海三菱藨草(Scirpus mariqueter)根际沉积物中重金属生物有效性的影响因素

采用野外连续调查和实验分析方法，连续3年研究了海三菱藨草根际沉积物重金属（Cu、Zn、Pb和Cd）生物有效性的主要影响因素（生长季节、pH、P、Eh和DO等）。结果表明，植物不同生长季节的变化影响根际沉积物生物有效性的季节变化。具体表现为：Cu和Pb均在春、夏季可交换态含量较高，生物有效性较高，而秋、冬季可交换态较低，生物有效性较低，但碳酸盐结合态和铁锰氧化态二者之和也比较高，具有一定的潜在生物有效性；Zn在任何季节的可交换态比例均不高，以有机结合态和残渣态的形态为主，生物有效性较低；Cd一般以残渣态为主，基本不具有生物有效性。pH值下降，春、夏季可交换态和铁锰氧化物结合态增加，而有机结合态和碳酸盐结合态减少，提高了生物有效性，而秋、冬季正好相反；磷对重金属生物有效具有直接影响的为无机磷，春、夏季随着无机磷的减少，pH值下降，提高了生物有效性。春、夏季根际Eh和溶解氧含量增加，降低了其生物有效性。

FACTORS AFFECTING BIOAVAILABILITY OF HEAVY METAL IN RHIZOSPHERE OF SCIRPUS MARIQUETER

A three-year successive field investigation and laboratory analysis were conducted for factors affecting bioavailability of heavy metal (Cu, Zn, Pb and Cd ) in rhizosphere of Scirpus mariqueter. The factors include plant growth season, pH, phosphorus, Eh and dissolved oxygen. Results indicate that season alternation affects the bioavailability; and the exchangeable contents of Cu and Pb are higher in spring-summer with higher bioavailability accordingly, but lower in autumn and winter with lower bioavailability. Particularly, the combination of carbonate and ferro-manganese oxides contents of Cu and Pb is also higher, indicative of potential bioavailability. However, the content of exchangeable Zn is low but the organic-bounded and residues that account for its low bioavailability. For Cd, mostly it is in the residue of no bioavailability. In spring and summer with the increase of pH, both the exchangeable and the ferro-manganese oxides increased, while the organic-bounded and the carbonate decreased, which improved their bioavailabilities. Furthermore, in autumn and winter, the scenario is opposite to that of spring and summer. Inorganic phosphorus affect directivity the bioavailability in spring and summer, resulting in decrease of pH because of inorganic phosphorus decline. The bioavailability of heavy metal decreased with the increase in Eh and dissolved oxygen.