土壤外源铅的稳定化特征及其对土壤性质的响应

为探明土壤理化性质对外源铅（Pb）稳定化过程的影响,选取11种理化性质差异较大的土壤样品,分别加入500mg·kg-1Pb和500mg·kg-1Pb＋1.0mg·kg-1镉（Cd）后进行360d的室内培养,利用5个动力学模型对Pb稳定化过程进行模拟,并进一步分析了有效Pb变化的特征及其关键影响因素。结果表明,在Pb单一和Pb-Cd复合污染下,所有土壤有效Pb浓度在初始的15d内都迅速下降,随后变化减缓,60d后基本达到平衡。外源Cd对Pb浓度变化的影响非常小。5个动力学模型中以二级动力学方程模拟结果最好,所得的稳定化平衡浓度Ce2和表观速率常数k2能够较好地表征Pb的衰减和稳定过程。相关和逐步回归分析表明,提高土壤pH、阳离子交换量和有机质含量能够显著加快Pb的稳定化速率、降低Pb的平衡浓度,并以pH对Pb稳定化速率和平衡浓度的直接影响最大。

External Lead Stabilization Characteristics in Soils and Responses to Soil Properties

In order to evaluate the stabilization characteristics of external lead（Pb）in soils and the responses to soil properties, 11 soils with different properties were selected and added 500 mg·kg-1 Pb or 500 mg·kg-1 Pb＋1.0 mg·kg-1 Cd. During 360 days of incubation, the avail- able Pb contents were periodically measured. Then five dynamic models were used to simulate the variability. Soil available Pb showed a rapid decrease during the first 15 days, followed by a slow decrease until day 60 when available Pb was stabilized. Existing of Cd had no ef- fect on Pb availability. Among the five models, a second-order equation was the best one for simulating Pb stabilization in soils, which pro - vided satisfied parameters：equilibrium concentration（Ce2）and stabilization velocity（k2）. Correlation analysis and stepwise regression sug- gested that stabilized velocity of Pb was higher in the soils with higher pH, CEC and clay content. Soil pH had the largest effect on Ce2 and k2 during Pb stabilization process.