Geothermometry is fundamentally important to explore thermal processes within the Earth. An extremely popular geothermometer is the two-pyroxene thermometer, which is based on the temperature dependence of elemental partitioning between pyroxenes in a rock. This technique is ambiguous in terms of its responsiveness to change in the temperature of the system. We performed a numerical simulation of one-dimensional calcium diffusion in a clinopyroxene using Ca-Mg inter-diffusion coefficients. While applying the simulation to rock bodies with various temperature conditions and both heating and cooling rates, we investigated the time scale for the re-equilibration of elemental partitioning between enstatite and diopside. Those results enable us to evaluate the responsiveness of the two-pyroxene thermometer to change in temperature. For heating processes up to 1300°C, chemical zoning is not well developed at a heating rate faster than 10°C/yr because the duration for the diffusion is insufficient. In addition, at a heating rate 10^–4°C/yr and >1200°C, the simulated diffusion profiles show no chemical zoning. This occurs because the chemical equilibrium between the pyroxenes is achieved via elemental diffusion. For cooling processes, a rock body will cool down to closure temperature before making an observable zoning at a high cooling rate such as 100°C/yr. In addition, no detectable zoning of Ca in clinopyroxene developed under high temperature (>~1100°C) and a slow cooling rate (<~10^–4°C/yr) down to 700°C, properly reflecting temperature without detectable zoning of Ca. In contrast, for a rock body with detectable chemical zoning, it is difficult to ascertain the appropriate pyroxene temperature. Model diffusion profiles reflect conditions of changing temperature. Therefore, a graphic representation of diffusion profiles under various initial temperatures and different rates of temperature change would be useful to estimate the thermal history of rock bodies.

The strontium isotope ratio (⁸⁷Sr/⁸⁶Sr) is often used to identify the origin of agricultural products and the movement of ancient people, and a nationwide ⁸⁷Sr/⁸⁶Sr distribution map would greatly assist such studies. The Geological Survey of Japan (GSJ), AIST has already created nationwide element distribution maps using the <180 μm fraction of stream sediments, but this grain size fraction may not necessarily be suitable for mapping the ⁸⁷Sr/⁸⁶Sr isotopic ratio. Therefore, this study investigated the effect of grain size on elemental concentrations and ⁸⁷Sr/⁸⁶Sr ratios in stream sediments and compared their values with those of the source rocks. The stream sediments studied were collected from the granitic drainage basin of the Yahagi and Yada rivers in Aichi Prefecture, central Japan. The elemental concentrations and ⁸⁷Sr/⁸⁶Sr ratios of five fractions in the size range 1000–75 μm from the stream sediments of the Yahagi River tributaries varied with the grain size, and the variations corresponded to the heterogeneity of the mineral compositions in each fraction. The difference in the elemental concentrations and ⁸⁷Sr/⁸⁶Sr ratios among the sampling points was smallest in the 300–75 μm fractions, which showed ⁸⁷Sr/⁸⁶Sr and ⁸⁷Rb/⁸⁶Sr values that were closest to those of the source rocks. The coarser (>300 μm) and the fine (<75 μm) fractions of the stream sediments showed systematically higher ⁸⁷Rb/⁸⁶Sr and lower ⁸⁷Sr/⁸⁶Sr ratios than the Rb-Sr mineral isochron for the source rock, and the result suggests that 1) these fractions are enriched in K- and Rb-rich minerals such as K-feldspar, biotite, and hornblende; and 2) Sr is lost relative to Rb because of weathering processes. Furthermore, temporal variations in ⁸⁷Sr/⁸⁶Sr of the <180 μm stream sediments collected at a fixed sampling site in the Yada River were 0.001, which is smaller than the variations associated with grain size seen in the ⁸⁷Sr/⁸⁶Sr values in the granitic study area. Consequently, we concluded that, in granite areas, the <180 μm fraction of the stream sediments can be used for ⁸⁷Sr/⁸⁶Sr mapping, implying that a nationwide ⁸⁷Sr/⁸⁶Sr map can be made using sediment samples with a grain size of less than 180 μm.

The sources of 16 polycyclic aromatic hydrocarbons (PAHs) in Linfen, a coking industry city in Northern China, were studied. The overall emission amount for these 16 PAHs in 2013 in Linfen was 825.12 t, with 149.22 t identified as carcinogenic PAHs. The emission intensity of PAHs in 2013 was about 40.7 kg/km² in Linfen, which was much higher than the average intensity found in China in 2013. Most of the PAHs were generated from the combustion of domestic, industrial, and coke-production coal, accounting for 78.6% of the total emission amount. Among the emissions of these 16 PAHs, two- and three-ring PAHs made up the majority (68.15%). In the different areas (17 in total) of Linfen, the PAH emissions ranged from 143.35 t in Hongdong County to 2.64 t in Daning County. There was a positive correlation between the rural population and total PAH emissions (R² = 0.794). The estimated 16 PAH emissions in Linfen from 1995 to 2013 based on historical energy consumption data showed that the amount of PAH emissions has been gradually increasing.

Iron sulfides are thought to play critical roles in prebiotic chemistry as a synthesis reactant or a mineral catalyst to form key organic compounds and as an active center for proto-enzymes. Laboratory experiments with iron sulfides and other reactants at geologically reasonable low concentrations are essential to test this hypothesis. Therefore, organic contaminants potentially attached to iron sulfides should be removed as much as possible prior to experiments. This study measured amounts of organic contaminants in troilite and pyrite that are/were likely present in extraterrestrial and Hadean Earth hydrothermal environments, respectively. In addition, we evaluated the effectiveness of the anoxic heating (450–1000°C and 0.1 MPa), hydrothermal processing (300°C and 50 MPa), and wet chemical treatment (acid and/or organic solvents) of these reagents as pretreatments. Commercially available iron sulfide reagents contain considerable amounts of organic matter with up to 1560 ppm carbon and 30 ppm nitrogen. With the best cleaning procedure, anoxic heating removed 66% and 53% of the carbon and nitrogen from troilite, respectively, whereas it removed 25% and <10% of the carbon and nitrogen from pyrite, respectively. Anoxic heating and hydrothermal processing of the troilite reagents reduced the metallic iron impurity contents but produced small amounts of iron oxides. Clearly, future work is needed to establish more efficient protocols to substantially remove persistent organic components. However, appropriate sample selection combined with anoxic heating and mineral separation would allow the preparation of troilite or pyrite fractions with a relatively small amount of refractory organic contaminants (≤40 ppm C, ≤2 ppm N) that could not contribute to the synthesis of ammonia and polymeric biomolecules in simulated extraterrestrial and Hadean Earth hydrothermal conditions, respectively.

Dolomitization is the most striking diagenetic process affecting marine carbonates from the Quaternary-Neogene strata of the Xisha islands in the South China Sea. Petrographic and geochemical evidence from previous studies outline a diagenetic history in which dolomite has experienced a progressive maturation process indicated by textural and compositional changes from shallow to deep depth. With the goal of providing valuable insight into the role of dolomitization on REY geochemistry, rare earth element and yttrium (REY) concentrations were determined in 56 Neogene carbonate samples from the ZK-1 well in this study. The PAAS-normalized REY patterns of these carbonate samples are characterized by the following: 1) pronounced light rare-earth element (LREE) depletion with Pr_N/Yb_N ranges between 0.28 and 0.94 at an average of 0.57; 2) real negative Ce anomalies and positive La anomalies; 3) superchondritic Y/Ho molar ratios with an average of 85; and 4) moderately negative Eu anomalies with an average of 0.56. Except for the Eu anomalies, these REY distributions are similar to those found in modern seawater and are considered to be indicative of a primary marine REY signature. The presence of hydrothermal input is ruled out by negative Eu anomalies in the carbonates that likely reflect that the diagenetic environment was characterized by more reducing conditions as compared to modern seawater. Dolomitization itself did not necessarily modify the REY signatures of the precursor limestones because the REY patterns of different rock types are uniform, and no correlation exists between dolomite content and REY parameters. Gradual variations in Y/Ho values and LREE depletion with depth indicate that the REY signatures of ZK-1 carbonates depend not only on the REY source of the sedimentary fluids, but also on the degree of diagenetic REY uptake at different stages of diagenesis, which is related to the rate of meteoric influence in early diagenesis versus marine-derived alteration in late diagenesis. The latter process involves the progressive recrystallization or remobilization of dolomite during increasing burial.

Concentrations of the pesticides diuron, Irgarol 1051 and fenitrothion and the heavy metals cadmium, copper, manganese, nickel, lead, and zinc were determined in sediment core samples (n = 45) from the Seto Inland Sea in Japan. The pesticides were analyzed using a Shimadzu high-performance liquid chromatography system equipped with a UV-Vis detector. The heavy metals were analyzed using inductively coupled plasma atomic emission spectroscopy. The highest diuron, Irgarol 1051, and fenitrothion concentrations were 415, 328 and 119 ng g^–1 by dry weight, respectively. The highest cadmium, copper, manganese, nickel, lead, and zinc concentrations were 2.77, 3490, 3011, 157, 188 and 859 mg kg^–1 by dry weight, respectively. These concentrations were found in sediment cores collected near the mouth of the River Yodo in Osaka Bay. The ages of the sediment core samples were estimated using radioisotopic dating techniques, and the maximum pesticide and metal concentrations were associated with periods in which anthropogenic activities occurred on land. For example, the maximum diuron and Irgarol 1051 concentrations coincided with the time these pesticides were mostly used as antifoulants as replacements for organotin compounds (in the 1990s and 2000s). Generally, the highest heavy metal concentrations were in samples dated to the 1960s and 1970s, a period of high economic activity. Sediment samples from near the coast contained high concentrations of both heavy metals and pesticides further confirming that anthropogenic activity has affected heavy metal and pesticide concentrations in the studied coastal area. The concentrations were particularly high in areas close to cities with high population densities (such as Osaka Bay) and in areas in which rivers that pass through areas with high population densities enter the Seto Inland Sea (such as Kure Bay and Harima-nada). The contaminant concentrations were lower in the surface samples than in the deeper layers of the sediment cores. Sediment is a potential source of both pesticides and heavy metals through processes such as recirculation, so pesticides and heavy metals in sediment pose risks to aquatic organisms.

The neodymium isotope ratios (¹⁴³Nd/¹⁴⁴Nd) and rare earth element compositions of eight plant species in a well-studied Ca-depleted research forest (the Strengbach catchment) were measured. The ¹⁴³Nd/¹⁴⁴Nd ratios distributed between the higher ratio of apatite and the lower ratio of plagioclase. The ratio correlated well with the type of infected fungi. Ectomycorrhizae (EM)-infected plants tended to show lower isotope ratios than Ect-uninfected plants. This is supported by the REE abundance patterns: higher ¹⁴³Nd/¹⁴⁴Nd plants tend to show a more negative Eu anomaly. Based on the reported soil profile, the Nd isotope ratio of the surface soil is considered to be influenced significantly by Nd in plant litter. Combining Nd isotope and Eu anomaly data, the REE cycle in the catchment can largely be understood by mixing three endmembers of Ca-bearing plagioclase, apatite and carbonate in loess. EM-infected plants are estimated to incorporate 50–70% of Nd ultimately from plagioclase, whereas for non EM-infected plants, less than 30% of Nd is from plagioclase, perhaps indirectly from the recycled pool. Comparison of the results with reported mineral soil profiles and REE composition of acid leachates of soil indicates that plagioclase is dissolved by the symbiotic action of ectomycorrhizae, providing a direct evidence of active plant-induced weathering in a natural system. It is likely that plants dissolve plagioclase to compensate for insufficient Ca in soil.

Experimental studies have indicated that water-saturated magmas fractionate voluminous amphibole as a cumulus phase at depth, which is considered as a mechanism by which adakitic compositions can be produced. In the Tongling region, Lower Yangtze River belt (LYRB), widespread Late Mesozoic intrusions contain large amounts of amphibole-dominant cumulate enclaves that show adakitic affinities. Among them, the newly dated Early Cretaceous (138 Ma) Guihuachong quartz diorite intrusion is a representative with high Sr/Y (47–61) and La/Yb (22–26) ratios as well as weak Eu anomalies. The whole-rock geochemistry and the zircon Hf isotopic characteristics of the quartz diorites indicate a mixed crust-mantle source. Petrographic observations and geochemical analyses of the cumulate enclaves indicate significant amphibole and apatite fractionation during the early stages of magma evolution. In this paper, we highlight the roles of amphibole and apatite in the petrogenesis of rocks with adakitic affinities. The high-aluminum amphiboles crystallized under high-temperature conditions from a water-rich magma near the crust-mantle boundary and preferentially partitioned the middle-heavy rare earth elements (M-HREEs) over light REEs (LREEs). Under conditions of high water content and pressure, plagioclase crystallization was suppressed, which led to high concentrations of Sr and Eu in the melts. The crystallization of apatite consumed a large proportion of the Y (77.52–97.71 ppm in apatite), resulting in fractionated melts that were depleted in Y. Hence, the deep accumulation of amphibole and apatite led to the adakitic signatures of the derivative melts, which were the parent melts of the Tongling adakite-like rocks. The results of our study also indicate that continental adakites are not generated exclusively by partial melting of garnet-bearing sources during crustal thickening.

Lipids are a component of the dissolved organic matter found in natural waters. The susceptibility of lipids to oxidation suggests that lipid hydroperoxides (LHPs) may be among the hydroperoxides present in natural waters. However, the selective determination of potential LHPs among other hydroperoxides in natural waters has not been investigated. In this study, a method was developed to selectively determine LHPs in river water using the fluorescent probe Liperfluo (2-(4-diphenylphosphanyl-phenyl)-9-(3,6,9,12-tetraoxatridecyl)-anthra[2,1,9-def:6,5,10-dʹeʹfʹ]diisoquinoline-1,3,8,10-tetraone). The probe reacted selectively with LHPs to form Liperfluo-Ox, which was quantified using a flow injection analysis system (FIA) equipped with a fluorescence detector (Excitation/Emission: 495 nm/546 nm). The linear range under the optimized conditions for the reaction of Liperfluo with LHPs in MilliQ and river water was 0–500 nM LHPs. The method detection limit for LHPs, defined as three times the standard deviation of five measurements of 100 nM LHPs, was 10.1 nM in river water and 7.3 nM in MilliQ. The coefficient of variation was ≤3.8% for five replicate measurements each for 100 nM and 500 nM LHPs. The conditions and the probe used in this study showed high selectivity for LHPs over other natural water hydroperoxides, including hydrogen peroxide, methyl hydroperoxide and ethyl hydroperoxide. The method was applied to the quantification and fate determination of LHPs in water from the Kurose River (Japan). The concentrations ranged from below the detection limit to 98 nM (ave. 37.2 nM; n =12). The LHPs in river water samples were found to quickly photo-decomposed within an hour. The irradiation of LHP-spiked river water using a solar simulator resulted in an increased H₂O₂ concentration, suggesting that H₂O₂ formation may be a possible sink for LHPs in river water.

We developed a convenient sample preparation method applicable to electron probe microanalysis (EPMA) of the clay fraction of sediment. The clay fraction separated from original sediment by elutriation was pasted evenly on an area of about 1 cm × 1 cm on a copper plate. After the sample had dried at room temperature, it was subjected to EPMA analysis using the maximum electron beam diameter (30 μm). This method provides adequate results, consistent with those obtained by X-ray fluorescence in the case of intensely hydrothermally altered sediments collected from a seafloor hydrothermal field. The major merit of this method is the small amount of clay fraction required (about 10 mg), which saves time in sample preparation. We call this method the “Cu-EPMA method.”

Synchrotron radiation-based Fourier transform infrared microspectroscopy (SR micro-FTIR) was applied to ~830 Ma prokaryotic fossils in a doubly polished thin section in order to examine the micrometer-scaled spatial distributions of organic components in the microfossils. Mapping analysis allowed us to locate aliphatic C-H bonds (~2925 cm^–1 band and ~2850 cm^–1 band) in two species of microfossils (a filament and a coccoid) with a ~2 × 2 μm² rectangular aperture. The distributions of the ~2925 cm^–1 band and ~2850 cm^–1 band agree with the morphology of the filament, and also seem to be partially distributed along the wall structure of the coccoid. These results suggest that the SR micro-FTIR can provide a few microscale distributions of organic/inorganic components in prokaryotic fossils in doubly polished thin sections. However, artifacts are sometimes generated when certain analytical models are used, and some caution must be exercised to avoid their generation.