酸性水动态淋滤与静态浸泡土壤中氟的实验研究

模拟研究了不同pH值的淋滤液对土壤的动态淋滤及静态浸泡,用氟离子选择电极法测定了不同pH值淋滤液在不同时间段获取的淋出液中氟浓度以及淋滤后残渣中的氟含量,结果表明:淋滤液的pH值、淋滤时间以及土壤中氟的赋存形态对氟的淋出影响重大。淋滤液的酸性越强,土壤中氟的最大淋出浓度越大,土壤中被淋出的氟含量越高,淋出率也越高且氟的淋出主要集中在淋滤初期60h内,后渐趋于平缓;动态淋滤淋出的氟含量及溶出率均稍高于静态浸泡,这可能源于动态淋滤较强的分子运动,进而使提取剂充分渗透到土壤基质中。黄壤、黄棕壤、水稻土在pH=3的淋出液中的氟浓度变化曲线表明土壤淋洗作用更多的是将土壤中的可溶性氟盐淋洗掉。可溶性氟盐越多,被淋失的氟就越多。

Characteristics of Fluorine in Soil in both Dynamic Leaching and Static Immersion Experiments

The dynamic leaching experiments and static immersion were carried out by using solution with different pH in order to investigate behaviour and fluorine concentration with different leachates;fluorine contents in residual after leaching were measured by fluoride ion-selective electrode. Results show that pH,leaching time and the modes of occurrence have great influence on leaching behavior of fluorine. The maximum concentration of fluorine,fluorine total quantity released soil and leaching rate increase with increasing acidity of leaching solution and fluorine leaching mainly concentrates within 60 h in the early stage of leaching. With increasingleaching time,fluorine released from soil decreases. Fluorine content dissolved and leaching rate of dynamic leaching are both higher than that of static immersion. This may be due to the stronger molecular motion of dynamic leaching which prompt the leaching solution fully infiltrating into the soil matrix. Leaching curves of yellow soil, yellow brown earths, paddy soil under the solution of pH=3 indicate that soluble fluoride saltcan be released during the leaching process and the more the soluble salt is, the more fluorine will be released.