Capture of heavy metals and sulfur by foliar dust in urban Huizhou, Guangdong Province, China

Foliar dust on urban tree leaf surfaces in Huizhou (HZ) in Guangdong Province of China was studied for a range of elements. The concentrations of the heavy metals (Cd, Cr, Cu, Pb, Zn) and sulfur in the foliar dust were determined by ICP-AES. Remote sensing imaging was used to estimate the total aboveground urban vegetation biomass in Huizhou, information that was then used to estimate the total removal of air particulates in the city by foliar dust.The results showed that the heavy metal concentrations in foliar dust were high, particularly for Cd and Pb. Concentrations of Cd ranged from 6.2 to 12.8 mg kg−1, while concentrations of Pb ranged from 434.0 to 512.0 mg kg−1. The amount of foliar dust retained by the four tree species increased with time for 20 d following a rain event. The amount of foliar dust collected from different locations in the city was significantly different. Specifically, the heavy metal and sulfur pollution index in the different locations decreased in this order: Power Station (PS) > Electronic Industry Area (EIA) > Commercial and Traffic Area (CTA) > Residential Areas (RA) > Control Area (CA). These data suggest that the foliar dust can remove appreciable amounts of Cd, Cr, Cu, Pb, Zn, and S – 0.040 t, 1.63 t, 2.70 t, 1.84 t, 5.54 t, and 19.52 t, respectively – from the atmosphere in the study area. This information can provide health-related impetus and guidance for the work of urban planners and those involved in environment protection.