西安冬季元素碳气溶胶的碳同位素组成及来源变化

Fine particulate matter (PM_{2. 5} ) play an important role in climate and human health. The element carbon (EC) in PM_{2. 5} doesn’t react in atmosphere, so its sources can indicate the change of primary combustion sources. This work aims to identify the sources of EC in winter of Xi’an in 2008 / 2009 and 2015 / 2016 by combining the method of stable carbon isotope (¹³C) and radioactive carbon isotope (¹⁴C). The ¹⁴C results demonstrate that EC was dominated by fossil sources in 2008 / 2009 and 2015 / 2016, with a mean contribution of 77% ±4% and 72% ±5%. ¹³C composition of EC was more enriched in 2008 / 2009 (- 23. 72% ~ - 22. 81%, - 23. 22% ± 0. 39%) compared to that in 2015 / 2016 (-25. 04% ~ -24. 64 %,-24. 80%±0. 21%), indicating the influence of coal combustion in 2008 / 2009 and liquid fossil fuel combustion in 2015 / 2016. By combining ¹⁴C and ¹³C signatures, the change of EC emission sources was significant of Xi’an in the past decade, it was found that the relative contributions from coal combustion to EC decreased, and vehicle emission to EC increased respectively. This is related to the change of coal to gas and the rapid increase of motor vehicles population.