Phytoremediation of heavy metal‐contaminated water and sediment by Eleocharis acicularis

Phytoremediation is an environmental remediation technique that takes advantage of plant physiology and metabolism. The unique property of heavy metal hyperaccumulation by the macrophyte Eleocharis acicularis is of great significance in the phytoremediation of water and sediments contaminated by heavy metals at mine sites. In this study, a field cultivation experiment was performed to examine the applicability of E. acicularis to the remediation of water contaminated by heavy metals. The highest concentrations of heavy metals in the shoots of E. acicularis were 20 200 mg Cu/kg, 14 200 mg Zn/kg, 1740 mg As/kg, 894 mg Pb/kg, and 239 mg Cd/kg. The concentrations of Cu, Zn, As, Cd, and Pb in the shoots correlate with their concentrations in the soil in a log‐linear fashion. The bioconcentration factor for these elements decreases log‐linearly with increasing concentration in the soil. The results indicate the ability of E. acicularis to hyperaccumulate Cu, Zn, As, and Cd under natural conditions, making it a good candidate species for the phytoremediation of water contaminated by heavy metals.     

Changes in the hypsometric curve through mountain building resulting from concurrent tectonics and denudation

The stages of geomorphic development of mountains have sometimes been explained based on Strahler's diagram of hypsometric curves. Although the Japanese mountains are young, they do not follow his diagram. Hypsometric curves, simulated using empirical laws deduced from the Japanese mountains, indicate that mountain building resulting from concurrent tectonics and denudation does not produce convex curves but concave and/or s-shaped curves. The hypsometric curve of a mountain changes from a concave curve to an s-shaped curve in accordance with the increase in mountain altitude. The succession of the hypsometric curve during concurrent tectonics and denudation is the reverse of Strahler's diagram. The hypsometric integral increases with the advance in stage which is evaluated based on the change in mountain altitude. It has a relatively good correlation with the stage. However, the sequence of change in the hypsometric integral is different according to the extent of the terrain examined, whether the terrain is restricted to the interior of a mountain or pertains to the whole mountain, and whether it includes newly emerged land. The stage should be evaluated based on the course of change in the integral characteristics for the extent of the mountain examined.     

A model of relief forming by tectonic uplift and valley incision in orogenesis

A model for the change in shape of interfluves by concurrent tectonics and denudation was developed based on the morphometric attributes of landforms. The tributaries flowing down valley side slopes and dissecting low-relief surfaces on the interfluves are one of the most important elements for relief-forming processes. They were named as β-tributaries. The valleyhead altitude ( H ), the junction altitude ( L ) and the valley length ( l ) of the β-tributary were measured. The altitudinal difference ( h=H−L ), which indicates the local relief, and the average slope of tributary (tan θ= h / L ) were calculated. The regression analyses among H , L , l , h and tan θ indicate that the valley length, relief and slope increase with an increase in valleyhead altitude.
Based on the functional relations above, the shape of interfluve is a function of uplift, altitude and erosion. This model is used to illustrate the change in cross-section of interfluves during a period of sustained rock uplift.
Successive changes in shape of interfluve can be divided into two substages: (1) the early substage, characterized by trapezoidal cross-sections with the original low-relief surfaces and residual, shallow stream networks on the ridges; and (2) the later substage, characterized by a triangular cross-section, with the original low-relief surfaces removed and with the interfluves lowered by headward erosion of β-tributaries. In central Japan, the transitional relief from the trapezoidal to the triangular cross-section appears when the ridges of interfluves attain elevations about 1600–2000 m above sea level.     

Earthquake design considerations in reinforced concrete columns

Damages resulting from the Tokachi-Oki earthquake of 1968 demonstrated that many code-designed reinforced concrete columns do not have adequate earthquake resistance. A review of Japanese research revealed that the axial force ratio, the moment arm ratio, and the type and ratio of transverse reinforcement control the resistance and ductility of concrete columns. A recent experimental study at the Kajima Institute of Construction Technology evaluated the resistance of columns with three types of transverse reinforcement and three reinforcement ratios subjected to repeated alternating loads. Tied and spiral columns proved to be superior to hooped columns.