Kinetics of sorption of lead on bed sediments of River Hindon, India.

A number of low cost waste sorbent have been used for removal of heavy metals, however, few studies have been carried out on the sorption process on riverbed sediments in their natural state of occurrence. Stream sediments adsorb certain solutes from streams, thereby significantly changing the solute composition, but little is known about quantitatively describing sorption phenomena and rates of these processes. In the present investigation, sorption of lead ions on river bed sediments of river Hindon, a tributary of river Yamuna, India has been studied to demonstrate the role of bed sediments in controlling metal pollution. The effect of various operating variables, viz., initial concentration, solution pH, sediment dose, contact time and particle size has been studied. The sorption of lead ions increased with respect to pH and sorbent dose and decreased with sorbent particle size. Two important geochemical phases, iron and manganese oxide, also play important role in the sorption process. The sorption data were analysed using Langmuir and Freundlich isotherm models to determine the mechanistic parameters related to the sorption process. Further, although lead ions have more affinity for the fine fraction of the sediment, but the overall contribution of coarser fraction to sorption is more as compared to clay and silt fraction. The kinetic data suggest that the sorption of lead on bed sediments is an endothermic process, which is spontaneous at low temperature. The uptake of lead is controlled by both bulk and intraparticle diffusion mechanism.

Adsorption of zinc on bed sediment of River Hindon: adsorption models and kinetics.

The paper presents a study of zinc adsorption using the experimental data on bed sediments of River Hindon in western Uttar Pradesh (India). The effect of various operating variables, viz., initial concentration, solution pH, sediment dose, contact time, and particle size, have been studied. The optimum contact time needed to reach equilibrium was of the order of 60 min and was independent of initial concentration of zinc ions. The extent of adsorption increased with an increase of pH. Furthermore the adsorption of zinc increases with increasing adsorbent doses and decreases with the adsorbent particle size. The content of iron, manganese and organic matter in various fraction of sediment decreases with increasing particle size indicating the possibility of the two geochemical phases to act as the active support material for the adsorption of zinc ions. The adsorption data follows both Langmuir and Freundlich adsorption models. Isotherms were used to determine thermodynamic parameters, viz., free energy change, enthalpy change and entropy change. The negative values of free energy change indicate spontaneous nature of the adsorption while positive values of enthalpy change suggest the endothermic nature of the adsorption of zinc on bed sediment of the River Hindon. The positive values of entropy change indicate randomness at the solid/solution interface.

Estimating nutrient loadings using chemical mass balance approach.

The river Hindon is one of the important tributaries of river Yamuna in western Uttar Pradesh (India) and carries pollution loads from various municipal and industrial units and surrounding agricultural areas. The main sources of pollution in the river include municipal wastes from Saharanpur, Muzaffarnagar and Ghaziabad urban areas and industrial effluents of sugar, pulp and paper, distilleries and other miscellaneous industries through tributaries as well as direct inputs. In this paper, chemical mass balance approach has been used to assess the contribution from non-point sources of pollution to the river. The river system has been divided into three stretches depending on the land use pattern. The contribution of point sources in the upper and lower stretches are 95 and 81% respectively of the total flow of the river while there is no point source input in the middle stretch. Mass balance calculations indicate that contribution of nitrate and phosphate from non-point sources amounts to 15.5 and 6.9% in the upper stretch and 13.1 and 16.6% in the lower stretch respectively. Observed differences in the load along the river may be attributed to uncharacterized sources of pollution due to agricultural activities, remobilization from or entrainment of contaminated bottom sediments, ground water contribution or a combination of these sources.

Metal pollution assessment of sediment and water in the River Hindon, India.

The metal pollution in water and sediment of the River Hindon in western Uttar Pradesh (India) was assessed for Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. The metal concentrations in water showed wide temporal variation compared with bed sediment because of variability in water discharge and variations in suspended solid loadings. Metal concentrations in bed sediments provided a better evaluation of the degree and the extent of contamination in the aquatic environment, Santagarh and Atali being the most polluted sites of the river. The ratio of heavy metals to conservative elements (Fe, Al, etc.) may reveal the geochemical imbalances due to the elevated metal concentrations normally attributed to anthropogenic sources. Metal/A1 ratios for the bed sediments of the river Hindon were used to determine the relative mobility and general trend of relative mobility occurred Fe > Mn > Zn > Cr > Ni > Pb > Cu > Cd.

Arsenic contamination in parts of Yamuna sub-basin, West Bengal.

Arsenic rarely occurs in free state and is generally found in combination with Sulphur, Oxygen and Iron. In the environment, Arsenic occurs as a result of several inputs that contain this element in organic and inorganic forms. Arsenic is present in Coal, Lead, Zinc, Gold and Copper ores in the form of several minerals viz. Arsenopyrite (FeAsS), Orpiment (As2S3), Realgar (AsS), Arsenolite (As2O3) and Lollingite (FeAs2). The commonly existing species in groundwater are in two forms viz. Arsenite [As(III)] which is the reduced state of inorganic Arsenic and Arsenate [As(V)], which is the oxidized state of inorganic Arsenic, The As(III) form is more mobile and toxic for living organisms. Recently, the symptoms of chronic arsenic poisoning have been observed in many parts of West Bengal (India) and Bangladesh. In the present study, an integrated evaluation of hydrogeology and hydrochemistry has been carried out by processing the available data of Yamuna sub-basin (Part of Nadia and North 24 Parganas district) of West Bengal in order to understand the possible reason of arsenic pollution in the ground water. Arsenic has generally been observed in higher concentration in shallow aquifer. Northwestern region of the study area has been observed to be the most effected with premonsoon periods exhibiting higher concentration. Transmissivity values have been observed to vary inversely with arsenic concentrations. Arsenic values have not indicated any well defined association with many other constituents. Arsenic buildup could also not be conclusively related to lowering of ground water table of the study area.