Isotopocule ratios of N2O (δ15N, δ18O and SP = 15N site preference within the linear N2O molecule) are useful parameters to identify sources of this greenhouse gas and provide an insight into production and consumption mechanisms in a complex bacterial system. We measured isotopocule ratios of dissolved N2O in simulated wastewater with activated sludge under variable conditions of key factors including dissolved oxygen (DO), carbon-to-nitrogen ratio (C/N ratio), mixed liquor suspended solid (MLSS), and water temperature in oxic and anoxic conditions. Under oxic condition, lower DO concentration causes greater N2O accumulation. Observed low SP (–2.6 to +7.8‰ at 25°C and –7.2 to +9.2‰ at 18°C), which is unique to N2O production pathway, and the relation of nitrogen isotope ratios between N2O and its substrate (NH4+) suggests that N2O is produced mainly by NO2– reduction by autotrophic nitrifiers (nitrifier-denitrification). The N2O production mechanism in this condition was not altered by changes in DO of 0.5–3.0 mg L–1. Under anoxic conditions, NO2– reduction by denitrifying bacteria (heterotrophic denitrification) is the dominant contributor to N2O production. Also, N2O reduction to N2 occurred simultaneously, as implied by isotopocule analysis. The C/N ratio had a negligible effect on the N2O production mechanism. During anoxic N2O decomposition experiment, a positive correlation between δ18O and δ15Nbulk (slope = 2.2) and between SP and 15Nbulk (slope = 0.9) of N2O, which indicates the occurrence of N2O reduction, were found. The N2O reduction rate was increased by the high MLSS concentration. Moreover, isotopic enrichment factors (ε), which are specific to biological reaction, during N2O reduction were estimated as –9.5 ± 1.0‰ for δ15Nbulk, –28.7 ± 3.7‰ for δ18O and –10.0 ± 2.2‰ for SP of N2O.
By using a permanent network of multi-component gas analyzer systems (Multi-GAS), we report for the first time the H2O-CO2-SO2 composition of the volcanic gases emitted prior to, during, and after terminal Strombolian activity at Mount Etna’s central craters (CCs). We show that the summer 2012 Strombolian episodes of the Bocca Nuova crater (BNC), the largest of Etna’s CCs, are associated with the emission of the most CO2-rich gas measured at the volcano thus far. The BNC plume was particularly CO2-rich with CO2/SO2 up to 100, H2O/CO2 < 1 in the quiescent periods between Strombolian episodes. However, more CO2-poor gas with CO2/SO2 < 27, H2O/CO2 > 1 prevailed at the BNC and at other degassing vents such as Voragine and Northeast craters during Strombolian eruptions. Based on the results of numerical simulations of volcanic degassing, conclude that the shallow Etna plumbing system was invaded in summer 2012 by a CO2-rich gas front likely supplied by the deep (>100 MPa pressure) volcano’s magmatic storage zone. This deep gas-bubble supply eventually caused a general rejuvenation of the resident magma in the upper conduits/shallow reservoirs, thereby triggering the first Strombolian episodes on the volcano’s summit after years of quiescence.
The recently discovered world-class Shimensi tungsten-polymetallic deposit, located in the Middle-Lower Yangtze River metallogenic belt, has an estimated reserve of 742,500 tons of WO3 with 0.195% W, which is accompanied by 403,600 tons of Cu and 28,000 tons of Mo. The ore geology, ore mineralogy, structure/texture, alteration, and mineral zoning of the Shimensi deposit are discussed in the paper. Three styles of mineralization are present in the deposit: veinlet-disseminated, quartz vein, and hydrothermal crypto-explosive breccia. The associated hydrothermal alteration includes mainly K-feldsparization, greisenization, chloritization, silicification, and carbonatization. Seven samples of molybdenite from the three ore styles have Re-Os model ages ranging from 145.6 Ma to 139.7 Ma, with an isochron age of 140.6 ± 1.2 Ma and mean square weighted deviation (MSWD) of 1.5. The rhenium content in the molybdenite in the Shimensi deposit varies from 0.8641 × 10–6 to 22.600 × 10–6, mostly in n × 10–6, which indicates that ore-forming elements conform to the characteristics of the tungsten deposit accompanied by Cu and Mo and also implies that the ore-forming materials originate mostly from the crust, with some input from a mantle source. The calculated O isotope and measured H isotope compositions of the quartz veins indicate that the ore-forming fluids had a partially magmatic-hydrothermal origin but were mixed with meteoric water. The geochronology and isotopic chemistry indicate that the Shimensi deposit is related to the Early Cretaceous magmatism that occurred throughout eastern China. The partial melting of the Neoproterozoic Shuangqiaoshan Group, with high-W-background concentrations, and the high degree of fractional crystallization of volatile-rich magma are significant factors in the genesis of the Shimensi tungsten-polymetallic deposit.
Biodegradation is well known as the most effective and important process in monitored natural attenuation (MNA). Previous studies at a crude oil spill site in Northeast China have documented the progress of oil biodegradation by analyzing geochemical indicators. However, without evidence about the behavior of methane (CH4), methanogenesis was only speculated to be occurring at the source area of the site. In this study, CH4 content, radiocarbon, and stable carbon isotopes of CH4 were analyzed to confirm the occurrence of methanogenesis during the biodegradation of petroleum hydrocarbons (PHCs) and to infer the fate of CH4. The results show that CH4 concentrations were higher in the pollution source than in the intermediate zone and in the fringes of the pollution plume, and they decreased gradually along the groundwater flow path. The 13C of CH4 and CO2 in the groundwater were in the ranges of the groundwater in other sites. However, in the pollution plume, the 13C of CH4 was more depleted than those in other places and the δ13C of CH4 was increasing in the groundwater flow direction. Confirmed by the presence of δ13C of dissolved inorganic carbon (DIC) and 13C Rayleigh fractionation modeling during CH4 reactions, we found that the PHC methanogenesis mainly occurred in the pollution source, while methane oxidation occurred along the downgradient of the plume. Percentage of modern carbon (pMC) data confirms that approximately 29% of the CO2 found in pollution source groundwater is derived from petroleum sources.
Molecular compositions, isotopes and biomarkers were analyzed to evaluate organic matter source and generation of crude oils in the Xihu Depression. This study also focused on identifying coal and mudstone contribution to crude oil by using effective geochemical parameters. Compared to oil from mudstone, oil from coal appeared to have obviously heavier carbon isotopic values, higher concentrations of diterpenoids and phenanthrenes, and to exhibit C29 sterane predominance over C27 and C28 steranes. These factors imply input of organic matter by terrestrial higher plants. Selected samples from the Pinghu slope belt (PHSB) and Huangyan tectonic belt (HYTB) exhibited geochemical characteristics typical of a terrestrial oxidizing depositional environment, including high concentrations of diterpenoids, which implies pronounced evidence of higher plant input to source facies. Despite the similarities between northern and southern Pinghu oil samples, biomarker parameters indicate greater levels of higher plant input to northern Pinghu oils than to southern Huangyan oils. The mudstone and coal contributions for hydrocarbons vary by facies and by generation-dependent parameters such as carbon isotope values, relative sterane concentrations, and gammacerane index values. Isotope and biomarker results show the genetic correlations and differences between the Pinghu and Huangyan oils in the Xihu Depression. The oils in the Pinghu and Huangyan fields likely originated from coals and mudstones, respectively.
New major, minor, and trace element (Mg, Al, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, and Ir) abundances for a chromitite reference sample, GPt-5, were obtained using instrumental neutron activation analysis (INAA), and are presented in this report. Replicate analyses of GPt-5 with sample masses ranging from 22 to 64 mg showed a precision of less than 8% (1 s) for most elements, except for Ca and Ir, implying that a small amount of the GPt-5 sample (22 to 64 mg) is enough to obtain representative elemental abundances with the exception of these two elements. The large variation (44.5% for 1 s) observed in the abundance of Ir was attributed to sample heterogeneity. By using isotope dilution inductively-coupled plasma mass spectrometry (ICP-MS) coupled with NiS fire-assay pre-concentration, the concentrations of the platinum group elements (PGE; Ru, Rh, Pd, Os, Ir, and Pt) were determined for the sample powders previously used for the INAA to avoid the sampling bias in assessing the effectiveness of the NiS fire-assay digestion. It was possible to determine the abundance of Ir using both the INAA and ICP-MS, and the values obtained were consistent with each other within the measurement precision. This approach confirmed that the NiS fire-assay procedure applied in this study can digest chromite and that the accurate determination of PGE for chromite-containing rocks can be performed by using our analytical method. Based on the Ru/Rh ratio, the GPt-5 chromitite reference sample was classified as a podiform chromitite.
Coastal wetlands are important carbon pools around the world, and soil respiration is a key process that releases carbon into the atmosphere. In this study, the soil respiration rates of different wetland vegetation zones (Phragmites australis, Spartina alterniflora, Scirpus mariqueter, and a bare mudflat) were investigated in Hangzhou Bay over 12 consecutive months. The wetland soil respiration rate was high in the daytime and low in the nighttime in summer, similar to the diurnal dynamics of soil temperature, and formed an obvious unimodal curve. The seasonal dynamics of soil respiration also formed a unimodal curve: summer > autumn > spring > winter; the soil respiration rates of the vegetation zones were in the rank of P. australis > S. alterniflora > S. mariqueter > bare mudflat, under all diurnal and seasonal conditions. The soil respiration rate had no significant correlation with soil water content but did have a significant exponential correlation with air and soil temperatures. The correlation between the soil temperature and respiration rate in P. australis, S. alterniflora, and bare mudflat was greater than that between the air temperature and respiration rate, while thatin S. mariqueter was quite different. Calculations showed that the Q10 value, a temperature-sensitive coefficient of soil respiration, was 2.59 ± 0.58 in the study area, and was greater in bare mudflat than in soil with vegetation. Soil CO2 emissions in P. australis, S. alterniflora, S. mariqueter, and bare mudflat were 6483.40, 5228.96, 2295.48, and 975.48 gm–2 yr–1 respectively.
A geochemical study of the Late Cambrian-Early Ordovician sandstones exposed in the West Coast Range, Tasmania, Australia, was carried out to develop an understanding of the provenance and tectonic settings. The average composition of these sandstones displayed high SiO2 (92.72%), moderate Al2O3 (3.34%) and Fe2O3 (1.71%), low K2O (0.90%) and MgO (0.15%), and very low CaO and Na2O (<0.01%) concentrations. The sandstones were mainly classified as quartzarenite, and some samples were classified as sublitharenite. Tectonic discrimination diagrams based on major and trace elements suggest passive margin settings. Provenance diagram (Al2O3 vs. TiO2) revealed that the Owen Group was derived from a silica-rich source. The average chemical index of alteration (CIA) was 78.45, indicating that the source area suffered severe weathering due to persistent warm and humid climate. High amounts of rare earth elements (REE) and strong negative anomalies on the chondrite-normalized REE pattern indicate an oxidizing deposition environment. The trace element chemostratigraphy reflects sharp contrasts in concentrations, distinguishing the unconformity between the lower and upper sequences and also shows the effect of alteration assemblages.
Stable oxygen isotopic analysis was performed on the UT-A stalagmite with annual microbanding from the Uchimagi-do Cave in Iwate Prefecture on the Pacific side of Northeast Japan. High-resolution analysis of the uppermost portion of UT-A revealed a positive correlation between the stalagmite δ18O value and R ((summer precipitation–winter precipitation)/annual precipitation) over the last several decades. This correlation is the result of the distinct seasonal shift in precipitation δ18O. During the summer, rainfall with higher δ18O values arrives from the humid atmosphere over the Pacific Ocean. In the winter, comparatively little snowfall/rainfall, with lower δ18O values, arrives from the Japan Sea and is brought by Nangan cyclones (low-pressure systems that pass along the southern coast of Japan). In years with humid summers, large amounts of rainfall from the Pacific Ocean raise the δ18O values of the cave dripwater and stalagmites. Changes in precipitation over the last 1,100 years, reconstructed from the δ18O profile of the UT-A stalagmite, coincide with the historical records of famines and disasters triggered by rainfall excesses and shortages.
April 26, 2016 Due to the maintenance of online payment system, article purchase with credit card will be unavailable as following schedule. If you may encounter the maintenance difficulties, please try again after the maintenance is completed. Thanks for your kind cooperation. Details
May 01, 2015 Please note the "spoofing mail" that pretends to be J-STAGE.