Evaluation of Heavy Metal Pollution in Rice (Oryza sativa L.) Fields of Bafra Plain

Abstract

Heavy metals are naturally present in the soils in trace quantity. Besides, some soils include these elements at high levels resulting from the weathering of minerals or human activities. Contamination of these metals has been of great concern in the environment interrelatedly with their toxicity, persistence and non-degradability. So, this article aimed to evaluate heavy metal pollution by using several pollution indices contamination factor (CF), degree of contamination (CD), pollution load index (PLI), summarization of the sources of heavy metals, and change of these metals along soil depth. For this purpose, 10 coordinated soil samples were taken from 0-20 cm and 20-40 cm depths in the rice fields of Bafra Plain in Samsun-Türkiye. In these samples, some physico-chemical soil characteristics (texture, pH, electrical conductivity, organic matter and lime content, available phosphorus and cation exchange capacity) and heavy metal contents Zinc (Zn), copper (Cu), nickel (Ni), cobalt (Co), cadmium (Cd), chromium (Cr) and lead (Pb) were determined. According to the results, metal contents were determined between 39.79-58.44 mg kg-1, 32.15-68.31 mg kg-1, 75.68-132.6 mg kg-1, 11.95-18.02 mg kg-1, 0.001-0.278 mg kg-1, 61.88-102.5 mg kg-1, and 9.942-14.67 mg kg-1 for Zn, Cu, Ni, Co, Cd, Cr and Pb, respectively. While Cd content was higher at 0-20 cm depth, Cr, Ni and Zn values were higher at 20-40 cm. Cu, Pb and Co values did not show significant change with depth. Average CF values for heavy metals were determined as Ni>Pb>Cr>Cu>Cd>Zn>Co. Degree of contamination values varied between 4.922-7.848 and PLI values varied between 0.946-1.028. In all elements, CF and CD values were classified in the group of low and moderate contamination. Besides, significant relationships were found between soil physicochemical properties, heavy metal concentrations and pollution indices.