可溶性有机物和pH值对铅的毒性和生物可利用性的影响

Effects of Dissolved Organic Matter and pH on Toxicity and Bioavailability of Lead

采用芥菜发芽试验研究了柠檬酸(CA)、苹果酸(MA)、草酸(OA)、乙二胺四乙酸(EDTA)、二乙烯三胺五乙酸(DPTA)、腐植酸(HA)和土壤提取液(A)对Pb2+的毒性和生物可利用性的影响。结果表明,低分子量有机酸柠檬酸和苹果酸降低了Pb2+的毒性,但增加了Pb2+的生物可利用性,低浓度乙二胺四乙酸(EDTA)、草酸(OA)和二乙烯三胺五乙酸(DTPA)均降低了Pb2+的毒性和生物可利用性;相反,腐植酸增加了Pb2+的毒性,降低了生物可利用性。pH<5时,上述低分子量有机酸增加了Pb2+的毒性和生物可利用性;pH>5时,则降低了Pb2+的毒性和生物可利用性。土壤中Pb2+的生物可利用性和毒性效应取决于土壤溶液中共存有机物质的性质和溶液的pH值。

The germination test was carried out to study the effect of different organic ligands citric acid （CA）, malic acid （MA）, oxalic acid （OA）, ethylenediamine tetra-acetic acid（EDTA）, diethylenetriamine penta-acetic acid（DTPA）, humic acid（HA） and soil extract（A） on toxicity and bioavailability of Pb^2＋ and its uptake by mustard. Mustard seeds were exposed to solutions containing Pb^2＋ and several kinds of dissolved organic matters, and the root lengths and the concentration of Pb^2＋ in mustard sprouts were measured. The results indicated that low molecular weight organic acids （citric and malic acids） decreased the toxicity of Pb^2＋ and increased its bioavailability. Low concentrations of the synthetic chelators ethylenediamine tetra-acetic acid （EDTA）, oxalic acid （OA） and diethylenetriamine penta-acetic acid （DTPA） decreased the toxicity and bioavailability of Pb^2＋. In contrast, humic acid increased the toxicity of Pb^2＋ and decreased the bioavailability of Pb^2＋. The toxicity and the bioavailability of lead increased at pH〈5, while decreased at pH〉5. Consequently, the bioavailability and toxic effects of Pb2~ in soil depended on the nature of coexisting organic substances in the soil solution and the pH of soil solution.