Soil acidification stimulates the emission of ethylene from temperate forest soils     

徐星凯 《大气科学进展》2009,26(6):1253-1261

Soil acidification via acid precipitation is recognized to have detrimental impacts on forest ecosystems, which is in part associated with the function of ethylene released from the soil. However, the impacts of acidification on the cycling of ethylene in forest soils have not been fully taken into consideration in global change studies. Forest topsoils (0--5 cm) under four temperate forest stands were sampled to study the effects of a pH change on the emissions of ethylene and carbon dioxide from the soils and concentrations of dissolved organic carbon (DOC) released into the soils. Increasing acidification or alkalinization of forest soils could increase concentrations of DOC released into the soils under anoxic and oxic conditions. The ethylene emission from these forest topsoils could significantly increase with a decreasing pH, when the soils were acidified experimentally to a pH<4.0, and it increased with an increasing concentration of DOC released into the soils, which was different from the carbon dioxide emission from the soils. Hence, the short-term stimulating responses of ethylene emission to a decreasing pH in such forest soils resulted from the increase in the DOC concentration due to acidification rather than carbon mineralization. The results would promote one to study the effects of soil acidification on the cycling of ethylene under different forest stands, particularly under degraded forest stands with heavy acid depositions.  相似文献   

SHRIMP and electron microprobe chronology of UHT metamorphism in the Napier Complex,East Antarctica: implications for zircon growth at >1,000 °C     

Tomokazu?HokadaEmail author  Keiji?Misawa  Kazumi?Yokoyama  Kazuyuki?Shiraishi  Akira?Yamaguchi 《Contributions to Mineralogy and Petrology》2004,147(1):1-20

Zircons in ultra-high-temperature (UHT) metamorphosed paragneisses from Mt. Riiser-Larsen in the Napier Complex, East Antarctica, were dated by using ion microprobe (SHRIMP) and electron microprobe (EMP). Both SHRIMP and EMP analyses yield consistent 2520–2460 Ma age populations for garnet–orthopyroxene-bearing paragneiss and leucosomes enclosed within. The peak UHT event was dated at 2480 Ma by SHRIMP analyses on metamorphic zircons from the garnet–orthopyroxene paragneiss and those on magmatic zircons from the leucosomes which are interpreted to be formed at syn-UHT. As obtained by SHRIMP, the UHT metamorphic event was terminated no later than 2460 Ma. Minor 2520-Ma SHRIMP age suggests either the onset of prograde metamorphism or another high-grade metamorphic event unrelated to the UHT. EMP analyses on metamorphic zircons from sapphirine–quartz and osumilite-bearing magnesian paragneisses give c. 2500–2450 Ma ages. Inherited igneous zircon cores of the magnesian paragneisses yield relatively scattered EMP ages ranging over c. 3000–2650 Ma, suggesting that igneous materials of these ages sourced the protoliths of the paragneisses and that they were deposited during the interval c. 2650–2520 Ma.  相似文献   

New Indices for Characterizing Spatial Models of Ore Deposits by the Use of a Sensitivity Vector and an Influence Factor     

Katsuaki Koike  Setsuro Matsuda 《Mathematical Geology》2006,38(5):541-564

Precise spatial estimation of ore grades and impurity contents from sample data limited in amount and location is indispensable to metallic and nonmetallic resource exploration. One of the advantages of using geostatistics for this purpose is that it can incorporate multivariate data into spatial estimation of one variable. However, there are two weak points concerning technical and post-processing problems. First is the difficulty in application to geologic data in which spatial correlations are not clear because of intrinsic nonlinear behavior. Second is the absence of indices to interpret the mechanisms and factors which govern the spatial distribution. To address these problems, a spatial method of modeling based on a feedforward neural network, SLANS, which recognizes the relationship between the data value and location by considering supplementary attributes such as lithology and biostratigraphy, and a sensitivity analysis using this network were developed. These methods were applied to two case studies, genetic mechanisms of kuroko deposits and quality assessment of a limestone mine. The first case study is a spatial analysis of principal metals of kuroko deposits (volcanogenic massive sulfide deposits) in the Hokuroku district, northern Japan. It was clarified that upward and downward sensitivity vectors were distinguished near the deposits inside and outside the tectonic basin, respectively. Sensitivity analysis for the second case study showed a strong effect of crystalline limestone on the important impurity, P₂O₅ contents. Hydrothermal alteration, which could cause leaching and secondary concentration of phosphorus, is considered to have produced this effect.  相似文献   

Sensitive high-resolution ion microprobe U-Pb ages of the Latest Oligocene-Early Miocene rift-related Hidaka high-temperature metamorphism in Hokkaido, northern Japan     

Tadashi  Usuki  Hiroshi  Kaiden  Keiji  Misawa  Kazuyuki  Shiraishi 《Island Arc》2006,15(4):503-516

Abstract   In order to define the timing of granulite facies metamorphism, sensitive high-resolution ion microprobe (SHRIMP) U-Pb analyses were performed on zircons of three pelitic granulites from the lower metamorphic sequence of the Hidaka Metamorphic Belt, southern central Hokkaido, Japan. Both rounded and prismatic zircons were found in the granulite samples. The rounded zircons had thin (10–20 µm) concentric overgrowth rims on detrital cores, while the prismatic zircons did not have detrital cores. Both the overgrowth rims on the rounded zircons and the entire prismatic zircons were formed under granulite facies metamorphism and consistently yield Latest Oligocene–Early Miocene ages (23.7 ± 0.4 Ma to 17.2 ± 0.5 Ma; ²⁰⁶Pb/ ²³⁸U ages ( n  = 31) with low Th/U ratios, mostly <0.1). The internal structure of zircons and their SHRIMP U-Pb ages provide strong evidence in support of the granulite facies event occurring during the Latest Oligocene-Early Miocene. The detrital cores of rounded zircons show a huge variety of ages; Mesoarchean to Paleoproterozoic, Paleozoic to Mesozoic and Paleogene. The interior and marginal portions of the Eurasian continent including cratonic areas are suggested for their source provenances. These wide variations in age suggest that the protolith of the granulites of the lower metamorphic sequence were deposited near the trench of the Eurasian continental margin during Paleogene. The protolith of the lower metamorphic sequence of the Hidaka metamorphic belt was thrust under the upper metamorphic sequence, which had already been metamorphosed in early Paleogene. The Latest Oligocene-Early Miocene Hidaka high-temperature metamorphic event is presumed to have been caused by asthenospheric upwelling during back-arc rifting of the Kuril and Japan basins.  相似文献   

Three-Dimensional Interpolation and Lithofacies Analysis of Granular Composition Data for Earthquake-Engineering Characterization of Shallow Soil     

Katsuaki Koike  Yoshihiro Shiraishi  Eduardo Verdeja  Kenji Fujimura 《Mathematical Geology》1998,30(6):733-759

In Japan, many major cities are located on tectonic basins which are surrounded by faults and underlain by soft alluvial materials. Because these areas are subject to earthquake damages, it is important to determine their seismic engineering characteristics. Geotechnical databases which contain many borehole logs are useful information sources for this type of analysis. Each datum stored in the database has a value or an attribute, and its location is irregular in both horizontal and vertical directions. A new interpolation method based on the optimization principle is proposed here to deal with such three-dimensionally distributed data. Susceptibility of unconsolidated ground to liquefaction is known to be related to the content of loose and saturated sand. The mixture ratio of several soil types in a deposit, i.e., granular composition, is strongly influenced by the sedimentary environment. There are two numerical methods: the optimization principle method (OPM) used to determine three-dimensional distribution of granular composition and the model used to evaluate liquefaction. The application of the proposed methods to two locations in Japan indicated that the zones with high susceptibility to liquefaction were indeed those that had suffered from liquefaction during past earthquakes.  相似文献   

Three-Dimensional Geometry of Planar Magnetic Structure in the Corona     

Hakamada  Kazuyuki 《Solar physics》1998,181(1):73-85

The coronal magnetic field (CMF) during Carrington rotation 1870 is inferred by using the so-called 'potential model' with the photospheric magnetic field observed at Kitt Peak. Magnetic field lines starting at areas restricted (90deg; ± 30deg; in longitude and 0deg; ± 20deg; in latitude) in both the photosphere and the source surface of 2.5 solar radii are traced to examine fine geometrical structures of the CMF. We found a well-ordered planar magnetic structure (PMS) near 90° Carrington longitude in the corona. The PMS consists of magnetic flux of negative polarity emanating from several small areas in the photosphere. The magnetic flux expands into a wide longitudinal angle in the source surface making a planar magnetic structure.  相似文献   

Attenuation of peak ground acceleration,velocity and displacement based on multiple regression analysis of japanese strong motion records     

Kazuhiko Kawashima  Koh Aizawa  Kazuyuki Takahashi 《地震工程与结构动力学》1986,14(2):199-215

This paper presents the result of multiple regression analysis of 197 sets of two orthogonal horizontal strong motion acceleration records. They were obtained at 67 free field sites in Japan from 90 earthquakes with focal depth less than 60 km. Because sensitivity of the Japanese SMAC accelerograph is appreciably low at the high frequency range, instrument correction was performed on the original data. Each pair of two orthogonal horizontal components was combined in the time domain to get the maximum peak ground motions in the horizontal plane. The records were classified into three groups due to subsoil condition. With the use of multiple regression analysis, empirical formulae of attenuation of the maximum peak ground acceleration, velocity and displacement were proposed for three subsoil conditions.  相似文献   

Far-Field Tsunami Potential and a Real-Time Forecast System for the Pacific Using the Inversion Method   总被引：1，自引：0，他引：1  

Koike  Nobuaki  Kawata  Yoshiaki  Imamura  Fumihiko 《Natural Hazards》2003,29(3):425-436

Estimating tsunami potential is anessential part of mitigating tsunami disasters. Weproposed a new method to estimate the far-fieldtsunami potential by assuming faultmodels on the Pacific Rim. We find thata tsunami that generates in the areas wherethere is no tsunami in the history can damagethe Japanese coast. This shows that it isimportant to estimate tsunami potential byassuming fault models other than the pastearthquake data.Another important activity to mitigate tsunamidisasters is to provide appropriatewarnings to coastal communities when dangerfrom a tsunami is imminent. We applied anew inversion method using wavelet transformto a part of the real-time tsunami forecastsystem for the Pacific. Because this inversionmethod does not require fault location, it ispossible to analyze a tsunami in real timewithout all seismic information. In order tocheck the usability of the system, anumerical simulation was executed assuming anearthquake at sea off Taiwan. The correlationcoefficient for the estimated initialwaveform to the assumed one was calculatedto be 0.78. It takes 90 min to capturetime-series waveform data from tsunamigauges and 5 sec to estimate the 2-D initialwaveform using the inversion method. After that,it takes 2 minutes to forecast thetsunami heights at the Japanese coast. Since thesum of these times is less than the 105minutes transit time of the tsunami fromTaiwan to Japan, it is possible to give a warningto the residents before the tsunami attacksthe Japanese coast. Comparing the tsunamiheights forecasted by this system with thosecalculated by the fault model, the averageerror was 0.39 m. The average error ofthe arrival time was 0.007 min.  相似文献   

Pan-African Alkali Granitoids from the Sør Rondane Mountains, East Antarctica     

Zilong Li  Yoshiaki Tainosho  Jun-ichi Kimura  Kazuyuki Shiraishi  Masaaki Owada 《Gondwana Research》2003,6(4):595-605

Alkali granitoids (500-550 Ma) representing a prominent Pan-African magmatic event are widely distributed in the Sør Rondane Mountains, Dronning Maud Land, East Antarctica. Geochemically, they are granitic to syenitic in composition and show an alkaline affinity of A-type granites. They are characterized by high K₂O+Na₂O (7-13 wt%) and K₂O/Na₂O (1-2), low to intermediate Mg#, wide ranges of SiO₂ (45-78 wt%), Sr (20-6500 ppm) and Ba (40-13000 ppm) and have Nb and Ti depletion in the primitive mantle normalized diagram. The granitoids are subdivided into Group I granites, Group II granites, Lunckeryggen Syenitic Complex and Mefjell Plutonic Complex. The Group I granites have higher Mg#, Sr/Ba, Sr/Y, (La/Yb)_N and LREE/HREE, lower A/CNK, SREE and initial ⁸⁷Sr/⁸⁷Sr ratios and lack Eu anomalies compared to those with negative Eu anomalies in the Group II granites. The syenitic rocks from the Mefjell Plutonic Complex are higher in alkali, Ga, Zr, Ba, and have lower Mg#, Rb, Sr, Nb, Y, F and LREE/HREE with positive Eu anomaly, whereas the granites from the Mefjell Plutonic Complex have high LREE/HREE ratios with negative Eu anomaly. The Lunckeryggen syenitic rocks have intermediate Mg#, higher K₂O, P₂O₅, TiO₂, Fe₂O₃/FeO, Ba, Sr/Y and LREE/HREE ratios with lack of Eu anomalies and are lower in Al₂O₃, Ga, Y, Nb and Rb/Sr ratios. Based on chemical characteristics combined with isotopic data, we suggest that the Lunckeryggen syenitic body and Group I granitic bodies may be derived from the mantle-derived hot basic magma by fractional crystallization with minor assimilation. We also suggest that the Group II granites may be derived from assimilation with crustal rocks to varing degrees and then fractional crystallization in higher crustal levels (ACF model). The Mefjell Plutonic Complex seems to be derived from a heterogenetic magma source compared with other granitoids from the Sør Rondane Mountains. The syenitic rocks in the Mefjell Plutonic complex have a unique source (iron-enriched) and have a chemical affinity with the charnockites in Gjelsvikjella and western Mühlig-Hofmannfjella, but not like the Yamato syenites in adjacent areas.  相似文献   

青藏高原局地因素对近地表层地温的影响   总被引：23，自引：6，他引：23  

王绍令  丁永建  赵林  小池俊雄 《高原气象》2002,21(1):85-89

青藏高原近地表层地温既受区域性因素（高度、经度、纬度）控制，同时又受局地因素的影响。观测结果表明，高原稀疏植被地段比裸地地温高，短时期薄层雪盖起降低地温的作用，南坡比北坡地温高2－7℃，黑色沥青路面年平均温度比碎石土天然的年平均地表温度高4．5℃，亦高于其它材料的路面地温。  相似文献