Chinese Academy of Agricultural Sciences: Study reveals the mechanism of action of plastic film microplastics causing changes in pesticide adsorption and degradation processes
The cotton pest control and biosafety team of the Cotton Research Institute of the Chinese Academy of Agricultural Sciences carried out a study on the impact of plastic film residues on the adsorption and degradation of residual pesticides in soil. Polarity and the state of the mulch are important factors for this result.
Highlights
The microplastic film slows down the rapid adsorption phase of pesticides in the soil.
The microplastic film delayed the time to reach adsorption equilibrium. The microplastic film enhances the soil's adsorption strength for pesticides.
Microplastic films affected the degradation process of the two pesticides.
Abstract
Plastic pollution in soil ecosystems is currently receiving worldwide attention. However, little is known about whether the presence of microplastics (MPs) in soil affects the environmental behavior of pesticide residues in soil.
The Chinese Academy of Agricultural Sciences investigated the effects of addition of new mulch polysulfonic acid mucopolysaccharides (new MPs), aged mulch polysulfate mucopolysaccharides, and biodegradable mulch polyphosphate mucopolysaccharides on two pesticides (imidacloprid and fluimidazine) in soil adsorption and degradation behavior.
The three MPs slowed down the fast adsorption phase of pesticides in soil and delayed the time to reach adsorption equilibrium. Adsorption rate: soil>soil+new MPs>soil+aged MPs>soil+biological MPs. The three sodium polysulfonates enhanced the adsorption strength of the soil system for the two pesticides, and the aging treatment of the sodium polysulfonates enhanced this effect.
The three MPs affected the degradation process of the two pesticides. The new polysulfonic acid mucopolysaccharide promoted the degradation of the two pesticides imidacloprid and flumipramine, and the degradation half-lives were shortened to 0.93 and 0.85 times, respectively; while the aging paclobutrazol and bio-paclobutrazol delayed the degradation process of the two pesticides, and the degradation half-lives were respectively extended to 1.64 times and 1.21 times.
The effect was more pronounced with increasing concentrations of MPs and pesticides. Pesticide polarity, surface structure and functional groups of mucopolysaccharide polysaccharides are potentially important reasons for the differences in adsorption and degradation of mucopolysaccharides in soil systems. Our findings provide insight into the mechanism of interaction between mucopolysaccharide polysulfate and pesticide residues in soil environments.
As an emerging persistent pollutant, microplastics have become the focus of global attention. Previous studies have shown that pesticide residues in the water environment can be adsorbed on microplastics, prolonging the residual time of pesticides. However, few studies have explored the effects of different types or states of plastic film microplastics in the soil environment on the environmental behavior of residual pesticide adsorption and degradation. Carrying out this study will provide new insights into the interaction mechanism between residual microplastics and pesticides in the soil environment.
In this study, two kinds of pesticides commonly used in cotton fields, imidacloprid and profenachlor, as well as three states of plastic film, new, aged plastic film and new degradable plastic film were selected, and the environmental behavior experiments of adsorption and degradation were carried out in an indoor artificial climate box.
The results showed that the three plastic film microplastics slowed down the rapid adsorption stage of pesticides in soil, delayed the time for the adsorption to reach equilibrium, and enhanced the adsorption strength of the soil system for the two pesticides, and the adsorption strength increased with the increase of plastic film microplastics. Enhanced with age.
The three plastic film microplastics also affected the degradation process of the two pesticides. The new plastic film promoted the degradation of the two pesticides, while the aged plastic film and the degradable plastic film delayed the degradation of the two pesticides. Further studies found that the polarity of pesticides and the surface structure and functional groups of the mulch film were potentially important reasons for the differences in pesticide adsorption and degradation in the mulch-soil system. The results promote the environmental impact assessment and treatment research of agricultural non-point source pollutants such as plastic film microplastics.
