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EQS approaches for waterbodies impacted by abandoned metal mines under the Water Framework Directive

Lookup NU author(s): Dr Hugh Potter


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Abandoned metal mines are significant and unregulated sources of metal pollution in England and Wales. As part of a programme to manage impacts from abandoned mines under the Water Framework Directive (WFD) this work aimed to clarify the ecological risks when metal concentrations exceed their respective EQS in mining-impacted catchments. Additional project objectives were to provide guidance on 1) the course of action when biological and chemical measurements of status differ, 2) how to implement water quality targets for metals that represent good chemical and ecological status in mining-impacted rivers, and 3) the evidence required to enable refinement of water quality targets in mining-impacted rivers. Field surveys of four mining impacted waterbodies were undertaken across Wales and South West England. These surveys included the collection of chemical, ecological and physicochemical data (for metal bioavailability calculations), including from headwaters. These field data, in combination with existing Environment Agency chemical and biological data, were then analysed to determine the potential of various candidate alternative approaches for applying EQS in mine impacted waterbodies during WFD classification, including the use of Biotic Ligand Models (BLMs), Bioavailability Screening Tools, Ambient Background Concentrations (ABCs) and site-specific quality targets based on the macroinvertebrate community. The conclusions of the project were: Site-specific data can be used to refine the predictions of bioavailability screening tools made using default values, and are likely to result in improved compliance (particularly for the copper EQS). The BLM for copper provides less precautionary estimates of site-specific PNECs than the bioavailability screening tool and could be readily applied to refine EQS compliance where risks remain after application of the bioavailability screening tool. Ambient Background Concentrations (ABC) for zinc can be estimated by sampling in the headwaters of waterbodies, but care must be taken to ensure that these estimates are reliable. Site-specific quality targets for zinc, based on the predicted or observed macroinvertebrate community, can result in improved compliance compared to the use of both conventional and bioavailability-based EQS. However, the methodology for deriving site-specific quality targets requires additional validation.

Publication metadata

Author(s): Simpson P, Peters A, Brown B, Smith R, Merrington G, Greest V, Potter HAB

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: 23rd SETAC (Society for Environmental Toxicology and Chemistry) Europe Annual Meeting: Building a better future: Responsible innovation and environmental protection

Year of Conference: 2013