抄録
The aim of the present study was to investigate the air concentrations (mass concentration) and exchange fluxes of inorganic particles, i.e., water-soluble inorganic components in fine and coarse particles, and relevant gases at a paddy field for the single cropping of rice in central Japan. The target chemical species were ammonium (pNH4), nitrate (pNO3), nitrite (pNO2), sulfate (pSO4), and chloride (pCl) for inorganic particles separated into coarse and PM2.5 fractions and ammonia (NH3), nitric acid (HNO3), nitrous acid (HNO2), sulfur dioxide (SO2), and hydrochloric gas (HCl) for the relevant gases. Intensive observations were conducted for approximately one week in the winter of 2009 as a fallow season (winter 2009) and in the summer of 2010 at the heading stage of paddy rice (summer 2010). The filter-pack and gradient methods were used to determine the air concentrations and the exchange fluxes, respectively. The air concentrations of the coarse particles were lower than those of the PM2.5 except pCl and pNO3 in the summer of 2010. The ion balance of PM2.5 implied an acidic condition in the daytime in summer 2010 but neutral conditions at other times. Ammonia showed the highest air concentrations and the largest exchange fluxes in most cases among all target species. The paddy field was usually a sink for the inorganic particles and relevant gases; however, NH3 emission in the summer of 2010, perhaps from the paddy rice, occasionally occurred when the air concentrations of NH3 became very low.
