P、Fe及水分对土壤砷有效性和小麦砷吸收的影响

Effects of P, Fe and water supply on arsenic availability in soil and accumulation in wheat seedlings

为探讨外源调控措施对土壤中砷的结合状态和植物砷吸收的影响,利用室内盆栽试验,研究了外源添加不同的磷酸盐、FeCl_3和不同水分条件下土壤中砷的有效性和小麦砷吸收的变化。研究结果显示,加Fe能显著降低土壤pH值、土壤溶液中砷的含量及土壤中非专性吸附态和专性吸附态砷的含量,降低植物对砷的积累。施加不同形态磷酸盐后,土壤溶液中砷的浓度显著增加,其中以KH_2PO_4和Ca(H_2PO_4)_2处理条件下增加效果更明显。加磷处理也能显著增加小麦地上部砷含量,但对土壤不同提取态砷的含量影响不明显。不同土壤含水量并不能引起土壤pH的显著变化,饱和水处理时土壤溶液和土壤各提取态砷的含量略高于干湿交替处理。小麦地上部分砷的含量与土壤溶液砷浓度和土壤中专性吸附态砷含量分别呈极显著(P<0.01)和显著(P<0.05)正相关,而与无定形Fe-Al氧化物结合态和晶质Fe-Al氧化物结合态均呈显著负相关(P<0.05)。小麦地上部生物量与专性吸附态和晶质Fe-Al氧化物结合态砷之间呈显著正相关(P<0.05),与无定形Fe-Al氧化物结合态和残渣态砷含量之间呈显著负相关(P<0.05),其中与无定形Fe-Al氧化物结合态砷含量的相关性达极显著水平(P<0.01)。地上部砷含量和生物量之间呈极显著负相关(P<0.01)。结果表明:不管是在加磷还是不加磷的条件下,FeCl_3均能显著降低土壤溶液中砷的含量和小麦对砷的吸收;三种磷酸盐处理显著增加了土壤溶液和小麦地上部砷的含量,小麦地上部对砷的积累在三种磷酸盐处理之间没有显著差异。

In this study, we investigated the effects of exogenous phosphate（P）, iron（Fe）and water supply on arsenic（As）availability in soil and its accumulation in the shoots of wheat（Triticum aestivum L.）seedlings. The Fe supplement resulted in a significant reduction of As available for uptake by plants, including specifically and non-specifically sorbed As in soil, which might be attributed to the decrease of As accumulation in the shoots of wheat plants. On the contrary, phosphate application led to the opposite effect, showing a dramatic increase in the As concentration in the soil solution and As uptake in the wheat shoots. Among the treatments with various forms of phosphate, a significant difference in the As concentration in the soil solution was detected. However, no change was observed in the As concentration in various fractionations of the soil. This change in the As concentration in the soil solution by different forms of phosphate did not correspond to the variation in As accumulation in wheat shoots. Various water supplies to the soil could not alter the As concentration in the soil solution and wheat shoots, as well as the soil pH. Correlation analysis suggested that the As concentrations in wheat shoots were positively correlated with the As in soil solution and specifically sorbed As in soil, while being negatively correlated with dry biomass, amorphous Fe and Al oxidesbound, and, crystalline Fe and Al oxides-bound As in soil（P〈0.05）. Additionally, the shoot biomass was significantly positively correlated with the specifically sorbed and amorphous Fe and Al oxides-bound As concentrations in soil（P〈0.05）. Considered together, our data indicates that the exogenous supplement of Fe and P alters the As concentration in the soil solution and specifically sorbed As in soil, which in turn positively affect the As accumulation in wheat shoots.