A study for evaluation of contaminant transport characteristics through fine-grained soil.

Transport of soluble toxic substances through porous media lead to some significant geoenvironmental problems, for example, leachate migration from municipal and industrial solid waste resulting from unregulated disposal. Advection, dispersion, diffusion, and decay are reported to be the principal mechanisms in such phenomena. Geotechnical properties of the soil also play a significant role in this deterioration. In the present study, laboratory tests were conducted to formulate an appropriate method for assessment of migration of metal ions, such as nickel, through the soil. Relevant kinetic and process parameters, such as aquifer data, surface area, dielectric constant, pH of zero point charge (pHzpc), and permeability were also studied. One-dimensional mathematical modeling was used to describe the dynamics of the process. The present investigation was carried out at an ash pond site of a thermal power plant situated in West Bengal, India.     

Breakthrough adsorption study of migratory nickel in fine-grained soil.

The present study was conducted to evaluate the breakthrough curve for nickel adsorption in fine-grained soil from a nearby ash pond site of a thermal power plant. Nickel was found to be the major polluting solute in the ash sluicing wastewater. The adsorption of nickel by vertical soil column batch test and horizontal migration test was carried out in the laboratory. Field investigation was conducted also, by installing test wells around the ash pond site. Experimental results showed a good adsorptive capacity of soil for nickel ions. The breakthrough curves showed a reasonable fitting with a one-dimensional mathematical model. The breakthrough curves yielded from field test results showed good agreement with a two-dimensional mathematical model.     

Physico-chemical and bacteriological investigation on the River Torsa of North Bengal

A few physico-chemical and bacteriological parameters on certain locations of the river Torsa was studied. The major characteristics of Torsa river water were high alkalinity, high concentration of free ammonia with respect to albuminoid ammonia and the presence of bacteria of fecal origin. Marked seasonal variations of the parameters were also observed.     

Development of Zinc Oxide Sensors for Detecting Ammonia Gas in the Ambient Air: A Critical Short Review

Ammonia (NH₃) is emitted into the atmosphere by various industries and other sources and causes environmental pollution. Considering the hazards of ammonia, detecting leakage from vessels and pipes demands the use of sensors. Therefore, the development of NH₃ gas sensors assumes considerable importance to researchers and regulators and to industry, businesses, and facilities that make, store, or use ammonia. The use of metal oxide sensors (MOS) for detecting NH₃ gas, such as zinc oxide (ZnO), has been a topic of interest to researchers seeking methods to detect NH₃ gas, even at low concentrations. In this article, an attempt has been made to review the research thus far published on the synthesis of ZnO‐based NH₃ gas sensor materials, their characterization, and analyses of their performance. Finally, we make several recommendations regarding the scope of future research. For example, the kinetics of the sensor materials should be determined. Furthermore, extensive studies of gas–solid (NH₃–ZnO) adsorption are proposed to ascertain the exact adsorption mechanism in terms of isotherm, kinetics, and diffusive mass transport, and to determine “reversibility” and “recovery” of sensor materials so they can continue sensing and activating alarms when necessary for practical applications.     

Mobility of spiromesifen in packed soil columns under laboratory conditions

On percolating water equivalent to 1,156 mm of rainfall, spiromesifen formulation did not leach out of 25-cm long columns, and 62.7 % of this was recovered in 5–10-cm soil depth. In columns treated with the analytical grade, 52.40 % of the recovered spiromesifen was confined to 0–5-cm soil depth, with 0.04 % in leachate fraction, suggesting high adsorption in soil. Results revealed that percolating 400 mL of water, residues of enol metabolite of spiromesifen was detected up to 20–25-cm soil layer, with 23.50 % residues of spiromesifen in this layer and 1.73 % in the leachate fraction indicating that metabolite is more mobile as compared to the parent compound. Results suggested a significant reduction in leaching losses of enol metabolite in amended soil columns with 5 % nano clay, farmyard manure (FYM), and vermicompost. No enol spiromesifen was recovered in the leachate in columns amended with nano clay, vermicompost, and FYM; however, 85.30, 70.5, and 65.40 %, respectively, was recovered from 0–5 cm-soil depth of column after percolating water equivalent to 1,156 mm of rainfall. Spiromesifen formulation is less mobile in sandy loam soil than analytical grade spiromesifen. The metabolite, enol spiromesifen, is relatively more mobile than the parent compound and may leach into groundwater. The study suggested that amendments were very effective in reducing the downward mobility of enol metabolite in soil column. Further, it resulted in greater retention of enol metabolite in the amendment application zone.