Up-flow column percolation tests are used at laboratory scale to assess the leaching behavior of hazardous substance from contaminated soils in a specific condition as a function of time. Monitoring the quality of these test results inter or within laboratory is crucial, especially if used for Environment-related legal policy or for routine testing purposes. We tested three different sandy loam type soils (Soils I, II and III) to determine the reproducibility (variability inter laboratory) of test results and to evaluate the difference in the test results within laboratory. Up-flow column percolation tests were performed following the procedure described in the ISO/TS 21268–3. This procedure consists of percolating solution (calcium chloride 1 mM) from bottom to top at a flow rate of 12 mL/h through softly compacted soil contained in a column of 5 cm diameter and 30 ± 5 cm height. Eluate samples were collected at liquid-to-solid ratio of 0.1, 0.2, 0.5, 1, 2, 5 and 10 L/kg and analyzed for quantification of the target elements (Cu, As, Se, Cl, Ca, F, Mg, DOC and B in this research). For Soil I, 17 institutions in Japan joined this validation test. The up-flow column experiments were conducted in duplicate, after 48 h of equilibration time and at a flow rate of 12 mL/h. Column percolation test results from Soils II and III were used to evaluate the difference in test results from the experiments conducted in duplicate in a single laboratory, after 16 h of equilibration time and at a flow rate of 36 mL/h. Overall results showed good reproducibility (expressed in terms of the coefficient of variation, CV, calculated by dividing the standard deviation by the mean), as the CV was lower than 30% in more than 90% of the test results associated with Soil I. Moreover, low variability (expressed in terms of difference between the two test results divided by the mean) was observed in the test results related to Soils II and III, with a variability lower than 30% in more than 88% of the cases for Soil II and in more than 96% of the cases for Soil III. We also discussed the possible factors that affect the reproducibility and variability in the test results from the up-flow column percolation tests. The low variability inter and within laboratory obtained in this research indicates that the ISO/TS 21268–3 can be successfully upgraded to a fully validated ISO standard.
Due to the 2011 off the Pacific Coast of Tohoku of March 11, 2011, a large scale tsunami hit the Pacific coast area of the Tohoku and North-Kanto Regions, Japan. As a result of the earthquake and subsequent tsunami, approximately 900,000 tons of the tsunami-related deposits were left in the flooded area in Kesennuma city, Miyagi Prefecture. Since they were expected to be certainly recycled as embankment or backfilling materials in the prospective restoration and reconstruction works, proper treatment and management were essentially required for the tsunami-related deposits. Additionally, rapid completion of the treatment project was also important for the local residents to preserve living environment and improving public health. Thorough our laboratory experiments and a field demonstration to select soil modification materials for the tsunami-related deposits, both gypsum-based and lime-based materials were effectively accelerating dry sieving process. A part of the tsunami-related deposits contained naturally occurring heavy metals and required an additional treatment for immobilization. Elution concentration of arsenic and fluorine could be controlled stably below their criteria by using magnesia-based material. This paper summarizes the outline of the treatment of tsunami-related deposits and describes the geotechnical properties of recycled geomaterials in Kesennuma treatment area.
This paper presents the CO 2 fixation properties of steel slag containing calcium, and proposes a geotechnical application for the formation of a sound material-cycle society and a low-carbon society. In order to investigate the properties of CO 2 fixation, CO 2 fixation test with vented constant flow was conducted. As a result, when the CO 2 concentration 4500 L-CO2 /L was vented in a specimen by 0.05 L/min, non-aging steelmaking slag amount of CO 2 fixed is the maximum, the value was 0.04 g-CO2 /g-slag. The amount of CO 2 that is fixed in the steelmaking slag was about 20% of water-soluble calcium. Therefore, a possibility that the quantity of CO2 fixation could be evaluated was shown from the viewpoint of the mechanism of CO 2 fixation using the quantity of water-soluble calcium.
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