Application of chemical mass balance to upstream downstream river monitoring data

The river Kali in western Uttar Pradesh (India) has been heavily influenced by the discharge of untreated municipal, agricultural, and industrial effluents. In the main channel of the river, the metal contamination was found to be three to four times the background level. The concentration of iron, zinc, and copper was 0.41, 0.04, and 0.015 mg l(-1), respectively, in the upstream section during October. The same were 0.56, 0.07, and 0.016 mg l(-1), during December. Comparisons between upstream and downstream monitoring sites reveal changes in the concentration and/or load to the river and can be used to discriminate between point and non-point sources of pollution for these elements in the river. The resulting differential loadings, if adjusted for uncharacterized non-point contribution to the load, may represent the total point source load to the river minus any losses due to volatilization, settling, and/or degradation. Mass balance calculations conducted for iron, zinc, and copper indicated that additional inputs are needed to account for the observed differences in load along the river. The sources may include non-point sources of pollution due to agricultural activities, sediment remobilization or entrainment, groundwater intrusion or from a combination of these sources. The difference may also be attributed to some point sources of pollution which could not be identified in the course of investigations.