Effect Of Prothioconazole On The Degradation Of Microplastics Derived From Mulching Plastic Film And Analysis Of Pollution Characteristics

Microplastic pollution has been listed as the second largest scientific issue in the field of environmental and ecological science research,and has become a major global environmental issue alongsideglobal climate changes,ozone depletion and ocean acidification.The content of microplastics in soil has surpassed the water environment as the main environmental reservoir.However,compared with the water environment,microplastics are relatively neglected as invisible pollutants in terrestrial ecosystems.Up to now,plastic mulch residue has become one of the main sources of microplastic pollution in farmland soil.As the country with the largest mulching area in the world,china residual pollution is very serious.In order to reduce the pollution of plastic film residue,biodegradable plastic film was gradually used in agricultural production.But compared with ordinary polyethylene mulch,it will not be completely degraded when exposed to sunlight and oxygen,but will break into a large number of microplastics,and accumulate in the soil environment,which bringing the potential environmental hazards.Microplastics will absorb various types of pollutants such as hydrophobic organic compounds and heavy metals in the environment,and release various toxic and harmful additives at the same time.It leads to the ecological risk.In agricultural soil,the pesticides which adsorbed on the surface of microplastics will migrate into the interior of microplastics and accelerate its degradation.Some studies have found that sulfur/chlorine pesticides could promote the degradation of plastic film in the soil,but currently there is no relevant research to discuss the impact of pesticides on the degradation of microplastics derived from mulching plastic film.Therefore,this topic takes common polyethylene(PE)film,biodegradable polyadipate/butylene terephthalate(PBAT)film source microplastic as the research object,and selects prothioconazole which is a new broad-spectrum and highly effective fungicide as the representative compound.Investigate its effect on the degradation of microplastics derived from mulching plastic film under soil environmental conditions.And explore the adsorption and release behavior of microplastics to heavy metals and organic pollutants during the degradation process.The main research contents are as follows:(1)The effect of prothioconazole on the degradation of microplastics: simulated degradation experiments were carried out on PE and PBAT microplastics,and the degradation results were characterized by ATR-FTIR and SEM to study the effect of prothioconazole on the degradation of microplastics.The results show that: in the soil environment,a)no matter whether prothioconazole is added,the number of hydroxyl functional groups and cracks generated on the surface of PBAT is higher than that of PE microplastics;b)After the addition of prothioconazole,the cracks on the surface of these two types of microplastics increased significantly,indicating that in the soil environment,both types of microplastics PBAT and PE will degrade.The degradation rate of PBAT microplastics is higher than that of PE microplastics,and prothioconazole promotes the degradation of these two types of microplastics.In the absence of soil,the functional groups and morphology of the microplastic surface did not change significantly.It shows that the degradation of microplastics derived from mulching plastic film is not only affected by the single factor of light,but also by various soil conditions such as pesticides and other environmental pollutants,microorganisms,water and so on.(2)Characteristics of heavy metal pollution during the degradation of microplastics: In the simulated degradation experiments of PE and PBAT microplastics,ICP-MS was used to characterize the soil and microplastics during the degradation process.The heavy metal pollution characteristics of two types of microplastics derived from mulching plastic film were studied with or without prothioconazole.The result show that: For the heavy metals arsenic,barium,chromium,and lead,these types are common heavy metal pollutants in the soil environment.Their concentration in the soil is higher than that in the microplastics.They will be gradually absorbed by the microplastics.Prothioconazole will hinder the adsorption of microplastics to metals.For the heavy metal tin,because it is often used as a stabilizer added in the mulch,its concentration in the mulch is much higher than that in the soil,it will be gradually released into the soil.Prothioconazole has little effect on the release of tin.For heavy metal copper,its concentration in soil is similar to that in microplastics.Prothioconazole will promote microplastics to adsorb copper in soil.Because PBAT has a faster degradation rate and a larger specific surface area,its adsorption capacity for these heavy metals is generally higher than that of PE.Therefore,the adsorption and release behavior of microplastics derived from mulching plastic film in the soil is a complex dynamic process.Prothioconazole will affect this process.Compared with PE microplastics,PBAT will show a greater negative impact.(3)Characteristics of organic matter pollution during the degradation of microplastics: In the simulated degradation experiments of PE and PBAT microplastics,the soil during the degradation process was subjected to ultrasonic extraction and characterized by GC-MS.Analyze the organic pollution characteristics of two types of microplastics derived from mulching plastic film with or without prothioconazole.The results show that: In the soil environment,the degraded plastic film source plastic will release the plasticizer bis(2-ethyl)hexyl phthalate into the soil.Compared with naturally degraded microplastics,after the addition of prothioconazole,the release time of phthalic acid plasticizers is earlier.Compared with PE microplastics,the degradation process of PBAT microplastics can detect phthalate compounds earlier.Therefore,in the soil environment,prothioconazole will promote the release of plasticizers in the two types of plastic film source plastics of PE and PBAT,and the release rate of plasticizers in PBAT is faster,with greater potential risks.The research results of the thesis will help to correctly understand the impact of the degradation process of microplastics derived from mulching plastic film on the soil ecological environment.Provide scientific basis for the scientific and standardized use of agricultural mulch and the rational development of biodegradable mulch.Accurately assess the potential risks of pesticides and microplastics derived from mulching plastic film on soil ecological environment,crops and human health.