Chemistry of Nitrate Contamination: A Multivariate Assessment of Drinking‑Water Quality across Major Cities of Pakistan

Abstract

Nitrate contamination in drinking water is a growing environmental and public‑health concern in Pakistan, where agricultural intensification, inadequate wastewater management, and rapid urbanization contribute to elevated nitrate levels in groundwater. This study assessed nitrate (NO₃⁻) concentrations across sixteen major cities using 718 water samples collected from hand pumps, tube wells, and municipal supplies. Nitrate levels showed substantial spatial and intra‑city variability, with several cities—particularly Bahawalpur, Kasur, Quetta, and Lahore—exceeding international drinking‑water guidelines. Descriptive statistics highlighted wide differences between minimum and maximum concentrations, indicating heterogeneous contamination sources. Principal Component Analysis (PCA) revealed that mean and maximum nitrate values were the dominant contributors to overall variability, while spatial mapping identified clear contamination hotspots in agricultural and densely populated regions. The combined analytical approach demonstrates that nitrate pollution in Pakistan is influenced by both agricultural and urban pressures. These findings emphasize the need for improved monitoring, sustainable fertilizer practices, and strengthened water‑quality management to protect public health.