Oil Plots Research Articles

Agrochemical inputs to managed oil palm plantations are a probable risk to ecosystems: Results from a screening level risk assessment

Palm oil is a high value crop widely grown in the tropics. The management of palm oil is characterised by widespread agrochemical use. Here we report the results of a screening level risk assessment conducted from the available literature on the environmental concentration of agrochemicals in surface waters and soils in palm oil growing areas. To date, only a small number of published studies have measured pollutant concentrations in and around palm oil plantations. To identify potential high-risk contaminants, a standard SSD based risk assessment, establishing risk quotients for detected contaminants, was conducted in relation to available species sensitivity distributions. A probabilistic SSD based risk assessment, calculating potential risk distributions, was also conducted for contaminants with the required number of data points available. Metals were the most commonly detected (and measured) substances and also presented the greatest risk, especially copper and zinc, but also nickel, lead and cadmium. For these metals, environmental concentrations overlapped levels found to cause effects in toxicity studies, indicating the potential for adverse outcomes from exposure. To fully understand the extent of this risk, more detailed studies are needed that assess metal speciation states and bioavailability under the prevailing soil and water chemistry conditions in palm oil plots. Limited studies have measured pesticide concentrations in palm oil systems. In these few cases, only a few active substances have been measured. From the limited information available, potential risks are indicated due to the presence of some insecticides. However, fungicides are also widely used for palm oil disease management, but little data studies are available to assess both exposure and potential effects. To further assess the potential chemical footprint of different palm oil management practices, studies are needed that systematically assess pollutant levels across a range of chemical groups to consider effects within a mixture context.

Evaluation of soil fauna biodiversity in restored farmland for protection of wetland ecology by planting different crops

Wetlands play a crucial role in oxygen production, air purification, and quality maintenance. Thus, conservation of wetland is essential in response to natural and anthropogenic damaging activities. Restored farmland, utilized to repair the southern buffer zone of Jiangsu Yancheng Wetland National Nature Reserve for Rare Birds, was used to investigate and analyze the diversity of migratory birds and soil fauna. In this study, five different crops, colza oil, mustard, Chinese cabbage, wheat, and barley, were planted in the restored plots, which were foraged by overwintering migratory birds, resulting in low crop yield. The soil fauna biodiversity and biomass in the wheat, Chinese cabbage, and colza oil plots during winter were relatively rich, which attracted many migratory birds to roost and feed. The variability and population of migratory birds significantly improved (18 species and 164231 migratory birds), which was owed to soil fauna and planted crops. Therefore, based on the results of our study, farmland restoration could significantly enrich the biodiversity of soil fauna and migratory birds, improve the ecological environment of wetlands, and attract more migratory birds as inhabitants.

The Oil Industry in Galicia until 1918 in Light of the Records of the Galician Governorate in Lviv

The files kept at the Central State Historical Archive of Ukraine in Lviv are of fundamental importance for research into the issues of the oil industry in Galicia. Of particular note is the largest ensemble in the archive – fond 146: Galician Governorate in Lviv, containing the records of the central government of Galicia. This collection has preserved a rich collection of materials representing various aspects of the development of the oil industry. They dealt with issues of the occurrence of crude oil in Galicia, the acquisition and exploitation of oil plots, the extraction and processing of oil, and the construction and operation of wells and refineries. The information on the state of the oil mines in Galicia, especially in terms of meeting technical conditions, fire protection and occupational safety, is valuable. An important place is held by files depicting issues of the creation of industrial infrastructure, including the construction and maintenance of oil pipelines, the construction of storage facilities, and the railway connection to the plants. The files also contain information on the establishment and activities of domestic and foreign oil companies and joint stock companies in Galicia. Also of interest are materials on the development of the labour movement. Keywords: records of the Galician Governorate in Lviv, kerosene, oil industry, mines, oil companies and joint stock companies.

The abundance of soil invertebrates in young and mature palm oil plot in relations to soil physical properties: A preliminary study

The soil biota is considered the biological engine of the earth and is associated with most of the critical functions of the soil in terms of ecosystem services. The knowledge on the impact of land management and agricultural activities on the abundance and diversity of soil invertebrates is still understudied especially in Malaysia. This study was conducted to investigate the relation of the abundance and diversity of soil invertebrates with the soil physical parameters from two different palm oil plots. Sampling methods of soil invertebrates include pitfall trap and Burlese-Tullgren funnel. Invertebrate’s abundance and diversity were measured and invertebrates were identified according to their morphological characteristics under the dissecting microscope concerning taxonomic keys. A total of 621 individuals were documented from both sites with 408 collected in mature palm oil farms whereas 213 individuals were documented in young palm oil farms. Hymenoptera (67.31 %) is the most dominant invertebrate followed by Orthoptera (12.40 %) and Arachnida (10.14 %). Morphospecies diversity, evenness, and richness are highest in mature palm oil plot with Shannon; 1.54, Evenness; 0.32, and Menhinick; 0.67 respectively. Well-developed canopy, plenty of shelters, and reduced agricultural activities in mature palm oil mainly contributed to ideal soil physical parameters (bulk density; 1.23 (g/cm3) ± 0.02, porosity; 55.03 % ± 2.48, temperature; 35.65°C ± 0.30 and moisture; 34.05 % ± 0.60) produces a comparatively more balanced habitat for a diverse community of soil invertebrates. Because of the roles they play in soil biological processes, soil invertebrates may be used as bioindicators of soil health. This study can be used as a baseline for more extensive research that may be applied in future planning on land management in achieving the nation’s agricultural sustainability.

Clonal integration in Phragmites australis alters soil microbial communities in an oil-contaminated wetland

Clonal plants can share information and resources among connected ramets (asexual individuals). Such clonal integration can promote ramet growth, which may further influence soil microbial communities in the rooting zone. Crude oil contamination can negatively affect plant growth and alter soil microbial community composition. However, we still know little about how clonal integration affects soil microbial communities, especially under crude oil contamination. In a coastal wetland, ramets of the rhizomatous plant Phragmites australis in circular plots (60 cm in diameter) were subjected to 0, 5 and 10 mm depth of crude oil, and the rhizomes at the edge of the plots were either severed (preventing clonal integration) or left intact (allowing clonal integration). After three years of treatment, we analysed in each plot soil physiochemical properties and soil microbial community composition. The alpha-diversity of the soil microbial communities did not differ between intact and severed plots, but was overall lower in 10-mm than in 0-mm and 5-mm oil plots. Considering all three oil treatments together, soil microbial community dissimilarity (beta-diversity) was positively correlated with soil property distance in both severed and intact plots. Considering the three oil treatments separately, this pattern was also observed in 10-mm oil plots, but not in 0-mm or 5-mm oil plots. The soil microbial community composition was more sensitive to the oil addition than to the clonal integration. Moreover, the relative abundance of the nitrogen-cycling bacterial taxa was lower in intact than in severed plots, and that of the oil-degrading bacterial taxa increased with increasing oil-addition levels. Our results indicate that clonal integration and oil contamination can influence soil microbial communities independently through changing the relative abundance of the component bacteria taxa, which has important implications for ecosystem functions of the soil food web mediated by clonal plants.

Applications of quick look methods for evaluating the Middle Miocene Jeribe Formation from a selected well in Jambour Oilfield, Kurdistan Region, northern Iraq

Quick look methods (QLM) in log interpretation are helpful to the geologist because they provide flags, or indicators, that point to possible hydrocarbon zones. The importance of QLM is in their ability to provide information about the nature of the fluids in the pore spaces and the lithology of the reservoirs in a quick and simple way. Four ways of QLM are applied on the Middle Miocene Jeribe Formation from the well Ja-49 in Jambour Oilfield. The apparent water resistivity (Rwa) method helped in quick detecting the hydrocarbon-bearing zones of the formation. The logarithmic movable oil plot method assisted in detecting the intensity of the movability of the hydrocarbons within the hydrocarbon-bearing zones of the formation. The SP versus Rxo/Rt overlay is an additional helpful way for detecting water and hydrocarbon-bearing horizons without need to know porosity. movable hydrocarbon index (MHI) is also used as QLM for detecting the movability of the hydrocarbons through calculating the ratio of water saturation in the uninvaded zone to that of the flushed zone. Accordingly, the formation in the studied well appeared to be generally a hydrocarbon-bearing reservoir with zones of different movable hydrocarbon potentiality. The application of MHI method indicated that about 53% of the gross 56 m thickness of the formation contains movable hydrocarbons. The upper and lower 5 m of the formation appear to be containing the most efficient productive horizons. No actual oil water contact is observed in the studied section of Jeribe Formation, which means the oil column extends down to certain depth in the formations underlying Jeribe Formation.

Bioefficacy of different insecticides against blister beetle Mylabris phalerata (Pallas) on pigeonpea

The experiment was accomplished to evaluate the bioefficacy of different insecticides against Mylabris phalerata (Pallas) on pigeonpea. The experiment consisted of seven treatments viz., bifenthrin 62 g a.i. ha-1, lambda-cyhalothrin 24 g a.i. ha-1 (encapsulated with polymers; Matadore), chlorpyriphos 310 g a.i. ha-1+ cypermethrin 31 g a.i. ha-1, cypermethrin 62 g a.i. ha-1, neem oil 1500 ppm, permethrin 154 g a.i. ha-1, chloropyriphos 173 g a.i. ha-1 compared with untreated (control). The sixth day after each spray, minimum population abundance of M. phalerata and maximum percent efficacy in reducing their population was obtained from bifenthrin which was at par with lambda-cyhalothrin, cypermethrin, chlorpyriphos+ cypermethrin and permethrin and all these were significantly effective over chloropyriphos, neem oil and control plots. On the tenth day after each spray, minimum population abundance and highest per cent efficacy were obtained from bifenthrin which was at par with lambda-cyhalothrin and both these treatments were significantly superior over rest of the treatments. The maximum productivity was observed with bifenthrin, while highest net return per rupee investment was obtained from lambda-cyhalothrin treatment. The results explicitly show that out of all treatments, Lambda-cyhalothrin was effective and imposing lucrative against M. phalerata and thereby minimized the yield loss. Three sprays of lambda-cyhalothrin and bifenthrin with an interchange at ten days interval will be effectual and lucrative against M. phalerata in short duration pigeonpea crop.SAARC J. Agri., 15(1): 55-65 (2017)

Fluid prediction using AVO analysis and forward modelling of deep reservoirs in Faith Field, Niger Delta, Nigeria

Amplitude versus offset AVO analysis and forward modelling were used to predict the fluid type and seismic signature in a deep gas reservoir in faith field, Niger Delta. Well A, which identified the major deeper gas bearing reservoir in this field, was used in the modelling to predict what the seismic response would be away from this well at varying thickness and porosity ranges. The entire well was blocked into alternate layers of sand and shale lithotypes; the sands were fluid substituted from its initial in situ condition to 100 % brine saturation, and from the brine case, fluid substituted to 100 % oil and 100 % gas saturations. The elastic properties of these fluid substituted sands were estimated using the Gassmann equations and Batzle and Wang. The results were used in AVO analysis. Seismic forward modelling to determine the seismic wiggle signatures of these sands were also conducted. The variations of pertinent rock properties with depth of burial were also investigated. The results show that sand alpha (interval 10,400–10,650 ft) exhibited a typical class 3 AVO signature. Seismic wiggle response from top of this sand shows a distinct negative trough on the near angle stack and a much larger trough on the far stack. Sand beta (interval 11,700–12,050 ft) exhibited a typical class 2n AVO signature. Sand wedge model response shows increasing amplitudes from tops and bases of these sands as a function of thickness with the limits of seismic resolution shown by the tuning thickness. The gradient-stack plots, Hiltermann’s acoustic impedance (HAI) versus Poisson’s ratio (PR) plots and the AVO models suggest that the hydrocarbon-bearing sands will be distinguishable from sands with 100 % brine saturations. There is significant overlap between oil and gas plots because the oil was modelled as having a high gas oil ratio (GOR) of 3,586. The reservoirs at this level in Faith Field are either condensate or gas bearing. Seismic direct hydrocarbon indicator (DHI) and lithologic delineation are better defined in the shallower sand alpha than the deeper sand beta. These models have shown that any good quality seismic acquired over this prospect would be useful in deriving reservoir properties from seismic (RPFS) for these reservoirs and would be effective in lithologic differentiation or hydrocarbon identification.

Salt Marsh Remediation and the Deepwater Horizon Oil Spill, the Role of Planting in Vegetation and Macroinvertebrate Recovery

ABSTRACTThe Deepwater Horizon oil spill resulted in persistent heavy oiling in salt marshes, particularly in northern Barataria Bay, Louisiana. Oiling conditions and several ecological variables were compared among reference plots and three types of heavily oiled plots located along a continuous shoreline area in northern Barataria Bay: oiled control plots, mechanical treatment plots, and mechanical treatment plots coupled with vegetation planting (Spartina alterniflora). Data were collected more than three years following initial oiling and two years following cleanup treatments and planting. Salt marsh oiling and associated impacts were apparent across all oiling/treatment classes relative to reference conditions. Mechanical treatment with planting showed the most improvement in oiling conditions and was also effective in re-establishing vegetation cover and plant species composition similar to reference conditions, in contrast to the oiled controls and mechanical treatment plots without planting. Marsh periwinkle (Littoraria irrorata) recovery was limited across all oiling/treatment classes relative to reference. Impacts to fiddler crabs (Uca spp.) were also documented in the heavily oiled plots. Positive influences of mechanical treatment and planting on macroinvertebrate recovery were observed; however, invertebrate recovery may lag the return of Spartina alterniflora by several years. Vegetation planting should be considered as a spill response and emergency restoration option for heavily oiled salt marshes where vegetation impacts are substantial, natural recovery may be lacking or delayed, intensive cleanup treatments are used, or where marsh shorelines are at risk of erosion.

The use of toxicity bioassays to monitor the recovery of oiled wetland sediments.

Six toxicity assays were compared to determine their efficacy in assessing toxicity dynamics during a wetland bioremediation study. The toxicity bioassays used were the Microtox 100% elutriate test, Microtox Solid Phase Test (SPT), amphipod assay, P450 reporter gene system, Toxi-ChromoPad test and a Salmonella/microsome assay. Oiled sediments were analyzed for toxicity in the petroleum biostimulation experiment conducted along the San Jacinto River, near Houston (TX, USA). The bioassays were evaluated for their ability to measure acute toxicity, chronic toxicity, and the mutagenic potential of amended oiled plots as compared to oiled and unoiled control plots. Amendments were diammonium phosphate alone or in combination with potassium nitrate, which served as an alternate electron acceptor. With exception of the Toxi-ChromoPad and Salmonella tests, the bioassays exhibited a significant increase in toxicity after oil application. Microtox bioassays detected significant sediment toxicity up to 29 d after oil and amendment application. The Microtox solid phase test results correlated strongly with gas chromatography-mass spectrometry analyses of total target saturate and aromatic hydrocarbons. The amphipod assay detected initial toxicity with a decline to day 70, followed by a significant increase in toxicity on day 140 in plots receiving nutrient amendments, which may be in response to excessive nutrient application. Low levels of enzyme induction were observed with the P450 reporter gene system assay in all oiled sediments throughout the study, suggesting low but persistent levels of polycyclic aromatic hydrocarbons. Of the six tests, the two Microtox tests and the amphipod test showed the most potential in evaluating petroleum toxicity in wetland sediments.

The Reduction of Stranded Oil by In Situ Shoreline Treatment Options

The Svalbard Shoreline Field Trials quantified the effectiveness of sediment relocation, mixing, bioremediation, bioremediation combined with mixing, and natural attenuation as options for the in situ treatment of oiled mixed-sediment (sand and pebble) shorelines. These treatments were applied to oiled plots located in the upper beach at three experimental sites, each with different sediment character and wave-energy exposure. Systematic monitoring was carried out over a 400-day period to quantify oil removal and to document changes in the physical character of the beach, oil penetration, oil loading, movements of oil to the subtidal environment, biodegradation, toxicity, and to validate oil-mineral aggregate formation. The results of the monitoring confirmed that sediment relocation significantly accelerated the rate of oil removal and reduced oil persistence where oil was stranded on the beach face above the level of normal wave activity. Where the stranded oil was in the zone of wave action, sediment relocation accelerated the short-term (weeks) rate of oil loss from the intertidal sediments. Oil removal rates on a beach treated by mechanical mixing or tilling were not significantly higher than those associated with natural recovery. However there is evidence that mixing/tilling may have enhanced microbial activity for a limited period by increasing the permeability of the sediment. Changes in the chemical composition of the oil demonstrated that biodegradation was significant in this arctic environment and a bioremediation treatment protocol based on nutrient enrichment effectively doubled the rate of biodegradation. However, on an operational scale, the success of this treatment strategy was limited as physical processes were more important in causing oil loss from the beaches than biodegradation, even where this oil loss was stimulated by the bioremediation protocols.

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.

Microbial Dynamics during Bioremediation of a Crude Oil-Contaminated Coastal Wetland

In 1996, a controlled crude oil application was conducted at a Texas intertidal, coastal wetland to determine the effectiveness of two biostimulation treatments in these sensitive areas. An inorganic nutrient treatment and inorganic nutrient plus a potential electron acceptor (nitrate) treatment were examined. As part of this research, polycyclic aromatic hydrocarbon (PAH)-degrading, aliphatic-degrading, and total heterotrophic microbial numbers were monitored. Using a randomized, complete block design consisting of 21 plots, microbial data from biostimulation treatment plots were statistically compared to oiled control plots to assess treatment differences. Sediment samples from all plots receiving oil showed exponential increases in the numbers of aliphatic (n-alkane) and PAH-degrading microorganisms. This increase was observed at both 0 to 5 cm and 5 to 10 cm sample depths. Statistical analysis, however, revealed no significant differences in the numbers of aliphatic-degrading or PAH-degrading microorganisms between treatment plots and oiled control plots or between treatments on any sample day. The numbers of PAH- and aliphatic-degrading microorganisms returned to near pre-application levels by the end of the monitoring period. Ratios of hydrocarbon-degrading microbes to total heterotrophs also increased as a result of the oil application and returned to pre-application levels by the end of the monitoring period. Overall, the populations of hydrocarbon-degrading microorganisms illustrated a well-documented response to crude oil. However, the addition of the biostimulation treatments did not significantly increase the numbers of aliphatic-degrading, PAH-degrading, or total heterotrophic microorganisms over populations on control plots.

Effect of Bioremediation on the Microbial Community in Oiled Mangrove Sediments

Bioremediation was conducted in the field on a mature Rhizophora stylosa mangrove stand on land to be reclaimed near Fisherman’s Landing Wharf, Gladstone Australia. Gippsland crude oil was added to six large plots (>40 m 2) and three plots were left untreated as controls. Bioremediation was used to treat three oiled plots and the remaining three were maintained as oiled only plots. The bioremediation strategy consisted of actively aerating the sediment and adding a slow-release fertilizer in order to promote oil biodegradation by indigenous micro-organisms. Oil addition stimulated the numbers of alkane-degrading bacteria slightly to levels of 10 4–10 5/g sediment. Bioremediation of the oiled sediment had a marked effect on the alkane-degrading population, increasing the population size by three orders of magnitude from 10 5 to 10 8 cells/g of sediment. An effect of bioremediation on the growth of aromatic-degraders was detected with numbers of aromatic-degraders increasing from 10 4 to 10 6 cells/g of sediment. Active aeration and nutrient addition significantly stimulated the growth of hydrocarbon-degraders in oiled mangrove sediment in the field.

Distributions of methylated naphthalenes in crude oils: indicators of maturity, biodegradation and mixing

Variations in the distributions of trimethylnaphthalenes (TMNs), tetramethylnaphthalenes (TeMNs) and pentamethylnaphthalenes (PMNs) were studied in a set of crude oils, which differ mainly in their level of maturity. Comparison with mixtures obtained after heating methylated naphthalenes with clay led to the proposal of three new parameters, one for each class of naphthalenes. Each parameter is based on the same principle, which is the increase with maturity of stable isomers relative to less stable ones. It appears that the relationships between these three parameters are linear for those oils where thermal stress alone has determined the distributions. These relations can be conveniently displayed in a ternary diagram. It is proposed that when an oil plots in the restricted area in the diagram that is defined by these linear relations, the so-called maturity centre, the value of any of the three parameters is an accurate indication of its thermal maturity. When an oil plots outside the maturity centre, factors like in-reservoir mixing, biodegradation or mixing with indigenous organic matter have distorted the distributions of methylated naphthalenes. It is thought that the distributions of methylated naphthalenes reflect the extent to which 1,2-methylshifts and methyl transfer reactions, mediated by clay catalysis, have taken place. It is proposed that the methyl groups involved in these reactions form a ‘methyl pool’ to which most compounds present will have access. Increasing temperature and availability of suitable catalysts can remove methyl groups from this pool through formation of very stable compounds such as methane, leading to a decrease in the degree of methylation of aromatic hydrocarbons.

Weathering of hydrocarbons in mangrove sediments: testing the effects of using dispersants to treat oil spills

This field study was a combined chemical and biological investigation of the relative effects of using dispersants to treat oil spills impacting mangrove habitats. The aim of the chemistry was to determine whether dispersant affected the short- or long-term composition of a medium range crude oil (Gippsland) stranded in a tropical mangrove environment in Queensland, Australia. Sediment cores from three replicate plots of each treatment (oil only and oil plus dispersant) were analyzed for total hydrocarbons and for individual molecular markers (alkanes, aromatics, triterpanes, and steranes). Sediments were collected at 2 days, then 1, 7, 13 and 22 months post-spill. Over this time, oil in the six treated plots decreased exponentially from 36.6±16.5 to 1.2±0.8 mg/g dry wt. There was no statistical difference in initial oil concentrations, penetration of oil to depth, or in the rates of oil dissipation between oiled or dispersed oil plots. At 13 months, alkanes were >50% degraded, aromatics were ∼30% degraded based upon ratios of labile to resistant markers. However, there was no change in the triterpane or sterane biomarker signatures of the retained oil. This is of general forensic interest for pollution events. The predominant removal processes were evaporation (≤27%) and dissolution (≥56%), with a lag-phase of 1 month before the start of significant microbial degradation (≤17%). The most resistant fraction of the oil that remained after 7 months (the higher molecular weight hydrocarbons) correlated with the initial total organic carbon content of the soil. Removal rate in the Queensland mangroves was significantly faster than that observed in the Caribbean and was related to tidal flushing.

Microbial population changes during bioremediation of an experimental oil spill.

Three crude oil bioremediation techniques were applied in a randomized block field experiment simulating a coastal oil spill. Four treatments (no oil control, oil alone, oil plus nutrients, and oil plus nutrients plus an indigenous inoculum) were applied. In situ microbial community structures were monitored by phospholipid fatty acid (PLFA) analysis and 16S rDNA PCR-denaturing gradient gel electrophoresis (DGGE) to (i) identify the bacterial community members responsible for the decontamination of the site and (ii) define an end point for the removal of the hydrocarbon substrate. The results of PLFA analysis demonstrated a community shift in all plots from primarily eukaryotic biomass to gram-negative bacterial biomass with time. PLFA profiles from the oiled plots suggested increased gram-negative biomass and adaptation to metabolic stress compared to unoiled controls. DGGE analysis of untreated control plots revealed a simple, dynamic dominant population structure throughout the experiment. This banding pattern disappeared in all oiled plots, indicating that the structure and diversity of the dominant bacterial community changed substantially. No consistent differences were detected between nutrient-amended and indigenous inoculum-treated plots, but both differed from the oil-only plots. Prominent bands were excised for sequence analysis and indicated that oil treatment encouraged the growth of gram-negative microorganisms within the alpha-proteobacteria and Flexibacter-Cytophaga-Bacteroides phylum. alpha-Proteobacteria were never detected in unoiled controls. PLFA analysis indicated that by week 14 the microbial community structures of the oiled plots were becoming similar to those of the unoiled controls from the same time point, but DGGE analysis suggested that major differences in the bacterial communities remained.

Bioremediation of Oil-Contaminated Fine Sediments

ABSTRACT Bioremediation of oil contamination has been shown to be effective for cobble and sandy shorelines. To assess the operational limitations of this technology, this project studied its potential to treat buried oil in fine sediments. The effectiveness of bioremediation by nutrient enrichment with water-soluble mineral fertilizers was quantified experimentally with a randomised block design with three replicate blocks. Each block consisted of an untreated control plot, a plot treated with fertilizer alone, an oiled plot, and an oiled plot treated with fertilizer. The sediment in each plot was retained in mesh enclosures and buried at a depth of 0.15 m. Weathered and emulsified Arabian Light crude oil was applied to the appropriate plots at 3.7 kg.m−−2. Bioremediation success was monitored by examining in situ CO2 production rates; changes in residual hydrocarbons normalized to 17?(H), 21?H)-hopane; and response of hydrocarbon-degrading microorganisms. Fertilizer treatments significantly increased the biodegradation of petroleum hydrocarbons (p = 0.0001) in the buried sediments. These conclusions were supported by in situ CO2 production data. Microbiological analyses showed that nutrient addition increased the numbers of hydrocarbon-degraders on the oiled plots tenfold. The results clearly showed that bioremediation can treat oil buried in fine sediment following a spill incident.

The Effect of Bioremediation on Microbial Populations in an Oil-Contaminated Coastal Wetland

ABSTRACT A series of controlled crude oil applications was carried out in a Texas coastal wetland to determine the effectiveness of bioremediation in these sensitive areas. The first application, conducted in 1996, was performed to assess the use of diammonium phosphate and diammonium phosphate plus a potential electron acceptor (nitrate) to stimulate microbial growth and subsequent hydrocarbon degradation. The second application, conducted in 1997, was performed to determine the potential of two commercial bioaugmentation products to enhance hydrocarbon biodegradation. Diammonium phosphate was also re-evaluated during this phase as a bio stimulation treatment. For both applications, sediment samples from all oiled test plots showed exponential increases in the numbers of aliphatic hydrocarbon and polycyclic aromatic hydrocarbon (PAH)-degrading microorganisms. Average numbers of aliphatic-degrading and PAH-degrading microorganisms were slightly higher (though not significantly higher) than populations on oiled control plots on most sample days. The bioaugmentation products and diammonium phosphate treatment examined during the second application did not significantly increase the numbers of hydrocarbon-degrading microorganisms (aliphatic-degraders or PAH-degraders). Overall, the microbial populations from both phases of research illustrated a well-documented response to a petroleum hydrocarbon input. Although the bioremediation treatments did not appear to significantly increase these populations, this data will be evaluated with nutrient and petroleum hydrocarbon data to determine the effectiveness of bioremediation in wetland areas.