Variations of the Physicochemical Parameters and Metal Levels and Their Risk Assessment in Urbanized Bagmati River, Kathmandu, Nepal

Abstract

During post-monsoon 2013, surface water samples were collected form 34 sites from the Bagmati River and its tributaries within the Kathmandu Valley to assess the river water quality. The physical parameters were measured on site and major ions (Na+,NH4+, K+, Mg2+, Ca2+, Cl−,SO42-, andNO3-) and 17 elements in water were analyzed in the laboratory. Conductivity ranged from 21.92 to 846 μS/cm, while turbidity ranged from 2.52 to 223 NTU and dissolved oxygen (DO) ranged from 0.04 to 8.98 mg/L. The ionic and elemental concentrations were higher in the lower section where the population density is high compared to the headwaters. The large input of wastewater and organic load created anoxic condition by consuming dissolved oxygen along the lower belt of the river. The concentration of the elements was found to be in the order of Mn > Zn > Ti > Rb > Cr > Cu > Sc > Ni > V > Li > Co > Mo > Cd > Y > Ga > Be > Nb. The concentration of Mn, Cd, Cr, Co, and Zn was particularly higher in urban and semiurban sections. Enrichment factor (EF) calculations for Cd, Co, and Zn showed their highly enriched values indicating that these elements originated from anthropogenic sources. Preliminary risk assessments were determined by the hazard quotient (HQ) calculations in order to evaluate the health risk of the metals. TheHQingestionvalues of elements were found to be in the order Sb > Mn > Cr > V > Co > Cd > Cu > Zn > Ni > Li > Mo with all averaged HQ values less than 1, indicating no or limited health risk of metals from the river to the local residence. However the values of Sb in some parts of the Bagmati were close to unity indicating its possible threat. Anthropogenic activities like industrial activities, municipal waste water, and road construction besides the river appear to control the chemical constituent of the river water. Overall the river was highly polluted with elevated concentrations of major ions and elements and there is a need for restoration projects.

Physicochemical and Bacteriological Analysis of Bagmati River in Kathmandu Valley

“…Higher values recorded at sites downstream to B 3 can be linked with variation in inputs of organic matter associated with population density and activities. Poudyal et al also presented an increasing trend from headwaters to semi urban to urban section along the river; the average TDS recorded was 42.06 ppm, 130.10 ppm and 240.15 ppm respectively [14].…”

Heavy Metal Assessment of Kavre Valley Basin River System

“…Therefore, continuous monitoring of the water resources must be made. Similar studies have been conducted in Kathmandu, Nepal for Bagmati river system (Kayastha 2015;Paudyal et al 2016), but previous water body related studies in Kavre have only highlighted organic pollutants and none have focused on heavy metal pollution, which is also a major environmental and health concern.…”

Hydrochemical assessment of the Beeshazar and associated lakes in Central Nepal

“…Results showed that the mean value of DO was found in the order of Kingfisher > Kumal > Tikauli > Laxmi > Beeshazaar. The higher value of DO in the water designates the better water quality, thus, the aforementioned order of the lakes also characterizes the spatial water quality variations in the lake complex [35]. Similarly, the mean Cl − values of different lakes were reported in the order of Laxmi > Kingfisher > Tikauli > Kumal > Beeshazar.…”