Lois Richards

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Aerosol chemical and optical properties were measured near the Mt. Zirkel Wilderness Area in northwestern Colorado. Six-hour PM2.5 (particles with aerodynamic diameters less than 2.5 microm) mass concentrations and PM2.5 dry particle light scattering at 550 nm averaged 4.6 microg m(-3) and 8.6 Mm(-1), respectively. Sulfates, organic carbon, and geological(More)
Both weight-bearing and strengthening exercises have been thought to reduce the hypercalciuria associated with tetraplegia. In patients with incomplete spinal cord injuries and tetraplegia, tilt table exercises reduced hypercalciuria and made the calcium balance more positive particularly in the early group of patients. Strengthening exercises did not have(More)
Particle light scattering and PM2.5 (particles with aerodynamic diameters less than 2.5 microm) concentration data from air quality studies conducted over the past ten years were examined. Fine particle scattering efficiencies were determined from statistical relationships among measured light scattering and fine and coarse mass concentrations. The(More)
Dear Sir: I have read your article “Visibility clarified” (February 198 1, p. 135). It provided a good summary of the technical presentations made at the Grand Canyon symposium, including the state of our understanding of visibility, sources of visibility impairment, and the limitations of and difficulty with the tools (modeling and monitoring, etc.) to(More)
sometimes not true for plumes emitted into a background with high moisture or ozone levels. I t also may not apply to plumes emitted from smelters or urban areas. Since visibility is a sensitive political issue and since VISTTA is sponsored jointly by government and industry, it is very important to us that the results not be generalized to conditions for(More)
  • Lois Richards
  • Journal of the Air & Waste Management Association
  • 1999
The U.S. Environmental Protection Agency (EPA) Notice of Proposed Rulemaking (NPR) for regional haze uses the deciview haze index (dv) as the indicator for visibility impairment and proposes a change of 1 dv as "a small but noticeable change in haziness under most circumstances." All previous visibility rules have specified human perception as the indicator(More)
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