Distribution Characteristics and Seasonal Variations of Arsenic in Atmospheric Aerosols over the Yellow Sea and Bohai Sea

Abstract

Marine aerosol samples of total suspended particulates (TSP) were collected in winter (2017) and spring and summer (2018) over the Yellow Sea and Bohai Sea. These samples were analyzed for total arsenic (As), As(Ⅴ) and As(Ⅲ), and water soluble ions to investigate the distribution and seasonal variation of As in atmospheric aerosols, as well as the dry deposition flux. Results showed that As concentrations in winter, spring, and summer were 6.6, 5.5, and 4.4 ng·m-3, respectively. The highest As concentrations occurred in the winter. Obvious differences in the spatial distribution of As were observed in different seasons. The highest concentrations of As were observed over the Bohai Sea in winter and the northern Yellow Sea in spring, with an average of 8.8 and 11.3 ng·m-3, respectively. As concentrations exhibited a relatively uniform spatial pattern in summer over the Yellow Sea and Bohai Sea, which may have been affected by the different sources of As. As(Ⅴ) was the main species of As, while As(Ⅴ)/As(Ⅲ) ratios were 0.41 in winter and 0.21 in summer, respectively. Average As/TSP ratios in the winter, spring, and autumn were 95.4, 83.9, and 81.4 μg·g-1, respectively. Obviously higher As/TSP ratios, indicating higher intensity, occurred in winter. Air masses carry pollutants released over the Bohai Rim Region by the winter monsoon, resulting in higher As concentrations in winter. In summer, As concentrations are also higher, because air masses bring pollutants to the southeast coastal economic zone via the northeast monsoon. In spring, most air masses arriving in this region originate from Siberia and the southeast ocean with high rate, resulting in lower As concentrations. The significant correlation between K+/TSP and As/TSP (r=0.78, P<0.05) in winter indicates that As is affected by the combustion of land biomass. No significant correlation in summer reveals the difference in As sources between winter and summer. The dry deposition flux of As over the Yellow Sea and Bohai Sea was 1.15 μg·(m2·d)-1 in winter, 0.77 μg·(m2·d)-1 in spring, and 0.97 μg·(m2·d)-1 in summer, with an annual mean value of 0.95 μg·(m2·d)-1.