Seasonal fluctuations in heavy metal bioaccumulation and health risk in wild fish from a highly urbanized estuary: a case study in Guangzhou, China

Wild fish in highly urbanized estuaries are commonly exposed to heavy metal contamination, and seasonal fluctuations in metal bioaccumulation can significantly influence associated health risks. To characterize seasonal variations in health risks, this study investigated seasonal fluctuations of heavy metal bioaccumulation in dominant wild fish from Guangzhou, a typical highly urbanized estuary city in southern China. Significant seasonal variations were observed, with metal concentrations being notably higher in summer than in winter. A considerable proportion of samples exceeded limits for As, Cr, and Pb; but Cr mostly decreased below the limits in winter. Clustering analysis suggested species-specific accumulation patterns were stable across seasons, with Oreochromis mossambicus and Ophiocephalus argus Cantor exhibiting broad-spectrum high accumulation. Pi values of As, Cr, and Pb were mostly within 0.2–0.6, suggested their prevalent mild contamination. TTHQ values were overall higher in summer, TTHQ exceeded 1 mainly occurred in summer, particularly for children, with As being the dominant health risk contributor. TTHQ > 1 primarily centralized in hyperaccumulators for adults, while those of some low-accumulators fell below 1 for children in winter. Based on safe consumption rate calculations, As imposed the strictest limits, with recommended weekly intakes of 0.20 kg (adults) and 0.10 kg (children) in summer, those significantly improved to 0.36 kg and 0.18 kg in winter suggested the higher security for wild fish consuming in winter. Given the huge difference of health risk and recommended consumption rate between different seasons, the seasonal impacts should be incorporated into the guidance for fish consuming.