Biomedical subjects

R P Walsh

Publications and source records attributed to R P Walsh.

13 recordsLinked to original sources

PubMed2001

Heavy metals in the waters of the Nant-y-Fendrod: change in pollution levels and dynamics associated with the redevelopment of the Lower Swansea Valley, South Wales, UK.

Approximately 240 years (c. 1720-1960) as a world centre for the metal smelting industry left the Lower Swansea Valley as a derelict urban landscape with severe Cu, Zn, Pb, Cd and Ni and metal contamination. Using analysis of archival water quality and discharge records, this paper assesses changes in river pollution over the period 1966-1999 for the Nant-y-Fendrod stream. The marked reduction in metal pollution levels over the period can be linked to the cessation of remaining metal smelting activity and to the rehabilitation and redevelopment measures and their timing. Pollution, both in the past and currently, is shown to be episodic rather than continuous and relationships of high pollution levels to antecedent weather, season, discharge and hydrograph position are explored. Some of the highest levels were recorded during redevelopment itself. Prospects for metal pollution episodes in the Nant-y-Fendrod with further redevelopment in the Lower Swansea Valley in the future are briefly discussed.

Conservation of Natural Resources↗

PubMed1999

The role of extreme events in the impacts of selective tropical forestry on erosion during harvesting and recovery phases at Danum Valley, Sabah.

Ten years' hydrological investigations at Danum have provided strong evidence of the effects of extremes of drought, as in the April 1992 El Niño southern oscillation event, and flood, as in January 1996. The 1.5 km2 undisturbed forest control catchment experienced a complete drying out of the stream for the whole 1.5 km of defined channel above the gauging station in 1992, but concentrated surface flow along every declivity from within a few metres of the catchment divide after the exceptional rains of 19 January 1996. Under these natural conditions, erosion is episodic. Sediment is discharged in pulses caused by storm events, collapse of debris dams and occasional landslips. Disturbance by logging accentuates this irregular regime. In the first few months following disturbance, a wave of sediment is moved by each storm, but over subsequent years, rare events scour sediment from bare areas, gullies and channel deposits. The spatial distribution of sediment sources changes with time after logging, as bare areas on slopes are revegetated and small gullies are filled with debris. Extreme storm events, as in January 1996, cause logging roads to collapse, with landslides leading to surges of sediment into channels, reactivating the pulsed sediment delivery by every storm that happened immediately after logging. These effects are not dampened out with increasing catchment scale. Even the 721 km2 Sungai Segama has a sediment yield regime dominated by extreme events, the sediment yield in that single day on 19 January 1996 exceeding the annual sediment load in several previous years. In a large disturbed catchment, such road failures and logging-activity-induced mass movements increase the mud and silt in floodwaters affecting settlements downstream. Management systems require long-term sediment reduction strategies. This implies careful road design and good water movement regulation and erosion control throughout the logging process.

Ecosystem↗

PubMed1999

Parsimonious modelling of water and suspended sediment flux from nested catchments affected by selective tropical forestry.

The ability to model the suspended sediment flux (SSflux) and associated water flow from terrain affected by selective logging is important to the establishment of credible measures to improve the ecological sustainability of forestry practices. Recent appreciation of the impact of parameter uncertainty on the statistical credibility of complex models with little internal state validation supports the use of more parsimonious approaches such as data-based mechanistic (DBM) modelling. The DBM approach combines physically based understanding with model structure identification based on transfer functions and objective statistical inference. Within this study, these approaches have been newly applied to rainfall-SSflux response. The dynamics of the sediment system, together with the rainfall-river flow system, were monitored at five nested contributory areas within a 44 ha headwater region in Malaysian Borneo. The data series analysed covered a whole year at a 5 min resolution, and were collected during a period some five to six years after selective timber harvesting had ceased. Physically based and statistical interpretation of these data was possible given the wealth of contemporary and past hydrogeomorphic data collected within the same region. The results indicated that parsimonious, three-parameter models of rainfall-river flow and rainfall-SSflux for the whole catchment describe 80 and 90% of the variance, respectively, and that parameter changes between scales could be explained in physically meaningful terms. Indeed, the modelling indicated some new conceptual descriptions of the river flow and sediment-generation systems. An extreme rainstorm having a 10-20 year return period was present within the data series and was shown to generate new mass movements along the forestry roads that had a differential impact on the monitored contributory areas. Critically, this spatially discrete behaviour was captured by the modelling and may indicate the potential use of DBM approaches for (i) predicting the differential effect of alternative forestry practices, (ii) estimating uncertainty in the behaviour of ungauged areas and (iii) forecasting river flow and SSflux in terrain with temporal changes in rainfall regime and forestry impacts.

Ecosystem↗

PubMed1999

The ecoclimatology of Danum, Sabah, in the context of the world's rainforest regions, with particular reference to dry periods and their impact.

Climatic records for Danum for 1985-1998, elsewhere in Sabah since 1879, and long monthly rainfall series from other rainforest locations are used to place the climate, and particularly the dry period climatology, of Danum into a world rainforest context. The magnitude frequency and seasonality of dry periods are shown to vary greatly within the world's rainforest zone. The climate of Danum, which is aseasonal but subject, as in 1997-1998, to occasional drought, is intermediate between less drought-prone north-western Borneo and the more drought-prone east coast. Changes through time in drought magnitude frequency in Sabah and rainforest locations elsewhere in South-East Asia and in the Neotropics are compared. The 1997-1998 ENSO-related drought event in Sabah is placed into a historical context. The effects of drought on tree growth and mortality in the tropics are assessed and a model relating intensity and frequency of drought disturbance to forest structure and composition is discussed.

Borneo↗

PubMed1980

Attitudes toward the older job applicant: just as competent, but more likely to fail.

Undergraduate and mid-life participants evaluated a male or female job applicant on the basis of a transcript of a job interview, answering both attitudinal and attributional questions. One-half of the participants were told that the applicant was 65 years old, one-half that the person was 25 years old. Competence of the applicant and his or her success in obtaining the job were also manipulated. Age and sex of the applicant had very little impact on attitudinal items in both the young and mid-life samples. Regardless of the target's age and sex, competent and hired applicants were rated significantly more positively on all questions than their not-hired or less competent counterparts. However, there was a significant age by hiring interaction on the attribution items. Stable factors (particularly demographic characteristics) were used more often to explain the failures of the old than the failures of the young. Implications of these results for employment prospects of the elderly as well as future attitude research are discussed.

Adult↗

PubMed1979

Old men and young women: how objectively are their skills assessed?

Seventy-four male and female undergraduate participants evaluated an essay describing a work of art. They read either a well or a poorly written essay attributed to one of the following authors: a 25-year-old male, a 25-year-old female, a 64-year-old male or a 64-year-old female. Age of target X sex of target X essay quality interactions emerged on four of five dependent variables. In general, essay quality affected evaluations of young male and old female authors, but had little impact on evaluations of young females and old males. The results suggest that young females and old males may be the target of subtle prejudice which causes their work to be assessed unobjectively. They also emphasize the importance of simultaneously manipulating age and sex of target persons in future research. Implications of the findings for the accurate evaluation of elderly males in employment settings are discussed.

Adult↗

PubMed1976