汪宁欣,刘婷婷,谢希琳,周文强.无机砷与两种典型天然有机质络合行为比较[J].环境科学学报,2019,39(8):2593-2601
无机砷与两种典型天然有机质络合行为比较
- Comparison of complex behavior between inorganic arsenic and two typical natural organic matter
- 基金项目：国家自然科学基金（No.21507001）
- 汪宁欣
- 安徽工业大学能源与环境学院, 马鞍山 243032
- 刘婷婷
- 安徽工业大学能源与环境学院, 马鞍山 243032
- 谢希琳
- 安徽工业大学能源与环境学院, 马鞍山 243032
- 周文强
- 南京大学环境规划设计研究院股份公司, 南京 210093
- 摘要：以毒性较强的无机砷（五价砷iAsV和三价砷iAsⅢ）和环境中常见的天然有机质（NOM）为研究对象，采用平衡透析的方法，研究在pH中性条件下两种无机砷与两种NOM （胡敏酸HA和富里酸FA）的络合平衡时间，并通过对络合态砷占总砷比例的测定以及条件分配系数（Dom）的测定，对比不同NOM种类、不同无机砷种类及不同比率iAs/DOC （dissolved organic carbon，可溶性有机碳）条件下两者的络合特征，并对相应的络合机理进行探讨.结果表明，无机砷与NOM的络合过程分为快速扩散、慢速扩散和平衡3个阶段；其中iAsV与两种NOM的络合平衡时间约为48 h，iAsⅢ则在24 h之后基本达到络合平衡状态.两种NOM与iAsV和iAsⅢ的络合比例随NOM浓度的增高而增加，但由于HA比FA具有更高的分子量和更复杂的分子结构，HA较FA显示出更强的络合能力.由于配位点减少原因，无机砷与两种NOM的络合随iAs/DOC比率上升而呈现出非线性下降趋势，这样非线性的现象与络合点位至少有两种类型有关.
- Abstract：Highly toxic inorganic arsenic (arsenate iAsV and arsenite iAsⅢ) and two common natrual organic matters (NOM), humic acid and fulvic acid, were selected as the object in the present study. The complex equilibrium time of inorganic arsenic bound onto NOM under neutral pH condition was investigated using equilibrium dialysis method. Based on the proportion of bound arsenic to the total arsenic, the complexion characteristics were compared accroding to NOM type and arsenic species. Conditional distribution coefficients (Dom) of iAsⅢ and AsV bounded onto NOM were fitted as a function of different iAs/dissolved organic carbon (DOC) ratios. Additionally, the mechanism of complexation was discussed. The results indicate that the binding process of inorganic onto NOM is divided into three stages including a fast diffuse stage, a slow diffuse stage and an equilibrium stage. equilibrium time for iAsV Complexation onto HA/FA (humic acid/fulvic acid) was 48 hours, while 24 hours for iAsⅢ. Proportion of the bounded arsenic to the total arsenic increased with the concentrations of HA and FA. However, compared to FA, HA had a higher affinity for arsenic, probably due to the higher molecular weight and more complex molecular structure of HA. As a result of the decreasing binding sites, the values of Dom of inorganic arsenic complex with HA/FA exhibit a non-linear decrease with the increasing ratio of iAs/DOC. This non-liner relationship might be attributed to the existence of at least two types of binding sites.
