No abstract

Underground coal gasification (UCG) generates potential groundwater pollution because it changes local hydrogeological parameters. Groundwater pollution is caused by diffusion and penetration of contaminants generated by UCG processes towards surrounding strata and possible leaching of residue by natural groundwater flow after gasification. A large number of hazardous water-borne contaminants were identified during different UCG operations conducted so far, and in some locations long-term groundwater contaminations were observed. Organic pollutants were detected after UCG process are phenols, benzene with its derivatives, polycyclic aromatic hydrocarbons (PAHs), heterocycles etc. and inorganic pollutants includes ammonia, mercury, zinc, sulphates, cyanides, heavy metals etc. Adsorption function of coal and surrounding strata makes a significant contribution to decrease the contaminants over time and distance from the burn cavity. Possible pollution control measures regarding UCG include identifying unsuitable zone, sitting a hydraulic barrier and pumping contaminated water out for surface disposal. The paper enumerates major pollutants identified in different UCG sites and its mitigation measures during gasification processes, and groundwater remediation after gasification.

Charcoal  produced from plant matter and stored in the soil as a means of removing carbon dioxide from the atmosphere. The purpose of this research was to study the impact of biochar application on soil pH and chemical properties in both acidic and neutral soils. Three types of biochar were used in a greenhouse experiment: 1) red gram straw biochar produced at 400°C, 2) pongamia fruit husk biochar produced at 500°C, 3) Calophyllum fruit husk biochar produced at 500°C, and a control in which neither of the biochar was used. Each treatment was applied with four levels of 4t/ha,8t/ha.12t/ha and 16t/ha biochars. Each treatment was replicated five times and whole experiment set up was done in factorial CRD (Completely randomised design). Two-way ANOVA was also used to analyze the impact of the biochars on soil acidity and other chemical properties. The results showed the application of biochar increased the soil pH in both soils. The increase in pH was more noticeable in acidic soil. In acidic soil calophyllum fruit husk biochar produced at 500 °C applied at 16t/ha showed highest pH at all intervals except at 120 days. The increase in pH in neutral soil doesn’t show any particular pattern throughout the incubation period. In acidic soil exchangeable bases such as Ca, Mg, K and Na were highest in red gram straw produced at 400°C. In both acidic and neutral soils, there was no definite trend in micronutrient contents such as extractible Mn, Fe, Zn, and Cu. The incorporation of biochar can cause beneficial changes in soil chemical properties and improve the bioavailability of plant essential nutrients.