Potential for natural and enhanced attenuation of sulphanilamide in a contaminated chalk aquifer

Understanding antibiotic biodegradation is important to the appreciation of their fate and removal from the environment. In this research an Isotope Ratio Mass Spectrometry(IRMS)method was developed to evaluate the extent of biodegradation of the antibiotic,sulphanilamide, in contaminated groundwater. Results indicted an enrichment in δ~(13)C of8.44‰ from-26.56(at the contaminant source) to-18.12‰(300 m downfield of the source).These results confirm reductions in sulphanilamide concentrations(from 650 to 10 mg/L)across the contaminant plume to be attributable to biodegradation(56%) vs. other natural attenuation processes, such as dilution or dispersion(42%). To understand the controls on sulphanilamide degradation ex-situ microcosms assessed the influence of sulphanilamide concentration, redox conditions and an alternative carbon source. Results indicated, high levels of anaerobic capacity(~50% mineralisation) to degrade sulphanilamide under high(263 mg/L), moderate(10 mg/L) and low(0.02 mg/L) substrate concentrations. The addition of electron acceptors; nitrate and sulphate, did not significantly enhance the capacity of the groundwater to anaerobically biodegrade sulphanilamide. Interestingly, where alternative carbon sources were present, the addition of nitrate and sulphate inhibited sulphanilamide biodegradation. These results suggest, under in-situ conditions, when a preferential carbon source was available for biodegradation, sulphanilamide could be acting as a nitrogen and/or sulphur source. These findings are important as they highlight sulphanilamide being used as a carbon and a putative nitrogen and sulphur source, under prevailing iron reducing conditions.     

Use of principal components analysis (PCA) on estuarine sediment datasets: The effect of data pre-treatment

Principal components analysis (PCA) is a multivariate statistical technique capable of discerning patterns in large environmental datasets. Although widely used, there is disparity in the literature with respect to data pre-treatment prior to PCA. This research examines the influence of commonly reported data pre-treatment methods on PCA outputs, and hence data interpretation, using a typical environmental dataset comprising sediment geochemical data from an estuary in SE England. This study demonstrated that applying the routinely used log (x + 1) transformation skewed the data and masked important trends. Removing outlying samples and correcting for the influence of grain size had the most significant effect on PCA outputs and data interpretation. Reducing the influence of grain size using granulometric normalisation meant that other factors affecting metal variability, including mineralogy, anthropogenic sources and distance along the salinity transect could be identified and interpreted more clearly.     

An unintended experiment in fisheries science: a marine area protected by war results in Mexican waves in fish numbers-at-age

Marine protected areas (MPAs) are attaining increasing importance in the management of marine ecosystems. They are effective for conservation in tropical and subtropical areas (mainly coral and rocky reefs), but it is debated whether they are useful in the management of migratory fish stocks in open temperate regions. World War II created a large marine area within which commercial fishing was prevented for 6 years. Here we analyse scientific trawl data for three important North Sea gadoids, collected between 1928 and 1958. Using statistical models to summarise the data, we demonstrate the potential of MPAs for expediting the recovery of over-exploited fisheries in open temperate regions. Our age-structured data and population models suggest that wild fish stocks will respond rapidly and positively to reductions in harvesting rates and that the numbers of older fish in a population will react before, and in much greater proportion, than their younger counterparts in a kind of Mexican wave. Our analyses demonstrate both the overall increase in survival due to the lack of harvesting in the War and the form of the age-dependent wave in numbers. We conclude that large closed areas can be very useful in the conservation of migratory species from temperate areas and that older fish benefit fastest and in greater proportion. Importantly, any rise in spawning stock biomass may also not immediately result in better recruitment, which can respond more slowly and hence take longer to contribute to higher future harvestable biomass levels.     

A simple method for preparing prometaphase chromosomes from amniotic fluid cell cultures

A simple method for preparing prometaphase chromosomes from amniotic fluid cell cultures is described. The technique is based upon several key steps including: (1) reduced colcemid concentration, (2) reduced exposure to trypsin-EDTA, and (3) maintaining cells in single suspension by adjusting cell concentration appropriately. Chromosomes with banding resolution up ot 800 bands per haploid set can be routinely produced. The described methodology is particularly useful in defining and establishing the clinical significance of subtle structural aberrations.     

Recent advances in econometric estimation of materials substitution

Interest in substituting reproducible inputs such as capital and labour for non-renewable materials is principally motivated by two factors — the short-run concern about supply disruptions on the part of producing countries and the long-run concern about the exhaustion of depletable natural resources. In this paper, techniques for estimating elasticities of substitution between inputs (ie between different materials or between material aggregates and other input aggregates) from production and cost functions are discussed, and the recent literature that makes use of these techniques is reviewed.     

motor vehicle emissions and atmospheric lead concentrations in the los angeles area

This paper is directed to those concerned with the effect of changes in lead consumption by motor vehicles on atmospheric lead concentrations. Atmospheric lead concentrations in the Los Angeles area have been found to be dependent on lead consumption, meteorology, and source-receptor relationships. Mathematical relationships between these variables for selected Los Angeles area sites are derived. Los Angeles County experienced a 50% reduction in annual average atmospheric lead concentrations between 1971 and 1976, which was found to be due to a decrease in vehicular emissions of lead. Seasonal variations in lead concentration were found to be mainly a product of seasonal variations in weather. Projections of atmospheric lead concentrations for the next decade show a continued downtrend, based on regulation of fuel lead content and introduction of additional catalyst equipped vehicles. By the mid-1980's most locations in the Los Angeles area are expected to attain the California and federal ambient air quality standards for lead, 1.5 micrograms per cubic meter, based on a monthly average.