Colloids and their interaction with REEs was studied in granitic groundwater and closed gallery at 500 m depth. Colloidal particles of silicate minerals, iron minerals, carbonate minerals, sulfur and organics with size of 0.1-100 micron meter were identified in groundwater. REEs are likely to be pseudo carbonate colloids. In the closed gallery REEs are probably captured by cement and clay materials.

From February 29 to March 17, 2016, deep-sea drilling of hydrothermal systems was operated at Iheya North Knoll and Noho Site in Okinawa Trough. Recovered core samples were cut off at 1 m long on the Lab. Roof Deck, and gas sensing and sub-sampling for gas analysis were conducted. The sectioned cores were then scanned by X-ray computed tomography. The core samples for interstitial water analysis were selected at 10-25 cm long. The sample was squeezed according to the IODP protocol to extract interstitial water samples. The samples were used for measurements of pH, alkalinity, nutrients, and hydrogen sulfide on board, and major elements on land.

Land use in a catchment area has significant impacts on nitrate eluted from the catchment, including atmospheric nitrate deposited onto the catchment area and remineralized nitrate produced within the catchment area. In this study, we determined the spatial distribution and seasonal variation of stable isotopic compositions of nitrate for more than 30 streams within the same watershed, the Lake Biwa watershed in Japan, in order to use O-17 excess of nitrate as an additional tracer to quantify the mole fraction of atmospheric nitrate accurately and precisely.

This study evaluated method validation and five pesticide residues Diazinon, Fenarimol, Cyanazine, Isoprothiolane and Simetryn in water samples from Kurose River, Hiroshima prefecture, Japan. Water samples were collected every month (March to June 2016) from seven sites in Kurose river. The samples were concentrated with solid-phase extraction (SPE) apparatus and analyzed by a reverse phase HPLC. Assay validation parameters evaluated include linearity range, specificity, limit of detection (LOD) and limit of quantification (LOQ). Mobile phase compositions (Acetonitrile-MilliQ) were evaluated to optimize peak signal and retention times (RTs). Good linearity was achieved in a range of 10 to 200 ?g/L (r² ?0.99), with an accuracy range of 99.81 to 100.69%. The average recoveries of spiked samples ranged from 70.5 to 120.6%. The Cynazine and Simetryn registered relatively higher concentration during transplantation of rice (April and May), and correlated well with their application period. Sites K3 and K4 showed relatively higher concentrations during the month of June for almost all the pesticides, hence a need to evaluate their environmental risks.

The observation of organic carbon (TOC) was conducted throughout year in the water of Lake Tega in Japan, identified as a eutrophic lake. Higher TOC inventory was found in spring, and TOC inventory was correlated with organic carbon production rate. Total annual riverine outflow of TOC was approximately 300MgC larger than the inflow of TOC. Based on the results of inorganic and organic carbon in Lake Tega, we made a comprehensive evaluation of the role of this lake to the atmospheric CO₂ concentration. Lake Tega releases CO₂ to the atmosphere from lake water at a twice rate of the mean rate of global lakes. On the other hand, this lake self-constrains the CO₂ release rate due to changing inorganic carbon into organic matter which cannot exchange to the atmospheric CO₂, by the higher productivity.