Abstract

This paper describes the concentrations of total dissolved iron (tFe) and <TEX>$Fe^{2+}$</TEX> in rainwater and snow, the relationship of Fe species with other metals and ions in bulk rainwater, and the <TEX>$Fe^{2+}$</TEX> generation mechanism in aqueous samples in rainwater of time series collection. Volume weight mean concentrations of tFe and <TEX>$Fe^{2+}$</TEX> were 3.22 and <TEX>$1.25{\mu}gL^{-1}$</TEX> in bulk rainwater, and 50.1 and <TEX>$43.5{\mu}gL^{-1}$</TEX> in snow, respectively. <TEX>$Fe^{2+}$</TEX> was significant fraction to the tFe, accounted for 3.25-93.4% of the tFe in rainwater and 87% in snow. We also investigated temporal variations of tFe, <TEX>$Fe^{2+}$</TEX>, other metals and ions in rainwater of time series collection during rain event. Although the concentration range of tFe was different from those of other species, a decreasing trend of tFe from the beginning of the rain event was similar with other species. However, though <TEX>$Fe^{2+}$</TEX> did not show such a decreasing trend, <TEX>$Fe^{2+}$</TEX>/tFe was in good correlation with solar radiation. From the results of multiple linear regression analysis and thermodynamic calculations (Mineql+), <TEX>$Fe^{2+}$</TEX> in our samples may be generated from photochemical reduction of <TEX>$Fe^{3+}$</TEX> species (such as <TEX>$Fe(OH)^{2+}$</TEX>,<TEX>$Fe(OH)^{2+}$</TEX> and Fe-oxalate) at daytime.