Abstract
Abandoned mining sites often cause contamination of surface and subsurface waters. A 3-month pot experiment was performed to evaluate the influence of waste mixed with biochar as a soil amendment on a series of chemical characteristics and trace element solubility in a mine soil. Trace element concentrations were measured in pore water of the mine soil reclaimed with different proportions of waste-biochar amendment (20, 40, 80 and 100%) and grown with <em>Brassica juncea</em>. The results showed that amendment application improved soil conditions such as pH, total carbon, dissolved organic carbon, total nitrogen, and strongly reduced the concentration of Al (99.99%), Co (99.95%), Cu (99.97%), Fe (99.79%) and Ni (99.91%) in pore water, compared to the unamended soils. Waste and biochar also promoted the establishment of <em>B. juncea</em> in the mine soil. These results highlight the importance of mitigating the impacts from abandoned mines sites on water quality. The use of waste and biochar as soil amendment combined with <em>B. juncea</em> plants was effective in reducing metal concentrations in pore water and the associated toxicity risk.
Highlights
Mining areas are characterised by young, poorly developed soils often with scarce or absent vegetation cover due to extreme pH values, poor fertility conditions, low organic matter contents and degraded soil structures, usually with high metals and another potential hazardous elements (Mench et al 2010)
The soil from the settling pond at the mine of Touro had an extremely acid pH (2.96), pseudototal Cu concentration of 452 mg kg-1 and soil total carbon (TC), soil total nitrogen (TN) and dissolved organic carbon (DOC) contents were below the detection limit (TC content < 4.0 g kg-1, TN content < 1.5 kg-1) (Table 2)
The results presented in this study suggested that a mixture of wastes and biochar have the potential to significantly affect the behavior of trace elements in a mine soil by altering their solubility in the soil
Summary
Mining areas are characterised by young, poorly developed soils often with scarce or absent vegetation cover due to extreme pH values, poor fertility conditions, low organic matter contents and degraded soil structures, usually with high metals and another potential hazardous elements (Mench et al 2010). Reducing trace element contamination in mine soils, especially in the soil pore water, is important due to its impact on surface and subsurface waters (Beane et al 2016). The presence of a vegetation cover in mine soils reduces the potential transport of contaminants to surface and ground waters (Beesley et al 2014; Ruttens et al 2006). These soils often have important limitations for revegetation due to their extremely degraded conditions (Thakur et al 2016)
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