Oil-contaminated Sites Research Articles

Assessment of the Potential for in Situ Biotreatment of Hydrocarbon-Contaminated Soils

Enhanced insitu biotreatment is a recent technology for the cleanup of contaminated soil and ground water but it has not yet been tested for many contaminants. This report describes the assessment of three hydrocarbon-contaminated sites, one contaminated with crude oil, one with lubricating oil and one with gasoline, with respect to their potential for biotreatment. All locations were permeable, sandy soils which contained low concentrations of extractable inorganic macronutrients. Degradative microbial populations were present, although their numbers were reduced in the most highly contaminated portions of the soil. Hydrocarbon analysis demonstrated that vertical penetration of contaminants into the soil was poor for the crude oil but had occurred at the other sites. There was some evidence that biodegradation at the crude and lubricating oil-contaminated sites may have occurred. The available data suggested that biotreatment of the lubricating and gasoline-contaminated sites by the provision of inorganic nutrients and oxygen to the soils might prove viable. However, it was found that the addition of inorganic nutrients resulted in an inhibition of mineralisation in the soils.

Pollutant effects on the mixed function oxygenase (MFO) and reproductive systems of the marine polychaeteNereis virens

The cytochrome P-450 dependent mixed-function oxygenase (MFO) system ofNereis virens, found in the endoplasmic reticulum of the intestinal epithelium, has similar components and cofactor requirements when compared to other invertebrates. Worms exposed to food containing benzo(a)pyrene or a mixture of polychlorinated biphenyls (Aroclor 1254) had significantly higher MFO activity and cytochrome P-450 content than unexposed ones.N. virens from a site in Porland, Maine, USA, which was heavily contaminated with oil, and nearby “clean” reference sites were studied. The weight, MFO activity and presence or absence of gametes were determined. The MFO activity in worms from the oil-contaminated site was approximately six times that of worms from the reference sites; worms from the reference areas were six times larger than oil-contaminated worms. Worms from the oil-contaminated area lacked or had undeveloped gametes in spring, summer and fall. In contrast, many of the worms collected from the reference sites at the same times had fully developed gametes.

Petroleum-degrading achlorophyllous alga Prototheca zopfii

ONE of the objectives of this research programme is to enumerate and identify petroleum-degrading microorganisms occurring in Chesapeake Bay, to assess the potential of these microorganisms to degrade petroleum in vitro and in situ and to determine the types of petroleum degraded1. We are sampling two locations in Chesapeake Bay at monthly intervals. One is Colgate Creek, an oil-contaminated site in Baltimore Harbour, the other is an area south of Parson's Island in Eastern Bay, a non-polluted shellfish harvesting region of Chesapeake Bay. The presence of petroleum in Colgate Creek and its absence in Eastern Bay has been confirmed by computerised low-resolution mass spectrometry analysis of benzene extracts of sediments collected at both sites2,3. We have routinely isolated petroleum-degrading bacteria, yeasts and filamentous fungi from Colgate Creek and Eastern Bay, but during April and May 1973, and again in 1974, an unusual organism, believed to be an algal species, was isolated from sediment of Colgate Creek. Corresponding isolates have not been isolated from Eastern Bay.

Some effects of petroleum on estuarine and marine microorganisms.

Degradation of mixed hydrocarbon substrate in a system comprising water from an environment relatively free of oil and a sediment inoculum from an oil-contaminated site was significantly greater than when sediment from the non-oil-contaminated environment served as inoculum. Mixed hydrocarbon substrate, however, was observed to have a limiting effect on the growth of autochthonous bacteria from the non-oil-contaminated estuarine source. Growth and cell yield were similarly reduced when marine sediment bacteria were cultured in seawater supplemented with mixed hydrocarbon substrate. The addition of a South Louisiana crude oil or a No. 2 fuel oil to water and sediment collected from a marsh area of Chesapeake Bay showed no limiting effects on growth of the total heterotrophic microbial flora when examined over a 28-day period. However, results of these studies indicate that the effects of petroleum on microoganisms should be examined carefully under conditions closely approximating those in situ.

Biological aspects of land rehabilitation following hydrocarbon contamination

The incorporation of hydrocarbon material into soil causes an increase in microbial oxygen uptake. Competition between micro-organisms and higher plants for available soil nitrogen also occurs. A survey of 15 oil-contaminated sites showed that members of the Leguminosae are abundant in oil-contaminated areas, possibly due to the nitrogen-fixing symbiotic relationship with Rhizobium spp. It is proposed that rehabilitation of oil spill sites includes aeration of soil, addition of nitrogen and seeding with leguminous species in order rapidly to establish a mantle of vegetation.