Soluble Chemical Species in Bulk Precipitation Collected in the Western Tokyo Regional Distribution of the Deposition Fluxes

Abstract

The regional distribution of deposition fluxes of soluble chemical species in bulk precipitation was determined (Figs.2 to 11). The monthly precipitation samples were collected at 41 urban and rural sites of the western Tokyo of Japan (Fig.1), from June to July of 1988, and analyzed for Na⁺, K⁺, NH₄⁺, Mg²⁺, Ca²⁺, Cl⁺, Br⁺, NO₃^-and SO₄^2-by ion chromatography and atomic absorption spectrometry. Hydrogen ion flux was evaluated by the mass balance calculation which assumes that any charge discrepancy in favor of anions is due to hydrogen ion flux. Based on the assumption of the sodium ion being derived from sea salt, the enrichment factor calculations indicated that sea salt is a minor source for the other ion species (Table 2): the maximum contribution of sea salt is 34% for Cl^-. In order to find out the characteristics of deposition flux pattern in geography, sampling sites were located along a 50 km line from coastal industrial zone to mountainous area. Deposition fluxes of Na+, NH₄⁺, Mg²⁺, Ca²⁺, Cl^- and SO₄^- decreased with increasing distance from the coast. Deposition fluxes of NO₃^- and H⁺+NH₄⁺ were different from those of the other ions. A high acid deposition was found in Machida, 20 km far from the coast. These regional distribution patterns indicated that CaSO₄, MgSO₄ and (NH₄)₂SO, were released from the coastal zone, probably as primary particulate matter. The difference of deposition flux patterns between acid substance and sulfate salt was also briefly discussed.