Begum et al. 2023 — Water quality and heavy metals in Rawal Lake tributaries, Pakistan
This study applies principal component analysis (PCA) and a Water Quality Index (WQI) to evaluate spatial variation in water quality across the five major tributaries feeding Rawal Lake, Islamabad, the primary drinking water source for the twin cities of Islamabad and Rawalpindi (population approximately 2 million). Among the 11 water quality parameters assessed, temperature, TDS, pH, EC, chlorides, and sulfates were within WHO limits at most sites; however, cadmium (Cd) and lead (Pb) exceeded WHO permissible limits specifically in the Bari Imam and Rumli tributaries. Pearson correlation analysis revealed a strong positive correlation (r = 0.910, p less than 0.05) between Pb and Cd concentrations, suggesting co-sourcing from common anthropogenic inputs. PCA yielded three factors explaining 96.5 percent of total variance. The WQI classified water in Bari Imam and Rumli tributaries as highly contaminated and unsuitable for drinking. Contamination sources at Bari Imam include high population density, household waste dumping, and car wash activities; at Rumli, agricultural and grassland runoff are implicated.
Key numbers
Cd and Pb exceeded WHO limits in Bari Imam and Rumli tributaries (specific concentration values not extracted from tables in this read). Strong Pearson correlation between Pb and Cd: r = 0.910 (p less than 0.05). PCA: three factors explained 96.5% of total variance; Factor 1 loadings for pH, TDS, alkalinity, chlorides, sulfates, zinc (all greater than 0.60). Heavy metals analysed by AAS (Perkin-Elmer Analyst 300) after acid digestion with concentrated nitric acid. Metals measured: Pb, Cr, Cd, Zn, Cu. Sampling conducted three times over three months (March, May, July), 12 random samples per site per month.
Methods (brief)
Grab sampling from five tributaries; acid digestion with nitric acid, AAS analysis. PCA with XLSTAT on 10 variables across 5 sites and 3 months. Pearson correlation (SPSS v13). WQI calculated using weighted relative importance of 11 parameters. Limitation: small temporal window (3 months, one season); no speciation of Cd or Pb forms; total metals only.
Implications
Certification: Relevant to the drinking water exposure framing and to the risk that urban water-to-irrigation pathways can transfer Cd and Pb to food crops in periurban Pakistan.
Courses: Useful illustration of how a WQI integrates multiple parameters into a single actionable metric and how heavy metals can be the binding constraint even when most other parameters are acceptable.
App: Not directly applicable to food concentration data; provides drinking water context for Pakistani supply chains.
Microbiome: Not addressed.