Diesel Oil Concentration Research Articles

Model for Microbial Degradation of Nonpolar Organic Contaminants in a Soil Slurry Reactor

An extended radial pore effective diffusion model is presented, describing the (microbial) decontamination of oil contaminated soil in a slurry. The aim of the model is to estimate the biodegradation rates of nonpolar contaminants in soil slurries. In the model, the soil is divided into three separate fractions, each of which contributes independently to the oil concentration in the slurry. The sand fraction is not inhibiting microbial degradation of the oil. The organic matter fraction limits the oil transport rate from the soil particles to the microorganisms. The clay fraction exhibits an extremely low transport rate for the nonpolar contaminants, about 1000 times lower than the organic matter fraction. The two types of clay used in this research showed comparable sorption coefficients. The model was tested on the decrease of hexachlorocyclohexane concentrations in two different types of soil. The diesel oil concentration in a sieve fraction of a contaminated soil, containing high amounts of clay and organic matter, could be modeled well with only one fitting parameter by using the previously measured sorption coefficients for hexadecane.

The effect of hydrocarbons and drilling fluids on the fecal pellet production of the deposit feeder Abra alba

The fccal pellet production of Abra alba was measured during exposure to different concentrations of diesel oil, drilling muds with different base fluids, oil-based cuttings and barite. For oil-based drilling muds a curvilinear regression ( y = ax + b log x + c), gave a very good description of the relationship between fecal pellet production ( y) and concentration of drilling mud in the sediment ( x). EC 50) (5 days) values calculated from the regression equation ranged from 57 to >1000 mg kg −1. The response was significantly correlated to the content of naphthenics in the mud. After 5 days of exposure to diesel oil and to two oil-based muds, no increase in the concentration of total hydrocarbons was found in the soft tissue of A. alba, and normal fecal pellet production was restored within 4–6 days in uncontaminated sediment. This suggests that the reduction in fecal pellet production may be due to a negative stimulus to feeding activity and ingestion, as well as to internal toxic effects on the organism. A reduction in feeding activity of A. alba may slow down the bioturbation of the sediments.

Spawning frequency, growth and mortality of Mytilus edulis larvae, exposed to copper and diesel oil

Mature Mytilus edulis were exposed to copper (concentration range 1–40 μg l ) and microencapsulated diesel oil (concentration range 200–5,000 μg l ) for 30 days and induced to spawn. EC 50 values for spawning frequency were approximately 2 μg l for copper and 800 μg l for diesel oil. Larvae (size 150 μm) from uncontaminated mussels were exposed to copper (concentration range 0.5–10 μg l ) and microencapsulated diesel oil (concentration range 5–500 μg l ) for 10 days. EC 50 values for growth were found at 5–6 μg l for copper and 25–30 μg l for diesel oil. For copper this is about the same value as found for juvenile mussels, while diesel oil is at least one order of magnitude more toxic for larvae than for juveniles. LC 50 values for larvae exposed to copper and diesel oil were about 10 μg l and 30–35 μg l , respectively. Microencapsulation of diesel oil gives a test medium which contains both water soluble and water nonsoluble fractions. Ingestion of the particulate fraction seems to increase the toxic effect.

EFFECTS OF DIESEL OIL ON COMMERCIAL BENTHIC ALGAE IN NORWAY1

ABSTRACT The kelp Laminaria digitata and the fucoid Ascophyllum nodosum are being studied to see if low, continuous dosage of diesel oil over a two-year period has any effects on length growth. This project is part of a larger experiment to assess long-term effects of low concentrations of oil on a simulated littoral rock community kept in four 50 m3 concrete basins equipped with artificially made waves and tide. Over three years, four fucoids planted along with associated flora and fauna have established luxuriant and relatively stable communities. From September 1982 to autumn 1984 the plants were exposed to diesel oil mixed with inlet seawater as a water-accommodated fraction. The exposure level averaged about 100 µg/L total hydrocarbons in the basin with the highest diesel oil concentration and about 25 µg/L in that with the lowest concentration. The other two basins served as controls. The work on A. nodosum started in June 1982. No significant growth difference was observed the first year. However, during 1983 and 1984, the new tips of plants in both oil-exposed basins were significantly shorter than those of the controls. No significant difference in growth of L. digitata was noted from March to July 1983. However, during spring 1984, growth of plants in both oil-exposed basins varied significantly from the controls. Studies of recovery will start at the end of the diesel oil exposure and will continue until 1986.

Recovery of Mytilus edulis L. from chronic oil exposure

Previous laboratory studies 1 have shown that physiological and cellular processes of Mytilus edulis are affected by exposure to low and environmentally realistic concentrations of oil. However, there is little information concerning the rate of recovery from oil exposure and the extent to which physiological recovery may be related to the depuration of hydrocarbons from the tissues. The present study has shown a marked reduction in the feeding rate and scope for growth of mussels exposed to two concentrations of diesel oil (30 and 130 μg/litre) for 8 months. During recovery from oil exposure the depuration of hydrocarbons from the tissues was concomitant with the recovery of physiological performance. Mussels exposed to high oil concentrations (‘high-oil’ mussels) were found to recover more rapidly than those exposed to low oil concentrations (‘low-oil’ mussels), both in terms of depuration and scope for growth, and there was evidence of ‘catch-up’ growth. Recovery of both low- and high-oil mussels was complete after approximately 55 days.

Lethal and Sublethal Toxicity of Drilling Fluids to Larvae of the American Lobster,Homarus americanus

The lethal and sublethal effects of five used, whole drilling fluids on the larval stages of the American lobster (Homarus americanus) were assessed in laboratory experiments using a continuous-flow bioassay. Although the five tested drilling fluids varied markedly in their toxicity, some were highly toxic, with LC50 values as low as 74 mg/L. Sublethal exposures to drilling fluids at concentrations as low as 10–50 mg/L resulted in reduced respiration rates, reduced O:N ratios, and increased protein:lipid ratios, demonstrating a change in energetics of the larval lobsters. Growth and development of the larvae were seriously impaired by exposure to three of the five drilling fluids at concentrations of 50 and 100 mg/L. The feeding rates were also significantly reduced after a 24-h exposure to 50 mg/L drilling fluid. Exposure of larvae to barite (a major component of drilling fluids) and to a field-collected, fine-grained sediment did not result in deleterious effects. We suggest that the chemical components and not the physical properties of the drilling fluids are primarily responsible for detrimental effects. From results of the chemical analyses of the tested drilling fluids, we consider that the adverse effects of these drilling fluids cannot be attributed to any one group of chemicals. For example, diesel oil, a known toxicant, was present in the more toxic drilling fluids; however, there was no direct correlation between the toxicity of a drilling fluid and diesel oil concentration. Phenolic compounds, various metals, and other components probably also contributed to the toxicity of these drilling fluids.

Potentialities of Yeasts in Production of Single-Cell Proteins (SCP)

Different local active yeasts were isolated from air, soils, and muddy sludges. Potentialities and capabilities of 67 yeasts isolates for formation of SCP (single-cell protein) were evaluated by their cultivation on the fermentation medium, containing diesel oil as sole carbon source to select the most efficient yeast isolates. Identification of the most active organisms revealed that Candida tropicalis and Yarrowia lipolytica were the most efficient yeasts, having potentialities for SCP production. Biochemical changes which occurred during the fermentative production of SCP by Candida tropicalis revealed that during the fermentation process a deep in pH towards the acid side was recorded, and this might be due to the formation of certain organic acids with the beginning of fermentation. Yields of yeast cell biomass increased with the increase of fermentation period, reaching its optimum at 168 h, above which a decline in SCP was observed. High diesel oil concentrations in the fermentation medium harmed yeast growth and consequently a decrease in cell biomass was observed, while low diesel oil concentrations, especially in the range of 40--60 ml/litre, gave high titres of SCP. Addition of diesel oil at different intervals of the fermentation process-promoted yield of SCP.