Water-rock interaction processes and trace elements distribution were studied in the Triassic dolomite aquifers of Sassolungo and Sella group (Dolomite mountains, northern Italy). These systems consist of almost pure dolomite and constitute an extremely favourable situation to study water-rock interactions and trace elements mobility in aquifers hosted by dolomite rocks. The chemical and isotopic composition of 26 springs was analysed together with mineralogical and geochemical data of the host rocks from the Sciliar Dolomite Fm. (Sassolungo) and the Dolomia Principale Fm. (Sella Group). Rock samples were found to be formed by almost ordered and stoichiometric dolomite (dolomite wt.% > 93) and minor phases, such as calcite, Mg-calcite and, to a smaller extent, albite and gypsum. The sampled waters are characterised by a Ca-Mg bicarbonate composition and aqueous speciation calculations, coupled with the analyses of isotopic data, reveal that congruent dissolution of dolomite is the main process governing the composition of groundwater. For most of the samples, dolomite dissolution occurs in an open system with PCO₂ between 10^-2 and 10^-3 bar. The study of trace elements distribution shows that during dolomite dissolution alkaline metals, alkaline earth elements larger than Ca and some transition metals are relatively enriched in the solutions while the solutions result to be depleted in Fe, Al, Y and REE.

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Chemical and physical properties of humic acids (HAs) isolated from Mudbanks (locally known as "Chakara"—a unique phenomenon occurring along the south west coast of India during the southwest monsoon season) sediments were characterized by using CHNS, UV-Vis, Fluorescence, FTIR, ¹H NMR, solid state CP/MAS ¹³C NMR, MALDI-TOF-MS and HRTEM. Elemental analysis by CHNS revealed the presence of excess organic sulfur content which indicates the prevailing of sulphate-reducing conditions during the active phase of mudbanks. The HAs origin under the influence of terrestrial environments which contributes more aliphatic fragments is substantially supported by lower N/C ratio and higher E4/E6 ratio (i.e., a rapid decrease in absorptivity with an increase in wavelength). Intense short wavelength maxima in fluorescence emission spectra characterises the presence of terrestrially derived lignin-like moieties. FTIR indicates the presence of hydroxyl, methyl, methylene, carbonyl, carboxyl, phenol, and alcohol and amide groups, probably sulfur groups also. The ¹H NMR spectra shows that in mudbank HAs, the relative content of aliphatic, lignin-like and methoxyl protons is typically greater than the content of aromatic protons. Alkyl carbon components (such as methyl, methylene and methine carbons) in ¹³C NMR spectra constitute the highest structural moiety, and the percentage of carbon signaling carboxyl, amide, ester, ketone, and aldehyde groups is significantly higher than the O-substituted alkyl or substituted aromatic carbon entities. The resonance of unsubstituted aromatic structures shows a higher proportion of the structural components. Mass fragmentation pattern in MALDI-TOF-MS revealed the presence of lignin moieties with β-O-4 in the HAs. These spectral informations further correlated to the quasi-spherical assembling of HAs revealed from HRTEM images. Structural features of HAs isolated from the sediments of mudbanks are significantly marked with lignin and/or lignin-like moieties which are characteristic of the terrestrially derived organic debris, and thus it endorses various postulates for the formation of mudbanks along the Kerala coast during southwest monsoon season, based on the flow of water and mud from the inland rivers and backwaters through the "subterranean channels" into the coastal sea.

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Extensive coals and coaly shales were deposited at the western margin of the Central Myanmar Basin (CMB) during the Late Eocene. Carbon, nitrogen and sulfur (CNS) elemental analyses, vitrinite reflectance, Rock-Eval pyrolysis, biomarker analyses and δ¹³C measurements were made of eight coal and coaly shale samples from the Pondaung and Yaw Formations. Moderate weathering was recognized in three coaly shales, as manifest by microscopic cracks, holes, and rim structures in vitrinite. A sample pair of fresh and weathered coaly shale collected from the same seam showed that HI, Pr/Ph ratio, and concentration of PAHs and long chain n-alkanes (>n-C₂₀) bonded to kerogen in the coaly shales decreased drastically due to weathering, while OI increased. These results suggest that hydrocarbon generation potential of the coaly shale as an oil/gas source rock decreased to about one tenth by the weathering, whereas the free n-alkanes, biomarkers such as steranes and triterpanes, and δ¹³C ratios of kerogen were not affected. Facies change from the coaly shale layers (Phase-I) to the coal layers (Phase-II) was accompanied by variations in origin of the organic matter. The source of the organic matter was mainly terrestrial herbaceous vegetation and/or aquatic plants, deposited in oxic to oxygen-poor peat swamps associated with an estuarine/fluvial-deltaic setting. Phase-I is relatively rich in gymnosperm biomarkers such as retene and 1,7-dimethylphenanthrene (DMP), whereas Phase-II shows an increase in angiosperm proxies such as oleanane content and oleanane/C₃₀ hopane ratio, with δ¹³C values ranging from -24.6‰ to -26.5‰. Based on HI values of unweathered samples, Phase-I is characterized by type II-III kerogen, while Phase-II contains type III kerogen. Higher values of HI, Pr/Ph ratios, n-C₂₉/n-C₁₉ alkane ratios (>1.5), and higher concentrations of conifer-derived 1,7-DMP in Phase-I suggest a significant contribution from material of resinous vascular plant origin. High Fluoranthene/(Fluoranthene+Pyrene) ratio in the uppermost coal suggests occurrence of wildfire, probably related to a dry climate experienced in Phase-II. Unweathered CMB samples show good source rock quality, with potential generation of liquid/gas hydrocarbons.

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Dissolved organic carbon (DOC) can be considered fine indicators of soil quality that influence soil function in specific ways and are very sensitive to changes in soil management practices. In this study, the contents and isotopic compositions of dissolved organic carbon (δ¹³C_DOC) in soils were analyzed at different topographic positions on two typical slopes in a karst area to evaluate the source and fate of DOC in the soil from these regions. The results show that DOC contents of the two slopes were mainly affected by soil organic matter (SOM) input, topography, and soil quality. DOC contents at each topographic location on the two slopes decrease with increasing soil depth. The δ¹³C_DOC of the shrubby slope surface soils varied from -15.1‰ to -22.1‰, and are consistent with SOM δ¹³C and local vegetation. The δ¹³C_DOC of the grassy slope surface soils ranged from -20.0‰ to -20.9‰, similar to isotopic compositions of soil organic carbon (δ¹³C_SOC), but are inconsistent with present-day vegetation. The δ¹³C_DOC varied significantly with depth at each topographic location. Thus, the dependence of δ¹³C_DOC in soil profiles on depth reflects the migration and transformation of DOC in soils.

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Two piston cores (06GHSA P1 and 06GHSA P6) taken from the Ulleung Basin of the Japan Sea/East Sea were examined for the presence of an organic compound, diploptene (hopanoid 17α(H),21β(H)-hop-22(29)-ene). Carbon isotopes of diploptene (δ¹³C_dip) were analyzed to determine their origins and relationship with methane hydrate dissociation. The presence of diploptene was identified, and its concentrations in the two cores exhibited spatiotemporal variations, ranging from 1.7 to 632.1 ng/g (average, 87 ng/g) in core 06GHSA P6 and from 1.4 to 42.2 ng/g in core 06GHSA P1 (average, 20.1 ng/g). In both cores, δ¹³C_dip exhibited significant variations, ranging from -22.3 to -61.3‰. In core 06GHSA P6, extreme δ¹³C_dip depletion was evident in the sediments deposited under glacial conditions, whereas relatively enriched values were determined in Holocene sediments. High diploptene concentrations correspond to depleted δ¹³C_dip, indicating that carbon was, in part, derived from methanotrophic bacterial activities, whereas low diploptene concentrations may reflect a mainly cyanobacterial origin. The presence of depleted δ¹³C_dip and its fluctuation may record the dissociation of gas hydrates and methane seepage during glacial intervals for core 06GHSA P6. The release of methane hydrate release may have been triggered by the collapse of the stability zone. Several factors associated with the hydrate stability include sea-level fluctuations. Lowered sea levels during glacial periods may cause the collapse of hydrate stability zone, which could be the source of dissociated of methane hydrate and methane seepage. This study documents the evidence of methane hydrate instability, inferred from compound-specific analysis, of the Japan Sea/East Sea sediments.

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We studied the alpha-cellulose extraction procedure used for the tropical tree sungkai (Peronema canescens Jack) using an improved Teflon extraction vessel to achieve reliable oxygen isotopic analysis for paleoclimate reconstruction in tropical Asia. We assessed the change in the attenuated total reflection infrared (ATR-IR) spectra and oxygen isotopic ratios during the extraction. Results suggest that the optimum extraction time durations using thin sungkai samples (≤15 mg, 20-μm thickness shaved wood samples) are (i) 30 min for resin removal from tree contents in an organic solvent extraction, (ii) 6 h (1 h × six times) for delignification in a bleaching reaction, and (iii) 2 h 15 min (45 min × three times) for lignin and hemicellulose removal in an alkali reaction. Moreover, our result suggests the necessity of removing impurities such as lignin completely because the oxygen isotopic ratio of lignin in this sample was found to be significantly lower than that of alpha-cellulose.

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We report high-resolution in situ Pb isotope analysis (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios) by femtosecond laser ablation-multiple ion counter-inductively coupled plasma-mass spectrometry (fsLA-MIC-ICP-MS) for low-Pb geological reference glasses. Pb isotope analysis was realized using a multiple ion counter (MIC) and a modified inductively coupled plasma (ICP) ion interface to improve the signal-to-noise ratio and instrumental sensitivity, respectively. Use of femtosecond deep-UV (200 nm) laser ablation enhanced the sampling efficiency of the small amount of glass. Pb memory from sample-skimmer cones were subtracted using an on-peak background method. Instrumental mass bias correction and inter-MIC calibration were performed simultaneously using a standard-sample bracketing method. The optimized analytical protocol was applied to various rock reference glasses (BHVO-2G, BCR-2G and GSD-1G from the United States Geological Survey, and the MPI-DING series glasses: KL2-G, StHs6/80-G, ATHO-G, T1-G, and GOR132-G from the Max Plank Institute for Chemistry, Germany) with spatial resolution of ∼30-μm diameter and 3-25-μm depth. The accuracy achieved was better than 0.38% compared with reference values, and the reproducibility was better than 1.0% (2SD) for both ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios from the glasses with Pb concentrations of 1.7-19 ppm. We found that proper control of signal intensity is crucial for accurate and precise isotopic ratio measurements by the miniature MIC. Signal intensity higher than 300 kcps results in instantaneous saturation of the MIC and consequent inaccurate isotopic ratio measurements. The optimization of the fsLA-MIC-ICP-MS system allows high-throughput Pb isotopic microanalysis with the precision, accuracy and lateral spatial resolution comparable to those of secondary ion mass spectrometry, indicating the versatility of this method for in-situ microanalysis of Pb isotopes in the geosciences.

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Molecular distribution and compound-specific hydrogen isotopic ratios (δD) of n-alkanes in shallow-water surface sediments from the Chaka salt lake and from various terrestrial plants in the surrounding area were measured to obtain a better understanding of the relationship between sedimentary n-alkanes in salt lakes and their biological sources. The n-alkanes in the terrestrial plants exhibited a modal distribution, maximizing at n-C₂₅ or n-C₂₇ with average chain length (ACL) values ranging from 26.6 to 27.7. The ACL values of the sediments were similar to those of terrestrial herbaceous plants from the study area. The average n-alkane δD value (-81.7‰) for the woody-plant leaves was higher than that for terrestrial herbaceous plants (-164.3‰). The average δD values of n-alkanes in the sediments ranged from -163.8‰ to -127.7‰, which fall between the δD values in herbaceous and woody plants, but closer to those in terrestrial herbaceous plants from the study area. This similarity of the n-alkane distributions, and δD values of sediments and plants suggests that n-alkanes in the sediments are likely to be derived mainly from terrestrial herbaceous and partly from woody plants.

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The significant enrichment of chemical composition associated with enhanced bioactivities and an increased number of bio-particles in the sea-surface microlayer (SML) were observed in the high-nutrient, low-chlorophyll (HNLC) eastern equatorial Pacific Ocean (0°N, 95.5°W) during the EqPOS cruise in 2012. The particulate phosphorus and iron were enriched by factors of 72 and 11, respectively, in the SML samples in comparison with subsurface water (SSW) samples. Individual particle chemical analysis by SEM/EDX also showed higher phosphorus levels in most of the analyzed SML particles than in the SSW particles. These observations demonstrated a distinct biogeochemical enhancement in the SML in response to an external perturbation, most likely iron depositions into the HNLC ocean SML.

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