Stable carbon isotope ratios (δ¹³C) in tree rings have been increasingly used as indicators of climatic and ecological processes. However, compared to inter-annual δ¹³C variability, the factors related to inter-tree and -site variability (i.e., dendroclimatic noise) have attracted less attention. Here we present a statistical study quantifying the inter-tree and -site variability in a tree-ring δ¹³C dataset in the context of biogeographical, climatic, and forestry variables. This dataset originates from sixty-seven Scots pine (Pinus sylvestris L.) trees growing in seven sites in the north boreal forests and near the subarctic timberline in Finnish Lapland. Using estimates from a linear mixed model, we identified a set of three constraints, possibly behind the inter-tree and -site δ¹³C variations. First, a latitudinal constraint was found with more negative δ¹³C values in colder (timberline) conditions, in comparison to trees in south of timberline. Second, a longitudinal constraint appeared to result in more negative δ¹³C levels in the eastern sites. Third, an altitudinal constraint led to less negative δ¹³C levels at higher altitudes. Additional source of inter-tree and -site δ¹³C variations attributable to tree size variables resulted in less negative δ¹³C values in taller trees with larger crowns. As the tree size and age are closely connected in our data, these results supported earlier findings that Pinus δ¹³C data may exhibit age-related changes. These results were consistent with mechanistic links between environmental drivers and carbon isotope fractionation. The extent of inter-tree and -site variability affected the length of confidence intervals around the mean δ¹³C value. The use of statistical power analyses was highlighted for assessing the required sample size to estimate the mean value.

In this study, a combined methods of geochemistry, petrology and mineralogy are used to analyze the Lower Carboniferous clastic rocks from the northeastern Junggar, China, and then the weathering intensity, recycling, provenance and tectonic setting are discussed. The chemical index of alteration (CIA) values and the A-CN-K diagram show that the detritus of the mudrocks experienced a weak to moderate weathering intensity. The low Th/U and Zr/Sc ratios show that the mudrocks experienced a minimal recycling process. The low compositional and textural maturities of the interlayer sandstone reflect a proximal provenance. The low contents of Cr and Ni of the samples exclude the southern adjacent Armantai ophiolites as the potential provenance. Therefore, the nearby northern Dulate arc was the likely source area for the mudrocks. The XRD analysis reveals that the mudrocks contain abundant of quartz, plagioclase (albite) and clay minerals, and some calcite and apatite. The samples have high contents of P₂O₅, meanwhile, show statistically significant positive correlation between P₂O₅ and CaO, Y, Sr, and light rare earth elements, also indicating abundant phosphates minerals (e.g., apatite) in the mudrocks. The discriminate plots of the geochemistry (major, trace and rare earth elements) suggest that the source rock compositions are mainly felsic rocks and mixed with a few basic rocks. The tectonic discrimination diagrams of major and trace elements indicate that the mudrocks were originated from oceanic island arcs, which formed in an extensional tectonic environment. Combined with previous studies, the geochemistry data imply there are two evolution stages occurred in the northern Junggar area during the early late Paleozoic time. The northern Junggar was amalgamated to the southern margin of the Chinese Altai before Devonian, and then experienced extensional movements during the early Devonian to early Carboniferous periods. The Dulate arc and arc-related basins in this area were formed during this extensional course.

The shallow-seafloor Wakamiko hydrothermal field in Kagoshima Bay, Japan, has been characterized by high ammonium contents (~17 mM) in the discharge fluid. The sediment layer covering the field also contained a high concentration of ammonium in the pore fluids. The fluid chemistry suggests that the high concentration was attributed to whether mixing with hydrothermal fluid or the mineralization of organic matter. The occurrence of sediments such as smectite, illite and mica has been reported, and is associated with hydrothermal activity. Those 2:1 clay minerals can fold ammonium as mineral nitrogen (MN) in their interlayers. Extracted clay fractions from the sediment core samples obtained from the field were mainly composed of smectite. It contained a small amount of MN and its δ¹⁵N values reflected that of pore fluid ammonium in the case of a high ammonium (>4 mM) environment. On the other hand, δ¹⁵N values of MN in the low ammonium (≤4 mM) environment were similar to those of the associated adsorbed organic nitrogen. The high ammonium environment associated with hydrothermal activity is expected to enhance formation of ammonium-bearing clay minerals, and then the δ¹⁵N value of MN fixed in the clay minerals is possibly preserved a signal of pore fluid ammonium.

With the aim of improving understanding of aromatic hydrocarbon formation by transformation of alkanes during maturation, the C₂₃, C₂₈, C₂₉, C₃₁ and C₃₆ n-alkanes and pristane were separately heated at 350–500°C in a closed system for 72 h to determine the aromatic hydrocarbon species and their characteristics formed by pyrolysis. Analysis of the obtained pyrolysates using gas chromatography-mass spectrometry showed that pyrolysis of different alkanes formed similar aromatic hydrocarbons with increasing maturity, regardless of whether they were straight chain or isoprenoid. Monoaromatic compounds were preferentially formed first, followed by various dicyclic and polycyclic aromatics. Many common aromatic hydrocarbons were detected in the pyrolysates, and their distribution suggests that alkanes are an important aromatic hydrocarbon source in petroleum formed by high maturity. Some aromatic hydrocarbons that are known to originate from biological precursors could also be formed by pyrolysis, so more attention to sample maturity is required when such compounds are used as source indicators. With increasing temperature, the aromatic hydrocarbons mainly underwent polymerization and desubstitution reactions, resulting in an elevated amount of polyaromatics and fewer substituted aromatic compounds.

A method is presented for the routine analysis of eight trace metals (As, Cd, Co, Cr, Cu, Ni, Pb, V) in wood samples of 100–200 mg. The organic matrix is broken down by microwave digestion and the resulting solutions are analyzed by ICP-MS, after appropriate dilution, against an external multi-element calibration line. Detection limits are ~200 ng metal per g of dry wood for Cr and Cu, and as low as 10–60 ng g^–1 for the other six metals. Frequent analysis of the Certified Reference Material NJV 94-5 (Wood Fuel) and a series of spike recovery experiments gave chemical yields ranging from 90% for Cr to 103% for V, but only 80% for As. Precision is generally 2–7%, yet better for Cd and Cu (~1%) and somewhat worse for As (~20%). This new method is suitable for the analysis of tree increment cores cut into sections representing 1–5 years of growth and can be readily modified to include additional metals. As a practical application, increment cores of eastern cottonwood (Populus deltoides) from Ohio (USA) were analyzed for the period 1970–2009. Pairwise comparisons of cores taken from the same tree, or from adjacent trees at the same location, illustrate some acknowledged limitations of their use as a temporal record of trace metal loading in soils.

The spatial distribution of radon in soil and ground water is investigated in the proximity of Khairi Murat (KM) fault, Northern Pakistan. The present work is aimed to delineate the concealed segment of KM fault by analyzing the spatial distribution of radon in soil and ground water. Soil radon concentration is measured for 90 sampling points along 15 transverse profiles in the proximity of KM fault zone. A consistent trend of soil radon level for exposed and concealed segment of KM fault manifests the existence of subsurface fault structure. The anomalous radon level (2.40–3.35 kBq/m³) corresponds to sampling points adjacent to fault zone. Conversely, insignificant radon level (1.57–2.35 kBq/m³) corresponds to the distant sampling points from fault zone. Such heterogeneity of soil-radon level along transverse profiles reveals an evident correlation with seismogenic feature. In addition to that, ground water radon level, along (29.41 ± 5.2 Bq/L) and across (12.33 ± 3.2 Bq/L) the KM fault show a congruence with soil radon observations. Inclusively, our results suggest that spatial distribution of soil radon can serve as a useful tool for identification of concealed seismogenic features.

Deep-sea mud extremely enriched in rare-earth elements and yttrium (together called REY) has been discovered around Minamitorishima Island, in the western North Pacific. The REY-rich mud was previously observed to contain abundant phillipsite and biogenic calcium phosphate. We analyzed the chemical compositions of porewater in a sediment core containing REY-rich mud and observed a decrease of dissolved phosphate (PO₄^3–) from ~1 μM to ~0.5 μM around the REY-rich mud layer. The presence of dissolved nitrate + nitrite throughout the cored depth indicated oxic sediment conditions. In the REY-rich mud, PO₄^3– was presumed to be adsorbed onto the surfaces of minerals such as phillipsite. Our results support that oxic pelagic clay containing phillipsite can be a sink for PO₄^3–. Concentrations of REY in porewater were below the detection limit.

The CO₂ densimetry based on CO₂ Fermi diad (delta, cm^–1) is a powerful method for estimating the depth of a rock’s origin. To enhance the accuracy of delta, we investigated both room and sample temperature dependency under laboratory conditions. We examined sample temperature dependence of delta while raising sample temperature using a heating-cooling stage at a constant room temperature. The results showed no sample temperature effect at least at temperatures of 21–26°C. Similarly, in order to evaluate room temperature effect, we measured delta while raising room temperature by an air conditioner at constant sample temperature. Independent fluctuation of room and sample temperatures showed that changes in room temperature and the Raman system, not the influence of sample temperature, affect delta. In order to enhance the accuracy, we suggested a new correction formula for CO₂ Fermi diad, which functions to correct for the influence of the temperature effects.

Source and formation of high-molecular-weight dissolved organic matter (HMW-DOM) and its interaction with other organic components such as particulate organic matter (POM) and low-molecular-weight DOM (LMW-DOM) have been poorly understood so far. Molecular and isotopic compositions of HMW-DOM are generally far different from those of POM and LMW-DOM. In this study, we further investigate large proportions of 24-ethylcholesta-5,22-dien-3β-ol (stigmasterol) in the HMW-DOM (but not in POM and LMW-DOM) during summer in three types of lakes: freshwater Lakes Kizaki and Suwa and a brackish-water Lake Suigetsu, in Japan. Moreover, from the carbon and hydrogen isotope analysis, we reveal autochthonous algae (perhaps some minor, specific phytoplankton) as a major source of the abundant stigmasterol in the lakes. These results suggest that HMW-DOM in summer is derived from autochthonous phytoplankton rather than allochthonous terrestrial plants and that HMW-DOM likely has few interaction (e.g., exchange of components) with POM and DOM in the lakes.