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Marine coastal areas of British Columbia, Canada are subject to a gradient of increasing anthropogenic sources from pristine areas in the north to the more urbanised areas of the south. Along the gradient, the relative contributions of polycyclic aromatic hydrocarbons (PAHs) from multiple natural and anthropogenic sources are not well understood, but concerns linger about bioavailability and consequent risks to marine biota. Composition patterns and principal components analysis (PCA) models for surface sediment and core samples collected along this transect indicate that samples from the urbanised Vancouver area have the highest proportions of tricyclic terpane, hopane and sterane biomarkers, UCM (unresolved complex mixture), the alkyl fluoranthene/pyrene and benz[a]anthracene/chrysene series and most parent PAHs. Those from Hecate and Queen Charlotte Straits and other locations in the Strait of Georgia have, on the other hand, higher proportions of the resolved alkanes, and petrogenic alkyl naphthalene, fluorene, dibenzothiophene and phenanthrene/anthracene series. PAH ratios clearly indicate a predominance of combustion sources for the four ring and higher parent PAHs for all the sediments. Most samples have values close to the biomass/solid fuel and liquid fuel combustion borderline for ratios of the major PAHs, but liquid fuel combustion input dominates closer to urbanised locations. Ratios also suggest similar pyrogenic and petrogenic inputs between central Hecate Strait and reference sediments from Hecate Strait through to Queen Charlotte Strait, which indicates that biomass combustion and immature coal formations are the major putative respective sources for the reference areas. Alkyl PAH ratios for the C3 and C4 naphthalenes, C2 and C3 phenanthrenes and 3- and 2-methylchrysene, reflecting terrigenous/vascular plant sources and petroleum maturity, exhibit marked differences between Comox bituminous coal and Alberta Sweet Mixed Blend (ASMB) oil and reveal that the petrogenic input in all of the sediments is non-biodegraded. Ratios of these alkyl PAHs with multiple substituents indicate that the sediment samples in the northern Strait of Georgia closest to the Comox coal field receive relatively constant input of eroded coal, while those in the southern Strait of Georgia and Vancouver Harbour show a composition closest to ASMB oil. PAHs associated with liquid fossil fuel combustion and petroleum discharges adjacent to urbanised areas are expected to be fully bioavailable to marine food webs, while the char from biomass combustion and coal from immature deposits in more remote areas would have limited bioavailability. This implies that biota in remote areas of Hecate Strait/Queen Charlotte Sound are likely not adapted to the presence of oil and thus would be more sensitive to exposure to spilled oil than those in the more impacted environments in southern British Columbia.

Significant reserves of oil and gas have been predicted for Hecate Strait, a pristine, semi-enclosed sea on the continental shelf adjacent to British Columbia, on the west coast of Canada. To establish a baseline for the natural background of hydrocarbons in sediment prior to any further offshore oil and gas development or increase in oil tanker traffic in the Hecate Strait region, three sediment box cores were collected along a west to east transect across southern Hecate Strait in September 2003. 210 Pb measurements established that the bottom sections date to ∼1920, pre-1800 and ∼1870, respectively, which predate any significant industrial development on the coast. Alkane and polycyclic aromatic hydrocarbon (PAH) concentrations are low in most sediment samples and both the concentrations and fluxes differ little between surface and bottom core sections. PAH profiles exhibit a dominance of alkyl PAHs for each alkyl PAH homologous series with varying amounts of parent (unsubstituted) PAHs, while alkane chromatograms show no unresolved complex mixture (UCM), and there is little change in composition between present day and pre-1800 sediments for most parameters. Principal components analysis (PCA) models, and PAH and biomarker ratios indicate that composition patterns are consistent with low and varying natural petrogenic and pyrogenic inputs, with little or no anthropogenic input. The most likely primary source of petrogenic PAHs to the sediments is Cenozoic lignites from the Skonun Formation, which outcrops on Haida Gwai and underlies most of Hecate Strait. Two subsurface sections (deposited in ∼1990 and ∼1930) in the core from Milbanke Sound, on the east side of the transect, have elevated concentrations for the alkyl phenanthrene/anthracenes and dibenzothiophenes with no UCM, and most likely also have a source in immature coal. This study suggests that the Hecate Strait environment has low hydrocarbon concentrations, with an apparent minor role for oil seeps and a likelihood that most of the petrogenic PAH sources are shales or immature coals with limited PAH bioavailability. If these characteristics are representative of Hecate Strait sediments overlying the Queen Charlotte Basin, it may mean that biota are likely unadapted to the presence of oil and thus would be more sensitive to exposure to oil from an oil spill than those in a more impacted environment.

On the morning of April 9, 2015, citizens in Vancouver (British Columbia, Canada) awoke to the sight and smell of oil on the shores of popular downtown beaches. Because the oil also had spread over the shallow seawater intakes for the Vancouver Aquarium, a preliminary screening of samples was performed as a prompt, first response to assess the risks to the Aquarium collection and guide the emergency operational response. A subsequent, more detailed examination for the presence of spilled oil in sediment, biota and water samples from the Vancouver Harbour region was then conducted based on the analysis of a large suite of alkanes, petroleum biomarkers, parent polycyclic aromatic hydrocarbons (PAHs) and alkyl PAH isomers. Most of the commonly applied biomarker ratios exhibit similar values for the spilled oil, Alberta oil (the main petroleum source for British Columbia), and pre-spill and un-oiled sediment samples. In contrast, alkyl PAH isomer ratios showed a clear distinction between the spilled oil and pre-spill samples, with the largest differences shown by isomers of the methyl fluoranthene/pyrene alkyl PAH series. This novel use of alkyl PAH isomers for fingerprinting petroleum helped to confirm the grain carrier MV Marathassa as the source of the oil that affected beach and mussel samples to document definitively the spread of the oil and to establish which samples contained a mix of the oil and hydrocarbons linked to historical activities. Finally, an initial evaluation of the biological risks of the MV Marathassa oil spill in Vancouver Harbour showed that oiled beach sediments had priority parent PAH concentrations that are likely to harm marine life.

An understanding of the carbon cycle within arctic sediments requires discrimination between the terrigenous and marine components of organic carbon, insight into the removal mechanisms for labile carbon during burial and appreciation of shelf-to-basin processes. Using a large data set of multiple molecular organic markers (alkanes, alkanols, sterols, saturated and unsaturated fatty acids, dicarboxylic acids), we apply (1) principal components analysis (PCA) to obtain a robust comparison of biomarker compositions in Arctic Ocean sediments, (2) geometric mean (GM) linear regression of the PCA variables to estimate the relative contributions of labile/marine and stable/terrigenous sources to each biomarker and (3) the slope of the GM regression of each biomarker with TOC to provide a novel measure of the removal rate of each biomarker relative to phytol. The PCA- and TOC-based indices generally increase together: biomarkers with very high TOC-based removal rates such as the saturated and unsaturated n-alkanoic acids generally have a high labile/marine content from PCA, while the sterols have low removal rates, but exhibit a range of labile/marine content values and the n-alkanes and n-alkanols have low values for both. A dominant feature of all PCA models examined is a progressive decrease in the autochthonous/marine biomarkers with each increase in sediment core depth, which points to a universal diagenetic alteration of organic carbon with depth in the cores. The PCA model also displays a shelf to basin trend that is non-diagenetic and implies the ongoing (centuries or more) delivery of long-chain n-alkanes, n-alcohols and n-alkanoic acids in a matrix that is pre-formed and well-preserved within the sediments. Terrigenous biomarker distributions within the PCA model suggest that atmospheric transport of plant waxes in aerosols and the water borne transport of very fine plant macerals likely have significant roles in the export of these vascular plant biomarkers to the basins. Biomarker ratios and profiles of the PCA-based labile/marine content with core depth indicate that the PCA model is more strongly influenced by the biomarker lability than the marine content, while increases in the marine content are largely responsible for the shifts in composition for near-surface core sections.

A suite of organic biomarkers was examined in six sediment cores from two shelf-basin transects in the Chukchi and Beaufort Seas of the Arctic Ocean to compare the sources and preservation of organic carbon between the two differing depositional regimes. Profiles of polyunsaturated fatty acids (PUFAs) and several algal sterols reveal the dominance of marine carbon on the broad, shallow Chukchi Shelf and Slope, and suggest that episodic pulses of marine material may be incorporated relatively unaltered into sediments. Biomarker profiles show carbon from terrestrial sources is present throughout the Chukchi transect, but is of lesser importance and is degraded compared to that seen in the Beaufort Sea. In contrast, the narrow Beaufort Shelf system is greatly influenced by the Mackenzie River with terrestrial contributions to total organic carbon estimated as over 95% for the shelf area and approximately 65% farther offshore. An unexpected correlation between dinosterol and α-amyrin in shelf and slope sediments suggests that dinoflagellates may contribute significantly to phytoplankton abundance in areas of seasonal open water. At basin locations that are almost permanently covered with ice, sterol profiles reflect diatoms as the main source of marine carbon.

Hydrocarbon data for dated sediment cores from Fraser Basin lakes and the Strait of Georgia in Canada reveal a pristine pre-industrial background that remains unaltered in modern sediments far from human activities. These pristine sediments contain polycyclic aromatic hydrocarbons (PAHs) from combustion (natural forest and prairie fires), and alkanes and PAHs from weathering of soils containing vascular plant remains and natural petroleum hydrocarbons, and algal production. At other locations examined, however, these natural loadings have been augmented over the past century by hydrocarbons from petroleum, the combustion of liquid (oil, gasoline) and solid (coal, wood) fuels and from processing of wood either directly from disturbed land and slash burning or indirectly through pulp mill effluent. Although contamination is clearest where there are nearby human activities, alkane profiles, PAH distributions and alkane unresolved complex mixtures suggest a widespread contamination from petroleum. Combustion products from human activities can also be identified, although with less source specificity than with the petroleum products. Regional emissions from anthropogenic combustion processes appear to support modern PAH increases within the Fraser River Basin and there is little evidence of inputs from global emissions. Principal components analysis using the new centred log ratio normalisation procedure to normalise data discriminates well between PAHs entering lakes from runoff or the atmosphere and PAH formed diagenetically within lake sediments, as well as between combustion and petroleum PAHs.

Hydrocarbon measurements have been made on dissolved, suspended particulate and sediment samples collected in 1987, 1993 and 1994 from the Mackenzie River delta and shelf and in 1993 from 10 smaller Northwest Territories and Nunavut rivers that drain into the Canadian Archipelago or Hudson's Bay. Suspended particulate samples from all rivers have a resolved higher alkane pattern with a well-defined odd–even predominance consistent with a major source in terrestrial, vascular plant material. Particulate samples from the 10 smaller rivers have alkane concentrations that are similar to the Mackenzie River during summer, but PAH (polycyclic aromatic hydrocarbon) concentrations are approximately 10 times lower for the parent PAHs and 100 times lower for alkyl PAHs. PAHs on suspended particulate from the Mackenzie River exhibit a uniform composition typical of mature petrogenic sources, while PAHs in the smaller rivers are typical of combustion. The virtual absence of petrogenic PAHs in the smaller rivers is the single most important difference between these and the Mackenzie River. During summer the alkane and PAH composition of suspended particulate in the Mackenzie River is sufficiently homogenous to estimate directly the hydrocarbon load from the particulate load. Mackenzie River particulates and sediments have the hopane and sterane ratios characteristic of immature bitumens, shales or coals from the Devonian Canol formation that outcrops in the lower Mackenzie River valley. The erosion of organic-rich rocks from this formation is likely the source of the refractory petrogenic material found in the Mackenzie River delta and shelf. Data are insufficient to determine whether the petrogenic lower alkanes and PAHs have the same source or whether more mature petroleum also contributes. Because sediment samples (suspended and bed) from the Mackenzie delta have natural PAH concentrations that exceed the level where adverse biological effects are expected to occur, there is an urgent need to establish whether these petroleum-derived PAHs are bioavailable and if they are inducing effects in bottom fish and other biota.

Mill process changes and source controls instituted in the late 1980s at pulp and paper mills along the British Columbia (BC) coast produced dramatic reductions in both the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and the TEQ (2,3,7,8-TCDD toxic equivalents). Nevertheless, questions remained as to whether the sediments were acting as contaminant sources or sinks, whether crab uptake pathways have stayed the same since the mills ceased producing PCDD/Fs, and whether improvement was faster at some sites than others. To examine the processes governing the changes in PCDD/F composition, PCDD/F sources and compositional trends for the coastal BC sites were interpreted using sediment and crab PCA (principal components analysis) models and two indices based on the three main groups of PCDD/Fs that covary in all PCA models. One index measured the relative inputs of chlorine bleaching PCDFs and PCP (pentachlorophenol)-related PCDDs at each mill and harbor site whereas the other measured the relative inputs of PCP wood preservatives and pulp mill effluents. Results indicated that PCDFs produced during chlorine bleaching accumulate from sediments to crabs more readily than the PCDDs but that the chlorine bleaching TCDFs have generally decreased in importance at all mill sites. In the years just before 1995, little change was observed in either the proportion of toxic 2,3,7,8-chlorinated congeners or the PCDD/F concentrations, and the improvements seemed to have largely ceased by 1995. The lack of change in PCA composition for the harbors provided a further, disturbing indication that ecosystem recovery may have stalled. Results also implied that the main route of PCDD/Fs into crabs shifted from uptake via a pelagic food web incorporating effluent-borne PCDD/Fs associated with suspended particulate matter to uptake via a benthic food web.

Biota-sediment accumulation factors (BSAFs) for some chlorinated dibenzo- p -dioxin and dibenzofuran congeners (PCDD/Fs) in Dungeness crab (Cancer magister) hepatopancreas and associated sediments are concentration independent as required by equilibrium partition models. In particular 2, 3, 7, 8-tetrachlorodibenzo-p -dioxin (2, 3, 7, 8-TCDD), 2, 3, 7, 8-tetrachlorodibenzofuran, the 2, 3, 7, 8-substituted pentachlorodibenzofurans, and the non-2, 3, 7, 8-hexachlorodibenzofurans (HxCDFs) seem to fall into this group. The BSAFs for other isomers exhibit significant, nonlinear variations with sediment or crab PCDD/F concentrations. For some of these other isomers (e.g., the non-2, 3, 7, 8 TCDDs and possibility the 2, 3, 7, 8-substituted HxCDFs), association of a variable fraction of the total present with soot carbon may provide a satisfactory explanation for the concentration behavior. For the HxCDDs we propose that the nonlinear concentration behavior may arise from the thermodynamic properties of fluids confined in hydrophobic voids within particulate and colloidal material produced by the pulp mills. The nonlinear relationship between BSAFs and PCDD/F concentrations greatly complicates prediction of the potential for dioxin and furan bioaccumulation in crabs and the formulation of sediment quality criteria. We provide a nonlinear equation relating toxic equivalency and sediment concentrations.

Suspended sediments from the Mackenzie River Delta and surface sediments from the Beaufort Shelf were analyzed by alkaline CuO oxidation. In addition, elemental (percentage total organic carbon, inorganic carbon and silica) and stable carbon isotope compositions were determined for all samples. The carbon-normalized yields of over 60 different compounds derived from the oxidative hydrolysis of several biochemicals, including lignin, cutin, proteins, polysaccharides and lipids were quantified and subjected to principal component analyses (PCA). The results of these investigations indicate that most lignin and cutin products originate from non-woody angiosperm vascular vegetation such as that present in the tundra. For example, lignin-derived product compositions are characterized by relatively high syringyl:vanillyl and cinnamyl:vanillyl phenol ratios (exceeding 0.4 and 0.15, respectively). The compositions of these biomarkers, especially the elevated (0.5 to 1.5) acid:aldehyde ratios for vanillyl and syringyl phenols, also suggest that the land-derived organic matter (OM) exported by the Mackenzie River is highly degraded. Non-lignin CuO reaction products derived from proteins, polysaccharides and lipids display distributions that are consistent with a predominant marine (autochthonous) source. The composition of lipid-derived fatty acid products, which is in shelf sediments are dominated by hexanedecenoic acid, suggests a planktonic origin, likely from diatoms. The distribution of these biomarkers across the shelf indicates the presence of relatively fresh algal remains in at least one sample. The relationships between terrigenous biomarker concentrations and bulk 13 C/ 12 C ratios in surface sediments indicate that terrestrial organic carbon dominates in abundance (80% to 50% of total organic carbon) over much of the shelf. Marine/algal-derived carbon represents 20% to 50% of the total carbon in shelf sediments, with the largest fraction being present in the outer mid-shelf. The large variability in the yields of CuO biomarkers from the river suspended sediment samples highlights the heterogeneous nature of the particle load exported by the Mackenzie River. Such variability must be taken into account during the development of quantitative carbon budgets for the Beaufort Shelf.

Sediment cores from the Fraser estuary, Vancouver Harbour and Strait of Georgia, suspended sediment samples from the Fraser River and sediment grabs from Vancouver Harbour have been analyzed for alkanes and parent and alkyl PAHs (polycyclic aromatic hydrocarbons). Principal components analysis (PCA) clearly distinguishes mixed sources by separating parent PAHs according to molecular size, and separating alkyl substituted PAHs from higher plant PAHs. We find the Fraser River to be the predominant source for natural and anthropogenic hydrocarbons to the Strait of Georgia. The natural hydrocarbon burden from the Fraser River is augmented principally by petroleum hydrocarbons and combustion PAHs from Vancouver. Contaminated sediments from Vancouver Harbour very likely have also been transported to a major ocean disposal site off the Fraser estuary. Petroleum alkanes, which dominate Fraser River suspended sediment samples, are lost by processes such as dissolution or microbial degradation during transport and sedimentation, while PAHs from the river are delivered essentially unchanged to sediments in the strait. Hydrocarbon composition undergoes little change with depth at a reference location in the Strait of Georgia, indicating that PAH inputs have changed very little since the early part of this century. In Vancouver Harbour the low rate of sediment accumulation coupled with surface mixing has led to the retention of contaminant PAHs within the surface mixed layer, while the rapid delivery of sediments from the Fraser River has buried contaminant PAHs from historical ocean disposal in the Strait of Georgia.

The Arctic Ocean accounts for 20% of the world's continental shelves. Because the Arctic is sensitive to global change, budgets of organic carbon for its shelves are of immediate interest. The Mackenzie Shelf of the Canadian Beaufort Sea is the best North American proxy for the enormous Eurasian Shelves (large area, large river input), and the only site for which a complete organic carbon budget can be attempted, due to an extensive data base. A mass balance for the Mackenzie Shelf has been constructed for sediments, terrestrial organic carbon, and primary produced carbon. We have considered allochthonous inputs from the Mackenzie River, from coastal erosion, from smaller rivers, from groundwater, from the atmosphere and import by ice. The Mackenzie River dominates the supply to the Beaufort shelf of inorganic sediment (127 Mt a −1 ) and paniculate and dissolved terrestrial carbon (2.1 Mt a −1 POC, 1.3 Mt a −1 DOC). The combined input from all other sources contributes only about 5% of the Mackenzie load. Using sediment accumulation data we estimate that about half of the sediment supply is trapped in the delta, about 40% on the shelf and the remainder escapes the shelf edge by various processes. Autochthonous primary production in the delta and on the shelf adds a further 3.3 Mt a −1 of particulate organic carbon. A box model has been constructed to account for sediment, terrestrial organic carbon and primary produced carbon. Whereas about 60% of the terrestrial POC is preserved in delta and shelf sediments, it appears that most (97%) of the primary produced carbon is recycled and not preserved in sediments. Confidence in the budget should be improved by focusing future research on the determination of modern sedimentation rates on the delta and shelf, measurement of organic carbon content of deltaic sediments, determination of primary production on the shelf, and determination of the relative proportions of terrestrial and marine organic carbon preserved in sediments.

Eight gravity cores collected from Alice Arm and Upper Observatory Inlet in British Columbia were analyzed for 210 Pb to determine the sediment accumulation rates. Sediment samples were also analyzed for Al, Ba, Cd, Cu, Fe, Mn, Pb, and Zn to establish the transport and fate of mine tailings in Alice Arm. Sediment accumulation rates ranged from 0.17 to 0.76 g cm −2 per year in Upper Observatory Inlet; in Alice Arm the accumulation rates ranged from 1.39 g cm −2 per year near the sill to above 2 g cm −2 per year in the upper sections of the arm. The significantly lower sedimentation rates in Observatory Inlet suggest that much of the sediment and mine tailings entering Alice Arm are trapped within the arm. Elevated Cd, Pb and Zn concentrations in the cores taken from Alice Arm indicate the presence of tailings from an open-pit molybdenum mine at the head of the Arm (Kitsault). Ba, Fe and Mn increase deep in cores from the head of Alice Arm, and a maximum in the Ba concentration around 1956 in a core from near the sill are probably associated with tailings disposed earlier into the Kitsault River at the head of the inlet (Dolly Varden mines). Post-1900 increases, particularly in Cu and Zn, for sediments from upper Observatory Inlet coincide with mining and smelting operations by Anyox at Granby Bay. Both the sediment accumulation rates and the sediment metal concentrations suggest that Alice Arm is an effective trap for most of the tailings supplied to it. The application of Principal Component Analysis on the metals data set shows a remarkably clear separation between Alice Arm (Cd, Pb, Zn) and Observatory Inlet (Cu, Zn) sediments; it appears that the submarine tailings discharge used by the most recent mine at Kitsault (Amax) deposited most tailings near the outfall and down the centre of the fjord.

Understanding the sources and pathways of pollutant transport to the Arctic is fundamental to our custody of this sensitive ecosystem. To achieve such an understanding, we need to go beyond a catalog of environmental concentrations. Sediments, which are a final sink for particle-active contaminants, can provide a valuable resource to assess fluxes and sources of contaminants. Here, we interpret PAH distributions from widely distributed Arctic marine sediments both as indicators of anthropogenic contribution and to illuminate transport pathways. We use principal components analysis (PCA) to reveal the potential sources of PAHs and their geochemistry in sediments from the Beaufort and Barents Seas. PCA distinguishes between natural and anthropogenic inputs and supports a direct linkage between anthropogenic emissions and Arctic contamination. In the Beaufort Sea, PAHs and triterpenes reflect strong Mackenzie River-dominated inputs of natural PAHs and petroleum which overwhelm anthropogenic sources. In the B...

To study the largest source of river sediment to the Arctic Ocean, we have collected suspended particulates from the Mackenzie River in all seasons and sediments from the Mackenzie shelf between the river mouth and the shelf edge. These samples have been analyzed for alkanes, triterpenes and polycyclic aromatic hydrocarbons (PAHs). We found that naturally occurring hydrocarbons predominate in the river and on the shelf. These hydrocarbons include biogenic alkanes and triterpenes with a higher plant/peat origin, diagenetic PAHs from peat and plant detritus, petrogenic alkanes, triterpenes and PAHs from oil seeps and/or bitumens and combustion PAHs that are likely relict in peat deposits. Because these components vary independently, the season is found to strongly influence the concentration and composition of hydrocarbons in the Mackenzie River. While essentially the same pattern of alkanes, diagenetic hopanes and alkyl PAHs is observed in all river and most shelf sediment samples, alkane and triterpene concentration variations are strongly linked to the relative amount of higher plant/peat material. Polycyclic aromatic hydrocarbon molecular-mass profiles also appear to be tied primarily to varying proportions of peat, with an additional petrogenic component which is most likely associated with lithic material mobilized by the Mackenzie River at freshet. Consistent with the general lack of alkyl PAHs in peat, the higher PAHs found in the river are probably derived from forest and tundra fires. A few anthropogenic/pyrogenic compounds are manifest only at the shelf edge, probably due to a weakening of the river influence. We take this observation of pyrogenic PAHs and the pronounced source differences between two sediment samples collected at the shelf edge as evidence of a transition from dominance by the Mackenzie River to the geochemistry prevalent in Arctic regions far removed from major rivers.

Sediment-associated hydrocarbons can pose a risk to wildlife that rely on benthic marine food webs. We measured hydrocarbons in sediments from the habitat of protected sea otters in coastal British Columbia, Canada. Alkane concentrations were dominated by higher odd-chain n-alkanes at all sites, indicating terrestrial plant inputs. While remote sites were dominated by petrogenic polycyclic aromatic hydrocarbons (PAHs), small harbour sites within sea otter habitat and sites from an urban reference area reflected weathered petroleum and biomass and fossil fuel combustion. The partitioning of hydrocarbons between sediments and adjacent food webs provides an important exposure route for sea otters, as they consume ∼25% of their body weight per day in benthic invertebrates. Thus, exceedences of PAH sediment quality guidelines designed to protect aquatic biota at 20% of the sites in sea otter habitat suggest that sea otters are vulnerable to hydrocarbon contamination even in the absence of catastrophic oil spills.

The question of polycyclic aromatic hydrocarbon (PAH) bioavailability and its relationship to specific PAH sources with different PAH binding characteristics is an important one, because bioavailability drives PAH accumulation in biota and ultimately the biochemical responses to the PAH contaminants. The industrial harbour at Kitimat (British Columbia, Canada) provides an ideal location to study the bioavailability and bioaccumulation of sediment hydrocarbons to low trophic level biota. Samples of soft shell clams (Mya arenaria) and intertidal sediment collected from multiple sites over six years at various distances from an aluminium smelter and a pulp and paper mill were analysed for 106 PAHs, plant diterpenes and other aromatic fraction hydrocarbons. Interpretation using PAH source ratios and multivariate data analysis reveals six principal hydrocarbon sources: PAHs in coke, pitch and emissions from anode combustion from the aluminium smelter, vascular plant terpenes and aromatised terpenes from the pulp and paper mill, petroleum PAHs from shipping and other anthropogenic activities and PAHs from natural plant detritus. Harbour sediments predominantly contain either pitch or pyrogenic PAHs from the smelter, while clams predominantly contain plant derived PAHs and diterpenes from the adjacent pulp mill. PAHs from the smelter have low bioavailability to clams (Biota-Sediment Accumulation Factors; BSAFs1 for pitch and coke;10 for anode combustion, decreasing to ∼0.1 for the mass 300 and 302 PAHs), possibly due to binding to pitch or soot carbon matrices. Decreases in PAH isomer ratios between sediments and clams likely reflect a combination of variation in uptake kinetics of petroleum PAHs and compound specific metabolism, with the importance of petroleum PAHs decreasing with increasing molecular weight. Plant derived compounds exhibit little natural bioaccumulation at reference sites, but unsaturated and aromatised diterpenes released from resins by industrial pulping processes are readily accumulated by the clams (BSAFs500). Thus while most of the smelter associated PAHs in sediments may not be bioavailable to benthic organisms, the plant terpenes (including retene, totarol, ferruginol, manool, dehydroabietane and other plant terpenes that form the chemical defence mechanism of conifers) released by pulp mills are bioavailable and possess demonstrated toxic properties. The large scale release of plant terpenes by some of the many pulp mills located in British Columbia and elsewhere represents a largely undocumented risk to aquatic biota.

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.

Sediment samples were collected to study the dispersion and fate of mineral oil hydrocarbons from the above-water discharge of oiled drill cuttings at two exploration well sites. At the shallow water (16 m), exposed location, the primary method of dispersion was wave action. Aliphatic hydrocarbon samples at times showed substantial weathering and concentrations decreased to ten times background at approximately 200 m from the wellhead. The oiled cuttings pile under the drill rig was observed to disappear within three months. At the deeper water (70 m) location, the dispersal mechanism was ocean (tidal) currents and the oiled cuttings appeared to be much more persistent. Hydrocarbon samples showed no significant weathering and aliphatic concentrations remained more than an order of magnitude above background 1500 m from the wellhead in the primary current direction. Concentrations three orders of magnitude above background were confined within 400 m, and four orders within 200 m. Aromatic hydrocarbon profiles at both well sites indicated a source other than the base oil.

Polycyclic aromatic hydrocarbon (PAH) concentrations in suspended particulate samples from the Mackenzie River delta and shelf sediments from the Beaufort Sea are higher than expected for a pristine area. Low concentrations of combustion PAHs indicate that anthropogenic inputs are low. Alkyl PAH distributions indicate that a significant component of the lower molecular weight parent (unsubstituted) PAH fraction is petrogenic. The majority of the high molecular weight PAHs, together with the petrogenic PAHs, have a principal source in the Mackenzie River. Despite the high PAH content, we consider the area still to be pristine. Although PAH concentrations are below the concentrations believed to induce toxic effects on biota, the high natural concentrations may make this region of the Arctic sensitive to additional PAHs from human activities. Key words: polycyclic aromatic hydrocarbon (PAH), Arctic, baseline, sediment, effects threshold, principal components analysis

Synchronous samples of sediment and Dungeness crab (Cancer magister) hepatopancreas, which were obtained for monitoring and assessment purposes at British Columbia, Canada, marine pulp mill sites between 1990 and 1995, were used to calculate biota-sediment accumulation factors (BSAFs) for individual chlorinated dibenzo-p -dioxin and dibenzofuran congeners (PCDD/Fs). The BSAFs for individual pairs of samples were highly variable, and no systematic trends were apparent in the observed accumulation factors over time, with crab size, with crab lipid concentration, with sediment percent organic carbon, or among mill sites or depositional environments. Composition and source differences in sedimentary PCDD/Fs, which are apparent as principal components analysis class separations in the sediment data set, also did not correlate with differences in BSAFs. This independence from environmental factors provides a valuable endorsement of the BASF concept for the formulation of aquatic effects-based sediment-quality criteria and human risk-assessment guidelines. However, BSAF values did exhibit a significant, nonlinear decrease with increasing log Kow and with sediment and crab PCDD/F concentrations. The correlation between BSAFs and sediment concentrations accounts for between 14 and 81% of the variability in the BSAF values. The PCDD/F congeners that are present in low concentrations and/or have reduced bioavailability are the congeners that have the strongest correlations between the BSAFs and the sediment PCDD/F concentrations. Congeners that are bioavailable to Dungeness crab exhibit poorer correlations between the BSAFs and sediment concentrations.