Ecological Risk of Heavy Metal in Agricultural Soil and Transfer to Rice Grains

Higher accumulation of toxic heavy metals in rice grain and agricultural soil may lead to an imbalanced ecosystem. The present study was carried out to assess the risk of different heavy metals nickel, copper, arsenic, lead, and manganese in agricultural soil and transfer status to rice grain. The samples were collected from four agricultural fields at different times in the Dumuria Upazila (sub-district) under Khulna district in Bangladesh. Heavy metal concentration in soil extracts, irrigation water samples, and grain samples was determined by Atomic Absorption Spectrometry (AAS). Average metal concentrations were calculated and compared with the reference value in soil. In most of the cases, the existence of heavy metals in agricultural soil was greater than the reference soil which is a rising concern. Overall risk index (RI) stated that the examined soils were at moderate risk of contamination. Transfer factor (TF) of Arsenic (0.037 to 0.115) and Manganese (0.056 to 0.155) from soil to rice grain were higher that is also a matter of concern. On the other hand, TF of Lead (Pb) was found in a very negligible amount which is a good sign. Regular monitoring of heavy metals in agricultural soil should be initiated and the awareness level should be increased to avoid environmental problems.