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ENVR Seminar: Spatial Distribution of Nitrogen (N) + Sulfur (S) Deposition and its Exceedance in US: From Present to Future

Date: Thursday, September 14

Time: 3:30 pm - 5:00 pm

Location: 410 John D. Tickle Building

 

Abstract:

Nitrogen (N) and sulfur (S) deposition are much mitigated over the conterminous US (CONUS) but deposition exceedance still exists on forest soil. In addition, the empirical approach is usually used but only provides a spatially constant critical load (CL). Therefore, the CL derived from steady-state mass balance equation is used to study the CL exceedance on forest soil over the CONUS. The multi-model mean (MMM) of global climate-chemistry models in 2000s indicates that total (wet + dry) N deposition alone over 10.32% of forest soil exceeds the CL, but a higher percent (30.16%) is observed by the N+S deposition, which highlights the necessity of considering S deposition. In 2050s, less CL exceeded forest soil is projected and the exceedance amount is lower as well, mainly attributed to the strong reduction of projected NOX and SO2 emissions. By firstly projecting the future CL due to the climate change, the CL exceedance could further decrease since the air temperature is projected to increase rapidly and lead to higher CL in the future. The CL exceedance by N deposition alone is likely to be dominated by NOy in 2000s but NHX in 2050s because of the enhanced NH3 emission. Moreover, both in 2000s and 2050s, using the CL generated by different aggregation methods can cause up to 33 times difference between the corresponding CL exceedance. This suggests that several regions are under the marginal threat of either N or N+S deposition and different CL can influence the results significantly.

Abstract:

Nitrogen (N) and sulfur (S) deposition are much mitigated over the conterminous US (CONUS) but deposition exceedance still exists on forest soil. In addition, the empirical approach is usually used but only provides a spatially constant critical load (CL). Therefore, the CL derived from steady-state mass balance equation is used to study the CL exceedance on forest soil over the CONUS. The multi-model mean (MMM) of global climate-chemistry models in 2000s indicates that total (wet + dry) N deposition alone over 10.32% of forest soil exceeds the CL, but a higher percent (30.16%) is observed by the N+S deposition, which highlights the necessity of considering S deposition. In 2050s, less CL exceeded forest soil is projected and the exceedance amount is lower as well, mainly attributed to the strong reduction of projected NOX and SO2 emissions. By firstly projecting the future CL due to the climate change, the CL exceedance could further decrease since the air temperature is projected to increase rapidly and lead to higher CL in the future. The CL exceedance by N deposition alone is likely to be dominated by NOy in 2000s but NHX in 2050s because of the enhanced NH3 emission. Moreover, both in 2000s and 2050s, using the CL generated by different aggregation methods can cause up to 33 times difference between the corresponding CL exceedance. This suggests that several regions are under the marginal threat of either N or N+S deposition and different CL can influence the results significantly.

 

Short bio:

Jian Sun is a Phd Candidate from Dr. Joshua S. Fu’s group at the Department of Civil & Environmental Engineering. The focus of his doctoral dissertation is about the model development of global chemistry-climate model including convergence test, accuracy analysis and computational optimization. He has also been involved in other research projects such as the climate-driven exceedance of N and S deposition in US, the assessment of pollutant-related (ozone and PM2.5) health risk in a changing climate and the estimation of control cost for multi-pollutants from the power sectors in China.

Tags: ENVR Seminar

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