Samples for precipitation and dry deposition observation are collected using a sampling system installed on ground (Fig. 7.2.15.1), and are picked up every day for precipitation and every month for dry deposition. Maximum wind speed and wind direction, as well as precipitation amount if any, are recorded at the station.
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Fig. 7.2.15.1 Precipitation and dry deposition sampling system at Minamitorishima station. |
The samples and meteorological records are sent once a month to the JMA headquaters where thay are analyzed to obtain pH, electrical conductivity, alcalinity and chemical compositions (NH4+-N, Na+, K+, Ca2+, Mg2+, Cl−, NO3−-N, NO2−-N, SO42−-S, Cd and Hg) using flow-cell pH meter, electrical conductance meter, automatic burette, ion chromatograph and atomic absorption spectrophotometer. Monthly mean values for precipitation are the weighted mean of analytical results of daily samples according to daily precipitation amounts. Dry deposition samples are analyzed separately for water-soluble components and for water-insoluble components. For the former, chemical components of Na+, K+, Ca2+, Mg2+, Cl−, NO3−-N, NO2−-N and SO42−-S are analyzed. The residues are distilled with an evaporator to be weighed. For the latter, organic compounds are burned to be removed and the residual ashes are weighed. Monthly totals are obtained for each component.
GAW stations for greenhouse and reactive gas observation | Precipitation and dry deposition observation | Quality control of chemical analysis for precipitation and dry deposition