Study On The Combined Toxicity And Toxicity Mitigation Mechanism Of Polystyrene Microplastics And Arsenic On The Early Growth Of Wheat

The presence of microplastics in terrestrial ecosystems has gained significant attention globally.Research has revealed that microplastics combined with arsenic can have a compounded toxic effect on crops,posing new challenges for the prevention of soil pollution and assessment of environmental health risks.Current research primarily focuses on the ecotoxicology of microplastics and arsenic,with limited understanding of the mechanism underlying their compounded toxicity in soil,and a lack of effective measures to control this toxicity.This study investigated the compound toxicity of Polystyrene microplastics(PSMPs)and arsenic on wheat germination and seedling growth through a chain research idea,focusing on three aspects: soil environment,soil-plant interface,and plant body.And as a common iron mineral in soil,goethite was used to explore its potential for mitigating the compound toxicity of PS-MPs and arsenic.The study examined the impact of As,PS-MPs,and goethite interaction on chemical speciation and pollutant distribution in the soil environment,and the interfacial processes of PS-MPs and As on wheat roots and the effect of goethite on these processes at the soil-plant interface.Furthermore,the study explained the relationship between PS-MPs and arsenic in wheat based on the pollutants’ enrichment and distribution,as well as the balance of the oxidation-antioxidation system.Finally,the study investigated the effects of combined pollution on wheat germination and growth,as well as the changes in the combined toxicity of PS-MPs and arsenic mediated by goethite.The paper’s primary research findings are presented as follows:(1)PS-MPs and/or goethite are known to adsorb arsenic in soil,thus reducing its bioavailability.In the presence of both microplastics and goethite,the adsorption of arsenic is further enhanced through ligand exchange and-OH activation.(2)Due to the adsorption of arsenic by PS-MPs,on one hand,PS-MPs can fix arsenic and reduce its uptake by wheat.On the other hand,can release arsenic adsorbed on the surface and increase its accumulation in wheat.During the germination stage of wheat seeds,PS-MPs mainly fix arsenic,but during the seedling stage,PS-MPs enter the wheat body in large amounts,leading to increased accumulation of arsenic and aggravated toxicity.(3)Goethite can promote the formation of an iron plaque on the surface of wheat roots,thereby reducing the absorption of PS-MPs and arsenic by wheat.In addition,it activates the secretion behavior of wheat seedling roots,thereby improving the nutritional conditions of the rhizosphere and enhancing the stress resistance of plants.At the germination stage,goethite demonstrated a good attenuation effect on the compound toxicity of PS-MPs and arsenic.However,at the seedling stage,as the compound toxicity increased,the attenuation effect of goethite on the compound toxicity of the two was significantly weakened.This research investigates the effects and mechanisms of combined toxicity of PSMPs and arsenic on the early growth stage of wheat,and also explores the role of iron minerals in the combined toxicity of PS-MPs and arsenic.The findings of this study provide valuable insights into the treatment of combined pollution of microplastics and heavy metals in soil.