Effects Of Polyethylene Microplastics On The Bioaccumulation And Toxicity Of Cadmium

Microplastics,as a new environmental pollutant,has drawn an increasing worldwide attention due to its widespread existence and its resulting severe ecological and environmental problems.Especially,up to date researchers have paid more and more attention to the microplastic pollution in agricultural ecosystems.During the production processes of microplastics,some other additives are added,resulting in a relatively stronger adsorption ability under natural conditions.In this case,microplastics could adsorb other pollutant in environment,and caused serious environmental pollution.Because microplastics are difficult to degrade,the pollutants carried by them could be transmitted along the food chain,ultimately threatening ecosystem stability and human health.Meanwhile,there are different degrees of heavy metal pollution in soil environment.The microplastics in soil can absorb and enrich heavy metals,and lead to the aggravation of soil pollution through migration and diffusion.The microplastics and heavy metals in soil could interact and pose potential threats to the ecological environment.Therefore,exploring the interaction between microplastics and heavy metals in the soil environment and the influence of microplastics on heavy metal enrichment in plants and its potential mechanism have important theoretical guiding significance for assessing the ecological risk of microplastics pollution in soil and preventing and controlling heavy metal pollution in farmland soil.To explore the influences of microplastic,heavy metal and their interaction on seed germination and seedling growth of crops,this paper taken wheat and rice as targeted crops and select polyethylene plastic and heavy metal cadmium as the research objects,to discuss their alone and coupling influences on seed germination and seedling growth under the condition of soil culture and hydroponic experiment,respectively.In this study,the effects of microplastic and cadmium on wheat and rice seed germination,belowground-aboveground biomass,chlorophyll content,root enzyme activity,the absorption and enrichment of cadmium in plants,the pH and available cadmium concentration in soil and water environments were analyzed,with the propose of revealing the effects of polyethylene plastic on cadmium bioaccumulation in plants and their mechanism.Specific results were as follows:Under the single treatment,the effect of cadmium stress on the germination characteristics of seeds was basically manifested to be "low promotion and high inhibition".The germination rate,germination potential,germination index,vigor index,root length and bud length all showed a downward trend with the increase of cadmium concentration.The single microplastic treatment showed a similar trend,i.e.,the low concentration(5 mg L-1)promoted seed germination,medium concentration(10 mg L-1)had no significant effect on germination,while high concentration(50 mg L-1)inhibited germination.The results of the combined pollution of microplastics and cadmium showed that compared with the control,except that the combined treatment of microplastics(100 mg L-1)and cadmium(5 mg L-1)had synergistic promoting effect,all other combinations had antagonistic effects on seed germination and seedling growth.Under the 100 mg L-1 concentration of microplastic,its combination with low concentration of cadmium(5 mg L-1)had a synergistic effect on the bud and root growth of seeds,while its combination with high concentration of cadmium(10 mg L-1,50 mg L-1)had an antagonistic effect on root growth.Our study indicated that compared with single pollution,the combination of microplastics and cadmium showed antagonistic effects on seed germination and seedling growth,and reduced the toxic effect of a single pollutant to a certain extent,and polyethylene microplastics could reduce the adsorption capacity of plants to cadmium.This paper could be helpful to understand the influence of microplastics and heavy metals accumulation in plants and their mechanisms and assess the subsequent ecological security risks,and highlight the important of future studies on relevant mechanisms.The pollution of microplastics and heavy metals in agro-ecosystem environment must be paid attention to and prevention and control measures should be taken as soon as possible.