Groundwater chemistry affected by trace elements (As, Mo, Ni, U and V) from a burning alum shale waste deposit, Kvarntorp, Sweden

Kristina Åhlgren,Viktor Sjöberg,Bert Allard,Mattias Bäckström

doi:10.1007/s11356-021-12784-2

Kristina Åhlgren, Viktor Sjöberg + Show 2 more

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https://doi.org/10.1007/s11356-021-12784-2

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Abstract

Worldwide, black shales and shale waste are known to be a potential source of metals to the environment. This project demonstrates ongoing weathering and evaluates leaching processes at a 100-m-high shale waste deposit closed in the 1960s. Some deep parts of the deposit are still burning with temperatures exceeding 500 °C. To demonstrate ongoing weathering and leaching, analyses of groundwater and solid samples of shale and shale waste have been undertaken. Largest impact on groundwater quality was observed downstream the deposit, where elevated temperatures also indicate a direct impact from the burning waste deposit. Groundwater quality is largely controlled by pH and redox conditions (e.g., for arsenic, nickel, molybdenum, uranium and vanadium), and the mixture of different waste materials, including pyrite (acidic leachates) and carbonates (neutralizing and buffering pH). Analyses of shale waste from the deposit confirm the expected pyrite weathering with high concentrations of iron, nickel and uranium in the leachates. No general time trends could be distinguished for the groundwater quality from the monitoring in 2004–2019. This study has shown that black shale waste deposits can have a complex long-term impact on the surrounding environment.

Highlights

Black shale is the denomination of a heterogeneous group of dark-coloured sedimentary rocks containing organic matter (Vine and Tourtelot 1969) which to various extents are enriched in sulfides and metals
Ketris and Yudovich (2009) have made estimates of median concentrations based on reported data in black shales globally, e.g., 30 mg/kg for arsenic, 20 mg/kg for molybdenum, 70 mg/kg for nickel, 8.5 mg/kg for uranium and 205 mg/kg for vanadium
The shales are enriched in trace elements such as molybdenum, nickel, uranium and vanadium (Armands 1972; Andersson et al 1985)

Summary

Introduction

Black shale is the denomination of a heterogeneous group of dark-coloured sedimentary rocks containing organic matter (Vine and Tourtelot 1969) which to various extents are enriched in sulfides and metals. Weathering and leaching of shale residues on mining sites and from shale waste dumps lead to release of elements resulting in local and regional environmental impacts. This is reported from numerous sites worldwide, e.g., in Denmark, Norway, Finland, Estonia and Germany in Europe and from the Responsible Editor: Xianliang Yi. USA and China (e.g., Loukola-Ruskeeniemi et al 1998; Puura 1998; Puura et al 1999; Woo et al 2002; Peng et al 2004; Burkhardt et al 2009; Grawunder et al 2009; Jüriado et al 2012; Paikaray 2012; Peng et al 2014; Schovsbo et al 2014; Phan et al 2015; Liu et al 2017; Lerat et al 2018; Parviainen and Loukola-Ruskeeniemi 2019; Stuckman et al 2020; Waersted et al 2020). Mining of alum shale from the 18th to the 20th centuries has led to dispersion of elements from weathering of shale residues, still in progress, notably at Degerhamn, Ranstad and Kvarntorp (e.g., Allard et al 1991, 2011; Falk et al 2006; Kalinowski et al 2006; Lavergren 2008; Lavergren et al 2009; Åhlgren et al 2020)

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