Flow-through tests using a dye microcapsules Lagrangian actinometer (DMC-LA) and a biodosimeter (MS2, Qβ) were conducted to study the UV photosensitivity of DMC-LA in flow-through tests, a method for calculating average UV doses in a UV disinfection reactor, as well as the applicability of the DMC-LA method to flow-through tests. The fluorescence distributions obtained with the DMC-LA fitted the lognormal distributions. The obtained UV dose distributions of the UV disinfection reactor could be regarded as a lognormal distribution with a shape similar to a normal distribution, and the variance increased with decreasing flow rate. The predictions based on the obtained UV dose distributions agreed with the measured values from the flow-through tests using each biodosimeter with the same accuracy over a range of up to 2.9 log inactivation for MS2 and up to 3.1 log inactivation for Qβ. The results of this study confirmed that the DMC-LA method is applicable not only to collimated beam tests but also to flow-through tests, indicating that the DMC-LA method is effective for the validation of UV disinfection reactors.

The first basin-scale survey of concentration levels and regional distributions of major systemic insecticides and their metabolites were conducted in the Lake Hachiro Basin in Akita Prefecture in June and August 2020. Dinotefuran, imidacloprid, thiacloprid, thiamethoxam, clothianidin, ethiprole, fipronil, and thiacloprid amide were detected in the tested samples. The highest detection frequencies of dinotefuran and thiacloprid amide were respectively observed in August (100%) and June (80%) . Such trends seem to be affected by the rice production and productivity in the basin. The highest concentration among the parent pesticides was dinotefuran at 2,200 ng L^-1 detected from Lake Hachiro in August and those in metabolites were thiacroprid amide at 60 ng L^-1 detected from tributaries in June. Dinotefuran was widely detected from the Lake Hachiro Basin, and its concentration was 1–3 orders of magnitude higher than those of other pesticides. The ecotoxicological risk assessment value (maximum measured environmental concentration/ predicted no effect concentration, MECmax/PNEC) , which was calculated using the PNEC value estimated as the acute toxicity test value of a highly sensitive species (Chironomus yoshimatsui) to dinotefuran was greater than 1. However, the environmental behavior and fate of target pesticides during all seasons were unknown in this study. Further detailed studies are required in the Lake Hachiro Basin.