Study On The Pollution Status And Adsorption Behavior Of Microplastics And Heavy Metals In The Soil Of Coal Mining Subsidence Area

As a new type of pollutant,microplastics are ubiquitous in various environmental media.Microplastics in the soil have a great impact on the environment and have received more and more attention in recent years.Under the conditions of underground mining,the original landform will change,forming large-scale coal mining subsidence areas,changing the water cycle in the soil and the migration of pollutants,especially the occurrence of heavy metals.The paper took the Huaibei Zhuzhuang Mine and the Huainan Panyi Mine as research areas to investigate the microplastic pollution status and evaluate the heavy metal pollution status.The adsorption behavior of microplastics to heavy metals was experimentally studied with typical microplastic polypropylene(PP)particles,and then discussed the occurrence characteristics of microplastics and heavy metals in mining subsidence area.The main conclusions are as follows:(1)The investigation of microplastic pollution shows that:Microplastics were detected in the soil of Zhuzhuang Mine and Panyi Mine in the study area.The abundance of microplastics in the surface soil of Zhuzhuang Mine is greater than that of Panyi Mine,and the influence of human activities may be the main reason.(2)The evaluation of the pollution status of heavy metals shows that:Among the six heavy metals analyzed(Pb,Zn,Cu,Cd,Ni,Cr),the lead in the heavy metals in Zhuzhuang mine exceeded 1.4 times,and the zinc in the Panyi mine exceeded 4.8 times.In both mining areas,the status of heavy metal pollution in soil is good,and the potential ecological risk index is also relatively small,but the soil condition of Panyi mining area is generally inferior to that of Zhuzhuang mining area.(3)Studies on the adsorption behavior of microplastics to heavy metals show that:The adsorption process of four heavy metals(Pb,Zn,Cu,Cd)by microplastics can be better fitted with a second-order kinetic model,and the adsorption behavior can reach equilibrium in 36 hours.Kinetic experiments indicate that surface adsorption and intra-particle diffusion may be the main adsorption mechanism of microplastics to four heavy metals.The adsorption isotherm data can be better fitted by Freundlich model,and the Langmuir model shows that the adsorption process is all favorable adsorption.The adsorption of mixed heavy metals by microplastics indicates that when the concentration of mixed adsorbate is low,the coexistence system can promote the adsorption of lead and copper by microplastics.But with the increase of the mixed concentration,all the adsorption is inhibited.The relationship between ion concentration and adsorption capacity is not clear.The increase of K+concentration will promote the adsorption of Pb but inhibit the adsorption of Zn,Cu and Cd by microplastics.Fig.[21]Table[16]Reference[121]...