Structural Analysis And Pollution Evaluation Of Microplastics In Soil Mulched By Dust-proof Nets In Beijing

As a driving factor of global change,microplastics have attracted widespread attention.Despite extensive research on microplastics in marine and freshwater systems,the pollution and behavior of microplastics in terrestrial ecosystems and soil are still not fully understood.It is worth noting that microplastic pollution in soil was maybe 4-23 times higher than in the marine environment.The Air Pollution Prevention and Control Law of the People’s Republic of China stipulates that for construction land that cannot be started shortly,the relevant unit shall cover the bare ground;if it takes more than three months,it shall be greened,paved,or covered to reduce the risk of damage.Some air pollution problems are caused by dust.Considering that plastic dust-proof nets have low production costs,are simple to use,and have apparent visual effects,many dust-proof nets are covering the soil of construction land,which may cause soil microplastic pollution and increase ecological risks.To(1)determine whether the soil covered by the dust net is contaminated by microplastics,(2)explore the crucial sources of microplastics in the soil covered by the dust net,(3)estimate the accumulation of microplastics in the soil covered by the dust net in Beijing,(4)To evaluate the impact of microplastics pollution on the soil ecosystem,we conducted a case study in Beijing.A comprehensive and effective method for separating microplastics in soil was established by collecting samples of soil covered and uncovered with dust-proof nets in Beijing(surface layer 2 cm).This method was used to separate microplastics from soil successfully.Through a stereo microscope,micro-Fourier transform infrared spectrometer(μ-FTIR),and scanning electron microscope(SEM),the abundance,shape,size,polymer type,and surface microscopic characteristics of the separated plastic particles are studied.The study results showed that the abundance of microplastics in the soil covered by the dust net was 272-13,752/kg,with a median value of 4680/kg.Large particles(>1000 μm)of plastics accounted for 49.83%of the microplastics in the study area.The polymer types of microplastics are mainly polyethylene(50.12%)and polypropylene(41.25%).The surface of the microplastics shows signs of aging and degradation,including uneven protrusions and pits,irregular holes,and attached particles.The cumulative amount of microplastics in the soil covered by the dust-proof net(average 4910.2/kg)was higher than that of the uncovered soil(average 840.8/kg)(P<0.05).They obtained high-spatial-resolution multi-spectral remote sensing image data from remote sensing satellite images.They combined it with a deep convolutional neural network to automatically detect and segment the dust-proof net,extracting the entire Beijing dust-proof net covering an area of 7 km2.By combining the abundance of microplastics in the soil per unit area of dust-proof nets and the coverage area of dust-proof nets in Beijing,it is roughly estimated that the accumulation of microplastics in the soil is covered dust-proof nets in Beijing is 7.616×l09-3.581×1011.This research has developed a comprehensive and effective method for separating microplastics in the soil to realize the effective detection and analysis of microplastics in soil,which has specific application prospects.Taking Beijing as an example,this article reveals the prevalence of microplastic pollution in the soil and the pollution characteristics of microplastics in the soil covered by dust-proof nets.Residual and broken dust-proof nets may be the main source.Moreover,through the convolutional neural network to extract the coverage area of the Beijing dust-proof net,combined with the abundance of the dust-proof net per unit area,a rough estimate of the accumulation of microplastics in the soil covered by the dust-proof net in Beijing,and then explore the environment The potential hazards of microplastics to soil organisms.This research will strengthen scientists’ and policy makers’ understanding of soil microplastic pollution and its environmental impact.Provide advice to decision-makers to formulate effective legislation and policies to protect the soil and the wider environment.