Detection of Ni, Cd, and Cu in green leafy vegetables collected from different cultivation areas in and around Colombo District, Sri Lanka.

Five types of green leafy vegetables ["Kankun" (Ipomoea aquatica), "Mukunuwenna" (Alternanthera sessilis), "Thampala" (Amaranthus viridis), "Nivithi" (Basella alba), and "Kohila leaves" (Lasia spinosa)] were randomly collected from six different locations (Wellampitiya, Kolonnawa, Kottawa, Piliyandala, Bandaragama, and Kahathuduwa) in and around Colombo District, Sri Lanka, and subjected to analysis of three heavy metals [nickel (Ni), cadmium (Cd), and copper (Cu)] by atomic absorption spectrometry. Soils from green leafy vegetable cultivation lands and irrigated water were also tested. The average concentrations of heavy metals Ni, Cd, and Cu in soils were 51.5 ± 45.5, 1.4 ± 1.1, and 66.5 ± 59.5 mg kg(-1), respectively. The highest Ni contamination was detected in the irrigated water samples from Wellampitiya (2.02 mg L(-1)) followed by Kolonnawa (1.02 mg L(-1)) and Kahathuduwa (0.25 mg L(-1)) areas. This has exceeded the WHO/FAO guideline (0.2 mg L(-1)). However, Cd and Cu contents in all tested irrigated water samples were well below the detection limits. Significant differences were observed in Ni, Cd, and Cu levels, between both production sites and green leafy vegetables analyzed (P < 0.05). The mean concentrations (mg kg(-1), dry weight basis) of heavy metals in all green leafy vegetable samples collected from six areas varied as 0.23 ± 0.15 for Cd, 12.60 ± 9.01 for Cu, and 7.62 ± 8.41 for Ni. Maximum Ni, Cd, and Cu contaminations were found in the green leafy vegetables collected from Kolonnawa area. Among the green leafy vegetables analyzed, "Kohila leaves" have the highest tendency to accumulate Ni, Cd, and Cu from the environment.