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

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

Inverse modeling of global and regional CH_4 emissions using SCIAMACHY satellite retrievals

Methane retrievals from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument onboard ENVISAT provide important information on atmospheric CH_4 sources, particularly in tropical regions which are poorly monitored by in situ surface observations. Recently, Frankenberg et al. (2008a, 2008b) reported a major revision of SCIAMACHY retrievals due to an update of spectroscopic parameters of water vapor and CH_4. Here, we analyze the impact of this revision on global and regional CH_4 emissions estimates in 2004, using the TM5-4DVAR inverse modeling system. Inversions based on the revised SCIAMACHY retrievals yield ∼20% lower tropical emissions compared to the previous retrievals. The new retrievals improve significantly the consistency between observed and assimilated column average mixing ratios and the agreement with independent validation data. Furthermore, the considerable latitudinal and seasonal bias correction of the previous SCIAMACHY retrievals, derived in the TM5-4DVAR system by simultaneously assimilating high-accuracy surface measurements, is reduced by a factor of ∼3. The inversions result in significant changes in the spatial patterns of emissions and their seasonality compared to the bottom-up inventories. Sensitivity tests were done to analyze the robustness of retrieved emissions, revealing some dependence on the applied a priori emission inventories and OH fields. Furthermore, we performed a detailed validation of simulated CH_4 mixing ratios using NOAA ship and aircraft profile samples, as well as stratospheric balloon samples, showing overall good agreement. We use the new SCIAMACHY retrievals for a regional analysis of CH_4 emissions from South America, Africa, and Asia, exploiting the zooming capability of the TM5 model. This allows a more detailed analysis of spatial emission patterns and better comparison with aircraft profiles and independent regional emission estimates available for South America. Large CH_4 emissions are attributed to various wetland regions in tropical South America and Africa, seasonally varying and opposite in phase with CH_4 emissions from biomass burning. India, China and South East Asia are characterized by pronounced emissions from rice paddies peaking in the third quarter of the year, in addition to further anthropogenic emissions throughout the year

Harmful Algal Blooms in Chinese Coastal Waters Will Persist Due to Perturbed Nutrient Ratios

The three large marine ecosystems (LMEs) bordering China (Yellow Sea/Bohai Sea, East China Sea, and South China Sea) have received excess nitrogen (N) and phosphorus (P) in the past decades with detrimental consequences for ecosystem functioning, such as increased productivity, loss of biodiversity, and proliferation of harmful algal blooms (HABs). N loading increased much faster than that of P. Here, we show that HABs in the three LMEs started to proliferate after the N:P molar ratio exceeded the threshold value of 25 in the 1980s. The mismatch of N and P inputs is not only related to differences in loads but also inherent to the differences in their biogeochemical cycles which more efficiently filter P than N in land- and waterscapes. Future Shared Socioeconomic Pathways show that high N:P ratios will persist for decades to come, even worsening in a future oriented toward sustainability, and indicate that HABs may be a persisting problem in China’s coastal waters. While efforts in agricultural systems are governed by the agronomic crop requirements and are not easy to manage with respect to N:P ratios, the separate collection of urine in urban and rural areas could contribute to decreases in both total nutrient loads and N:P ratios

Observations of aerosols in the free troposphere and marine boundary layer of the subtropical Northeast Atlantic: discussion of processes determining their size distribution

During July 1994, submicron aerosol size distributions were measured at two sites on Tenerife, Canary Islands. One station was located in the free troposphere (FT), the other in the marine boundary layer (MBL). Transport toward these two sites was strongly decoupled: the FT was first affected by dust and sulfate-laden air masses advecting from North Africa and later by clean air masses originating over the North Atlantic, whereas the MBL was always subject to the northeasterly trade wind circulation. In the FT the submicron aerosol distribution was predominantly monomodal with a geometric mean diameter of 120 nm and 55 nm during dusty and clean conditions, respectively. The relatively small diameter during the clean conditions indicates that the aerosol originated in the upper troposphere rather than over continental areas or in the lower stratosphere. During dusty conditions the physical and chemical properties of the submicron aerosol suggest that it has an anthropogenic origin over southern Europe and that it remains largely externally mixed with the supermicron mineral dust particles during its transport over North Africa to Tenerife. Apart from synoptic variations, a strong diurnal variation in the aerosol size distribution is observed at the FT site, characterized by a strong daytime mode of ultrafine particles. This is interpreted as being the result of photoinduced nucleation in the upslope winds, which are perturbed by anthropogenic and biogenic emissions on the island. No evidence was found for nucleation occurring in the undisturbed FT. The MBL site was not strongly affected by European pollution during the period of the measurements. The MBL aerosol size distribution was bimodal, but the relative concentration of Aitken and accumulation mode varied strongly. The accumulation mode can be related to cloud processing of the Aitken mode but also to pollution aerosol which was advected within the MBL or entrained from the FT. No bursts of nucleation were observed within the MBL

Contributions of nitrogen deposition and forest regrowth to terrestrial carbon uptake

<p>Abstract</p> <p>Background</p> <p>The amount of reactive nitrogen deposited on land has doubled globally and become at least five-times higher in Europe, Eastern United States, and South East Asia since 1860 mostly because of increases in fertilizer production and fossil fuel burning. Because vegetation growth in the Northern Hemisphere is typically nitrogen-limited, increased nitrogen deposition could have an attenuating effect on rising atmospheric CO₂by stimulating the vegetation productivity and accumulation of carbon in biomass.</p> <p>Results</p> <p>This study shows that elevated nitrogen deposition would not significantly enhance land carbon uptake unless we consider its effects on re-growing forests. Our results suggest that nitrogen enriched land ecosystems sequestered 0.62–2.33 PgC in the 1980s and 0.75–2.21 PgC in the 1990s depending on the proportion and age of re-growing forests. During these two decades land ecosystems are estimated to have absorbed 13–41% of carbon emitted by fossil fuel burning.</p> <p>Conclusion</p> <p>Although land ecosystems and especially forests with lifted nitrogen limitations have the potential to decelerate the rise of CO₂concentrations in the atmosphere, the effect is only significant over a limited period of time. The carbon uptake associated with forest re-growth and amplified by high nitrogen deposition will decrease as soon as the forests reach maturity. Therefore, assessments relying on carbon stored on land from enhanced atmospheric nitrogen deposition to balance fossil fuel emissions may be inaccurate.</p