Here, we qualitatively discuss the effects of flow paths on dissolved organic carbon (DOC) concentrations in a headwater stream during a nonstorm flow (NF) period on the basis of hydrometric measurements at a hillslope and a riparian zone and the DOC concentrations of hillslope runoff water. In the analysis, the NF period in which dominant runoff water was derived from the upslope area in a hillslope (hillslope-NF period) was distinguished from the other NF period (normal-NF period). For hillslope runoff water, DOC concentrations during the hillslope-NF period were very low compared with those during the normal-NF period. For stream water, at a few measurement points, DOC concentrations during the hillslope-NF period were also very low (< 10th percentile of concentrations during normal-NF period), but at most measurement points the concentrations were slightly lower than those during the normal-NF period (at least 25th percentile). At sampling points with a relatively large catchment area (≥ 36 ha), the difference in DOC concentration between the hillslope- and normal-NF periods was small and nearly constant. It was inferred that stream DOC concentrations during NF periods were determined by the balance between the decreasing effects of hillslope water and the increasing effects of riparian water. Moreover, these results suggest that considering the balance is important for models estimating DOC concentrations in headwater streams.

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To investigate the diurnal behavior of linear alkylbenzene sulphonates (LAS) in domestic wastewater from a residential district on a fine-weather day, wastewater was collected for 24 hours from an upper part of a combined sewer. Dissolved LAS (D-LAS) concentration and loading began to increase from early morning and reached the highest values at 9:00. Then, they gradually decreased until noon. Multi-dimensional scaling (MDS) analysis using total LAS (T-LAS) composition showed that around the peak time wastewater was largely derived from laundry. On the other hand, there were significant shifts in D-LAS concentration and loading as well as T-LAS composition on the MDS map from 12:00 to 0:00. Therefore, LAS discharge showed a marked diurnal change. In the above investigation, the LAS adsorbed onto SS (A-LAS) and the D-LAS that is commonly analyzed were assayed. As a consequence, the former occupied larger fraction than the latter. Additionally, A-LAS composition differed from D-LAS composition, because C₁₃-LAS was predominant in A-LAS, whereas C₁₁-LAS was dominated in D-LAS. From the results, it was found that using the T-LAS obtained by analyzing A-LAS as well as D-LAS was desirable, for example, to assess the environmental pollution risk caused by combined sewer overflow. Moreover, the amount of LAS discharged from household per person per day was estimated at 1.2 g · p.e^-1 · day^-1 by taking notice of T-LAS.

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Nitrate and nitrite denitrification rates were analyzed for 12 activated sludge samples collected from municipal wastewater treatment plants. Five of the 12 samples denitrified nitrite more rapidly than they denitrified nitrate. To evaluate the relationship between denitrification rates and denitrifier community structure, we analyzed nitrite reductase genes (nirK and nirS) for two samples. As a result, the activated sludge sample that denitrified nitrate more rapidly than it did nitrite showed large nirS diversity compared with the sample that denitrified nitrite more rapidly than it did nitrate. Moreover, the nirS populations of the two samples were phylogenetically different, although the nirK populations of the two were almost same.

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The effects of pesticides on the biomass and community productivity of periphyton were investigated for three years (2001-2003) in Hiroi stream. The biomass of periphyton was affected by the flow of the stream and precipitation. Pesticides, however, showed no effect on the species composition or biomass of periphyton during the study period. Thus, we measured the net community productivity (NCP) and community respiration (CR) rate of periphyton in June and August of 2003. The NCPs in June and August were 64 and 105 mgC · m^-2 · h^-1 and the CR rates were 74 and 18 mgC · m^-2 · h^-1, respectively. In June, the main herbicide was detected simetryn, and the insecticide Trichlorfon (DEP) and the fungicide Tricyclazole were detected in August. The lower NCP in June than in August might have been caused by the high concentration of simetryn (>5μg · l^-1). However, the NCP was higher in August than in June because DEP and Tricyclazole decreased the respiration rate of organisms such as insects and bacteria. Simetryn reduced NCP, and DEP and Tricyclazole lowered CR level, resulting in an increased NCP. We suggest that measuring the NCP and CR rate of periphyton in aquatic ecosystems is an effective method of assessing the effects of pesticides.

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The proper management of water quality in fishing ports handling seafood is necessary for ensuring food quality and public health. In this study, the hygienic conditions at Aoshima fishing port (Miyazaki, Japan) and surrounding coastal areas were investigated. In water samples obtained from inner sites of the port using a lift pump, coliform counts and fecal streptococcus counts varied seasonally from 10 to 10⁴ MPN·100ml^-1 and from 0 to 10² MPN·100ml^-1, respectively. In water samples from an estuary located adjacent to the port, coliform counts and fecal streptococcus counts were1 to 2 orders of magnitude higher that those of water samples from the fishing port. Coliform counts obtained by the MPN method were significantly higher than fecal streptococcus counts and fecal coliform counts obtained by the membrane filter method. Fecal streptococcus counts and fecal coliform counts corresponded to 2% and 3% of coliform counts, respectively. There was an inverse correlation between salinity and coliform counts, and coliforms seemed to be diluted with seawater. Fecal streptococcus counts showed a lower correlation with not only salinity but also turbidity, suggesting that sedimentation and resuspension affect the fecal streptococcus population dynamics in the estuary near the port.

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