Humidity and PM2.5 composition determine atmospheric light extinction in the arid region of northwest China

• 作者: Xiaoxiao Zhang Xiang Ding Dilinuer Talifu Xinming Wang Abulikemu Abulizi Mailikezhati Maihemuti Suwubinuer Rekefu
• 来源期刊: 环境科学学报（英文版）
• 年，卷（期）: 2021,（2）
• 页码范围: 279-286
• 页数: 8页
• 语种: 英文

摘要

Atmospheric visibility can directly reflect the air quality.In this study,we measured water-soluble ions(WSIs),organic and element carbon(OC and EC)in PM2.5 from September 2017 to August 2018 in Urumqi,NW China.The results show that SO42-,NO3-and NH4+were the major WSIs,together accounting for 7.32％-84.12％of PM2.5 mass.Total carbon(TC=OC+EC)accounted for 12.12％of PM2.5 mass on average.And OC/EC ＞ 2 indicated the formation of secondary organic carbon(SOC).The levels of SO42-,NO3-and NH4+in low visibility days were much higher than those in high visibility days.Relative humidity(RH)played a key role in affecting visibility.The extinction coefficient(bext)that estimated via Koschmieder formula with visibility was the highest in winter(1441.05 ± 739.95 Mm-1),and the lowest in summer(128.58 ± 58.00 Mm-1).The bext that estimated via IMPROVE formula with PM2.5 chemical component was mainly contributed by(NH4)2SO4 and NH4NO3.The bext values calculated by both approaches presented a good correlation with each other(R2 = 0.87).Multiple linear regression(MLR)method was further employed to reconstruct the empirical regression model of visibility as a function of PM2.5 chemical components,NO2 and RH.The results of source apportionment by Positive Matrix Factorization(PMF)model showed that residential coal combustion and vehicle emissions were the major sources of bext.