基于硫碳同位素研究南京北郊冬季霾事件中PM_(2.5)来源

Investigations on PM_(2.5) Sources in Winter Haze Event in the Northern Suburb of Nanjing Based on Sulfur and Carbon Isotope

2015年12月27日—2016年1月6日,针对南京北郊地区一次霾事件所采PM_(2.5)样品,测定样品中水溶性离子、硫同位素与碳同位素组分含量。水溶性离子研究结果表明:该次霾事件以二次污染为主且移动源占主要地位。硫同位素分析结果表明:硫酸盐的δ^(34)S(SO_4^(2-))值的范围为4.4‰~6.8‰,平均值为5.7‰±0.7‰(n=11),结合该地潜在硫源可知,此次霾事件中硫酸盐气溶胶主要来源为机动车尾气及煤炭燃烧。PM_(2.5)中的δ^(13)C值变化范围为-28.43‰^-24.94‰,平均值为-26.62‰±1.11‰,说明碳质污染物来源主要为机动车尾气、燃煤。此外,硫、碳同位素具有较好的负相关性,结合潜在硫源、碳源可知,2016年1月1日之前,南京北郊地区大气污染源以汽油车尾气排放为主;1月1日之后大气污染源以柴油车尾气和燃煤排放为主。

From December 27,2015 to January 6,2016,PM2.5 samples were taken from a haze event in the northern region of Nanjing,and the content of water-soluble ions,sulfur isotopes,and carbon isotope components were measured. The results of water-soluble ion composition showed that this event was dominated by secondary pollution and the mobile source of this event was dominant. The results of sulfur isotope analysis showed that the δ^34S（ SO4^2-） value of sulfate in this event was in the range of4. 4‰-6. 8‰,with an average of 5. 7‰ ± 0. 7‰（ n = 11）. Based on the local potential sulfur source,the main sources of sulfate aerosol in the event were motor vehicle exhaust and coal combustion. The δ^13C values in PM2.5 ranged from-28. 43‰ to-24. 94‰,with an average of-26. 62‰ ± 1. 11‰. Combined with relevant data,the source of heavy carbon isotopes was mainly motor vehicle exhaust and coal-fired pollution. Analysis of sulfur and carbon isotope relationships in this event showed that the two had a high negative correlation. Combined with potential sulfur sources and carbon sources,it was known that before January 1,2016 the atmospheric pollution source in Nanjing had a lower δ^13C value. Exhaust gas dominates,and the source of atmospheric pollution after January 1 was motor vehicle exhaust and coal-fired.