『Abstract
The annual and seasonal dust emissions were calculated for eight
types of desertified lands at 120 sites in the Heihe River Basin
of northwestern China. The results showed that dust emission rates
increased from the middle to the lower reaches of the river by
a factor of up to 103. There two strongest areas of
dust emission are the dried-up Gaxun Lake with a dust emission
rate of 1.6 t ha-1 year-1, and the desertified
grassland areas around the abandoned Heicheng City, with a dust
emission rate of 0.6-0.7t ha-1 year-1. The
total annual dust emission with their particle diameters less
than 50, 30, and 10μm were 1.71×106, 1.11×106,
and 0.555×106t, respectively. Dust emission rates showed
striking seasonal variations, with the maximum value (45％) occurring
in spring and the minimum value (13.5％) in summer. The mineral
aerosol-size distributions were also measured and the results
showed that the size distributions for dust and non-dust events
were both trimodal, in contrast with the widely accepted view
that primary particles such as aeolian dust are coarse, whereas
particles less than 1μm in diameter are mainly secondary particulate
substances such as ammonium nitrate, ammonium sulfate, and organic
matter.』
Introduction
Methodology
Particulate matter concentration measurements
US EPA formula and its application
Conclusions
Acknowledgments
References