The Influence Of Residual Plastic Powder On The Soil Environment

In view of long-term effect of residual plastic powder on the soil environment,adopted the controlled plant body-root cellar experiment. Under the influence of accumulation of above 5 years in a row,2 crop planted every year, the soil enzyme activity,soil physical and chemical properties and soil microbial biomass of different soil types which added the different molecular weight polyethylene and polyethylene cumulative residual were tested, and investigated the influence of polyethylene powder on the soil environment according to the results. Meanwhile,the degradation behavior of mulch residual powder were explored in different soil environments. The results indicate that:(1) The influence of mulch residual powder on the soil enzymes.The average urease activity was 191.62?g/(g*d), the sucrase was 254.32?g/(g*h),decreased respectively 0.30% and 2.80%.Mulch residual powder have different degree of negative impact on urease and invertase activity after five years.The average phosphatase activity was 327.34?g/(g*h),1.90% more than the control group.The processings performanced comprehensive activation effect on phosphatase.Five years consecutive planting,the difference of three kinds of enzyme activity that residual plastic powder impacted on was not significant.(2) The influence of mulch residual powder on the soil physical and chemical propertiesFive years consecutive planting,the average value of pH,CEC(cation exchange capacity),organic matter and alkali-hydrolyzale nitrogen of all treatments was 7.77,10.60cmol(+)/kg,18.38g/kg and 115.70mg/kg in corn whole growing period, slightly increased by 0.3%,0.3%,0.4% and 1.8%, respectively. And the average content of available phosphorus and available potassium were 42.48mg/kg and 215.38mg/kg,respectively 2.9% and 7.5% decreased compared with the controls.Low molecular weight,large residue had the strongest positive effect on the available phosphorus,and large molecular weight and large residual impact had the largest negative effects on available phosphorus;Low molecular weight and low residue treatment promoted rapidly-available potassium, and large molecular weight and large residual amount had a strong negative impact.(3)The effect of mulch residual powder on the soil microbial biomassFive years consecutive planting,the mulch residual powder increased soil MBC(microbial biomass carbon) and MBN(microbial biomass nitrogen).The average content of soil microbial biomass carbon (MBC) was 326.47?g*C/kg,increased 2.7% by compared with 317.95?g*C/kg.This showed that residual powder had a slight boost on microbial biomass carbon film. The average content of each process in all the birth of the microbial biomass nitrogen (MBN) was 79.28?gN/g,increased 6.86% by compared with the contrast average content of 74.19?gN/g,which showed that residual powder integrated membrane showed certain activation function on the microbial biomass nitrogen.After 2000 and 5000 low molecular weight polyethylene powder of larger residues entered into the soil,MBC and MBN be markedly increased.(4) The influence of different soils environment on mulch residual powder structure.The extraction rate of residual plastic powder decreased significantly after five consecutive years of planting. The average extraction rate of mulch residual powder fell by 13.47%.The molecular weight of 2000 processing had been difficult to extract. The average extraction yield of LLDPE(linear low density polyethylene) treatment groups was 24.80%, compared to 24.94% of two years ago, declined 0.7%.Infrared spectrum showed that the oxygen-containing groups and the characteristic structure were changed after five years of planting. The crystallization peak temperature of residual plastic powder of 5000 molecular weight was 107.26?. Initial melting temperature of residual powder of LLDPE after processing was 118.93?, control experiment 115.03?. Peak average melting temperature was 126.26? residual powder of LLDPE after processing, and the control experiment was 122.83?.The SEM surface of residual plastic powder dealt by molecular weight of Mn=2000/5000 become porous, and which have little bar or crack, but the change of SEM surface of residual plastic powder dealt by LLDPE was not obvious.