Chapter 22 - Time series analysis of dissolved trace elements in Gomati River, the Ganga River tributary, northern India: its environmental implications

Abstract

The distribution of dissolved metals (Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Zr, Mo, Cd, and Pb) was investigated in the water of the 900-km long Gomati River (the Ganga River tributary). Thirty-six time-series samples were collected from May 2009 to June 2010, covering the monsoon, post-monsoon, winter, and summer seasons. Trace elements concentration varies in the eighth order of magnitude from 0.005ng/L (Zr) to 77.861µg/L (Al). Also, the extreme monsoon-controlled hydrological event had a noticeable effect on dissolved trace elements concentration, confirming the dominance of biogeochemical factors in determining dissolved trace metals concentrations. Most dissolved metals have a significant (increase in one to three orders of magnitude) single positive anomaly, corresponding seasonality with the river’s high flood-water discharge. However, significant inter-elemental correlation coefficients of metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn Rb, and Pb) appear to be predominantly derived from biotite mica, which recommends the importance of chemical weathering processes of mica-rich alluvial sediments under the sub-tropical climatic condition. With an annual quantity of 5.9×109m3 water discharge from 30,437km2 draining area of the Ganga Alluvial Plain, the river transports about 90% of its metallic elements flux during the monsoon and the post-monsoon seasons. The Gomati River Basin acts as a natural laboratory to study the influence of monsoon climate and biotite mica weathering on river water chemistry in the sub-tropical region.