Particle-tracking simulation for the drift/diffusion of spilled oils in the Sea of Okhotsk with a three-dimensional, high-resolution model

To conduct the simulation of oil spills in the Sea of Okhotsk, we developed a three-dimensional, high-resolution ocean circulation model. The model particularly improved the reproducibility of velocity field during the strong stratification period. Particle-tracking experiments with the effects of evaporation and biodegradation were performed using the combined data of daily ocean currents from the present model and the hourly diurnal tidal currents from the tidal model. The results are shown by the relative concentration of the particles averaged over the 8 years of 1998–2005 based on the ensemble forecast idea. For the case of particles released from the Sakhalin II oil field, the particles deployed in September–January are carried southward by the East Sakhalin Current, finally arriving at the Hokkaido coast, after 60–90 days. The particles deployed in March–August are diffused offshore by the synoptic wind drift, and hardly transported to regions south of Sakhalin. For the case of particles released from the region off Prigorodnoye, the oil export terminal, after the diffusion by the synoptic wind drift, a part of them are carried offshore of Hokkaido by the Soya Warm Current. The particles released in November–April flow out to the Japan Sea through the Soya Strait, mainly by the synoptic wind drift and secondly by the diffusion due to strong tidal currents around the Soya Strait. By considering the effects of evaporation and biodegradation, the relative concentration of the particles is considerably decreased before arriving at the Hokkaido coast, particularly in the case of drift from the Sakhalin II oil field.     

Numerical model and flume experiments of single- and two-layered hillslope flow related to slope failure

A hillslope flow model is developed considering 3D saturated and unsaturated flow of water during rainfall events. A finite difference-based numerical model of hillslope flow processes is developed. Four different experiments are done to see the effects of a single- and double-layered soil in pore-water pressure dynamics and slope failure. Results from the numerical model are verified with experimental results. The numerical and experimental values of the pore-water pressure and moisture contents are in good agreement. The results show that the hillslope heterogeneity caused by multiple layers of soil has greater influence on hillslope pore-pressure dynamics and slope failure patterns. The depth of slope failure shows high dependency on layering characteristics of the soil slope and pattern of rainfall. The proposed model provides a perspective on failure mechanism of a single- or double-layered slope under rainfall infiltration.     

Joint FAO/WHO/IOC activities to provide scientific advice on marine biotoxins (research report)

The Joint FAO/WHO/IOC ad hoc Expert Consultation on Biotoxins in Molluscan Bivalves performed risk assessments for a number of biotoxins present in bivalve molluscs. For performing risk assessments, the Expert Consultation categorized the biotoxins into eight distinct groups based on chemical structure. The Expert Consultation established LOAELs for the azaspiracid (AZA), okadaic acid (OA), saxitoxin (STX), and domoic acid (DA) toxin groups. The derived provisional acute RfDs for the AZA, OA, STX, and DA toxin groups were 0.04 μg/kg bw, 0.33 μg/kg bw, 0.7 μg/kg bw, and 100 μg/kg bw, respectively. For the yessotoxin (YTX) group, a NOAEL was established, based on animal studies. Applying a safety factor of 100, a provisional acute RfD of 50 μg/kg bw was suggested for the YTX group. The Expert Consultation considered that the database for cyclic imines, brevetoxins, and pectenotoxins was insufficient to establish provisional acute RfDs for these three toxin groups.