Responses of nitrogen and sulfur deposition to NH3 emission control in the Yangtze River Delta, China
2022
Dong, Zhaoxin | Xing, Jia | Wang, Shuxiao | Ding, Dian | Ge, Xiaodong | Zheng, Haotian | Jiang, Yueqi | An, Jingyu | Huang, Cheng | Duan, Lei | Hao, Jiming
NH₃ emission control has proven to be of great importance in reducing PM₂.₅ concentrations in China, while how it affects nitrogen/sulfur (N/S) deposition is still unclear. This study expanded the response surface model method to quantify the responses of N/S deposition to the emission control of precursors (NOₓ, SO₂, NH₃, VOCs and primary PM₂.₅) in the Yangtze River Delta, China. NH₃ control was found to have higher efficiency in reducing N/S deposition than NOₓ and SO₂ alone. The reduced N deposition response to NH₃ emission control was higher in the northern part of the YRD region, whereas oxidized N deposition decreased sharply in the region with a low N critical load. Synergetic effect was found in reducing N deposition when we controlled the NH₃ and NOₓ emissions simultaneously. Compared with the sum effect of individual NH₃ and NOₓ emission control, the extra benefits from the synergy controls accounted for 4.4% (1.23 kg N·ha⁻¹·yr⁻¹) of the total N deposition, of which 81% came from the oxidized N deposition. The YRD region could receive the largest synergetic effect with a 1:1 ratio of NOₓ:NH₃ emission reduction. The NH₃ emission control increases the dry deposition of acid substances and worsens acid rain though it reduces the wet S/oxidized N deposition. These findings highlight the effectiveness of NH₃ emission control and suggest a multi-pollutant control strategy for reducing N/S deposition. The response surface model method for deposition also provides a reference for other regions in China and other countries.
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