State Key Laboratory of Loess and Quaternary Geology of Earth Environment Academy of Sciences’an 710061;
CAS Center for Excellence in Quaternary Science and Global Change’an 710061;
Guanzhong Plain Ecological Environment Change and Comprehensive Treatment National Observation and Research Station’an 710061;
Xi’an Institute for Innovative Earth Environment Research’an 710061;
University of Chinese Academy of Sciences 100049;
Laboratory of Atmospheric Chemistry Scherrer Institute(PSI) 5232;
COVID-19; Brown carbon; Mass absorption cross-section; Radiative effects;