title: Fate of cadmium at the soil-solution interface: a thermodynamic study as influenced by varying pH at South 24 Parganas, West Bengal, India.
abstract: A study on the sorption kinetics of Cd from soil solution to soils was conducted to assess the persistence of Cd in soil solution as it is related to the leaching, bioavailability, and potential toxicity of Cd. The kinetics of Cd sorption on two non-contaminated alkaline soils from Canning (22° 18' 48.02″ N and 88° 39' 29.0″ E) and Lakshmikantapur (22° 06' 16.61″ N and 88° 19' 08.66″ E) of South 24 Parganas, West Bengal, India, were studied using conventional batch experiment. The variable soil suspension parameters were pH (4.00, 6.00, 8.18, and 9.00), temperatures (308, 318, and 328 K) and Cd concentrations (5-100 mg L(-1)). The average rate coefficient (kavg) and half-life (t1/2) values indicate that the persistence of Cd in soil solution is influenced by both temperature and soil suspension pH. The concentration of Cd in soil solution decreases with increase of temperature; therefore, Cd sorption on the soil-solution interface is an endothermic one. Higher pH decreases the t 1/2 of Cd in soil solution, indicating that higher pH (alkaline) is not a serious concern in Cd toxicity than lower pH (acidic). Based on the energy of activation (Ea) values, Cd sorption in acidic pH (14.76±0.29 to 64.45±4.50 kJ mol(-1)) is a surface control phenomenon and in alkaline pH (9.33±0.09 to 44.60±2.01 kJ mol(-1)) is a diffusion control phenomenon The enthalpy of activation (ΔH∓) values were found to be between 7.28 and 61.73 kJ mol(-1). Additionally, higher positive energy of activation (ΔG∓) values (46.82±2.01 to 94.47±2.36 kJ mol(-1)) suggested that there is an energy barrier for product formation.
authors.affiliation: Department of Agricultural Chemistry and Soil Science, Faculty of Agriculture, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal, 741252, India. tanmay.karak@gmail.com.|Upper Assam Advisory Centre, Tea Research Association, Dikom, Dibrugarh, Assam, 786101, India. tanmay.karak@gmail.com.
authors.forename: Tanmoy
authors.initials: T
authors.lastname: Karak
authors.affiliation: Division of Statistical Genetics, Indian Agricultural Statistics Research Institute, New Delhi, 110012, India. ranjitstat@gmail.com.
authors.forename: Ranjit Kumar
authors.initials: RK
authors.lastname: Paul
authors.affiliation: Dibrugarh Polytechnic, Lahowal, Dibrugarh, Assam, 786010, India.
authors.forename: Sampa
authors.initials: S
authors.lastname: Das
authors.affiliation: Department of Agricultural Chemistry and Soil Science, Faculty of Agriculture, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal, 741252, India.
authors.forename: Dilip K
authors.initials: DK
authors.lastname: Das
authors.affiliation: Upper Assam Advisory Centre, Tea Research Association, Dikom, Dibrugarh, Assam, 786101, India.
authors.forename: Amrit Kumar
authors.initials: AK
authors.lastname: Dutta
authors.affiliation: Upper Assam Advisory Centre, Tea Research Association, Dikom, Dibrugarh, Assam, 786101, India.
authors.forename: Romesh K
authors.initials: RK
authors.lastname: Boruah
mesh_terms: D000327:Adsorption; D002104:Cadmium / Q000032:analysis* / Q000737:chemistry; D004058:Diffusion; D004784:Environmental Monitoring; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D007194:India; D007700:Kinetics; D008956:Models, Chemical; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry; D012996:Solutions; D013696:Temperature; D013816:Thermodynamics
chemical_list: D012987:Soil; D012989:Soil Pollutants; D012996:Solutions; D002104:Cadmium
keywords: Enthalpy; Entisols; Entropy; Free energy; Half-life; Sorption