I samhallet genereras kontinuerligt olika material som genom sitt fosforinnehallkan vara lampat som godning for akermark eller i andra omraden. Denna rapportpresenterar en litteraturgenomgang av vi ...

The retention and mobility of hydrophobic organic contaminants (HOCs) in soil is mainly determined by hydrophobic partitioning to dissolved and particulate organic matter (DOM and POM, respectively). The aqueous phase, DOM, and POM fractions were extracted and separated from soils at three sites contaminated with technical chlorophenol formulations. Concentrations of chlorophenols (CP), polychlorinated phenoxyphenols (PCPP), polychlorinated diphenyl ethers (PCDE) and polychlorinated dibenzo-p-dioxins and furans (PCDD/F) were determined. The partitioning to POM, in relation to DOM, increased in all three soils with increasing hydrophobicity in the order CP < PCPP ~ PCDE ~ PCDF < PCDD. Differences in partitioning to DOM (logK(DOC)) and POM (logK(POC)) could not be explained by differences in gross organic C chemistry. Black carbon did not contribute significantly to the sorption of PCDDs, whereas >70% wood fibre in one soil resulted in a decrease of logK(POC) of 0.5 units for CPs and PCDDs. We conclude that logK(OC) for both DOM and POM need to be explicitly determined when the retention and mobility of HOCs is described and modelled in soils.

This paper summarizes recent studies on the environmental fate of chloroaromatic compounds in chlorophenol (CP)-contaminated soil and groundwater at Swedish sawmill sites. Relative proportions of CPs, polychlorinated phenoxy phenols (PCPPs), polychlorinated diphenyl ethers (PCDEs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) were determined in preservatives, particulate organic matter (POM), dissolved organic matter (DOM), groundwater, and particles filtered from groundwater. All compound classes were found in the different compartments. The fraction of PCPPs, PCDEs, PCDDs, and PCDFs had increased in the soil samples relative to the proportions in the preservatives. This increase showed correlation with the hydrophobicity, that is, PCDDs had the largest increase. Similar correlation was found between hydrophobicity and the importance of partitioning to POM over DOM. The more water soluble compound group, CP, was found equally distributed between POM and DOM. For PCPPs, PCDEs, PCDDs, and PCDFs, the relative partitioning to POM increased with increased hydrophobicity. Despite the relative partitioning towards POM, compared with DOM, cotransport with DOM and suspended colloidal fractions was found to substantially increase the transport of these compounds in the groundwater samples.

In this study, we investigated how the chemical degradability of polycyclic aromatic hydrocarbons (PAHs) in aged soil samples from various contaminated sites is influenced by soil characteristics and by PAH physico-chemical properties. The results were evaluated using the multivariate statistical tool, partial least squares projections to latent structures (PLS). The PAH-contaminated soil samples were characterised (by pH, conductivity, organic matter content, oxide content, particle size, specific surface area, and the time elapsed since the contamination events, i.e. age), and subjected to relatively mild, slurry-phase Fenton's reaction conditions. In general, low molecular weight PAHs were degraded to a greater extent than large, highly hydrophobic variants. Anthracene, benzo(a)pyrene, and pyrene were more susceptible to degradation than other, structurally similar, PAHs; an effect attributed to the known susceptibility of these compounds to reactions with hydroxyl radicals. The presence of organic matter and the specific surface area of the soil were clearly negatively correlated with the degradation of bi- and tri-cyclic PAHs, whereas the amount of degraded organic matter correlated positively with the degradation of PAHs with five or six fused rings. This was explained by enhanced availability of the larger PAHs, which were released from the organic matter as it degraded. Our study shows that sorption of PAHs is influenced by a combination of soil characteristics and physico-chemical properties of individual PAHs. Multivariate statistical tools have great potential for assessing the relative importance of these parameters.

We determined the distribution of hydrophobic organic contaminants (HOCs) to fractions of natural organic matter in a soil contaminated by chlorophenol wood preservatives more than 30 years ago. The concentration of dissolved organic matter (DOM) was enhanced in soil suspensions by raising pH to 6.8-9.1. After 48 h of desorption/equilibration, the DOM fraction was separated from the particulate organic matter (POM) of the soil by filtration. In the next step, DOM was flocculated by Al-nitrate, and free concentrations of HOCs were determined in the aqueous phase. The HOCs associated with DOM and POM were extracted with toluene. No significant differences in gross carbon chemistry were detected between DOM and POM, using X-ray photoelectron spectroscopy (XPS). Normalized to organic C, chlorophenols (CPs) showed a similar degree of partitioning between DOM and POM, whereas the partitioning of polychlorinated diphenyl ethers (PCDEs), polychlorinated dibenzo-p-dioxins, and furans (PCDD/Fs) was highly shifted toward POM. The partitioning to POM, relative to DOM, increased in the order PCDE < PCDF < PCDD, reflecting the hydrophobicity of the compounds.

To make proper risk assessments of sites with contaminated soil it’s important to understand the biogeochemical processes determining transport and sequestration of the contaminants in soil. Soil organic matter (SOM) is the most important component in soil for adsorption of hydrophobic organic compounds (HOC) and the organic carbon normalized partitioning constant (KOC) is used to model partitioning of HOCs between the aqueous phase and SOM. The aqueous solubility of HOCs is low and association to dissolved organic matter (DOM) in soil solution is therefore important for the mobility of HOCs. Similarly, association to the solid phase of SOM, in this thesis denoted particulate organic matter (POM), controls the retention of HOCs in organic rich soils. Few data are reported on the partitioning of HOCs to DOM (KDOC) and to POM (KPOC) determined in the same equilibrium system. In short-term adsorption experiments with controlled equilibrium systems, adsorption to DOM and POM was best described by linear isotherms for chlorophenols (CPs) and nitrobenzene (NB), indicative of a hydrophobic partitioning mechanism. Adsorption of aniline was best described by the Langmuir isotherm, indicative of a specific interaction to functional groups of DOM and POM. Trinitrotoluene (TNT) adsorption data revealed specific interactions of degradation products to DOM and hydrophobic partitioning of TNT to POM. As a complement to the short-term adsorption experiments, soils with aged contaminants were investigated. Chlorophenols (CP), phenoxy phenols (PCPP), diphenyl ethers (PCDE), dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) associated to DOM and POM and the free analyte in the aqueous phase were determined. In both the adsorption experiments and the soils with aged contaminants, POM showed a higher binding affinity towards HOCs than DOM, when normalized to organic carbon content. The partitioning towards POM, relative to DOM, increased with increasing hydrophobicity of the classes of compound studied in the order CP

Summary We determined the sorption of 2,4‐dichlorophenol (DCP), 2,4,5‐trichlorophenol (TCP) and pentachlorophenol (PCP) to dissolved (DOM) and particulate soil organic matter (POM) from the same soil in controlled equilibrium systems, using 14 C‐labelled chlorophenols in combination with reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and liquid scintillation. Associations of DCP, TCP and PCP to DOM and POM were satisfactorily described by linear adsorption isotherms. Together with the absence of substantial competition between DCP and TCP for binding sites, this indicates a hydrophobic partitioning mechanism. The organic carbon normalized partitioning coefficient ( K OC ) for the binding of DCP was similar in magnitude for POM ( K POC ) and for DOM ( K DOC ), whereas K POC for the more hydrophobic compounds TCP and PCP were approximately one order of magnitude greater than K DOC . On the basis of the relationships between log K OC and the organic carbon normalized partitioning coefficient (log K OW ), the extent of association to POM increases more with the hydrophobicity of the chlorophenol than the extent of association to DOM. This holds for our data obtained for DOM and POM of similar origin, as well as for various sources of POM and DOM reported in the literature. Differences in the magnitude of K POC and K DOC in our study could not be accounted for by differences in gross carbon chemistry of POM and DOM, as determined by nuclear magnetic resonance ( 13 C‐NMR) and X‐ray photoelectron spectroscopy (XPS). Thus, other factors such as the average size and capacity of hydrophobic moieties could explain differences in chlorophenol association between POM and DOM. We conclude that K POC and K DOC need to be determined explicitly, when the transport and retention of chlorophenols is modelled, and not calculated from relationships between log K OC and log K OW .

Surveys of dioxins and related compounds focused on identification and quantification of sources in Sweden show that a major reservoir of dioxins is connected to the use of chlorophenol (CP) based wood preservatives (1,2). In Sweden, CP preservatives have been used at approximately 400 – 500 sawmill sites. The total accumulated amount of dioxins at these sawmill sites, expressed as toxic equivalents (TEQs), is estimated to be in the range of 2-50 kg TEQ (1). Today, soil at these sites are contaminated not only with CPs, but also with by-products in the technical formulations, viz. polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), diphenyl ethers (PCDEs) and phenoxy phenols (PCPPs) (See Figure 1).

The distribution of TNT* (the sum of TNT and its degradation products), aniline, and nitrobenzene between particulate organic matter (POM), dissolved soil organic matter (DOM), and free compound was studied in controlled kinetic (with and without irradiation) and equilibrium experiments with mixtures of POM and DOM reflecting natural situations in organic rich soils. The binding of TNT* to POM was fast, independent of irradiation, and adsorption isotherms had a great linear contribution (as determined by a mixed model), indicative of a hydrophobic partitioning mechanism. The binding of TNT* to DOM was slower, strongly enhanced under nonirradiated conditions, and adsorption isotherms were highly nonlinear, indicative of a specific interaction between TNT derivatives and functional groups of DOM. Nitrobenzene was associated to both POM and DOM via hydrophobic partitioning, whereas aniline binding was dominated by specific binding to POM and DOM functional groups. On the basis of nitrobenzene and TNT* adsorption parameters determined by a mixed Langmuir + linear model, POM had 2-3 times greater density of hydrophobic moieties as compared to DOM. This difference was reflected by a greater (O + N)/C atomic ratio for DOM. The sum of C-C and C-H moieties, as determined by X-ray photoelectron spectroscopy (XPS), and the sum of aryl-C and alkyl-C, as determined by solid-state cross-polarization magic-angle spinning (CP-MAS) (13)C NMR, could only qualitatively account for differences in adsorption parameters. Aliphatic C was found to be more important for the hydrophobic partitioning than aromatic C. On the basis of nonlinear adsorption parameters,the density of functional groups reactive with aniline and TNT derivatives was 1.3-1.4 times greater in DOM than in POM, which was in fair agreement with 13C NMR and XPS data for the sum of carboxyl and carbonyl groups as potential sites for electrostatic and covalent bonding. We conclude that in contaminated soils characterized by continuous leaching of DOM, formation of TNT derivatives (via biotic and abiotic reductive degradation) and their preference for specific functional groups in DOM may contribute to a significant transportation of potentially toxic TNT compounds into surface waters and groundwaters.