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Soil/air partition coefficients (K(SA)) were measured experimentally on a silty clay loam soil spiked with polychlorinated biphenyls (PCBs) over a wide range of environmentally relevant temperatures (-30 to +30 degrees C). Measured K(SA)-values ranged over 6.4 orders of magnitude, with log K(SA) from 4.3 for PCBs 10/4 at +30 degrees C to 10.7 for PCBs 77/110 at -30 degrees C. Higher than expected, K(SA)-values were observed at subzero temperatures (by up to one order of magnitude, at -30 degrees C). The plots of log K(SA) vs. reciprocal absolute temperature show a change in slope at 0 degrees C. A log-log linear regression of K(SA) vs. octanol/air partition coefficient (K(OA)) has a slope close to 1, indicating that K(OA) is a good descriptor of the interchemical variability in K(SA). Further study showed that K(OA)-based Karickhoff-type equations can perfectly fit experimental K(SA)-values.

The soil/air partition coefficients (K(SA)) for two polycyclic aromatic carbons (PAHs) and six organochlorine pesticides (OCs) were determined by a solid-phase fugacity meter over a wide temperature range of -30 to +30 degrees C in a paddy field soil. Literature values for PAHs and OCs obtained by the same method were 1.9-5.1 times of present values at +20 degrees C. Experimentally determined K(SA) ranged over six orders of magnitude, with log K(SA) from 4.5 for alpha-hexachlorocyclohexane at +30 degrees C to 10.4 for trans-nonachlor at -20 degrees C. Separate linear regressions of log K(SA) and reciprocal absolute temperature were employed at temperatures above 0 degrees C and below 0 degrees C. The calculated enthalpies associated with the phase transfer from the soil to the air (DeltaH(SA)) over 0 to +30 degrees C range from 78 to 108 kJmol(-1), which are in a good agreement with the literature values.

Enhancement of p,p'-DDT photodegradation on soil surfaces using TiO2 induced by UV-light was mainly investigated in this work. After being spiked with p,p'-DDT, soil samples loaded with different doses of TiO2 (0%, 0.5%, 1%, 2%, and 3% wt) were exposed to UV-light irradiation for 24 h. The results indicated that the photodegradation of p,p'-DDT followed the pseudo-first-order kinetics. TiO2 accelerated the photodegradation of p,p'-DDT significantly as indicated by the half-life reduction from 23.3 h to 10.4 h, corresponding to the TiO2 content from 0% to 3% respectively. In addition, the effects of soil pH, photon flux and humic substances on p,p'-DDT degradation were investigated. The photodegradation rate increased with the increase of the soil pH and photon flux. The humic substances (2% wt) inhibited the p,p'-DDT photodegradation by reducing the amount of light available to excite the p,p'-DDT and TiO2 or by quenching radicals capable of oxidizing p,p'-DDT. p,p'-DDE, p,p'-DDD and DDMU were main degradation intermediates and they were further degraded in the presence of TiO2.

Importance of environmental black carbon (BC) to sorption of dissolved petroleum hydrocarbons (DPH) on two soils with high BC:TOC ratios (33% and 11%, respectively) was evaluated at a relatively high concentrations (mg/L ∼ μ g/L range). Sorption isotherms of DPH were determined for the two original soils and soils combusted at 375°C (only BC). The sorption isotherms of the original soils were linear, whereas the isotherms of the combusted soils were highly nonlinear (nF = 0.45, 0.60). It is indicated that intrinsic BC-water sorption coefficient is not possible to be used to estimate total sorption to the original soil, even in our relatively high concentrations. From the sorption isotherms, Freundlich coefficient of environmental BC sorption, KF,BCenv of 102.55 ± 0.21 was calculated and could be used as a generic starting point for environmental modeling purposes. From the data, it could be deduced that BC was responsible for 50% of the total sorption at concentrations of 45 and 4 μ g/L (μ g/L range), which were significantly higher than literature concentrations (ng/L range). These results demonstrate that in soil with high BC:TOC ratio BC is the most important geosorbent constituent with respect to sorption of DPH at relatively high concentrations ranged in μ g/L. [ABSTRACT FROM AUTHOR]

Microwave-induced thermal treatment of the soil contaminated with petroleum hydrocarbon is explored with a model contaminant of diesel oil. The contaminated soil is treated in the microwave field of 2.45 GHz with addition of granular activated carbon (GAC), which is used as microwave absorber for achieving an appropriate temperature to decontaminate the soil. During the treatment, the oil removed from the soil matrix is recovered by a condensation system of ice-salt bath. Some process parameters, such as GAC dose, microwave power, treating time, moisture and sample mass, are investigated. It is shown that the contaminated soil can be treated by this microwave-induced thermal process such that more than 99% contaminant removal can be achieved within 10 min. The analysis performed on the recovered oil indicates that it does not change obviously in chemical composition and physical properties, compared with the original oil. [ABSTRACT FROM AUTHOR]