The mechanisms of nitrate (NO_3^-) adsorption and retardation in Andisols are vital to understanding how NO_3^- derived from fertilizers contaminates the groundwater in areas with a volcanic ash soil. In this study, we quantified the relationship between NO_3^- adsorption and retardation in an Andisol under different conditions of pH and coexisting anions. The soil pH was adjusted to 4 or 5 by adding 0.01N HCl or H_2SO_4 solutions. We measured the NO_3^- adsorption on these pH-adjusted soils in batch tests at a soil-to-solution ratio of 1:10, and measured NO_3^- retardation by means of column-flow tests. The NO_3^- adsorption isotherms in the batch tests were described by the Freundlich equation at solution NO_3^- concentrations ranging from I to 10mmol L^<-1>. Nitrate adsorption and retardation were both smaller for H_2SO_4-treated soils than for HCl-treated soils, and decreased at higher soil pH due to the soil's low anion exchange capacity. The retardation factors determined by the column tests were strongly associated with the NO_3^- adsorption measured in the batch tests (r^2=0.99). Furthermore, we could predict the NO_3^- retardation factor from the NO_3^- adsorption in the batch tests through the adsorption-retardation theory. Our results suggest that batch tests for NO_3^- adsorption are a useful tool for inferring NO_3^- retardation in Andisols.

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Eight hundreds and seventy-seven soil samples taken from arable lands in Miyagi Prefecture (7,300km^2, referred to as "Miyagi soils" henceforth), northeastern Japan have been analyzed for 42 trace elements. The results were compared with those of the previous national nationwide scale survey (380,000km2) obtained by analyzing 514 samples from 78 pedons (referred to as "national nationwide soils" henceforth) taken in such a way as to cover a wide range of soil types that are common to Japan. The frequency distributions of most of the elements were positively skewed and coincided well with those of log-normal distributions. The minimum values of all the elements in the national nationwide soils were one to two orders of magnitude lower than those in the Miyagi soils. On the contrary, the maximum values in the national nationwide soils were higher than those in the Miyagi soils with the exception of Cu, Zn, Mo, Sn, Sb, Tl and Pb, presumably due to anthropogenic pollution. Consequently, whereas the concentration ranges of the nationwide soils spanned two to four orders of magnitude, those of the Miyagi soils were narrowed to around one order of magnitude for most of the elements. In spite of these big differences in the concentration ranges between the national nationwide soils and the Miyagi soils, the pattern of changes in concentration of each element in soils with the increase of atomic number were quite similar. The concentrations of Cr, Cu, Zn, Cd, Sn, Pb, Bi and U were higher in surface soils than in sub-surface soils at 1% significance level. Whereas Cd was higher in paddy soils, other 7 elements were higher in orchard soils at 5% significance level. The dendrogram of the 41 elements showed that the occurrence and distribution of the elements in the national nationwide soils were basically controlled by the chemical properties of each element. In the Miyagi soils, however, the effects of anthropogenic activities were also evident.

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