Assessment of Fluxes and Ecological and Health Risks of Toxic Trace Elements in Atmospheric Deposition from the Baicheng-Songyuan Area, Jilin Province, Northeast China

A total of 56 atmospheric deposition samples were collected on a yearly basis from the Baicheng-Songyuan areas, Jilin Province, Northeast China. Each sample was subdivided into wet (soluble) and dry (insoluble) fractions, and the concentrations of toxic trace elements including As, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Se, and Zn in both fractions were analyzed. The bulk fluxes and ecological and human health risk of these toxic trace elements in atmospheric deposition were evaluated. The bulk deposition fluxes of toxic trace elements decreased in the order of Mn > Zn > Cr > Pb > Cu > Ni > As > Co >Mo > Cd > Se > Hg. The fluxes of toxic trace elements in dry fraction accounted for 74.7-99.9% of their bulk deposition fluxes, indicating that the atmospheric deposition of toxic trace elements in the study area is predominantly dry atmospheric deposition. The mean values of the geo-accumulation index (Igeo) and enrichment factor showed moderately heavy contamination with Cd via dry atmospheric deposition, but no contamination from other toxic trace elements; Cd and Hg in dry atmospheric deposition were in the moderate to considerable ecological risk levels, while other trace elements were at low ecological risk levels. The health risk assessment showed that the effects of toxic trace elements in dry atmospheric deposition via three exposure pathways were in the order of ingestion > inhalation > dermal contact for adults and children. The mean values of hazard quotient (HQ) and hazard index (HI) of toxic trace elements via three pathways were less than one, indicating that their non-carcinogenic risks in dry atmospheric deposition may be low or negligible for adults and children. The mean values of carcinogenic risk (CR) and total carcinogenic risk (TCR) of As and Cr via the three pathways for adults and children were between 10(-6) and 10(-4), indicating that the carcinogenic risk levels of As and Cr were tolerable or acceptable, and the mean TCR value of Cd through the three pathways for adult and children was less than 10(-6), implying that the carcinogenic risk level of Cd was negligible. Mn, Ni, Cr, and Co in dry atmospheric deposition were mainly contributed from the crustal sources, while As, Cd, Cu, Hg, Mo, Pb, Se, and Zn in dry atmospheric deposition were derived from both crustal and anthropogenic sources. The results obtained in this study advocate the necessity for monitoring atmospheric deposition in some rural areas, and also provide a scientific basis for controlling contamination posed by toxic trace elements in dry atmospheric deposition.