Aerosol composition (IMAGE) Science China Press Caption (a)Variation of mass concentration in NR-PM1 and (b) mass fraction of organic, nitrate, sulfate, ammonium and chloride during heating seasons in Beijing from 2013 to 2017 Credit ©Science China Press Usage Restrictions Use with credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.