A 15-year record (2001-2015) of the ratio of nitrate to non-sea-salt sulfate in precipitation over East Asia
A 15-year record (2001-2015) of the ratio of nitrate to non-sea-salt sulfate in precipitation over East Asia
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DOI：
10.5194/acp-18-2835-2018
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发表时间：
2018-02-28
影响因子：
6.3
通讯作者：
Wang, Yuesi
中科院分区：
文献类型：
--
作者：
Itahashi, Syuichi;Yumimoto, Keiya;Wang, Yuesi
降水中的酸化物质可对生态系统产生严重影响。降水的化学成分与降水量直接相关;因此，很难确定化学浓度的长期变化。硝酸盐（NO3-）/非海盐硫酸盐（nss-SO24）/降水浓度的比值（以下简称比值）是研究这些酸化物种相对贡献的有用指标。为了确定全球排放量最高的东亚地区降水中酸化物种的长期记录，我们根据东亚酸沉降监测网络（EANET）编制了2001年至2015年中国，韩国和日本降水化学成分的地面观测结果。空间覆盖范围有限，但利用了日本、中国南部和北京周围北方的额外监测数据。分析期分为三个阶段：第一阶段（2001-2005）、第二阶段（2006-2010）和第三阶段（2011-2015）。NO3-和nss-SO 42-浓度的行为以及降水中的比值与这些前体物有关。分析了人为排放的NOx和SO2以及NOx = SO2的排放比例。此外，卫星观测的NO2和SO2柱密度，以捕捉排放量的变化。结果表明，降水中NO3-浓度的长期变化趋势与NOx排放量和NO2柱的变化无关。相比之下，中国，韩国和日本降水中的nss-SO 42-浓度与中国SO2排放量的变化有部分联系，但趋势并不显著。中国、韩国和日本的长期趋势在第一阶段几乎持平，在第二阶段显著增加，在第三阶段基本持平。东亚地区NOx = SO2排放比和NO2 = SO2气柱比的变化与中国的NOx = SO2排放比和NO2 = SO2气柱比明显对应。第一阶段的初始平稳趋势是由于中国NOx和SO2排放量的增加，第二阶段的显著增加趋势是由于中国NOx排放量的增加和SO2排放量的减少，第三阶段的恢复平稳趋势是由于中国NOx和SO2排放量的减少。这些结果表明，在2001-2015年的15年期间，中国的排放不仅对中国而且对顺风降水化学产生了重大影响。在湿沉降方面，NO3-湿沉降在中国，韩国和日本没有显着变化，但nss-SO 42-湿沉降下降在中国，韩国和日本从第二阶段到第三阶段。这些下降是由于降水中nss-SO 42-浓度的强烈下降，伴随着中国SO2排放量的减少，抵消了降水的增加。这些结果表明，降水的酸度从硫转移到氮。
Acidifying species in precipitation can have severe impacts on ecosystems. The chemical composition of precipitation is directly related to the amount of precipitation; accordingly, it is difficult to identify long-term variation in chemical concentrations. The ratio of the nitrate (NO3-/to non-sea-salt sulfate (nss-SO24/concentration in precipitation on an equivalent basis (hereinafter, Ratio) is a useful index to investigate the relative contributions of these acidifying species. To identify the long-term record of acidifying species in precipitation over East Asia, the region with the highest emissions worldwide, we compiled groundbased observations of the chemical composition of precipitation over China, Korea, and Japan from 2001 to 2015 based on the Acid Deposition Monitoring Network in East Asia (EANET). The spatial coverage was limited, but additional monitoring data for Japan, southern China, and northern China around Beijing were utilized. The period of analysis was divided into three phases: Phase I (2001-2005), Phase II (2006-2010), and Phase III (2011-2015). The behaviors of NO3- and nss-SO42- concentrations and hence the Ratio in precipitation were related to these precursors. The anthropogenic NOx and SO2 emissions and the NOx = SO2 emission ratio were analyzed. Further, satellite observations of the NO2 and SO2 column density to capture the variation in emissions were applied. We found that the longterm trend in the NO3- concentration in precipitation was not related to the variation in NO x emission and the NO2 column. In comparison, the nss-SO42- concentration in precipitation over China, Korea, and Japan was partially connected to the changes in SO2 emissions from China, but the trends were not significant. The long-term trends of Ratio over China, Korea, and Japan were nearly flat during Phase I, increased significantly during Phase II, and were essentially flat again during Phase III. This variation in Ratio in East Asia clearly corresponded to the NOx = SO2 emission ratio and the NO2 = SO2 column ratio in China. The initial flat trend during Phase I was due to increases in both NOx and SO2 emissions in China, the significantly increasing trend during Phase II was triggered by the increase in NOx emissions and decrease in SO2 emissions in China, and the return to a flat trend during Phase III was caused by declines in both NOx and SO2 emissions in China. These results suggest that emissions in China had a significant impact not only on China but also on downwind precipitation chemistry during the 15-year period of 2001-2015. In terms of wet deposition, the NO3- wet deposition over China, Korea, and Japan did not change dramatically, but the nss-SO42- wet deposition declined over China, Korea, and Japan from Phase II to III. These declines were caused by a strong decrease in the nss-SO42- concentration in precipitation accompanied by a reduction in SO2 emission from China, which counteracted the increase in precipitation. These findings indicated that the acidity of precipitation shifted from sulfur to nitrogen.