The regional nature of nitrate-dominant haze pollution during autumn over the Pearl River Delta area

Abstract

China has experienced severe haze and visibility degradation problems in recent years because of rapid urbanization and industrialization. In this study, daily atmospheric fine-aerosol samples were concurrently collected at three sites over the Pearl River Delta (PRD) region during 1-29 October 2014. PM 2.5 samples were analyzed for organic carbon and elemental carbon using a thermal/ optical carbon analyzer. Major water-soluble inorganic ions including F − , Cl − , NO 3 − , SO 4 2− , Na + , NH 4 + , K + , Mg 2+ , and Ca 2+ were analyzed by ion chromatography. The results show that the temporal variations of PM 2.5 concentration at the three sites were highly parallel, with particle pollution events simultaneously observed during 13-19 October (EP1) and 23-27 October (EP2), suggesting that pollution events in the PRD region are usually regional. This can most likely be attributed to the significant influences of synoptic conditions, which regionally facilitate or block diffusion of air pollutants. The chemical compositions of PM 2.5 at the three sites were also found to be similar, dominated by organics and sulfates. The results indicate that accumulation of traffic emissions seems to play important roles in particle pollution for the PRD region, leading in this case to elevated nitrate contributions during both EP1 and EP2 at the three sites. Moreover, the authors found that locally emitted aerosols from biomass burning only markedly influenced the air condition at one site, Nanhai, during EP1, while regionally transported biomass burning aerosols from eastern and northern Guangdong Province influenced all three sampling sites when the PRD was dominated by polluted air from these directions during EP2. 珠三角秋季硝酸盐气溶胶致霾污染的区域性特征 摘要 为研究珠三角地区大气霾污染特征和形成机制, 于2014年秋季在区域内三个典型观测站同步开

Toward a better understanding of cascading consequences of atmospheric reactive nitrogen along its transport pathway

“…found that 91% of fire points in Northeast China from 2003 to 2017 were from croplands, and mainly occurred during March-April (37%) and October-November (46%). In the Pearl River Delta region, Guo et al (2020) observed the linkage between severe haze episodes and biomass burning during October 2014. They also found a regional feature of haze pollution, with periodically elevated nitrate aerosols.…”