Nh. Lin et al., A preliminary analysis of chemical characteristics of atmospheric pollutants and their deposition budget on the Fu-Shan forest in Taiwan, TERR ATM OC, 11(2), 2000, pp. 481-500
This paper presents the chemical characteristics of atmospheric pollutants
measured at the Fu-Shan forest (620 m MSL) during two two-weeks field exper
iments held in the summer and winter of 1993. Chemical compositions of thes
e atmospheric pollutants in solid, gaseous and liquid phases were analyzed.
The deposition budget of S and N compounds through dry and wet deposition
pathways were particularly assessed. As a result, aerosol mass spectra were
found to be bimodal, having the 50% cut size < 1.0 mu m and around 3.2 mu
m for fine and coarse modes, respectively. In summer, fine and coarse modes
were primarily composed of ammonium sulfate and nitrate, respectively. But
, in winter the coarse mode was dominated by sea salts due to the influence
of northeast monsoon flows. Our average HNO2 (similar to 0.10 ppb) was app
reciably higher than those observed in clean troposphere, whereas HNO3 was
at a comparable level. Meanwhile, ammonia gas and particulate ammonium were
at a lower concentration level compared with those generally observed on t
he continental grounds. The SO2 (< 1 ppb) was comparable with those frequen
tly observed in the free troposphere, while SO42- was close to the lowest l
evel typically obtained in urban areas. In addition, NO3- which is thought
to be associated with local pollution was limited. Therefore, we believe th
at excessive SO42-, to a larger extent, was transported to the site via lon
g-range transport, particularly in winter. With regard to the deposition bu
dget, wet deposition pathway (> 90%) was the most effective mechanism for d
elivering atmospheric S and N compounds to the Fu-Shan forest during the pe
riods of our field experiments.