We investigated the properties of organic matter indicators in water collected at landfill sites in Fukuoka prefecture, Japan. A linear relationship was observed between total organic carbon (TOC) and chemical oxygen demand (COD).However, no clear relationship was found between TOC and biochemical oxygen demand (BOD). This lack of a relationship was inferred to attribute to the influence of bacterial nitrification on BOD. Next, we evaluated of water quality characteristics by using organic matter indicators and inorganic ion components. The results of principal component analysis showed that the primary component indicated the total amount of pollution, and the secondary component indicated the balance of organic and inorganic components of the contamination. The landfill related water was classified into seven groups by the results of cluster analysis. The radar chart of each group was made using water quality indicators, which were the ratios of the average of each group to the average of all samples. The shape of the radar chart of each group was consistent with the component type based on the principal component scores, and it was possible to visualize the differences among the water groups. In addition, we investigated data on leachate collected during a period, in which hydrogen sulfide gas was generated, and the resulting radar chart showed that organic matter indicators tended to be higher. These results indicated that the method of evaluating water quality used in this study was effective for understand the characteristics of water quality for the proper management of waste landfill site.

In early February 2016, tap water originating from Agano River was reported to have an unusual odor. In order to elucidate the source of the compound and its cause, the Agano River Basin was investigated from downstream to upstream following the specific odor. As a result, we found that the odor was derived from the branches of the Aga River in Fukushima Prefecture, and the maximum odor concentration reached 240,000. By measuring a water sample with the maximum odor intensity, we identified the odor compound using: 1) a search system for unknown mass spectrum using gas chromatography mass spectrometry (GC/MS); 2) sensory gas chromatography with flame ionization detector and 3) chemical constitutions deducted from the precise mass using gas chromatography time-of-flight mass spectrometry. The results of these measurements suggested that the odor compound was 2-methoxy-3,5- dimethylpyrazine (2-MDMP), which was confirmed by measurement of a 2-MDMP standard using GC/MS. Purge and Trap GC/MS was adopted as an easy and rapid method to determine the 2-MDMP concentration at the odor threshold level in river water. Using this method, 2-MDMP concentrations ranged from ＜0.5 to 29,000 ng/L. High correlation was observed between concentrations of 2-MDMP and odor concentrations, which shows that 2-MDMP was the main pollutant producing the unusual odor in the Agano River Basin.