添加外源耐砷菌与零价铁对土壤砷有效性和形态的影响

采用室内土壤培养试验，探讨了外源添加耐砷真菌棘孢木霉（TrichodermaasperellumL．）和零价铁对土壤砷的有效性和形态转化的影响。结果表明：向污染土壤中添加耐砷真菌棘孢木霉后，随着培养时间的延长，土壤中水溶态砷和NaHCO，提取态砷含量均呈稳定增加趋势，耐砷真菌促进了土壤中砷的溶出和释放；培养30d时，耐砷菌处理土壤有效砷含量比同期对照增幅达3．9％-10．7％，水溶态砷以As（V）为主，未检测到As（Ⅲ）、一甲基胂（MMA）、二甲基胂（DMA）等其他形态的砷；随着外源零价铁的加入，土壤中砷的活性大大降低，其有效砷含量降幅为76．5％-90．4％；在耐砷菌与零价铁联合作用下，相比于单纯的零价铁处理，土壤有效砷含量显著增加（p〈0．05），因耐砷真菌棘孢木霉的加入导致零价铁对土壤砷的固定效率下降7．0％-11．1％。耐砷菌导致土壤砷活化可能主要与残渣态向非专性吸附态砷的转化等过程有关，外源零价铁对土壤砷的固定作用可能与非专性吸附态向无定形及弱晶质氧化物结合态、残渣态砷等转化过程相关；耐砷菌的加入抵消了零价铁对土壤砷的部分固定效果，但短期内（〈30d）不会构成大的影响。

Arsenic Availability and Speciation in Soils Treated with Exogenous Arsenic-resistant Fungi and Zero-valent Iron

Through indoor soil incubation experiment, arsenic availability and speciation in soil treated with exogenous arsenic-resistant fungi （ Trichoderma asperellum L. ） and zero-valent iron were explored. The results showed that when the exogenous arsenic-resistant fungi. was added into soils, both the content of water soluble arsenic and the of content NaHCO3 extractable arsenic increased steadily with the pro- longing incubation time, indicating that the arsenic-resistant fungi promoted the release and dissolution of arsenic from soils, and when the experiment lasted for 30 days, the increasing percentage of soluble arsenic content in soils ranged from 3.9% to 10.7% compared to the con- trol treatment. Only arsenateAs （ V ）] was found out, and arsenic of other species including arseniteAs （ m ）~, dimethylarsinie acid （DMA）, monomethylarsonic acid（ MMA ） was not detected. With exogenous zero-valent iron added into soils, the reduced percentage of available ar- senic in soils extracted by NaHCO3 ranged from 76.5% to 90.4%. Compared to the zero-valent iron treatment, the available arsenic in soils increased significantly（P〈0.05 ） under the treatment of exogenous arsenic-resistant fungi and zero-valent iron, and the stabilization ef- ficiency decreased 7.0%-11.1% due to more available arsenic absorbed. The mechanism of activated arsenic in soils resulted from exoge- nous arsenic-resistant fungi maybe connected with the transformation from residual phase of arsenic to non-specifically sorbed one. The sta- bilization of arsenic due to the addition of exogenous zero-valent iron into soils may be related to the transformation process from non- specifically sorbed arsenic to residual phase and amorphous and poorly-crystalline hydrous oxides of Fe and A1 phase. The addition of ar- senic-resistant fungi T. asperellum resulted in the enhancement of available arsenic of soils treated with iron power in certain degree, which is not so obvious in short term.