Fraction distribution of arsenic in different-sized atmospheric particulate matters

The sequential extraction method was used to determine the fraction of arsenic (As) in different-sized particulate matters (PMs) (i.e., PM_2.5, PM₁₀, and total suspended particles (TSP)). Samples were collected from Baoding, a typical medium-sized city with the serious haze pollution in China. The bioavailabilities of As in the samples were estimated based on the fraction results. A large percentage of fine particles were detected in TSP, with the average PM_2.5/PM₁₀ and PM₁₀/TSP ratios all above 0.69. The total concentrations of As in PM_2.5, PM₁₀, and TSP samples were in the range of 4.5-296.4, 14.1-708.0, and 32.8-798.0 ng m^-3, respectively. The mass percentages of As in PM_2.5, PM_2.5-10, and PM_10-100 were calculated; the results indicated that As tended to concentrate in fine particles. PM-bound As mainly presented in the nonspecifically sorbed fraction (F1) during all of the sampling periods. The percentages of F1-As and bioavailability of As were higher in PM_2.5, followed by PM₁₀ and TSP. By contrast, the residual fraction (F5-As) contents declined in the order of TSP > PM₁₀ > PM_2.5. Significant differences in the speciation and bioavailability of As in different-sized PMs were found, and the influence of particle size on the speciation and bioavailability of As in PMs was verified. Fine particles adsorbed more As with higher bioavailability, and potentially led to more serious adverse effects on human health than the larger ones.