Controlled Oil Spill Research Articles

Biomass poplar catkin fiber-based superhydrophobic aerogel with tubular-lamellar interweaved neurons-like structure

Superhydrophobic aerogels are attractive candidates in controlling oil spills. The major challenges for existing aerogels are the construction of mechanical endurance as well as accessible of building materials. Herein, a newfangled biomass superhydrophobic aerogel (M-PCF/CS) with both superior compressibility and oil caption speed is fabricated by assembling poplar catkin fiber (PCF) hollowed-out shell of 330 nm and chitosan (CS) into tubular-lamellar interweaved neurons-like structure. The resultant aerogels (porosity ~ 96.12%), with flexuous PCF as the elastic buffer and second-pore capillaries, exhibit large longitudinal and transverse compressibility, endurable fatigue tolerance, fast oil sorption rate with a capacity of 28.8–78.1 g/g at 5–25 s. In parallel, the aerogels are tolerant of NaCl, UV radiation, and organic solvents without superhydrophobic variation and a case of oil spill remediation via pump-supported experiment shows that the aerogels facilely achieve continuous oil recycling from seawater by 23052–43956 L·m–2·h–1. Furthermore, the resultant M-PCF/CS, with assistance of an oscillator, can be applied to separate oil/water emulsions with efficiency of 98.07–99.11%. The successful fabrication of this material provides a new design strategy for the construction of mechanically robust aerogels for speedy and economical cleanup of oil pollutants from water.

Effective and sustainable adsorbent materials for oil spill cleanup based on a multistage desalination process

Oil spills, which are often caused by crude oil transportation accidents, contaminate coastal waters and land and can harm aquatic life, seabirds, humans, and the entire ecosystem. Ocean currents and wind complicate oil spill cleanup and extend the oil spill area. This study proposes a new approach to control oil spills using solids recovered from the treatment of reject brine through a novel multistage desalination process. The aim is to produce applicable adsorbent for oil spill cleanup especially in the final cleaning stages. The multistage desalination process is based on the electrochemical treatment of high-salinity reject brine and Solvay and modified Solvay liquid effluents in a closed Plexiglas electrocoagulation cell. After the electrochemical treatment, the collected solids were dried and ground for utilization as adsorbents in oil spill cleanup. Results were promising for the adsorbent produced from the electrochemical treatment of the modified Solvay effluent. A maximum adsorption capacity of 2.8 g oil/g adsorbent was achieved, with an oil recovery of 98%. In addition, the regenerated solids after toluene extraction process were recycled and achieved an adsorption capacity of 2.1 g oil/g adsorbent in the second oil spill clean-up cycle. The structural and chemical characteristics of the adsorbents produced from the multistage desalination process were investigated using X-ray powder diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Results support the adoption of the collected solids as effective oil-adsorbent materials.

Durable hydrophobic Enteromorpha design for controlling oil spills in marine environment prepared by organosilane modification for efficient oil-water separation

Hydrophobic and oleophilic materials are attractive candidates for efficient oil collection due to their excellent oil-water separation. However, the most of currently reported oil adsorption materials are limited resources or require complicated preparation steps, which causes high energy consumption and not be practical for large-scale application. Herein, we report a facile strategy to modify the wettability of Enteromorpha from hydrophilic to hydrophobic, which not only greatly reduces energy consumption but also shows the outstanding capacity for oil-water separation with the maximum adsorption capacities is 11.4 g/g and the contact angle reaches 137°. The successful modification of the Enteromorpha is achieved by grafting n-octyltriethoxysilane on the surface of the pristine Enteromorpha. The hydrophobic and superoleophilic Enteromorpha guarantee adequate voids in the fibrous bundles only for oil adsorption and the oil floating on the seawater is removed by the formation of hydrogen bonding between oil and modified Enteromorpha. By optimizing test, the optimal adsorption conditions are adsorption time of 60 min, oil-water ratio of 1:10 and pH of 7. Our reported hydrophobic organosilane modified Enteromorpha will open a new avenue to control marine oil pollution and suppress the damage of Enteromorpha to the marine ecology system.

Detection of Actionable Oil using RADARSAT-2 and Simulated RADARSAT Constellation Mission Data

Abstract 688970 For oil spill response, one of the key parameters is detection of actionable oil. Actionable oil (AO), which tends to be thick, emulsified oil, refers to oil that can be cleaned-up versus non-actionable oil (sheen) which cannot be readily cleaned-up. Previous studies by MDA of a controlled oil spills in the North Sea have shown the capability of RADARSAT-2 quad polarized data to detect AO using the entropy parameter (H) derived from the Cloude-Pottier decomposition. H → 0 for oil-free water and H → 1 in the presence of an oil slick. To further test the detection of AO, RADARSAT-2, ASTER, WorldView imagery and in situ measurement were acquired April 25, 2017 at the MC20 site off Louisiana. Five oil thickness classes ranging from 1 micron to 100 microns were derived from a maximum likelihood classifier based on the ASTER and WorldView images and in situ samples. For oil-free water, the average H was 0.13 and 0.62 for the slick. There was good correlation between the variability of H and the oil thickness classes. Specifically, larger H was correlated with oil thickness in the 50 – 200 micron range and smaller H was correlated with oil in the 1 micro range. Not surprising there was overlap in H for area were the oil thickness was ~ 1 micron and the area deemed to be slick-free. The results indicate that actionable oil can be discriminated from non-actionable oil based on the relative difference of H. Although these results are encouraging, one of the operational limitations is based on the use of the relatively small swath-width (25 km – 50 km) of the RADARSAT-2 quad polarized mode. The impact of the swath-width can be mitigated with data from the RADARSAT Constellation Mission (RCM). The RCM has a compact polarimetry (CP) mode that provides more polarimetric information than dual polarized modes, less than quad polarized modes, but is available for swath widths up to 500 km. Analysis of simulated SC50 RCM data (50 m resolution, 350 km swath width) derived from the aforementioned RADARSAT-2 image shows similar oil-slick variability that was observed in the RADARSAT-2 image and hence the capability to detect AO.

Study of oil sorption behaviour of esterified oil palm empty fruit bunch (OPEFB) fibre and its kinetics and isotherm studies

Oil spills concern the public as they are incredibly harmful to the environment and the economy. A collection of business frameworks has been created to control oil spills, such as the utilization of agricultural wastes as sorbents. This paper demonstrates the use of raw and modified fibre from empty bunches of palm fruit, a low-cost adsorbent material for the oil spill in the marine environment. To improve fibre’s sorption capacity, the fibre was modified by esterification using oleic acid. The modified fibre was tested to adsorb crude oil in a batch system (Tapis and Arabian). The extent of modification was given according to weight percent gain (WPG), which was calculated on the basis of difference in weight before and after the treatment. To increase the esterification productivity, an optimization study was conducted at various concentrations of oleic acid and temperature, and achieved higher WPG (with 4.32%) and subsequently higher oil sorption capacity of 5.8 and 5.96 g/g for Tapis and Arabian crude oil, respectively. Besides, this study also focused on correspondence of surface functional groups of the adsorbent using Fourier transform infrared (FTIR) spectrum, surface morphology by field emission scanning electron microscopy (FESEM) and measure the contact angle using Interfacial Tension. Two well-known adsorption kinetic and isotherm models of sorbents were utilized to explain the mechanism of adsorption of oil onto the modified OPEFB fibre. The predicted result exemplified that, Pseudo-second-order model from the kinetic and Langmuir model from isotherm study were well represented to remove crude oil onto the treated OPEFB fibre regarding the highest correlation coefficient (R2) and closely of maximum crude oil adsorption in theoretical (q0) and experimental (qe) data.

The Challenge of Oil Spill Monitoring and Control in Nigeria

Oil has been a fundamental enabler of development. Be this as it may, the emergence of the green environment movement, catalyzed by the challenge of climate change, has called into question the significance of crude oil as a source of energy. This has necessitated the need to manage the environmental impact of oil. One area needing attention is oil spill monitoring and control. Several technological systems have been developed in order to monitor and subsequently control oil spills. These include acoustic emission sensoring, infrared sensoring, fibre optic sensoring, satellite remote sensoring and remotely-piloted aircrafts. Nigeria, where oil spill is a major challenge, requires an effective management of oil spills. In realization of this, regulatory agencies such as National Oil Spill Detection and Response Agency and detailed guidelines for effective oil spill monitoring and control have emerged. Be this as it may, weak regulation by government agencies has been exploited by oil companies and communities; resulting in frequent oil spills, large quantities of spilled oil, extensiveness of polluted areas and persistence of the impact of spilled oil. Oil spills occur frequently. For instance, there were 5,848 incidents resulting in the spillage of about 169,691 barrels of oil between 2010 and 2018. Spills occur in all parts of the oil producing region, the Niger Delta; resulting in its being commonly described as the most polluted area of the planet. The impact of spills is usually enduring because many spill sites are either not cleaned or cleaned ineffectively. Effective regulation and a more environment-friendly oil spill monitoring and control through technological applications are necessary.

THE BREAKTHROUGH TECHNOLOGY SOLUTIONS FOR CONTROL AND TREATMENT OIL SPILL ON THE SEA: A SHORT REVIEW

In recent years, all countries in the world are very interested in the effects of pollutants affecting human health, the living environment in general and especially pollution of water sources and oceans on the earth's surface. The cause of this pollution is largely due to human use of chemicals and fuels from many different sources, especially oil. The exploitation and transportation of crude oil are increasing according to the common development of humanity. Since people discovered and exploited oil, the oil spill at sea began to appear. Since ancient times, oil spills on the sea have been a threat to the marine environment in general, coastal ecosystems in particular and damage to economic activities. It is the concern of all humanity. Every year, we still have to witness many accidents from tankers making millions of tons of oil spilled into the sea, causing great consequences for the natural resources and environment on the earth. In order to overcome the oil spills on the sea, people have also found a way to deal with them, and many processing methods were created to overcome the above problems such as mechanical methods, chemical methods, biological methods. The application of scientific and technological advances in information technology and biotechnology have been creating breakthroughs in forecasting and controlling oil spills at sea. The paper focuses on an overview of pollution problems from ships, especially oil pollution from tankers and the consequences of oil pollution on the marine environment. Moreover, the authors learn and evaluate some specific advanced technology solutions to prevent oil pollution from ships, effective feasible solutions that need to be applied in practice.

Study of the Raveling Resistance of Porous Asphalt Pavements Used in Sustainable Drainage Systems Affected by Hydrocarbon Spills

Permeable pavements are one of the most commonly-used sustainable drainage systems (SuDS) in urban areas for managing stormwater runoff problems. Porous asphalt is widely used in surface layers of permeable pavement systems, where it can suffer from accidental oil spills from vehicles. Oil spills affect bituminous mixes through the solvent action of the hydrocarbons on the bitumen, reducing the raveling resistance of asphalt pavements. In order to assess the raveling resistance in porous asphalt pavements, the Cantabro abrasion test was performed on 200 test samples after applying controlled oil spills. Three different types of binders were used: conventional bitumen, polymer-modified bitumen and special fuel-resistant bitumen. After analyzing the results, it was concluded that the most suitable bitumen to protect against oil leakages is the polymer-modified one, which is far better than the other two types of bitumen tested.

Application of Strong Porous Polymer Sheets for Superior Oil Spill Recovery

AbstractThe usage of natural and synthetic sorbents in order to control oil spills is gaining increasing attention due to environmental concerns. In particular, polyolefins including polypropylene and polyethylene are the most commonly used oil sorbent materials because of their low cost but suffer from low oil absorption capacity. Attempts at trying to increase the surface‐to‐thickness ratio for improving uptake capacity makes them vulnerable to breakage and impractical for most oil spill applications. Novel super oil sorbent polymer sheets consisting of porous ultrahigh‐molecular‐weight polyethylene have been prepared. The presented sorbent exhibits extremely high uptake and retention capacities along with a mechanically strong structure. The combination of these factors as well as the cost effectiveness of the material used makes these sheets viable candidates for widespread production and utilization.

Study of Oil spill in Norwegian area using Decomposition Techniques on RISAT-1 Hybrid Polarimetric Data.

Abstract. Over past few years Synthetic Aperture Radar(SAR) has received a considerable attention for monitoring and detection of oil spill due to its unique capabilities to provide wide-area surveillance and day and night measurements, almost independently from atmospheric conditions. The critical part of the oil spill detection is to distinguish oil spills from other natural phenomena. Stokes vector analysis of the image data is studied to estimate the polarized circular and linear components of the backscatter signal which essentially utilize the degree of polarization(m) and relative phase (δ) of the target. In a controlled oil spill experiment conducted at Norwegian bay during 17th to 22nd June 2014, RISAT-1 hybrid polarimetry images were utilized to study the characteristics of oil spill in the sea. The preliminary results obtained by using polarimetric decomposition technique on hybrid polarimetric data to decipher the polarimetric characteristics of oil spills from natural waters are discussed in the paper.

Biosurfactant Producing Microbes and their Potential Applications: A Review

Biosurfactants are surface-active biomolecules produced by microbes (bacteria, fungi, and yeast) and have several advantages over the chemical surfactants, such as lower toxicity, higher biodegradability, better environmental compatibility, higher foaming, high selectivity, and specific activity under extreme conditions such as temperature, pH, and salinity. Almost all the surfactants now available in the market are chemically synthesized. Recently, attention toward the biosurfactants was doubled, which is mainly due to their wide range of functional properties and the diverse synthetic capabilities of the microbes. Microbial biosurfactants are found to have a wide range of applications in environmental protection, which include enhancing oil recovery, controlling oil spills, biodegradation, and detoxification of oil-contaminated industrial effluents and soils. Biosurfactants produced by microorganisms have potential applications in pharmaceutical/medicine, food, cosmetic, pesticide, oil, and biodegradation industries. In this review article, we concentrated on three important aspects such as various types of biosurfactants, the group of microbes involved in the production of biosurfactants, and application of microbial biosurfactants.

Characterization of Marine Surface Slicks by Radarsat-2 Multipolarization Features

In this paper, we study surface slick characterization in polarimetric C-band synthetic aperture radar (SAR) data. The objective is to identify the most powerful multipolarization SAR descriptors for mineral oil spill versus biogenic slick discrimination. A systematic comparison of eight well-known multipolarization features is provided. The analysis is performed on data that we collected during a large-scale oil spill exercise at the Frigg field situated northwest of Stavanger, in June 2011. Controlled oil spills and simulated look-alikes were simultaneously captured within fine quad-polarization Radarsat-2 acquisitions during this experiment. Multipolarization features derived from only the copolarized complex scattering coefficients are explored. We find that the two most powerful multipolarization features extracted from this data set are the geometric intensity, measuring the combined intensity based on the determinant of the coherency matrix, and the real part of the copolarization cross product, which is related to the scattering behavior of the target. We show that these two features can distinguish between the simulated biogenic slicks and mineral oil types such as Balder and Oseberg blend, and that the discriminative power seems to be persistent with time.

Differential responses of a benthic meiofaunal community to an artificial oil spill in the intertidal zone

This study aimed to determine the potential impact of an oil spill on intertidal meiofauna at a clean, sandy beach in Korea. This objective was accomplished by examining changes in the structure of meiofaunal assemblages after a controlled oil spill of different concentrations on the beach. The concentration of total petroleum hydrocabon (TPH) in the experimental plots after oil application was expectedly higher for the first 4 d compared to before oil application. The TPH concentrations decreased at a faster rate in the first 4 d, and then progressively. The sharp decline in meiofaunal density in the experimental plots during the first 4 d after the spill might be attributed to the short-term toxic effects of the oil. This suggestion is supported by a significant negative interaction of the TPH on meiofaunal density during the study period. The period of low density of meiofauna also coincided with the maximum concentration of TPH in the sediment. The multivariate indices proved to be highly efficient, showing that samples contaminated with oil had high TPH concentrations, and were partially separated in terms of meiofaunal communities from samples before oil application or samples with low TPH concentrations. The structure of the meiofaunal communities in the experimental plots was similar before and 1 month after oil application. However, the density of meiofauna sharply decreased immediately after oil application in the experiment plots. Furthermore, the meiofaunal density recovered slowly as time passed.

Airborne Lidar Measurements of a Smoke Plume Produced by a Controlled Burn of Crude Oil on the Ocean.

An airborne lidar was used to study the smoke plume from the burning of a controlled oil spill on the ocean. The ratio of the amount of light (at a wavelength, λ, of 0.532 u.m) backscattered by the smoke to the amount of light extinguished by the smoke was determined by measuring the strength of a laser beam after it had passed through the smoke plume, been reflected from the ocean, and passed through the smoke plume again, and comparing this to the strength of the laser beam reflected directly from the ocean. The optical depth of the smoke (at λ = 0.532 µm) was typically between 0.2 and 0.5. The mass fluxes of smoke particles that passed through four vertical cross sections of the (nonsteady state) smoke plume were estimated from lidar measurements to be 142, 175, 423, and 414 g s-1, compared to an average smoke mass production rate of ~770 g s-1. The spatial distribution of smoke mass along the long axis of the plume was also estimated from the lidar measurements; derived smoke mass concentrations were generally <300 µg m-3, with a few isolated values up to ~800 µg m-3.

Field Trials ofin-situOil Spill Countermeasures in Ice-Infested Waters

An oil spill response technique in ice-infested waters based on the application of fine minerals in a slurry with mixing by propeller-wash to promote the formation of oilmineral aggregates (OMA) has been proposed. This process promotes the physical dispersion of mineral-fine stabilized oil droplets into the water column that support higher rates of oil degradation by natural bacteria. To validate the operational effectiveness of this technique a controlled oil spill experiment was conducted from a Canadian Coast Guard ice-breaker in the St. Lawrence Estuary (offshore of Matane, Quebec, Canada). Following the release of the test crude oil and the application of experimental treatments, time-series changes in oil concentrations were monitored to quantify dispersion effectiveness. Field samples were also recovered for laboratory microcosm studies on the biodegradation of petroleum hydrocarbons by monitoring CO2 production and the depletion of specific hydrocarbon components. Detailed chemical analysis (GC/MS with hopane normalization) from these studies showed that more than 60% of the total petroleum hydrocarbon, 75-88% of total alkanes, and 55-65% total PAHs, were degraded after 56 days of incubation at 0.5 o C. The alkylated PAH was degraded to a greater extent following the addition of mineral fines. This technique offers several operational advantages as a spill countermeasure for use under Arctic conditions such as reduced numbers of personnel required for its application, no need for waste disposal sites, and cost effectiveness.

Controlling Oil Spills in Fast Currents with the Flow∼Diverter

ABSTRACT Sixty nine percent (645 million tons annually) of the oil transported in United States waters is on waterways where currents routinely exceed one knot. Conventional skimmers and booms lose their effectiveness when current speeds exceed 1 knot. The US Coast Guard recognized that this threat could not be easily controlled, and so they initiated a project that led to the successful development of a novel spill control device, the Oil Spill Flow~Diverter. The Flow~Diverter system is effective at diverting and converging oil at speeds up to 5+ knots. In more moderate currents it can also be used in place of an anchor, towboat or outrigger arm to deploy and position the outboard end of a deflection boom. It may also have application to dispersant and in-situ burn operations. The diverter is a unique stable catamaran design that consists of two hulls each comprised of symmetrical foils with integral buoyancy. The foils are pinned to a rigid connecting structure such that they can pivot but always remain parallel to each other. Two or more diverter catamarans can be connected together with cables to increase the total sweep width of the system. Two control lines are anchored to shore or secured to a boat and are used to deploy the system by adjusting the foils’ angle to the oncoming water. With the control lines securely anchored, the system is launched into the current and “flies out” into a stable operating position. It remains in equilibrium, balanced by the hydrodynamic lift forces of the passing water and the tension in the lines. The foils create a strong transverse surface current downstream to achieve the desired diversion and consolidation affect on floating oil. Unlike most skimmers and deflection boom, the diverters are not adversely affected as currents increase. The oil is diverted by the same lateral distance irrespective of the current or speed of advance. This paper presents the development of the Flow~Diverter prototype, its testing and operational evaluations. Several applications of the diverter technology in various response tactics are discussed. Use of the Diverter during a recent US Coast Guard Spill Exercise on the Ohio River is also presented. Production model enhancements are presented that will enhance performance in 7+ knot currents and shallow water applications.

Indigenous Sediment Microbial Activity in Response to Nutrient Enrichment and Plant Growth Following a Controlled Oil Spill on a Freshwater Wetland

Indigenous Sediment Microbial Activity in Response to Nutrient Enrichment and Plant Growth Following a Controlled Oil Spill on a Freshwater Wetland

Indigenous Sediment Microbial Activity in Response to Nutrient Enrichment and Plant Growth Following a Controlled Oil Spill on a Freshwater Wetland

The population density and activity of a microbial community associated with the sediment and rhizosphere of an intertidal freshwater wetland dominated by Scirpus pungens was monitored before and following the application of weathered Mesa light crude oil and fertilizers. The influence of nutrient enrichment (fertilizers) and plant growth on oil degradation rates was determined from the resulting data. The study plots (four blocks of replicates) were subjected to five treatments: oil only (natural attenuation); oil plus ammonium nitrate and phosphate, with regular cropping of the plants; oil plus ammonium nitrate and phosphate; oil plus sodium nitrate and phosphate; no oil, ammonium nitrate and phosphate. The plots were regularly monitored in the field for gas production (carbon dioxide and nitrous oxide), and samples were collected for laboratory analysis of denitrification activity, aliphatic and aromatic hydrocarbon degradation activity, and total heteroptrophic bacteria.The viable bacterial population density increased during the first 4 weeks in oiled and unoiled experimental plots that were fertilized. In contrast, population densities in untreated areas remained relatively unchanged throughout the monitoring period. The microbial population demonstrated a rapid and sustained increase in naphthalene mineralization activity in plots that were both fertilized and oiled. Hexadecane mineralization activity increased in response to fertilizer application, with ammonium nitrate causing a larger increase than sodium nitrate. A very significant difference observed in the mineralization of hexadecane was that the surface sediments were much more active than the subsurface sediments. This difference became even more pronounced in the second year of monitoring, even though the treatment regime had been discontinued. This compartmentalization of mineralization activity was not observed for naphthalene. Following fertilizer application, field and laboratory evaluation of nitrogen metabolism in the sediments indicated significant denitrification activity that was not adversely affected by oiling. The results demonstrated that the application of fertilizers stimulated the activities of indigenous hydrocarbon-degrading and denitrifying bacteria, and the presence of oil either enhanced or had no detrimental effect on these activities. As a remediation strategy, the application of fertilizers to a wetland shoreline following an oil spill would promote the growth of indigenous plants and their associated microbial flora, resulting in increased metabolic activity and the potential for increased oil degradation activity.

Indigenous Sediment Microbial Activity in Response to Nutrient Enrichment and Plant Growth Following a Controlled Oil Spill on a Freshwater Wetland

The population density and activity of a microbial community associated with the sediment and rhizosphere of an intertidal freshwater wetland dominated by Scirpus pungens was monitored before and following the application of weathered Mesa light crude oil and fertilizers. The influence of nutrient enrichment (fertilizers) and plant growth on oil degradation rates was determined from the resulting data. The study plots (four blocks of replicates) were subjected to five treatments: oil only (natural attenuation); oil plus ammonium nitrate and phosphate, with regular cropping of the plants; oil plus ammonium nitrate and phosphate; oil plus sodium nitrate and phosphate; no oil, ammonium nitrate and phosphate. The plots were regularly monitored in the field for gas production (carbon dioxide and nitrous oxide), and samples were collected for laboratory analysis of denitrification activity, aliphatic and aromatic hydrocarbon degradation activity, and total heteroptrophic bacteria.The viable bacterial population density increased during the first 4 weeks in oiled and unoiled experimental plots that were fertilized. In contrast, population densities in untreated areas remained relatively unchanged throughout the monitoring period. The microbial population demonstrated a rapid and sustained increase in naphthalene mineralization activity in plots that were both fertilized and oiled. Hexadecane mineralization activity increased in response to fertilizer application, with ammonium nitrate causing a larger increase than sodium nitrate. A very significant difference observed in the mineralization of hexadecane was that the surface sediments were much more active than the subsurface sediments. This difference became even more pronounced in the second year of monitoring, even though the treatment regime had been discontinued. This compartmentalization of mineralization activity was not observed for naphthalene. Following fertilizer application, field and laboratory evaluation of nitrogen metabolism in the sediments indicated significant denitrification activity that was not adversely affected by oiling. The results demonstrated that the application of fertilizers stimulated the activities of indigenous hydrocarbon-degrading and denitrifying bacteria, and the presence of oil either enhanced or had no detrimental effect on these activities. As a remediation strategy, the application of fertilizers to a wetland shoreline following an oil spill would promote the growth of indigenous plants and their associated microbial flora, resulting in increased metabolic activity and the potential for increased oil degradation activity.

Microbial Population Analysis as a Measure of Ecosystem Restoration

During a controlled oil spill study in a freshwater wetland, four methods were used to track changes in microbial populations in response to in situ remediation treatments, including nutrient amendments and the removal of surface vegetation. Most probable number (MPN) estimates of alkane and aromatic hydrocarbon degraders showed divergence of the alkane and aromatic degrading populations during the first summer of the experiment. Alkane degraders increased in all plots by 1.5 orders of magnitude and aromatic degraders increased in oiled plots by 3.5 orders of magnitude. Phospholipid fatty acid (PLFA) analysis of biomass and community composition showed no essential differences among treatments. Denaturing gradient gel electrophoresis (DGGE) analysis of the sediment microbial community showed some differences in specific populations of organisms with respect to oiled and unoiled plots. Some organisms were only found in the oiled plots. Sediment toxicity measured against single celled algae showed that the oiled sediments were toxic into the second year of the study, but that nutrient addition relieved the toxicity more rapidly than natural attenuation of the oil.