Physiologically based in vitro methods have been developed to measure bioaccessibility of organic contaminants in soils. However, bioaccessibility of hydrophobic organic contaminants (HOCs) can be underestimated by in vitro tests if gastrointestinal (GI) solution fails to provide sufficient sorption sink for HOCs. To circumvent this drawback, Tenax was included in GI solution as sorption sink to trap mobilized HOCs and maintain the desorption gradient between soil and GI solution. Polycyclic aromatic hydrocarbons (PAHs) were selected as target HOCs, and physiologically based extraction test (PBET) was selected as the in vitro method. Inclusion of Tenax in GI solution increased bioaccessibility of PAHs in five spiked soils from 8.25–20.8% to 55.7–65.9% and the bioaccessibility of PAHs in a field contaminated soil from 3.70–6.92% to 16.3–31.0%. Our results demonstrated the effectiveness of Tenax as sorption sink to enhance PAH mobilization in bioaccessibility measurement in soils.

In this study, reusable poly(alkoxysilane) organogels with high absorption capacities were synthesized by the condensation of a cyclo aliphatic glycol (UNOXOL™) and altering the chain length of the alkyltriethoxysilanes. The structural and thermal properties of cross-linked poly(alkoxysilane) polymers were determined by FTIR, solid-state 13C and 29Si CPMAS NMR and TGA. The oil absorbency of poly(alkoxysilane)s was determined through oil absorption tests, absorption and desorption kinetics. Results showed that the highest oil absorbency capacities were found to be 295% for hexane, 389% for euro diesel, 428% for crude oil, 652% for gasoline, 792% for benzene, 792% for toluene, 868% for tetrahydrofuran, and 1060% for dichloromethane for the poly(alkoxysilane) gels based on UNOXOL™ and dodecyltriethoxysilane. Owing to their hydrophobic structure, the poly(alkoxysilane) organogels can selectively absorb crude oil from water. The reusability of the absorbents was quantitatively investigated, demonstrating that absorbents can be used effectively at least nine times.

Solid Phase Microextraction (SPME) was applied to provide the first large scale dataset of freely dissolved concentrations for 9 polycyclic aromatic hydrocarbons (PAHs) in Baltic Sea sediment cores. Polydimethylsiloxane (PDMS) coated glass fibers were used for ex-situ equilibrium sampling followed by automated thermal desorption and GC–MS analysis. From the PAH concentrations in the fiber coating we examined (i) spatially resolved freely dissolved PAH concentrations (Cfree); (ii) baseline toxicity potential on the basis of chemical activities (a); (iii) site specific mixture compositions; (iv) diffusion gradients at the sediment water interface and within the sediment cores and (v) site specific distribution ratios. Contamination levels were low in the northern Baltic Sea, moderate to elevated in the Baltic Proper and highest in the Gulf of Finland. Chemical activities were well below levels expected to cause narcosis to benthos organisms. The SPME method is a very sensitive tool that opens new possibilities for studying the PAHs at trace levels in marine environments.

This work investigated effects of a prototype oil dispersant on solubilization, sorption and desorption of three model PAHs in sediment–seawater systems. Increasing dispersant dosage linearly enhanced solubility for all PAHs. Conversely, the dispersant enhanced the sediment uptake of the PAHs, and induced significant desorption hysteresis. Such contrasting effects (adsolubilization vs. solubilization) of dispersant were found dependent of the dispersant concentration and PAH hydrophobicity. The dual-mode models adequately simulated the sorption kinetics and isotherms, and quantified dispersant-enhanced PAH uptake. Sorption of naphthalene and 1-methylnaphthalene by sediment positively correlated with uptake of the dispersant, while sorption of pyrene dropped sharply when the dispersant exceeded its critical micelle concentration (CMC). The deepwater conditions diminished the dispersant effects on solubilization, but enhanced uptake of the PAHs, albeit sorption of the dispersant was lowered. The information may aid in understanding roles of dispersants on distribution, fate and transport of petroleum PAHs in marine systems.

Semi–volatile polycyclic aromatic hydrocarbons (PAHs) and their oxygenated analogues (OPAHs) are associated with adverse health effects. They are normally sampled by active sampling but recently a number of passive samplers that rely on calibrated sampling rates (Rs), have successfully captured the full suite of PAHs associated with both the gas–and particulate phases. However, there have been few studies on the mechanisms controlling particle deposition during passive sampling. To address this issue, a diesel exhaust aerosol with a number mode of ~120 nm containing PAHs and OPAHs that are partitioned approximately equally between the gas and particle phases was used to study the performance of a passive sampler design of axial badge type. The sampler was tested with two different collection substrates and the diffusion distance was varied to determine its effects on sample collection. The results obtained were compared to data gathered by active sampling of the gas and particle phases. In addition, Rs values were calculated for selected PAHs and OPAHs. The material collected by the passive samplers was analyzed using a highly sensitive protocol involving thermal desorption followed by GC–MS. The passive sampler yielded highly reproducible Rs values and its PAH uptake was shown to be enhanced by using a collection substrate modified with a gas–adsorbing coating (Tenax®) which was exclusively addressed being uptake from the gaseous phase. However, the uptake of the less volatile OPAHs was not affected by the use of a coated substrate. Experimental data and theoretical calculations showed that particle diffusion may have substantially less impact on particulate matter collection than other deposition mechanisms. The high sensitivity and small size of the sampler suggest that after testing in other environments it may have diverse applications in sampling campaigns and as a promising candidate for a personal sampler.

The objective of this study was to investigate the chemisorption mechanisms of Cu(II) on alcohol functionalized carbon nanotubes (OH-CNT) compared to granulated activated carbon (F-400). Two different sizes of OH-CNT were used on both adsorption isotherm experiments and continuous-flow fixed-bed columns. The experiments were conducted as a function of adsorbent type with fixed bed height (5 cm), fixed flow rate (0.035 mL/min), and one initial Cu(II) concentration (10 mg/L) at pH 5.1 and room temperature. Isotherm curves follow Freundlich model with better adsorption capacity for OH-CNT (6.3 and 15.7 mg/g) compared to F-400 (6.0 mg/g). Breakthrough curves for all adsorbents were typical, while OH-CNT showed higher capacity to treat water per amount of adsorbent than F-400. After 5 days of desorption, there was very little Cu(II) leached from the OH-CNT column as compared to F-400 that slowly desorbed 85 % of Cu(II). These results indicated chemisorption process on OH-CNT with low residual release of Cu(II) from adsorbent after reaching saturation. A systematic correlation method using converted FTIR absorbance curves (first derivative analysis) of as-received and hybrid OH-CNT identified new peaks on the spectra for Cu(II) chemisorbed on CNT surface, showing that Cu(II) target acidic functional groups during adsorption.

Cr interactions with TiO₂were systematically studied using batch and spectroscopic investigations. Sorption of chromium on TiO₂at pH 4.5 increases with increasing Cr concentration. The sorption of Cr(III) is in good agreement with Langmuir isotherm model, whereas that of Cr(VI) is better accounted for by the Freundlich model. At pH 7.0, however, the uptake of Cr(III) by TiO₂is over 95 %, while the extent of Cr(VI) sorption on TiO₂is much less than that of pH 4.5. These results are consistent with SEM observations showing that precipitates of Cr(III) are dominant under neutral pH. The sorption of Cr(VI) on TiO₂decreases with increasing pH. However, Cr(VI) sorption decreases with increasing ionic strength below pH 4.5 whereas the sorption increases with ionic strength above pH 4.5. These observations suggest that Cr(VI) sorption is sensitive to ionic strength, and Cr(VI) could form weakly bound adsorption complexes at the TiO₂–water interface. Phosphate competes with Cr(VI) for TiO₂surface sites during sorption processes, and Cr(VI) desorption accelerates and increases in the presence of phosphate. It is noted that the reduction of Cr(VI) is induced by sunlight on the TiO₂surface, but not detected in acidic solution throughout batch experiments at pH ≥ 4.5 for 24 h.

The carbon rich material obtained from pyrolysis process, i.e. biochar, has been widely discussed during the last decade due to its utilisation as a soil amendment. Furthermore, there is an unsolved question of biomass disposal from phytoremediation technologies. The idea of contaminated biomass pyrolysis has appeared, but there is lack of information about possible biochar utilisation obtained by this process. The aim of our study was to observe sorption properties of biochar prepared from contaminated biomass and release of contaminants from biochar back into the environment. The biomass of fast growing trees and maize was harvested on a site significantly damaged by risk element contamination (Cd, Pb and Zn). Plant biomass was pyrolysed and then the batch (de)sorption experiments were settled. The results confirmed no significant differences in metal sorption ability between biochars prepared from contaminated and uncontaminated biomass under the same conditions. The trend of maximum sorption capacity of observed matrices followed the order: wood biochar + soil (WB + soil) > wood uncontaminated biochar + soil (WUB + soil) > maize biochar + soil (MB + soil) > soil for cadmium, WB + soil > WUB + soil > soil for lead and MB + soil > WUB + soil > WB + soil > soil for zinc. Despite of increase of Zn desorption from wood biochars, maximum sorption capacity of the final WB + soil system was comparable to the WUB+soil sample. Our laboratory experiments showed high potential of biochar from contaminated plants as a soil amendment with sorption abilities and minimal risk of metal release.

A series of column experiments was conducted to evaluate the effect of organic carbon fraction on long-term atrazine elution tailing for calcareous soil (foc = 0.97 %) and calcareous soil with 10 % by weight terra rossa amendment (foc = 1.20 %). Effluent atrazine concentrations were monitored for approximately 400 pore volume to understand the influence of controlling sorption–desorption kinetics on long-term tailing behavior. Laboratory studies showed that the sorption of atrazine was described by rate-limited, nonlinear reversible processes for both soils. Atrazine transport exhibited extensive elution tailing for all experiments due to the presence of hard carbon components such as black carbon and kerogen in both soils. This nonlinear sorption and extensive atrazine tailing behavior were more pronounced and extensive for soil with terra rossa amendment due to the addition of approximately 20 % organic carbon including 10 % hard carbon components from terra rossa soil. A mathematical model incorporating nonlinear, rate-limited sorption/desorption described by a continuous distribution function was used to successfully simulate atrazine transport early-time breakthrough and long-term concentration tailing for both porous media.

The reversible and resistant components of adsorption and desorption of munition constituents (MCs) on soils was studied to determine the environmental fate of these contaminants. The long-term desorption of MCs has applicability in formulating accurate risk assessments for operational military ranges. Batch experiments near 1:1 (w/v) soil-to-solution ratios reflecting field conditions using solutions containing mixtures of HMX, RDX, and nitroglycerine (NG) were conducted. The three soils used varied from 0.04 to 13.3 % organic matter. The experiment involved one adsorption step followed by four consecutive desorption steps. Adsorption times were 2, 5, 10, and 30 days. For each adsorption time, desorption times were carried out for 1, 12, 24 and 72 h and 30 days. The reversible/resistant component model was applied to the data. The model predicted the desorption concentrations of the MCs in the soil with root mean square errors of approximately 0.05 to 0.2 μg g soil⁻¹. The extent of desorption hysteresis is not changed by the length of desorption time, irrespective of the initial adsorption time.