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. The first high-resolution spatial distribution of ammonia emissions for the North China Plain showed rates up to 200 kg NH3–N ha−1 yr−1.

The spatial distribution of organochlorine pesticides (OCs) in soils and their potential for soil–air exchange was examined. The most prominent OCs were the DDTs (Geometric Mean, GM = 1.6 ng g−1), endosulfans (0.16 ng g−1), and toxaphenes (0.64 ng g−1). DDTs in soils of southern Mexico showed fresher signatures with higher FDDTe = p,p′-DDT/(p,p′-DDT + p,p′-DDE) and more racemic o,p′-DDT, while the signatures in the central and northern part of Mexico were more indicative of aged residues. Soil–air fugacity fractions showed that some soils are net recipients of DDTs from the atmosphere, while other soils are net sources. Toxaphene profiles in soils and air showed depletion of Parlar 39 and 42 which suggests that soil is the source to the atmosphere. Endosulfan was undergoing net deposition at most sites as it is a currently used pesticide. Other OCs showed wide variability in fugacity, suggesting a mix of net deposition and volatilization. Chemical profiles of residues and soil–air fugacities are used to assess the potential of soil as a source of organochlorine pesticides to the air of Mexico.

Critical loads (CLs) define maximum atmospheric deposition levels apparently preventative of ecosystem harm. We present first nitrogen CLs for northwestern North America’s maritime forests. Using multiple linear regression, we related epiphytic-macrolichen community composition to: 1) wet deposition from the National Atmospheric Deposition Program, 2) wet, dry, and total N deposition from the Communities Multi-Scale Air Quality model, and 3) ambient particulate N from Interagency Monitoring of Protected Visual Environments (IMPROVE). Sensitive species declines of 20-40% were associated with CLs of 1-4 and 3-9 kg N ha-1 y-1 in wet and total deposition. CLs increased with precipitation across the landscape, presumably from dilution or leaching of depositional N. Tight linear correlation between lichen and IMPROVE data suggests a simple screening tool for CL exceedance in US Class I areas. The total N model replicated several US and European lichen CLs and may therefore be helpful in estimating other temperate-forest lichen CLs. Lichen-based critical loads for N deposition in western Oregon and Washington forests ranged from 3 to 9 kg ha-1 y-1, increasing with mean annual precipitation.

The potential for storing additional C in U.S. Corn Belt soils – to offset rising atmospheric [CO2] – is large. Long-term cultivation has depleted substantial soil organic matter (SOM) stocks that once existed in the region's native ecosystems. In central Illinois, free-air CO2 enrichment technology was used to investigate the effects of elevated [CO2] on SOM pools in a conservation tilled corn–soybean rotation. After 5 and 6 y of CO2 enrichment, we investigated the distribution of C and N among soil fractions with varying ability to protect SOM from rapid decomposition. None of the isolated C or N pools, or bulk-soil C or N, was affected by CO2 treatment. However, the site has lost soil C and N, largely from unprotected pools, regardless of CO2 treatment since the experiment began. These findings suggest management practices have affected soil C and N stocks and dynamics more than the increased inputs from CO2-stimulated photosynthesis. Soil carbon from microaggregate-protected and unprotected fractions decreased in a conservation tilled corn–soybean rotation despite increases in primary production from exposure to atmospheric CO2 enrichment.

The effects of elevated concentrations of atmospheric tropospheric ozone (O3) on DNA damage in five trembling aspen (Populus tremuloides Michx.) clones growing in a free-air enrichment experiment in the presence and absence of elevated concentrations of carbon dioxide (CO2) were examined. Growing season mean hourly O3 concentrations were 36.3 and 47.3 ppb for ambient and elevated O3 plots, respectively. The 4th highest daily maximum 8-h ambient and elevated O3 concentrations were 79 and 89 ppb, respectively. Elevated CO2 averaged 524 ppm (+150 ppm) over the growing season. Exposure to O3 and CO2 in combination with O3 increased DNA damage levels above background as measured by the comet assay. Ozone-tolerant clones 271 and 8L showed the highest levels of DNA damage under elevated O3 compared with ambient air; whereas less tolerant clone 216 and sensitive clones 42E and 259 had comparably lower levels of DNA damage with no significant differences between elevated O3 and ambient air. Clone 8L was demonstrated to have the highest level of excision DNA repair. In addition, clone 271 had the highest level of oxidative damage as measured by lipid peroxidation. The results suggest that variation in cellular responses to DNA damage between aspen clones may contribute to O3 tolerance or sensitivity. Ozone tolerant clones and sensitive Populus tremuloides clones show differences in DNA damage and repair.

The aim of this study was to validate lichens as biomonitors of PAH atmospheric deposition; for that, an inter-comparison between the PAH profile and concentrations intercepted in lichens with those of air, soil and pine needles was performed. The study was conducted in a petro-industrial area and the results showed that PAH profiles in lichens were similar to those of the air and pine needles, but completely different from those of soils. Lichens accumulated higher PAH concentrations when compared to the other environmental compartments and its concentrations were significantly and linearly correlated with concentrations of PAHs in soil; we showed that a translation of the lichen PAHs concentrations into regulatory standards is possible, fulfilling one of the most important requirements of using lichens as biomonitors. With lichens we were then able to characterize the air PAHs profile of urban, petro-industrial and background areas. Lichen PAH concentrations can identify geographic areas that may be out of compliance with regulatory standards.

In urban cities in Southern China, the tissue S/N ratios of epilithic mosses (Haplocladium microphyllum), varied widely from 0.11 to 0.19, are strongly related to some atmospheric chemical parameters (e.g. rainwater SO42−/NH4+ ratios, each people SO2 emission). If tissue S/N ratios in the healthy moss species tend to maintain a constant ratio of 0.15 in unpolluted area, our study cities can be divided into two classes: class I (S/N > 0.15, S excess) and class II (S/N < 0.15, N excess), possibly indicative of stronger industrial activity and higher density of population, respectively. Mosses in all these cities obtained S and N from rainwater at a similar ratio. Sulphur and N isotope ratios in mosses are found significantly linearly correlated with local coal δ34S and NH4+–N wet deposition, respectively, indicating that local coal and animal NH3 are the major atmospheric S and N sources.

During the winters of 2006/2007 and 2007/2008, PM2.5 source apportionment programs were carried out within five western Montana valley communities. Filter samples were analyzed for mass and chemical composition. Information was utilized in a Chemical Mass Balance (CMB) computer model to apportion the sources of PM2.5. Results showed that wood smoke (likely residential woodstoves) was the major source of PM2.5 in each of the communities, contributing from 56% to 77% of the measured wintertime PM2.5. Results of 14C analyses showed that between 44% and 76% of the measured PM2.5 came from a new carbon (wood smoke) source, confirming the results of the CMB modeling. In summary, the CMB model results, coupled with the 14C results, support that wood smoke is the major contributor to the overall PM2.5 mass in these rural, northern Rocky Mountain airsheds throughout the winter months. This manuscript describes how woodsmoke is the largest source of PM2.5 in the Northern Rocky Mountains of the US.

Numerous experiments have demonstrated reductions in the yields of cereal crops due to tropospheric O3, with losses of up to 25%. However, the only British econometric study on O3 impacts on winter wheat yields, found that a 10% increase in AOT40 would decrease yields by only 0.23%. An attempt is made here to reconcile these observations by developing AOT40 maps for Great Britain and matching levels with a large number of standardised trial plot wheat yields from many sites over a 13-year period. Panel estimates (repeated measures on the same plots with time) show a 0.54% decrease in yields and it is hypothesised that plant breeders may have inadvertently selected for O3 tolerance in wheat. Some support for this is provided by fumigations of cultivars of differing introduction dates. A case is made for the use of econometric as well as experimental studies in prediction of air pollution induced crop loss.

The effect of elevated CO2 and O3 on apparent quantum yield (), maximum photosynthesis (Pmax), carboxylation efficiency (Vcmax) and electron transport capacity (Jmax) at different canopy locations was studied in two aspen (Populus tremuloides) clones of contrasting O3 tolerance. Local light climate at every leaf was characterized as fraction of above-canopy photosynthetic photon flux density (ÆPPFD). Elevated CO2 alone did not affect or Pmax, and increased Jmax in the O3-sensitive, but not in the O3-tolerant clone. Elevated O3 decreased leaf chlorophyll content and all photosynthetic parameters, particularly in the lower canopy, and the negative impact of O3 increased through time. Significant interaction effect, whereby the negative impact of elevated O3 was exaggerated by elevated CO2 was seen in Chl, N and Jmax, and occurred in both O3-tolerant and O3-sensitive clones. The clonal differences in the level of CO2 × O3 interaction suggest a relationship between photosynthetic acclimation and background O3 concentration. Photosynthetic acclimation to elevated CO2 depends on the background oxidant levels.