Aa. Ansari et al., Role of monsoon rain on concentrations and dispersion patterns of metal pollutants in sediments and soils of the Ganga Plain, India, ENVIR GEOL, 39(3-4), 2000, pp. 221-237
Monsoon rain causes large scale sediment-water movement and reworking of se
diments of the Ganga Plain which is one of the largest fluvial systems on E
arth. Geomorphology and drainage type combined with sedimentation processes
play a substantial role on dispersion and transport patterns of metals bou
nd to sediments and soils. The study area of Kanpur-Unnao industrial region
in the Ganga Plain has been divided into five independent geochemical doma
ins on the basis of sediment-geomorphic, hydrological and geochemical chara
cters. The monsoon hydrography and physicochemical parameters (pH, conducti
vity) of the river and urban drain waters play a prominent role in regulati
ng the concentrations and behaviour of the metals in the aquatic system of
the Ganga Plain. Values of pH and specific electrical conductivity of the r
iver water of the study area decrease whereas those of the urban drain wate
r increase in post-monsoon period. The monsoon rain reduces the contents of
Co, C-org, Cr, Fe and Ni and enhances the contents of Cd, Sn and Zn in sed
iments of post-monsoon period. In soils, it reduces the contents of Al, Co,
Fe, Mn and Ni and enhances the contents of Cd, Sn and Zn in the post-monso
on period. These changes in concentrations vary from metal to metal and fro
m one geochemical domain to the other. An increase in the concentrations of
few metals in the soils from pre- to post-monsoon periods indicates that t
hese metals were mobilized tents of Al, Co, Fe, Mn and Ni and enhances the
metal to metal and from one geochemical domain to the other. An increase in
the concentrations of from the overflooding of metal rich waste-water onto
the fields during high water stage and also by reworking of the soils thro
ugh sheet floods during the monsoon time. Despite the changes in concentrat
ions, metal dispersion patterns in each domain remain similar both in pre-
and post-monsoon periods which indicate that the geochemical and sediment-g
eomorphic processes operating for the metal and mobilization in sediments a
re persistent even after large scale sediment-water movement and reworking
of the sediments during the monsoon period.