Biomedical subjects

R J Barthelmie

Publications and source records attributed to R J Barthelmie.

4 recordsLinked to original sources

PubMed2001

Nitrogen deposition to and cycling in a deciduous forest.

The project described here seeks to answer questions regarding the role increased nitrogen (N) deposition is playing in enhanced carbon (C) sequestration in temperate mid-latitude forests, using detailed measurements from an AmeriFlux tower in southern Indiana (Morgan-Monroe State Forest, or MMSF). The measurements indicate an average atmosphere-surface N flux of approximately 6 mg-N m(-2) day(-1) during the 2000 growing season, with approximately 40% coming from dry deposition of ammonia (NH3), nitric acid (HNO3), and particle-bound N. Wet deposition and throughfall measurements indicate significant canopy uptake of N (particularly NH4+) at the site, leading to a net canopy exchange (NCE) of -6 kg-N ha(-1) for the growing season. These data are used in combination with data on the aboveground C:N ratio, litterfall flux, and soil net N mineralization rates to indicate the level of potential perturbation of C sequestration at this site.

Ammonia↗

PubMed2000

REVEAL II: seasonality and spatial variability of particle and visibility conditions in the Fraser Valley.

This paper presents data collected during a year-long field experiment (REVEAL II) in the Fraser Valley, British Columbia. The data are used to provide information regarding ambient visibility conditions and fine particle concentrations in the valley. Although average fine mass measured during REVEAL II was 8-9 microg m(-3), the fine particle mass has high light-scattering efficiencies and the visual range is frequently below publicly defined acceptable levels. For example, data indicate that during the fall the visual range is frequently below 20 km even under favorable meteorological conditions. Source apportionment analyses of mass and particle light-scattering indicate motor vehicles may contribute as much as 40% of the fine particle mass in the central valley and up to one-third of the particle light-scattering. In addition to characterizing conditions in the Fraser Valley, slides taken at a number of sites during REVEAL II are used to evaluate a simple method for obtaining (classed) quantitative estimates of visual range from this medium without requiring access to specialized instrumentation.

Air Pollution↗

PubMed1997

Secondary organic aerosols: formation potential and ambient data.

Organic aerosols comprise a significant fraction of the total atmospheric particle loading and are associated with radiative forcing and health impacts. Ambient organic aerosol concentrations contain both a primary and secondary component. Herein, fractional aerosol coefficients (FAC) are used in conjunction with measurements of volatile organic compounds (VOC) to predict the formation potential of secondary organic aerosols (SOA) in the Lower Fraser Valley (LFV) of British Columbia. The predicted concentrations of SOA show reasonable accord with ambient aerosol measurements and indicate considerable seasonal variability in SOA potential. Particulate carbon contributes only approx. 3% of total carbon concentrations in the LFV, and it is shown that variability in total carbon concentrations is significantly larger than variability in gas/particle partitioning.

Aerosols↗

PubMed1996

PM10 in Canada.

Annual mean PM10 concentrations in Canadian cities are between five and eight times estimated background levels. Federal and Provincial agencies in Canada are currently reviewing particulate standards, and considering replacing current total suspended particulate (TSP) standards with standards to regulate PM10 (thoracic particles) because epidemiological research suggests that this size fraction is active in the production of adverse health impacts. This paper documents the spatial and temporal variability of current particulate levels in Canada, and compares them with TSP standards presently implemented in Canada and PM10 standards as applied by the US EPA, state of California and the World Health Organization (WHO). Twenty-four-hour averaged PM10 data from the 52 sites described here exceed the standard as applied in California on up to 35% of monitoring days. The threshold suggested by the WHO for 24-h averaged concentrations is passed at the majority of the sites on approximately 5% of monitoring days.

Air Pollutants↗