The types of microplastics, heavy metals, and adsorption environments control the microplastic adsorption capacity of heavy metals

Anthropogenic development has released large amounts of microplastics (MPs), which are carriers of migratory heavy metals, into the environment, and heavy metal adsorption by MPs may have strong combined toxic effects on ecosystems. However, until now, a comprehensive understanding of the factors influencing these adsorption capacities of MPs has been lacking. Thus, we used 4984 experimental data points to systematically assess the factors influencing the adsorption strength of 8 types of MPs on 13 types of heavy metals. We found that (1) the types of MPs, heavy metals, and adsorption environments significantly impacted the heavy metal adsorption capacities of MPs; (2) polyvinyl alcohol (PVA) showed a higher adsorption capacity for lead (Pb) and cadmium (Cd) than did other MPs, by 2810.62 mg/kg and 2732.84 mg/kg, respectively; (3) the adsorption capacities of MPs for heavy metal were regulated by multiple variables, with heavy metal concentration, MP quality, solution amount, adsorption time, and pH being the most important; and (4) MPs had a higher adsorption capacity in aquatic environments (except for seawater) than which in soil environments. Overall, our study clearly showed that the types of heavy metals, adsorption environments, and MPs influenced the heavy metal adsorption capacities of MPs and may exacerbate their combined environmental toxicity, which would help better characterize the severity of MP pollution.

Automated summary

Anthropogenic development has led to the release of microplastics (MPs) and their associated heavy metals into the environment, potentially causing toxic effects on ecosystems. This study evaluated the factors influencing the adsorption capacities of 8 types of MPs on 13 types of heavy metals using a large dataset. The results showed that the types of MPs, heavy metals, and adsorption environments significantly influenced the adsorption capacities, with polyvinyl alcohol (PVA) exhibiting high adsorption capacities for lead (Pb) and cadmium (Cd). Multiple variables such as heavy metal concentration, MP quality, solution amount, adsorption time, and pH regulated the adsorption capacities of MPs for heavy metals.