The specific interaction between a strongly hydrophobic but still water-soluble cellulose derivative, ethyl(hydroxyethy1)cellulose (EHEC), and a low molecular weight anionic surfactant, sodium dodecyl sulfate (SDS), is studied in dilute solution without added neutral electrolyte by means of hydrodynamic (viscosity) and thermodynamic (dialysis equilibrium) measurements. The dialysis equilibrium shows strong adsorption of SDS at concentrations far below the normal cmc for SDS. The dialysis equilibrium is sensitive to the polymer concentration at higher SDS concentrations where the adsorption seems to decrease. In the region of increasing adsorption of SDS to EHEC the hydrodynamic measurements reveal a drastic reconformation of the polymer in dilute solution leading to a 4-fold reduction in hydrodynamic volume. At higher polymer concentrations the viscosity passes through a very marked maximum when the SDS concentration is increased. The results are interpreted in terms of a clustering theory for the SDS adsorption.

Groundwater is an important source for drinking water supply in hard rock terrain of Bundelkhand massif particularly in District Mahoba, Uttar Pradesh, India. An attempt has been made in this work to understand the suitability of groundwater for human consumption. The parameters like pH, electrical conductivity, total dissolved solids, alkalinity, total hardness, calcium, magnesium, sodium, potassium, bicarbonate, sulfate, chloride, fluoride, nitrate, copper, manganese, silver, zinc, iron and nickel were analysed to estimate the groundwater quality. The water quality index (WQI) has been applied to categorize the water quality viz: excellent, good, poor, etc. which is quite useful to infer the quality of water to the people and policy makers in the concerned area. The WQI in the study area ranges from 4.75 to 115.93. The overall WQI in the study area indicates that the groundwater is safe and potable except few localized pockets in Charkhari and Jaitpur Blocks. The Hill-Piper Trilinear diagram reveals that the groundwater of the study area falls under Na+-Cl−, mixed Ca2+-Mg2+-Cl− and Ca2+-$${\text{HCO}}_{3}^{ - }$$ HCO 3 - types. The granite-gneiss contains orthoclase feldspar and biotite minerals which after weathering yields bicarbonate and chloride rich groundwater. The correlation matrix has been created and analysed to observe their significant impetus on the assessment of groundwater quality. The current study suggests that the groundwater of the area under deteriorated water quality needs treatment before consumption and also to be protected from the perils of geogenic/anthropogenic contamination.

This article deals with a systematic hydrochemical study carried out in coastal aquifers, Tuticorin, Tamil Nadu, to assess groundwater quality. A total of 29 groundwater samples were collected and analyzed. Results showed that total dissolved solids (TDS), sodium (Na+), magnesium (Mg2+), chloride (Cl-), and sulfate (SO₄²⁻) significantly damaged groundwater systems. The degree of salinization due to seawater mixing in a well or a given area could be indicated by an increase in nearly all major cations and anions. Toxic elements (i.e., Pb and As) were higher than the maximum permissible limits of drinking water. Cross plot of HCO₃⁻/Cl- (molar ratios) versus TDS indicated that about 62% of the analyzed samples were saline. Factor analysis showed that groundwaters, affected by seawater intrusion/industrial activity, were separated from the clusters. An attempt was made to identify the hydrochemical processes that accompany current intrusion of seawater using ionic changes. It was estimated that the mixing rate of seawater intrusion was about 5.81% during April 2007. An index, called 'Seawater Mixing Index' (SMI), was also adopted and its value was SMI>1.18 with EC>3,000 μS/cm about 62% of the sampled waters, were saline. Further, a few trace elements (i.e., Sr, B, and Li) were used as indicators for responding to the change in fresh to saline groundwater environments in coastal aquifers.

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