Fluxes and sources of metals deposited in dew in Changchun, China

Abstract

Because of the recent expansion of industrialization and urbanization, the concentration of metals in the atmosphere has significantly increased. Considering the threats of wet metal deposition to the water and soil quality, many studies have primarily focused on wet metal deposition in rain or snow, but there are few reports considering dew. As an important factor of wet deposition, dew cannot be ignored when assessing wet metal deposition. To analyze the fluxes and sources of metals deposited on Hemiptelea davidii (Hance) Planch via dew, dew samples were collected over six months in Changchun from May to October 2021, and the concentrations of 12 metals were measured. The order of both the volume-weighted mean (VWM) concentrations and fluxes of the measured metals were Ca > Na > Mg > K > Al > Fe > Zn > Pb > As > Mn > Cu > Ni. Ca was the most abundant metal, with a VWM concentration and wet flux of 6156.74 ± 1807.69 μg/L and 218.87 mg/m2·y, respectively, which were 3 orders of magnitude higher than those of Pb, As, Mn, Cu, and Ni. Based on correlation and principal component analysis, the metals in dew originated from both natural sources (Ca, Na, Mg, Al, Mn, Fe, and K) and anthropogenic activities (Cu, Ni, Pb, Zn, and As). Combined with the analysis of air mass trajectories, fire maps and microstructure characteristics of particles within dew, it was determined that the metals in dew were mainly sourced from crustal dust, straw burning, vehicle exhaust and coal combustion. Additionally, the determined metals could be attributed to a mixture of long range transport and local sources.