Dispersal and dilution of wastewater from an ocean outfall at Davis Station, Antarctica, and resulting environmental contamination.

The Antarctic Treaty permits the discharge of wastewater into Antarctic marine waters providing that conditions exist for initial dilution and rapid dispersal. We investigated the dilution and dispersal of macerated wastewater around Australia's Davis Station in East Antarctica and examined sediments for evidence of contaminants. Methods used to examine hydrodynamic conditions included current meters, dye release experiments and measurement of sewage-associated microbial markers and surfactants in the water column. We measured marine sediments for metals, nutrients, PBDEs, hydrocarbons and faecal sterols. We propose that if there is adequate dilution and dispersal there would be no significant difference in contaminant concentrations in sediments around the outfall compared to distant control sites. Currents were strongly correlated with prevailing wind conditions. Modelling indicated that diffusivity of wastewater had the greatest effect on dilution factors and that neither discharge rates nor local currents had as much effect. During summer conditions of open water, wastewater is likely to be constrained in a narrow plume close to the coast. Concentrations of sewage bacteria were high around the outfall and detected up to 1.5 km away, along with dye. There were significant differences in sediment concentrations of metals, PBDEs, hydrocarbons, nutrients and faecal sterols between sites within 2 km of the outfall and control sites. We conclude that dilution and dispersal conditions at the Davis outfall are insufficient to prevent the accumulation of contaminants in local sediments and that microbial hazards posed by wastewater are an environmental risk to local wildlife.

Detection of intermittent sewage pollution in a subtropical, oligotrophic, semi-enclosed embayment system using sterol signatures in sediments.

A field study was conducted to investigate sewage inputs at popular anchorages in Moreton Bay, a sub-tropical, semienclosed embayment system in Southeast Queensland, Australia. Sterol biomarkers were quantified in sediments revealing low levels over a spatial and temporal scale consistent with a shallow, oligotrophic, highly dynamic, sand dominated system. Despite low concentrations (ng/g) and high variability, relevant sterol/stanol pairs remained well-correlated and were successful in identifying an unexpected once-off pollution event from a point source at Moreton Bay Island. During this incident, the main human sewage biomarker, coprostanol, was found at a concentration of 1.4 microg/g, with a coprostanol/5alpha-cholestanol ratio of 3.2. Other than this one incident, sterol levels were consistently low even when anchorages were at full capacity. Thus, sewage from recreational vessels was found to have very little effect on sediment quality at anchorages in Moreton Bay and Gold Coast Broadwater.

Quantitative determination of sterols and other alcohols in overland flow from grazing land and possible source materials.

Organic marker compounds (biomarkers) can be used to identify the sources of waterborne pollutants. This paper examines sterols and other alcohols in overland flow from pasture-based grazing systems, possible agricultural source materials and water extracts of these source materials as a preliminary step to developing chemical profiles that can be used for tracing pollutants. The biomarkers were quantified using gas chromatography and gas chromatography-mass spectrometry techniques. Analyses of plant material show that some pasture species contain unique compounds, enabling their identification. For example, Arctotheca calendula (capeweed) contains an as yet unidentified compound (Arctotheca m/z 163). Other pasture species that do not contain unique compounds do contain unique ratios of phytol, hexacosanol, octacosanol and 24-ethylcholesterol, enabling their identification. Analyses of faecal samples show that the ratios of sterols to stanols enable faeces to be distinguished from the pasture species, e.g. the ratio of 24-ethylcholesterol to 24-ethylcoprostanol was <1, generally <0.25 for faeces, while for most pasture species this ratio was >4. Using this ratio, qualitative apportioning of the sources of pollutants in overland flow to vegetation or faeces could be performed, but only in extreme cases (i.e. when the ratio <1 or >4). Decaying organic matter and surface soil appear to contain a composite of plant and faecal sterols. Sterols, being sparingly soluble in water and surface active, were not expected to be present in overland flow samples. Surprisingly, cholesterol and 24-ethylcoprostanol were found in both the particulate and filtrate fractions of most overland flow and water extracts of most source materials. Using the ratios of sterols to stanols, particulate organic material in water could be traced back to its broader source, i.e. vegetation or faeces.

Application of comprehensive two-dimensional gas chromatography to the quantification of overlapping faecal sterols.

Standard solutions containing a mixture of seven sterols and 5alpha-cholestane as internal standard, and sample mixtures that comprised varying ratios of sterol and stanols from green lip mussel tissue and dried cow faeces were analysed by using comprehensive two-dimensional gas chromatography (GC x GC). Quantitative results were compared with single-column GC analysis. The latter samples included sterols of interest, but which cannot be readily obtained elsewhere. It may also mimic potential environmental samples where dairy production and aquaculture (oyster, mussel cultivation) share the same catchment; environmental sterol signatures may exhibit characteristics of both sample types comprising this mixture. Whereas single-column GC-flame ionisation detection was unable to reliably quantitate target sterols, the GC x GC experiment permitted small amounts of sterols and stanols to be detected and separated. Likewise GC-MS analysis was unable to detect some of the minor sterols which coeluted on a single column. The GC x GC mode allows complete separation of several important sterols and stanols, such as 24-ethylcoprostanol, campesterol and 24-methylenecholesterol, demonstrating the enhanced resolving power of the GC x GC system. Separation of 24-ethyl-epi-coprostanol from several algal-derived interfering components was achieved, leading to higher degree of confidence in the quantitative analysis of faecal sterols. The effects of a number of operating variables--column length, carrier flow-rate and elution temperature--on component resolution and presentation of data in the two-column analysis are described.

Faecal contamination of source-separated human urine based on the content of faecal sterols.

Transmissible pathogens in source-separated human urine, intended for reuse in agriculture, mainly originate from faeces that cross-contaminate the urine. The health risks associated with the enteric pathogens will largely be dependent on their initial concentration and their inactivation during storage in the urine. Faecal sterols have proven stable in urine and can, rather than indicator bacteria, be used to quantify the faecal cross-contamination. In this study, urine collection tanks were sampled and ratios between various faecal sterols were used to determine if the urine was contaminated by faeces. Twenty-two percent of samples from the upper part of the tanks and 37% of samples from the bottom sludge were found to be contaminated. Coprostanol concentrations in the contaminated urine samples corresponded to a mean faecal contamination of 9.1+/-5.6 mg l(-1) urine. E. coli was absent in a majority of the samples. Faecal streptococci and clostridia were enumerated but not found to correlate with coprostanol concentrations in contaminated samples.