Quantity And Distribution Of Microplastics In Farmland Soil Of Lake Shore In Dianchi Lake

At present,the influence of <5mm plastic particles(ie,microplastics)on the ecological environment has aroused strong concern.As a new type of persistent environmental pollutant,the harm of microplastics to Marine ecosystem has been confirmed and studied in depth.However,research on microplastics in terrestrial ecosystems,especially in soils,has not yet been carried out in depth.The Dianchi Lake Basin is the earliest area in Yunnan to carry out large-scale vegetable and flower production.Due to the long-term use of large amounts of agricultural plastic products and the history of sludge farming,there may be a large amount of microplastics accumulated in the farmland soil in this area.However,lacking of assessment of microplastics in the soil will adversely affect the maintenance of farmland soil health.Therefore,this paper collected the Surface soil samples from farmland and lakeside buffers with different facilities cultivation time in this area,the amount,shape and size of microplastics in soil and its water-stable aggregates were analyzed,attempting to explore the distribution characteristics of microplastics in Farmland Soil in this Lake Basin Area.The results show that:1.The microplastics were detected in all soil samples,indicating that the microplastic is common in the soil of this area.The content of microplastics in soil in this area is in the range of 13020-28100n/kg,with an average content of 19660n/kg;The microplastics in the soil are mainly fibrous,accounting for 92.69% of the total amount of microplastics,while the thin films,fragments and cord microplastics account for 3.24%,3.89% and 0.17%,respectively.2.Data analysis shows that there are significant differences in the content of different sizes of microplastics in the soil.Microplastics of 0.05-0.25 mm,0.25-1 mm,and >1 mm respectively accounted for 82.54%,12.66%,and 4.81% of the total amount of microplastics,and the number of 0.05-0.25 mm microplastics was significantly higher than 0.25-1 mm and >1mm fraction,which indicates that with the decrease of microplastics size,number of microplastics accumulation in soil increased.3.The color of microplastics in the soil of this area is mainly transparent,purple,blue,and yellow,accounting for 54.74%,33.80%,8.37%,and 1.19%,respectively,and the remaining 1.90% are red,green,black and other colors.This distribution characteristic may be related to the color of agricultural plastic products or the habits of local farmers in selecting plastic products.4.According to the study data,71.38% of the microplastics in the soil of the study area were distributed in water stable aggregates,while 28.62% of the microplastics were distributed.At the same time,the microplastic content in soil water stable microaggregates of 0.25-0.05mm(30060n/kg)was significantly higher than that of > 2 mm and 2-0.25 mm large water stability of aggregate(14680 n/n/kg and16730 kg),this may be due to the fact that microaggregates with high microplastic content are difficult to be agglomerated into large agglomerates.On the other hand,it also suggests that microplastics may have an adverse effect on the stability of soil structure.Due to the large amount of water stable macroaggregates in the soil in this area,the total accumulation of microplastics in soil water stable macroaggregates is significantly higher than that in microaggregates.In addition,the cumulative amount of microplastics in soil water stable aggregates is also affected by the size and shape of the microplastics.5.The microplastic content(15030n/kg)in the soil of the buffer zone is significantly lower than that in the adjacent farmland soil(27050n/kg),indicating that the agricultural activity is the main reason for the high accumulation of microplastics in farmland soil.At the same time,the content of thin films microplastics in farmland soil with different facility cultivation time are lower,it only account for about 5% of the total amount of microplastics,indicating that the greenhouse film contributes little to the amount of microplastics in soil.Contrast found that the microplastic content(24130n/kg)in the gleysols soil was significantly higher than that of the ferrisols soil(14060n/kg),this may be due to the fact that Irrigation Water Source of gleysols farmland is mostly sewage which from nearby villages.In addition,there is no significant difference in the content of microplastics in 0-5cm and 5-10 cm soil layers due to the tillage rotation.The above results showed that the accumulation of microplastic in the surface soil of Chai River Basin in southern Dianchi is huge,and the microplastic size is relatively small,Therefore,the influence of micro-plastics on soil structural stability needs to be studied in-depth.