Sequential Supercritical Fluid Extraction (SSFE) for Estimating the Availability of High Molecular Weight Polycyclic Aromatic Hydrocarbons in Historically Polluted Soils

Abstract

Sequential supercritical fluid (CO2) extraction (SSFE) was applied to eight historically contaminated soils from diverse sources with the aim to elucidate the sorption-desorption behavior of high molecular weight polycyclic aromatic hydrocarbons (PAHs). The method involved five extraction phases applying successively harsher conditions by increasing fluid temperature and density mobilizing target compounds from different soil particle sites. Two groups of soils were identified based on readily desorbing (available) PAH fractions obtained under mildest extraction conditions (e.g., readily desorbing fractions of fluoranthene and pyrene significantly varied between the soils ranging from <10 to >90%). Moreover, extraction behavior strongly correlated with molecular weight revealing decreasing available PAH fractions with increasing weight. Physicochemical soil parameters such as particle size distribution and organic dry mass were found to have no distinct effect on the sorption-desorption behavior of PAHs in the different soils. However, PAH profiles significantly correlated with readily available pollutant fractions; soils with relatively less mobile PAHs had higher proportions of five- and six-ring PAHs and vice versa. Eventually, biodegradability corresponded well with PAH recoveries under the two mildest extraction phases. However, a quantitative relationship was only established for soils with biodegradable PAHs. Out of eight soils, five showed no biodegradation including the four soils with the lowest fraction of readily desorbing PAHs. Only one soil (which was found to be highly toxic to Vibrio fischeri) did not match the overall pattern showing no PAH biodegradability but large fractions of highly mobile PAHs, concluding that mass transfer limitations may only be one of many factors governing biodegradability of PAHs.

Integrative approaches for assessing the ecological sustainability ofin situbioremediation

“…Further, recent studies for efficient pollutant extraction are targeting the physico‐chemical nature (hydrophobicity, soil adsorption, aqueous solubility, etc.) of the pollutant(s) for developing the efficient extraction methods (Szolar et al , 2004). The other common method for pollutant extraction focuses on the use of selective binding abilities to develop affinity chromatography‐based extraction of chemical pollutants (Stevenson, 2000; Liu & Ding, 2001; Tudorache & Emneus, 2006).…”

Potential of preliminary test methods to predict biodegradation performance of petroleum hydrocarbons in soil

“…To overcome nutrient depletion and to establish similar experimental conditions, a mineral medium was added as previously described by Szolar et al (2003). Suspension flasks were incubated at 20°C in the dark and analysed for residual hydrocarbons at day 0, 5, 9, 16, 23, 40 and 61.…”

Data evaluation of tar oil degradation using comprehensive GC2/ MS: individual compounds and principal component analysis

“… c The EPA PAHs were quantified using HPLC/3d‐FLD and DAD as described in Szolar et al (2004) and Scherr et al (2009) 27, 28…”

“…To all degradation tests, 10 µL of an enriched mixed consortium from different PAH‐contaminated soils, activated sludge and compost residues mixed culture was added. The mixed culture enrichment procedure is described in Szolar et al 27…”