Measuring nonpolar organic contaminant partitioning in three Norwegian sediments using polyethylene passive samplers.
ABSTRACT Freely dissolved pore water concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), penta- and hexachlorobenzene (PeCB and HCB), octachlorostyrene (OCS), p,p'-DDE and p,p'-DDD were measured in bottom sediments from three sites in Norway. Sediments were from Aker Brygge, site of a former shipyard in the inner part of Oslofjord, Frierfjord in the Grenlandsfjord area, impacted during the 50 year-long activity of a magnesium smelter plant, and from Kristiansand harbour, site with high industrial activity. Low density polyethylene (LDPE) membrane samplers were exposed to these sediments in laboratory incubation under constant and low-level agitation for periods of 1, 2, 6, 13, 23 and 50 days. Freely dissolved pore water concentrations were estimated from contaminant masses accumulated and sampling rates obtained from the measurement of kinetics of dissipation of performance reference compounds (PRCs). Marked differences in freely dissolved PAH concentrations and resulting organic carbon-normalised sediment-pore water partition coefficients, logK(TOC), between these three sediments could be observed despite the generally similar total sediment concentrations. In contrast with the PAH data, partitioning of PCBs and other organochlorine compounds (OCs) was relatively similar in all three sediments. For sediments from Frierfjord and Kristiansand, logK(TOC) values were lower for PCBs/OCs than for PAHs, indicating higher availability. Similar partitioning of PAHs and PCBs/OCs was found for sediments from Aker Brygge. No simple logK(oc)-logK(ow) relationships could model these data successfully. These results support the notion that the assessment of the risk posed by these compounds present in sediments in most cases requires actual measurement of contaminant availability.
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ABSTRACT: The effectiveness of many bioremediation systems for PAH-contaminated soil may be constrained by low contaminant bioaccessibility due to limited aqueous solubility or large sorption capacity. Information on the extent to which PAHs can be readily biodegraded is of vital importance in the decision whether or not to remediate a contaminated soil. In the present study the rate-limiting factors in methyl-β-cyclodextrin (MCD)-enhanced bioremediation of PAH-contaminated soil were evaluated. MCD amendment at 10 % (w/w) combined with inoculation with the PAH-degrading bacterium Paracoccus sp. strain HPD-2 produced maximum removal of total PAHs of up to 35 %. The desorption of PAHs from contaminated soil was determined before and after 32 weeks of bioremediation. 10 % (w/w) MCD amendment (M2) increased the Tenax extraction of total PAHs from 12 to 30 % and promoted degradation by up to 26 % compared to 6 % in the control. However, the percentage of Tenax extraction for total PAHs was much larger than that of degradation. Thus, in the control and M2 treatment it is likely that during the initial phase the bioaccessibility of PAHs is high and biodegradation rates may be limited by microbial processes. On the other hand, when the soil was inoculated with the PAH-degrading bacterium (CKB and MB2), the slowly and very slowly desorbing fractions (F sl and F vl ) became larger and the rate constants of slow and very slow desorption (k sl and k vl ) became extremely small after bioremediation, suggesting that desorption is likely rate limiting during the second, slow phase of biotransformation. These results have practical implications for site risk assessment and cleanup strategies.Biodegradation 24(3). · 2.17 Impact Factor