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Biomedical subjects

P M Geary

Publications and source records attributed to P M Geary.

9 recordsLinked to original sources
PubMed2005

Effluent tracing and the transport of contaminants from a domestic septic system.

A domestic soil absorption system in a coastal location was instrumented with suction lysimeters and piezometers and monitored between August and December 2002. Using the sandy soils from the site, column leaching experiments were also undertaken and these suggested that bromide would be a suitable conservative tracer which could be added to the wastewater system to determine the direction and rate of groundwater flow. The septic system plume boundaries were identified from the monitoring results and the subsurface fate of the inorganic nutrients determines using ion ratios. The tracing results indicated that groundwater was moving at 0.4 m/day towards a nearby drain. The ion ratios indicated that total inorganic nitrogen and orthophosphate were not substantially lost or diluted in the sandy soils downgradient from the soil absorption system, and that without riparian vegetarian lining the drain, these nutrients would have been largely unattenuated in transport. In the absence of adequate vertical and horizontal setback distances, riparian vegetation is regarded as very important in limiting the subsurface transport of inorganic nutrients from domestic septic systems.

Absorption↗
PubMed2003

Bacterial source tracking and shellfish contamination in a coastal catchment.

Introduced pathogens from faecal material can make their way into the aquatic environment from a number of catchment sources. These sources typically include sewage outfalls, seepage from septic tanks, and urban and agricultural runoff. Shellfish as filter feeders are particularly susceptible to contamination in faecally contaminated waters and a range of microbiological indicators have been developed to assess the levels of contamination and likely risks to public health (Hackney and Pierson, 1994). This paper outlines the application of bacterial source tracking (BST) in a shellfish growing area in part of the Port Stephens estuary along the NSW north coast. The approach is based on the premise that bacterial isolates from different faecal sources will have significantly different resistance patterns to the battery of antibiotics and concentrations tested. Faecal streptococci (FS) were isolated from several possible faecal sources: beef and dairy cattle, chickens and humans. The resistance patterns of these isolates to four different concentrations of four antibiotics were compared to those of FS isolates obtained from samples collected upstream and in the vicinity of the oyster leases. Discriminant analysis was performed using the patterns from the known source isolates and the rate of correct classification was determined for each source. The predictive function of discriminant analysis was then used to determine the most probable source of each of the unknown isolates from Tilligerry Creek, the drainage channels to the estuary, and the shellfish leases. Preliminary results are presented here and suggest that there is no single significant source of faecal contamination, rather there are contributions from a range of sources. The findings may have implications for the ways in which land use activities and catchments are managed in similar estuarine locations with a shellfish industry.

Agriculture↗
PubMed2001

The impact of biomass harvesting on phosphorus uptake by wetland plants.

Two species of macrophytes, Baumea articulata and Schoenoplectus mucronatus, were examined for their capacity to remove phosphorus under nutrient-rich conditions. Forty large bucket systems with the two different species growing in two types of substrate received artificial wastewaters for nine months, simulating a constructed wetland (CW) under high loading conditions. Half of the plants growing in the topsoil and gravel substrates were periodically harvested whereas the other half remained intact. Plant tissue and substrate samples were regularly analysed to determine their phosphorus concentrations. With respect to phosphorus uptake and removal, the Schoenoplectus in the topsoil medium performed better than the Baumea. Biomass harvesting enhanced P uptake in the Schoenoplectus, however the effect was not significant enough to make an improvement on the overall P removal, due to the slow recovery of plants and regrowth of biomass after harvesting. From P partitioning, it was found that the topsoil medium was the major P pool, storing most of total P present in the system. Plant parts contributed only minor storage with approximately half of that P stored below ground in the plant roots. The overall net effect of harvesting plant biomass was to only remove less than 5% of total phosphorus present in the system.

Biomass↗
PubMed2000

A comparison of the effects of Veau-Wardill-Kilner palatoplasty and furlow double-opposing Z-plasty operations on eustachian tube function.

OBJECTIVE: The purpose of this study was to compare the effects of Veau-Wardill-Kilner (VWK) two-flap palatoplasty and Furlow double-opposing Z-plasty operations on eustachian tube (ET) opening in patients with cleft palate (CP). DESIGN: Twenty-six patients underwent CP repair between 1993 and 1997. VWK and Furlow operations were used in 13 patients each. All patients were examined by the otorhinolaryngologist before and after the operations; mean follow-up time was 27.3 months. Secretory otitis media (SOM), as identified by tympanograms, was the comparison criterion used. RESULTS: The prevalence of SOM was 69% (n = 18) in all CP patients preoperatively. Among those with preoperative SOM, we did not find any statistically significant difference in the frequency of postoperative SOM between the two techniques. CONCLUSION: This study suggests that there is no difference in postoperative ET function between patients undergoing either VWK or Furlow operations, in spite of the differences in muscle positioning in these operations. We discuss the implications of this finding in relation to surgical anatomy and histology of the soft palate muscles.

Child↗