Electroplating parks as hidden sources of novel plastic additives: Occurrence, migration pathways, and ecological...

Novel plastic additives (NPAs), such as antioxidants and vulcanization accelerators, are frequently used in electroplated plastic products and electroplating solutions. However, their occurrence, migration pathways during the wastewater treatment process in electroplating parks and their environmental impact after discharge remain poorly understood. Here, we present the first comprehensive multi-matrix assessment of 35 NPAs, including p-phenylenediamines and their quinone derivatives, benzothiazoles and their derivatives, guanidine derivatives, and others, across wastewater, sludge, surface water, groundwater, and sediments from four electroplating parks in South China. Caprolactam and 1,3-Diphenylurea (DPU) dominated in influent (up to 5575 ng/L) and effluent (up to 1027 ng/L), whereas 6PPD (up to 2969 ng/g) prevailed in sludge. Treatment removal efficiencies ranged from 23.5 % to 95.2 %, with the membrane bioreactor achieving the highest removal (84.6 %), while hydrolysis acidification units promoted the formation of NPAs. The mass loadings of NPAs in sludge exceeded the influent-effluent differentials, suggesting that substantial NPAs were retained in the sludge. Concentrations of total NPAs in surface waters were highest at the On-site locations (up to 4358 ng/L), while groundwater beneath the treatment plants reached levels as high as 6431 ng/L. Multivariate statistical analysis identified electroplating wastewater as a primary source of pollution in the surrounding waters, with hydrophilic compounds migrating via surface-groundwater exchange, while sediments served as the ultimate sink for hydrophobic NPAs. Ecological risk assessment revealed medium-to-high risks, specifically identifying 2,5-bis(o-tolylamino)cyclohexa-2,5-diene-1,4‑dione (DTPD-Q), DPU, and 1,3-Diphenylguanidine (DPG) as high-priority pollutants in the aquatic environment surrounding electroplating parks. Our study illustrates the extensive persistence and mobility of NPAs across both engineered and environmental systems, emphasizing the necessity for upgraded treatment and integrated tracking of their migration from industrial sources.