Soot-Carbon Influenced Distribution of PCDD/Fs in the Marine Environment of the Grenlandsfjords, Norway

Abstract

The particle associations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) were studied in both the water column and the surface sediments of a marine fiord system and were found to poorly obey expectations from the organic matter partitioning (OMP) paradigm. The field observations were instead consistent with the presence of a stronger sorbent subdomain such as pyrogenic soot-carbon (SC) playing an important role in affecting the environmental distribution and fate of PCDD/Fs. Solid-water distribution coefficients (Kd) of PCDD/ Fs actually observed in the water column were several orders of magnitude above predictions from a commonly used OMP model. Even when these elevated Kd values were normalized to the particulate organic carbon (POC) content (i.e., K(OC)), the variability in K(OC) for individual PCDD/ Fs at different fjord locations and seasons of factors 100-1,000 suggested that bulk organic matter was not the governing sorbent domain of the suspended particles. Further, POC-normalized particle concentrations of PCDD/ Fs (C(OC)) in a vertical profile (surface water-bottom water-surface sediment) revealed a strong increasing trend with depth. Factors of about 100 higher Coc for all PCDD/Fs in the sediment than in the surface water could not be explained by higher fugacity in the surrounding deep water nor with C:N or delta13C indexes of selective aging of the bulk organic matter. Instead this was hypothesized to reflect selective preservation of a more recalcitrant and highly sorbing, but minor, subdomain such as soot. The extent of enhanced PCDD/F sorption, above the OMP predictions, was positively correlated with the SC:POC ratio of the suspended particles in surface and deep waters. Finally, the geographical distribution of sedimentary PCDD/F concentrations were better explained by the SC content than by the bulk OC content of the sediment. Altogether, these field-based findings add to recent laboratory-based sorption studies to suggest that we need to consider both amorphous OC partitioning domains and SC particles as carriers of planar aromatic contaminants if we are to explain the environmental distribution and fate of pollutants such as PCDD/Fs.

The factors controlling the partitioning of polybrominated diphenyl ethers and polychlorinated biphenyls in the water-column of the Pearl River Estuary in South China

“…Laboratory and field studies on the solid-water partitioning (K p ) of PAHs over the past decade in the marine and aquatic environment suggest that there is an order of magnitude higher affinity for the particulate phase than what was predicted empirically from bulk organic matter partitioning models (Vanhoof and Andren, 1991;Xiao et al, 2004). Elevated K p values have also been found for the solid-water partitioning of other aromatic compound classes, such as PCDD/Fs and PCBs (Persson et al, 2002). These results strongly suggest that the elevated K p for those HOCs can be attributed to an efficient interaction between HOCs and carbonaceous particles such as BC that possess highly aromatic and planar structural properties.…”

“…The binding of hydrophobic organic chemicals (HOCs) to DOC reduces the vertical diffusive exchange of HOCs in the water column as well as the bioavailability of HOCs in aquatic ecosystems (Persson et al, 2002). The colloidal-associated contaminants may be the dominant species in some surface waters.…”

“…It can compose a significant fraction (2-20%) of the total organic carbon in marine sediments (Gustafsson et al, 2001). Numerous investigations have performed the sorption of HOCs to BC using a variety of carbonaceous particles such as soot carbon and charcoal (Persson et al, 2002). Laboratory and field studies on the solid-water partitioning (K p ) of PAHs over the past decade in the marine and aquatic environment suggest that there is an order of magnitude higher affinity for the particulate phase than what was predicted empirically from bulk organic matter partitioning models (Vanhoof and Andren, 1991;Xiao et al, 2004).…”

Stability and carbon isotope changes of soot and char materials during thermal oxidation: Implication for quantification and source appointment

“…Among these tested methods, the chemothermal oxidation (CTO) method has gained much attention as operatively simple and reasonably accurate measurements for soot-BC in soils and sediments (Gustafsson et al, 1997(Gustafsson et al, , 2001Gélinas et al, 2001;Elmquist et al, 2004Elmquist et al, , 2006 and later also soot-BC in aerosols (Zencak et al, 2007;Gustafsson et al, 2009). For instance, the large-scale distribution of combustion-derived and sorptive PAHs in marine sediments have repeatedly been shown to be much better explained by CTO375-based BC than by bulk OC or any other parameter (e.g., Gustafsson and Gschwend, 1998;Persson et al, 2002;Oen et al, 2006;Sanchez-Garcia et al, 2010). The CTO method was systematically evaluated in two recent studies using four BC reference materials -two liquid fossil fuel soots (diesel soot and hexane soot) and two biomass chars (wood char and grass char) (Elmquist et al, 2006;Hammes et al, 2007).…”

Quantification of sedimentary black carbon using the chemothermal oxidation method: an evaluation of ex situ pretreatments and standard additions approaches

“…For instance, BC may be an important component of sedimentary carbon preservation (Goldberg 1985;Gustafsson and Gschwend 1998;Masiello and Druffel 1998;Dickens et al 2004) and thereby constitutes a valuable record of the global fire history (e.g., Bird and Cali 1998). Sorption of aromatic compounds to BC is 10 to 1000 times stronger than to nonpyrogenic sedimentary organic matter (e.g., Bucheli and Gustafsson 2000;Accardi-Dey and Gschwend 2002;Jonker and Koelmans 2002;Cornelissen and Gustafsson 2004) and frequently governs the environmental distribution of many organic pollutants (Gustafsson et al 1997;Gustafsson and Gschwend 1997;Dachs and Eisenreich 2000;Persson et al 2002;Ribes et al 2003). In the atmosphere, BC affects Earth's radiative heat balance (e.g., Jacobson 2001) and BC in urban air particles has been implicated as the culprit of epidemiological respiratory diseases and human deaths (Dockery et al 1993;Künzli et al 2000;Gerde et al 2001).…”