Nontargeted Screening of Contaminants of Emerging Concern in the Nandu River Estuary

Abstract

Contaminants of emerging concern (CECs) in estuarine areas have garnered increasing attention due to their potential environmental impacts. Despite this focus, detailed analyses of the sources, transport mechanisms, and environmental consequences of these pollutants remain limited. This study pioneered the use of non-target screening technology for a comprehensive assessment of CECs in the Nandu River estuary. A total of 18,000 characteristic features were screened, revealing a greater number of hydrophobic features in seawater compared to the estuarine area. We identified 74 Level 1 compounds, 195 Level 2 compounds and 48 Level 3 compounds, with the main categories being pharmaceuticals (34%), industrial materials (23%), pesticides (18%) and natural products (17%). The most frequently detected pollutants were Cotinine, Atrazine, Carbendazim, and 2,7,8,9-Tricyclazole. Semi-quantitative analysis using external standards was performed on 61 pollutants, showing higher concentrations in the estuarine area than in offshore waters, with Climbazole exhibiting the highest concentration. Based on ecological risk assessment, 12 CECs (with RQ > 1) were identified as requiring enhanced monitoring. Climbazole and Imidacloprid had risk quotient (RQ) values exceeding 10, categorizing them as high-risk compounds. A priority list was established based on the frequency of detection, bioaccumulation potential, persistence, toxicity and endocrine disruption potential of the compounds. 64 CECs were identified as high priority, consisting mainly of pesticides and pharmaceutical compounds. Pesticides predominantly originate from upstream agricultural activities, decreasing in concentration downstream, whereas pharmaceuticals, industrial materials, and natural products are linked to domestic sewage. Tidal cycles play a crucial role in modulating the distribution and concentration of CECs within estuarine waters. This modulation is attributed to the dynamic interaction between terrestrial inputs and coastal influences, where high tides significantly contribute to the dilution of land-derived pollutants.

Keywords: Nontarget screening, Nandu river, Contaminants of emerging concern, Environmental monitoring, Tidal