Stability of ionic components in precipitation samples - A case study in Taipei

The changes in ionic contents were studied in acidic precipitation samples collected for precipitation events in Taipei, which is near the sea. The st orage cases under investigation include filtration, refrigeration, and ligh t. Thus the experimental design leads all precipitation samples collected i n the same rain event stored under different conditions. They were then ana lyzed six times successively within two months to provide the information c ontaining potential ionic composition change. The measured constituents are H+, K+, Na+, Ca+, Mg2+, NH4+, NO3-, SO42-, and Cl-. The comparison of meas ured ionic concentrations corresponding to different storage methods yield no significant difference. The increases of NO3- and decreases of NH4+ with time were observed to be of similar magnitude, while the variation of pH v alues is significant. The presented study indicated the important role play ed by sample storage in determining the ionic composition of precipitation samples.