Effects of heating activities in winter on characteristics of PM_2.5-bound Pb, Cd and lead isotopes in cities of China

Fossil fuel combustion was often mentioned as the most important source of air pollution, but coal-fired heating was rarely isolated to discuss its impact on air quality. In winter, the northern part of China will carry out a large area of continuous coal-fired heating activities, which contributes to a high degree of heavy metals in PM_2.5. And combined with the liquidity of atmospheric particles, tends to create regional and even international problems. But many air control policies ignore this control measure. Twenty-five representative cities in heating and non-heating area in China were selected for spatial difference analysis of PM_2.5-bound Pb and Cd. In addition, using the HYSPLIT model and Pb isotope ratios to verify whether coal-fired heating in heating areas (Tianjin) contribute to heavy metals in atmospheric particulate matter in non-heating areas (Shanghai). Results showed that the average Pb and Cd concentrations in the heating cities were 3.5 and 2.9 times of those in the non-heating cities, respectively. Long-distance transportation would affect the concentrations of PM_2.5 in Shanghai and Tianjin, while coal-fired emissions from heating cities had a greater impact on PM_2.5-bound heavy metal concentrations in non-heating cities. Therefore, cross-border environmental impact assessments need to be standardized, and monitoring of regional activities need to be strengthened.