Heavy metals in agricultural soils and level of contamination with crop production

Abstract

Heavy metals (HM) can be defined as metallic elements that are greater than 40 in atomic weight and above 5 g/cm3 in specific gravity and cause abnormal effects on the biota at low concentrations. This study aimed to assess the levels of HM contamination in soils and unpolished rice grains (Oryza sativa) at three separated paddy cultivation fields in Anuradhapura, Gampaha, and Jaffna over one consecutive season. The concentrations of arsenic (As), cadmium (Cd), and lead (Pb) were detected using inductively coupled plasma mass spectrometry (ICP-MS). According to the results, HM concentrations of As and Pb in the soil for all studied fields were below the maximum permissible limits (MPL) set by the World Health Organization/Food and Agriculture Organization (WHO/FAO). However, Pb content in rice grains was high in all stations relative to the MPL for crops given by WHO/FAO. The results revealed that Cd has exceeded MPL of both soil and grains in the Jaffna paddy field according to the WHO/FAO guidelines and Cd has a high transfer factor (TF>0.27) from soil to grain among all concerned agricultural lands. Other heavy metals have lower TF values (0.001 to 0.131). Regarding the contamination factor, As, Cd and Pb showed a moderate level of contamination severity over three regions.