Effects of microplastics and cadmium on the soil-wheat system as single and combined contaminants.

Two types of microplastics (MPs) (micro polyethylene (mPE) and micro polypropylene (mPP)) were studied alongside and cadmium (Cd) to determine how they affected soil-wheat systems, both individually and in mixed combinations. This was accomplished by carrying out a pot experiment to reveal their respective interaction effects. Results showed that in different Cd pollution levels soils (0, 1, and 5 mg kg-1), chlorophyll concentrations in wheat leaves decreased markedly with rising levels of mPE/mPP. In the single mPE treatment, as the mPE content in the soil increased, the aboveground and root biomass improved. By contrast, in the single mPP treatment, when the mPP content was low, the aboveground biomass of wheat increased and with the mPP content increased, the aboveground biomass of wheat decreased. This result was also shown in the combined contamination of mPE/mPP and Cd (1 mg kg-1) in the root biomass. With an increase in Cd concentration (that is, at 5 mg kg-1) in the combined contamination, this phenomenon continued in the aboveground biomass while in the roots, there was a promotion effect. At Cd contaminated soil (1 mg kg-1), MPs inhibited Cd enrichment in aboveground wheat, but at 5 mg kg-1, Cd enrichment was promoted instead, in both aboveground and roots. Adding mPE/mPP diminished pH and the Cd effective state concentration in soil. The combined contamination of mPE/mPP and Cd affected the Cd biological enrichment in the wheat to some extent, which was influenced by the types of MP and pollution levels of Cd in the soil.

Effect of Microplastics on the Adsorption and Desorption Properties of Cadmium in Soil.

This study analyzed the role of micro polyethylene (mPE) and micro polypropylene (mPP) on cadmium (Cd) adsorption and desorption in soil. Cd adsorption in soils reached equilibrium within 240 min with or without mPP/mPE. The largest Cd adsorption amount was 923.88 mg kg-1 in the control treatment (no MPs). The Cd adsorption amount in the mPP treatment was 872.21 mg kg-1, greater than that in the mPE treatment (780.21 mg kg-1). MPs reduced the soil adsorption of Cd to some extent. Soils supplemented with mPE were more inhibitory to Cd adsorption than mPP. The pseudo-second-order model equation proved to be the most optimal equation for describing Cd adsorption dynamics in the presence of different MPs, while the Freundlich equation was best for describing isothermal adsorption of Cd in the presence of MPs. MPs facilitate the desorption of metals from the soil.