Abstract
Abstract. This study uses multi-model ensemble results of 11 models from the second phase of Task Force Hemispheric Transport of Air Pollution (HTAP II) to calculate the global sulfur (S) and nitrogen (N) deposition in 2010. Modeled wet deposition is evaluated with observation networks in North America, Europe and East Asia. The modeled results agree well with observations, with 76–83 % of stations being predicted within ±50 % of observations. The models underestimate SO42-, NO3- and NH4+ wet depositions in some European and East Asian stations but overestimate NO3- wet deposition in the eastern United States. Intercomparison with previous projects (PhotoComp, ACCMIP and HTAP I) shows that HTPA II has considerably improved the estimation of deposition at European and East Asian stations. Modeled dry deposition is generally higher than the “inferential” data calculated by observed concentration and modeled velocity in North America, but the inferential data have high uncertainty, too. The global S deposition is 84 Tg(S) in 2010, with 49 % in continental regions and 51 % in the ocean (19 % of which coastal). The global N deposition consists of 59 Tg(N) oxidized nitrogen (NOy) deposition and 64 Tg(N) reduced nitrogen (NHx) deposition in 2010. About 65 % of N is deposited in continental regions, and 35 % in the ocean (15 % of which coastal). The estimated outflow of pollution from land to ocean is about 4 Tg(S) for S deposition and 18 Tg(N) for N deposition. Comparing our results to the results in 2001 from HTAP I, we find that the global distributions of S and N deposition have changed considerably during the last 10 years. The global S deposition decreases 2 Tg(S) (3 %) from 2001 to 2010, with significant decreases in Europe (5 Tg(S) and 55 %), North America (3 Tg(S) and 29 %) and Russia (2 Tg(S) and 26 %), and increases in South Asia (2 Tg(S) and 42 %) and the Middle East (1 Tg(S) and 44 %). The global N deposition increases by 7 Tg(N) (6 %), mainly contributed by South Asia (5 Tg(N) and 39 %), East Asia (4 Tg(N) and 21 %) and Southeast Asia (2 Tg(N) and 21 %). The NHx deposition increases with no control policy on NH3 emission in North America. On the other hand, NOy deposition has started to dominate in East Asia (especially China) due to boosted NOx emission.
Highlights
Nitrogen (N) plays an important role in the balance of the global ecosystem
We evaluate the multi-model mean (MMM) results of SO24−, NO−3 and NH+4 wet deposition with site observations in the United States, Europe and East Asia
The model performance on wet deposition is evaluated with the measurement networks National Atmospheric Deposition Program (NADP) over North America, European Monitoring and Evaluation Programme (EMEP) over Europe and EANET over East Asia
Summary
Nitrogen (N) plays an important role in the balance of the global ecosystem. The most affected regions are eastern Europe (80 %), South Asia (60 %) and East Asia (40– 50 %) This percentage will be 40 % for the world’s protected areas in 2030 (Bleeker et al, 2011). Elevated S and N deposition are associated with a host of environmental issues such as acidification and eutrophication of the terrestrial system (Bouwman et al, 2002), loss of ecosystem biodiversity (Bobbink et al, 2010), harming heterotrophic respiration and disturbing the soil decomposition process (Janssens et al, 2010), some studies have found that increasing N deposition could benefit the carbon uptake by land processes (Reay et al, 2008; Holland et al, 1997). Similar to the terrestrial system, over-richness of S and N deposition are threats to the aquatic system by acidification (Doney et al, 2007) and eutrophication of the ocean (Bergstrom and Jansson, 2006; Jickells, 2006; Jickells et al, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
