Oil and Chemical Pollution最新文献

The use of a surface-drifting buoy equipped with an Argos transmitter to monitor the movement of an oil slick has been evaluated. It is concluded that such a buoy could act as a useful aid to aerial surveillance during oil spill incidents.

A sandy loam soil from a mangrove freshwater environment was contaminated with 0, 25, 50, 100 and 1000 ppm concentrations of chemical demulsifiers to determine their effect on nitrogen transformation. Changes in nitrification and N mineralization rates were determined by monitoring the changes in the levels of NH₄⁺-N, NO₂⁻-N and NO₃⁻-Nin the treated soilsfor a period of 28 days. Application of Separol NF.36 and Servo C.6602 inhibited ammonfication as shown by the increase in NH₄⁺-Nlevels in the treated soil above the untreated control, though not significantly. A demulsifier concentration of 1000 ppm inhibited ammonfication most, as shown by the high level of NH₄⁺-N, while a 25 ppm concentration showed the least adverse effect on NH₄⁺-N reduction in the contaminated soils. Separol NF.36 and Servo C.6602 at the concentrations used did not result in the complete inhibition of nitrification rates. Nitrate-N levels were very minute; the effect of different concentrations of demulsifiers on NO₂⁻-N levels did not vary significantly, the NO₂⁻-N being rapidly converted to NO₃⁻-N accounting for the increases in the NO₃⁻-N levels throughout the period of investigation.

However, all concentrations of the chemical demulsifier used depressed NO₃-N levels until the 14th day in Separol NF.36 and the 7th day in the Servo C.6602 treated soils. Treatments with 1000 and 100 ppm of demulsifier depressed nitrification and N mineralization most, while 25 and 50 ppm concentrations stimulated nitrogen transformation most, especially after the 14th day in the Separol NF.36 treated soil and after the 7th day in the Servo C.6602 treated soils. The effect of Separol NF.36 and Servo C.6602 when compared, did not vary significantly. Changes in total mineral nitrogen level in the treated soils exhibited the same trend as NO₃⁻-N.

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.

In an attempt to develop a nonpolluting method for used oil disposal, sharp sand bed filtration and the continuous elution technique were used on a bench scale to carry out the reclamation of used industrial hydraulic oils. Both processes gave quantitative yields of reclaimed oils. Assessment of the qualities of these oils using standard ASTM procedures and IR spectroscopy showed that the reclaimed oils are similar to the base oil from which the hydraulic oil was formulated. The metallic impurities in the used oil were completely removed, and the oils totally dehydrated. The yields from the continuous elution process were generally higher than those of the sharp sand filtration technique.

The results of a series of chemical dispersion tests are presented, in which three crude oils (Gullfaks, Statfjord and Arabian heavy), each at 4 states of weathering, have been dispersed at 13°C with two dispersants (Finasol OSR-5 and OSR-12) using three laboratory tests (Warren Spring Rotating Flask — WSL test, Institute Français du Pétrole flow test — IFP test and MackayNadeau—Steelman — MNS test). Effectiveness and dispersed oil droplet size distributions in the different test methods have been studied and an attempt has been made to develop correlation or mathematical models of the chemical dispersion phenomena. This mathematical treatment helps to explain the reasons that the tests give different results, but it is concluded that, at present, our understanding of the basic dispersion phenomena is not sufficient to form a basis for a reliable model. Several modelling approaches are discussed in the hope that as further data and insights become available, reliable models may be developed to describe this complex process.

Afield analysis of the effect of oil and gas derived produced water discharges on the vegetation of one freshwater and two brackish wetlands in coastal Louisiana was conducted. Aboveground biomass, plant species composition, pH and salinity were measured to determine if the produced water discharge in each marsh was related to differences in plant response. Of the three marshes investigated, only one of the brackish marshes exhibited significantly lower live aboveground biomass at the site receiving produced waters compared to its adjacent reference site. Although interstitial salinities were significantly higher at the treatment site of this brackish marsh, the salinity difference between treatment and reference sites was only 1·5 ppt in a marsh with a mean salinity of 11·9 ppt. This salinity difference should have no discernible biological effect on the brackish species inhabiting this marsh. Also, the differences in species composition between treatment and reference sites of each marsh did not indicate a produced water effect. Thus, at these three produced water discharge sites the dilution of the produced water in the discharge canals, plus the sinking of higher density produced water to canal bottoms (thus making it less available for tidal movement into the marsh), appears to prevent a biologically significant negative impact on the marsh vegetation. Whether this conclusion is valid for other produced water sites needs further evaluation.

When coal tar is transported by sea it is categorized under International Maritime Organisation (IMO) guidelines for noxious liquids, by toxicity as well as other properties. Previous toxicity assessments are available for freshwater animals only, however, and are misleading because they were reported as nominal measures of the amount of coal tar added to the dilution water. Not all of this coal tar will enter solution, and if the data are corrected to measured concentrations of total organic carbon in solution, the true LC50 values are an order of magnitude less. Even lower values may be obtained by exposing the animals to whole coal tar in addition to the water-soluble fraction (WSF), but the concentration of whole coal tar in water cannot be measured accurately. It is recommended that such toxicity assessments should rely on measured values for WSF alone, and marine test values are reported here for the tiger prawn Penaeus monodon. The WSF was analysed by gas chromatography-mass spectrometry (GC/MS) to obtain 96-h LC50 values of 3·1 mg/litre total organics and 2·5 mg/litre total organic carbon.