The contamination of groundwater with dissolved cationic chemical species such as Ni, Cu, Zn, Cd, Hg, and Pb has been an important concern in the past. Dissolved anionic species such as As has received a more important focus due to its prevalence in West Bengal as a toxic contaminant affecting several hundreds of thousands of people. Nitrates and phosphates from excessive use of fertilizers in agriculture and detergents in households are grim reminders of dissolved anion contamination in rural groundwater supplies. Chemical weathering of slag and fly ash recycled as cement materials can release anionic chemical species that has alarmed the industrial community. Long-lived dissolved anionic nuclides such as 14C, 36Cl, 79Se, 99Tc and 129I from radioactive wastes of the nuclear power industry are also a cause for grave concern. The behavior of dissolved anionic chemical species in the natural environment has proved to be the most important factor in determining their hazards and their accumulation in minerals that comprises rocks and soils. In this context, this paper presents a review of the chemical speciation of hazardous inorganic anions in groundwater. It is one of main objectives of the paper to depict and understand anion mobility at different pH and redox conditions in the natural geochemical environment. A substantial part focuses on adsorptive behavior of the anions onto goethite as the representative adsorbent in the natural environment. Finally, the management strategies involved in controlling hazardous inorganic anions in the natural environments, i.e., natural remediation strategies of anions, are comprehensively reviewed and discussed. The final part is reinforced by several examples of natural attenuation processes in governing the anion mobility.
The influence of water vapor pressure of surrounding environment on fracture toughness of rock is clarified, based on the results of a series of semi-circular bend (SCB) test under various water vapor pressures. The rocks used in the test are Kumamoto andesite and Kunnum basalt, and the range of water vapor pressure is from 10-3 to 103 Pa. The results obtained in this paper are summarized as follows: 1) Elastic modulus at 60% of maximum load depends on water vapor pressure, and decreases with increasing water vapor pressure. 2) Fracture toughness depends on water vapor pressure, and decreases with increasing water vapor pressure. The tendency of influence of water vapor pressure on fracture toughness is the same as that on uniaxial compressive strength or tensile strength. The relation between fracture toughness and water vapor pressure can be represented as: KIC=βp-m where β is a constant and -m is the slope of the approximated line on the logarithmic graph. The value m is 0.013 for Kumamoto andesite and 0.012 for Kunnum basalt, respectively. 3) Based on above results for the SCB test, models for load-displacement curve and for relation between crack velocity and stress intensity factor are suggested. 4) The time until fracture was calculated under the assumption of the crack velocity V= αKIn and the above equation, where α is a constant and n is stress corrosion index. It is shown that the rock mass of large n and small m should be selected to assure the stability for long term in spite of change in surrounding water vapor environment.
In this study, a series of percussive long-hole drilling tests using Inada granite was carried out to examine the effect of hole length on drilling performace. Special care was taken to clarify the attenuation of elastic wave at a sleeve coupling which connects the two rods. The main results are summarized as follows; 1) The experimental results show that penetration rate decreases and rod stress attenuates with increase of hole length or number of sleeve couplings to pass through. 2) Numerical simulation using the spring model proposed by Okubo et al. indicates that calculated results of elastic-wave amplitude and length agree well with experimental results. 3) Penetration rate was found to be proportional to transmitted energy into the rock. Specific energy in the percussive drilling test is considerably lower than that in the static penetration test.
Hydrothermally altered rocks are rich in arsenic (As). Thus the leaching of As from the rocks as muck may affect the surrounding soil and groundwater. The objective of this study is to clarify the leaching behavior of As for eleven crushed rock samples collected in Hokkaido by batch leaching experiments. The results showed that the As concentration in the leachate correlated with the As and sulfur (S) contents in rock and the SO42- and Fe concentrations in leachate, and that pyrite was detected in the rock samples that contained more sulfur. The As was also observed in the pyrite grain of the rock samples by SEM-EDX. This suggests that the mechanism of As release from altered igneous rocks used in the present work is partly explained by the congruent dissolution with pyrite that contains As as impurities. The higher correlation between As concentration in the leachate and As content in the rock means that the As content is used as an effective indicator of the necessity of leaching experiments.
The synergistic effect of polymer additives such as gelatin, polyethylene glycol (PEG) and Cl- on Cu electrodeposition behavior have been investigated by measuring the polarization curves for Cu deposition, by rotating ring-disk electrode technique and by AC impedance measurement. In the polymer additive-free solution containing Cl-, the cathode potential shifted to less noble direction with increased concentration of Cl- in solution, resulting in a decrease in grain size of deposited Cu. The rotating ring-disk electrode technique revealed that Cu deposition in the solution containing slight amount of Cl- proceeded with preceding formation of adsorbed intermediate CuClad. The reduction of intermediate CuClad to Cu seems to polarize the cathode potential for Cu deposition. In the solutions containing both polymer additives and Cl-, the cathode potential for Cu deposition was more greatly polarized and deposited Cu was consisted of smaller grains, showing evident synergistic effect of polymer additives and Cl- on Cu deposition. The Nyquist plots obtained by AC impedance techniques suggest that the reduction of CuClad to Cu is suppressed by polymer additives.
We proposed a new concept of the metal recycling system ( RtoS : “Reserve to Stock”, “artificial ore deposit design” ) in our previous paper.In the present paper, we have comprehensively examined the metal content of Japanese WEEE (Waste Electrical and Electronic Equipment) by carrying out presumption from the quantity of products and others.Most of the metals in WEEE are disposed of, and become unrecoverable form in the land fill site, now.As a result, the annual amount of Japanese WEEE was calculated to be 19.4kg/person.The quantity was almost equivalent to the amount of discharge of the EU countries’ which is said to be about 20kg/person. Moreover, the four items of home electronics which are already recycled by law in Japan, made up for 30% of WEEE weight. As for the annual amount of metals in WEEE, copper was found to be about 110,000t, lead is about 10,000t and zinc is about 20,000t.In addition, the amount of precious metals and rare metals are able to be presumed by the same method.Considering the value of each metal and the impact of an ecological rucksack, it is a serious problem that these metals are disposed of without any recovery.Especially, the large volume of rare metals has already been consumed to EEE.If any recovery system is not taken into consideration, rare metals will dissipate all over the land in the future.In the case of WEEE, however, when Cu, Au, and Ag are collected for recycling, rare metals can also be gathered with them.If rare metals are separated from WEEE by proper technique and are accumulated for reservation, we can consider them as resources.We showed a possibility of rare metals recycling that could have a self-supporting economical system by devising the collection system and by changing the recycling system related with a commercial transaction.