Stephen M. Mudge

Lipid biomarkers in the Conwy Estuary (North Wales, U.K.): a comparison between fatty alcohols and sterols

Abstract Fatty alcohols (FAs) and sterols were quantified in surface sediment samples taken from Conwy Bay, the Conwy Estuary and in the freshwater tributaries of the river. Total FA concentrations ranged from ~ 230 to ~ 20,000 μg g −1 dry weight and the total sterols from 2.4 to 125 μg g −1 . In the marine samples, the short-chain C 16 FAs dominated although longer-chain, terrestrially derived moieties were also present. Samples from the freshwater sites had C 22 C 26 FAs present in the greatest concentration. A series of Alcohol Source Indices (ASI) based on the ratio between selected terrestrial FAs and marine FAs was developed on this basis. Other such ratios based on the short/long, odd/even and branched/ n -alkanol distribution highlighted regions of proposed bacterial diagenesis. Comparison was made to the traditionally used terrestrially derived sterols (β-sitosterol and stigmasterol) although the ergosterol (associated with decaying organic matter)/cholesterol ratio provided the best correlation to the ASI. A new sterol derived from the short-term diagenesis of ergosterol in mildly reducing conditions (ergosta 5,8(14),22 -trien-β-ol, proposed trivial name, munsterol) was identified in the lower estuarine site and Principal Components Analysis of the data indicates that a clearer separation of the geochemical sources can be seen with the sterols and suggests that the fatty alcohol provide more information on secondary processes rather than primary origins. On the basis of the biomarker profiles, the estuary was divided into the marine environment, the lower estuary dominated by sewage discharges and marine production, the upper estuary with increasing amounts of terrestrial organic matter, and the freshwater sites with terrestrially derived materials and sewage discharges.

Sewage contamination following an accidental spillage in the Ria Formosa, Portugal

Abstract Following an accidental spillage of sewage to the Ria Formosa in September, 1994, sediment samples were collected and analysed for sterols and fatty alcohols. Coprostanol concentrations ranged from 0.1 μg g −1 at sites remote from the spill, to 41.8 μg g −1 adjacent to the source. Use of the coprostanol/cholesterol ratio indicates the localized nature of the dispersion, only 2 km from the source. The distribution of fucosterol, ergosterol and fatty alcohols in the sediments are discussed. Principal Component Analysis using selected sterol and fatty alcohol ratios identified two major components describing the extent of sewage contamination and the marine-terrestrial nature of the organic matter.

Stimulating the Biodegradation of Crude Oil with Biodiesel Preliminary Results

Abstract Experiments using biodiesel derived from vegetable oils have demonstrated the considerable potential for removing crude oil from contaminated beaches. During laboratory studies in small boxes, contaminated sand treated with biodiesel also demonstrated the rapid biodegradation of the crude oil. Water soluble components were washed through the sand columns and these components subsequently precipitated with cold storage. This solid fraction was not soluble in organic solvents but could be re-dissolved in dilute acid. The sediments after four weeks were black in colour due to the precipitation of metal sulphides although no H 2 S was generated because the pH of the seawater kept the sulphides in solution. Further work is investigating which components of the oil were degraded and what products were formed.

Organic Contamination of San Vicente Bay, Chile

Abstract Surface sediment samples from 16 sites in San Vicente Bay were analysed for a range of lipid biomarkers and hydrocarbons. Coprostanol and cholesterol were used to indicate regions of sewage contamination: ratios reached 1.1 adjacent to known discharge points. The fatty alcohol data were used to highlight regions of bacterial and terrestrial biomass. The bacterial fatty acid 18:1ω7 co-varied with the odd/even fatty alcohol ratio and the coprostanol/cholesterol ratio confirming the regions of aerobic bacterial activity near the sewage outlets. The fluoranthene/pyrene ratio together with the ratio between the (three or less/four or more) ring aromatics and total concentration of aromatics demonstrate the extent of crude oil and pyrogenic contamination in the sediments. San Vicente Bay was divided into three principal regions on the basis of this analysis: (a) the highly contaminated northern end with strongly reducing sediments and high concentrations of organic matter, (b) the region adjacent to the sewage outlets with associated bacterial biomass, and (c) the remaining central and southern areas relatively unaffected by the northern discharges. Partial Least Squares path modelling suggests the latter region received less than 50% of the material discharged at the northern end of the Bay.

Cleaning oiled shores: laboratory experiments testing the potential use of vegetable oil biodiesels.

A series of laboratory experiments were carried out to test the potential of vegetable oil biodiesel for the cleaning of oiled shorelines. In batch experiments, biodiesel was shown to have a considerable capacity to dissolve crude oil, which appears to be dependent on the type of biodiesel used. Pure vegetable oil biodiesels (rapeseed and soybean) were significantly more effective in the cleanup of oiled sands (up to 96%) than recycled waste cooking oil biodiesel (70%). In microcosm and mesocosm experiments, oiled sediments were sprayed with biodiesel and subjected to simulated tides. Microcosm experiments revealed that, of those tested, the highest ratio of biodiesel to crude oil, had the highest effectiveness for cleaning fine sands, with ratios of 2:1 (biodiesel:crude oil) giving the best results. In the mesocosm experiments a ratio 1:1 of soybean biodiesel to crude oil removed 80% of the oil in cobbles and fine sands, 50% in coarse sand and 30% in gravel. Most of the oil was removed with the surface water, with only a small amount being flushed through the sediments. Particle size and pore size were important determinants in the cleanup and mobility of crude oil in the sediments in these static systems. It is expected that the biodiesel effectiveness should improve in the natural environment particularly in exposed beaches with strong wave action. However, more laboratory and field trials are required to confirm the operational use of biodiesel as a shoreline cleaner.

The effect of biodiesel on the rate of removal and weathering characteristics of crude oil within artificial sand columns

Abstract The physical and chemical properties of crude oils differ greatly, and these properties change significantly once oil is spilled into the marine environment as a result of a number of weathering processes. Quantitative information on the weathering of spilled crude is a fundamental requirement for a fuller understanding of the fate and behaviour of oil in the environment. Additionally, such data are also essential for estimating windows-of-opportunities, where specific response methods, technologies, equipment or products are most effective in clean-up operations. In this study, the effects of a relatively low toxicity compound, biodiesel (rape seed oil methyl ester) on the rate of removal and weathering characteristics of crude oil within artificial sand columns are thoroughly investigated using GC/MS techniques. In the absence of the biodiesel, the crude oil exhibits low mobility and a slow rate of microbial degradation within the sediment and as a result, a high degree of persistance. Brent crude oil was subject to a progressive loss of the low molecular weight n-alkanes with respect to time through evaporation and a preferential migration of these fractions through the sediment to depth. The addition of the biodiesel led to greater recovery of oil from the sediment if applied to relatively unweathered crude oil. This was as the result of the crude oil dissolving within the more mobile biodiesel. The negligible concentration of the n-C10 to n-C21 fraction in surface sediment samples suggests a greater solubility of these fractions within the biodiesel and that their subsequent adsorption onto subsurface sediment particles was responsible for their absence from water flushed through the sands. These results suggest that biodiesel may have an active role in the beach clean-up of spilt crude oil.

Tracing sewage in the marine environment : Altered signatures in Concepción Bay, Chile

Lipid biomarkers are now widely used to trace organic matter in the marine environment. Selected compounds and ratios can be used to identify sources or processes. However, in a study of a particularly contaminated area, the expected signatures were not found (Mudge and Seguel, Bol. Soc. Chil. Quím. 42 (1997) 5). This site has been re-examined to determine why they were absent. The concentrations of sterols, fatty acids and alcohol biomarkers of 10 sediment cores from Concepción Bay, Chile, were quantified by capillary gas chromatography-mass spectrometry. The data obtained from 34 fatty acids, 28 fatty alcohols (C12-C30) and 32 sterols from the target study area, indicated that fatty acids from Concepción Bay sediments were the most abundant lipids (range 1.6-307 microg g(-1) dry wt) followed by sterols (range 0.02-25.3 microg g(-1) drywt). The sewage markers 5beta-coprostanol and epi-coprostanol were found in the areas close to the Penco-Lirquen disposal pipe. High bacterial activity was also present as indicated by the cholestanol, 18:1omega7, iso, anteiso and branched fatty acids and enhanced odd/even ratios of fatty alcohol biomarkers. The sediments from the centre of Concepción Bay had a greater marine/algal input characterized by brassicasterol and the marine fatty acids (20:4omega6, 20: 5omega3 22: 6omega3). The terrestrial contribution was mainly characterized by beta-sitosterol, C22-C26 fatty acids and confirmed by short/long chain ratio of the fatty alcohols. The distribution of these two markers indicates that the terrestrial matter passing through the sewage system is deficient in short chain fatty alcohols. The epi-coprostanol/coprostanol versus coprostanol/cholesterol plots also indicated selected removal of the stanols leaving apparently high cholesterol concentrations.

Multivariate Statistical Methods in Environmental Forensics

In an environmental forensic context, statistics can lend considerable support to evidence presented to a court and assist in the interpretation of data. However, the use of statistical methods must be conducted with utmost rigor and be applied only where relevant and necessary. Statistics for the sake of statistics or the wrong statistics may lead to doubt being raised and imply deception. It has also been suggested that a well-planned and executed analytical program should not need statistics to prove a point; this suggestion may be true when simple comparisons are all that is required, but when examining complex environmental situations, statistical methods might be the only ones that can identify the underlying truth. There are several types of statistics, but this article concentrates on some of the multivariate statistical methods that can assist in the identification of the source. This article is not designed to be a comprehensive study of any one method or of any one case but an overview of the methods and the common pitfalls made by inexperienced practitioners.

Vegetable Oil Spills On Salt Marshes

Abstract Following the wreck of the M.V. Kimya during which 1500 tonnes of sunflower oil was spilled, sandy sediments bound together with sunflower oil were discovered on the beach. These are still present 2½ years later. Sunflower and linseed oil were applied to salt marsh sediments to reproduce potential spills. Cores were taken and the vertical migration and degradation rates determined. Sunflower oil polymerised at the surface after 28 days resulting in the formation of a cap of increased shear strength and reduced permeability to water and oxygen. This contrasts with linseed oil that rapidly percolated to depth without the formation of a polymer. One degradation product formed from linseed oil was possibly 18:2ω3, although this has still to be confirmed. Increased bacterial numbers were observed with both oils. in the event of spill, these results suggest sunflower oil should be removed although linseed oil could be left to natural degradation processes.

Temporal trends and identification of the sources of volatile organic compounds in coastal seawater

Volatile Organic Compounds (VOCs) in the marine environment are produced by biogenic sources (marine macroalgae, phytoplankton, sediments, etc.) as well from anthropogenic sources. The temporal variation of such VOCs was studied together with their relationship to biological, meteorological and physico-chemical factors. Sixty four different VOCs were quantified including halogenated (<LoD to 906 ng L(-1)), non-methane hydrocarbons (NMHC) (<LoD to 1539 ng L(-1)), mono-aromatics (<LoD to 4232 ng L(-1)), oxygenated (<LoD to 1539 ng L(-1)) and sulfur containing compounds (<LoD to 160 ng L(-1)). The analyses were performed employing solid phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (GC/MS) analysis. Pigments such as chlorophyll a correlated with halogenated compounds (e.g. chloroform and dichloromethane) and dimethylsulfide (DMS) was maximal during the spring bloom. Multivariate statistical analyses demonstrated seasonal changes in the VOC signature (more mono-aromatics and alkanes in the winter and halocarbons in the summer). Principal component analysis (PCA) demonstrated that physico-chemical and meteorological factors such as wind speed and water temperature can influence the detection of VOCs in surface waters as well their productions. Partial least squares (PLS) modelling highlighted the importance of the microalgae signature in spring while macroalgae and sediments dominated at other times. Short term variability in concentrations and fluxes was due to such factors as tidal state, wind speed and seawater temperature. The atmospheric concentrations were significantly less than any regulatory values although no measurements were made in eutrophic conditions.