Characteristics Of Microplastics Pollution Along The Jialing River Coast,and Responses Of Fungi To Microplastics/Plastic Leachates

Plastic is ubiquitous because of its hydrophobicity,difficult degradation,and low density.Plastic particles are found in coastal beaches,deep-sea sediments,inland soil,polar glaciers,and even atmospheric dustfall.Plastics are easily mistaken for food being eaten by animals,and plastic causes gastrointestinal ulcers that cannot be excreted accumulates in the organism.Microplastics will also become new carriers to transfer microorganisms,heavy metals,persistent organic matter,etc.Plastics with a particle size smaller than 5mm are defined as microplastics,and the study of their effects on fungi in the environment is helpful to evaluate the effects of microplastics on the ecosystem.This paper is divided into two parts.The first part is to investigate the soil micro plastic pollution along the Jialingjiang River(Beibei,Shapingba,Yuzhong District,the main urban area of Chongqing).The micro plastic particles in the soil are separated by air flotation method,screened and classified,and the surface morphology of the plastic after natural weathering is observed by SEM.At the same time,the micro plastic extracted from the soil,and soil is determined by its primer.The diversity of fungi on the surface of the material was analyzed.In the second part,the response of fungi to plastic was studied from the point of view of microparticle size and plastic dissolution.The effect of microparticles and solutes on fungi was reflected by measuring enzyme activity,lignin degradation rate and dye color change.Then,the thickness of biofilm on plastic surface was observed by SEM scanning electron microscope.After the interaction between plastic and fungi,the molecular structure of plastic surface was analyzed by Raman spectrum.TOC analyzer and UV spectrum were used to analyze the artificial solar radiation.The nature of the plastic dissolution under the conditions.(1)In the soil along the Jialing River,the particle size distribution of microplastics ranges from 0.05 mm to 5mm,in which the microplastic content of 0.1-0.5mm is the most,and that of 0.05-0.1mm is the least.The number of plastics whose particle size is smaller than 1mm decreases along the flow direction,while the number of microplastic particles whose particle size is larger than 1mm is on the contrary.The content of transparent microplastics was the highest,followed by white,black,and color(red,green,blue)microplastics.The average abundance of microplastics in waterside,shore,and the slope is 13.40 ±11.17/kg soil,15.13 ±11.09/kg soil,and 7.12 ±5.18/kg soil,respectively.Because the soil has a certain fixation effect,microplastics accumulate in a certain range,and the migration capacity is limited.Along the flow direction of Jialing River,the average abundance of microplastics decreases gradually,and the number of microplastic particles in the upstream is larger than that in the lower reaches.Due to the use of agricultural film in rural areas,the abundance of plastic is relatively high.Therefore,it is suggested to control the use of agricultural mulch film in rural areas,increase the reuse frequency of agricultural mulch film,and carry out unified recycling and treatment,further improve the recycling and centralized treatment system of plastic waste in rural and economically backward areas,and develop and use biodegradable plastic;plastic waste collection in urban areas The collection system is relatively perfect,but we still need to increase the number of recycling of plastic products,and actively implement waste classification,and strive to reduce the amount of plastic waste from the source.(2)The fungal community on the surface of the soil sample and microplastic changed obviously.The abundance and diversity of fungi on the surface of microplastics were higher than those in soil samples,and some fungi did not exist in soil on the surface of plastics,such as Trichoderma and Aspergillus.Penicillium coexisted in soil and microplastics,but its abundance increased significantly on the surface of the plastics sample.In the soil environment,the location of each microplastics becomes a new microbial hotspot.The organic pollutants,heavy metals and other substances absorbed by microplastics can be transformed and degraded.Therefore,the hotspot of microplastics needs further attention and research.(3)polyethylene terephthalate(PET)promoted laccase production by Fusarium oxysporum,but inhibited manganese peroxidase and lignin peroxidase production.With the decrease of PET fragments,the inhibitory effect on manganese peroxidase activity was enhanced,while laccase and lignin peroxidase activity did not change with the particle size decreases of PET.When Fusarium oxysporum degraded lignin,PET promoted the activity of lignin peroxidase,inhibited the activity of manganese peroxide,and inhibited the degradation rate of lignin.When the PET fragments are smaller,it is easier to colonize thicker biofilms.Fusarium oxysporum did not change the molecular structure of PET fragments in a short time.The degradation of lignin is the rate limiting step of carbon cycle.If the degradation rate of lignin is inhibited,the amount of carbon dioxide will be reduced.Therefore,microplastics in the environment may play a positive role in reducing carbon dioxide flux.(4)Following irradiation of artificial sunlight,the TOC content of plastic dissolution PE > PP > PET,filtered out ultraviolet light,the TOC content of plastic dissolution decreased significantly,but it was still higher than that of TOC in the dark.The absorbance trend of the dissolution is PE > PP=PET > dark control > light control.After filtering ultraviolet light,after 7 days of radiation,the absorbance trend of the dissolution is: PE=PET > PP > dark control > light control.This experiment shows that different light radiation produces different characteristics of plastic dissolved matter,and the production of dissolved matter is also different between day and night;and PE is the most easy to aging,so more attention should be paid to PE plastic products in daily use.(5)The effect of PE leachates on manganese peroxidase production by Phanerochaete chrysosporium showed no obvious dose relationship.At the initial stage of the reaction,the PE leachates could stimulate the secretion of manganese peroxidase,but with the extension of the reaction time,the manganese peroxidase was finally inactivated.The higher the concentration of PE leachates,the earlier the manganese peroxidase was inactivated.It shows that the negative effects of plastics and their exudates on the environment are long-term.In the presence of plastic leachates,the ability of Phanerochaete chrysosporium and Fusarium oxysporum to degrade methylene blue was enhanced,and the discoloration rate of methylene blue was accelerated,and the discoloration rate of methylene blue was as follows: PE leachates >PP leachates > PET leachates,but there was no obvious dose relationship.The ability of Fusarium oxysporum to degrade methylene blue was higher than that of Phanerochaete chrysosporium.This experiment shows that PE is easy to age,but the bioavailability of its dissolution is also the highest.