Screening and prioritizing substances in groundwater in the Beijing-Tianjin-Hebei region of the North China Plain based on exposure and hazard assessments.

Screening and prioritizing hazardous substances in groundwater is crucial to monitor and control groundwater quality. Total of 283 substances were determined in 213 groundwater samples from the Beijing-Tianjin-Hebei region during 2019-2020. 184 substances were screened as candidates. 22 prioritizing indicators were evaluated and scored for the candidates to reflect their occurrence, mobility, persistence, bioaccumulation, acute and chronic ecotoxicities with different trophic levels, and long-term human health effects. Multi-attribute decision-making technologies were applied to prioritize these candidates, including analytic hierarchy process (AHP), TOPSIS and VIKOR. Greater weightings in AHP were assigned to attributes of occurrence and acute toxicity by experts' judgment. Hierarchical cluster analysis and principal component analysis were used to transform initial matrix with the 22 indicators into an orthogonalized matrix with 6 principal components, which represented general toxicity to aquatic organism and mammal, bioaccumulation, carcinogenicity & mutagenicity, persistence, and teratogenicity & endocrine, respectively. VIKOR and TOPSIS results were similar, but different from the AHP ranking. Two filter criteria harmonized their difference. Twenty-three substances were proposed as the priority substance with high hazard and potential exposure, and nitrate-nitrogen and ammonia-nitrogen were selected as additional priority substance frequently and extensively exceeding official groundwater quality standard on the regional scale.