混合无机改良剂对酸性多重金属污染土壤的改良效应

为筛选适合于治理和修复酸性多金属污染土壤的无机混合改良剂,通过正交土壤培育实验,研究了不同剂量的石灰石、沸石和羟基磷灰石组配的混合改良剂对广东省韶关市大宝山周边的酸性多金属污染土壤的改良作用,根据其提高土壤p H和固定土壤Cu、Zn、Pb、Cd的效果,从中筛选出效果较好的6种混合改良剂配方,并以红油麦菜为供试植物进行盆栽试验。土壤培育实验显示,15种混合改良剂均显著提高了土壤p H,对土壤中Cu、Zn、Pb、Cd有很好的固定效果。统计分析显示,混合改良剂对土壤中Pb、Cd、Zn固化效果的影响依次为石灰石>羟基磷灰石>沸石,对Cu固化效果影响依次为石灰石>沸石>羟基磷灰石。盆栽试验发现:6种无机混合改良剂显著增加了土壤p H值,降低了Cd、Cu、Zn、Pb的有效态含量,且土壤p H值和Cd、Cu、Zn的有效态含量呈显著负相关。当土壤p H为6~7时,红油麦菜的生长健康,其中混合改良剂(4 g·kg-1沸石+2 g·kg-1石灰石+6 g·kg-1羟基磷灰石)处理后,红油麦菜可食部分的生物量最高。当土壤施加改良剂的用量过大、土壤p H过高时(处理A与B),植物的生长状态较差。虽然混合改良剂显著降低了土壤中Pb、Cd的有效态含量,但红油麦菜地上部的Cd含量均显著超过食品卫生标准,Pb含量超过或接近食品卫生标准。因此,石灰石、沸石和羟基磷灰石混合无机改良剂在改善红油麦菜的生长和提高产量上有很大效果,但不能保障红油麦菜在大宝山周边的酸性多金属污染土壤上的安全生产。

Remediation of Multi-metals Contaminated Acidic Soil by Mixed Inorganic Amendments

The main objective of the present study was to determine the capacity of mixtures of some inorganic amendments to reduce the bioavailability of heavy metals in multiple-metals-contaminated acidic soil. Incubation experiment with orthogonal experimental design was conducted to study the efficiency of mixed inorganic amendments in increasing soil pH and decreasing the mobility of Cd, Pb, Cu and Zn in a multi-metals-contaminated acid soil collected from the Dabaoshan area of Shaoguan City, Guangdong Province. Then a pot experiment was carried out to examine the effects of six different combinations of three inorganic amendments on heavy metal bioavailability and growth and heavy metal accumulation of red leaf lettuce(Lactuca sativa L.). All combinations of three inorganic amendments significantly increased soil pH and reduced the mobility and bioavailability of Cd, Pb, Cu and Zn in soil. The ability of immobilizing soil Pb, Cd, and Zn decreased in order of limestone > hydroxyapatite > zeolite, but for soil Cu it was limestone> zeolite> hydroxyapatite. There were significant negative correlations between soil pH and bioavailable Cd, Zn, and Cu. When soil pH was raised to 6~7 by supplying inorganic amendments, red leaf lettuce grew healthy and the highest shoot biomass was obtained in soil treated with 4 g·kg^-1 zeolite+2 g·kg^-1 limestone+6 g·kg^-1 hydroxyapatite. However, over-doses of inorganic amendments inhibited the growth of red leaf lettuce. Though all these mixed amendments significantly reduced the bioavailability of Pb and Cd in soil, the shoot Cd concentrations were still greater than 0.2 mg·kg^-1(the limit for food health standard), while shoot Pb concentrations were close to the limit value(0.3 mg·kg^-1). In summary, mixed amendments of limestone, zeolite and hydroxyapatite can improve the growth of red leaf lettuce in multi-metals contaminated acid soil, but the safety of red leaf lettuce is still a concern.