Ecological Indicators for Abandoned Mines
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Ecological indicators for abandoned mines Report: SC090024/R2 The Environment Agency is the leading public body protecting and improving the environment in England and Wales. It’s our job to make sure that air, land and water are looked after by everyone in today’s society, so that tomorrow’s generations inherit a cleaner, healthier world. Our work includes tackling flooding and pollution incidents, reducing industry’s impacts on the environment, cleaning up rivers, coastal waters and contaminated land, and improving wildlife habitats. This report is the result of research commissioned and funded by the Environment Agency. Published by: Author(s): Environment Agency, Horizon House, Deanery Road, Peter Simpson, Adam Peters, Bruce Brown, Rhiannon Bristol, BS1 5AH Smith, Graham Merrington www.environment-agency.gov.uk Dissemination Status: ISBN: 978-1-84911-294-9 Publically available © Environment Agency – December 2012 Keywords: Biotic Ligand Model, Bioavailability Screening, All rights reserved. This document may be reproduced Abandoned Non-Coal Mines, Ambient Background with prior permission of the Environment Agency. Concentrations The views and statements expressed in this report are Research Contractor: those of the author alone. The views or statements wca environment limited. Brunel House, Volunteer expressed in this publication do not necessarily Way, Faringdon, Oxfordshire, SN7 7YR. T: 01367 represent the views of the Environment Agency and the 246026 Environment Agency cannot accept any responsibility for such views or statements. Cascade Consulting. Enterprise House, Manchester Science Park, Lloyd Street North, Manchester, M15 Further copies of this report are available from our 6SW. T:0161 227 0282 publications catalogue: http://publications.environment- agency.gov.uk or our National Customer Contact Environment Agency’s Project Managers: Centre: T: 08708 506506 Vicky Greest (Evidence Directorate) and Hugh Potter E: [email protected]. (Operations Directorate) Collaborator(s): Department for Environment, Food and Rural Affairs (Defra) Project Number: SC090024/2 Product Code: LIT 7657 ii Ecological indicators for abandoned mines Evidence at the Environment Agency Evidence underpins the work of the Environment Agency. It provides an up-to-date understanding of the world about us, helps us to develop tools and techniques to monitor and manage our environment as efficiently and effectively as possible. It also helps us to understand how the environment is changing and to identify what the future pressures may be. The work of the Environment Agency’s Evidence Directorate is a key ingredient in the partnership between research, guidance and operations that enables the Environment Agency to protect and restore our environment. This report was produced by the Scientific and Evidence Services team within Evidence. The team focuses on four main areas of activity: • Setting the agenda, by providing the evidence for decisions; • Maintaining scientific credibility, by ensuring that our programmes and projects are fit for purpose and executed according to international standards; • Carrying out research, either by contracting it out to research organisations and consultancies or by doing it ourselves; • Delivering information, advice, tools and techniques, by making appropriate products available. Miranda Kavanagh Director of Evidence Ecological indicators for abandoned mines iii Executive summary Abandoned metal mines are significant and unregulated sources of pollution to our rivers and seas discharging priority hazardous and other polluting substances, notably cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn) and iron (Fe). The first Water Framework Directive (WFD) surface water classification in England and Wales identified 133 waterbodies failing to meet environmental quality standards (EQS) for metals (Cd, Pb, Ni, Zn, Cu) in metal mining areas. The majority of significant EQS failures for Pb and Cd across England and Wales (that is, EQS failures occurring with more than 95 per cent statistical certainty) are in rivers draining abandoned metal mines. Four hundred and seventy waterbodies have been identified as “impacted” or “probably impacted” by abandoned non-coal mines across England and Wales. The Environment Agency has developed a joint approach with the Department for Environment, Food and Rural Affairs (Defra) to manage pollution from abandoned non- coal mines for the WFD. Three priority areas have been identified in the first river basin management planning cycle (2009-2015): 1. Develop new low-cost sustainable treatment technologies for metal mines (mitigation of pollution from abandoned mines). 2. Understand how to implement water quality targets to protect ecosystems impacted by abandoned mines over many decades (ecological indicators)., and 3. Carry out catchment investigations in priority water bodies to identify the main sources of metals, appraise options to manage the pollution including costs and benefits, and implement remediation (clean-up). This project focussed on the second work area – ecological indicators for abandoned mines. The project was funded by Defra and managed by the Environment Agency as part of the overarching project, Managing mining pollution for the Water Framework Directive (MAGIC) (SC090024). The project outlined in this report aimed to clarify whether conventional EQS are suitably protective of aquatic life (such as invertebrates, fish, diatoms, macrophytes), or if higher metal concentrations than the EQS can be acceptable in mining-impacted catchments without risk to aquatic life and, if so, how this is accommodated within the WFD to enable the status of the water body to be correctly classified. The overall project aim was to investigate the ecological impact of metals in rivers and produce guidance on setting water quality targets for aquatic ecosystems that are impacted by long-term mining pollution. Additional objectives were to provide guidance on: 1. The course of action when biological and chemical measurements differ, that is, when EQS for metals are breached but the biological community is in a good condition. 2. How to implement water quality targets for metals that represent good chemical and ecological status in mining-impacted rivers. 3. The evidence required to enable the appropriate refinement of water quality targets in mining-impacted rivers. For example, whether site biological data are required. To achieve these objectives a combination of desk and field-based work was undertaken. The “tiered risk-based framework” for incorporating biotic ligand models (metal bioavailability models) and ambient background concentrations (ABCs) for iv Ecological indicators for abandoned mines metals risk assessment under the WFD was used as the basis for the project. The initial phase of the project (described in section 2 of this report) was focussed on the identification of sub-sets of waterbodies that share similar WFD compliance characteristics. For example, scenario 3, has poor chemical status but good1 ecological status. This “screening assessment” applied both simple bioavailability screening tools and default Ambient Background Concentrations for zinc and was used to identify candidate waterbodies that offered the greatest scope for developing robust guidance for the implementation of alternative approaches to assess the status of mining impacted waters after undertaking a field programme to provide a range of water physico-chemistry, metal mixtures and EQS compliance scenarios. A prioritised list of waterbodies was agreed with the Environment Agency project board and field surveys to obtain additional site-specific chemical and ecological data were undertaken, which included the collection of waterbody specific background concentrations for zinc and the suite of physico-chemical input parameters required to run full biotic ligand models for Cu and Zn. These field data, in combination with existing Environment Agency data for these waterbodies, were then analysed to determine the relative efficacy, transparency and legitimacy of candidate alternative approaches for applying EQS in mine impacted waterbodies during WFD classification in order to minimise instances of chemical and biological mis-match. A pre-screening exercise removed waterbodies where there are pressures other than metals or acidity. This decreased the number of waterbodies taken forward to the screening assessment from 470 to 240. The screening assessment resulted in a modest improvement in the overall surface water classification of the 240 mining impacted waterbodies considered in this report. The number of waterbodies at “good or better” surface water status (based on a combination of chemistry and ecology) increased slightly from 47 to 53. More significantly, the number of waterbodies reaching good chemical status was increased from 105 to 116. However, potentially of most interest in this dataset is the reduction in the number of waterbodies at which “significant” metal EQS failures are reported. Significant EQS failures are those that occur at a confidence of at least 95 per cent and are most likely to require a regulatory intervention. Overall, significant failures occur at 130 (54 per cent) waterbodies with conventional EQS, which is reduced to 87 (36 per cent) of waterbodies after applying the bioavailability screening tools. Based on the findings of the screening assessment, a limited “confirmatory” field programme was undertaken to further explore some of the compliance scenarios.