analysis of dense non-aqueous phase liquid contaminants effects on soil permeability by response surface methodology

Soil contamination is considered a controversial issue in most countries. nowadays, it is important to clearly understand how pollutants influence the soil from different sources. today, hydrocarbons are one of the most important sources of soil contaminants, which is considered as a fundamental issue at the global level. the current study aims to analyze and model the effect ofsimultaneous parameters (time and concentration) of phenols and naphthalene with differentpercentages (10, 15, 20 and 25%) together with the amount of bentonite in fine-grained sandysoil. the designed experiments made use of response surface methodology (rsm) and design-expert software to carry out a computer-based simulation. according to the proposed model, theamount of bentonite is most affected by the permeability of the soil. the obtained results alsoshowed that the permeability significantly decreases in the light of increasing the percentage ofphenol and naphthalene coupled with the amount of bentonite and the age of contamination. onaverage, an 80% reduction of permeability was observed in contaminated soil, which was foundin the soil contaminated with naphthalene. according to the results of the synergistic effects oftime, the considerable impacts of both the percentage of hydrocarbon pollutants and the amountof bentonite on the reduction of permeability are quite evident.