A stable isotopic technique was used to identify the effects of groundwater recharge on nitrate concentration in the alluvial fans of the eastern Kofu basin. Precipitation, groundwater and river water samples were collected from the Fuefukigawa and Hikawa—Kanegawa alluvial fans. The samples were analyzed for nitrate concentration, water δD and δ¹⁸O and nitrate δ¹⁵N. A wide range of nitrate concentrations was observed in the groundwater of both alluvial fans. The observed δ¹⁵N values suggest that the major sources of nitrate are the fertilizers used in orchards. Similarly, the values of δD and δ¹⁸O shows that precipitation and river water are the sources of groundwater recharge for both aquifers. Furthermore, a strong positive correlation was observed between nitrate concentration and δ¹⁸O values. Nitrate concentration increases with an increase in δ¹⁸O value, where lower δ¹⁸O values correspond to river water and higher δ¹⁸O values correspond to precipitation. It is suggested that precipitation acts as a carrier and river water acts as a diluent in nitrate loading from terrestrial catchments.

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The purpose of this preliminary study is to characterize stone powder granulated with cement for the remediation of an organically rich sediment and the control of nutrient balance in a water column. The material used contained SiO₂, Al₂O₃, K₂O, CaO, CO₃, Fe₂O₃, MgO, TiO₂ and trace elements with quartz and aluminum silicate as the main phases. An increase in the pH of seawater due to cement was observed with the material addition, which was effective for the remediation of the acid-rich sediment in coastal seas. Phosphate and silicate were released into seawater and the growth of S. costatum was maintained with the material addition. Thus, results of this preliminary study support the notion that the application of granulated stone powder may have potential advantages for the remediation of the acid-rich sediment and the control of the balance of nutrients in seawater.

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Superoxide radical produced during algal metabolism is one of the most important agents that contribute to the transformation of the Fe(III)-organic ligand complex to more bioavailable Fe(II). In this work, we investigated the kinetics of superoxide-mediated Fe(II) production from Fe(III) complexed by citrate (Fe(III)Cit) in coastal seawater on the basis of a laboratory experiment and a kinetic model. To simulate a coastal environment, Fe(III)Cit samples with various ratios of citrate concentration to iron concentration (ligand/Fe ratio) were incubated for five minutes to one week in seawater medium. Then, Fe(II) production rate was spectrophotometrically measured by detecting the ferrous-ferrozine complex. During the measurement, superoxide was constantly generated by oxidizing xanthine. Fe(II) production rate generally decreased with incubation time, since Fe(III)Cit as a source of Fe(II) gradually dissociated to form less reactive iron oxyhydroxide in coastal seawater. However, when the ligand/Fe ratio was sufficiently high, the dissociation of Fe(III)Cit was suppressed and Fe(II) was formed at a relatively higher rate over one week. These results demonstrated that Fe(II) production rate is largely influenced by ligand/Fe ratio and incubation time. The kinetic model developed was in good agreement with the experimentally determined Fe(II) production rates.

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The long-term succession of bacterial communities in a medium-scale septic tank was monitored by the denaturing gradient gel electrophoresis (DGGE) of amplified 16S rDNA fragments. The calculation of diversity indices from DGGE profiles indicated that the bacterial diversity in the aeration tank was significantly higher than those in the other tanks studied. Ten of the 23 sequenced DGGE bands were affiliated with beta-proteobacteria and some of these bacteria were prominent. Clustering analysis of the DGGE banding pattern revealed that spikes in feed strength caused significant changes in community structure in the raw water and aeration tanks. Dendrogram construction using the DGGE profiles of the aeration tank showed that the bacterial community structure changed by direct inputs of organic waste matter returned to the original stable community structure over time. The specification of bacteria that mainly affect the succession of the indigenous bacterial community structure was facilitated by the dendrogram construction from DGGE profiles.

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