Assessment of heavy metal contamination in surface water, sediment and paddy soil in CKDu endemic regions: A comparative study in Minipe and Dambagolla, Sri Lanka

Abstract

Chronic Kidney Disease of unknown etiology (CKDu) is a major health crisis in Sri Lanka, particularly affecting rural agricultural communities in regions such as the Central and Uva provinces. This study investigated the concentrations of heavy metals, alongside various quality indicators, in water, sediment, and paddy soil within CKDu endemic regions of these provinces. The objective is to determine whether toxic heavy metals present in surface water, sediment, and paddy soil correlate with the upraised CKDu incidence in Dambagolla compared to Minipe. Using a stratified random sampling technique, surface water and sediment samples were collected from three locations: Minipe Anicut, Minipe Canal, and Loggal Oya. Eighteen composite sediment samples (six from each location) and thirteen surface water samples (three from Minipe Anicut, two from Minipe Canal, and eight from Loggal Oya) were collected. Additionally, a total of twelve topsoil samples (six from each location) were collected from paddy fields in Minipe and Dambagolla areas in which higher CKDu prevalence was recorded compared to Minipe. Water samples were analyzed for pH, electrical conductivity (EC), hardness, and phosphate using standard methods. Sediment and soil samples were tested for pH, EC, organic matter, potassium, phosphate, and total nitrogen. Heavy metals (Pb, As, Cr, Cd, Ni) were quantified using Inductively Coupled Plasma–Mass Spectrometry (ICP-MS). All analyses were duplicated. Statistical significance across parameters was assessed through ANOVA and Tukey's pairwise comparisons. Water samples from all locations have maintained pH levels within WHO recommendations. Minipe Anicut samples had relatively lower conductivity (141.1±27.27 μS/cm) while having elevated hardness (65.39±7.58 mg/L) and phosphate levels (12.28±9.67 ppm). Pb, Cr, and Cd were not detected in Minipe Anicut, and Cr was absent in Minipe Canal. Arsenic levels, although within WHO standards, were higher than other metals, particularly in Minipe Canal (4.17±0.03 µg/L) and Loggal Oya (5.25±3.89 µg/L). ANOVA showed no significant differences in heavy metal levels among sites (p>0.05). Sediment samples from Minipe Canal had lower levels of Cr (11.93±0.37 mg/kg) Pb (2.52±1.06 mg/kg), As (0.62±0.30 mg/kg), Cd (0.013±0.010 mg/kg), and potassium, resulting in substantially lower conductivity. In Minipe Anicut and Loggal Oya, heavy metal content followed the order Cd < As < Pb < Ni < Cr, with Minipe Anicut showing slightly higher concentrations. Furthermore, paddy soil analysis showed higher organic matter content in Dambagolla (4.16±0.46%) compared to Minipe (1.22±0.15%), while Minipe had higher heavy metal concentrations and potassium content (p<0.05). The results suggest that agricultural activities, natural geological factors, and localized contamination sources influence the water, sediment, and soil quality in the studied areas. Furthermore, findings reveal that heavy metal concentrations in surface water, sediment, and paddy soil were not significantly linked to the higher CKDu prevalence in Dambagolla compared to Minipe, suggesting greater influence from other critical factors, driving CKDu development in this region.