Preparation and performance of arsenate (V) adsorbents derived from concrete wastes

Solid adsorbent materials, prepared from waste cement powder and concrete sludge were assessed for removal of arsenic in the form of arsenic (As(V)) from water. All the materials exhibited arsenic removal capacity when added to distilled water containing 10–700 mg/L arsenic. The arsenic removal isotherms were expressed by the Langmuir type equations, and the highest removal capacity was observed for the adsorbent prepared from concrete sludge with heat treatment at 105 °C, the maximum removal capacity being 175 mg-As(V)/g. Based on changes in arsenic and calcium ion concentrations, and solution pH, the removal mechanism for arsenic was considered to involve the precipitation of calcium arsenate, Ca₃(AsO₄)₂. The enhanced removal of arsenic for the adsorbent prepared from concrete sludge with heat treatment was thought to reflect ion exchange by ettringite. The prepared adsorbents, derived from waste cement and concrete using simple procedures, may offer a cost effective approach for arsenic removal and clean-up of contaminated waters, especially in developing countries.     

Performance of various sub-grid scale models in large-eddy simulations of turbulent flow over complex terrain

Turbulent flow over a two-dimensional steep hill was analyzed by large-eddy simulations (LES). Here, six LES computations were carried out using four different sub-grid scale (SGS) models and two different ground surface conditions. The accuracy of these computations was assessed by comparing the results with those from an experiment by Ishihara et al. (An experimental study of turbulent boundary layer over a steep hill, Proceedings of the 15th National Symposium on Wind Engineering, 1998, pp. 61–66; J. Wind Eng. 89 (2001) 573). The results of the dynamic SGS models were in very poor agreement with those of the experiment. The poor prediction accuracy was mainly caused by the inaccurate estimation of the model coefficient near the ground surface. In order to improve the prediction accuracy of the dynamic SGS models, a hybrid SGS model, i.e., a combination of the standard Smagorinsky model and the dynamic Smagorinsky model, was introduced. The hybrid model provided very accurate predictions and produced the best results of the four SGS models compared here.     

Ozone–dioxane delignification from the cell walls of Japanese cypress (Chamaecyparis obtusa Endl.)

Delignification from the cell walls with a combination of ozone oxidation and dioxane–water extraction using thin sections of a softwood, Japanese cypress (Chamaecyparis obtusa Endl.), was studied to determine its suitability for the production of recyclable cellulose-based materials from wood waste. The visible-light absorption spectra of treated wood sections revealed that delignification from the cell walls with ozone increased with increasing ozonization time. Ozone delignification proceeded from the lumen side toward the middle lamella within the secondary wall of a cell, and it proceeded faster in early wood than in late wood within an annual ring. Mild ozonization for 10–30 min was sufficient for the removal of lignin from the cell walls when sections were extracted with dioxane after ozonization. The results obtained here demonstrate that microspectrometry coupled with the Wiesner reaction is useful for the quantitative analysis of lignin in cell walls.     

Chlorophyll maxima in Kuroshio and adjacent area

Fluorometric determination of chlorophyll a and pheopigments was carried out in the sea area off southern Japan. Maximum concentration of chlorophyll pigments was determined to be at or below the lower limit of the euphotic zone, namely from 50 to 150 m depth. To estimate the activity of phytoplankton in this maximum chlorophyll layer, changes of chlorophyll concentration and number of cells were measured in samples taken from this layer before and after exposure to different light intensities. It was concluded that the growth of shade-adapted phytoplankton and the deterioration of chlorophyll pigments by light are the main factors causing the chlorophyll maximum to occur in a rather deep oceanic layer.     

Mineral carbonation using alkaline waste and byproducts to reduce CO2 emissions in Taiwan

Environmental Chemistry Letters - Climate change induced partly by emissions of carbon dioxide (CO2) is an urgent issue worldwide, calling for advanced methods of carbon sequestration. Since...     

Movement patterns of American eels (Anguilla rostrata) between salt- and freshwater in a coastal watershed, based on otolith microchemistry

Otolith strontium:calcium ratios were used to trace lifetime movements of American eels (Anguilla rostrata) captured in salt-water bays and adjoining freshwater ponds in Prince Edward Island, Canada. Eels were classified into migratory contingents based on their movement patterns. A pond with a pool-and-weir salmonid fishway and a pond drained by a low-gradient channel contained eels that had entered freshwater at all ages, but a pond with a 2.2 m vertical spillway contained only eels that had entered freshwater in the elver year. Salt-water residents were the dominant migratory contingent in salt-water bays (85% of 39), which overturns the paradigm of obligate catadromy for this species. Freshwater residency was the sole pattern found in the pond with the vertical spillway (100% of 12) and the majority contingent in the pond with the low-gradient channel (54% of 24). Inter-habitat shifting was the dominant migratory contingent in eels sampled from the pond with the pool-and-weir fishway (85% of 20). Resident eels were established in salt- and freshwater habitats by the year after their arrival in continental waters. Eels that shifted between habitats increased their rate of inter-habitat shifting with age. The high degree of plasticity in habitat use found in this study is consistent with worldwide Anguillid patterns as revealed by Sr:Ca.An erratum to this article can be found at