DETERMINATION OF HEAVY METALS AND SPATIAL DISTRIBUTION OF HEAVY METALS IN SOILS BASED ON SOIL PHYSICOCHEMICAL CHARACTERISTICS, NEAR AN ABANDONED MINE-COMPLEX IN BUMPUS COVE, TN

Waste rock, tailings, and slag generated from mining processes increase heavy metal concentrations in soils, where they may accumulate and eventually threaten environmental and public health. Un-reclaimed abandoned mine sites are especially vulnerable to such accumulation. Once a rich mineralized district of eastern TN, Bumpus Cove contains at least 47 abandoned, un-reclaimed mines, which were permanently closed in the 1950s. Mineral deposits within the cove include primary sulfide deposits, and secondary oxidized deposits within the residual clay. The present study assesses 52 soil samples collected within a 0.67 km² study area encompassing 6 known abandoned Pb, Zn, and Mn mines at the headwaters of Bumpus Cove. Soil samples were analyzed for physical (texture, moisture content, bulk density) and chemical (cation exchange capacity [TEC], pH, total organic carbon [TOC]) properties, then heavy metal (Zn, Mn, Pb, Cu, and Cd) concentrations were determined by microwave-assisted acid digestion and flame atomic absorption spectrometry. Heavy metal concentration ranges as follows: 12 – 1354 mg/kg Zn, 6 – 2574 mg/kg Mn, 33 – 2271 mg/kg Pb, and 1 - 65 mg/kg Cu, and 7 – 40 mg/kg Cd. Of the measured heavy metals, only Zn and Pb concentrations exceed permissible limits. The large range in Zn, Pb, and Mn concentrations is likely due to mining sludge or tailings and slag. Spearman rho coefficient was used to establish correlations between soil physicochemical properties and heavy metal concentrations. All metals are strongly and positively correlated with each other, except for Mn and Cd, which show no correlation. All metals show strong positive association with pH, but only Cu and Cd show a positive association with moisture content. Regression models for Zn concentration using TEC and pH explained 37% variability (R² = 0.37), for Pb using pH explained 50% (R² = 0.50), for Cu, silt and sand explained 37% (R² = 0.37), and for Cd, silt, sand, and pH explained 56% (R² = 0.56) of variability. Soil physico-chemical properties could not explain the variability in Mn concentration. Generally, strong positive correlation is expected between metals, TOC, and clay fractions, but this was not evident in the present study. This study provides data driven explanations for the spatial distribution of heavy metals in Bumpus Cove, TN soils.