秸秆不同还田方式对污染土壤砷形态的影响

Effects on the arsenic speciation in the contaminated soil by different straw returning

为探讨秸秆还田对农田土壤砷形态的影响,采用室内土壤培养试验,探究旱作和水淹条件下秸秆灰分还田、秸秆粉碎还田对污染农田土壤砷赋存形态的影响。结果表明:在旱作条件下,秸秆灰分还田松散结合态砷含量相比对照试验提高了102%,钙型砷含量降低了30.3%;秸秆粉碎还田松散结合态砷、钙型砷含量分别增加了43.3%、21.7%,铝型砷、铁型砷含量降低。水淹条件下,秸秆灰分还田、粉碎还田松散结合态砷含量相比对照试验提高了105%、210%,钙型砷含量降低,铝型砷、铁型砷含量升高,残渣态砷含量降低。秸秆还田上覆水pH升高、Eh降低、砷浓度升高,粉碎还田、秸秆灰分还田上覆水砷浓度分别达对照试验的26倍和6倍,Eh与上覆水砷浓度存在显著负相关,r=-0.876(P=0.01)。研究表明,两种秸秆还田方式均能增加砷的活性,若在砷污染土壤中用秸秆灰分或粉碎秸秆还田可能会增加砷的环境风险。

In order to explore the influence of straw returning on arsenic speciation in the farmland soil, the soil incubation experiments were carried out to investigate the arsenic speciation in a contaminated soil by returning straw ash and crushed straw under the conditions of drought and flooded. The results showed that compared to the control experiment, the content of A-As was increased by 102% by straw ash residues, while Ca-As decreased by 30.3% under the condition of drought. In addition, the contents of A-As and Ca-As were increased by 43.3% and 21.7% by crushed straw returning, respectively, while the contents of Al-As and Fe-As were decreased. Under the condition of flooding, the contents of A-As were increased by 105% and 210% by straw ash and crushed straw returning, respectively. Meanwhile, the contents of Ca-As and R-As were reduced, while the contents of Al-As and Fe-As were increased. To the straw returning, the pH and arsenic concentrations of overlying water were increased, while Eh decreased. To the straw crushing and ash returning, the arsenic concentration were 26 times and 6 times as much as the control experiments, respectively, and the Eh was significantly correlating with the arsenic concentration in the overlying water(r =-0.876(P = 0.01)). The results indicated that the two modes of straw returning could increase the activity of arsenic. Hence, the use of straw ash or crushing straw in the arsenic contaminated soil may increase the environmental risk for arsenic pollution.