A Study on Contaminant Transport Through Soil

Abstract

Soil in ecosystem is contaminated by various environmental activities taking place in day-to-day life. Major contaminants in soil are chlorides, fluorides, nitrates, iron, silicates, etc. The present study deals with the transportation of contaminants like sodium chloride (Nacl) and sodium fluoride (NaF) in soil by advection–diffusion method. The tests are carried on soil mixed with varying percentages of sand from 10 to 40%. In the present study, the dosage of contaminants, i.e., Nacl and NaF, is varied from 0.1 N to 0.4 N, respectively. The column of size 60 cm is utilized, and up to 40 cm height, soil is compacted from the base. The solutions of additives are pumped at the rate of 0.208 ml/s. The time of flow at the entry and exit of soil column is observed, and solution is collected from the exit point to evaluate percentage absorption by the soil. For different normalities of sodium chloride such as 0.1 N, 0.2 N, 0.3 N, 0.4 N, corresponding relative concentrations obtained are 0.078, 0.073, 0.062, 0.056, and similarly, relative concentrations for sodium fluoride are also determined. The soil absorption capacity increases with increasing the concentration of contaminants. For all normalities of contaminants, the nature of results obtained follows the footprint of breakthrough curves. Strength parameter of contaminated soil is evaluated by unconfined compressive strength test. The strength of sodium chloride contaminated soil is increased irrespective of concentrations and decreased with increase in percentage addition of sand. The strength of sodium fluoride contaminated soil is decreased with longer curing period.