Trace Elements in Soils around Coal Mines: Current Scenario, Impact and Available Techniques for Management

The present paper reviewed the average concentrations of trace elements in soils near coal mine areas from various cities/countries to provide a current global summary of this issue. The contamination of soils was assessed by using global reference materials and various contamination indices. The results show that the average concentrations of trace elements varied widely: As (0.5–38.3 mg/kg), Mn (86–3,700 mg/kg), Zn (1.5–296 mg/kg), Cu (0.5–110 mg/kg), Cr (17.5–954 mg/kg), Ni (4.3–390 mg/kg), Pb (0.5–433 mg/kg), Cd (0.02–4.48 mg/kg), and Hg (0.02–0.69 mg/kg). Most of these values are higher than the average world background soils and upper continental crust (UCC). The geo-accumulation (I geo ) and contamination factor (CF) indices show that the contamination levels of Ni and Pb are higher than other elements. The potential ecological risk index (E i ) suggests a high risk from Cd, especially in the Tabagi River watershed in Brazil and Ledo coal mines in India, and Hg, especially in Oltu (Turkey). The degree of contamination index (C d ) reveals that the soils from Barapukuria (Bangladesh), Ledo (India), Ptolemais-Amynteon (Greece), and the Tibagi River (Brazil) have a higher degree of contamination than other sites. To control soil contamination, effective monitoring and legislative measures must be taken immediately. For the long term, various physical, chemical, and biological methods should be implemented. Although the selection of suitable methods is site-specific based on the extent and nature of contamination, in general, phytoremediation seems to be more beneficial and cost-effective than physical/chemical techniques.