Abstract:
Kirala Kale is an urban wetland in southern Sri Lanka. This study examined the aquatic pollution status within the wetland in relation to the nearby land-use composition. Eight water sampling sites considering inlets and outlets, low flow rate, and easy access were selected to represent the whole wetland. Percentages of different land-use types (urban, forest, marshlands, paddy lands, sparse vegetation, and water bodies) within a 300m buffer area around each site were assessed via remote sensing and GIS. Temperature, Electrical conductivity (EC), Total Dissolved solids, Salinity, Dissolved Oxygen, pH, Nitrate (NO3-), Orthophosphate (PO43-), Heavy metals (Cu, Cd, Cr, Pb) in water and macro-benthos in sediment were analyzed at two sampling occasions with three replicates from each site. There were significant positive spearman rank correlations between the proportion (%) of Urban and settlement land cover and NO3-(r = 0.762, p < 0.01), PO43- (r = 0.738, p < 0.01), and EC (r = 0.833, p < 0.01). Similarly, Paddy land cover and NO3- (r = 0.994, p < 0.05), and PO43-(r = 0.994, p < 0.05) were positively correlated. Negative correlations were observed between forest cover and NO3-(r = - 0.708, p < 0.01), and sparsely distributed vegetation and NO3- (r = - 0.881, p < 0.05), and PO43- (r = - 0.905, p < 0.05). Cu and Cd concentrations (0.006-0.022 ppm) were below the accepted limits (0.05 ppm and 0.03 ppm, respectively) in Sri Lanka. The absence of pollution-sensitive EPT taxa and the presence of pollution-tolerant Glycera sp., Pomacea sp. Helisoma sp. etc. in sediment indicated moderate pollution at sites. Results showed urban setup has affected aquatic pollution levels in Kirala Kale wetland.
