In this study, the application of the polar organic chemical integrative sampler (POCIS) for the time-weighted average concentration (TWAC) of paddy-use pesticides in environmental water was evaluated. Two herbicides and one fungicide were selected and investigated by deploying POCIS and high-frequency grab sampling (more than two times per day) in three paddy drainage canals (2.8–70 ha) and one river in the Lake Biwa basin for 7–21 day periods. TWACs determined by POCIS and by high-frequency grab samples showed good agreement, and 11 of 14 datasets (79% of all datasets) were within the range of 0.5–2.0-fold difference. To generate estimates of TWAC at different sampling intervals, the high-frequency grab sampling data were subsampled at intervals of 1, 2, 3, 4, and 7days. On the basis of the comparison of TWACs between POCIS and different grab sampling intervals, it is considered that the sampling interval that yields equivalent TWACs to those of POCIS was more than once a week in datasets with low CVs of pesticide concentration (CV ≦ 100%) , but more than three day intervals in databases with high CVs.

We developed a liquid chromatography/mass spectrometry (LC/MS) or tandem mass spectrometry (LC/MS/MS) analysis method for the simultaneous determination of six anions (bromate, chlorate, chlorite, perchlorate, nitrate, and nitrite) in drinking water. Furthermore, we conducted a validation test along with 15 organizations to confirm that the analytical method developed in the present study is applicable to various types of drinking water and instruments. Recovery tests of the six anions spiked into drinking water were performed to evaluate the linearity of calibration curves, selectivity, accuracy (recovery) , repeatability, and intermediate precision of these anions. Regarding four anions (bromate, chlorate, chlorite, and perchlorate) , the accuracy, repeatability, and intermediate precision obtained by the recovery tests satisfied the criteria in the guideline for the validation of the testing method for drinking water provided by the Ministry of Health, Labour and Welfare, Japan. Therefore, we concluded that the analytical method developed in the present study is valid for the analysis of these four anions in drinking water. However, ethylenediamine must be used for the dechlorination of water samples because degradation of chlorite was observed by using sodium thiosulfate. In addition, proper ranges of calibration curves should be selected for the determination of these anions because the range of the linearity of calibration curves differed depending on the anion.

In the Seto Inland Sea, oligotrophication due to the long-term reduction measures of nitrogen and phosphorus, which is evidenced by the discoloration of nori laver and a decrease in fishery production, is pointed out. In this study, we developed a fertilizer that can elute nutrients required for the growth of marine organisms. The main ingredient of this fertilizer is chicken manure, to which steel slag and hardener were added, followed by pressing to form a solid fertilizer. To establish the proper N/P/Fe elution ratio for the growth of microalgae, elution tests using 500 L flasks were carried out with fertilizer pieces of different ingredient mixed ratios. A long-term elution test was also performed using the actual size fertilizer (25 cm diameter and 23 cm height) in 100 L containers under flow-through seawater systems. Elution of nutrients continued for longer than 5 months. It is concluded that the fertilizer developed in this study is useful for enhancing the growth of marine organisms.

The landscape of a small pond in Fukuoka prefecture has been ruined by floating algae. Basic information, such as the type of algae, location of occurrence, and the amount of generated floating algae, was required to take action. In this study, we identified the floating algae by polarizing microscope observation and microbial community analysis. Additionally, we conducted aerial investigations using a multicopter equipped with a visual and near-infrared camera, and we quantified floating algae areas using images obtained from aerial observation. The results revealed that the floating algae were primarily made up of filamentous cyanobacteria from the family Pseudanabaenaceae. They mainly grow in the shallow area of the pond and peel off from the shallow bottom of the pond because of proliferation-related bubbles in summer. In addition, there was a relationship between the increase and decrease in algae carbon calculated using water temperature and solar radiation and the fluctuation in aerially observed algae area, suggesting that measures to limit solar radiation may be effective as a means of controlling algae proliferation.

The antibiotic-resistant ratios of Escherichia coli taken from rivers in Kanagawa prefecture were investigated to clarify their changes since the early 2000s. A considerable number of isolates taken from urbanized rivers carried resistance to cefotaxime, indicating human-related sources such as combined sewer overflows and companion animals. On the other hand, some of the isolates from rivers in the suburbs carried simultaneous resistances to tetracycline and to sulfamethoxazole, which were associated with livestock farming. A comparison of resistant ratios in 2019 with those in the early 2000s shows a significant decrease in the resistance associated with livestock farming and an increase in the resistance to levofloxacin and to gentamicin, although this increase was not statistically significant.