Chemical characterization and source identification of PM_(2.5) in Luoyang after the clean air actions

摘要

Luoyang is a typical heavy industrial city in China,with a coal-dominated energy structure and serious air pollution.Following the implementation of the clean air actions,the physic-ochemical characteristics and sources of PM_(2.5) have changed.A comprehensive study of PM_(2.5) was conducted from October 16,2019 to January 23,2020 to evaluate the effectiveness of previous control measures and further to provide theory basis for more effective policies in the future.Results showed that the aerosol pollution in Luoyang in autumn and win-ter is still serious with the average concentration of 91.1 μg/m^(3),although a large reduction(46.9%)since 2014.With the contribution of nitrate increased from 12.5%to 25.1%and sul-fate decreased from 16.7%to 11.2%,aerosol pollution has changed from sulfate-dominate to nitrate-dominate.High NO_(3)^(-)/SO_(4)^(2-)ratio and the increasing of NO_(3)^(-)/SO_(4)^(2-)ratio with the aggravation of pollution indicating vehicle exhaust playing an increasingly important role in PM_(2.5) pollution in Luoyang,especially in the haze processes.Secondary inorganic ions contributed significantly to the enhancement of PM_(2.5) during the pollution period.The high value of Cl^(-)/Na^(+)and EC concentration indicate coal combustion in Luoyang is still serious.The top three contributor sources were secondary inorganic aerosols(33.3%),coal combus-tion(13.6%),and industrial emissions(13.4%).Close-range transport from the western and northeastern directions were more important factors in air pollution in Luoyang during the sampling period.It is necessary to strengthen the control of coal combustion and reduce vehicle emissions in future policies.