Spatial distribution and pollution assessment of Cr, Ni and Co in Joghatay ophiolitic region soils (NW Sabzevar), by statistical analysis and sequential extraction

Joghatay plain is located in Sabezvar Ophiolitic Zone and next to the chromite mine. In this research, the soil pollution by heavy metals have been investigated with respect to geochemical, statistical and environmental indicators in Joghatay plain.Material and

Samples were collected seasonally from soil in Joghatay plain within May 2014, and the concentration of heavy metals were measured using ICP-MS method. To the geochemical phases of metals in soil were determined using BCR sequential extraction method.

The result of the analysis of heavy metals in soil samples has shown high concentrations of some elements such as Chromium, Nickel and Cobalt in the southern part of the region. Assessment and correlation of heavy metals in Joghatay region soils by multivariate statistical methods (Pearson correlation, cluster analysis and principal component analysis) show a strong positive correlation between Cobalt, Nickel, Chromium, Iron, Manganese and Magnesium due to the same source  (ophiolitic unit area).

The pollution index (geoaccumulation index, enrichment factor, contamination factor and modified contamination degree) indicates that soil has strongly polluted with regard to Chromium and Nickel and moderately polluted to Cobalt. Sequential extraction method has indicated that more than 50% of Nickel and Chromium concentration in intercahnageable phase. On the other hand ophiolitic rocks and Chromit mining leads releasing of these elements in the area. Though, as far as it gets away from ophiolitic rocks these elements concentration will be decreased. Also element speciation in different phases reveals that the rest elements have concentrated in residual phases and have a lithogenic source.