Weathered Petroleum Hydrocarbons Research Articles

Partitioning of Per‐ and Polyfluoroalkyl Substances to Weathered Light Non‐Aqueous Phase Liquid

AbstractPer‐ and polyfluoroalkyl substances (PFAS) and weathered petroleum hydrocarbons can be co‐contaminants at sites where aqueous film‐forming foam (AFFF) was used to extinguish high‐temperature petroleum fires. Here, we report on the partitioning of six PFAS between water and a weathered diesel and gasoline range hydrocarbon light non‐aqueous phase liquid (LNAPL) collected from the subsurface of a decommissioned refinery. Results showed that both the structural features of PFAS and the characteristics of LNAPL exhibited significant impacts on the magnitude of PFAS partitioned to the LNAPL. The LNAPL–water partition coefficients (Kl) of PFOA and PFOS to the weathered LNAPL measured in this work were nearly or more than 10 times greater than Kl values calculated by others for partitioning to single‐component, unweathered NAPLs, indicating that laboratory studies evaluating LNAPL–water partitioning studies using single component NAPLs can largely underestimate the Kl expected to be encountered at contaminated AFFF sites. Interactions with LNAPL can be important controllers of PFAS fate and transport, and the Kl values estimated in this work suggest that LNAPL could be a significant transport sink for PFAS in the field. Results from this work suggest that PFAS partitioning to weathered LNAPL is an important process to be considered when designing remedial strategies, particularly those incorporating monitored natural attenuation or natural source zone depletion.

Phytotoxicity of weathered petroleum hydrocarbons in soil to boreal plant species

Canada has extensive petroleum hydrocarbon (PHC) contamination in northern areas and the boreal forest region from historical oil and gas activities. Since the 2013 standardization of boreal forest species for plant toxicity testing in Canada, there has been a need to build the primary literature of the toxicity of weathered PHCs to these species. A series of toxicity experiments were carried out using fine-grained (<0.005–0.425 mm) background (100 total mg/kg total PHCs) and weathered contaminated soil (11,900 mg/kg total PHCs) collected from a contaminated site in northern Ontario, Canada. The PHC mixture in the contaminated site soil was characterized through Canadian Council of Ministers of the Environment Fractions, as indicated by the number equivalent normal straight-chain hydrocarbons (nC). The soil was highly contaminated with Fraction 2 (>nC10 to nC16) at 4790 mg/kg and Fraction 3 (>nC16 to nC34) at 4960 mg/kg. Five plant species (Elymus trachycaulus, Achillea millefolium, Picea mariana, Salix bebbiana, and Alnus viridis) were grown from seed in 0%, 25%, 50%, 75%, and 100% relative contamination mixtures of the PHC-contaminated and background soil from the site over 2–6 weeks. All five species showed significant inhibition in shoot length, shoot weight, root length, and/or root weight (Kruskal-Wallis Tests: p < 0.05, df = 4.0). Measurements of 25% inhibitory concentrations (IC25) following PHC toxicity experiments revealed that S. bebbiana was most significantly impaired by the PHC-contaminated soil (410–990 mg/kg total PHCs), where it showed <35% germination. This study indicates that natural weathering of Fraction 2- and Fraction 3-concentrated soil did not eliminate phytotoxicity to boreal plant species. Furthermore, it builds on the limited existing literature for toxicity of PHCs on boreal plants and supports site remediation to existing Canadian provincial PHC guidelines.

Persulfate-based ISCO for field-scale remediation of NAPL-contaminated soil: Column experiments and modeling

An experimental and computational investigation of in situ chemical oxidation (ISCO) of weathered diesel fuel in soil columns was undertaken to validate a reactive-transport model capable of predicting contaminant mass reduction from a residual source zone. Reactivity tests with contaminated groundwater in batch reactors were used to estimate a priori the kinetic parameters of a phenomenological model of the oxidation of petroleum hydrocarbon (PHC) mixture fractions. The transport model, which incorporated groundwater flow, dissolution of main PHC fractions, and homogeneous reaction in the aqueous phase, was subsequently validated against experimental data of ISCO in soil columns using repetitive treatments with unactivated and alkaline-activated persulfate. No significant effect of the initial concentration of persulfate on the remediation performance was observed in the batch system, but alkaline activation significantly improved performance. The alkaline-activated persulfate treatment achieved ∼80% removal of the initial NAPL mass in soil columns. The combination of models and experiments described herein should enable the rational design of field-scale advanced oxidation strategies for the removal of weathered petroleum hydrocarbons. This expectation was supported by a comprehensive demonstration study at a historical site contaminated by weathered diesel fuel present as a residual source within the soil and dissolved within groundwater.

Assessment of the toxicity of weathered petroleum hydrocarbon impacted soils to native plants from a site in the Canadian Subarctic

Remedial guidelines for petroleum hydrocarbons (PHCs) in soil aid in the mitigation of risks to human health and the environmental. However, some remediation guidelines may overestimate the potential for adverse effects to native plant species, contributing to unnecessary remedial efforts in attempts to meet the guidelines. At sites where PHC-contaminated soils undergo weathering, some PHCs may persist but with decreased bioavailability to organisms. In this study, the toxicity of both coarse and fine-grained subarctic soils, contaminated with weathered PHCs were assessed using five native plant species (Picea mariana, Achillea millefolium, Alnus viridis, Elymus trachycaulus and Salix bebbiana). Soil toxicity tests were conducted in a growth chamber with parameters set to simulate the site's subarctic climate conditions. Reference toxicant tests using boric acid were conducted to provide confidence in the interpretation of the results for the PHC-contaminated soils, and also provide new information on the sensitivities of the four boreal species to boric acid. All plants exhibited reduced growth and germination rates as boric acid concentrations increased. Despite exceeding the Canada-wide standard guidelines for Fraction 3 PHCs, field-collected contaminated soils had no significant negative impacts on the growth (i.e., length, dry weight and emergence) of any of the plant species tested.

Phytoremediation of soil contaminated with weathered petroleum hydrocarbons by applying mineral fertilization, an anionic surfactant, or hydrocarbonoclastic bacteria

This study evaluated the effect of the application of mineral fertilization (F), the anionic surfactant Triton X-100 (TX100), or the inoculation with a hydrocarbooclastic bacterial consortium (BCons) on the growth of Clitoria ternatea during the phytoremediation of a Gleysol contaminated with weathered petroleum hydrocarbons (39,000 mg kg−1 WPH) collected from La Venta, Tabasco (Mexico). The experiment consisted of a completely randomized design with seven treatments and four replications each under greenhouse conditions. The application of F (biostimulation) increased plant growth and biomass production; in contrast, TX100 only favored root biomass (11%) but significantly favored WPH degradation. Bioaugmentation with BCons did not show significant effects on plant growth. Nevertheless, the combination of biostimulation with bioaugmentation (BCons + F, BCons + TX100, and BCons + F+TX100) enhanced plant growth, hydrocarbonoclastic bacteria population, and WPH degradation when compared to treatments with the single application of bioaugmentation (BCons) or biostimulation (F).

Biodegradation of Weathered Petroleum Hydrocarbons Using Organic Waste Amendments

Extraction, transport, and processing of petroleum products have resulted in inadvertent contamination of soil. Various technologies have been proposed for removal of petroleum hydrocarbon contaminants, including biological techniques. Treatment of aged (weathered) petroleum compounds is challenging, as these wastes tend to be enriched with recalcitrant hydrocarbons. The purpose of the reported study was to investigate remediation of weathered petroleum via simulated landfarming using selected soil amendments. Soil contaminated by aged crude petroleum from well fields in the southern Zagros region in Iran was treated in combination with plant compost, papermill sludge, activated carbon, and molasses. Over 15 weeks, the greatest percentage removal (40%) of total petroleum hydrocarbons (TPH) occurred in the molasses treatment, followed by a 29% reduction in the plant compost treatment. The degradation constant (k), produced by a kinetic model, demonstrated the performance of the molasses over the other treatments applied; experimental data adequately fitted into first-order kinetics (k = 0.005 d−1, t½ = 71 d). Benzene decomposition was greatest (77 and 74%) in the molasses and activated carbon treatments, respectively, and was lowest in the papermill sludge treatment (41%). FTIR analysis revealed loss of benzene in all treatments. Bacterial counts were highest (4.9 × 106 CFU/g) in the plant compost treatment and lowest (1 × 105 CFU/g) in the untreated oil-contaminated soil. Based on the findings of the current study, it is possible to successfully conduct landfarming of aged petroleum deposits; however, it is recommended that common and inexpensive amendments such as molasses and plant compost be used when feasible.

Efecto de bacterias emulsificantes en la atenuación de la fitotoxicidad de suelos contaminados con petróleo intemperizado

Introduction: Plants and microorganisms have been used as bioindicators to evaluate the toxicity of hydrocarbons in soils. Objective: This study evaluates the toxicity of a chronically-contaminated Gleysol with several concentrations of weathered petroleum hydrocarbons (WPH), collected from La Venta, Tabasco (Mexico), on the growth of Clitoria ternatea and the phytoxicity attenuation due to inoculation of emulsifying bacteria. Methods: Soils with 50 and 150 g WPH kg-1, and control soil with 0.15 g WPH kg-1 (biogenic origin) were utilized, as well as the inoculation of six emulsifying bacteria and their combination (consortium). The WPH-phytotoxicity was evaluated by considering plant height, dry biomass production (root, shoot, and total), leaf area, specific leaf area, and the efficiency of photosystem II (EPSII), after 30 days. Results: WPH did not affect plant height, but soil with 50 g WPH kg-1 diminished root and total dry weight, and leaf area, when compared to both control soil and soil with 150 g WPH kg-1. The strain Sml (Stenotrophomonas maltophilia C10S1) significantly increased shoot and total dry weight, while the strain Ro (Raoultella ornithinolytica C5S3) produced higher specific leaf area relative to uninoculated plants. In control soil, the bacterial consortium stimulated plant height. The strains Sm (Serratia marcescens C11S1) and Sm2 (S. marcescens C7S3) improved plant height and specific leaf area when compared to uninoculated plants in soil with 50 g WPH kg-1. In soil with 150 g WPH kg-1, strains Spa (Stenotrophomonas pavanii C5S3F) and Cfr (Citrobacter freundii C4S3) enhanced root and shoot dry weight, respectively. The EPSII was unaffected by soil contamination. Emulsifying bacteria reduced the phytotoxic effects of WP, but depending on the content of WPH in soils. Conclusions: Soil with 50 g WPH kg-1 showed the greatest phytotoxic effects on plant growth. Bacterial inoculation favored growth, biomass production and leaf area in soil with 150 g WPH kg-1. The EPSII was not affected by WPH in soils.

Origin of hydrocarbons in suspended matter and bottom sediments near the Crimean peninsula

It was established that the content of hydrocarbons in the surface waters of the Feodosia Gulf fluctuated were varied a wide range (11–179 μg/l), and exceeded the MPC values for petroleum hydrocarbons in individual samples. The highest concentrations were observed in 2016. The composition of alkanes suggested their mixed (autochthonous and allochthonous) origin. The weathered petroleum hydrocarbons have been identified only in a few cases. In bottom sediments, the concentrations of hydrocarbons depended on their grain size distribution, and terrigenous alkanes were dominated in their composition. The oil and pyrogenic hydrocarbons’ pollution were established based on the composition of polycyclic aromatic hydrocarbons. In the open part of the Black Sea, southward the Crimean peninsula, the hydrocarbon content in surface waters and bottom sediments were at the level of background concentrations, and homologs of terrigenous origin dominated in their composition.

Effect of digestate application on microbial respiration and bacterial communities' diversity during bioremediation of weathered petroleum hydrocarbons contaminated soils

Digestate is an organic by-product of biogas production via anaerobic digestion processes and has a great potential as soil fertilizer due to concentrated nutrients. In this study, we examined digestate as a potential nutrient and microbial seeding for bioremediation of weathered (aged) petroleum hydrocarbon contaminated soils. We analysed 6 different treatments in microcosm using two industrial soils having different textures: a clay rich soil and a sandy soil. After 30 days of incubation, the highest total petroleum hydrocarbons (TPH) removal was observed in microcosms containing digestate together with bulking agent (17.8% and 12.7% higher than control in clay rich soil and sandy soil, respectively) or digestate together with immobilized bacteria (13.4% and 9% higher than control in clay rich soil and sandy soil, respectively). After digestate application microbial respiration was enhanced in sandy soil and inhibited in clay rich soil due to aggregates formation. After bulking agent addition to clay rich soil aggregates size was reduced and oxygen uptake was improved. Application of digestate to soil resulted in the development of distinct microbial groups in amended and non-amended soils. Genera containing species able to degrade TPH like Acinetobacter and Mycobacterium were abundant in digestate and in soil amended with digestate. Quantification of alkB genes, encoding alkane monoxygenase, revealed high concentration of these genes in digestate bacterial community. After application of digestate, the level of alkB genes significantly increased in soils and remained high until the end of the treatment. The study revealed great potential of digestate as a nutrient and bacteria source for soil bioremediation.

Diesel degradation by emulsifying bacteria isolated from soils polluted with weathered petroleum hydrocarbons

This study evaluated bacterial populations (total, lipolytic, P-solubilizers, N-fixing free, and hydrocarbonoclastic bacteria) from uncontaminated soils or soils contaminated with weathered petroleum hydrocarbons (WPH) and evaluated the emulsifying and diesel-degrading properties for each bacterial strain. Soils collected from Tabasco State (Mexico) included moderately contaminated (50,000mgkg−1), highly contaminated (150,000mgkg−1), or non-contaminated samples. Bacterial populations showed significant differences (P<0.05) among the three soils, with highly contaminated soil containing the highest populations of lipolytic and phosphate (P) solubilizing bacteria. Thirteen bacterial strains were isolated from non-contaminated and highly contaminated soils. These bacteria were able to degrade diesel and to produce surfactants, as determined by four methods [emulsification index (E24%), cell surface hydrophobicity, drop collapse, and hydrocarbon displacement]. Bacteria with high emulsification activity were molecularly identified (16S rRNA) as Serratia marcescens C11S1, S. marcescens C7S3A, Citrobacter freundii CCC4DS3, Raoultella ornithinolytica C5S3, Stenotrophomonas maltophilia CCC10S1, and St. pavanii C5S3FN. The strain C7S3A showed the highest diesel emulsification (74.2%) and high cell hydrophobicity (173%) and diesel degradation (96%). A consortium containing the six bacterial strains also showed high diesel degradation (97%). The biochemical tests demonstrated that the bacterial strains were also able to produce indole acetic acid. Our results suggest that the emulsifying bacteria may useful for bioremediating soils chronically contaminated with weathered petroleum hydrocarbons.

Canine Oil Detection (K9-SCAT) following 2015 Releases from the T/V Arrow Wreck

Abstract The T/V Arrow sank in 1970, spilling Bunker C fuel oil into Chedabucto Bay, Nova Scotia. In the summer and fall of 2015, residual oil leaked from the sunken vessel and re-oiled shorelines in the Bay. A K9-SCAT field study, funded by Environment and Climate Change Canada (ECCC), was conducted in June 2016 to assess the capability of detection canines to locate stranded oil following the new releases. The canine detected small amounts of weathered surface oil that were barely visible, and in some cases, not visible, to the SCAT-trained observers, as well as subsurface oil on mixed- and coarse-sediment beaches. The average speed of a survey, in terms of the length of shoreline covered, varied depending on the shore type and the width of the survey band. The most challenging site was a steep bedrock shoreline with an alongshore survey rate of 0.2 linear km/hour. Typical alongshore coverage rates for the wide, mixed sediment were in the range 0.7 to 1.2 linear km/hour, and for both straight, wide sand beaches were 1.2 km/hour. The highest alongshore rate was 2.4 linear km/hour for the narrow beach on Janvrin Island. The successful detection of 2015 T/V Arrow cargo oil (both naturally stranded and intentionally planted) on selected Chedabucto Bay shorelines indicates that there is a low risk, high confidence level that the canine did not miss subsurface oil, although that possibility may exist. Where the canine made an alert and no surface oil was visible, chemical analyses of sediment samples indicated that weathered petroleum hydrocarbons were present at those locations and, therefore, the canine had made correct alerts. The results provide further “proof of concept” for K9-SCAT teams to support surface and subsurface oil detection during traditional shoreline assessment surveys.

Phytoremediation potential and ecological and phenological changes of native pioneer plants from weathered oil spill-impacted sites at tropical wetlands.

Pioneer native plant species from weathered oil spill-affected sites were selected to study their potential for phytoremediation on the basis of their ecological and phenological changes during the phytoremediation process. Experiments were conducted in field and in greenhouse. In field, native plants from aged oil spill-impacted sites with up 400g of weathered petroleum hydrocarbons per kilogram soil were selected. In the impacted sites, the principal dominant plant species with potential for hydrocarbons removal were Cyperus laxus, Cyperus esculentus, and Ludwigia peploides. In greenhouse, the phenology of the selected plant species was drastically affected by the hydrocarbons level above 325g total petroleum hydrocarbons (TPH) per kilogram soil after 2years of phytoremediation of soils from the aged oil spill-impacted sites. From the phytoremediation treatments, a mix-culture of C. laxus, C. esculentus, and L. peploides in soil containing 325gTPH/kg soil, from which 20.3% were polyaromatic hydrocarbons (PAH) and 34.2% were asphaltenes (ASF), was able to remove up 93% of the TPH, while in unvegetated soil the TPH removal was 12.6%. Furthermore, evaluation of the biodiversity and life forms of plant species in the impacted sites showed that phytoremediation with C. esculentus, alone or in a mix-culture with C. laxus and L. peploides, reduces the TPH to such extent that the native plant community was progressively reestablished by replacing the cultivated species resulting in the ecological recovery of the affected soil. These results demonstrate that native Cyperus species from weathered oil spill-affected sites, specifically C. esculentus and C. laxus, alone or in a mix-culture, have particular potential for phytoremediation of soils from tropical wetlands contaminated with weathered oil hydrocarbons.

Identification of unresolved complex mixtures (UCMs) of hydrocarbons in commercial fish oil supplements

Heightened awareness of the health benefits of fish oil consumption has led to a great increase in the number of fish oil supplements available to the consumer. Therefore manufacturers are continually looking for ways to distinguish their products from those of competitors. Minimally refined or virgin fish oils provide a unique feature; however, petroleum hydrocarbon contamination from oil spills is a reality in the world's oceans. The question arises whether oil produced from fish species caught in these polluted areas is free of petroleum hydrocarbons, with particular interest in unresolved complex mixtures (UCMs). This study investigates the presence of UCMs in commercially available fish oil supplements advertised as being virgin, as well as refined. Weathered petroleum hydrocarbons in the form of a UCM were found at 523 µg g(-1) in a virgin Alaskan salmon oil supplement. Supplements that were refined were free of this contamination. Fish used in the production of fish oil supplements appear to have accumulated petrogenic hydrocarbons in their tissues which were not removed by minimal oil refining. Further study is required to determine if there are any health implications associated with long-term consumption of these contaminated supplements.

Combining Solvent Extraction and Bioremediation for Removing Weathered Petroleum from Contaminated Soil

This study aimed to evaluate the efficacy, practicality and sustainability of a combined approach based on solvent extraction and biodegradation to remediate the soils contaminated with high levels of weathered petroleum hydrocarbons. The soils used in this study were obtained from the Shengli Oilfield in China, which had a long history of contamination with high concentrations of petroleum hydrocarbons. The contaminated soils were washed using a composite organic solvent consisting of hexane and pentane (4:1, v/v) and then bioremediated in microcosms which were bioaugmentated with Bacillus subtilis FQ06 strains and/or rhamnolipid. The optimal solvent extraction conditions were determined as extraction for 20 min at 25 °C with solvent-soil ratio of 6:1 (v/w). On this basis, total petroleum hydrocarbon was decreased from 140 000 to 14 000 mg kg−1, which was further reduced to < 4 000 mg kg−1 by subsequent bioremediation for 132 d. Sustainability assessment of this integrated technology showed its good performance for both short- and long-term effectiveness. Overall the results encouraged its application for remediating contaminated sites especially with high concentration weathered hydrocarbons.

Characterization of weathered petroleum hydrocarbons during a landfarming bioremediation study

Landfarming bioremediation was performed over 2 years on soil heavily polluted with weathered oil and oil derivatives: 23200 mg kg-1 of mineral oil, 35300 mg kg-1 total hydrocarbons, and 8.65 mg kg-1 of total PAHs. During the experiment, mineral oil, total hydrocarbon and PAH concentrations decreased by approximately 53%, 27% and 72%, respectively. A GC/MS-Scan was used to identify the crude oil components that persist after bioremediation treatment of contaminated soil and the metabolites generated during this process. The data shows that in weathered-hydrocarbons contaminated soil, the number of initially detected compounds after the bioremediation process further decreased over a 2 year period, and at the same time several new compounds were observed at the end of experiment. Higher persistence was also shown for heavier n-alkanes and branched alkanes, which could be detected over a longer period of time. The analysis highlights the importance of n-alkanes, their substituted derivatives and polycyclic aromatic hydrocarbons as the most significant pollutants.

Bacterial succession in a petroleum land treatment unit.

Bacterial community dynamics were investigated in a land treatment unit (LTU) established at a site contaminated with highly weathered petroleum hydrocarbons in the C(10) to C(32) range. The treatment plot, 3,000 cubic yards of soil, was supplemented with nutrients and monitored weekly for total petroleum hydrocarbons (TPH), soil water content, nutrient levels, and aerobic heterotrophic bacterial counts. Weekly soil samples were analyzed with 16S rRNA gene terminal restriction fragment (TRF) analysis to monitor bacterial community structure and dynamics during bioremediation. TPH degradation was rapid during the first 3 weeks and slowed for the remainder of the 24-week project. A sharp increase in plate counts was reported during the first 3 weeks, indicating an increase in biomass associated with petroleum degradation. Principal components analysis of TRF patterns revealed a series of sample clusters describing bacterial succession during the study. The largest shifts in bacterial community structure began as the TPH degradation rate slowed and the bacterial cell counts decreased. For the purpose of analyzing bacterial dynamics, phylotypes were generated by associating TRFs from three enzyme digests with 16S rRNA gene clones. Two phylotypes associated with Flavobacterium and Pseudomonas were dominant in TRF patterns from samples during rapid TPH degradation. After the TPH degradation rate slowed, four other phylotypes gained dominance in the community while Flavobacterium and Pseudomonas phylotypes decreased in abundance. These data suggest that specific phylotypes of bacteria were associated with the different phases of petroleum degradation in the LTU.

An Assessment of Potential Oil Spill Damage to Salt Marsh Habitats and Fishery Resources in Galveston Bay, Texas

We sampled nekton, benthic infauna, and sediments in salt marshes of upper Galveston Bay, Texas to examine relationships between habitat use and sediment hydrocarbon concentration. Most marsh sediment samples were contaminated with relatively low concentrations of weathered petroleum hydrocarbons. We found few statistically significant negative relationships between animal density and hydrocarbon concentration (6 of 63 taxa examined using simple linear regression). Hydrocarbon concentration did not contribute significantly to Stepwise Multiple Regression models we used to explore potential relationships between animal densities and environmental parameters; in most cases where hydrocarbon concentration was an important variable in the models, the relationship was positive (i.e., animal densities increased with hydrocarbon concentration). Low hydrocarbon concentrations in sediments of upper Galveston Bay marshes could have contributed to our results either because levels were too low to be toxic or levels were toxic but too low to be detected by most organisms.

The response of southern hemisphere saltmarsh plants and gastropods to experimental contamination by petroleum hydrocarbons

Field experiments examined the response of two common perennial saltmarsh plants and their gastropod epifauna to the effects of weathered petroleum hydrocarbons. Application of the petroleum hydrocarbons to the saltmarsh mimicked an accidental spill, but confined the contamination to small areas. Populations of the perennial chenopod, Sarcocornia quinqueflora, and the perennial grass, Sporobolus virginicus, showed little inertia and senesced rapidly after the application of weathered Bass Strait crude oil and diesel (11· m −2). No resprouting from underground stems or recruitment of seedling was detected up to 17 months after the application of hydrocarbons to Sarcocornia. Dead stems of the perennial grass Sporobolus persisted in areas treated with oil and diesel for up to 12 months, but showed no signs of resprouting from basal shoots or rhizomes originating from culms within the treated areas. Slow recovery from rhizomes originating outside the plots was evident after a few months but tiller growth appeared to be inhibited by residual hydrocarbons. No recruitment of seedlings was observed in the denuded plots and no other macrophytes were observed to colonise these areas until the end of the study (17 months). The response of saltmarsh gastropods to petroleum hydrocarbons shows greater inertia and stability than the vascular plants. Initial mortality was high, but migrations from the edges of the treated areas restored densities to control and pre-treatments levels within a few months. The reduction in cover of plants apparently had little effect on the abundance of gastropods although residual effects of the hydrocarbons may have inhibited predators of gastropods from the openings created by the death of saltmarsh plants. We predict that the widespread contamination of saltmarshes in south-eastern Australia by spills of crude oil or diesel would result in the loss of vegetation cover and reductions in the abundance of gastropod epifauna.