Translocation of Heavy Metals in the Water-Soil-Plants System From the Lga of Nangere, Yobe State, Nigeria

Heavy metal contamination of irrigation water and agricultural soil poses a serious threat to crop safety and public health because toxic elements can be transferred into edible plant tissues and subsequently enter the human food chain. This study investigated the concentrations and apparent translocation of lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and copper (Cu) within the water–soil–plant system of Dadiso Kukuri, Nangere Local Government Area, Yobe State, Nigeria. Four irrigation water samples, soil, rice, tomato, and onion were collected from selected farms and analyzed using atomic absorption spectrophotometry following acid digestion. The results revealed substantial contamination of the soil and irrigation water by several toxic metals. Soil Pb concentrations ranged from 96 to 107 mg/kg, while Cd, Cr, and As concentrations ranged from 2.90 to 3.42, 70 to 110, and 6.20 to 10.00 mg/kg, respectively. In irrigation water, Pb, Cd, Cr, and As concentrations ranged from 0.03 to 0.05 mg/L, Cd from 0.251 to 0.833 mg/L, Cr from 0.05 to 0.09 mg/L, and As from 0.01 to 0.03 mg/L, respectively. These values exceeded the permissible limits for most or all samples. In contrast, Cu concentrations in soil and water remained below the stated limits in soil and water. Contamination in the water–soil system was reflected in edible crops. Rice contained 0.21–0.25 mg/kg, Cd at 0.46–0.53 mg/kg, Cr at 2.14–2.44 mg/kg, and As at 0.28–0.31 mg/kg. Tomato samples contained 0.10–0.20 mg/kg, Cd at 0.054–0.10 mg/kg, Cr at 0.06–0.34 mg/kg, and As at 0.13–0.20 mg/kg. Onion samples contained 0.32–0.39 mg/kg, Cd at 0.13–0.20 mg/kg, Cr at 2.14–2.40 mg/kg, and As at 0.12–0.30 mg/kg. Most of these concentrations exceeded the corresponding limits stated in the study, whereas Cu remained low in all crops. The findings demonstrate the movement of toxic metals from irrigation water and soil into edible crops and indicate potential dietary exposure risks, particularly from Pb, Cd, Cr, and As. Regular environmental monitoring, irrigation water treatment, improved agricultural practices, and public health interventions are urgently required in the study area.