Effects Of Polyester Fibers On Growth Of The Eisenia Foetida

Microplastics have the characteristics that small volume,degradation difficultly,move easily and have strong adsorption power,make negative effects on the environment and organisms.The fiber-microplastics have a higher proportion of microplastics in the environment.Although soil is the main storeroom of microplastics,its harmfulness in the soil is rarely noticed of publicity.Eisenia foetida as a sensitive indicator of soil pollution and a model organism in the study of soil ecotoxicology,its growth and living conditions can play an important role in evaluating and warning the health and quality of soil.In this study,set 0,1%,2%,3%,5%concentrations of polyester fiber-microplastics treatment with Eisenia foetida for short term(15 days),medium term(28 days)and long term(200 days)culture experiment.Study on the effects of different concentrations of polyester fiber-Microplastics on the survival,growth and breed of soil organisms,and soil structure.The experimental result shows:1.In short-term culture experiment,there were significant positive correlations between the body weight growth rate of Eisenia foetida with the amount of fiber-microplastics addition,and the number of eggs laid with the amount of fiber-microplastics addition;But the number of eggs laid and the body weight growth rate by Eisenia foetida in medium-term and long-term cultures were no correlations with microplastic addition.At the same time,three groups of culture experiments also showed that fiber-microplastics had no significant effect on the mortality of Eisenia foetida.2.During the cultivation,polyester fiber-microplastics were observed in the intestines and cast of Eisenia foetida.In short term culture experiment,the amount of polyester fiber-microplastics in the cast is show monotonically increasing characteristics:5%(36±9 p/g)>3%(23±5 p/g)>1%(13±5 p/g);in the medium term culture experiment,the amount of polyester fiber-microplastics in the cast is non-monotonous.3.In the long term culture experiment,Eisenia foetida was mainly distributed in the 3-13 cm soil layer.The addition of polyester fiber-microplastics has no significant effect on the distribution of Eisenia foetida and the Eisenia foetida hole density.At the same time,the number of>2 mm water-stable aggregates in the 0-3cm soil layer treated with polyester fiber-microplastics was significantly higher than that of the 3-13cm and 13-23cm soil layers,which indicates that Eisenia foetida activities frequently in 0-3cm soil layer,resulting in in the number of water-stable aggregates was increased in soil.4.In the long term culture experiment,the number of polyester fiber-microplastics in soil water-stable aggregates formed by earthworm activities increased with the increase of polyester fiber-microplastics.At the same time,with the deepening of soil layer,the amount of polyester fiber-microplastics in water-stable aggregates were decreased.The number of polyester fibers-microplastics in water-stable large-aggregates(>0.25 mm)was significantly higher than that of micro-aggregates.(0.25-0.05 mm).In addition,<0.25 mm polyester fiber-microplastics number for the most in soil water-stable aggregates,accounting for 53%;0.25-1 mm polyester fiber-microplastics accounted for 33%;1.1-2 mm polyester fiber-microplastics accounted for 10%;2.1-3 mm polyester fiber-microplastics accounted for 3%;3.1-4 mm polyester fiber-microplastics accounted for 1%.This may be caused by Eisenia foetida miseating polyester fiber-microplastics with smaller sizes,or the fracture of polyester fiber-microplastics in Eiseniafoetida's gut.The results of this study indicate that the polyester fiber-microplastics will have a slight short-term toxic behavior on the Eisenia foetida;as the culture time increases,The effect of different amounts of polyester fiber-microplastics on the death,laied egg,body weight growth rate and Eisenia foetida hold distribution were not significant o show a non-monotonous variation characteristics.this is indicating that the toxicity of polyester fiber-microplastics to Eisenia foetida may disappear with increasing culture experiment time.On the other hand,this result also indicates that Eisenia foetida may be have a strong tolerance for polyester fiber-microplastics or the less toxic to polyester fiber-microplastics.There are many types of microplastics in the environment.The effect of a single type of microplastics on a single organism is not enough to reflect the impact of microplastics on the soil ecological environment.Therefore,further experimental research are needed to evaluate the eco-environmental effects of microplastics in soil.