Correlation Analysis Between Cultivated Land Quality And Soil Microplastic Pollution

Cultivated land is an important material basis for the agricultural production on which people depend for their survival.It is closely related to food production security and the sustainable development of agriculture,as well as to human production and life.However,with the rapid development of the social economy,plastic products have become increasingly widely and frequently used in human production and life.Existing studies have shown that large amounts of microplastics are generated during the production and use of plastic products,and microplastic pollution has become a global environmental problem.Due to the high stability and difficulty in decomposing plastic products,particles and debris entering the soil can persist for a long time,posing a serious threat to the quality of arable land.As an emerging pollutant,microplastics have rarely been investigated on a national scale,especially in terms of the impact of the study on the quality of cultivated land,which somewhat limits its application in assessing the quality of cultivated land.Therefore,it is important to further investigate the relationship between microplastic contamination and the quality of cultivated land.Exploring the accumulation and occurrence characteristics of microplastics in cultivated soil,as well as the interaction between microplastics and cultivated land quality,is conducive to protecting the quality and safety of cultivated land in China,ensuring the sustainable use of cultivated land resources,and contributing to the management of cultivated land quality in China.Based on the research idea of mutual validation between literature analysis and large-scale sampling surveys,this study summarizes and analyzes a large body of existing literature and selects a total of 34 sampling sites across the country for paired sampling.Quantitative analysis of microplastics in the soil was carried out and the physical and chemical properties of the soil were measured.The main findings and conclusions of this study are as follows:(1)The existing research on microplastics shows that the spatial distribution of microplastics pollution in China is uneven,and the content of microplastics in soil is related to land use patterns.The main types of microplastics in soil are PP and PE,with the main particle size concentrated in 0~500 μm.The main colors are white and transparent,and the main shapes are fibrous and fragmented.(2)Soil microplastics pollution is affected by agricultural management measures such as plastic film mulching.The study found significantly higher levels of microplastics in plastic film-covered farmland than in soil not covered with plastic film,at an average of 26500 N/kg and 2300 N/kg,and that the abundance of microplastics was not balanced across regions..Microplastics are mainly used in soil from 10~200 μm.The main colors are white,transparent,and yellow.The main forms are fibres,fragments and films.The results of the random forest importance ranking indicate that human activity is the main factor affecting the abundance of microplastics.(3)Plastic pollution has a significant impact on soil structure.The input of micro plastic into cultivated land has increased the proportion of mechanically stable large aggregates by >5mm,significantly increasing the mechanical stability aggregate diameter index MWD and GMD,but has no significant impact on the water stability aggregate diameter.The PAD results for farmland soils with high microplastic content were significantly higher than those for farmland soils with low microplastic content,suggesting that macroscopic aggregates in soils with increased microplastic contamination are only mechanically stable,but not water stable.(4)The correlation analysis results showed that the MWD and GMD values of mechanically stable soil aggregates and water stable soil aggregates with different microplastics abundance were correlated with the aggregate content of each particle size.For mechanically stable aggregates,the positive and negative correlation of soil aggregates with low microplastics content is bounded by 2mm,while the positive and negative correlation of soil aggregates with high microplastics content is bounded by5 mm,which proves that the input of microplastics increases the contribution of particle size fractions>5mm to the diameter of soil aggregates.For water-stable aggregates,0.25 mm is an important critical point for different microplastic abundance conditions.(5)Currently,soil physical and chemical properties are less affected by the abundance of microplastics,and the abundance of microplastics at the sampling site may not yet reach a level that can pose a threat to the health of cultivated land.The physical and chemical properties of cultivated soil are correlated with the shape,color and grain size of microplastics.Microplastics can affect the carbon and nitrogen cycling of soil to a certain extent,leading to a decline in the quality of cultivated land.The impact of microplastics on the physical and chemical properties of the soil is a complex process and the abundance,grain size and shape of microplastics should be included as indicators in an assessment system for the quality of cultivated land.