Walter J. Cretney

Terrestrial and marine biomarkers in a seasonally ice-covered Arctic estuary — integration of multivariate and biomarker approaches

Hydrocarbons, including alkanes, alkenes, hopane triterpenes and polycyclic aromatic hydrocarbons (PAHs), plus sterols, n-alcohols and a number of higher plant triterpenoids have been determined for suspended particulate, sediment trap and sediment samples taken from the Mackenzie River and the adjacent Mackenzie shelf in the Beaufort Sea. These biomarkers are valuable tracers of terrigenous and petrogenic inputs from the river to the shelf water column and are also useful for assessing marine production in the Mackenzie River estuary. We use Principal Component Analysis (PCA) to provide a robust classification of biomarkers according to their primary source (e.g. terrigenous, marine) and to identify which biomarkers covary. The Mackenzie River is the dominant source for n-alkanes, n-alcohols, sterols and triterpenoids from higher plants, diagenetic hopanes, petrogenic isoprenoids and parent (unsubstituted) PAHs to the Mackenzie shelf. The riverine hydrocarbon signature of these markers is modified by preferential settling out of lithic material relative to less dense higher plant debris. Seasonal marine production of a suite of alkenes, sterols and alcohols from phytoplankton and Zooplankton is evident in water column and sediment trap samples, but these labile compounds tend not to be preserved in surficial sediments. Although few individual sterols provide unambiguous markers of terrestrial or marine organic matter, PCA successfully classifies sterols as either principally marine or principally terrestrial. n-Alcohols are often overlooked as biomarkers, but we find that they too reflect the relative contributions of Zooplankton and terrigenous inputs in the Mackenzie estuary. To quantify dispersal of riverine material on the adjacent shelf in the context of dilution by marine production, we develop a multivariate Partial Least Squares (PLS) path model. We find that the PLS results strengthen geochemical interpretations based on individual biomarkers by providing a quantitative representation of the differences among samples. PLS successfully models the increases in terrigenous particulate on the shelf with river flow and the effect of autochthonous production.

Occurrence and congener profiles of polybrominated diphenyl ethers (PBDEs) in environmental samples from coastal British Columbia, Canada

Environmental levels and detailed congener profiles (31 congeners and 3 coeluting congener groups) of polybrominated diphenyl ethers (PBDEs) were assessed in a number of biota samples taken over a large geographic range covering harbours and industrial sites on Canadas West Coast. Additionally, PBDE congener profiles were determined using semipermeable membrane devices (SPMDs) deployed in the Fraser River, the river in Western Canada with the largest industrial activity. PBDE levels detected in biota were between 4 and 2300 ng/g lipid and these levels were compared with those reported in selected European biota to provide a wider perspective on PBDE contamination on Canadas West Coast. Thirteen-congener PBDE patterns in the environmental samples were examined using principal component analysis (PCA), and additionally, comparisons were made between the PBDE profiles in the sample groups and commercially used PBDE technical mixtures (e.g., Bromkals) on a percent composition basis. PCA on congener specific data revealed that PBDE patterns are remarkably similar over a wide geographical range in Western Canada, however, the general pattern in environmental samples varies significantly from those of the predominant technical mixtures. Finally, correlations between PBDE and other persistent and toxic co-occurring contaminants found in Dungeness crab were determined.

Alkane, terpene and polycyclic aromatic hydrocarbon geochemistry of the Mackenzie River and Mackenzie shelf: Riverine contributions to Beaufort Sea coastal sediment

Abstract 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.

Uptake rates of semipermeable membrane devices (SPMDs) for PCDDs, PCDFs and PCBs in water and sediment.

Uptake rates of several PCDDs, PCDFs and PCBs were measured for semipermeable membrane devices (SPMDs) under controlled conditions in bulk water and sediment. The study was performed at 19 degrees C and 11 degrees C, and water and sediment concentrations were measured during the exposure. Linear uptake rates for specific PCDD/Fs and PCBs in 19 degrees C water varied from 34 to 111 l/m2 day and in 11 degrees C water from 8.8 to 96 l/m2 day for the whole SPMD. Uptake rates at 19 degrees C sediment ranged from 9.0 to 80 mgOC/m2 day and in 11 degrees C sediment, from 3.0 to 31, mgOC/m2 day. Partitioning of the compounds between membrane and lipid was also measured during the linear uptake phase. The membrane-lipid concentration ratios ranged from 0.02 to 1.11 depending on the compound, temperature, and bulk medium.

Geochemistry and fluxes of hydrocarbons to the Beaufort Sea shelf: A multivariate comparison of fluvial inputs and coastal erosion of peat using principal components analysis

Abstract The allochthonous inputs of hydrocarbon to the Canadian Beaufort Shelf were studied by applying principal components analysis (PCA) to well-validated and rigorously blank-corrected samples. Incorporation of a wide range of perdeuterated n-alkanes and PAH into the analysis scheme ensured that only reliably quantified variables were used to interpret the hydrocarbon geochemistry. Application of PCA to Mackenzie River samples demonstrated a homogeneous system, from which we infer coupling or equilibrium between the river particulate hydrocarbons and the dissolved fraction. Particulate (particle size > 0.7 μm) hydrocarbon flux from the Mackenzie River is by far the most important terrestrially derived source of hydrocarbons to the Beaufort Sea. The Mackenzie River particulates have a distinct n-alkane signature which can be used to identify the riverine influence on the hydrocarbon geochemistry of the Beaufort Sea shelf. Based on one years data, the flux of total alkanes is 440 ± 94 tonne/a, and PAH is 49 ± 8 tonne/a (uncertainties are one standard deviation of the sampling and analytical variation). The particulate flux exceeds the accompanying dissolved hydrocarbon flux by two orders of magnitude and has a strong seasonal cycle: winter contributes less than an estimated 0.6% of total annual flux. Deltaic silt from the western Mackenzie delta and the smaller amounts of detritus from coastal erosion of peat are minor hydrocarbon sources and contribute, in total, less than 10% to the budget for most alkanes. An important exception, with regard to shelf geochemistry, is the significant quantity of peat-derived higher plant n-alkanes.

Distribution and source of tar on the Pacific Ocean

Abstract Petroleum residues, or tar lumps, are concentrated in the northwestern portion of the Pacific Ocean, particularly in the Kuroshio current system. The source of the tar appears to be tank washings from tankers on the very large Middle East to Japan route. Tar pollutants apparently are discharged by tankers south of Japan, become entrained in the Kuroshio current, and create a plume of contamination which extends downstream for 7000 km across the Pacific.

Biota – Sediment partitioning of aluminium smelter related PAHs and pulp mill related diterpenes by intertidal clams at Kitimat, British Columbia

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; BSAFs <1 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 (BSAFs >500). 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.

On the distribution of dissolved hydrocarbons in natural water

Abstract The identity and form of dissolved organic matter in rivers and oceans are fundamental to the biogeochemical cycle of carbon. In particular, understanding the phase distribution of hydrocarbon compounds is a prerequisite to predicting the transfer between phases and the impact of anthropogenic inputs of fossil fuels to the aquatic environment. After rigorous blank-correction of each individual hydrocarbon component of dissolved and particulate hydrocarbon samples from the Mackenzie River, we obtained dissolved hydrocarbon measurements that were unquestionably above the mean blank. Equivalence of the dissolved and particulate hydrocarbon compositions indicates that the two fractions are coupled or at equilibrium in natural waters. Changes in individual hydrocarbon concentrations with sample volume suggest that the dissolved hydrocarbons may be distributed fractally in water.

Low hepatic ethoxyresorufin-o-deethylase activity correlates with high organochlorine concentrations in Atlantic tomcod from the Canadian east coast

A suppression of hepatic ethoxyresorufin-O-deethylase (EROD) activity was reported recently in large-sized Atlantic tomcod (Microgadus tomcod) from the St. Lawrence Estuary (SLE; QC, Canada), possibly related to chronic exposure to persistent contaminants and/or to emaciation. In the present study, hepatic concentrations of organochlorine contaminants and biological responses were measured in female tomcods from three estuaries located on the Canadian east coast: The SLE, the Miramichi (ME), and the Richibucto (RE) Rivers Estuaries (NB, Canada). Tomcods from the SLE had higher hepatic concentrations of organochlorine contaminants than tomcods from the ME and RE. For example, concentrations of polychlorinated biphenyls (PCBs, lipid wt) were 2.5 to 4 times higher, and concentrations of mirex and chlordanes were 6 times higher, in tomcods from the SLE than in tomcods from the other sites. Concentrations of polycyclic aromatic hydrocarbons (PAHs) metabolites in the bile did not differ among sites. The pattern of biological responses differed markedly between the SLE and the two other sites. Tomcods from the SLE had 1.5 times higher concentrations of DNA adducts and 2 times higher rates of hepatocellular proliferation, but 20 times lower hepatic EROD activity, than tomcods from the ME and RE. Lipid content was not correlated with EROD activity, indicating that low hepatic lipid content alone does not cause suppression of EROD activity in Atlantic tomcod. In contrast, for the three sites combined, EROD activity decreased as concentrations of PCBs increased. Within sites, hepatic PCB concentrations increased as lipid content decreased. This study supports the hypothesis that low EROD activity in SLE tomcods is related to chronic exposure to organochlorine contaminants.

BIODEGRADATION OF A CHEMICALLY DISPERSED CRUDE OIL

ABSTRACT The n-alkane fraction of Prudhoe Bay crude oil dispersed with Corexit 9527 disappeared rapidly from the water column directly beneath a seawater surface slick contained by an enclosure. Biodegradation appeared to be more important than nonbiological volatilization or photooxidation processes. Extracellular polysaccharides, synthesized by floc-forming bacteria, accumulated in the water column of the enclosures during n-alkane degradation. The study demonstrates the possible usefulness of Corexit 9527 in accelerating the conversion of this crude oil fraction by the indigenous microflora of coastal marine waters.