Dhanwinder SinghSatnam Kaur2019-08-302019-08-302019http://krishikosh.egranth.ac.in/handle/1/5810124928Sorption and desorption of chromium (VI) were examined on twenty eight surface and subsurface soil samples collected from four different locations viz Ludhiana, Jalandhar, Malerkotla and Mandi Gobindgarh. Sorption of Cr was carried in presence of background electrolyte 0.01 M Ca(NO3)2 solution. Sorbed Cr was desorbed back by resuspending the same soil samples in fresh Cr-free 0.01 M Ca(NO3)2 and giving five repeated washings sequentially. Chromium sorption was observed to be significantly and negatively correlated with pH both in surface (r = -0.764) and sub-surface samples (r = -0.757). Simple linear regression model for different soil variables showed that 58% and 57% of the variation in Cr sorption in the surface and sub-surface soils under study, respectively, was explained by soil pH. The stepwise multiple regression model showed that other factors, like total Cr and EC could marginally increase the variability to 68% in surface soils and OC to 61% in subsurface soils. The amounts and patterns of chromium desorbed varied among the soils. Chromium desorption was significantly and positively correlated with soil pH both in surface (r = 0.635) and sub-surface (r = 0.438) soil samples. Among polluted samples, 51% variability was explained by pH in surface samples and 80% variability in sub-surface samples by pH, EC and clay content. In non-polluted soils, CEC, CaCO3, DTPA extractable Cr and total Cr together explained 91% variability in Cr desorption in surface samples and OC, CEC and DTPA extractable Cr explained 66% variation in sub-surface samples. The Cr sorption data of the three selected soil samples were very well described by Langmuir adsorption isotherm (R2=0.959 to 0.994), Freundlich adsorption isotherms (R2= 0.985 to 0.994) and Dubinin–Radushkevich (D-R) adsorption isotherm (R2=0.926 to 0.973). The Cr desorption data of the soils well fitted to Langmuir desorption isotherm (R2= 0.967 to 0.992). Effect of pH on Cr sorption-desorption was also studied by adjusting the pH of each of three selected surface soil samples in the range of 6-8 in the laboratory. The sorption of chromium decreased with the increase in soil pH from 6 to 8. Chromium sorption data fitted well in Langmuir (R2= 0.924 to 0.995), Freundlich (R2= 0.977 to 0.995) and (D-R) (R2= 0.954 to 0.981) adsorption isotherm equations at all pH levels. Percent chromium desorbed increased with the increase in pH from 6 to 8.enThesis