Microplastics Reflecting Water Quality Degradation in a Sediment-Laden Urban River of India

Microplastics (MPs) have emerged as significant indicators of anthropogenic pressure and deteriorating water quality in riverine systems. This study investigates the interrelationship between microplastic abundance and key physico-chemical parameters of the Yamuna River to elucidate how hydrochemical conditions influence MP distribution along the Delhi stretch. Water samples were analyzed for pH, dissolved oxygen (DO), electrical conductivity (EC), total dissolved solids (TDSs), and salinity, and the correlations were assessed. Strong negative correlations between pH and both EC (r = –0.99) and TDS (r = –0.99) reveal that acidic conditions correspond to higher ionic concentrations, likely resulting from untreated industrial effluents and urban runoff. A positive correlation between pH and DO (r = 0.88) indicates relatively cleaner and photosynthetically active regions within the river. In contrast, MP abundance exhibited strong positive correlations with EC (r = 0.95) and TDS (r = 0.94), but negative correlations with pH (r = –0.96) and DO (r = –0.81), suggesting greater accumulation of MPs in low-oxygen, high-ionic-strength waters. A moderate positive correlation with salinity (r = 0.68) further suggests enhanced deposition of MPs in sediment-laden and low-flow zones. The results collectively demonstrate that microplastic occurrence in the Yamuna River is closely governed by hydrochemical dynamics, reflecting complex interactions between pollution inputs and physical transport processes. Thus, microplastics can serve as effective indicators of water quality degradation, underscoring the need for integrated monitoring frameworks that couple conventional hydrochemical assessments with emerging contaminant analyses for sustainable river restoration.