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Mine Water and the Environment

, Volume 34, Issue 1, pp 59–74 | Cite as

Assessing the Environmental Hazard of Using Seawater for Ore Processing at the Lasail Mine Site in the Sultanate of Oman

  • Philipp WannerEmail author
  • Mohammed Yasser Nasser Al-Sulaimani
  • Niklaus Waber
  • Christoph Wanner
Technical Article

Abstract

The Lasail mining area (Sultanate of Oman) was contaminated by acid mine drainage during the exploitation and processing of local and imported copper ore and the subsequent deposition of sulphide-bearing waste material into an unsealed tailings dump. In this arid environment, the use of seawater in the initial stages of ore processing caused saline contamination of the fresh groundwater downstream of the tailings dump. After detection of the contamination in the 1980s, different source-controlled remediation activities were conducted including a seepage water collection system and, in 2005, surface sealing of the tailings dump using an HDPE-liner to prevent further infiltration of meteoric water. We have been assessing the benefits of the remediation actions undertaken so far. We present chemical and isotopic (δ18O, δ2H, 3H) groundwater data from a long-term survey (8–16 years) of the Wadi Suq aquifer along a 28 km profile from the tailings dump to the Gulf of Oman. Over this period, most metal concentrations in the Wadi Suq groundwater decreased below detection limits. In addition, in the first boreholes downstream of the tailings pond, the salinity contamination has decreased by 30 % since 2005. This decrease appears to be related to the surface coverage of the tailings pond, which reduces flushing of the tailings by the sporadic, but commonly heavy, precipitation events. Despite generally low metal concentrations and the decreased salinity, groundwater quality still does not meet the WHO drinking water guidelines in more than 90 % of the Wadi Suq aquifer area. The observations show that under arid conditions, use of seawater for ore processing or any other industrial activity has the potential to contaminate aquifers for decades.

Keywords

Acid mine drainage (AMD) Groundwater contamination Salinity contamination Remediation 

Bewertung der Umweltgefahr durch die Nutzung von Meerwasser in der Erzaufbereitung der Lasail Mine im Sultanat Oman

Zusammenfassung

Das Lasail-Bergbaugebiet (Sultanat Oman) wurde während der Gewinnung, der Aufbereitung, und der Entsorgung von lokalen und importierten Kupfererzen in einer unversiegelten Deponie, durch saures Sickerwasser kontaminiert. Zusätzlich bewirkte die Verwendung von Meerwasser in den ersten Stadien der Erzaufbereitung eine Versalzung des ursprünglich süßen Grundwassers im unmittelbaren Abstrombereich der Deponie. Nach der Entdeckung der Kontamination in den 1980er Jahren wurden verschiedene Verfahren zur Sanierung der Kontaminationsquelle eingesetzt, wie beispielsweise ein System der Sickerwassersammlung. Im Jahre 2005 wurde die Deponie mit einer HDPE-Folie abgedeckt, um einer weiteren Einsickerung meteorischer Wässer vorzubeugen. In der vorliegenden Studie wird der Nutzen der bisherigen Sanierungsmaßnahmen bewertet. Es werden chemische und isotopische (δ18O, δ2H, 3H) Grundwasserdaten einer Langzeitbeobachtung (8–16 Jahre) des Wadi Suq Aquifers präsentiert, welche eine Distanz von 28 km von der Deponie bis zum Golf von Oman abdecken. Während dieser Zeit fielen die meisten Metallkonzentrationen im Grundwasser des Wadi Suq unter die Nachweisgrenzen. Auch die Versalzung des Grundwassers in den Bohrlöchern im unmittelbaren Abstrombereich der Deponie nahm seit 2005 um 30 % ab. Diese Verringerung ist vermutlich durch die Oberflächenabdeckung der Deponie bedingt, welche die Durchspülung der Deponie durch die zwar seltenen, aber gewöhnlich sehr heftigen Regenfälle verminderte. Trotz der generell niedrigen Metallkonzentrationen und der verminderten Versalzung des Grundwassers erreicht die Grundwasserqualität in über 90 % des Wadi Suq Aquifers immer noch nicht die WHO-Mindestanforderungen für Trinkwasser. Die Beobachtungen ergeben, daß die Nutzung von Meerwasser zur Erzaufbereitung oder zu anderen industriellen Aktivitäten unter ariden Bedingungen das Potential hat, Aquifere für Jahrzehnte zu verunreinigen.

Relevando el riesgo ambiental de usar agua de mar para el procesamiento de minerales en la mina Lasail en el sultanato de Oman

Resumen

El área minera Lasail (Sultanato de Omán) fue contaminada por drenaje ácido de minas durante la explotación y el procesamiento de minerales de cobre, tanto locales como importados, y el subsecuente depósito de residuo de material con sulfuros en un dique de colas no sellado. En este ambiente árido, el uso del agua de mar en los pasos iniciales del procesamiento del mineral causó contaminación salina del agua subterránea fresca corriente abajo del dique de colas. Después de la detección de la contaminación en la década de los 80, se realizaron diferentes actividades de remediación incluyendo un sistema colector de agua de filtración y, en 2005, el sellado superficial de los diques de colas usando un revestimiento HDPE para prevenir futuras infiltraciones de agua meteórica. Hemos estado relevando los beneficios de las acciones de remediación realizadas hasta ahora. Presentamos los datos químicos e isotópicos (18O, 2H, 3H) del agua subterránea del acuífero Wadi Suq a lo largo de un perfil de 28 km del dique de colas del Golfo de Omán durante un largo período (8–16 años). Durante este período, la mayoría de las concentraciones de metales en el agua subterránea Wadi Suq descendieron por debajo de los límites de detección. Además, en las primeras perforaciones corriente abajo del dique de colas, se encontró que la contaminación salina había decrecido en un 30% desde 2005. Este descenso parece estar vinculado al cubrimiento de la superficie de las colas, lo que reduce la percolación de las colas por las esporádicas pero usualmente copiosos eventos lluviosos. Más allá de las bajas concentraciones de metal y de la salinidad decreciente, la calidad del agua subterránea no cumple las normas WHO de agua potable en más del 90% del área del acuífero Wadi Suq. Las observaciones muestran que bajo condiciones áridas, el uso de agua de mar para el procesamiento de minerales o para cualquier otra actividad industrial, tiene el potencial de contaminar los acuíferos por décadas.

利用海水处理矿石对阿曼Lasail采场的地下水环境影响评价

抽象

阿曼(Sultanate of Oman)Lasail矿区在开采和处理本地及外来铜矿石以及将含硫化物的废矿石堆放于未密封的尾矿堆时,产生的酸性废水污染了矿区地下水。在干旱条件下,用海水进行矿石处理污染了尾矿堆下游的地下淡水。在20世纪80年代检测出地下水污染之后,开展了系列控制污染源的水环境修复工程,包括溶滤水集取及阻止大气降水渗入尾矿堆的HDPE覆盖(2005年)。研究已完成水环境修复工程的效果评价。本文分析了Wadi Suq含水层沿尾矿堆至阿曼湾剖面(长28km)8~16年的长期水化学和水文同位素(δ18O, δ2H, 3H)监测资料。结果显示,Wadi Suq含水层地下水的多数重金属浓度降到了检测限以下。同时,尾矿池下游第一个钻孔的盐度污染自2005年已减少30%。上述变化与尾矿池表面覆盖程度相关,因为它减少了零星小雨、有时大雨对尾矿的直接冲刷。虽然地下水重金属浓度降低、盐度降低,但是该剖面90%以上的Wadi Suq地下水水质仍不符合世卫组织(WHO)的饮用水指南要求。研究结果显示,干旱区使用海水进行矿物加工或用于其它工业过程存在使地下水污染几十年的潜在风险。

Notes

Acknowledgments

We thank the Ministry of Water Resources, the Oman Mining Company, Sultanate of Oman, and the Swiss Academy of Sciences (SCNAT+) for financial support and for access to the Lasail mining site and the boreholes in Wadi Suq. Analytical support by Dr. Sabah (Directorate General of Minerals), R. Mäder, P. Bähler, and S. Weissen (Institute of Geological Sciences, University of Bern) is highly acknowledged. The constructive comments by two anonymous reviewers greatly helped improve the manuscript.

Supplementary material

10230_2014_281_MOESM1_ESM.pdf (53 kb)
Amounts of rainfall in the Sohar area between 1980 and 2012; the horizontal line indicates the average precipitation of the last 31 years; data from the Ministry of Transport and Communications, Sultanate of Oman, Directorate General of Meteorology and Air Navigation (PDF 52 kb)
10230_2014_281_MOESM2_ESM.pdf (157 kb)
X-ray diffraction pattern of tailings material from the uppermost 4 m of the tailings pond (bulk rock)(PDF 156 kb)
10230_2014_281_MOESM3_ESM.docx (47 kb)
Supplementary material 3 (DOCX 47 kb)

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Philipp Wanner
    • 1
    Email author
  • Mohammed Yasser Nasser Al-Sulaimani
    • 1
    • 2
  • Niklaus Waber
    • 1
  • Christoph Wanner
    • 3
  1. 1.RWI, Institute of Geological SciencesUniversity of BernBernSwitzerland
  2. 2.Earth SecretsAl-AthiaibahSultanate of Oman
  3. 3.Earth Sciences DivisionLawrence Berkeley National LaboratoryBerkeleyUSA

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