Abstract:
Trace metal contamination in sediment layer is a major issue that aquatic environments encounter.
Trace metals have a higher affinity to partition to the sediment layer posing ecological and public
health risk. In Sri Lanka, a number of studies have reported trace metal contamination in sediments
in both inland and coastal water bodies. Since individual studies are inadequate to assess the overall
status of the contamination, this study aims to evaluate the status of trace metal pollution in both
inland and coastal sediments based on a meta- analytical approach. Studies reporting trace metal
contamination in sediments were acquired from the literature search conducted in Google Scholar
followed by a grey literature search. After screening, 21 articles reporting the sediment
contamination in past 30 years were analysed. Altogether, published results of over 490 samples
were considered for this analysis. Range and median values were calculated. Nonparametric Kruskal Wallis test was performed comparing trace metal contamination between inland and coastal
sediments. Geo-accumulation index was calculated to assess the status of the sediment
contamination. Predominantly detected trace metals in sediments were Pb, Cd, Cu, Cr, Zn, and As. In
both inland and coastal sediments reported median concentrations followed the order
Zn>Cr>Pb>Cu>As>Cd and the reported concentration ranges were 28.99-2672.00, 2.51-845.33,
16.00-1197.00, 3.60-7485.00, 0-188.00, 0-105.66 for inland sediments whereas 31.00-569.52.00,
0.26-270.00, 0.03-121.66, 1.96-96.00, 0.088-10.00,0.01-3.91 for coastal sediments in mg/kg,
respectively. From the available data, significant differences were observed in the contamination
level of Pb, Cu, Cr and Zn between inland and coastal sediments (p<0.05) whereas there was no
significant difference (p>0.05) in the respective As and Cd concentrations. In coastal sediments,
calculated geo-accumulation index for each studied trace metal indicated the contamination status
as “Unpolluted” (Igeo<0). In inland sediments, Pd, Cd and Zn indicated a “Heavy pollution” (3≤Igeo≤4).
Contamination of Cu and Cr indicated a “Moderate to Heavy pollution” (2≤Igeo≤3), while As indicated
a “No pollution” (Igeo≤0). Overall, there was a high level of trace metal contamination in inland
sediments compared to the coastal counterparts. This could be due to high anthropogenic
intervention in inland waterbodies that responsible for trace metal loading. The findings of the
present study provide an overall picture of the trace metal pollution of aquatic sediments in Sri
Lanka.
