Chemical and isotopic (D, 18O) compositions of 40 shallow groundwater, 14 observation well water and 2 river water samples in the Sho river fan, Toyama, northern part of central Japan, were analyzed to examine their water quality, origins and water flow in order to obtain baseline geochemical data for application of groundwater to geothermal heat pump (Geo-HP). Water temperatures of the groundwaters in the observation wells are almost constant at 15°C from surface to ca. 60 m in depth and increase up to 25°C at depth of 200 m with the thermal gradient of 6°C/100 m. This geothermal gradient is twice as high as that of the other areas in Japan, suggesting existence of high temperature geothermal sources beneath this region and a high potential for heat usage in winter. The isotopic results show that the groundwaters are a mixture of two big river waters (Sho and Oyabe rivers) and precipitation in the Sho river fan and that the contribution of infiltration from the Sho river has increased in recent 10 years. The Sho river has lower δ18O values than the Oyabe river. The groundwaters shallower than 80 m depth are of a Ca–HCO3 type. Deep groundwaters from observation wells were characterized by high in pH and HCO3 compared to the shallow groundwaters due to ion exchange with rocks containing clay minerals. The deep groundwaters are almost saturated or oversaturated with respect to calcite and dolomite, becoming confined due to the presence of an impermeable layer. In this paper, formation of calcite and iron hydroxide scale inside pipes of the Geo-HP was discussed from the chemical compositions of groundwater to examine whether the water is applicable to geothermal heat pump or not.
Understanding the source and chemical characteristics of groundwater used for sake production is an important strategy for the quality management of sake brewing. Oxygen isotope ratios (δ18O) of 96 sake samples from 19 provinces in Japan were analyzed. A good correlation was found between the sake δ18O values and groundwater δ18O values taken from previously published data, where the δ18O of sake is similar to that of the groundwater used in the sake breweries. Detailed sampling of 19 sake and groundwater samples was conducted near a sake brewery in the Hokuriku district, central northern Japan (Ishikawa and Toyama Prefectures). The δ18O of sake and groundwater in the area also showed a good correlation. Our findings indicate that the δ18O of sake can be used to identify the locality of sake production. This has the potential to help prevent fraudulent representation of the area of production. Water chemistry, hydrogen (δD) and oxygen (δ18O) isotopes of two groundwater and eighteen river water samples in Hakusan City, Ishikawa Prefecture, were analyzed to determine their origin and water flow patterns. The groundwater is of a Ca–HCO3 type similar to river water. The results show that the groundwater used to produce the “Hakusan” brand of sake originates from river water at an altitude of 360 to 450 m. This is supported by groundwater flow modeling, which also indicates that the water was sourced 2–3 km away from the sake brewery. The combined geochemical and numerical modeling approach provides a good tool for determining the source of groundwater used in sake production.
Chemistry of surface waters from the Tateyama caldera known as a site of frequent landslides in northern central Japan was investigated to obtain the relationship between their geochemical characteristics and the landslide density in the watershed. Most waters in the caldera have water chemistry of a Ca–SO4 type with high total ionic concentrations. Stream waters originating from the landslide areas have notably high sulfate concentration. Dissolution of rock-forming minerals such as plagioclase by sulfuric acid produced by oxidation of hydrothermal pyrite that was formed during alteration of volcanic rocks is responsible for the high calcium and sulfate concentration. The δ34S values of dissolved sulfate in the surface waters support this view. Intense rock weathering at the head areas of sulfate-rich streams is likely to have caused the 1964 large-scale landslide there. Positive correlation between SO42− concentration in the streams and a ratio of landslide area to the catchment area indicates a high probability of landslide in the area where SO42− concentration in water is high. Hydrogeochemical information at landslide areas has a potential of identifying the area of future landslide.
We analyzed rainwater collected from Huanjiang, China, between June, 2007 and May, 2008, with the aim of understanding the origin of the acid rain and its potential impacts on CO2 uptake by carbonate weathering in the rural areas of southwest China. The pH of the samples varied between 4.2 and 6.2, with a volume-weighted mean (VWM) of 5.1. The rainwater was characterized by high concentrations of SO42−, Ca2+, NH4+, and Mg2+. The Na+ and Cl−, Ca2+ and Mg2+, and SO42− and NO3− were mainly derived from sea salt, the Earth’s crust, and anthropogenic sources respectively. The δ34S–SO42− of the rain ranged from −5.6 to −11.0‰, with a mean value of −8.4‰, suggesting that local combustion of coal was the main source of acid rain in the region and that the effect of vehicle emissions could be disregarded. Grouping precipitation events by their air mass back-trajectories showed that anthropogenic sources of SO42− and NO3− might vary depending on air mass origin and passes. The involvement of sulfuric acid in carbonate weathering at the study site resulted in an increase in weathering rates of about 6.5% and a decrease in CO2 consumption rates by 13.8%. Further, we estimated that anthropogenic sulfate in the atmosphere, mainly from coal combustion, can cause a decrease in CO2 consumption rates of up to 9.6% in the study area. The data available at present indicate that even in rural karst regions of southwest China, involvement of anthropogenically derived sulfate can significantly decrease the carbon uptake rate of carbonate weathering.
The concentrations of rare earth elements in the waters and suspended particles from two alkaline lakes in a carbonate drainage basin of the South China Karst region were determined via ICP-MS. Sequential chemical extraction experiments were conducted on the suspended matter to investigate water-particle interaction processes. Due to their high pH, the alkaline lakes have lower concentrations of dissolved rare earth elements than those reported for most other terrestrial surface waters of the world. Linear regressions between pH and the rare earth element (REE) concentrations over a wide pH range show a “three stage model,” implying the geochemical behavior of dissolved REEs in surface waters is mainly controlled by pH. Shale-normalized patterns of dissolved REEs mainly show a marked enrichment in heavy REEs (HREE), while acid-extracted and organic REEs mainly show convex patterns and the residual fractions have flat patterns. Distinct positive La anomalies were observed in the Lake Aha and its river waters, which also exhibit a very high Mn concentration, indicating severe redox and scavenging conditions. Both negative and positive Ce anomalies were clearly observed in the dissolved phase and extracted fractions of suspended particulate matter. The positive correlation of Ce anomalies with Mn indicates that redox reactions control these Ce anomalies.
The mineralogy and chemistry of aquifer sediments of As-contaminated groundwater in Sonargaon, Bangladesh were analyzed to identify the host phases of As and to understand release mechanism of As into the groundwater. Sequential chemical extraction revealed that the As was mostly fixed in silicate(s). Iron oxyhydroxides/oxides were produced via chemical weathering of basic minerals at depths where the redox conditions experience seasonal changes with the groundwater level. The Fe–oxyhydroxides/oxides are not effective adsorbents of dissolved As at that depth. A significant amount of As, together with Si, Al, Mg, and Fe, was extracted by oxidation-decomposition of the silicates during a sequential chemical extraction process, indicating that chemical weathering of As-bearing silicate(s), which mostly occurs under oxic aqueous conditions, results in As dissolution in nature. Since chlorite is the only silicate that includes As in the aquifer sediments (Masuda et al., 2012a), chlorite decomposition in oxic groundwater is the most plausible mechanism of As release into the groundwater from aquifer sediments in the study area.
Increased emission of acidic pollutants on the Asian continent and long-distance transport of such pollutants have caused soil acidification in eastern Asia. In Japan, Hokuriku district experiences high deposition of acidic pollutants, and soil acidification and acidic fog have been observed at Mt. Tateyama in central Japan. To preserve the Mt. Tateyama ecosystem, it is necessary to understand when soil acidification began, the extent of soil acidification, and its influence on forest soil environments. The historical evolution of soil acidification in this area is not yet fully understood. In this study, we analyzed Ca, Mg, Mn, Sr, Ba, and Pb concentrations in tree-rings of a Tateyama cedar (Cryptomeria japonica) at Bijodaira, covering a record from 1915 to 1993. The radial distributions of each element in the Tateyama cedar were classified into four groups: (I) increasing concentrations toward the outermost ring (Ca2+ and Mn2+); (II) sharp decrease across the heartwood/sapwood boundary (Mg2+); (III) higher values in the late 1950s and around 1990 superimposed on the slightly increasing trend from the 1920s (Sr2+ and Ba2+); and (VI) higher values around the late 1960s to early 1980s (Pb2+). Among these elements, Ca and Pb were interpreted to have a low radial mobility in Japanese cedar. It is worthy of note that Ca concentrations in the tree rings began to increase gradually in the 1950s–1960s, and increased significantly around 1970, and reached yet higher values in the 1980s–1990s. We interpreted that these signals, suggesting higher uptake of Ca2+ from the 1950s–1960s, may be related to increased nutrient availability in the rooting zone during the early stages of acidic deposition. Potential sources of acidic deposition may be H2SO4 and HNO3 from local road building activities of the Tateyama-Kurobe Alpine route during the 1950s–1971s, regional industrial activities during the rapid economic growth in Japan during the 1960s–1970s and in Asian nations from the 1980s. Accelerated soil acidification in the 1990s is documented by a significant loss of base cations and an increase in Al3+ concentrations in the soil water in 1993 and 1996. Given that soil acidification (pH < 4.0) is still observed at Bijodaira, a deficiency of nutrient cations and Al stress at Bijodaira may have continued for at least ~20 years.
Hydrogen and oxygen isotopic analysis using an off-axis integrated-cavity output spectroscopy (OA-ICOS) was carefully checked for long-term stabilities, dependence on the injected water volume, inter-sample memory effects, and influence of salinity, with an aim to investigate whether it can be an alternative to conventional isotope ratio mass spectrometry (IRMS). Salinity (up to 4 wt.% NaCl) had no influence on measured values of δD and δ18O, therefore the OA-ICOS technique can be applied to the analysis of seawater without demineralization. Standard errors (1σ) of δD and δ18O analysis using this technique were typically 0.2–0.3‰ and 0.05–0.10‰, respectively, which are completely comparable to those of conventional dual-inlet IRMS methods. The results suggest that the OA-ICOS method can be an alternative of IRMS for δD and δ18O analysis of natural water. However, sporadic fluctuations of measured values were often encountered. This problem can be most likely ascribed to subtle individual differences in the quality of micro-syringes used.
The chemical compositions in the snow layers of vertical snow samples collected from six sites in the central mountainous area, Japan, during early spring 2004 were analyzed to investigate the long-range transportation of chemical substances from the Asian continent to the high mountainous areas in Japan. These sites included Iou-zen, at 800 m above mean sea level (AMSL) and in closest proximity to the Sea of Japan: Kongoudou-zan, at 1300 m; Nishi-Hodaka-dake, the Northern Japan Alps at 2200 m; Hachimori-yama, at 2100 m; Kiriga-mine, at 2000 m; and Yatsuga-take, the most inlying site, at 2200 m. The concentration of anthropogenic components in the snow such as non-sea-salt (nss-) SO42− and NO3− range from nearly 0 to more than 100 μeq/L. The nss-SO42−/NO3− (S/N) ratio in snow typically ranges from 0.3 to 6.3. A considerable number of samples had higher S/N ratios than those found in Tokyo, Japan, at approximately 1.6, whereas some samples had a much higher ratio of approximately 4–6, which is more similar to values found in Beijing, China, at approximately 3.2. The vertical profile pattern variations of chemical components in the snow layers were found to correspond roughly. For example, the concentrations of nss-SO42− in snow was found to reduce exponentially with increasing distance from the Sea of Japan to the Japan Alps, although the value decreased sharply at three sites located monsoon-leeward of the Japan Alps. This suggests that the anthropogenic components transported from the Asian continent with the monsoon were gradually removed from air and deposited in the snow cover as the air masses passed over the Northern Japan Alps.
The design and operation of an in situ contamination-free sampler of submarine spring water for CFCs and SF6 analysis are described. The sampler consists of three parts: inlet, water pump, and sample bottle housing; all made from CFC and SF6 free materials. Samples from a submarine freshwater spring, discharging along the southwest coast of Rishiri Island, Japan, had CFC and SF6 ages of 1960–1970, which is consistent with previously reported 3H ages. This suggests suitability of the sampler for sampling submarine springs without atmospheric and seawater contamination. Moreover, the device is suitable for the collection of water samples for assessment of geochemical tracers, such as major dissolved gases, isotopes, and inorganic solutes.