The Effect Of Microplastics On The Mineralization Of Farmland Soil Organic Carbon

Microplastics are widely present in farmland soil and have a serious impact on the soil ecosystem.In view of the potential hazards of microplastics to soil and human health,the environmental effects of microplastics in soil have increasingly attracted widespread attention from scholars at home and abroad.At present,there are few researches on microplastics in the soil environment,and the understanding of the impact of microplastics on the conversion of soil organic carbon is still very limited.This article starts with the influencing factors of microplastics on the mineralization of soil organic carbon.1mm and 25μm polyethylene microplastics(PE-MPs)are selected at different ratios(0.05g/kg,0.20g/kg,0.50g/kg,5.00g/kg,50.00g/kg)was mixed with soil and then carried out soil culture experiments to explore the influence of microplastics on soil water and heat conditions,microbial biomass,soil respiration,and organic carbon mineralization process,with a view to scientific understanding of semi-arid areas The impact of microplastics on soil carbon cycle and soil health provides a theoretical basis.The main conclusions are as follows:1.Microplastics change the soil environment,resulting in the heterogeneity of soil temperature,humidity,bulk density,porosity,crust hardness and other elements.The degree of differentiation is related to the particle size and accumulation of microplastics.Microplastics entering the soil may have a temperature increase and decrease effect of1～2℃.Add 1mm PE-MPs,the soil moisture decreases,when the addition amount is 50.00g/kg,this effect is the most significant,the decrease is 28.95%～60.10%.With the addition of 25μm PE-MPs,as the amount of microplastics increases,most of the humidity first increases and then decreases.When the addition amount is 50.00g/kg,the increase is 10.84%～62.21%.After adding PE-MPs of different particle sizes and different cumulative amounts,the soil bulk density decreased to varying degrees,and with the increase of the added amount,the degree of decrease gradually increased.When the addition amount is 50.00g/kg,the bulk density of 1mm large particle size PE-MPs and 25μm small particle size PE-MPs are 88.57%and 88.20% of CK,respectively.PE-MPs with a large particle size of 1mm have a more significant impact on soil bulk density than PE-MPs with a small particle size of 25μm,and are more sensitive to changes in bulk density.PE-MPs with a large particle size of 1mm enter the soil mainly affecting macropores and effective pores,while PE-MPs with a small particle size of 25μm enter the soil mainly affecting micropores.The addition of microplastics has a significant effect on the hardness of the soil physical crust.The effect of PE-MPs with a small particle size of 25μm on the hardness of soil crust is more significant than that of PE-MPs with a large particle size of 1mm,which reduces the hardness of soil physical crust.2.As the accumulation of microplastics in the soil increases,the water holding capacity of the soil increases first and then decreases.The accumulation of a small amount of PE-MPs in the soil(0～5.00g/kg)can enhance the soil water holding capacity,but when the cumulative amount exceeds a certain threshold(5.00～50.00g/kg),the soil water holding capacity will be significantly reduced.The large accumulation of 1mm large diameter PE-MPs has a more significant effect on reducing soil water retention;a small amount of 25μm small accumulation of PE-MPs has a more significant effect on improving soil water retention.After 1mm large diameter PE-MPs enter the soil,it mainly affects the macropores and effective pores,and has a greater impact on the effective soil moisture content;after 25μm small diameter PE-MPs enters the soil,it mainly affects the micro pores and has a greater impact on the wilting coefficient..3.Adding microplastics increases soil microbial biomass carbon,but significantly reduces soil respiration.Microplastics significantly increase the carbon content of soil microbial biomass.In the range of 0～50.00 g/kg of PE-MPs,adding 1mm PE-MPs can increase soil microbial biomass carbon content by 9.31%～60.82%;adding 25μm PE-MPs can increase soil microbial biomass carbon content by-1.73%～ 37.45%.The accumulation of microplastics will cause a significant decrease in soil respiration.In the range of 0-50.00 g/kg of PE-MPs,the addition of 1mm PE-MPs resulted in a decrease of11.6%～48.14% in soil respiration,and the addition of 25μm PE-MPs caused a decrease in soil respiration of 19.91%～42.55%.After adding PE-MPs of different particle sizes and concentrations,the soil respiration is mainly affected by soil temperature,soil moisture,effective pores,and soil microbial biomass,and the impact levels are 10%,8%,56%,and 26%,respectively.4.Microplastics have an inhibitory effect on the mineralization of soil organic carbon.Soil microplastics significantly reduce the soil organic carbon mineralization rate,and soil microplastics significantly reduce the soil organic carbon mineralization rate.Microplastics with a particle size of 1mm PE-MPs and 25μm PE-MPs reduce the soil organic carbon mineralization rate by-0.78%～29.76,respectively.% And-0.58%～26.34%.Soil microplastics significantly reduced the cumulative mineralization of soil organic carbon.Microplastics with a particle size of 1mm PE-MPs and 25μm PE-MPs reduced the cumulative mineralization of soil organic carbon by 2.23%-26.00% and-0.62%-19.41,respectively.The addition of microplastics reduces the mineralization potential of soil organic carbon,and 25μm PE-MPs has a significant effect on the mineralization potential of organic carbon and the value of the mineralization rate constant..