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Mine Water and the Environment

, Volume 34, Issue 4, pp 464–477 | Cite as

Mitigation of Acid Mine Drainage via a Revegetation Programme in a Closed Coal Mine in Southern New Zealand

  • C. G. Rufaut
  • D. CrawEmail author
  • Andrea Foley
Technical Article

Abstract

Acid mine waters (pH 3–5) at the closed Wangaloa coal mine have resulted from surface runoff and groundwater seepage in contact with pyrite-bearing waste rock piles. The low nutrient content, physical factors, and elevated boron levels, all combined with the low pH (down to pH 2) of most waste rocks have limited early planned revegetation and natural plant colonisation. A renewed programme of site rehabilitation, started in 2000, focussed on establishment of near-complete ground cover and functioning ecosystems. Small patches (tens of m2) of low-pH, boron-rich, unvegetated substrates persist after more than 10 years of rehabilitation and introduction of a wide variety of species, but natural colonisation is slowly advancing on these remnants. The rehabilitation has coincided with and contributed to a rise in runoff water pH from ≈4.5 to ≈5.6. This decrease in severity of acid mine drainage (AMD) has apparently become sustainable without further intervention. Near-complete vegetative cover occurred by a combination of a major planting programme and natural colonisation from nearby islands of established native species. Both processes were accompanied by development of functioning ecosystems, and supported by increasing invertebrate diversity and abundance, which are ensuring the persistence of the ameliorative effects on AMD at the site. Vegetation established via natural processes can function ecologically at a higher level than comparable planted vegetation but may not lead to the desired plant cover on some substrates.

Keywords

pH Boron Quartz Waste rock Plants Invertebrates Colonisation 

Verminderung von saurem Grubenwasser durch eine Aufforstung in einem geschlossenen Kohlenbergwerk in Süd-Neuseeland

Zusammenfassung

Aufgrund des Kontakts von Oberflächen- und Grundwasser mit pyrithaltigen Bergen kommt es an der geschossenen Kohlenzeche Wangaloa (Süd-Neuseeland) zum Austritt von sauren Grubenwässern (pH 3–5). Der geringe Nährstoffgehalt der meisten Berge, deren physikalische Eigenschaften und erhöhten Borgehalte in Verbindung mit dem niedrigen pH-Wert (bis zu pH 2) behinderten frühere Begrünungsversuche und die natürliche Sukzession. Ein neuerliches Programm zur Rehabilitation begann im Jahr 2000 und zielte darauf ab, eine fast vollständige Vegetationsdecke zu erhalten und ein funktionierendes Ökosystem zu errichten. Selbst nach über 10 Jahren Renaturierung mit einer Vielzahl von Arten bestehen noch kleinere Bereiche von mehreren Zehnern Quadratmetern mit niedrigem pH-Wert und borreichen, unbewachsenen Substraten in denen allerdings langsam Sukzession einsetzt. Im Zuge der Rehabilitation stieg der pH-Wert des Oberflächenwassers von etwa 4.5 auf etwa 5.6 an. Offensichtlich hat sich diese nachhaltige Verbesserung des sauren Grubenwassers ohne weiteres Zutun ergeben. Eine nahezu vollständige Vegetationsdecke hat sich durch die Kombination eines großangelegten Bepflanzungsprogramms und natürliche Besiedlung von nahe gelegenen Inseln mit etablierten einheimischen Arten gebildet. Beide Prozesse gehen mit der Ausbildung eines funktionierenden Ökosystems einher und gleichzeitig hat die Vielfalt und Anzahl der Wirbellosen zugenommen. Dadurch ist gewährleistet, dass die Bemühungen zur Sanierung des Zechengeländes langlebig sein werden. Obwohl natürliche Sukzession zu einer ökologisch besser funktionierenden Vegetation führen kann als Anpflanzungen werden machen Substrate nicht zu der gewünschten Pflanzenbedeckung führen.

Atenuación del drenaje ácido de mina a través de un programa de revegetación en una mina de carbón cerrada en el sur de Nueva Zelanda

Resumen

Las aguas ácidas de mina (pH 3-5) en la mina de carbón Wangaloa, actualmente cerrada, han resultado del escurrimiento de agua superficial y la filtración de aguas subterráneas en contacto con pilas de residuos de roca con contenido en pirita. El bajo contenido en nutrientes, factores físicos y los elevados niveles de boro combinados con el bajo pH (debajo de pH 2) de la mayoría de las pilas de residuos de rocas, han limitado una planeada y temprana revegetación y la colonización natural de las plantas. Un renovado programa para rehabilitación del sitio, comenzada en 2000, se focalizó en el establecimiento de de una cobertura casi completa de la tierra y de ecosistemas funcionales. Pequeñas parcelas (decenas de m2) de bajo pH, ricas en boro y con sustratos sin vegetación aún persisten luego de más de 10 años de rehabilitación y la introducción de una amplia variedad de especies con colonización natural está lentamente avanzando sobre esos lugares remanentes. La rehabilitación ha coincidido y ha contribuido con el aumento del pH en el agua que se escurre desde ≈ 4.5 a ≈ 5.6. This decrease in severity of acid mine drainage (AMD) has apparently become sustainable without further intervention. Una cobertura vegetal casi completa se obtuvo por combinación del programa de plantación y la colonización natural desde islas cercanas de especies nativas establecidas. Ambos procesos fueron acompañados por el desarrollo de ecosistemas funcionales y apoyada por el incremento en la diversidad y la abundacia de invertebrados que aseguran la continuidad de los efectos paliativos sobre los AMD en el sitio. La vegetación establecida a través de procesos naturales puede funcionar ecológicamente a mayor nivel que la vegetación comparable plantada pero puede no dar la deseada cobertura vegetal sobre algunos sustratos.

植被恢复计划减少新西兰南部闭坑煤矿的酸性废水排放

抽象

由于地表径流和地下水渗流对富含黄铁矿矸石堆的淋滤作用,已闭坑的Wangaloa煤矿废水呈酸性(PH值为3-5)。营养贫乏、位置不利、硼量过高、矸石pH值偏低(pH为2)等综合因素限制了早期人为植被恢复计划和天然植被生长。2000年新一轮采后场地复垦计划重启,旨在建立植被全覆盖的功能生态系统。经过十几年复垦和大量物种引入,仅几处数十平方米的小片面积仍低PH值、高硼、无植被覆盖,但这里的天然植被恢复仍缓慢进行。复垦使地表径流的PH值从4.5升至5.6。即使在不进行进一步人为干预的情况下,矿井水酸度仍可持续降低。通过主要物种的人为种植计划和附近岛屿本土物种的天然定植方案相结合,实现了植被全覆盖。上述两种植被恢复过程同时完成了功能生态系统建立,无脊椎动物种类和数量不断增加,能够确保采场酸性废水治理的持久效果。虽然植被的天然恢复过程能够保证植被恢复系统的高水平生态运行,但该方法有时难以保证某些区域达到预期的植被覆盖程度。

Notes

Acknowledgments

This research was funded by the University of Otago, with additional support from Solid Energy New Zealand Ltd. Arne Cleland provided abundant practical comments and advice. AgResearch kindly provided use of their laboratory at Invermay campus for invertebrate heat extractions. We thank John Nunn and Barbara Barratt at Invermay AgResearch for their taxonomic input into Coleoptera, and to Penelope Greenslade at the University of Ballarat (Victoria) for Collembola taxonomy. Additional site information was provided by Megan Bedford, Michelle Begbie, and Genelle Slack. Reviews by two anonymous referees improved the paper.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Geology DepartmentUniversity of OtagoDunedinNew Zealand

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