The content of nickel (Ni), cadmium (Cd), chromium (Cr), lead (Pb) and copper (Cu) in five different types of green leafy vegetables viz., "Kangkung" (Ipomoea aquatica), "Mukunuwenna" (Alternanthera sessilis), "Thampala" (Amaranthus viridis), "Nivithi" (Basella alba) and "Kohila" (Lasia spinosa) collected from four randomly selected urban and sub urban market sites in and around Piliyandala area of Colombo District, Sri Lanka, were measured using atomic absorption spectrometry. The results showed significant differences in elemental concentrations among the green leafy vegetables analyzed. The average concentrations of heavy metals detected in green leafy vegetables ranged from 0.

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.

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Green Leafy Vegetables (GLV) are a key component of the Sri Lankan diet. However, GLV are identified as good heavy metal accumulators, which in turns causes potential health risks for consumers through food chain contaminations. The present study aimed to investigate the bioaccumulation, translocation and distribution patterns of cadmium (Cd) and lead (Pb) in five key Sri Lankan GLV ["Kankun" (Ipomoea aquatica), "Mukunuwenna (Alternanthera sessilis), "Thampala" (Amaranthus viridis), "Nivithi" (Basella alba) and "Kohila" (Lasia spinosa)] grown in Colombo District, Sri Lanka. The levels of Cd and Pb in different plant parts (roots, stems and leaves) and the soil underneath were determined using the inductively coupled plasma optical emission spectroscopy (ICP-OES) and the bioaccumulation and translocation factors of heavy metals from soil to different plants parts (roots, stems, leaves), were calculated to identify the hyper accumulative species.Irrespective of the species and the location, GLV showed the distribution pattern for Cd and Pb as: roots>stems>leaves. In all the analyzed GLV, roots have accumulated significantly higher concentrations (at P<0.05) of Cd and Pb compared with stems and leaves. Among the two heavy metals, Cd bioavailability was higher compared with Pb. Amaranthus viridis had the lowest capacity for metal enrichment. In contrast, Lasia spinosa showed the highest bioaccumulation factors for both elements and the accumulation factor obtained for Cd (1.04) was >1. Thus, Lasia spinosa has the potential to use in phytoextraction purposes in future, though it is not safe to consume as a day to day food item.