低分子量聚乙烯对土壤氮含量及相关酶的影响

Influence of Low Molecular Weight Polyethylene on Nitrogen Contents and Related Enzyme Activities in Potted Wheat Soil

环境降解地膜可在较短时间内碎片化,并进一步由碎片降解为粉末状的低分子量聚乙烯(LMWPE)。利用不同分子量聚乙烯粉末模拟环境降解地膜降解后的聚乙烯组分,将3种不同分子量LMWPE(M1=2000、M2=5000、M3=100 000)添加到盆栽土壤中种植小麦,测试分析小麦不同生育期土壤氮含量及两种关键酶活性变化,为环境降解地膜的环境安全性评估提供实验依据。结果表明:处理组土壤全氮、碱解氮含量在小麦分蘖期、孕穗期、开花期等显著低于对照组,土壤脲酶活性在拔节期至灌浆期受到显著抑制,不同分子量LMWPE处理对小麦各个生育期土壤蛋白酶活性的影响未达显著水平。LMWPE可在一定程度上降低土壤供氮能力,土壤氮素转换受到一定程度的抑制。以LMWPE为原料的环境降解地膜的环境安全性有待进一步探究。

The environmental degradable mulch film （EDMF） can be broken down into smaller bits or powdered residues with decreased molecular weight in a short period, which have provided an available way for solving the white pollution in field ecosystem. The powdered residues in soil have strong hydrophobicity and maybe very slow to be degraded completely. There were much more argument about the en- vironmental biology effects of the mulch film residues on soil microenvironments and crop growth. In the study, it was imitated that the EDMF were broken down into the powdered polyethylene components under natural conditions by adding three kinds of low molecular weight polyethylene （LMWPE） which had different molecular weight（M1 =2000, M2=5000, M3= 100 000） into the pot-soil and seeded wheat under natural conditions, and nitrogen contents and related enzymes activities in the soil were analysed during the ~period of wheat growth for providing the evidences of evaluating the environmental safety of degraded residues of EDMF in soil. The results showed that total nitrogen contents and effective nitrogen contents in the pot-soil were lower significantly compared with CK（The group without LMWPE added） during tillering stage, booting stage and florescence, the activities of soil urease were inhibited markedly through jointing stage to filling stage, but activities of soil protease were hardly influenced during whole growth period. It is Suggests that deliverability of soil nitrogen contents has been decreased by treatments of powdered LMWPE added into the pot-soil and the environmental security of EDMF needs to be further investigated.