Risk assessment of agricultural soils surrounding an iron ore mine: A field study from Western Ghat of Goa, India

Abstract

ABSTRACT Goa, a biodiversity hotspot, is also a major iron ore producing state in India. This study investigated total heavy metal (HM) contamination in 65 georeferenced soil samples through inductively coupled plasma atomic emission spectrophotometer (ICP-AES) for assessing risk of mining activity on agricultural soils. The mean concentrations of copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), chromium (Cr), cadmium (Cd), manganese (Mn), iron (Fe) and cobalt (Co) were 125.60, 75.60, 96.40, 51.20, 69.30, 25.77, 2091, 162638 and 21.20 mg kg−1, respectively. Lower pH, higher organic carbon (OC) and fine-textured soil augmented metal accumulation processes. Boxplot of geoaccumulation index (I geo) values indicated that lead (Pb) metal had more variation in the study area. Mean Igeo values of metals in descending order are Fe (4.24) > Mn (3.08) > Cu (2.84) > Co (2.47) > Pb (1.85) > Cd (0.7) > Zn (0.58) > Ni (0.45) > Cr (0.16). Mean values of modified degree of contamination (mCdeg) (10.4) and pollution load index (PLI) (6.19) revealed high contamination with deteriorating soil quality. Combined approach of correlation, principal component (PC) and cluster analysis indicated the source of origin by describing association of metals with Fe. PC biplot showed that impact of mining was more on lowland agro-ecosystem rather than natural due to slope factor which led to clogging of pores by mining overburden mixed soil deposition from uphill as evidenced from the presence of waterlogged fallow lands. Fuzzy k-mean clustering yielded three contamination zones (CZs) of low (CZ2), moderate (CZ1) and high (CZ3) degree of contamination. The CZs-based site-specific land management plan might lead to a sustainable ecosystem through coexistence of both mining and agricultural activity by arresting contamination and restoring fallow lands.