Humic acid alleviates the toxicity of polystyrene nanoplastics in combination with their copper nanoparticle co-pollutants in Artemia salina

Polystyrene nanoplastics (PSNPs) have become a ubiquitous environmental threat that can harm living organisms. Other pollutants such as copper nanoparticles (CuNPs) bind with PSNPs and humic acid (HA), alleviating the toxicity of PSNPs. In this study, individual PSNPs were interacted with CuNPs and HA to study their combined toxicity on Artemia salina. The size of PSNPs increased after 72 h of interaction with CuNPs. FTIR spectroscopy analysis confirmed that CuNPs bind to the surface of PSNPs. It was found that HA adsorbed more strongly onto PSNPs than CuNPs. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray (EDX) spectroscopy confirmed the adsorption of HA and CuNPs onto the surface of PSNPs. Toxicity experiments showed a decreased toxicity of PSNPs and CuNPs upon their combination with HA (humic acid). Microscopic analysis showed particle accumulation in Artemia salina. The mortality rate of Artemia salina is higher in PSNP + CuNP combination. PSNPs + CuNPs showed higher production of antioxidant enzymes, and PSNPs + CuNPs + HA showed lower toxicity. This study shows that the presence of HA can lead to a reduction in the toxicity of PSNPs and CuNPs, suggesting their potential application in environmental remediation.