Adaptive Groundwater Management: Tiered Environmental Health Risk Assessment and Zonation at Complex Contaminated...

Area of Science:

• Environmental Science
• Toxicology
• Risk Assessment

Background:

• Current regulations often assess toxicants individually, neglecting the synergistic risks of complex mixtures in groundwater.
• Realistic coexposure scenarios necessitate a shift towards mixture-oriented risk management strategies.

Purpose of the Study:

• To develop and validate an adaptive framework for assessing and managing environmental and human health risks posed by toxicant mixtures in groundwater.
• To identify priority toxicants and high-risk zones within complex groundwater systems for targeted intervention.

Main Methods:

• Integrated 1,016,590 quarterly concentration records for 277 toxicants from 367 monitoring points.
• Quantified ecological risk using species-sensitivity distribution models (concentration addition → response addition) and human health risks via Monte Carlo simulations.
• Developed an Environmental Health Risk Index (EHRI) by merging ecological and health risk dimensions and applied spatial interpolation for grid-scale risk mapping.

Main Results:

• Identified that a small subset of toxicants (inorganics, metals, BTEXs, haloalkanes, phenols) drives over 95% of the cumulative EHRI.
• Quadrant analysis revealed four distinct coexposure patterns influencing risk.
• Demonstrated that implementing a "source-plume-buffer" treatment train based on the framework reduced high-concern zones (EHRI > 0.60) from 19 km² to <0.1 km² by targeting 45 high-leverage toxicants.

Conclusions:

• The developed framework effectively unifies deterministic and probabilistic risk assessment approaches for complex toxicant mixtures.
• Provides field-scale evidence for coupling mixture-aware risk assessment with risk-zoned management for sustainable groundwater regulation.
• Offers a transferable blueprint for managing multipollutant systems, potentially applicable to surface water and other environmental management zones.