不同组成有机质对土壤中砷迁移行为的影响

本研究选择腐植酸(HA)、黄腐酸(FA)和鸡粪提取的可溶性有机质(DOM)三种天然有机质,加入供试土壤,以溴离子作为示踪剂,通过四组模拟土柱实验,获得不同有机质组成的土壤中As (V)的穿透曲线,并用CXTFIT 2.1软件拟合,计算阻滞系数R_d值,同时测定流出液中As (V)的形态变化。结果表明:HA抑制了As (V)的迁移,而加入FA和DOM后As (V)在土壤中的移动性显著增强。四种处理(CK、土壤+HA、土壤+FA、土壤+DOM)中As (V)的阻滞系数R_d值分别为17.82、19.53、10.13和12.2,土柱中残留的As分别占As总量的27.4%、31.7%、19.2%和18.2%。腐植酸以芳香族含量为主,分子量较大,吸附固定As的能力较强;黄腐酸和提取的可溶性有机质主要结构为烷基碳和氧烷基碳,H/C和O/C值较高,与As存在竞争吸附,促进As的迁移。

Effects of Natural Organic Matter with Different Composition on the Mobility of Arsenic in Soil

In this paper, humic acid (HA), fulvic acid (FA) and dissolved organic matter (DOM) extracted from chicken manure were selected to compare the migration of As(V) in soils composed of different natural organic matter. The breakthrough curves and spatial distribution of As along the column length was determined following soil column experiments. The computer program, CXTFIT 2.1, was used to estimate the parameters by simulating the breakthrough curves of Br^- and As, respectively. After each experiment, the species changes of As in the solution were measured. The results show that HA, FA and DOM affect the transport of As in soil. HA inhibited the migration of As in soils, while the mobility of As in soils increased significantly after the addition of FA and DOM. The retardation coefficient (R_d) values of four treatments (control, soil+HA, soil+FA, soil+DOM) are 17.82, 19.53, 10.13 and 12.2, respectively. The residual As content in soil column accounts for 27.4%, 31.7%, 19.2% and 18.2% of original total As, respectively. HA is mainly aromatic and has relatively large organic molecules, which has strong adsorption and immobilization capacity for As. The main structures of FA and DOM are alkyl carbon and oxyalkyl carbon with a higher element ratio of H/C and O/C, which are competitive with As for adsorption, hence promote the transportation of As in soil consequently.