Abstract
This study is based on agricultural soil samples which are collected along three traverses (A, B, C), near the gypsum quarries located near the village of Bajwan north of Kirkuk city, to conduct a geochemical analysis and determining some heavy elements (Co, Cr, Ni, Cu, Sr, Pb, Cd) levels in the surface and subsurface soil horizons, and to indicate the potential sources of contamination with these elements. Accordingly, 30 samples were collected (six samples from travers A, five samples from travers B, and four samples from travers C) from the soil for each of the surface and subsurface levels. The results showed that the average concentrations of most studied elements increased in the subsurface soil compared to the surface soil, as a result of the influence of different geological and environmental conditions on the distribution of these elements in different soil horizons. The concentrations of the studied elements (Co, Ni, Cd) are more than their natural concentrations when compared to the natural abundance of these elements in the earth's crust, which indicates an increase in the concentration of these elements in the soil as a result of the proximity of the study area to the oil industries activities, causing the emission of high concentrations of heavy elements. As well as the traffic density of vehicles, causing the release of high concentrations of some elements. The geo accumulation factor (Igeo) indicates that most of the soil samples within different horizons of most of the heavy elements are uncontaminated to moderately contaminated, and moderately contaminated for cadmium. Also, by calculating the RI and the environmental risk factor (Er), it was found that the relative content of cadmium in soil samples recorded a considerable potential ecological risk to a high potential ecological risk. This indicates high affinity of cadmium in the soil as its infiltration into the subsurface layers.
Highlights
Heavy elements are one of the most important environmental pollutants because of their toxicity and their long durability, where they can be transported to long distances from their areas of origin (Edem et al, 2002)
The results of the geochemical analyzes of soil samples in the surface and subsurface horizon shown in Tables 2, 3 and Fig. 3 indicate that the average concentration of cobalt (Co) is 16.09 ppm in the surface soil, and 16.69 ppm in the subsurface soil, and in all the studied samples is higher than its concentration rates in the soil ranged (1-40ppm) according to (Alloway, 1990), as well as from concentrations in the earth's crust according to (Kabata-Pendias and Mukherjee, 2007), which is (10-12ppm)
It is apparent through the results of the geochemical analysis that the relative content of the concentration of trace elements in the surface and subsurface soil is in the following descending order: (Sr> Ni> Cr> Cu> Co> Pb> Cd), and that the concentration of the elements (Co, Ni, Cu, Cr, Sr) in subsurface soils is more than surface soil sample, may be attributed to the effect of weathering and washing processes of the surface soil sample components and their concentration in the deep subsurface horizons of the soil by the effect of accumulation or depletion processes
Summary
Heavy elements are one of the most important environmental pollutants because of their toxicity and their long durability, where they can be transported to long distances from their areas of origin (Edem et al, 2002). The current research aims to study the geochemical distribution of heavy elements (Co, Cr, Ni, Cu, Sr, Pb, Cd) in the soil, and to identify the geochemical relationships by using the statistical program (SPSS, V22) to conducting some statistical operations Multivariate Statistical Analysis (MSA), to know the geochemical behavior of trace elements in surface and subsurface soil samples with other chemical components and probable sources there in order to identify about the role of natural resources and the impact of human activities in increasing the concentration of trace elements in the surface and subsurface soil, as well as assessing environmental impacts of heavy elements within the different horizons of the soil and determine the health risks (carcinogen and non-carcinogenic) it has on the health of residential communities located in the area
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