Air quality improvement by a forested, peri-urban national park was quantified by combining the Urban Forest Effects (UFORE) and the Weather Research and Forecasting coupled with Chemistry (WRF-Chem) models. We estimated the ecosystem-level annual pollution removal function of the park’s trees, shrub and grasses using pollution concentration data for carbon monoxide (CO), ozone (O₃), and particulate matter less than 10 microns in diameter (PM₁₀), modeled meteorological and pollution variables, and measured forest structure data. Ecosystem-level O₃ and CO removal and formation were also analyzed for a representative month. Total annual air quality improvement of the park’s vegetation was approximately 0.02% for CO, 1% for O₃, and 2% for PM₁₀, of the annual concentrations for these three pollutants. Results can be used to understand the air quality regulation ecosystem services of peri-urban forests and regional dynamics of air pollution emissions from major urban areas.

Socio-economic factors have significant influences on air quality and are commonly used to guide environmental planning and management. Based on data from 85 long-term daily monitoring cities in China, air quality as evaluated by AOFDAQ-A (Annual Occurrence Frequency of Daily Air Quality above Level III), was correlated to socio-economic variable groups of urbanization, pollution and environmental treatment by variation partitioning and hierarchical partitioning methods. We found: (1) the three groups explained 43.5% of the variance in AOFDAQ-A; (2) the contribution of “environmental investment” to AOFDAQ-A shown a time lag effect; (3) “population in mining sector” and “coverage of green space in built-up area” were respectively the most significant negative and positive explanatory socio-economic variables; (4) using eight largest contributing individual factors, a linear model to predict variance in AOFDAQ-A was constructed. Results from our study provide a valuable reference for the management and control of air quality in Chinese cities.

For a given emissions inventory, the general levels of air pollutants and the spatial distribution of their concentrations are determined by the physiochemical state of the atmosphere. Apart from the trivial seasonal and daily cycles, most of the variability is associated with the atmospheric synoptic scale. A simple methodology for assessing future levels of air pollutants' concentrations based on synoptic forecasts is presented. At short time scales the methodology is comparable and slightly better than persistence and seasonal forecasts at categorical classification of pollution levels. It's utility is shown for air quality studies at the long time scale of a changing climate scenario, where seasonality and persistence cannot be used. It is demonstrated that the air quality variability due to changes in the pollution emissions can be expected to be much larger than that associated with the effects of climatic changes.

Three sets of model predicted values for speciated mercury concentrations and dry deposition fluxes over the Great Lakes region were assessed using field measurements and model intercomparisons. The model predicted values were produced by the Community Multiscale Air Quality Modeling System for the year 2002 (CMAQ2002) and for the year 2005 (CMAQ2005) and by the Global/Regional Atmospheric Heavy Metals Model for the year 2005 (GRAHM2005). Median values of the surface layer ambient concentration of gaseous elemental mercury (GEM) from all three models were generally within 30% of measurements. However, all three models overpredicted surface-layer concentrations of gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) by a factor of 2–10 at the majority of the 15 monitoring locations. For dry deposition of GOM plus PBM, CMAQ2005 showed a clear gradient with the highest deposition in Pennsylvania and its surrounding areas while GRAHM2005 showed no such gradient in this region; however, GRAHM2005 had more hot spots than those of CMAQ2005. Predicted dry deposition of GOM plus PBM from these models should be treated as upper-end estimates over some land surfaces in this region based on the tendencies of all the models to overpredict GOM and PBM concentrations when compared to field measurements. Model predicted GEM dry deposition was found to be as important as GOM plus PBM dry deposition as a contributor to total dry deposition. Predicted total annual mercury dry deposition were mostly lower than 5 μg m⁻² to the surface of the Great lakes, between 5 and 15 μg m⁻² to the land surface north of the US/Canada border, and between 5 and 40 μg m⁻² to the land surface south of the US/Canada border. Predicted dry deposition from different models differed from each other by as much as a factor of 2 at regional scales and by a greater extent at local scales.

Benzo[a]pyrene (BaP) has been proven to be toxic and carcinogenic. Since 2010, the European Union officially established target values for BaP concentrations in ambient air. In this study BaP concentrations over Europe have been modelled using a modified version of the chemistry transport model Community Multiscale Air Quality (CMAQ) which includes the relevant reactions of BaP. CMAQ has been run using different emission datasets for the years 1980, 2000, and 2020 as input data. In this study, the changes in BaP concentrations between 1980 and 2020 are evaluated and regions which exceed the European annual target value of 1 ng/m3 are identified, i.e. the Po Valley, the Paris metropolitan area, the Rhine-Ruhr area, Vienna, Madrid, and Moscow. Additionally, the impact of emission reductions on atmospheric concentrations of BaP is investigated. Between 1980 and 2000, half of the BaP emission reductions are due to lower emissions from industrial sources. These emission reductions, however, only contribute to one third of the total ground-level BaP concentration reduction. Further findings are that between 2000 and 2020, a large part (40%) of the BaP concentration reduction is not due to changes in BaP emissions but caused by changes in emissions of criteria pollutants which have an impact on the formation of ozone.

Air pollutants emissions from traffic are very closely connected to urban air quality, in a local scale, as well as to global problems like climate change, in a large scale. Road transport air pollutants emissions represent, in most cases, a critical parameter for a comprehensive and successful understanding of the mechanisms governing the air pollutants concentrations. Hence, reliable estimations and comprehension of road transport emissions are indispensable in order to set reliable strategies in the direction of air pollution abatement and management of air pollutants and greenhouse gases emissions. In this framework, in the present work, the emissions of air pollutants from road transport in Greece will be presented for the whole period 1990–2009 as it was found that a detailed, accurate and reliable emissions inventory was missing. The whole period emissions variation has clarified the impact of the change in the vehicle fleet, the engine technologies and the fuel quality. The calculated results have revealed that the age of the vehicles and the corresponding engine technology are the critical parameters determining the amount of the pollutants emitted. This was mainly observed in both passenger cars and heavy duty vehicles demonstrating the importance of a renewal programme of the old circulating vehicles in order to set an effective air pollution abatement strategy. Passenger cars were found to be responsible for the major part of most air pollutants emissions except from nitrogen oxides and particulates emissions. Heavy duty vehicles contribute more than 66% to nitrogen oxides and particulates emissions. For the whole time period, all calculated pollutants present a decreasing trend, with the exception of carbon dioxide and nitrous oxide which increase constantly, ranging from −96% for sulphur dioxide to −1% for PM10.

The purpose of the research described here is to apply a new approach for generating aquatic critical load (CL) and exceedance calculations for an important acid-sensitive region of the eastern USA. A widespread problem in regional aquatic acidification CL modeling for US ecosystems has been the lack of site-specific weathering data needed to derive accurate model CL estimates. A modified version of the steady-state water chemistry CL model was applied here to estimate CL and exceedances for streams throughout acid-sensitive portions of Virginia and West Virginia. A novel approach for estimating weathering across the regional landscape was applied, based on weathering estimates extracted from a well-tested, process-based watershed model of drainage water acid–base chemistry and features of the landscape that are available as regional spatial data coverages. This process allowed extrapolation of site-specific weathering data from 92 stream watersheds to the regional context in three ecoregions for supporting CL calculations. Calculated CL values were frequently low, especially in the Blue Ridge ecoregion where one-third of the stream length had CL < 50 meq/m²/year to maintain stream ANC at 50 μeq/L under steady-state conditions. About half or more of the stream length in the study region was in exceedance of the CL for long-term aquatic resource protection under assumed nitrogen saturation at steady state. Land managers and air quality policy makers will need this information to better understand responses to air pollution emissions reductions and to develop ecoregion-specific air pollution targets.