有机酸和磷对两种污染土壤铅的释放作用研究

Effects of Organic Acids and Phosphate on Lead Release from Two Contaminated Soils

用土壤培养和化学浸提法研究了不同低分子量有机酸和磷对污染土壤中铅释放的影响。结果表明,随有机酸浓度增加,铅污染红壤、棕壤中可溶出铅量均增加。当供试有机酸浓度≥1mmol·L-1时,相同浓度有机酸溶出铅量为柠檬酸>乙酸>草酸;当有机酸浓度≤0.5mmol·L-1时,溶出铅量为草酸>柠檬酸>乙酸。将2g·kg-1磷及50mmol·kg-1有机酸与铅污染红壤以不同方式混合后,柠檬酸处理的溶出铅比率(在污染土壤中加入P、有机酸后溶出铅含量与单加有机酸溶出铅含量之比)为66%(先加有机酸再加磷)、58%(有机酸与磷同时加入)、70%(先加磷再加有机酸),草酸处理(方式同上)的溶出铅比率为90%、89%、94%,乙酸处理(方式同上)的为10%、8%、10%。铅污染棕壤上,以上处理的溶出铅比率分别为106.46%、104.43%、105.19%(柠檬酸);43%、48%、58%(草酸);38%、42%、55%(乙酸)。供试条件下,红壤最低溶出铅比率低于棕壤。

Soil culture and chemical extraction were used to study the effect of different low molecular weight organic acids and phosphate on lead release in two exogenous contaminated soils. The result showed that the amount of soluble lead of red soil and brown soil increased with the increase of concentration of organic acids. When the concentration of the tested organic acids was no less than 1 mmol·L-1, the amount of lead released by three organic acids at the same concentration was citric acid〉acetic acid〉oxalic acid. While the concentration of organic acids was no more than 0.5 mmol·L-1, the amount of soluble lead was oxalic acid〉citric acid〉acetic acid. After a mix of 2 g·kg-1 P, contami- nated red soil and 50 mmol·kg-1 organic acids in three different orders, soluble lead leaching rates of red soil dealt with citric acid were 66% （organic acid first）, 58%（phosphate and organic acid added simultaneously）, and 70%（P first）, respectively; while in terms of oxalic acid and acetic acid were 90% , 89% , 94% and 10% , 8% , 10% . In brown soil, these results were 106.46%, 104.43%, 105.19%（citric acid）; 43%, 48%, 58%（oxalic acid）; 38%, 42%, 55%（acetic acid）. Therefore, the lowest soluble lead leaching rates in red soil was lower than that in brown soil under the tested conditions.