The Effect of Weathering on Salt Release from Coal Mine Spoils

Abstract

Coal mine spoils have the potential to create environmental impacts, such as salt load to surrounding environments, particularly when exposed to weathering processes. This study was conducted to understand the effect of physical and chemical weathering on the magnitude, rate, and dynamics of salt release from different coal mine spoils. Five spoil samples from three mines in Queensland were sieved to three different particle size fractions (<2 mm, 2–6 mm, and >6 mm). Two samples were dispersive spoils, and three samples were nondispersive spoils. The spoils were subjected to seven wet–dry cycles, where the samples were periodically leached with deionised water. The rate, magnitude, and dynamics of solutes released from spoils were spoil specific. One set of spoils did not show any evidence of weathering, but initially had higher accumulation of salts. In contrast, broad oxidative weathering occurred in another set of spoils; this led to acid generation and resulted in physical weathering, promoting adsorption–desorption and dissolution and, thus, a greater release of salts. This study indicated that the rate and magnitude of salt release decreased with increasing particle size. Nevertheless, when the spoil is dispersive, the degree of weathering manages salt release irrespective of initial particle size. This study revealed that the long-term salt release from spoils is not only governed by geochemistry, weathering degree, and particle size but also controlled by the water/rock ratio and hydrological conditions of spoils.

The Relationship between Acid Production and the Microbial Community of Newly Produced Coal Gangue in the Early Oxidation Stage

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Quantifying the environmental impact of a major coal mine project on the adjacent Great Barrier Reef ecosystems

“…Recommendation 1: Implement reactive mine management systems Fine-grained sediments up to 64 µm diameter, corresponding to clays and silts, are commonly found amongst coal mine spoil run-off and coal dust particles (Hilton et al, 2019;Qian et al, 2019;Sapko et al, 2007;Spain and Hollingsworth, 2016). Such fine-grained sediments settle very slowly and remain mostly suspended in the water column, even in decantation ponds.…”

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