Combined Toxicity of Nano-Plastics and Cd 2+ On Chlorella and Mechanisms Behind

Polystyrene nano-plastics (PSNPs) and Cd2+ are two main pollutants in the water environment, which might lead to combined effects on aquatic organisms. In this study, the combined effects of PSNPs and Cd2+ on Chlorella were investigated. Results showed that smaller PSNPS performed higher inhibition on Chlorella. The inhibition ratio of PSNPs-50-, PSNPs-50+ at 10 mg/L were 5.01%-21.11% higher than those of PSNPs-250- and PSNPs-250+. The Chlorophyll a (Chl) concentrations of PSNPs-50- and PSNPs-50+ were 32.90% and 72.44% lower compared to control on day 2, respectively. Higher malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) activities were also observed in PSNPs-50- and PSNPs-50+, indicating that 50 nm PSNPs might inhibit the synthesis of Chl and induce the oxidative stress effect in Chlorella. Besides, a synergistic toxic effect on Chlorella was observed between Cd2+ and PSNPs-50 nm. PSNPs-50- could damage the membrane of Chlorella and promote the transfer of Cd2+ into Chlorella and improve the toxicity of Cd2+. This study could provide deeper understandings on the combined toxicities of nano-plastics and other contaminants.