Comprehensive Investigation And Risk Assessment Of Contaminants Of Emerging Concerns In Yellow River Estuary

Since the 20 th century,a large number of chemicals have entered water environments while improving human living standards,resulting in increasingly prominent ecological and human health issues.Water environment and aquatic ecosystem protection have gone through a gradual process from conventional water pollutants such as chemical oxygen demand and nitrogen and phosphorus pollutants,to the reduction of trace persistent organic pollutants(POPs),the determination of classic POPs with significant ecological effects,the tracking of congeners,and the contaminants of emerging concerns(CECs).CECs are compounds that are currently being produced and used in large quantities,with high environmental levels and insufficient ecological and health risk data to meet risk management standards,and they also exhibit one or more characteristics of POPs.The environmental pollution,ecological risks,and human health issues caused by CECs in China are unique.The "Catalog of Existing Chemical Substances in China" published by the Ministry of Ecology and Environment in 2013 has included more than 45,000 chemical substances,but not all chemicals and their metabolites are included.The estuary area is located in the middle of the open sea and land,with frequent and complex human activities,making it a fragile ecological area.The estuary and nearshore waters may be polluted by various sources,such as wastewater discharge,industrial emissions,stormwater runoff,aquaculture,and agricultural non-point source pollution.The typical area at the mouth of the Yellow River basin is one of China’s important chemical production bases,with active agricultural activities,unclear numbers of emerging contaminants,and potential ecological risks.Therefore,establishing a comprehensive screening strategy for CECs in estuarine water environments based on high-resolution mass spectrometry can quickly understand the distribution characteristics and patterns of emerging pollutants in the estuary area and identify their sources.Developing a risk ranking strategy for emerging contaminants based on the toxicity priority index(Tox Pi)is of great significance for actively preventing emerging pollutant pollution and risks.Currently,the conventional method for detecting CECs is target analysis,focusing on preselected compounds,particularly those associated with wastewater discharges.CECs from other sources or previously monitored associated with adverse water ecological risks are usually ignored.Therefore,a screening strategy and data processing workflow for CECs in surface water based on suspected/nontargeted analysis were developed in this study.This screening strategy combines high-resolution mass spectrometry and emerging statistical methods to identify and characterize potential CECs in surface water without all CECs standards.A total of 593 CECs were identified in the YRE by this screening strategy,including 153 pesticides,307 industrial chemicals,and 201 pharmaceuticals and personal care products(PPCPs).Noticeably,two CECs were identified for the first time in surface water in a specific area of the YRE: erucamide and 2-Phenylquinoline.Target analysis of pollutants of great concern in typical areas of the YRE showed that 112 CECs were detected at least at one sampling site and a total concentration range of 7.07 to10210.33 ng/L.The highest concentrations of CECs were found in the industrial chemicals category(126.58 to 10210.33 ng/L),followed by agricultural(45.11 to 4611.26 ng/L)and antibiotics(7.07 to 1025.07 ng/L).The degree of contamination of CECs was more significant in the central and southeastern areas of the study area with intensive living and production.It showed a significant correlation between land use type and the intensity of human activities.The principal component analysis(PCA)and positive matrix factorization(PMF)models were used to analyze the sources of CECs,which were found to be mainly "agricultural activity sources" and "domestic and industrial sources" in the water environment.The risk quotient(RQ),which is a ratio of measured environmental concentration(MC,ng/L)to the minimum predicted no-effect concentration(PNEC,ng/L),was used to quantify further the ecological risk in a specific area of the YRE.The range of the maximum risk quotients for 94 CECs was 0.00 to 157.01.Among them,6 CECs possessed high risk(11.59~157.01),8 CECs possessed moderate ecological risk(1.43~8.30),12 CECs possessed low ecological risk(0.10~0.76),and the rest 69 CECs possessed potential ecological risk with long-term attention to their changes.Under the Toxicological Priority Index(Tox Pi)framework,indicators such as toxicity data,environmental concentrations and detection rates of CECs are integrated to calculate Tox Pi scores for 94 CECs.As a result,the Tox Pi scores are used to rank the CECs and to create a list of priority compounds.The optimized list of priority control compounds suggests substances more toxic to aquatic organisms,such as PAHs,and substances detected more frequently,such as organophosphates,whose ecological risks also require attention.