Effects of Co-Contamination of Microplastics and Cd on Plant Growth and Cd Accumulation

Abstract

Microplastics (MPs) occur widely in terrestrial ecosystems. However, information on the interaction of MPs with metals in terrestrial ecosystems is lacking in the literature. The present study investigated the effects of two types of MPs (high-density polyethylene (HDPE) and polystyrene (PS)) with different dosages (i.e., 0, 0.1%, 1%, and 10%) on the uptake and effects of Cd in maize plants grown in an agricultural soil. Results showed that addition of Cd at a 5 mg/kg caused inhibited plant growth and resulted in high Cd accumulation in plant tissues. Polyethylene alone showed no significant phytotoxic effects, but a high-dose of HDPE (10%) amplified Cd phytotoxicity. Polystyrene negatively affected maize growth and phytoxicity further increased in the presence of Cd. Both HDPE and PS caused soil diethylenetriaminepentaacetic acid (DTPA)-extractable Cd concentrations to increase but did not significantly affect Cd uptake into plant tissues. In the soil without Cd addition, HDPE decreased soil pH, while PS did not significantly alter soil pH. However, in the soil spiked with Cd, both HDPE and PS increased pH. Overall, impacts on plant growth and Cd accumulation varied with MP type and dose, and PS induced substantial phytotoxicity. In conclusion, co-occurring MPs can change Cd bioavailability, plant performance, and soil traits. Our findings highlight the ecological impacts that could occur from the release of MPs into soil.

Microplastics interaction with terrestrial plants and their impacts on agriculture

“…This alteration in metabolic system caused a decline in harvest yield. Similarly, in maize (Zea mays L.) plants exposed simultaneously to MPs and Cd, the growth of plants was affected, which resulted in reduction of plant dry weights (Wang et al, 2020). Boots et al (2020) also noticed that MPs negatively influence the growth both aboveground and belowground productivity at different doses in L. perenne.…”

“…This alteration in metabolic system caused a decline in harvest yield. Similarly, in maize ( Zea mays L.) plants exposed simultaneously to MPs and Cd, the growth of plants was affected, which resulted in reduction of plant dry weights (Wang et al., 2020). Boots et al.…”

Microplastics as an Emerging Environmental Pollutant in Agricultural Soils: Effects on Ecosystems and Human Health

“…The co-exposure of MPs and OPFRs induced greater neurotoxicity and oxidative stress in mice compared with a single OPFR exposure, and it also enhanced the disruption of amino acid metabolism and energy metabolism in mice (Deng et al, 2018). The combined exposure of MPs and heavy metals may lead to stronger phytotoxicity, including reducing plant biomass, affecting photosynthesis, inhibiting root activities, and causing oxidative damage (Wang et al, 2020b;Dong et al, 2020;Dong et al, 2021a).…”

Uptake and Accumulation of Nano/Microplastics in Plants: A Critical Review

“…Furthermore, iron-manganese oxide-bound fractions of nickel (Ni), copper (Cu), chromium (Cr), and exchangeable carbonated-bound fractions in soil can be reduced by the presence of MPs [114]. The presence of high-density polyethylene (HDPE), polystyrene (PS), polyethylene (PE), and polylactic acid (PLA) increases the diethylenetriamine pentaacetate (DTPA) extractable Cd concentration of soil [116][117][118]. The presence of plastic in soil alters the bioavailability of other metals; arsenic bioavailability was limited in the presence of MPs [119].…”

“…Earthworms increase the bioavailability of Cd in MP-enriched soils [96]. Wang et al [117] reported the higher bioavailability of Cd in the presence of PLA in soil-plant systems as compared to PE.…”