Chemical characterization of fog and rain water collected at the eastern Andes cordillera

摘要

During a three month period in 2003 and 2004, the chemistry of fog andrainwater were studied at the "El Tiro" site in a tropical mountain forestecosystem in Ecuador, South America. The fogwater samples were collectedusing a passive fog collector, and for the rain water, a standard rainsampler was employed. For all samples, electric conductivity, pH, and theconcentrations of NH₄+, K+, Na+, Ca2+, Mg2+,Cl−, NO₃−, PO₄3−, and SO₄2− weremeasured. For each fog sample, a 5 day back trajectory was calculated by theuse of the HYSPLIT model. Two types of trajectories occurred. One type wascharacterized by advection of air masses from the East over the Amazonianbasin, the other trajectory arrived one from the West after significanttravel time over the Pacific Ocean.

We found considerably higher ion concentrations in fogwater samples than inrain samples. Median pH values are 4.58 for fog water, and 5.26 for the rainsamples, respectively. The median electric conductivity was 23 μS cm−1for the fog and 6 μS cm−1 for the rain. The continentsamples exhibit higher concentrations of most ions as compared to thepacific samples, but these differences could not be detected statistically.