Chemical and biological profiles of sediments as indicators of sources of contamination in Hamilton Harbour. Part II: bioassay-directed fractionation using the Ames Salmonella/microsome assay

Bottom sediment and suspended sediment samples from Hamilton Harbour (western Lake Ontario) and from a major tributary were profiled using a bioassay-directed fractionation approach. Sample extracts were fractionated using an alumina/Sephadex gel clean-up procedure to afford non-polar aromatic fractions which were characterized using chemical analyses and the Ames/microsome bacterial assay in Salmonella typhimurium strains YG1025 with the addition of oxidative metabolism (S9), and YG1024 without S9. Non-polar aromatic fractions of selected samples were separated by normal phase HPLC into 1-min fractions which were subjected to bioassay analyses. The bioassays using strain YG1025+S9, a TA100-type strain, were performed to assess genotoxicity arising from the presence of polycyclic aromatic hydrocarbons (PAH). Fractions which exhibited mutagenic activity contained PAH with molecular masses of 252, 276 and 278 amu; these fractions contained over 80% of the genotoxicity attributable to PAH. Individual compounds identified using Gas Chromatography-Mass Spectrometry analyses in these active fractions included benzo[a]pyrene, indeno[cd]pyrene and dibenz[a,h]anthracene. The YG1025+S9 mutagenic activity profiles were similar for all samples. Mutagenic activity profiles generated using strain YG1024-S9, a TA98-type strain sensitive to compounds characteristic of mobile source emissions, were very different. The mutagenic activities in strain YG1024-S9 were greatest for harbour-suspended sediment samples collected from sites impacted by a major tributary. Suspended sediments collected near areas known to contain high levels of coal tar-contamination in the bottom sediments contained higher levels of genotoxic PAH than suspended sediments collected from other areas of the harbour.     

A MORPHOLOGICAL AND ECONOMIC EXAMINATION OF PLUNGE POOLS AS ENERGY DISSIPATERS IN URBAN STREAM CHANNELS1

ABSTRACT: Naturally formed plunge pools (scour holes) are a common morphologic feature in many urban stream systems where the transition between a pipe and a natural channel occurs. Plunge pools serve as significant stream energy dissipaters, increasing flow resistance and enhancing stream channel stability. Such features may also improve habitat diversity and serve as refugia for stream biota during low flow periods. The morphologic characteristics of several naturally formed plunge pools associated with road crossing culvert outlets in the metropolitan Charlotte, North Carolina, area are presented. Plunge pool dimensions surveyed include maximum depth, length, and width, and longitudinal and side slopes as well as bed material. Culvert outlet dimensions and hydraulic characteristics of the scouring jet for each study site are also reported. Design equations developed from flume studies generally failed to predict the naturally formed plunge pool dimensions. Pool volume was significantly correlated with drainage area, with pool depth being the least sensitive dimension to changes in the magnitude of the scouring flow. The excavation costs for designed plunge pools compare favorably to initial construction costs of traditional culvert outlet riprap aprons.     

ANALYSIS AND PREDICTION OF SURFACE RUNOFF IN AN URBANIZING WATERSHED USING SATELLITE IMAGERY1

ABSTRACT: This paper demonstrates how satellite image data [e.g., from Landsat 5 Thematic Mapper (TM)], in conjunction with an urban growth model and simple runoff calculations, can be used to estimate future surface runoff and, by implication, water quality within a watershed. To illustrate the method, predictions of land use change and surface runoff are shown for Spring Creek Watershed, a medium sized urbanizing watershed in Central Pennsylvania. Land cover classifications for this watershed were created from images for summertime 1986 and 1996 and subsequently used as input to the Clarke urban growth model, called SLEUTH, to predict land use changes to the year 2025. Simulations with this model show a progressive growth in the percentage of urban pixels and in impervious surface area in the watershed but also an increase in woodland, primarily in previously clear‐cut areas. Given that woodland area will continue to increase in area, surface runoff into Spring Creek is predicted to remain only slightly above present level. However, should the woodland amount fail to increase, surface runoff is then predicted to increase more significantly during the next 25 years. Finally, the concept of urban sprawl is addressed within the context of predicted increases in urbanization by relating the implied increase in impervious surface area to population density within the watershed.     

Heteroduplex formation: A potential source of genotyping error from PCR products

The formation of heteroduplexes from polymerase chain reaction (PCR) products has recently become a diagnostic tool that is routinely used for the prenatal detection of small deletions or insertions in a number of disease-causing alleles. We present evidence illustrating that heterozygous PCR products can manifest ‘invisible’ heteroduplexes that can ultimately lead to genotyping errors. Justifications for these ‘invisible’ heteroduplexes and requisite parameters to optimize their detection are presented.     

Application of function analysis to bathing areas in the Maltese Islands

On a small island such as Malta where many developers and policy makers place a large emphasis on social use and develoment values, which encourages recreational/industrial development, it is often hard to promote the monetary value of coastal conservation due to strong competition with the large tourism industry. An assessment of the ecological (conservation) and economic (use/development) values of four popular Maltese bathing areas (Mellieha, St. George’s, Ramla and Ghajn Tuffieha Bay) was carried out by evaluating their ability to provide a number of functions. This is dependent on the environments’ inherent characteristics within the context of locally applicable time and space functions. Function Analysis is an innovative technique able to provide a means for assessing changes in environmental quality of an area and evaluating the sustainability of applied management regimes. This paper is a first example of an application of the Functional Analysis approach in Malta. Local application of this technique indicates a need for additional refinement in application to coastal areas. Analysis showed that St. George’s, had the lowest conservation value, Ramla and Ghajn Tuffieha bay had the highest conservation values, Mellieha Bay had high conservation value and use/development potential. In this context, conservation value is understood to reflect values of biodiversity, information/knowledge and environmental quality.     

Public mosquito abatement

Mosquito abatement is a public good for which there is a long history of operating expenditures and measured performance. A simultaneous model of mosquito abundance and abatement response is developed. Parameters are estimated using time-series, cross-section data from 30 districts. Both insecticides and ditching have contributed to reduced mosquito populations. There is evidence that district managers may have invested in excess permanent control (ditching) relative to use of insecticides, and that present abatement expenditures for the average district are excessive.