasting mode. As a consequence, the industrial plant and authorities are having a period of time (≈16 h) to decide to switch off one power group or several, to minimize or avoid the possible exceedance of European Union (EU) limits—as declared in the EU directives. The quantification of the impact of these possible exceedances of EU Directives due to emissions produced by the power plant is essential for decision making according to the daily forecasts. We will show the implementation of the TEAP system and operation in two real applications which are operating since summer 2005 and January, 2007 in the surrounding area of Madrid (Spain).

Microbial risk assessment with the OAEL approach at water abstraction points in rural Kenya

US-based models for recreational water quality were applied to characterize the potential health risk (PHR) of infection with gastroenteritis (GI) and highly credible gastroenteritis (HCGI) illnesses from single exposure at several water abstraction points (WAPs) along the Njoro River in rural Kenya. Ambient geometric mean densities of Escherichia coli (EC) and intestinal enterococci (IE) were generally high (2–4 log units of cfu/100 ml) and risk levels were grossly in excess of acceptable health risk (AHR) levels for bathing and drinking. PHR was 2–3 times higher with the Cabelli (IE) model (Equation (2)) compared to the US EPA (EC) model (Equation (1)). Risk levels varied among WAPs in concomitance to the spatial and seasonal variability of ambient EC and IE densities. With the Cabelli IE model, PHR of HCGI illness on single exposure to the dry weather 95th percentile IE density for bathing was 2.5% of the exposed population at Logoman compared to 5.2% at Turkana Flats, 4.9% at Kenyatta or Nessuit and 4.6%, 4.5% and 4.2% at Treetop, Segotik and Njoro Bridge, respectively. PHR was ⩾5% on exposure to the wet weather 95th percentile IE density at all WAPs, excepting Treetop with 4.3%. Relative risk levels increased by at least 30 and 70 times for GI and HCGI illnesses, respectively, from drinking (250 ml) raw stream water, rising erratically in wet weather by >80% of the dry weather risk at Logoman, >30% at Njoro Bridge and Kenyatta and 10–15% at Segotik, Nessuit and Turkana Flats. By stipulating freshwater bathing water quality guidelines of 126 and 33 cfu/100 ml for EC and IE, respectively, US, EPA upholds maximum AHR levels at 0.7% and 1.9% for EC and IE, respectively. Hence, reducing current PHR levels at the WAPs to the US, EPA bathing AHR levels would require at least 2–4 log reductions of IE and EC densities with even further log reductions to achieve the WHO recommended drinking water AHR level of 0.1%. This would necessitate specialized treatment, in particular point-of-use treatment at the household level, as well as the implementation of comprehensive catchment management measures to protect the stream and the WAPs.

An investigation into seasonal and regional aerosol characteristics in East Asia using model-predicted and remotely-sensed aerosol properties

Abstract. In this study, the spatio-temporal and seasonal distributions of EOS/Terra Moderate Resolution Imaging Spectroradiometer (MODIS)-derived aerosol optical depth (AOD) over East Asia were analyzed in conjunction with US EPA Models-3/CMAQ v4.3 modeling. In this study, two MODIS AOD products (τMODIS: τM-BAER and τNASA) retrieved through a modified Bremen Aerosol Retrieval (M-BAER) algorithm and NASA collection 5 (C005) algorithm were compared with the AOD (τCMAQ) that was calculated from the US EPA Models-3/CMAQ model simulations. In general, the CMAQ-predicted AOD values captured the spatial and temporal variations of the two MODIS AOD products over East Asia reasonably well. Since τMODIS cannot provide information on the aerosol chemical composition in the atmosphere, different aerosol formation characteristics in different regions and different seasons in East Asia cannot be described or identified by τMODIS itself. Therefore, the seasonally and regionally varying aerosol formation and distribution characteristics were investigated by the US EPA Models-3/CMAQ v4.3 model simulations. The contribution of each particulate chemical species to τMODIS and τCMAQ showed strong spatial, temporal and seasonal variations. For example, during the summer episode, τMODIS and τCMAQ were mainly raised due to high concentrations of (NH4)2SO4 over Chinese urban and industrial centers and secondary organic aerosols (SOAs) over the southern parts of China, whereas during the late fall and winter episodes, τMODIS and τCMAQ were higher due largely to high levels of NH4NO3 formed over the urban and industrial centers, as well as in areas with high NH3 emissions. τCMAQ was in general larger than τMODIS during the year, except for spring. The high biases (τCMAQ>τMODIS) may be due to the excessive formation of both (NH4)2SO4 (summer episode) and NH4NO3 (fall and winter episodes) over China, possibly from the use of overestimated values for NH3 emissions in the CMAQ modeling. According to CMAQ modeling, particulate NH4NO3 made a 14% (summer) to 54% (winter) contribution to σext and τCMAQ. Therefore, the importance of NH4NO3 in estimating τ should not be ignored, particularly in studies of the East Asian air quality. In addition, the accuracy of τM-BAER and τNASA was evaluated by a comparison with the AOD (τAERONET) from the AERONET sites in East Asia. Both τM-BAER and τNASA showed a strong correlation with τAERONET around the 1:1 line (R=0.79), indicating promising potential for the application of both the M-BAER and NASA aerosol retrieval algorithms to satellite-based air quality monitoring studies in East Asia.

Air pollution transport in the Balkan region and country-to-country pollution exchange between Romania, Bulgaria and Greece

US EPA Models-3 system is used for calculating the exchange of ozone pollution between three countries in southeast Europe. For the purpose, three domains with resolution 90, 30 and 10 km are chosen in such a way that the most inner domain with dimensions 90 × 147 points covers entirely Romania, Bulgaria and Greece. The ozone pollution levels are studied on the base of three indexes given in the EU Ozone Directive, mainly accumulated over threshold of 40 ppb for crops (AOT40C, period May–July), number of days with 8-h running average over 60 ppb (NOD60) and averaged daily maximum (ADM). These parameters are calculated for every scenario and the influence of each country emissions on the pollution of the region is estimated and commented. Oxidized and reduced sulphur and nitrogen loads over the territories of the three countries are also determined. The application of all scenarios gave the possibility to estimate the contribution of every country to the S and N pollution of the others and detailed blame matrixes to be build. Comparison of the ozone levels model estimates with data from the EMEP monitoring stations is made.