Pollution Characteristics of Metal Components in PM_2.5 in Two Districts of Guangzhou

Objective To evaluate the metal pollution of atmospheric PM_2.5 in two districts of Guangzhou.

Methods PM_2.5 samples were collected in Yuexiu District and Panyu District of Guangzhou in 2015 and analyzed for 15 metals by ICP-MS. The enrichment factors, characteristics, sources, and potential ecological risks of heavy metals were evaluated.

Results The monthly concentrations of PM_2.5 were 0.046-0.160 mg/m³ in Yuexiu District and 0.013-0.108 mg/m³ in Panyu District. The annual average concentrations of PM_2.5 were 0.078 mg/m³(Yuexiu) and 0.057 mg/m³(Panyu), 2.2 times and 1.6 times of the Grade II standard limit of the Ambient Air Quality Standards(GB 3095-2012), and the average of Yuexiu was higher than that of Panyu. The annual total average concentration of selected 15 metals was 1.08 μg/m³(accounting for 1.4% of PM_2.5 mass) in Yuexiu and 0.73 μg/m³(1.3%) in Panyu; iron, zinc, aluminum, and lead contributed most to the concentrations. The metal concentrations in Yuexiu and Panyu were 0.443 μg/m³(0.57%) and 0.285 μg/m³(0.50%) for iron, 0.306 μg/m³(0.39%) and 0.233 μg/m³(0.41%) for zinc, 0.157 μg/m³(0.20%) and 0.065 μg/m³(0.11%) for aluminum, and 0.059 μg/m³(0.08%) and 0.051 μg/m³(0.09%) for lead, respectively. The annual concentrations of the 15 metals were ranked from high to low as follows: iron >zinc >aluminum >lead >copper >manganese >barium >chromium >arsenic >stibium >selenium=nickel >cadmium >thallium >mercury for Yuexiu, and iron >zinc >aluminum >lead >manganese >copper >barium >arsenic >stibium >selenium >nickel=chromium >cadmium >thallium >mercury for Panyu. Metals with enrichment factor values over 100 were copper(130.1), zinc(235.1), arsenic(120.2), selenium(200.3), cadmium(201.1), and stibium(293.6), indicating anthropogenic inputs. The metals ordered by potential ecological risk index from high to low were cadmium >mercury >arsenic >copper >lead >zinc >nickel >chromium >manganese; cadmium(1 415.02) was graded extremely high potential ecological risk, and followed by mercury(310.77) and arsenic(281.51) as high risk. The total potential ecological risk index of nine heavy metals was 2 313.94, showing high comprehensive potential ecological risk.

Conclusion The metal component concentrations in atmospheric PM_2.5 in Yuexiu District are generally higher than those in Panyu District, and some metal elements are results of anthropogenic pollution.