Kuldip SinghJyoti2020-12-282020-12-282020Jyoti (2020). Geochemical assessment and remediation of arsenic in south-western Punjab (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810157436Geochemistry and assessment of arsenic (As) in groundwater and soil is an important factor for effective management of the groundwater resource. One hundred twenty groundwater samples, 60 soil samples and 120 paddy straw samples were collected from southern-western districts of Punjab, India: Mansa, Muktsar and Bathinda, during pre- and post-monsoon seasons. Significant and positive correlations were observed between As and RSC content of groundwater in premonsoon season. The paddy straw As content was positively and significantly correlated with As, RSC, redox of groundwater, total and available As content in soil. The available As was significantly and positively correlated with total soil As content. A laboratory investigation was carried out to examine the mechanism of As mobilization under flooded conditions (24 and 240 h) in 10 alluvial soils. Total dissolved As increased from a range of 3.14–16.14 µg l-1 (mean 8.95 µg l-1) to a range of 34.2–1768 µg l-1 (mean 871.5 µg l-1) with the increase in flooding period from 24 to 240 h. The amount of As mobilization varied depending upon redox potential (pe) created by flooding conditions. After 24 h of flooded conditions, pe of soil-water suspension ranged from 2.11 to -0.64 (mean -1.25), whereas, it decreased in the range of -5.23 to -2.55 (mean -3.52) after 240 h of flooding. A loamy sand and a clay soil were used to study adsorption behaviour of arsenate (AsV) by equilibrating soil with range of added concentration (50-2500 mg AsV kg-1 soil) in presence of background electrolyte 0.01 M NaNO3, under two temperatures (278 0K and 308 0 K) and two solution pH (5 and 8.5). Arsenate adsorption was found to increase with increase in temperature as well as with decrease in solution pH, however, amount of AsV adsorbed was relatively higher in clay soil as compared to loamy sand soil. Arsenate adsorption was highest at solution pH 5, 308 0K and lowest in solution pH 8.5, 278 0K, irrespective of soil. Arsenate adsorption data were well described by Langmuir and Freundlich isotherms. To study effect of added anions on AsV adsorption, at each added AsV concentration, 1000 mg anion kg-1 soil was also added. The addition of anions reduced the amount of AsV addition at both temperatures and pH in two soils in the order: phosphate > silicate > sulphate > bicarbonate. For removal of AsV from groundwater, effectiveness of iron-coated sand and iron-coated strips was investigated. Ironcoated strips were found to have relatively higher capacity to remove AsV as compared to ironcoated sand. To study kinetics of AsV adsorption by loamy sand soil, clay soil, iron-coated sand and iron-coated strips, the data were fitted to four kinetic models: Pseudo-first order, pseudosecond order, elovich and intra-particle diffusion models. Among these four kinetic models pseudo-second order gave best fit with high R2 value as well as lower error.EnglishThesis