| During a three month period in 2003 and 2004, the chemistry of fog and
rainwater were studied at the "El Tiro" site in a tropical mountain forest
ecosystem in Ecuador, South America. The fogwater samples were collected
using a passive fog collector, and for the rain water, a standard rain
sampler was employed. For all samples, electric conductivity, pH, and the
concentrations of NH4+, K+, Na+, Ca2+, Mg2+,
Cl−, NO3−, PO43−, and SO42− were
measured. For each fog sample, a 5 day back trajectory was calculated by the
use of the HYSPLIT model. Two types of trajectories occurred. One type was
characterized by advection of air masses from the East over the Amazonian
basin, the other trajectory arrived one from the West after significant
travel time over the Pacific Ocean.
We found considerably higher ion concentrations in fogwater samples than in
rain samples. Median pH values are 4.58 for fog water, and 5.26 for the rain
samples, respectively. The median electric conductivity was 23 μS cm−1
for the fog and 6 μS cm−1 for the rain. The continent
samples exhibit higher concentrations of most ions as compared to the
pacific samples, but these differences could not be detected statistically. |