Heavy metal contamination of surface water and bed-sediment quality for ecological risk assessment of Gomti River, India

Sustainable river ecosystem is the fundamental backbone of all civilizations of the world. Water contamination through heavy metals and metalloids causes wide environmental and public discontent which makes it a global concern. With this view, 20 km stretch of Gomti River encompassing 5-locations was selected for determination of 16-physicochemical parameters and 11-heavy metals in water and bed-sediment samples during two consecutive years 2019-2020 covering three seasons supplemented by indices and statistics. Bed-sediment characterization was done through scanning electron microscope-energy dispersive X-rays and attenuated total reflection-Fourier transform infrared analysis. River is significantly contaminated with Fe, Mg, Mn, Zn, Pb, Cu, Ni, Cr, Co, Cd, Hg having corresponding mean values 10.1 +/- 1.8, 36.1 +/- 10.6, 23.4 +/- 8, 16.7 +/- 5.9, 8.4 +/- 3.2, 8.2 +/- 3.3, 0.002 +/- 0.001 lg/g in bed-sediment, respectively. Corresponding order of heavy metals concentration was Mg > Fe > Mn > Zn > Cr > Co > Cd > Ni > Pb > Cu > Hg and Fe > Mg > Mn > Zn > Pb > Cu > Ni > Cr > Co > Cd > Hg, respectively. Higher values of indices for risk quantification; geo-accumulation index (5.0), contamination factor (1191.8), enrichment factor (46.5) and potential ecological risk index (393.8) were found for Cd in bed-sediment samples. Principal component analysis (? > 1) scored 3-factors having 65%, 19% and 11% variance for water and 75%, 10% and 7% variance for bed-sediment samples. Strong positive correlations (= 0.8) were observed among Mn, Cd, Co, Cr, Pb, Cu for water and sediment samples. Study could be beneficial in providing knowledge regarding heavy metal induced ecological risk to aquatic organisms and suggest ways to reduce the burden of potential influx sources.