Characterizing the flush of stream chemical runoff from forested watersheds

A flush can be defined as stream chemical exhibiting higher concentrations during the prophase of a storm event at an event scale, or exhibiting progressively lower concentrations during several successive storms at a seasonal scale. Investigating the flush characteristics of chemical runoff from forested watersheds is important and helpful to understand the chemical dynamics as well as to design a sampling schedule strategy during storm events. Here, three parameters describing the flush characteristic are quantified and the flush characteristics of chemicals from four Japanese forested watersheds (Mie, Kochi, Nagano and Tokyo) were investigated at both event and seasonal levels. We found that the characteristics of the flush were complicated, and depended on the constituents of the hydrochemistry, climate and runoff quality. Generally, the flush occurs more readily for particulate components than for those in solution; the flush on nitrate‐nitrogen is weaker in regions of nitrogen saturation, such as Nagano and Tokyo, than in Mie and Kochi. Rainfall feature was the main factor controlling the flush of particulate components. However, the source available in a watershed plays a main role on the flushes of dissolve chemicals. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of crystallographically oriented olivine aggregates using colloidal processing in a strong magnetic field

This study develops a fabrication technique to obtain Fe-free and Fe-bearing (Fe:Mg = 1:9) olivine aggregates not only with high density and fine grain size but with crystallographic preferred orientation (CPO). A magnetic field (≤12 T) is applied to synthetic, fine-grained (~120 nm), olivine particles dispersed in solvent. The alignment of certain crystallographic axes of the particles with respect to a magnetic direction is anticipated due to magnetic anisotropy of olivine. The dispersed particles are gradually consolidated on a porous alumina mold covered with a solid–liquid separation filter during drainage of the solvent. The resultant aligned consolidated aggregate is then isostatically pressed and vacuum sintered. We find that (1) preparation of fully reacted olivine particles, with less propensity to coalesce; (2) preparation of a suspension with highly dispersed particles; and (3) application of a certain strength of the magnetic field are essential to obtain well-sintered and well-aligned aggregates. High density (i.e., <1 vol% porosity) and fine grain size (~1 μm) Fe-free and Fe-bearing olivine aggregates were successfully synthesized with uniaxially aligned a- and c-axes, respectively. Attempts to uniaxially align the magnetization hard axis and to triaxially align Fe-bearing olivine by rotating the suspension in the magnetic field succeeded in obtaining weakly developed CPO aggregates.     

Changes in stream flow regime in headwater catchments of the Yellow River basin since the 1950s

The headwater catchments of the Yellow River basin generate over 35% of the basin's total stream flow and play a vital role in meeting downstream water resources requirements. In recent years the Yellow River has experienced significant changes in its hydrological regime, including an increased number of zero‐flow days. These changes have serious implications for water security and basin management. We investigated changes in stream flow regime of four headwater catchments since the 1950s. The rank‐based non‐parametric Mann–Kendall test was used to detect trends in annual stream flow. The results showed no significant trend for the period 1956 to 2000. However, change‐point analysis showed that a significant change in annual stream flow occurred around 1990, and hence the stream‐flow data can be divided into two periods: 1956–1990 and 1991–2000. There was a considerable difference in average annual stream flow between the two periods, with a maximum reduction of 51%. Wet‐season rainfall appears to be the main factor responsible for the decreasing trend in annual stream flow. Reductions in annual stream flow were associated with decreased interannual variability in stream flow. Seasonal stream flow distribution changed from bimodal to unimodal between the two periods, with winter stream flow showing a greater reduction than other seasons. Daily stream flow regime represented by flow duration curves showed that all percentile flows were decreased in the second period. The high flow index (Q₅/Q₅₀) reduced by up to 28%, whereas the reduction in the low flow index (Q₉₅/Q₅₀) is more dramatic, with up to 100% reduction. Copyright © 2006 John Wiley & Sons, Ltd.     

Evaluation of ADEOS-II GLI ocean color atmospheric correction using SIMBADA handheld radiometer data

The performance of the “version 2” Global Imager (GLI) standard atmospheric correction algorithm, which includes empirical absorptive aerosol correction and sun glint correction, was evaluated using data collected with handheld above-water SIMBADA radiometers during 23 cruises of opportunity (research vessels, merchant ships), mostly in the North Atlantic and European seas. A number of 100 match-up data sets of GLI-derived and SIMBADA-measured normalized water-leaving radiance (nL _W ) and aerosol optical thickness (AOT) were sorted out, using objective selection criteria, and analyzed. The Root-Mean-Square (RMS) difference between GLI and SIMBADA nL _W was about 0.32 μW/cm²/nm/sr for the 412 nm band, showing improvement by 30% in RMS difference with respect to the conventional “version 1” GLI atmospheric correction algorithm, and the mean difference (or bias) was reduced significantly. For AOT, the RMS difference was 0.1 between GLI estimates and SIMBADA measurements and the bias was small (a few 0.01), but the ?ngstr?m exponent was systematically underestimated, by 0.4 on average, suggesting a potential GLI calibration offset in the near infrared. The nL _W differences were not correlated to AOT, although performance was best in very clear conditions (AOT less than 0.05 in the 865 nm band). Despite the relatively large scatter between estimated and measured nL _W , the derived chlorophyll-a concentration estimates, applying the same ratio algorithm (GLI OC4V4) to GLI and SIMBADA, were consistent and highly correlated in the range of 0.05–2 μg/l. The large variability in chlorophyll-a concentration estimate for clear clean water areas (e.g. with the concentration range lower than about 0.05 μg/l) turns out to be due to the nature of the “band ratio” based in-water algorithm.     

Vertical vibration isolator having piecewise‐constant restoring force

We present a vertical vibration isolator having a piecewise‐constant restoring force, which belongs to a class of passive and nonlinear vibration isolators. In vertical vibration isolation, direct use of low‐stiffness elements leads to unacceptably large deformations due to self‐weight. To overcome the difficulty, we apply a combination of constant‐force springs, each of which sustains a constant load regardless of its stretch. By arranging the constant‐force springs, so that the isolator has a piecewise‐constant restoring force, we alleviate the problem of the excessive deformation caused by self‐weight, provide stability at the static equilibrium state along with the self‐centering capability, and realize a large stroke while keeping the mechanism simple and compact. Further, we attempt to limit the response acceleration within a tolerance regardless of the frequency spectrum and the magnitude of earthquake ground motions. We demonstrate the effectiveness of the present isolator through shaking table tests and numerical simulations. Copyright © 2009 John Wiley & Sons, Ltd.     

An empirical spectral ground-motion model for Iran

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.     

Nutrient and Phytoplankton Dynamics in Harima-Nada, Eastern Seto Inland Sea, Japan During a 35-Year Period from 1973 to 2007

Long-term monitoring of water quality and phytoplankton was conducted at 19 sampling stations in Harima-Nada, eastern Seto Inland Sea, Japan for 35 years from 1973 to 2007. There were two significant long-term changes, an increase in winter water temperatures of 0.042°C year^?1, and a decrease in dissolved inorganic nitrogen (DIN) from about 10 μM in the 1970s to ~5 μM in the late 1990s due to the reduction in nutrient inputs. DIN concentrations and total phytoplankton cell density were both higher during the 1970s to the early 1980s and then exhibited a significant decrease in the mid 1980s and remained relatively constant thereafter. Diatoms were the dominant phytoplankton group (>90%) over the 35-year period, and there was a dramatic shift from Skeletonema dominance (~70%) to Chaetoceros in the mid 1980s. This shift in diatom species may be attributed to differences in the life cycle of Skeletonema and Chaetoceros and the response to the decrease in DIN concentration.     

Geochemical significance of lipids and lipid-derived substructures interlaced in kerogen

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.     

A system of astronomical constants in the relativistic framework

The relation between the units and readings of time and space coordinates of terrestrial and barycentric reference frames is discussed from the viewpoint of general relativity. Attention is paid to the unit of space coordinates since the International Astronomical Union (IAU) regulates only the unit of time in the above two frames. Two definitions of unit of length are examined and their effects on the numerical expression of coordinate transformation, equations of planetary motions, and those for light propagation time are discussed. A clear conflict is found between the IAU (1976) recommendation on the definition of the time-scales in different frames of reference and the statement that all constants in the IAU (1976) new system of astronomical constants are defined in terms of the Internationsl System of units (SI units). One of the above two definitions is proposed to resolve this conflict by the least alteration to current procedures for analysing the recent astrometric observations such as the radar/laser rangings, the range and range-rate, and the very long baseline interferometric observations. Also, an interpretation of numerical values in the IAU (1976) new system of astronomical constants is presented. It is stressed that the definition proposed in this paper requires that a formula slightly different from that in current use be employed in the numerical transformation of readings of coordinates between the terrestrial and barycentric reference frames.