Exploring predictors for the increase in soil CO release by dry-wet cycles

Nagano, Hirohiko*; Suzuki, Yuri*; Hiradate, Shuntaro*; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Occurrence of plastics and their association with radiocesium in the coastal rivers in Fukushima, Japan

Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Plastic debris is pervasive and persistent which allows its interaction with a range of organisms and organic and inorganic materials in the environment. Considering that plastics are considered carriers and vectors for pollutants in the aquatic environment, it is of utmost importance to elucidate the interaction between plastic debris and radionuclides. Because the accident at the Fukushima Daiichi Nuclear Power Plant caused by the Great East Japan Earthquake in 2011 led to the release of fission products, in particular radiocesium (Cs), into the environment, we aimed to elucidate the interaction between plastic debris and Cs in the environment. We selected the Kuma, Ukedo, Odaka, and Ohta Rivers of the Fukushima prefecture to collect environmental plastic and sediment samples. In addition, we adopted a newly developed ultrasound-assisted extraction technique to extract biofilm (a thin but robust layer of microbial cells embedded in an extracellular matrix) from plastics. The Cs activity concentrations in plastic-associated biofilms and river bottom sediments were determined by gamma-ray spectrometry. Our results indicate the dominance of common polymer types (i.e., polyethylene, polypropylene, polystyrene) of plastic debris in the river environments. Preliminary results of Cs analysis revealed that plastics serve as carriers for radionuclides mediated by biofilms in the coastal rivers.

Precise trace gas measurements for identifying pathways around faults and anticlinal axis; A Field survey example at Horonobe, Hokkaido, Japan

Shimo, Michito*; Niwa, Masakazu; Miyakawa, Kazuya; Yasue, Kenichi*; Tokunaga, Tomochika*; Tonokura, Kenichi*; Biraud, S.*

no journal, , 

Faults and fractures often create migration pathways for gases formed in the subsurface. To investigate the applicability of the trace gas measurement to geologic seep detection, we conducted a series of mobile methane concentration surveys using Cavity Ring-down Spectroscop technology. The results support that precise trace gas measurement can be one of the promising approaches to characterize migration pathways and sources of methane in the subsurface.

Modeling of coastal landscape evolution during the last glacial-interglacial cycle; A Case study on the Kamikita coastal plain, NE Japan

Takai, Shizuka; Sanga, Tomoji*; Shimada, Taro; Takeda, Seiji

no journal, , 

Prediction of long-term future landscape evolution is indispensable for safety assessment for intermediate radioactive waste disposal, whose safety assessment period is ~10 years. To assess the coastal landscape evolution considering the uncertainty of future sea-level change, the numerical simulation based on the landscape evolution models (LEMs) will be valuable. However, the applicability of LEMs over 10 years has not been verified in coastal areas. JAEA has developed a LEMs (JAEAsmtp) coupling hillslope and fluvial transport, tectonics, marine sedimentation, sea-level and climate change, and lithology. In this study, we demonstrate the capabilities of JAEAsmtp in assessing the coastal landscape evolution over the last glacial-interglacial cycle. Our target area (250 km) is located on the Kamikita coastal plain (sedimentary rock), where the marine terraces (MIS5e, 7, 9) are widely distributed. First, based on the marine terraces, borehole, and sonic prospecting data, the spatial distributions of the present and paleo-elevation, uplift rate, and alluvial deposits were estimated. Second, the LEMs parameters for fluvial incision and erodibilities were obtained from the slope-area analysis and soil-test data, respectively. Finally, the landscape evolution from MIS5e (125 ka) to present was simulated. By incorporating the drift sand into JAEAsmtp, the applicability was confirmed via reproducibility of the present coastal line and the distribution of alluvial deposits.