Wax and wane of Chattonella (Raphidophyceae) bloom with special reference to competition between Skeletonema (Bacillariophyceae) in the Ariake Sea, Japan

The raphidophyte Chattonella and the bacillariophyte Skeletonema are representative bloom-causing organisms in the Ariake Sea, Japan. Changes in their abundance were monitored to clarify the role of river discharge in the red tides caused by these organisms in the innermost area of the sea. In late June 2010, heavy rain occurred and subsequently river discharge increased. A Chattonella bloom occurred after heavy rain on July 5, although Chattonella abundance was very low (<1?cell?ml^?1) before the heavy rain (June 29). Maximum cell density reached 4.2?×?10³?cells?ml^?1 at the surface. Thus, the bloom developed as the river plume extended in the estuary. During the course of extension of the river plume, the Chattonella population rapidly developed using the nutrients supplied by the river. Just after the Chattonella bloom, heavy rain occurred again and a very large quantity of river water flowed into the estuary. Consequently, the salinity of the surface decreased to 5 in the study area on July 16. Chattonella did not migrate to the surface probably because of the overlying low-salinity water; Chattonella formed a thin layer (20–50?cm in thickness) at the depth where salinity was 10. However, a Skeletonema population developed at the surface. On July 20, Skeletonema density at the surface exceeded 10⁵?cells?ml^?1. With the decline of the Skeletonema abundance due to the nutrient limitation, Chattonella again formed bloom probably using deep-nutrient pool by their vertical migration behavior. The present study clearly demonstrates that the Chattonella can form dense bloom after the heavy rain. The seed population awaiting the river discharge is probably essential to the rapid development of Chattonella in the estuary.     

Primary migration theory of petroleum and its application to petroleum exploration

Current concepts of oil and gas generation by thermal decomposition of kerogen are reviewed. Primary oil migration mechanisms requiring large quantities of water to serve as a carrier for the movement of oil from source rock to reservoir are discussed. Previous investigators regarded the expulsion of interlayer water from montmorillonite and montmorillonite-illite mixed-layer minerals by transformation during diagenesis as the most important source of the carrier water.The process of diagenesis is subdivided into three stages based on the results of experimental compaction studies on montmorillonite clay, on studies of the expulsion mechanism of interlayer and interstitial waters, and on the observed changes in pores and mineral grains in argillaceous sediments during these stages. As a result, we concluded that the migration of oil chiefly occurs during the late compaction stage when the sediment's porosity ranges from 30 to 10%.This conclusion implies that a large amount of oil can move during the period when the active generation of oil corresponds with the primary migration of carrier water. For instance, in the oil-bearing Miocene sediments of the Akita area of northern Japan, the oil generation temperature ranged from 100 to 150°C and the average migration depth was between 1300 and 2600 m. Therefore, the possibility of large oil pool formation will be high in the basin where the paleo-geothermal gradient is about 5.0°C/100 m. In fact, it is expected that the paleo-geothermal gradients in the vicinities of large oil fields will be very close to this value.Prediction of the type and amount of hydrocarbons in the exploration area will be possible by an examination of the paleo-geothermal gradient in the area and by a study of the relation between absolute porosity and burial depth of argillaceous rocks.     

Kinetics of intracrystalline cation redistribution in olivine and its implication

The rate of cation redistribution between M 1 and M 2 sites in olivine is theoretically studied on the basis of elementary processes of cationic migration. Cationic migration in olivine structure is assumed to be the superposition of a unit exchange of cations between closely spaced couple of sites. Such a process gives rise to both cation redistribution and also cationic interdiffusion in olivine crystal. The time constant of cationic equilibration in the redistribution reaction is related to the interdiffusion coefficient along b-axis, and its numerical value is given as a function of temperature and composition in Mg-Fe olivine. This time constant is very short, e.g., in the order of 10^?2～10^?4 s at 1000 ° C. The temperature dependence of cation distribution in Mg-Fe olivine could not be detected by heating and quenching experiments in some previous works, because of insufficient cooling rate. A skepticism is presented for the utility of cation distribution as a geothermometer or rate meter of cooling. Cation redistribution in olivine in the deep upper mantle is sufficiently fast to take place almost in phase with the seismic waves of long periods.     

Physicochemical Environment during the Formation of the Mozumi Skarn-type Pb–Zn–Ag Deposit at the Kamioka Mine, Central Japan: A Thermochemical Study

Abstract: The physicochemical environment during the ore formation of the Mozumi skarn-type Pb–Zn–Ag deposit, Kamioka mine, Central Japan is discussed with silicate phase equilibria using calculated phase diagrams. The mineral assemblages, mineral chemistry, and fluid inclusion data are coupled with thermodynamic calculation to estimate the stability fO2–XCO2condition of the mineral assemblages at each ore formation stage. The skarn was approximated by the model system CaO–A12O3–FeO–SiO2–O2–CO2–H2O including grossular-andradite garnet and clinozoisite-epidote solid solutions. The solid solutions are combined into the calculation using "pseudocompound approximation", and real boundary of the mineral assemblages other than simple activity corrected diagram was provided. The diagrams also show isoplethal contour for garnet and epidote.     

Significance of stemflow in groundwater recharge. 1: Evaluation of the stemflow contribution to recharge using a mass balance approach

Stemflow was evaluated in a water balance and its contribution to groundwater recharge determined. Gross precipitation, throughfall and stemflow were measured for one year in a pine forest (Tsukuba, Japan) to determine each component of the water balance in the forest. Groundwater recharge rates by stemflow and throughfall were calculated from a mass balance method using chloride in subsurface waters. The stemflow in the water balance was relatively small when estimated as a value per canopy projected area of the tree in the forest. However, the results for the mass balance of chloride in subsurface waters indicated that it was impossible to disregard the stemflow in determining groundwater recharge. Although the ratio of stemflow to the net precipitation was small in the water balance, the effect of stemflow on groundwater recharge was relatively large.     

Impact of climate and land-use changes on hydrological processes and sediment yield—a case study of the Be River catchment,Vietnam

Abstract

The impact of climate and land-use changes on hydrological processes and sediment yield is investigated in the Be River catchment, Vietnam, using the Soil and Water Assessment Tool (SWAT) hydrological model. The sensitivity analysis, model calibration and validation indicated that the SWAT model could reasonably simulate the hydrology and sediment yield in the catchment. From this, the responses of the hydrology and sediment to climate change and land-use changes were considered. The results indicate that deforestation had increased the annual flow (by 1.2%) and sediment load (by 11.3%), and that climate change had also significantly increased the annual streamflow (by 26.3%) and sediment load (by 31.7%). Under the impact of coupled climate and land-use changes, the annual streamflow and sediment load increased by 28.0% and 46.4%, respectively. In general, during the 1978–2000 period, climate change influenced the hydrological processes in the Be River catchment more strongly than the land-use change.

Editor Z.W. Kundzewicz; Associate editor Q. Zhang

Citation Khoi, D.N. and Suetsugi, T., 2014. Impact of climate and land-use changes on hydrological processes and sediment yield—a case study of the Be River catchment, Vietnam. Hydrological Sciences Journal, 59 (5), 1095–1108.     

Late Quaternary activity and dextral strike-slip movement on the Karakax Fault Zone, northwest Tibet

Field observations and interpretations of satellite images reveal that the westernmost segment of the Altyn Tagh Fault (called Karakax Fault Zone) striking WNW located in the northwestern margin of the Tibetan Plateau has distinctive geomorphic and tectonic features indicative of right-lateral strike-slip fault in the Late Quaternary. South-flowing gullies and N–S-trending ridges are systematically deflected and offset by up to ~ 1250 m, and Late Pleistocene–Holocene alluvial fans and small gullies that incise south-sloping fans record dextral offset up to ~ 150 m along the fault zone. Fault scarps developed on alluvial fans vary in height from 1 to 24 m. Riedel composite fabrics of foliated cataclastic rocks including cataclasite and fault gouge developed in the shear zone indicate a principal right-lateral shear sense with a thrust component. Based on offset Late Quaternary alluvial fans, ¹⁴C ages and composite fabrics of cataclastic fault rocks, it is inferred that the average right-lateral strike-slip rate along the Karakax Fault Zone is ~ 9 mm/a in the Late Quaternary, with a vertical component of ~ 2 mm/a, and that a M 7.5 morphogenic earthquake occurred along this fault in 1902. We suggest that right-lateral slip in the Late Quaternary along the WNW-trending Karakax Fault Zone is caused by escape tectonics that accommodate north–south shortening of the western Tibetan Plateau due to ongoing northward penetration of the Indian plate into the Eurasian plate.     

Characterization of a landslide-triggered debris flow at a rainforest-covered mountain region in Brazil

Natural Hazards - Debris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies,...     

A simple generalization of wisdom's perturbative method

A simple generalization of Wisdom's perturbative method, as originally proposed by Wisdom (1985), is obtained. Any number of resonant cosines can be handled and the method can also accommodate more involved disturbing functions. Averaged trajectories are easily obtained by drawing level curves of the action. Here, the method is first tested for simple models of 3:1 and 2:1 resonant problems. Comparisons with numerical integration and surface-section curves show very good agreements.     

Line width observation of Heii 4686 Å and Hei 4713 Å in the chromosphere

Line profiles of He ii 4686 Å and He i 4713 Å from active regions in the chromosphere were observed during the total solar eclipse of February 16, 1980, with a grazing incidence objective grating spectrograph. The Doppler width of the He i triplet line of 4713 Å increases with height and the average width is compatible with width of metallic and hydrogen lines, suggesting that the kinetic temperature of He i triplet emitting region is T 8000 K. This can only be explained by recombination after photo-ionization due to coronal UV radiation. The Doppler width of the Paschen line of He ii 4686 is, without any correction for the separation of subcomponents of the line nor non-thermal velocity, 18.4 km s^-1. This line width also shows a tendency to increase with height. After comparison with Doppler widths of He i 4713 and the EUV lines, and a necessary subtraction of non-thermal velocity, it is shown that this line is emitted in a 2 × 10⁴ K temperature region, which again supports the view that this line is emitted through the recombination process after photoionization due to coronal XUV radiation below 228 Å.