Acid Mine Drainage
Predicting and remediating the impacts of mining activities on freshwater ecosystems
Coal and gold mining in New Zealand is an important part of the economy, valued at $1.5B p.a. and based on current forecasts could grow to $3.0B p.a. by 2015. However, mining frequently has significant impacts on freshwater ecosystems. For example, many active and abandoned coal mines on the West Coast of the South Island, especially those associated with the sulphur and heavy metal rich Brunner coal measures, generate a cocktail of acid mine waters with low pH and elevated concentrations of dissolved iron, aluminium and other metals. This acid mine drainage (AMD) enters streams and rivers resulting in unnaturally low pH (e.g. < 3) potentially toxic levels of assorted heavy metals, and the formation metal oxide precipitates (Fig. 1). Gold mining can also impact freshwaters: mining of hard rock gold deposits can release of toxic metals such as arsenic and antimony, and alluvial gold mining often increases suspended sediment loads and sometimes produces elevated levels of mercury and other metals.
Figure 1. A stream near Reefton with
low pH
(approximately 3.5) and iron
hydroxide precipitate.
Our challenge is to investigate methodologies to predict, manage remediate these impacts on stream ecosystems and to enhance ecological recovery.
Researchers within the Freshwater Ecology Research Group (FERG) are part of a multidisciplinary team (University of Canterbury, Landcare Research, CRL Energy Limited and University of Otago) working on a framework to minimise and mitigate the impacts of mining on stream ecosystems. The research program “Delivering pathways to mineral wealth and environmental sustainability” is funded by the Foundation of Research, Science and Technology (FRST) and consists of four key objectives:
- Predictive geochemistry of mine drainage
- Effects of mine drainage on stream ecosystems
- Management and remediation of mine drainage
- Integrating this information to provide a management framework for the mining industry and water managers.
Work within the FERG group largely focuses the second objective, which aims to significantly improve the understanding of how freshwater systems respond to mine drainage. Our research has concentrated on the impacts of acid mine drainage arising from coal mines, and includes several components:
- Quantifying the impact of AMD on the structure of stream communities and food webs.
- Impact of mining activities on stream ecosystem functions
- Toxicity of AMD to benthic invertebrates and fish (in collaboration with Landcare Research).
- Limitations to the recolonisation of remediated streams (link to Justin's page)
People involved in this project
University of Canterbury
Jon Harding
Kristy Hogsden (PhD student)
Justin Kitto (Completed MSc Student)
Jonathan Bray (Completed MSc Student)
Annabel Barnden (Completed MSc Student)
Missouri University of Science & Technology
Dev Niyogi
Landcare Research
Jo Cavanagh
Olivier Champeau
Tom Sheehan
Rowan Buxton
CRL Energy Limited
James Pope
Dave Trumm
University of Otago
Dave Craw
Publications
Barnden 2005. Ecology of streams affected by iron precipitates and iron flocculants. MSc thesis, University of Canterbury (pdf, 1.6mb).
Barnden & Harding 2005. Shredders and leaf breakdown in streams polluted by coal mining in the South Island, New Zealand. New Zealand Natural Sciences 30: 35-48 (pdf, 580kb).
Bray 2007. The ecology of algal assemblages across a gradient of acid mine drainage stress on the West Coast, South Island, New Zealand. MSc thesis, University of Canterbury (pdf, 1mb).
Bray, Broady, Niyogi & Harding 2008. Periphyton communities in New Zealand streams impacted by acid mine drainage. Marine and Freshwater Research 59: 1084-1091 (pdf, 350kb).
Harding, McIntosh, Gray, Jellyman & Eikaas 2006. Distribution of native fish in the Ngakawau and Waimangaroa Rivers. University of Canterbury report for Solid Energy (pdf, 4.5mb).
O’Halloran, Cavanagh & Harding 2008. Response of a New Zealand mayfly (Deleatidium spp.) to acid mine drainage: implications for mine remediation. Environmental Toxicology and Chemistry 27: 1135-1140 (pdf, 550kb).
Newsletters
Harding, Bray & Niyogi 2008. Do algae grow in acid mine waters? Newsletter of the Freshwater Ecology Research Group, University of Canterbury (pdf, 320kb).
Harding & Champeau 2008. Can benthic invertebrates be used to predict impacts in streams with acid mine inputs? Newsletter of the Freshwater Ecology Research Group, University of Canterbury (pdf, 300kb).