Evaluation of Spatial Distribution of Soil Cadmium and Cadmium Hot Points in a Part of an Arable Lands in West of Shiraz in Fars Province by Kriging Method

Soil pollution, in general, and heavy metals contamination, in particular, are problems of modern life. In this context, surveying contaminated soils becomes essential for keeping away human food chains from dangerous heavy metals. This study was conducted to evaluate soil Cd-contamination in part of the arable lands in Bizaa, west of Shiraz. Soil samples were randomly collected from an area of 800,000 m2, prepared, and analyzed for Cd concentration. Analysis of variograms showed that the structural component moderately dominated the randomized component and that the range of special dependency was 2300 m. Ordinary kriging was used for mapping and estimation variances were calculated. Based on the Cd contamination standard threshold (3mg/Kg), the map thus prepared indicated that about 80 percent of the study area was polluted and that the hot point was located in the southern stretches of the study area. The non-existence of industrial activities and the absence of point Cd distribution indicated that soil pollution in the area must have been caused by human activities such as farming. The excessive consumption of chemical fertilizers, especially phosphates, in agricultural activities and sludge application seem to be the main suspects of soil Cd contamination. Further investigation is needed into the agricultural history of the area to determine the main causes of Cd contamination in this area.