Variations in the predicted spatial distribution of atmospheric nitrogen deposition and their impact on carbon uptake by terrestrial ecosystems

Widespread mobilization of nitrogen into the atmosphere from industry, agriculture, and biomass burning and its subsequent deposition have the potential to alleviate nitrogen limitation of productivity in terrestrial ecosystems, and may contribute to enhanced terrestrial carbon uptake. To evaluate the importance of the spatial distribution of nitrogen deposition for carbon uptake and to better quantify its magnitude and uncertainty NOy-N deposition fields from five different three-dimensional chemical models, GCTM, GRANTOUR, IMAGES, MOGUNTIA, and ECHAM were used to drive NDEP, a perturbation model of terrestrial carbon uptake. Differences in atmospheric sources of NOx-N, transport, resolution, and representation of chemistry, contribute to the distinct spatial patterns of nitrogen deposition on the global land surface; these differences lead to distinct patterns of carbon uptake that vary between 0.7 and 1.3 Gt C yr−1 globally. Less than 10% of the nitrogen was deposited on forests which were most able to respond with increased carbon storage because of the wide C:N ratio of wood as well as its long lifetime. Addition of NHx-N to NOy-N deposition, increased global terrestrial carbon storage to between 1.5 and 2.0 Gt C yr−1, while the “missing terrestrial sink” is quite similar in magnitude. Thus global air pollution appears to be an important influence on the global carbon cycle. If N fertilization of the terrestrial biosphere accounts for the “missing” C sink or a substantial portion of it, we would expect significant reductions in its magnitude over the next century as terrestrial ecosystems become N saturated and O3 pollution expands

Trend analysis from 1970 to 2008 and model evaluation of EDGARv4 global gridded anthropogenic mercury emissions

The Emission Database for Global Atmospheric Research (EDGAR) provides a time-series of man-made emissions of greenhouse gases and short-lived atmospheric pollutants from 1970 to 2008. Mercury is included in EDGARv4.tox1, thereby enriching the spectrum of multi-pollutant sources in the database. With an average annual growth rate of 1.3% since 1970, EDGARv4 estimates that the global mercury emissions reached 1287 tonnes in 2008. Specifically, gaseous elemental mercury (GEM) (Hg[superscript 0]) accounted for 72% of the global total emissions, while gaseous oxidised mercury (GOM) (Hg[superscript 2 +]) and particle bound mercury (PBM) (Hg-P) accounted for only 22% and 6%, respectively. The less reactive form, i.e., Hg[superscript 0], has a long atmospheric residence time and can be transported long distances from the emission sources. The artisanal and small-scale gold production, accounted for approximately half of the global Hg[superscript 0] emissions in 2008 followed by combustion (29%), cement production (12%) and other metal industry (10%). Given the local-scale impacts of mercury, special attention was given to the spatial distribution showing the emission hot-spots on gridded 0.1° × 0.1° resolution maps using detailed proxy data. The comprehensive ex-post analysis of the mitigation of mercury emissions by end-of-pipe abatement measures in the power generation sector and technology changes in the chlor-alkali industry over four decades indicates reductions of 46% and 93%, respectively. Combined, the improved technologies and mitigation measures in these sectors accounted for 401.7 tonnes of avoided mercury emissions in 2008. A comparison shows that EDGARv4 anthropogenic emissions are nearly equivalent to the lower estimates of the United Nations Environment Programme (UNEP)'s mercury emissions inventory for 2005 for most sectors. An evaluation of the EDGARv4 global mercury emission inventory, including mercury speciation, was performed using the GEOS-Chem global 3-D mercury model. The model can generally reproduce both spatial variations and long-term trends in total gaseous mercury concentrations and wet deposition fluxes.National Science Foundation (U.S.) (Atmospheric Chemistry Program Grant 1053648

Climate and Air Quality Impacts of Combined Climate Change and Air Pollution Policy Scenarios

This report describes an assessment of the co-benefits for air pollution of recently developed climate mitigation scenarios that inform the European Union policy making. The climate mitigation scenarios were obtained with the POLES equilibrium model for a business-as-usual and greenhouse gas reduction case. In the present work, these scenarios were expanded to air pollution emissions. The resulting set of global -spatially and sector disaggregated- air pollution emissions were evaluated with the global chemistry transport model TM5, to calculate levels of particulate matter and ozone. Subsequently, air pollution impacts on human health, ecosystems and climate were evaluated. The resulting set of four scenarios thus reflect various combinations of worldwide air pollution and climate policies: BAU (¿no further climate and air pollution policies since the 2000 base-year¿); CARB (¿climate policy only¿), BAP (¿no further climate policy, but progressive air pollution policies, to address worldwide increasing levels of air pollution) and CAP (¿combination of ambitious climate and air pollution policies¿). The implementation of a global climate policy (CARB) has substantial co-benefits for reducing air pollutant emissions. Compared to BAU, in 2050 global emissions of SO2 are reduced by ca. 75 %, NOx by 55 %, CO (40 %) and other pollutants VOC, OC and BC) about 25% %. These emission reductions result from cleaner technologies and decreased fuel demand, and correspond to a CO2 emission reduction of more than 60 %. Advanced air pollution abatement technologies can obtain similar air pollutant reductions ranging between 35 % (NOx), 45 % (OC, BC), 60 % (SO2) and 70% (CO), however in this case the CO2 emissions reach unabated levels of 55 Pg CO2/yr. The combined air pollution and climate policy case (CAP) further reduces BAP air pollution emissions by 10-30 %. Noticeable are the decreases of methane emissions by ca. 60 %, which have important impacts on ozone air quality and climate. The environmental benefits of the emission reductions are substantial. In 2050, average global life expectancy increases by 3.2 months/person for BAP (compared to BAU) and further increases by 3.7 to 6.9 months/person if additionally climate policies are introduced (CAP). Compared to 2000, only the CAP scenario leads to global improvement of life-expectancy (by about 3 months/person), while all other scenarios lead to higher particulate concentration and lower life expectancies, mainly driven by pollution developments in South and East Asia. These improvements in CAP are due to decreasing concentrations of primary (OC, BC) and secondary (SO4, NO3) aerosol. This work shows that combining air pollution and climate policies is in some regions the only way to stabilize or decrease the levels of air pollution and reducing impacts on human health. The global average life expectancy, however, masks large regional differences: e.g. current and future levels of air pollution in Asia are much larger than in Europe or the United States. Crop losses due to ozone are reduced by 4.7 % by implementing progressive air pollution policies, and could be reduced by another 2 %, by introducing additional climate policies. Climate policies target at limiting long-term (2100) climate change. On the intermediate time-scales (2030-2050), however, there might be important trade-offs to be considered in climate and air pollution policies, since reducing particulate matter and precursor (especially sulfur) emissions, are likely to lead to a net positive radiative forcing and a warming of climate. Since reductions of particulate matter and ozone are necessary to protect human health and vegetation, combined air pollution and climate policies are more beneficial for both climate and air pollution than stand-alone policies. There is scope to preferentially mitigate emissions of Black Carbon and methane, which is beneficial for climate and human health.JRC.DDG.H.2-Climate chang

What Can We Learn about Ship Emission Inventories from Measurements of Air Pollutants over the Mediterranean Sea?

Ship emission estimates diverge widely for all chemical compounds for several reasons: use of different methodologies (bottom-up or top-down), activity data and emission factors can easily result in a difference from a factor of 1.5 to two orders of magnitude. Despite these large discrepancies in existing ship emission inventories for air pollutants very little has been done to evaluate their consistency with atmospheric measurements at open sea. Combining three sets of observational data ¿ ozone and black carbon measurements sampled at three coastal sites and on board of a Mediterranean cruise ship, as well as satellite observations of atmospheric NO2 column concentration over the same area ¿ we assess the accuracy of the three most commonly used ship emission inventories, EDGAR FT (Olivier et al., 2005), emissions described by Eyring et al. (2005) and emissions reported by EMEP (Vestreng et al., 2007). Our tool is a global atmospheric chemistry transport model which simulates the chemical state of the Mediterranean atmosphere applying different ship emission inventories. The simulated contributions of ships to air pollutant levels in the Mediterranean atmosphere are significant but strongly depend on the inventory applied. Close to the major shipping routes relative contributions vary from 10 to 50% for black carbon and from 2 to 12% for ozone in the surface layer, as well as from 5 to 20% for nitrogen dioxide atmospheric column burden. The relative contributions are still significant over the North African coast, but less so over the South European coast. The observations poorly constrain the ship emission inventories in the Eastern Mediterranean where the influence of uncertain land based emissions, the model transport and wet deposition are at least as important as the signal from ships. In the Western Mediterranean, the regional EMEP emission inventory gives the best match with most measurements, followed by Eyring for NO2 and ozone and by EDGAR for black carbon. Given the uncertainty of the measurements and the model, each of the three emission inventories could actually be right, implying that large uncertainties in ship emissions need to be considered for future scenario analysis.JRC.H.2-Climate chang

Evaluating EDGARv4.tox2 speciated mercury emissions ex-post scenarios and their impacts on modelled global and regional wet deposition patterns

Speciated mercury gridded emissions inventories together with chemical transport models and concentration measurements are essential when investigating both the effectiveness of mitigation measures and the mercury cycle in the environment. Since different mercury species have contrasting behaviour in the atmosphere, their proportion in anthropogenic emissions could determine the spatial impacts. In this study, the time series from 1970 to 2012 of the EDGARv4.tox2 global mercury emissions inventory are described; the total global mercury emission in 2010 is 1772 tonnes. Global grid-maps with geospatial distribution of mercury emissions at a 0.1° × 0.1° resolution are provided for each year. Compared to the previous tox1 version, tox2 provides updates for more recent years and improved emissions in particular for agricultural waste burning, power generation and artisanal and small-scale gold mining (ASGM) sectors. We have also developed three retrospective emissions scenarios based on different hypotheses related to the proportion of mercury species in the total mercury emissions for each activity sector; improvements in emissions speciation are seen when using information primarily from field measurements. We evaluated them using the GEOS-Chem 3-D mercury model in order to explore the influence of speciation shifts, to reactive mercury forms in particular, on regional wet deposition patterns. The reference scenario S1 (EDGARv4.tox2_S1) uses speciation factors from the Arctic Monitoring and Assessment Programme (AMAP); scenario S2 (“EPA_power”) uses factors from EPA's Information Collection Request (ICR); and scenario S3 (“Asia_filedM”) factors from recent scientific publications. In the reference scenario, the sum of reactive mercury emissions (Hg-P and Hg 2+ ) accounted for 25.3% of the total global emissions; the regions/countries that have shares of reactive mercury emissions higher than 6% in total global reactive mercury are China+ (30.9%), India+ (12.5%) and the United States (9.9%). In 2010, the variations of reactive mercury emissions amongst the different scenarios are in the range of −19.3 t/yr (China+) to 4.4 t/yr (OECD_Europe). However, at the sector level, the variation could be different, e.g., for the iron and steel industry in China reaches 15.4 t/yr. Model evaluation at the global level shows a variation of approximately ±10% in wet deposition for the three emissions scenarios. An evaluation of the impact of mercury speciation within nested grid sensitivity simulations is performed for the United States and modelled wet deposition fluxes are compared with measurements. These studies show that using the S2 and S3 emissions of reactive mercury, can improve wet deposition estimates near sources

Fresh air in the 21st century?

Ozone is an air quality problem today for much of the world's population. Regions can exceed the ozone air quality standards (AQS) through a combination of local emissions, meteorology favoring pollution episodes, and the clean-air baseline levels of ozone upon which pollution builds. The IPCC 2001 assessment studied a range of global emission scenarios and found that all but one projects increases in global tropospheric ozone during the 21st century. By 2030, near-surface increases over much of the northern hemisphere are estimated to be about 5 ppb (+2 to +7 ppb over the range of scenarios). By 2100 the two more extreme scenarios project baseline ozone increases of >20 ppb, while the other four scenarios give changes of -4 to +10 ppb. Even modest increases in the background abundance of tropospheric ozone might defeat current AQS strategies. The larger increases, however, would gravely threaten both urban and rural air quality over most of the northern hemisphere

Atmospheric Organic Material and the Nutrients Nitrogen and Phosphorus It Carries to the Ocean

[1] The global tropospheric budget of gaseous and particulate non‐methane organic matter (OM) is re‐examined to provide a holistic view of the role that OM plays in transporting the essential nutrients nitrogen and phosphorus to the ocean. A global 3‐dimensional chemistry‐transport model was used to construct the first global picture of atmospheric transport and deposition of the organic nitrogen (ON) and organic phosphorus (OP) that are associated with OM, focusing on the soluble fractions of these nutrients. Model simulations agree with observations within an order of magnitude. Depending on location, the observed water soluble ON fraction ranges from ∼3% to 90% (median of ∼35%) of total soluble N in rainwater; soluble OP ranges from ∼20–83% (median of ∼35%) of total soluble phosphorus. The simulations suggest that the global ON cycle has a strong anthropogenic component with ∼45% of the overall atmospheric source (primary and secondary) associated with anthropogenic activities. In contrast, only 10% of atmospheric OP is emitted from human activities. The model‐derived present‐day soluble ON and OP deposition to the global ocean is estimated to be ∼16 Tg‐N/yr and ∼0.35 Tg‐P/yr respectively with an order of magnitude uncertainty. Of these amounts ∼40% and ∼6%, respectively, are associated with anthropogenic activities, and 33% and 90% are recycled oceanic materials. Therefore, anthropogenic emissions are having a greater impact on the ON cycle than the OP cycle; consequently increasing emissions may increase P‐limitation in the oligotrophic regions of the world\u27s ocean that rely on atmospheric deposition as an important nutrient source

Impacts of Intercontinental Transport of Anthropogenic Fine Particulate Matter on Human Mortality

Fine particulate matter with diameter of 2.5 microns or less (PM2.5) is associated with premature mortality and can travel long distances, impacting air quality and health on intercontinental scales. We estimate the mortality impacts of 20 % anthropogenic primary PM2.5 and PM2.5 precursor emission reductions in each of four major industrial regions (North America, Europe, East Asia, and South Asia) using an ensemble of global chemical transport model simulations coordinated by the Task Force on Hemispheric Transport of Air Pollution and epidemiologically-derived concentration-response functions. We estimate that while 93-97 % of avoided deaths from reducing emissions in all four regions occur within the source region, 3-7 % (11,500; 95 % confidence interval, 8,800-14,200) occur outside the source region from concentrations transported between continents. Approximately 17 and 13 % of global deaths avoided by reducing North America and Europe emissions occur extraregionally, owing to large downwind populations, compared with 4 and 2 % for South and East Asia. The coarse resolution global models used here may underestimate intraregional health benefits occurring on local scales, affecting these relative contributions of extraregional versus intraregional health benefits. Compared with a previous study of 20 % ozone precursor emission reductions, we find that despite greater transport efficiency for ozone, absolute mortality impacts of intercontinental PM2.5 transport are comparable or greater for neighboring source-receptor pairs, due to the stronger effect of PM2.5 on mortality. However, uncertainties in modeling and concentration-response relationships are large for both estimates