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Zinc was focused on as an element causing hardening retardation due to delayed hydration of Ordinary Portland Cement (OPC), and its hardening inhibitory effect and the mechanism of hardening enhancement by sodium aluminate were analyzed by X-ray diffraction and scanning electron microscopy/energy dispersive X-ray spectroscopy. The addition of zinc hydroxide retarded hardening at more than 0.3 mass%, as previously reported, and zinc produced calcium zincate hydrates (qatranaite) and inhibited the hydration of tricalcium silicate (C3S), the main component of hydration of OPC. After the zinc had been fully consumed in qatranaite formation, C3S started normal hydration. The addition of sodium aluminate caused earlier re-hydration of C3S, which was inhibited by hydration, as the hydrates produced appeared to consume zincate anions. The rapid setting effect of sodium aluminate addition was also delayed by zinc hydroxide, but it was estimated that the addition of the same amount of zinc would ensure initial strength through early formation of hydrocalumite. In the longer term, strength was considered to be more enhanced by the onset of C3S hydration. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFASs) are used in products, such as aqueous film-forming foam and fluorochemical surfactants, because of their high chemical stability. Although the use of perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) in PFASs has decreased because of replacement, many products containing them are landfilled. Determining accurate PFCA and PFSA concentrations of leachate from waste disposal sites is necessary, although reports on landfills are scarce, especially industrial waste landfills (IWLs). Little information about the fate of PFCAs and PFSAs during leachate treatment processes is available. Herein, the congener contributions of PFCAs and PFSAs in leachates of IWLs and municipal solid waste landfills (MSWLs) and changes in their concentrations before and after leachate treatment are reported. PFCA and PFSA concentrations in landfill leachates ranged from < 3.0 to 27,000 ng/L (n = 40), and concentrations in the leachates from IWLs were higher than those from MSWLs. Short-chain (C4–C9) PFCAs and PFSAs were well-detected, whereas long-chain (> C9) ones were rarely detected. Moreover, > 95% of these substances were removed in the activated carbon and reverse osmosis (RO) membrane treatments. These results suggest that activated carbon and RO membrane treatments effectively remove PFCAs and PFSAs from leachates. [ABSTRACT FROM AUTHOR]

The behaviour of carbon dioxide (CO2) and methane (CH4) emissions at the surface and below the soil cover in an industrial waste landfill under anaerobic operating conditions was evaluated for six years. This landfill contained gypsum board waste and incineration ash – a practice currently allowed because of a change in Japanese regulations. The CO2 and CH4 fluxes decreased throughout the six years of the survey. Almost all of the survey points exhibited fractions of CH4 in landfill gas emissions of <0.5 (mean values: 0.0–0.1 [surface], 0.0–0.3 [subsurface]) under anaerobic conditions. In addition, a relatively high first-order reaction rate constant for the landfill gas emissions (0.3 year−1) was observed. The landfill leachate showed a relatively high sulphate ion (SO42–) concentration, although other environmental conditions, such as the pH, oxidation–reduction potential and ammonium concentration, were not at levels that could have inhibited CH4 production. These findings suggest that the low fractions could have been related to the lower amounts of CH4 generation caused by competition between methanogens and sulphate-reducing bacteria (SRB). Therefore, SRB could play a major role in the degradation of organic carbon in the landfill. [ABSTRACT FROM AUTHOR]

The bentonite and ocean-floor clay used in hydraulic barriers for on-land and ocean waste disposal sites, respectively, act as the last defense against environmental pollution, and therefore must have high chemical resistivity and long-term stability. The primary factors that determine the hydraulic conductivity of bentonite and ocean-floor clay are the polarity and functional groups of their organic compounds as well as their concentration and hydration characteristics in solution. However, it is not known which of the organic compounds reduce the hydraulic barrier performance of clay liners, and the extent of degradation has not been quantified. Recently, high concentrations of 1,4-dioxane and bisphenol A have been detected in some waste leachates. Although these low-polarity compounds hinder the hydration reaction of clay minerals and increase the hydraulic conductivity of clay liners, the magnitude of their impact in the limited concentrations found in leachates remains unclear. In this study, long-term hydraulic conductivity tests are conducted on a bentonite liner and ocean-floor clay samples, where the permeation liquid contains 1,4-dioxane or bisphenol A. The hydraulic barrier performance is evaluated based on the hydraulic conductivity and the distribution coefficient. [ABSTRACT FROM AUTHOR]

Previous studies have shown that within a month benzene easily passes through geomembranes (PVC, LDPE, and HDPE geomembranes). This study uses diffusive permeation tests to clarify the barrier performance of geomembranes against bisphenol A and 1,4-dioxane, which have been detected in some Japanese waste leachates. Although dissolved bisphenol A can be adsorbed on the geomembranes, it does not pass through them during the testing period (at least 400 days are required for it to completely pass through 0.5-mm-thick PVC geomembranes). In addition, dissolved 1,4-dioxane is not adsorbed on any geomembranes and hardly passes through any of them (at least five years are required for it to completely pass through 0.5-mm-thick PVC geomembranes). Thus, geomembranes exhibit a good barrier performance against these two organic compounds, especially 1,4-dioxane. [ABSTRACT FROM AUTHOR]

The reuse of removed soil generated from decontamination projects in Fukushima as a recycled material for the construction of embankments has been under consideration for the sake of reducing the volume of this soil for its final disposal. Agents containing water-absorbing polymers are used in Fukushima to modify the removed soil in order to increase the separation efficiency of foreign materials and to improve the easiness of handling. As the reuse of modified soil containing organic water-absorbing materials, such as a superabsorbent polymer, is rather rare in the geotechnical field, it necessitates an investigation into the impact of the modifying agent on the leachate quality to ensure the environmental safety of the recycling project. In this study, therefore, bench scale percolation tests were conducted to examine the changes in the leachate quality of the removed soil with and without modification by an agent containing a superabsorbent polymer. The tests lasted for more than 950 days (liquid/solid ratio of over 10). The peak 137Cs concentration in the leachate from the removed soil was 8.6 Bq/L and the accumulated leaching ratio was 0.243 %. The leaching of 137Cs from the modified soil decreased by 60 % after mixing the removed soil with a 3 % water-absorbing polymer agent. The leaching of K+ and ammonia nitrogen (NH 4 +-N) was 40 % and 60 % lower, respectively, after the soil modification, while the accumulated amount of leaching of the dissolved organic carbon in the initial stage was 60 % higher. The total leachate amount collected from the modified soil was 4 % lower than that collected from the removed soil. [ABSTRACT FROM AUTHOR]

When separated soil (SS) generated from the Great East Japan Earthquake, which contains woodchips and others (WC), is utilized as ground material, microorganisms decompose the organic carbon in WC, and oxygen is consumed in the process. This reaction results in forming an anaerobic zone and generating methane gas. To effectively utilize SS as ground material, it is necessary to prevent anaerobic zone formation to ensure safety. This study clarified the relationship between WC content and the concentration of leached organic carbon (TOC) and the relationship between TOC concentration in the eluate and the oxygen consumption rate were clarified. We obtained the relationship between WC content and the extent of anaerobic zone formation from the results,. The anaerobic zone is formed below the oxygen penetration depth (L O2). L O2 rapidly decreases as the WC weight ratio increases from 0 to 1 w%, and L O2 is almost constant, i.e., around 1 to 2 m above 1 w% WC weight ratio. An increase in WC weight ratio does not significantly decrease L O2 determined by the aerobic decomposition of the solution. From the above, contamination with WC should be limited to 1 w% or less to prevent the formation of an anaerobic zone. If SS has WC above 1 w%, it is required to put a ventilating layer such as crushed stone every few meters or the other countermeasures when SS is utilized as ground material. [ABSTRACT FROM AUTHOR]

Abstract: The 2011 off the Pacific Coast of Tohoku Earthquake of March 11, 2011, caused devastating geotechnical and geo-environmental issues mainly in the coastal area of the Tohoku and North-Kanto Regions, Japan. As a result of the earthquake and subsequent tsunami, approximately 23,000Gg (23,000,000t) of disaster debris was generated, with more than 12 millionm3 of tsunami deposits left in the flooded area. The geotechnical utilization of the soil fraction in the disaster debris and tsunami deposits has presented a huge challenge to geotechnical engineers since (1) the clearance of debris and tsunami deposits is an urgent task which must be completed within a few years and (2) although a large amount of waste-mixed soil can be used in the construction of new embankments and levees to protect the coast from future tsunamis, their geotechnical properties have temporal and spatial variations. This paper summarizes the current status on the generation, clearance, and treatment and utilization of disaster debris and tsunami deposits from geotechnical and geo-environmental viewpoints. In addition, the environmental monitoring data on soil and groundwater quality conducted over the affected area is briefly reviewed. The results of several wide-area monitoring efforts conducted by different organizations indicate that no significant soil or groundwater contamination has occurred. However, the localized contamination near industrial plants where toxic chemicals leaked due to the earthquake and tsunami needs to be carefully taken into consideration during future revival and redevelopment works. Another serious geo-environmental issue is the management of the radioactive contamination of surface soils caused by the accident at the Fukushima First Nuclear Power Plant. This paper summarizes the distributions and expected behaviours of radioactive Caesium in soils and groundwater, and outlines the possible remediation options for dealing with this contamination. [Copyright &y& Elsevier]