Abstract
Soil characterization is a vital activity to develop appropriate and effective restoration protocols for mine wastelands while insights into the total content of heavy metals in the soil is an important step in estimating the hazards that the metals may pose to the vital roles of soil in the ecosystem. This study addressed the following research questions: (1) To what extent do the physico-chemical characteristics vary between mine waste sediments and the nearby forest soil? (2) Are the concentrations of heavy metals high enough to be considered as toxic? and (3) Are heavy metals present in mine waste sediments potential sources of pollution? We hypothesized that the physico-chemical characteristics of mine waste sediments are less favorably for plant establishment and growth while the concentrations of heavy metals are very high, thus restricting the success of revegetation of mine waste lands. Mine waste sediments were sampled following a diagonal transect across tailings dams, overburden dump sites and the local forest soil from the top layer (0–20 cm) using a closed auger. Samples were analyzed for arsenic, barium, lead, cadmium, cobalt, copper, chromium, nickel, vanadium, and zinc as well as for soil physico-chemical properties. The mine waste sediments were dominated by silt whilst the forest soil by sand particles, with significantly high bulk density in the former. Both the forest soil and overburden sediments were acidic than the alkaline tailings dam sediment. Total organic carbon and nitrogen contents were significantly low in mine wasteland substrates but the concentration of Ca and Mg were significantly higher in tailings dam substrate than the forest soil. The concentrations of available P, K and Na were similar across sites. The mean concentrations of heavy metals were significantly (p < 0.01) higher in mine waste sediments than the forest soil; except for cadmium (p = 0.213). The order of contamination by heavy metals on the tailings was Cu > Co > Ba > Ni > As > Zn > Pb > Cr > V > Cd, and that on the overburdens was Cu > Co > Ba > Ni > Zn > Cr > Pb > V > As > Cd. The pollution load index (PLI) was nearly twice higher for the tailings dam (8.97) than the overburden (5.84). The findings show that the copper mine wastes (the tailings dams and overburden waste rock sites) are highly contaminated by heavy metals; which, in turn, might pose serious hazards to human health and agricultural productivity. In addition, poor macro-nutrient availability, substrate compaction and soil acidity (particularly on overburden sites) coupled with toxic level of heavy metals would be the main challenges for successful phytostabilization of copper mine wastelands.
Highlights
There is a global concern regarding the high input and flow of heavy metals and metalloids in the biosphere; elements which on a global perspective should normally be present in very low concentrations (Monterroso et al 2014)
This study addressed the following research questions: (1) To what extent do the physico-chemical characteristics vary between mine waste sediments and the nearby forest soil? (2) Are the concentrations of heavy metals high enough to be considered as toxic? and (3) Are heavy metals present in mine waste sediments potential sources of pollution? We hypothesized that the physicochemical characteristics of mine waste sediments are less favorably for plant establishment and growth while the concentrations of heavy metals are very high, restricting the success of revegetation of mine waste lands
Poor macro-nutrient availability, substrate compaction and soil acidity coupled with toxic level of heavy metals would be the main challenges for successful phytostabilization of copper mine wastelands
Summary
There is a global concern regarding the high input and flow of heavy metals and metalloids in the biosphere; elements which on a global perspective should normally be present in very low concentrations (Monterroso et al 2014). Mining and processing of metal ores, such as copper, can be a significant source of environmental pollution; thereby affecting environmental quality and ecosystem services (Zhuang et al 2009). Some heavy metals, such as iron, boron, manganese, zinc, copper and molybdenum, are micronutrients essential for plant growth, high concentrations of all heavy metals are toxic and are regarded as pollutants (Chehregani et al 2004). Soils heavily contaminated by heavy metals, such as Cu, Pb, Zn and Ni, restrict plant growth, cause leaf chlorosis and alteration of the activity of many key enzymes of various metabolic pathways. Contaminated soils adversely affect the number, diversity and activity of soil organisms, inhibiting soil organic matter decomposition and N-mineralization processes (Wong 2003; Gowda et al 2010)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
