不同棚龄土壤重金属含量变化及污染评价

为揭示设施大棚中土壤重金属的变化趋势,采用单因子污染指数和综合污染指数法研究了浙江金华市郊不同棚龄的设施大棚土壤中污染重金属的积累现状.结果表明,设施大棚中施用规模化养殖畜禽粪,使土壤重金属(Cr、Pb、Cu)含量随棚龄(0～8 a)增加而递增,且两者之间呈显著的正相关关系,特别是土壤Cu含量平均以7.565 mg/(kg·a)的速度增加,导致有24.14％的设施土壤Cu含量超标；而Cd含量变化没有明显的规律性.并且,5a棚龄设施土壤有75％达污染警戒限水平(2级),而棚龄8a设施土壤100％都达到或超过了污染警戒限水平.可见,目前的栽培管理条件下,设施栽培导致重金属积累,设施土壤清洁使用的临界年限大约5a.建议在设施栽培过程中尽量使用经堆制腐熟的畜禽粪等有机肥料,并适时采取灌水治理、施用石灰氮、植物修复等措施,以保证设施栽培土壤环境的生态安全.

Content Changes and Pollution Evaluation of Heavy-metals in Different Cultivation Ages of Greenhouse Soils

The status quo of heavy-metals accumulation in the different cultivation ages of greenhouse soils from Jinhua suburb was studied.The results showed that when applying manures from big scale farm to the greenhouse soil,the contents of heavy-metals(Cr,Pb and Cu) in greenhouse soil increased with increasing cultivation age(0-8 years),and there were significant positive correlation between them;particularly,when Cu content in the soil increased at an average annual rate of 7.565mg/kg,the Cu content in 24.14% of the greenhouse soil exceeded standard,but the change of Cd content had no apparent regularity;75% of the greenhouse soil with five years cultivation age reached the second level of warning limit,and 100% of the greenhouse soil with eight years cultivation age exceeded the warning limit level.Therefore,under the present cultivation management conditions,the greenhouse cultivation will lead the accumulation of heavy metals,and critical period of the greenhouse soil for clean use was about five years.It suggested that during cultivation process in the greenhouse,using organic fertilizers,such as composting manures,as much as possible;meanwhile,adopting some measures timely,such as irrigation treatment,applying lime nitrogen and phytoremediation,to ensure the ecological safety of the greenhouse soil.