Combined Effects of Fronts, Upwelling and the Biological Pump on Organophosphate Esters in the Changjiang (Yangtze) River Estuary During Summer

Abstract

AbstractEstuarine and coastal environments are important transport pathways and regional sinks for anthropogenic pollutants. In this study, the occurrence and transport of the continuously released organophosphate esters (OPEs) was investigated together with physical and biochemical parameters throughout the water column in the Changjiang (Yangtze) River estuary during the summer. Total dissolved and particulate OPEs showed great spatial heterogeneity, with mean concentrations of 550 ± 280 ng/L in the estuary, 110 ± 270 ng/L in the front/upwelling zone, and 410 ± 450 ng/L in the continental shelf. OPE concentrations in the estuarine bottom waters were high due to massive terrestrial/sediment inputs. In contrast, the “surface enrichment and depth depletion” of OPEs in the continental shelf was closely related to seasonal stratification. Reduced OPE concentrations were observed in the frontal/upwelling zone due to isopycnal heaving. Frontal activity and upwelling induced phytoplankton blooms in the coastal regions, which jointly contributed to elevated OPEs beneath surface water with high phytoplankton aggregation. The OPEs mainly originated from wastewater treatment plant discharges, industrial pollution and consumer products. These OPEs generally posed a low ecological risk to aquatic lives, but their long‐term effects cannot be ignored due to their continuous high production, usage and release.