Investigating the possibility of using subcritical water for extracting polycyclic aromatic hydrocarbons from soils of the dry-steppe zone

Abstract

In the course of the model experiment, extraction conditions of 16 priority PAHs in subcritical water medium were selected for soils of the chestnut-solonetz complex. For low molecular weight 2-ringed naphthalene and 3-ringed acenaphthene, acenaphthylene, anthracene, phenanthrene and fluorene, the optimal extraction conditions correspond to 10 minutes at a temperature of 200°C. For high molecular weight 4- and 5-ring benz(a)anthracene, fluoranthene, pyrene, chrysene, benz(b)fluoranthene, benz(k)fluoranthene, dibenz(a,h)anthracene, as well as the pollutant of the first hazard class - benz(a)pyrene, the optimal extraction time reached 20 minutes at a temperature of 250°C. For 6-ring benz(g,h,i)perylene and indeno(1,2,3-cd)pyrene, the optimum extraction time increased to 30 minutes and the temperature to 300°C. When comparing the methods of extraction of pollutants from soils, it is shown that the extraction methods can be placed in the following descending order by the value of the extraction coefficient of priority PAHs from the studied types of soils: ultrasonic extraction (1.05) > subcritical extraction (1.13) > saponification method (1.25). Using multivariate analysis of dispersion it is shown that the efficiency of subcritical aqueous extraction decreases with increasing number of benzene rings in the PAH molecule, as well as with increasing soil salinity in the following order: Gleyic Kastanozems < Endosalic Kastanozems < Kastanozems Sodic < Solonets.