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61.
Hal Westberg Ken Sexton Don Flyckt 《Journal of the Air & Waste Management Association (1995)》2013,63(6):661-664
The purpose of this paper is to describe ozone production in forest slash burn plumes. Plumes from controlled fires in the state of Washington were monitored using an instrumented aircraft. Ozone, oxides of nitrogen, condensation nuclei, and visual range (nephelometer) were measured continuously on board the plane. Airborne grab samples were collected for detailed hydrocarbon analysis. The slash burn plumes were found to contain significant quantities of ozone. A buildup of 40–50 ppb above the ambient background ozone concentrations was not unusual. Hydrocarbon analyses revealed the presence of many photochemically reactive olefins in the plume. Hydrocarbon/NO x ratios were favorable for photochemical oxidant production. 相似文献
62.
Mike Barna Brian Lamb Hal Westberg 《Journal of the Air & Waste Management Association (1995)》2013,63(7):1021-1034
ABSTRACT A modeling system consisting of MM5, Calmet, and Calgrid was used to investigate the sensitivity of anthropogenic volatile organic compound (VOC) and oxides of nitrogen (NOx) reductions on ozone formation within the Cascadia airshed of the Pacific Northwest. An ozone episode that occurred on July 11-14, 1996, was evaluated. During this event, high ozone levels were recorded at monitors downwind of Seattle, WA, and Portland, OR, with one monitor exceeding the 1 hr/120 ppb National Ambient Air Quality Standard (at 148 ppb), and six monitors above the proposed 8 hr/80 ppb standard (at 82-130 ppb). For this particular case, significant emissions reductions, between 25 and 75%, would be required to decrease peak ozone concentrations to desired levels. Reductions in VOC emissions alone, or a combination of reduced VOC and NOx emissions, were generally found to be most effective; reducing NOx emissions alone resulted in increased ozone in the Seattle area. When only VOC emissions were curtailed, ozone reductions occurred in the immediate vicinity of densely populated areas, while NOx reductions resulted in more widespread ozone reductions. 相似文献
63.
Marine Protected Area Design and the Spatial and Temporal Distribution of Cetaceans in a Submarine Canyon 总被引:6,自引:0,他引:6
Abstract: The Gully, the largest submarine canyon off the coast of eastern Canada, is currently under consideration as a marine conservation area, primarily because of the increasing interest in oil and gas production on the Scotian Shelf. Cetaceans, as a guild of abundant, large organisms that are relatively sensitive to such threats, provide a reliable means to determine the boundaries for a conservation area in this region. We compared the abundance of cetaceans between the Gully and other parts of the Scotian Shelf and Slope and found that abundance was higher in the Gully. We also assessed cetacean distribution and relative abundance within the Gully relative to search effort for several spatial and temporal parameters: depth, slope, sea surface temperature, and month. Distribution within the Gully was most strongly correlated with depth, but was also significantly correlated with sea surface temperature and month. Five of the 11 cetacean species commonly found in the Gully, and all those for which the Gully formed significant habitat on the Scotian Shelf, were concentrated in the deep (200–2000 m) mouth of the canyon. We suggest that a year-round marine protected area is necessary for the Gully. A core protection zone should be defined in the Gully based on depth and bounded by the 200-m isobath. A buffer zone around the core zone should be defined to provide protection from activities with further-reaching effects, such as noise, dredging, and chemical pollution. 相似文献
64.
Barry R. Taylor Hal R. Hamilton 《Journal of the American Water Resources Association》1993,29(2):221-234
ABSTRACT: In the Saskatchewan River Basin (365,000 km2), which drains the Canadian prairie from the Rocky Mountains east to Manitoba, concentrations of total solutes are usually within the range of 100 to 1000 mg/L. Total solutes levels in tributaries increase markedly from west to east across the basin, as mountain snowmelt and dilute surface runoff are replaced by ion-rich ground water and concentrated prairie runoff as the major influences on solute concentrations. In contrast, total solutes concentrations in main-stem rivers are nearly constant, ranging 200–300 mg/L, with only a small increase across the basin. Dilute mountain runoff dominates solute concentrations in main-stem rivers, despite the influx of increasingly ion-rich water from tributaries. The principal long-term trends in total solute concentrations across the basin, as revealed by linear and sine-curve regressions, were due to the construction of reservoirs, which depress the natural winter maximum in solute concentrations and disrupt the sinusoidal annual pattern, while sharply reducing seasonal variation. These regression methods did not show anticipated anthropogenic increases in salt load in the Red Deer or South Saskatchewan Rivers, but a trend of slowly increasing solutes concentrations (2 mg/L/yr) was detected for autumn flows in the lower Bow River. Municipal wastes from the City of Calgary or irrigation return flows are probably responsible for this increase. 相似文献