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41.
Sources of uncertainty in estimating stream solute export from headwater catchments at three sites
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Ruth D. Yanai Naoko Tokuchi John L. Campbell Mark B. Green Eiji Matsuzaki Stephanie N. Laseter Cindi L. Brown Amey S. Bailey Pilar Lyons Carrie R. Levine Donald C. Buso Gene E. Likens Jennifer D. Knoepp Keitaro Fukushima 《水文研究》2015,29(7):1793-1805
Uncertainty in the estimation of hydrologic export of solutes has never been fully evaluated at the scale of a small‐watershed ecosystem. We used data from the Gomadansan Experimental Forest, Japan, Hubbard Brook Experimental Forest, USA, and Coweeta Hydrologic Laboratory, USA, to evaluate many sources of uncertainty, including the precision and accuracy of measurements, selection of models, and spatial and temporal variation. Uncertainty in the analysis of stream chemistry samples was generally small but could be large in relative terms for solutes near detection limits, as is common for ammonium and phosphate in forested catchments. Instantaneous flow deviated from the theoretical curve relating height to discharge by up to 10% at Hubbard Brook, but the resulting corrections to the theoretical curve generally amounted to <0.5% of annual flows. Calibrations were limited to low flows; uncertainties at high flows were not evaluated because of the difficulties in performing calibrations during events. However, high flows likely contribute more uncertainty to annual flows because of the greater volume of water that is exported during these events. Uncertainty in catchment area was as much as 5%, based on a comparison of digital elevation maps with ground surveys. Three different interpolation methods are used at the three sites to combine periodic chemistry samples with streamflow to calculate fluxes. The three methods differed by <5% in annual export calculations for calcium, but up to 12% for nitrate exports, when applied to a stream at Hubbard Brook for 1997–2008; nitrate has higher weekly variation at this site. Natural variation was larger than most other sources of uncertainty. Specifically, coefficients of variation across streams or across years, within site, for runoff and weighted annual concentrations of calcium, magnesium, potassium, sodium, sulphate, chloride, and silicate ranged from 5 to 50% and were even higher for nitrate. Uncertainty analysis can be used to guide efforts to improve confidence in estimated stream fluxes and also to optimize design of monitoring programmes. © 2014 The Authors. Hydrological Processes published John Wiley & Sons, Ltd. 相似文献
42.
Young kerogens isolated from seven freshwater lakes, six river mouths and four marine surface sediments were subjected to pyrolysis in vacuo. Their pyrolysates were trapped and separated subsequently for determination of hydrocarbons, fatty acids and alcohols. The abundances, carbon number distributions of long (C12) polymethylene chain lipid compounds and relative abundances of pristenes are proposed as possible indices applicable to discrimination between young kerogens from freshwater lacustrine and marine sediments. Some oil-shale kerogens of Eocene and Permian age were pyrolyzed in the same way, where the chain-length distributions of the pyrolysis products showed similar trends as those observed for the pyrolysis of young kerogens. 相似文献
43.
Nitrate pollution of groundwater in the Yellow River delta,China 总被引:8,自引:0,他引:8
Jianyao Chen Makoto Taniguchi Guanqun Liu Kunihide Miyaoka Shin-ichi Onodera Tomochika Tokunaga Yoshihiro Fukushima 《Hydrogeology Journal》2007,15(8):1605-1614
Nitrate pollution of groundwater in the Yellow River delta, China is an important issue related not only to nitrate dispersion and health concerns but also to mass transport and interactions of groundwater, sea, and river waters in the coastal area. The spatial distribution of nitrate, nitrate sources, and nitrogen transformation processes were investigated by field surveys and geochemical methods. Nitrate occurred mainly in shallow layers and had a spatial distribution coinciding with geomorphology and land/water use. Irrigation water from the Yellow River and anthropogenic waste are two main nitrogen sources of nitrate in the delta, and both denitrification and mixing processes could take place according to characteristics identified by ionic and isotopic data. 相似文献
44.
Toshio Fukushima 《Journal of Geodesy》2018,92(12):1371-1386
We developed an accurate method to compute the gravitational field of a tesseroid. The method numerically integrates a surface integral representation of the gravitational potential of the tesseroid by conditionally splitting its line integration intervals and by using the double exponential quadrature rule. Then, it evaluates the gravitational acceleration vector and the gravity gradient tensor by numerically differentiating the numerically integrated potential. The numerical differentiation is conducted by appropriately switching the central and the single-sided second-order difference formulas with a suitable choice of the test argument displacement. If necessary, the new method is extended to the case of a general tesseroid with the variable density profile, the variable surface height functions, and/or the variable intervals in longitude or in latitude. The new method is capable of computing the gravitational field of the tesseroid independently on the location of the evaluation point, namely whether outside, near the surface of, on the surface of, or inside the tesseroid. The achievable precision is 14–15 digits for the potential, 9–11 digits for the acceleration vector, and 6–8 digits for the gradient tensor in the double precision environment. The correct digits are roughly doubled if employing the quadruple precision computation. The new method provides a reliable procedure to compute the topographic gravitational field, especially that near, on, and below the surface. Also, it could potentially serve as a sure reference to complement and elaborate the existing approaches using the Gauss–Legendre quadrature or other standard methods of numerical integration. 相似文献
45.
Fan Yang Bunkei Matsushita Takehiko Fukushima 《ISPRS Journal of Photogrammetry and Remote Sensing》2010,65(5):479-490
The impervious surface area (ISA) has emerged not only as an indicator of the degree of urbanization, but also as a major indicator of environmental quality for drainage basin management. However, since almost all of the methods for estimating ISA have been developed for urban environments, it is questionable whether these methods can be successfully applied to drainage basins, such as those found in Japan, which usually have more complicated vegetation components (e.g. paddy field, plowed field and dense forest). This paper presents a pre-screened and normalized multiple endmember spectral mixture analysis (PNMESMA) method, which includes a new endmember selection strategy and an integration of the normalized spectral mixture analysis (NSMA) and multiple endmember spectral mixture analysis (MESMA), for estimating the ISA fraction in Lake Kasumigaura Basin, Japan. This new proposed method is superior to the previous methods in that the estimation error of the proposed method is much smaller than the previous SMA- or NSMA-based methods for drainage basin environments. The overall root mean square error was reduced to 5.2%, and no obvious underestimation or overestimation occurred for high or low ISA areas. Through the assessment of environmental quality in Lake Kasumigaura Basin using the ISA fraction, the results showed that the basin has been in the impacted category since 1987, and that in the two decades since, the environmental quality has continued to decline. If this decline continues, then Lake Kasumigaura Basin will fall into the degraded category by 2017. 相似文献
46.
Hadi Ghasemi Mehdi Zare Yoshimitsu Fukushima Fereidoon Sinaeian 《Soil Dynamics and Earthquake Engineering》2009
Shear wave velocity, measured recently at 107 strong motion stations, is a new empirical basis in the applicability investigation of empirical classification techniques. These stations are classified considering Iranian Practice Code criteria (Standard 2800). To check the applicability of empirical methods, three different empirical techniques are applied to re-classify the stations using previously determined site classes. The first method is based only on the determination of peak periods at each station. It is found that the fundamental periods in different site categories are within the ranges proposed by Japanese Road Association. The second one is upon the site classification index (SI), suggested by Zhao et al. In this study, a new site index term is proposed for quantitative site classification using the empirical H/V spectral ratio (here after HVRS) method. It is shown that the results from this scheme are comparable with those obtained by applying the method of Zhao et al. and are more reliable than the results from using only peak periods. A large number of strong motion stations are classified in Iran for more control of proposed SI applicability. The mean response spectral ratio curves for all data of ISMN stations are found to be fairly consistent with those obtained by Zhao et al. The results show the practicability and efficiency of the proposed method in site classification. However, more shear wave measurements and further information, like surface geology, borehole data etc., are still needed to clarify the uncertainties of such empirical schemes. 相似文献
47.
An empirical spectral ground-motion model for Iran 总被引:4,自引:3,他引:1
A new ground-motion prediction equation for 5%-damped horizontal spectral acceleration applicable to Iran is presented. On
the basis of analysis of variance (ANOVA), selected West-Eurasian records are added to an existing dataset of Iranian accelerometric
data to yield a ground-motion prediction equation applicable at wider ranges of magnitude and distance. The advantages of
using this model rather than those proposed previously for Iran are discussed by considering the distribution of residuals
against the explanatory variables, magnitude and distance. The applicability of the proposed model, as well as those of several
other models developed for shallow crustal environments, is also investigated by means of statistical tools. The results reveal
the overall suitability of the new model as well as the validity of models developed using mainly Eurasian strong-motion records.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
48.
Toshio Fukushima 《Celestial Mechanics and Dynamical Astronomy》1999,75(3):201-226
We developed a procedure to solve a modification of the standard form of the universal Kepler’s equation, which is expressed
as a nondimensional equation with respect to a nondimensional variable. After reducing the domain of the variable and the
argument by using the symmetry and the periodicity of the equation, the method first separates the case where the solution
is so small that it is given an inverted series. Second, it separates the cases where the elliptic, parabolic, or hyperbolic
standard forms of Kepler’s equation are suitable. Here the separation is done by judging whether detouring these nonuniversal
equations will cause a 1-bit loss of information to their nonuniversal solutions or not. Then the nonuniversal equations are
solved by the author’s procedures to solve the elliptic Kepler’s equation (Fukushima, 1997a), Barker’s equation (Fukushima,
1998), and the hyperbolic Kepler’s equation (Fukushima, 1997b), respectively. And their nonuniversal solutions are transformed
back to the solution of the universal equation. For the rest of the case, we obtain an approximate solution by solving roughly
the approximated cubic equation as we did in solving Barker’s equation. Then the correction to the approximate solution is
obtained by Halley’s method precisely. There the special function appeared in the universal equation is rewritten into a combination
of similar special functions of small arguments, so that they are efficiently evaluated by their Taylor series. Numerical
measurements showed that, in the case of Intel Pentium II processor, the new method is 10–25 times as fast as Shepperd’s method
(Shepperd, 1985) and 7–13 times as fast as the standard Newton method.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
49.
Precise computation of acceleration due to uniform ring or disk 总被引:1,自引:0,他引:1
Toshio Fukushima 《Celestial Mechanics and Dynamical Astronomy》2010,108(4):339-356
We describe a precise numerical method to evaluate the acceleration vector of an inverse-square force law caused by a uniform
ring or disk. The method consists of two parts. One is rewriting of the analytic expressions of the vector to reduce the loss
of information in its computation. The other is a procedure to compute a special linear combination of the complete elliptic
integrals of the first and the second kind appeared in the rewritten expressions. 相似文献
50.
Use of flood chronology for detailed environmental analysis: a case study of Lake Kizaki in the northern Japanese Alps,central Japan 总被引:1,自引:1,他引:0
Takuma Ito Haruka Iwamoto Koichi Kamiya Takehiko Fukushima Fujio Kumon 《Environmental Earth Sciences》2010,60(8):1607-1618
This paper presents a study of the usefulness of flood layers as a time marker in sediments and a report of a case study of
Lake Kizaki in central Japan. A flood layer can be identified as a layer having a higher density, coarser grain size, lower
TN content, and higher C/N ratio than those of the upper and lower horizons. It can also be characterized by a hyperpycnal
sequence composed of a basal coarsening-upward unit and a top fining-upward unit. When flood layers can be correlated with
heavy rains in meteorological records, detailed age markers are well established in the sediment. Five flood layers were identified
in the surface sediment of Lake Kizaki, and they could be attributed to the historical heavy rainfalls that took place on
July 12, 1995; September 28, 1983; August 25, 1974; September 26, 1959; and September 1, 1949 under the constraint of an age
model. A precise age model is essential to clarify the environmental changes such as the pollutant history in detail. 相似文献