Chemical composition and light absorption characteristics of brown carbon in Yuncheng in Winter
In order to better explore the problem of air pollution in urban areas in China,a four-channel sampler was used to collect fine particulate matter(PM2.5)samples daily in Yuncheng City,Shanxi Province from October 15,2019 to March 1,2020.The concentrations of organic carbon(OC),elemental carbon(EC),water-soluble organic carbon(WSOC)and water-soluble ions in the samples were analyzed,and the light absorption of methanol extract and water extract were compared.The results showed that the concentration of PM2.5 varied from 6.21 μg·m-3 to 325 μg·m-3 during the sampling period.41 d reached the standard of mild pollution or above stipulate in the Technical Provisions of Ambient Air Quality Index(AQI)(HJ 633-2012),accounting for 64％of the total days,indicating that air pollution in Yuncheng was very serious in winter.Secondary inorganic water-soluble ions and organic matter were the main components of PM2.5,accounting for 39.6％and 29.7％(fine days),38.9％and 30.8％(moderate pollution),40.4％and 29.1％(heavy pollution),38.9％and 26.5％(serious pollution)of PM2.5 mass concentration,respectively.NO3-was the highest species,and the ratios of NO3-/SO42-in the four periods were 2.15,2.11,2.31 and 1.93,respectively,indicating that NOx from motor vehicle exhaust was the main source of NO3-.The optical parameters,Abs,AAE and MAE of water-soluble brown carbon(WSBrC)and methanol extractable brown carbon(MSBrC)at 365 nm showed that the absorption efficiency of the unit extracted by methanol was higher than that of the water extract at all stages.The linear fit between MSBrC and SOC showed Abs365,M,SOC(r=0.80)and POC(r=0.69),indicating that secondary photochemical reactions were the main source of BrC.
fine particlechemical compositionbrown carbonlight absorption propertiessource
NETL
NSTL
万方数据
