Assessment of Pollution Impact on Three Oligotrophic Lakes in a University and Evaluation of Nature Based Solutions for their Restoration

Abstract

Natural and anthropogenic pollution make freshwater lakes uninhabitable for biodiversity and pose a serious threat to humans. Regular monitoring is necessary to detect early signs of pollution for treatment. The present study aims to identify possible waste intrusion sources and evaluate pollutant levels in water, sediment and flora of 3 lakes located in NUST university, Islamabad. Samples were collected from 6 points (Lake 1 inlet (L1I), Lake 1 outlet (L1O), Lake 2 inlet (L2I), Lake 2 outlet (L2O), Lake 3 inlet (L3I) and Lake 3 outlet (L3O)). The average concentrations of physicochemical parameters (total kjeldahl nitrogen (TKN) (26.5-97.6 mg/L), electrical conductivity (EC) (570-1686 μS/cm), turbidity (24.6-90.2 NTU) and phosphate-phosphorus (PO4-P) (0.47-0.75 mg/L)) exceeded the WHO limits. Dissolved oxygen (DO) (1.9-3.2mg/L) levels indicated near hypoxic conditions toxic for lake biota. Average chlorophyll (Chl-a, b and c) concentrations (0.00007-0.0006 mg/L) showed oligotrophic lake conditions while leaf chlorophyll content index (CCI) (3.7-165.3) varied in lake flora with highest average concentration in Stellaria graminea. Dominant algae (Nitzschia sp., Navicula gregaria sp., and Euglena sp.) were identified under compound microscope. Heavy metal analysis (Lead (Pb), Cadmium (Cd), Chromium (Cr), Zinc (Zn)) of water, sediment and plant samples through atomic absorption spectrophotometer (AAS) showed high Zn concentrations (5.302 mg/kg) as compared to other metals. Seasonal parameters provided a baseline for long term meteorological analysis. Nature Based Solutions (NBS) like phytoremediation were identified to mitigate pollution. Principal component analysis (PCA) and Environmental Systems Research Institute (ESRI) ArcGIS Pro software were used for data analysis and visualization.