A meta-analysis on particulate matter-associated heavy metals in rural air: Concentration, seasonal variability, and...

Heavy metals (HMs) bonded to PM (Particulate Matter) are a significant component of rural air pollution. They're primarily released from fossil fuel combustion and the operational decay of automobiles, leading to their considerable presence in roadway dust. This study aims to examine the concentration and seasonal effects on HM emissions in rural air. The pooled mean concentrations for As (7.81 ng m^-³), Cd (4.42 ng m^-³), and Pb (60.97 ng m^-³) were statistically significant. Pb concentrations were exceptionally high in some rural areas of China, with mean values over 500 ng m^-³ reported in two studies. Studies showed notably high levels of Pb, Cu, and Zn, with some sites having exceptional concentrations. The analysis also found significant seasonal variations, with many HMs showing higher concentrations in winter, which is likely due to increased coal combustion for heating. Seasonal analysis in China revealed higher concentrations of several HMs in winter, likely due to increased coal combustion for heating. In spring, road and soil dust from natural phenomena such as dust storms was a primary source of HMs.