Importance of geomorphology and sedimentation processes for metal dispersion in sediments and soils of the Ganga Plain: identification of geochemicaldomains

The Ganga Plain, one of the largest alluvial plains of the earth is under s evere environmental stress due to rapid industrial and urban development an d exploding population growth. Disposal of industrial and urban wastes and the ignorance of their management have resulted severe environmental proble ms, especially metal pollution. In the present study, an attempt is made to understand the transport and dispersion processes of metal contaminants in sediments and soils in Kanpur-Unnao industrial region of the Ganga Plain. The significance of geomorphology and monsoon rain is assessed in determini ng the distribution of contaminated sediments in this area. Three regional geomorphic surfaces (T-0, T-1 and T-2) are identified, each with its charac teristic river channel patterns and sediment distribution system which infl uence the dispersion and accumulation of the metal contaminants. The sedime nt and water distribution regime depends on the nature of geomorphic featur es and character of the river channels. Geomorphic features, sedimentation processes, the nature of the river channels and distribution of excess rain water of the monsoon season have given the bases to delineate five geochem ical domains in the study area. Each geochemical domain is an independently operating system with its own geomorphic and geochemical characters. Chemi cal parameters (e.g., pH), metal concentrations, and dispersion of metal-co ntaminated sediments and soils vary from domain to domain. In comparison to reference values, each domain exhibits its own enrichment of elements, nam ely the Loni River domain has high contents of C-org, Cd, Cr, Zn; the Ganda Nala domain of C-org, Cu, Cr; the Ganga River domain of C-org, Cr, Cu, Pb, Sn, Zn; the Sewage Network domain of C-org, Cd, Cr, Cu, Pb, Ni, Sn, Zn; an d the Pandu River domain of C-org, Cd, Cu, Ni, Zn. Patterns of changes in m etal concentrations from one monsoon year to the other and in different sea sons of a monsoon flood cycle are also domain specific. Each geochemical do main exhibits its own degree of metal enrichment in sediments and soils by anthropogenic activities and physico-chemical processes. Identification of geochemical domains with their specific physico-chemical processes in the f luvial system of the Ganga Plain will certainly help in assessing the envir onmental problems and land contamination of this region. (C) 2000 Elsevier Science B.V. All rights reserved.