Search Results

You are looking at 1 - 2 of 2 items for :

  • "upper atmosphere" x
  • Chemistry and Chemical Engineering x
  • Refine by Access: All Content x
Clear All

Abstract  

During a 1991 urban ozone study, simultaneous measurements of ozone and7Be, a tracer of stratospheric air, were obtained. The purpose of the study was to evaluate the potential contribution of stratospheric air to ground-level ozone concentrations observed in Montreal, Canada during the summer time. On June 27 and 28, 1991 two thunderstorms with cloud tops reaching the lower stratosphere hit the southwestern portion of the province of Quebec. High7Be counts that were recorded indicate that stratospheric air did reach the surface in the Montreal area. By using the7Be/ozone upper atmosphere ratio, the study concludes that, over these two days, the convective mixing of the atmosphere could have been responsible for a recorded 48 hour average 18% increase in ground-level ozone concentrations.

Restricted access

Abstract  

The activity concentration of beryllium-7 (7Be), a naturally occurring cosmogenic radionuclide produced in the upper atmosphere, was measured in plants on the Loess plateau of China during the growing season of 2005. The 7Be mass activity concentration on July 27 ranged from 34.8 to 147.1 Bq kg−1 in herbaceous plants, from 47.6 to 116.1 Bq kg−1 in subshrubs, and from 15.7 to 56.8 Bq kg−1 in crop plants. The 7Be mass and areal activity concentrations of a mixture of herbaceous plants increased from 66.8 to 288.7 Bq kg−1 and from 0.7 to 46.5 Bq m−2, respectively, during the growing season. On an areal basis, the fraction of 7Be in plants in the soil–plant system increased from 0.4 to 8.4% during the growing season. Positive linear correlations were found between the increases of 7Be mass and areal activity concentrations in the inter-sampling intervals and the amount of precipitation.

Restricted access