Department of Chemistry, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan.
Environ Sci Process Impacts. 2020 Jul 1;22(7):1514-1524. doi: 10.1039/d0em00135j. Epub 2020 Jun 19.
Heavy metals in particulate matter (PM) are of great concern, and their effects on the environment and human health depend on their solubilities and species present. In this study, the solubility of As, Se, Sb, V and Cr and their species eluted in water was investigated. As, Se, Sb, and V were present mostly in fine particles, and they were predominantly water-soluble in fine particles (<2.5 μm, PM) but insoluble in coarse particles (>2.5 μm). Solubility of Cr was poor even in fine particles. It was found that for fine particles, solubilities of the heavy metals were related to the nitrate and sulfate contents. This suggests that the higher the acidity of the particles, the higher the solubility of the heavy metals. Oxoanions of the five kinds of heavy metals in water extracts of fine particles were determined by inductively coupled plasma mass spectrometry preceded by ion chromatography. The results suggested the presence of atmospheric oxidation during the aerosol transportation. Also, the As(iii)/As(v) (arsenite/arsenate) ratios for the fine particle extracts were related to the transition metal concentrations, which indicated that Fe, Cu, etc. in fine particles affected the As redox equilibrium. It was suggested that the heavy metals exist as complexes with iron hydroxide and dissolved organic matter in addition to the free oxoanions. These investigations were performed for PM samples collected in winter and summer in Kumamoto, west Japan, where the site is strongly exposed to westerly winds from continental East Asia. The obtained results improve our understanding of the behavior of the heavy metals in airborne PM after depositing on a wet environment and biota.
颗粒物（PM）中的重金属备受关注，其对环境和人体健康的影响取决于它们的溶解度和存在形态。本研究考察了 As、Se、Sb、V 和 Cr 在水中的溶解度及其形态。As、Se、Sb 和 V 主要存在于细颗粒物中，它们在细颗粒物（<2.5 μm，PM）中主要是水溶性的，但在粗颗粒物（>2.5 μm）中不溶。Cr 的溶解度即使在细颗粒物中也很差。研究发现，对于细颗粒物，重金属的溶解度与硝酸盐和硫酸盐含量有关。这表明，颗粒的酸度越高，重金属的溶解度就越高。通过电感耦合等离子体质谱法（ICP-MS）在前处理离子色谱（IC）的基础上，测定了细颗粒物水提取物中五种重金属的含氧阴离子。结果表明，在气溶胶传输过程中存在大气氧化作用。此外，细颗粒提取物中的 As(iii)/As(v)（亚砷酸盐/砷酸盐）比值与过渡金属浓度有关，这表明细颗粒中的 Fe、Cu 等影响了 As 的氧化还原平衡。研究表明，重金属除了以自由含氧阴离子的形式存在外，还与氢氧化铁和溶解有机物形成配合物。这些研究是在日本西部熊本采集的冬季和夏季 PM 样本中进行的，该地点强烈暴露于来自东亚大陆的西风中。研究结果提高了我们对重金属在沉积到湿环境和生物群落后在空气中的 PM 中的行为的认识。
