Graphite-furnace atomic absorption spectrometry (GFAAS) is one of the most widely used techniques for the determination of trace elements in water. However, its sensitivity for cadmium and lead is not sufficient for a direct determination of these elements in drinking water. So far, many techniques have been used for the enrichment of trace elements in water samples. One of the most important conditions of the enrichment techniques is simple connection to the subsequent determination techniques. When the desired trace elements can be quantitatively extracted on a small amount of fine particles, a method based on the collection of particles by filtration, the preparation of a suspension in a small volume and the determination by suspensionintroduction GFAAS is favorable. Chelating ionexchange resins 1-7 and ion-exchange resins 8 and activated carbon 9-12 with complexing agents have been used for this purpose. Another technique was recently reported in which a part of the resin thin layer was cut and inserted in a cuvette for the determination by electrothermal AAS. 13The aim of this work was to develop a simple preconcentration method for the determination of cadmium and lead in tap water with the combined use of a finely divided ion-exchange resin and APDC. Fine resin particles are well suited for the rapid collection of the desired trace elements from a large sample of aliquots. 8 Since the ion-exchange resin particles have both hydrophilic and hydrophobic properties, they can act as a hydrophilic organic solid in the bulk solution, and can extract species with hydrophobic properties. APDC was selected for the simultaneous extraction of cadmium and lead on the resin particles. The proposed method was applied to the determination of cadmium and lead in tap water supplied to our laboratory. Experimental ApparatusA Hitachi Zeeman-effect GFAAS (Model Z-8270) equipped with an auto-sampler (Model SSC-300) was used for measuring the atomic absorption of cadmium and lead. The instrumental operating conditions are summarized in Tables 1 and 2. A Toyo KG-25 filter holder with a membrane filter of cellulose nitrate (0.45 mm pore size, 25 mm in diameter) was used for collecting the resin particles by filtration under suction. A Branson Ultrasonic Cleaner B-42 was used for preparing the resin suspension. ReagentsAll reagents used were of analytical grade. A Yamato Model WAR-30 and a WB-21 Auto-Still were employed to purify the water used; the water was first passed through a reverse-osmosis membrane and then A rapid and simple preconcentration method based on the combined use of ammonium pyrrolidinedithiocarbamate (APDC) and a finely divided anion-exchange resin has been described for the determination of trace amounts of cadmium and lead by graphite-furnace atomic absorption spectrometry (GFAAS). Cadmium-and lead-APDC complexes were extracted simultaneously on the resin at pH 6. The resin particles holding the cadmium-and lead-APDC complexes were separated by filtration and dispersed in 1.0 ml of 0.1 mol l -1 hydrochloric ...
The "Dredger" was developed as a specialized vessel for improving the water quality of lake Kasumigaura by dredging its muddy bottom ooze.Unlike normal dredging with a dredger, ooze dredging is a dredging operation performed under difficult constraints, namely, removing only the very oozy sludge built up on the surface layer of the lake bottom (about 30 cm thick) having a water content rate of 200-400% and including much phosphorus and nitrogen. Up till now, ooze dredging has presented many problems: because the mud content ratio is low and has a wide variation and the positioning of the ship and operation of the ladder is done by hand, ooze dredging has been of poor precision, with the dredging being either too deep or too shallow, and the operating efficiency has been low because the actual mud lifting time amounts to only a small fraction of the dredging time, and many workers are required.By working to overcome these technical problems, developing and improving the dredging equipment, and developing a dredging automatic control algorithm to greatly automate the operations, an automated dredger dubbed the "Kasumizaurus" has been completed.The automated system is divided broadly into an automatic control part for the dredging operation and an operation monitoring part for the operation of work management.The Kasumizaurus, which began operation in March 1995, is designed to be considerably better than a conventional ship in dredging efficiency, high-mud-content-ratio dredging, operational precision, and labor saving.
Ministry of Land, Infrastructure and Transport has been promoting computerized construction for the purpose of rationalization of construction and improvement of supervision and inspection work with regard to improvement of efficiency of construction, enhancement of safety, quality assurance and conservation of environment, etc. by effective use of information in relation to construction where IT (information technology), such as positional data acquisition technology, communication technology, and information processing technology is applied.This report describes the construction and construction management method using IT for asphalt paving work which has a predominant portion in public work projects and the results of trial work based on the method.
A 1.5-meter channel runs along the bank foot of Lake Kasumigaura, Ibaraki Prefecture. From fields and rice paddies that surround the area, soil drains into this channel and accumulates in the bottom. Unless removed, the accumulated soil degenerates the functions of the channel, and in the long run, possibly drain into .Lake Kasumigaura.With such anticipation, the Ministry of Construction has introduced the "Bank-foot channel cleaning work truck," a compact, highly mobile 11-ton truck installed with apparatuses necessary from absorbing to dewatering soil accumulated. Major advantages of the truck are: a suction robot, operated by wireless controller, runs pulling a suction hose by own driving system; and all apparatuses mounted on the truck are automatically-operated.Each apparatus was designed based on calculation and experiment, and specifications were designed to satisfy each function. Special attention was paid to the design of the suction robot, as well as to the balance between apparatuses mounted on a limited space on the truck bed.After factory testing, we conducted a site test, and confirmed that the truck has a soil collection capacity even higher than expected. However, repeated testing has shown that the truck requires further improvement. We intend to institute changes that will enhance its functions.
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