Assessment of heavy metals in Mukunuwenna (Alternanthera sessilis) collected from production and market sites in and around Colombo District, Sri Lanka

Abstract

The present study was conducted to evaluate the levels of trace metals (Ni, Cd, Cr, Pb and Cu) in Mukunuwenna (Alternanthera sessilis) samples randomly collected from the production and market sites located in and around Colombo District, Sri Lanka, using the Atomic Absorption Spectrophotometry. Significant differences in heavy metal concentrations were observed between both the production sites and market sites (P<0.05). Heavy metal accumulations in Mukunuwenna tested were higher at the market sites than at the crop production sites. The average concentrations (mg kg-1) of heavy metals in Mukunuwenna samples collected from the production sites were estimated as Ni (6.48±6.74), Cd (0.20±0.11), Cr (3.36±2.76), Pb (2.96±2.16) and Cu (11.85±7.51). The mean concentrations (mg kg-1) of Ni, Cd, Cr, Pb and Cu in Mukunuwenna samples collected from different marketing sites were reported as 7.90±5.98, 0.25±0.18, 4.09±3.36, 3.63±3.65, 13.05±5.15 respectively. The highest contaminated field and market samples were reported from the Kolonnawa area. The samples collected from the market sites were subjected to three processing treatments (raw, cooked and stir-fried) and analyzed for heavy metals, in order to find out the effect of food processing techniques on reducing the heavy metal contaminations of Mukunuwenna samples. The average levels (mg kg-1) of metals detected in raw, cooked and stir-fried Mukunuwenna samples were as follows: Ni (2.20±1.04, 1.77±0.84, 1.46±1.03), Cd (0.19±0.11, 0.12±0.07, 0.10±0.06), Cr (2.37±1.58, 2.27±1.57, 2.20±1.54), Pb (0.26±0.39, 0.22±0.34, 0.21±0.34) and Cu (9.59±4.48, 8.29±3.35, 7.45±3.72). The results showed no significant differences in heavy metal contents among three processing methods (P<0.05). Therefore, the type of processing method has a minimal effect on reducing the heavy metal contents of Mukunuwenna samples.