Effect Of Polyester Microfibers On Soil Physical Properties

Microplastics pollution has become a major ecological and environmental issue of global concern.At present,there are many studies on the impact of microplastics in aquatic ecosystems,but there is a lack of concern and attention to the ecological environment risks generated by microplastics in terrestrial ecosystems.Polyester fiber is currently the most productive plastic product and is widely distributed in the environment.In this study,the effects of polyester microfibers entering the soil on the physical properties of the soil and the distribution characteristics of polyester microfibers in the soil were investigated through field and indoor culture experiments.The main results are as follows:1.Compared with the control treatment,the addition of polyester microfibers in the field and indoor culture experiments had no significant effect on the soil bulk density,but the addition of polyester microfibers significantly increased the number of>30?m in the soil pores and reduced the number of<30?m in the soil pores.Field experiments found that there was no significant difference between the saturated water conductivity of the soil treated with polyester microfibers and the control treatment,which indicated that the water stability of the>30?m pores treated with polyester microfibers was lower.2.In the field and indoor culture experiments,the effect of adding polyester microfibers on the distribution of soil water-stable aggregates was different.The results of field experiment showed that the addition of polyester microfibers had no significant effect on the distribution of soil water-stable aggregates compared with the control treatment,while the addition of organic materials significantly increased the number of>2mm water-stable aggregates in the soil.However,the results of indoor culture experiments showed that the addition of polyester microfibers and organic materials significantly increased the water-stable large aggregates(>2mm)in the soil.Due to the finer soil particles after sieving used in the indoor culture experiments,the polyester microfibers are easily entangled in the dry-wet alternating process to formation of larger soil structure;while the soil structure is larger in the field experiments.The added polyester microfibers may only adhere to these existing structures,and thus have little effect on the formation of soil water-stable aggregates.These results indicate that the effect of polyester microfibers on soil structure is also affected by the size of the soil particles.3.Field and indoor culture experiments showed that the addition of polyester microfibers had no significant effect on soil total organic carbon content.The results of indoor culture experiments showed that there was no significant difference between the content of organic carbon in the soil microaggregates treated with polyester microfibers and the control treatment,however,the content of organic carbon in the water-stable aggregates(2-0.25mm)treated with polyester microfibers was significantly higher than the control treatment.This indicates that polyester microfibers have a certain effect on the distribution of soil organic carbon.4.Field and indoor culture experiments showed that the more the amount of polyester microfibers added in the soil,the higher the total amount of polyester microfibers entering the soil aggregates;and the proportion of microplastics in different particle size aggregates.The proportion of aggregates of various particle sizes in the soil is related.The distribution of particle size of polyester microfibers in soil aggregates showed obvious normal distribution,but the average length of polyester microfibers in large agglomerates was significantly higher than the average length of polyester microfibers in microaggregates.In addition,the field experiments results showed that the polyester microfibers in the topsoil migrate to the deep soil.