Sophia C. Johannessen

Large and growing environmental reservoirs of Deca-BDE present an emerging health risk for fish and marine mammals

Polybrominated diphenyl ethers (PBDEs) have been the subject of intense scientific and regulatory scrutiny during recent years. Of the three commercial forms (Penta, Octa and Deca) of PBDEs that have been widely used as flame retardants in textiles, furniture upholstery, plastics, and electronics, only Deca-BDE remains on the general market in North America, while a recent ruling of the European Court spells an impending end to its use in Europe. We review here highlights of aquatic research documenting the rapid emergence of PBDEs as a high priority environmental concern in Canada. PBDEs are being introduced in large quantities to the aquatic environment through sewage discharge and atmospheric deposition. In certain environmental compartments, the single congener BDE-209, the main ingredient in the Deca-BDE formulation, has surpassed the legacy PCBs and DDT as the top contaminant by concentration. Limited biomagnification of BDE-209 in aquatic food webs reflects its high log K(ow) and preferential partitioning into the particle phase. As a result, large environmental reservoirs of BDE-209 are being created in sediments, and these may present a long-term threat to biota: BDE-209 breaks down into more persistent, more bioaccumulative, more toxic, and more mobile PBDE congeners in the environment.

Joined by geochemistry, divided by history: PCBs and PBDEs in Strait of Georgia sediments.

Polychlorinated biphenyls (PCBs) are relict contaminants, while polybrominated diphenyl ethers (PBDEs) are in increasing use. Using sediment cores collected in the Strait of Georgia, we demonstrate that the surface sediment concentration of PCBs is largely determined by environmental processes, such as sediment accumulation and mixing rates, while that of PBDEs is strongly influenced by proximity to source. The Iona Island wastewater outfall appears to be a primary pathway for PBDEs. As well, Vancouver Harbour is highly contaminated with both classes of chemical. BDE-209, the main component of deca-BDE, is the dominant PBDE congener. Environmental debromination is not evident. Currently, the ranges of the surface concentration of PCBs and PBDEs are similar to one another, but that will change in the future, as the concentration of PBDEs continues to rise. The experience with PCBs suggests that if PBDEs were banned today, it would take decades for inorganic sediment to bury them.

Distribution and Cycling of Suspended Particles Inferred from Transmissivity in the Strait of Georgia, Haro Strait and Juan de Fuca Strait

Abstract Transmissometer profiles collected during quarterly cruises in 2000–03 indicate that most suspended particles in the Strait of Georgia and Juan de Fuca Strait are confined to the top and bottom of the water column. In Haro Strait, however, the particles are mixed throughout the water column by strong tidal currents, producing an estuarine turbidity maximum. The distribution and cycling of particles provide important aquatic controls for contaminant transport, photochemical reactions and photosynthesis. Particle‐associated contaminants that enter Haro Strait may remain in suspension and enter the food web at all water depths. In the autumn and sometimes in the summer, the rate of photochemical transformation of dissolved organic matter is probably higher in Juan de Fuca Strait than in the Strait of Georgia or Haro Strait, because the surface water in Juan de Fuca Strait is less turbid.

Environmental fractionation of PCBs and PBDEs during particle transport as recorded by sediments in coastal waters

The Strait of Georgia (British Columbia, Canada) is a hydrologically complex inland sea with a rich abundance and diversity of species of aquatic life. Marine sediments, as both a sink for hydrophobic contaminants and a potential source for aquatic food webs, were collected from 41 sites throughout the 6,900-km(2) Strait of Georgia. The congener-specific concentrations of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), including BDE-209, were measured. Urban harbors represented hotspots for both PCBs and PBDEs, whereas PBDEs were also found at high concentrations near municipal outfalls. Patterns of PCB distribution were consistent with historical point source emissions in urban areas and environmental distillation toward lighter profiles in remote sites over time. The single congener BDE-209 dominated the PBDEs, accounting for 52% of the average total concentration. However, nonurban deep-water sediment PBDE profiles were both heavier and had higher concentration-weighted average log K(OW) (octanol-water partition coefficient) values compared to shallow samples (percent BDE-209 of total PBDE, 66 versus 32%; log K(OW) , 9.5 versus 8.2, respectively). Collectively, our results suggest that although source signals largely explain PCB and PBDE hotspots in the Strait of Georgia, the combination of physicochemical properties and environmental processes drive divergent compositional fates for the PCBs and the heavier PBDEs in the sediments of the Strait of Georgia.

There is no 1954 in that core! Interpreting sedimentation rates and contaminant trends in marine sediment cores

Marine sediment preserves a useful archive for contaminants and other properties that associate with particles. However, biomixing of sediments can smear the record on a scale of years to thousands of years, depending on sedimentation rate and on the depth and vigour of mixing within a particular sediment. Where such mixing occurs, dates can no longer be associated with discrete sediment depths. Nevertheless, much can still be learned from biomixed profiles, provided that mixing is accounted for. With no modelling at all, it is possible to calculate an inventory of a contaminant at a site and a maximum possible sedimentation rate, and to determine whether the contaminant has increased or decreased over time. Radiodating the core with (210)Pb permits the estimation of sedimentation and mixing rates, which can be combined with the surface contaminant concentration to estimate an approximate flux of the contaminant. Numerical models that incorporate sedimentation and mixing rates (determined using (210)Pb and other transient signals with known deposition histories) can provide the basis to propose plausible histories for contaminant fluxes.

Responses of subtidal benthos of the Strait of Georgia, British Columbia, Canada to ambient sediment conditions and natural and anthropogenic depositions.

Patterns in infaunal biota in the Strait of Georgia are explored relative to water depth, substrate type, organic content of sediments and sedimentation characteristics. The analyses are based on geographically-diverse grab and core data collected over a 19-year period. Infaunal abundance and biomass were not predictable by sediment particle size, organic content or water depth. While organic flux was a reasonable predictor of biotic factors, quality of organic material, relative proportions of organic and inorganic input and source of inputs were also important in this regard. Areas with high accumulation of sediment and high organic flux rates from terrestrial (riverine) sources supported the highest macro-infaunal abundance and biomass found to date in the Strait of Georgia, and were dominated by bivalves. Polychaetes dominated in low organic deposition conditions, and where anthropogenic organic deposition was high. However, biota were severely impoverished in sediments with high organic content from marine deposition, due to low fluxes and poor quality of organic material. Taxa number was related to percent total nitrogen and to the ratio of organic/inorganic flux, both in background conditions and where there was labile organic enrichment. Faunal communities from the Fraser River delta, which experiences considerable bottom-transported riverine material, were very different in composition from those that proliferate in habitats with high deposition and organic flux from the water column.

Natural and anthropogenic mercury distribution in marine sediments from Hudson Bay, Canada.

Twelve marine sediment cores from Hudson Bay, Canada, were collected to investigate the response of sub-Arctic marine sediments to atmospherically transported anthropogenic mercury (Hg). Modeling by a two-layer sediment mixing model suggests that the historical Hg deposition to most of the sediment cores reflects the known history of atmospheric Hg deposition in North America, with an onset of increasing anthropogenic Hg emissions in the late 1800s and early 1900s and a reduction of Hg deposition in the mid- to late-1900s. However, although anthropogenic Hg has contributed to a ubiquitous increase in Hg concentrations in sediments over the industrial era, the most elevated industrial-era sedimentary Hg concentrations only marginally exceed the upper preindustrial sedimentary Hg concentrations. Analysis of delta13C and relationship between Hg and organic matter capture suggests that the response of Hudson Bay sediments to changes in atmospheric Hg emissions is largely controlled by the particle flux in the system and that natural changes in organic matter composition and dynamics can cause variation in sedimentary Hg concentrations at least to the same extent as those caused by increasing anthropogenic Hg emissions.

Sediment redox tracers in Strait of Georgia sediments--can they inform us of the loadings of organic carbon from municipal wastewater?

Organic carbon composition and redox element (Mn, Cd, U, Re, Mo, SigmaS, AVS) distributions are examined in seven 210Pb-dated box cores collected from the Strait of Georgia, British Columbia to evaluate the potential for redox elements to reveal impacts of anthropogenic loadings of labile organic carbon to sediments. In particular, the cores have been collected widely including regions far from local anthropogenic inputs and from locations within the zone of influence of two municipal outfalls where sediments are exposed to enhanced organic loadings from outfalls. We find a wide natural range in organic carbon forcing within the basin sediments generally reflected as Mn enrichments near the surface in cores exhibiting slow organic oxidation and sulphide, Cd, Mo, U and Re enrichments in cores exhibiting higher organic oxidation rates. Concentration profiles for redox elements or organic carbon are misleading by themselves, as they are influenced strongly by sediment porosity and sedimentation rate, and the organic matter remaining in sediment cores is predominantly recalcitrant. Fluxes of redox elements together with rates of organic metabolism estimated from sedimentation rates provide a better picture of the organic forcing. One core, GVRD-3, collected within the zone of influence of the Iona municipal outfall (0.5 km away), exhibits the highest organic carbon oxidation rates, enhanced Ag fluxes in the sediment surface mixed layer and altered delta15N composition, all of which implicate outfall particulates. Cd is also elevated in the GVRD-3 surface sediments, but evidence points to contamination and not redox forcing supporting this observation. Uranium also shows enrichment at sites near the outfalls, possibly in response to enhanced microbial metabolism. Predominantly these cores exhibit a wide natural range of organic carbon fluxes and organic carbon oxidation rates, supported by fluxes of marine and terrigenous organic carbon, within which it is difficult to identify any significant impact from municipal outfall organic carbon.

PBDE and PCB accumulation in benthos near marine wastewater outfalls: the role of sediment organic carbon.

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) were measured in sediments and benthic invertebrates near submarine municipal outfalls in Victoria and Vancouver, B.C., Canada, two areas with contrasting receiving environments. PBDE concentrations in wastewater exceeded those of the legacy PCBs by eight times at Vancouver and 35 times at Victoria. Total PBDE concentrations in benthic invertebrates were higher near Vancouver than Victoria, despite lower concentrations in sediments, and correlated with organic carbon-normalized concentrations in sediment. Principal Components Analysis indicated uptake of individual PBDE congeners was determined by sediment properties (organic carbon, grain size), while PCB congener uptake was governed by physico-chemical properties (octanol-water partitioning coefficient). Results suggest the utility of sediment quality guidelines for PBDEs and likely PCBs benefit if based on organic carbon-normalized concentrations. Also, where enhanced wastewater treatment increases the PBDEs to particulate organic carbon ratio in effluent, nearfield benthic invertebrates may face increased PBDE accumulation.

Water column organic carbon in a Pacific marginal sea (Strait of Georgia, Canada)

Marginal seas provide a globally important interface between land and interior ocean where organic carbon is metabolized, buried or exported. The trophic status of these seas varies seasonally, depending on river flow, primary production, the proportion of dissolved to particulate organic carbon and other factors. In the Strait of Georgia, about 80% of the organic carbon in the water column is dissolved. Organic carbon enters at the surface, with river discharge and primary production, particularly during spring and summer. The amount of organic carbon passing through the Strait (approximately 16x10(8) kg C yr(-1)) is almost twice the standing inventory (approximately 9.4x10(8) kg C). The organic carbon that is oxidized within the Strait (approximately 5.6x10(8) kg yr(-1)) presumably supports microbial food webs or participates in chemical or photochemical reactions, while that which is exported (7.2x10(8) kg yr(-1)) represents a local source of organic carbon to the open ocean.