On the origin of saline fluids in the KTB (Continental Deep Drilling Project of Germany)

Highly saline fluids were encountered during the German Continental Deep Drilling Project (KTB) from depths ranging between 2 and 3 km to about 9 km. The most reliable data were obtained from samples extracted during a long-term pumping test in the 4000-m deep KTB pilot hole. Some 460 m³ Ca–Na–Cl brines with about 68 g l⁻¹ total dissolved solids (TDS) and some 270 m³ associated gases, mainly N₂ and CH₄ were pumped to the surface from the main fracture system situated near the bottom of the pilot hole. Geochemical and isotopic data support the hydraulic tests which suggest the presence of an open and large fluid reservoir at depth. The pumped fluids from this main fracture system were released from a deep reservoir situated at more than 5500 m depth which is hydraulically connected with the 9101 m deep KTB main hole, drilled some 250 m to the northeast of the pilot hole.While Ca and Sr contents of the extracted brines may be the result of water–rock interaction, Cl is most likely of external origin. The Cl is hypothesized to derive from geotectonic processes rather than to descending infiltration of paleo-seawater (evaporitic brines). The sampled fluids have probably migrated from a deeper reservoir to their present position since the Cretaceous–Tertiary period due to tectonic activity. However, several isotopic studies have identified an admixture of descending paleowaters down to more than 4000 m depth. The high ³⁶Cl/Cl ratio of the fluids sampled during the long-term pumping test point to a host rock highly enriched in U–Th, unlike the sampled KTB country rocks. The fluid reservoir is believed to be in contact with the Falkenberg granite massif situated about 2 km to the E of the KTB holes, capable of supplying sufficient neutron flux for considerable subsurface production of ³⁶Cl. The Na–Cl–(K-, SO₄) precursor fluids of the Ca–Na–Cl brines were produced in the course of extensive tectonic processes since the Late Caledonian within the Bohemian Massif.     

The Diavik waste rock project: Water flow through mine waste rock in a permafrost terrain

A field experiment is being carried out at the Diavik diamond mine in northern Canada to investigate the influence of unsaturated flow behavior on the quality of drainage from mine waste rock piles in a region of continuous permafrost. This paper is part of a series describing processes affecting the weathering of waste rock and transport of reaction products at this site; here the focus is on unsaturated water flow and its role in mass loading. Two 15 m-high instrumented test piles have been built on 60 m by 50 m collection systems, each consisting of lysimeters and a large impermeable high-density polyethylene (HDPE) liner. Collection lysimeters are installed nearby to investigate infiltration in the upper 2 m of the waste rock. Porosity, water retention curves, and hydraulic conductivity functions are estimated from field measurements and for samples ranging in size from 200 cm³ to 16 m³. Net infiltration in 2007 is estimated to have been 37% of the rainfall for mean annual rainfall conditions. Early-season infiltration freezes and is remobilized as the waste rock thaws. Wetting fronts migrate at rates of 0.2–0.4 m d⁻¹ in response to common rainfall events and up to 5 m d⁻¹ in response to intense rainfall. Pore water and non-reactive solutes travel at rates of <10⁻² to 3 × 10⁻² m d⁻¹ in response to common rainfall events and up to 0.7 m d⁻¹ in response to intense rainfall. Time-varying SO₄ mass loading from the base of the test piles is dictated primarily by the flow behavior, rather than by changes in solute concentrations.     

Scytonemin-imine,a mahogany-colored UV/Vis sunscreen of cyanobacteria exposed to intense solar radiation

We report the structure of a novel sunscreen based on the scytoneman skeleton. This pigment, scytonemin-3a-imine, was isolated from cultures of the cyanobacterium, Scytonema hoffmani, only when grown under high to intense (300–1500+ μmol quanta m⁻² s⁻¹) light conditions, with or without added UVR (ultraviolet radiation). It was also isolated from samples of natural cyanobacterial mats growing in shallow/short hydroperiod fresh water (Florida Everglades), soils (Loxahatchee, Florida) and saline cyanobacterial mats (Eleuthera, The Bahamas). These natural samples were all growing under intense (e.g. > 1500 μmol quanta m⁻² s⁻¹) light conditions. Scytonemin-3a-imine may eventually become a biomarker for such biota.Characterization included UV/Vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, matrix assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry (MS and MSⁿ), and both 1- and 2-D ¹H nuclear magnetic resonance (NMR) spectrometry. Derivatization (NaBH₄ reduction, acetylation, deuterium exchange) were utilized to confirm structural features. The UV/Vis spectrum had maxima at 237, 366, 437 and 564 nm. The absorption of UVR is in line with other scytoneman-based pigments. The strong visible absorption bands (437 and 564 nm) indicate an alternate or additional physiological role for the pigment. We propose that it may protect both the chlorophyll reaction centers and the cytochromes from excess radiation. We speculate that excitation of the cytochromes, potentially leading to excess electron transport, or photo-oxidative destruction of the cytochromes, may enhance reactive oxygen species (ROS) generation.     

Evaluation of environmental fate and sinks of PCDD/Fs during specific extreme weather events in Taiwan

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are persistent organic pollutants (POPs) that are formed and released unintentionally from anthropogenic sources. The high persistence of PCDD/Fs results in the concentrations of these contaminants in environment decreasing only very slowly. Two transport pathways, air and water, carry PCDD/Fs into all regions of the world. Recently, more frequent extreme weather events, such as storms and floods, have been projected to occur as a result of global warming. Extreme weather events have a documented impact on the remobilization and subsequent bioavailability of POPs. In this study, three specific episodes, namely winter monsoon, southeast biomass burning and tropical cyclone (typhoon) events, which influence the environmental fate and transport of PCDD/Fs in Taiwan, were evaluated based on a climate change scenario. During the winter (northeast) monsoon period, the temperature and relative humidity observed in northern Taiwan decreases sharply. During this time, the quantity of PCDD/Fs adsorbed onto suspended particles, as observed at background sites, was found to increase from 300 ± 127 to 630 ± 115 pg I-TEQ g-TSP⁻¹, which is even higher than that measured in Taipei City (438 ± 80 pg I-TEQ g-TSP⁻¹). Hence, the winter monsoon not only brings cold air but also transports air pollutants and dust over long distances from mainland China to Taiwan. During the 2010 Southeast Asia biomass burning events (2010/3/22–3/28), the level of atmospheric PCDD/Fs were measured in central Taiwan (Mt. Lulin) and in the source region of northern Thailand (Chiang Mai); this revealed that the variations in atmospheric PCDD/F concentrations at these two sites followed a similar pattern. On 25 March 2010, the atmospheric PCDD/F concentration increased dramatically from 1.43 to 6.09 fg I-TEQ m⁻³ at Mt. Lulin and from 7.64 to 12.1 fg I-TEQ m⁻³ in northern Thailand. However, the atmospheric PCDD/F concentration decreased dramatically 1 day after the biomass burning event. Based on the measurements from a dated sediment core collected at a reservoir in northern Taiwan, the sharp increases in input fluxes of PCDD/Fs and mineral-derived elements levels in 1990 (20 ng I-TEQ m⁻² year⁻¹), 2001 (17 ng I-TEQ m⁻² year⁻¹), 2004 (16 ng I-TEQ m⁻² year⁻¹) and 2005 (15 ng I-TEQ m⁻² year⁻¹) seem to be a result of a deep turbid layer formed upstream due to landslides and/or mud flows during the typhoon season. This finding demonstrates the effect of typhoon events on the long-term remobilization of PCDD/Fs as well as supporting the hypothesis that such events would have the potential to remobilize pollutants that have been deposited previously.     

Fracture networks and fluid transport in active fault zones

Field measurements were made of 1717 mineral-filled veins in the damage zone of an active dextral strike-slip fault zone in Iceland. Most veins are composed of quartz, chalcedony and zeolites, strike roughly parallel or perpendicular to the fault zone, and are members of dense palaeo-fluid transporting networks. A common vein frequency in these networks is 10 veins per metre. Cross-cutting relationships indicate that 79% of the veins are extension (mode I) cracks and 21% are shear cracks. The apertures of most veins, measured as mineral-fill thicknesses, are from 0.1 to 85 mm, and the aperture frequency distribution is a power law. The outcrop trace lengths of 384 veins (of the 1717) could be measured accurately. These 384 veins are mostly small and range in length from 2.5 to 400 cm, in aperture from 0.01 to 0.9 cm, and have an average length/aperture ratio of about 400. Simple analytical models are derived and used to make rough estimates of the volumetric flow rates in hydrofractures of dimensions equal to those of typical veins. The results indicate that volumetric flow rates for a horizontal fracture and a vertical fracture in a rigid (non-deforming) host rock would be around 1.5×10⁻⁴ and 8.9×10⁻⁴ m³s⁻¹, respectively. The volumetric flow rate in a vertical fracture of equal size but in a deforming host rock, with buoyancy added to the pressure gradient, is around 1.3×10⁻³ m³s⁻¹. Thus, vertical fluid transport is favoured under these conditions.     

Gold mining related mercury contamination in Tongguan,Shaanxi Province,PR China

Elemental Hg–Au amalgamation mining practices are used widely in many developing countries resulting in significant Hg contamination of surrounding ecosystems. The authors examined for the first time Hg contamination in air, water, sediment, soil and crops in the Tongguan Au mining area, China, where elemental Hg has been used to extract Au for many years. Total gaseous Hg (TGM) concentrations in ambient air in the Tongguan area were significantly elevated compared to regional background concentrations. The average TGM concentrations in ambient air in a Au mill reached 18,000 ng m⁻³, which exceeds the maximum allowable occupational standard for TGM of 10,000 ng m⁻³ in China. Both total and methyl-Hg concentrations in stream water, stream sediment, and soil samples collected in the Tongguan area were elevated compared to methyl-Hg reported in artisanal Au mining areas in Suriname and the Amazon River basin. Total Hg concentrations in vegetable and wheat samples ranged from 42 to 640 μg kg⁻¹, all of which significantly exceed the Chinese guidance limit for vegetables (10 μg kg⁻¹) and foodstuffs other than fish (20 μg kg⁻¹). Fortunately, methyl-Hg was not significantly accumulated in the crops sampled in this study, where concentrations varied from 0.2 to 7.7 μg kg⁻¹.     

Dissolution kinetics and biodurability of tremolite particles in mimicked lung fluids: Effect of citrate and oxalate

The effect of citrate and oxalate on tremolite dissolution rate was measured at 37 °C in non-stirred flow-through reactors, using modified Gamble’s solutions at pH 4 (macrophages), 7.4 (interstitial fluids) and 5.5 (intermediate check point) containing 0, 0.15, 1.5 and 15 mmol L⁻¹ of citrate or oxalate. The dissolution rates calculated from Si concentration in the output solutions without organic ligands depend on pH, decreasing when the pH increases from −13.00 (pH 4) to −13.35 (pH 7.4) mol g⁻¹ s⁻¹ and following a proton-promoted mechanism. The presence of both ligands enhances dissolution rates at every pH, increasing this effect when the ligand concentration increases. Citrate produces a stronger effect as a catalyst than oxalate, mainly at more acidic pHs and enhances dissolution rates until 20 times for solutions with 15 mmol L⁻¹ citrate. However, at pH 7.4 the effect is lighter and oxalate solutions (15 mmol L⁻¹) only enhances dissolution rates eight times respect to free organic ligand solutions. Dissolution is promoted by the attack to protons and organic ligands to the tremolite surface. Magnesium speciation in oxalate and citrate solutions shows that Mg citrate complexes are more effective than oxalate ones during the alteration of tremolite in magrophages, but this tendency is the opposite for interstitial fluids, being oxalate magnesium complexes stronger. The biodurability estimations show that the destruction of the fibers is faster in acidic conditions (macrophages) than in the neutral solutions (interstitial fluid). At pH 4, both ligands oxalate and citrate reduce the residence time of the fibers with respect to that calculated in absence of ligands. Nevertheless, at pH 7.4 the presence of ligands does not reduce significantly the lifetime of the fibers.     

Activation energies of the self-diffusion of HTO, 22Na+ and 36Cl− in a highly compacted argillaceous rock (Opalinus Clay)

The temperature dependence of the self-diffusion of HTO, ²²Na⁺ and ³⁶Cl⁻ in Opalinus Clay (OPA) was studied using a through-diffusion technique, in which the temperature was gradually increased in the steady state phase of the diffusion. The measurements were done on samples from two different geological locations. The dependence of the effective diffusion coefficient on temperature was found to be of an Arrhenius type in the temperature range between 0 and 70 °C. A slight difference between the two locations could be observed. The average value of the activation energy of the self-diffusion of HTO in OPA was 21.1 ± 1.6 kJ mol⁻¹, and 21.0 ± 3.5 and 19.4 ± 1.5 kJ mol⁻¹ for ²²Na⁺ and ³⁶Cl⁻, respectively. The measured values for HTO are slightly higher than the values found for the bulk liquid water (HTO: 18.8 ± 0.4 kJ mol⁻¹). This indicates that the structure of the confined water in OPA might be slightly different from that of bulk liquid water. Also for Na⁺ and Cl⁻, slightly higher values than in bulk liquid water (Na⁺: 18.4 kJ mol⁻¹; Cl⁻: 17.4 kJ mol⁻¹) were observed.The Stokes–Einstein relationship, based on the temperature dependency of the viscosity of bulk water, could not be used to describe the temperature dependence of the diffusion of HTO in OPA. This additionally indicates the slightly different structure of the pore water in OPA.     

Chlor-alkali industrial contamination and riverine transport of mercury: Distribution and partitioning of mercury between water,suspended matter,and bottom sediment of the Thur River,France

Total dissolved and total particulate Hg mass balances were estimated during one hydrological period (July 2001–June 2002) in the Thur River basin, which is heavily polluted by chlor-alkali industrial activity. The seasonal variations of the Hg dynamics in the aquatic environment were assessed using total Hg concentrations in bottom sediment and suspended matter, and total and reactive dissolved Hg concentrations in the water. The impact of the chlor-alkali plant (CAP) remains the largest concern for Hg contamination of this river system. Upstream from the CAP, the Hg partitioning between dissolved and particulate phases was principally controlled by the dissolved fraction due to snow melting during spring high flow, while during low flow, Hg was primarily adsorbed onto particulates. Downstream from the CAP, the Hg partitioning is controlled by the concentration of dissolved organic and inorganic ligands and by the total suspended sediment (TSS) concentrations. Nevertheless, the particulate fluxes were five times higher than the dissolved ones. Most of the total annual flux of Hg supplied by the CAP to the river is transported to the outlet of the catchment (total Hg flux: 70 μg m⁻² a⁻¹). Downstream from the CAP, the bottom sediment, mainly composed of coarse sediment (>63 μm) and depleted in organic matter, has a weak capacity to trap Hg in the river channel and the stock of Hg is low (4 mg m⁻²) showing that the residence time of Hg in this river is short.     

The origins of the Mengye potash deposit in the Lanping–Simao Basin,Yunnan Province,Western China

The Lanping–Simao Basin (LSB) is a Mesozoic–Cenozoic continental margin rift basin in Western China. It formed during the opening and closing of the Tethys Ocean. This basin is also known as a “metal belt” as it hosts several metal deposits, besides, the Mengye potash deposit. However, the exact dates of the formation either in the Paleocene or the Cretaceous, and thus the origins of the marine, continental or mixed origins of the Mengye deposits, remain disputed. Based on the basin's evolution, materials of marine origin and/or remnant seawater should be present, but instead the salt layers of the Mengye potash deposit present typically continental lithological features. This study examines and reviews evaporative minerals, Br/Cl and I/Cl molar ratios, and isotopes of S, B, and Sr·I and I/Cl data for this area has not been previously reported. The basin's evaporative minerals are dominated by halite and sylvite. The amounts of anhydrite, chlorocalcite, langbeinite, glaserite, tachyhydrite and glauberite are small. All of these form in both marine and continental environments. The values of I and the I/Cl molar ratios of halite and sylvite are from 0.07 to 0.27 ppm, and from 0.03 to 0.11 × 10^− 6, respectively, dependent on organic substances. Br and molar Br/Cl values are from 89.08 to 555.45 ppm and from 0.06 × 10^− 3 to 0.38 × 10^− 3, respectively. All of the Br/Cl molar ratios are lower than those of seawater, and most of them are < 0.1, suggesting continental or mixed origin. Previously published δ³⁴S, δ¹¹B and ⁸⁷Sr/⁸⁶Sr values for evaporative minerals indicate a continental origin for the Mengye potash deposit. However, materials of hydrothermal origin are widely distributed in the basin and may have played an active role for the formation of the potash deposit. Thus the Mengye potash deposit could be of continental origin, with a remnant seawater trace.     

Pyrite oxidation by Acidithiobacillus ferrooxidans at various concentrations of dissolved oxygen

Pyrite oxidation rates were examined at various concentrations of dissolved oxygen (DO) in the presence of the sulfur and iron oxidizer Acidithiobacillus ferrooxidans. Five different batch experiments were performed at room temperature for 75 days under various DO levels (273, 129, 64.8, 13.2, and ≤ 0.006 μM), containing pyrite grains (particle size 63–250 μm) and a modified 9K nutrient medium at pH 3. The reactors were inoculated with A. ferrooxidans. In all experiments, pH decreased with time and sulfur and iron were released to the solution, indicating pyrite oxidation at all DO levels. Pyrite oxidation rates (ca. 5 × 10^− 10 mol m^− 2 s^− 1 at 273 μM DO) from all experiments showed positive correlation with DO, Fe(III), and bacterial concentration. These rates were significantly slower than rates presented in other published studies, but this is probably due to the significantly greater Fe(III) concentration at lower pH in these previous studies. The results obtained in this study suggest that ferric iron reduction at the pyrite surface is the primarily mechanism for microbial pyrite oxidation in the presence of DO. The results from our study support the indirect mechanism of sulfide oxidation, where A. ferrooxidans oxidizes ferrous iron in the presence of DO, which then oxidizes pyrite.     

Mercury and methylmercury in riparian soil,sediments, mine-waste calcines,and moss from abandoned Hg mines in east Guizhou province,southwestern China

Concentrations of total Hg and methylmercury (MMHg) in riparian soil, mine-waste calcine, sediment, and moss samples collected from abandoned Hg mines in Wanshan district, Guizhou province, China, were measured to show regional dispersion of Hg-contamination. High total Hg and MMHg concentrations obtained in riparian soils from mined areas, ranged from 5.1 to 790 mg kg⁻¹ and 0.13 to 15 ng g⁻¹, respectively. However, total Hg and MMHg concentrations in the soils collected from control sites were significantly lower varying from 0.1 to 1.2 mg kg⁻¹ and 0.10 to 1.6 ng g⁻¹, respectively. Total Hg and MMHg concentrations in sediments varied from 90 to 930 mg kg⁻¹ and 3.0 to 20 ng g⁻¹, respectively. Total Hg concentrations in mine-waste calcines were highly elevated ranging from 5.7 to 4400 mg kg⁻¹, but MMHg concentrations were generally low ranging from 0.17 to 1.1 ng g⁻¹. Similar to the high Hg concentrations in soil and sediments, moss samples collected from rocks ranged from 1.0 to 95 mg kg⁻¹ in total Hg and from 0.21 to 20 ng g⁻¹ in MMHg. Elevated Hg concentrations in mosses suggest that atmospheric deposition might be an important pathway of Hg to the local terrestrial system. Moreover, the spatial distribution patterns of Hg contamination in the local environment suggest derivation from historic Hg mining sites in the Wanshan area.     

Measuring the effective diffusion coefficient of dissolved hydrogen in saturated Boom Clay

Boom Clay is studied as a potential host formation for the disposal of high-and intermediate level long-lived radioactive waste in Belgium. In such a geological repository, generation of gases (mainly H₂ from anaerobic corrosion) will be unavoidable. In order to make a good evaluation of the balance between gas generation vs. gas dissipation for a particular waste form and/or disposal concept, good estimates for gas diffusion coefficients of dissolved gases are essential. In order to obtain an accurate diffusion coefficient for dissolved hydrogen in saturated Boom Clay, diffusion experiments were performed with a recently developed through-diffusion set-up for dissolved gases. Due to microbial activity in the test set-up, conversion of hydrogen into methane was observed within several experiments. A complex sterilisation procedure was therefore developed in order to eliminate microbiological disturbances. Only by a combination of heat sterilisation, gamma irradiation and the use of a microbial inhibitor, reliable, reproducible and accurate H₂(g) diffusion coefficients (measured at 21 °C) for samples oriented parallel (D_eff = 7.25 × 10⁻¹⁰ m²/s and D_eff = 5.51 × 10⁻¹⁰ m²/s) and perpendicular (D_eff = 2.64 × 10⁻¹⁰ m²/s) to the bedding plane were obtained.     

Controls on the sedimentology of an ice-contact jökulhlaup-dominated delta,Kangerlussuaq, west Greenland

This paper characterises the sedimentary impact of a glacial outburst flood or ‘jökulhlaup’ on an ice-contact delta topset at Russell Glacier, Kangerlussuaq, west Greenland. Rapid drainage of an ice-dammed lake in July 1987 generated a jökulhlaup with a peak discharge of ∼ 1300 m³ s^− 1, which drained across a 500-m-wide, 200-m-long, delta top into a proglacial lake. The delta topset comprises boulder clusters, ice block obstacle marks with relief of up to 4 m, and is graded to lake levels up to 6 m higher than those during typical non-jökulhlaup conditions. The delta top was dissected by the 1987 jökulhlaup causing a fan-shaped extension of the delta front by 30 m. Surface grain size on the delta decreases rapidly away from the main flood flow direction, reflecting rapid downstream reduction in sediment transport capacity. The 1987 jökulhlaup was predominantly fluidal and turbulent and had peak stream powers of 2846 W m^− 2 proximally and < 400 W m^− 2 distally. Delta topset sedimentation can be characterised by four lithofacies associations in order of decreasing flow energy: (A) coarse-grained deposits related to a flow expansion; (B) finer-grained peripheral deposits located at the margins of the main flow; (C) lobate bars and delta fronts deposited within distal locations and (D) fine-grained deposits at distance from the delta front associated with slackwater conditions. Jökulhlaup-dominated delta topsets are controlled by the geometry of the channel expansion into the proglacial lake, jökulhlaup hydrograph form, the sediment availability and character, proglacial lake basin depth and surface area, lake outflow spillway erodibility and cross-sectional area, and history of previous jökulhlaups.     

Compositional differences of chromophoric dissolved organic matter derived from phytoplankton and macrophytes

Chromophoric dissolved organic matter (CDOM) is an important component in the aquatic environment and plays a key role in light attenuation and in carbon biogeochemical cycles. We examined CDOM production in each of two laboratory experiments in which phytoplankton and macrophyte degradation were monitored using absorption and excitation–emission matrix fluorescence spectroscopy (EEMs). During the incubation period, CDOM was produced from phytoplankton and macrophytes, and partly decomposed by microorganisms. The absorption spectra of the phytoplankton derived and the macrophyte derived CDOM were distinct and characterized by peaks and shoulders in the UV bands. Production of CDOM absorption at 350 nm, a(350), was 0.0125 m²/g per unit of chlorophyll a from phytoplankton CDOM from 0–3 d. Meanwhile a(350) production was 2.708 × 10⁻⁴ m²/g per unit of wet biomass from macrophytes CDOM from 1–7 d. Despite the high production of CDOM by phytoplankton and macrophytes, extrapolation of these values to the field indicated that about 15% of total CDOM was produced from phytoplankton during algal blooms in Meiliang Bay in summer and about 8% of total CDOM was produced from macrophytes in the macrophyte dominated littorals. The mean value of the spectral slope (S) describing the exponential decrease of the absorption spectrum, which was strongly correlated to an optical index of molecular size, for the phytoplankton derived CDOM was 10.26 ± 2.05 μm⁻¹, which was significantly lower than the mean S of 14.47 ± 2.88 μm⁻¹ for the macrophyte derived CDOM (t-test, p < 0.001). The mean value of the spectral slope ratio (S_R) for the phytoplankton derived CDOM was 1.79 ± 0.52, which was significantly higher than that of 0.35 ± 0.58 for the macrophyte derived CDOM (t-test, p < 0.001). Three fluorescent components were validated in parallel factor analysis (PARAFAC) models calculated separately for phytoplankton derived and macrophyte derived CDOM, each CDOM source resulting in distinct excitation and emission maxima for each component. The significant differences in CDOM absorption spectra, S, S_R and PARAFAC fluorescence component characteristics, all showed that phytoplankton derived CDOM was compositionally distinct from macrophyte derived CDOM. Overall both sources were important to the CDOM pool in the shallow temperate lake.     

Detection of coenzyme F430 in deep sea sediments: A key molecule for biological methanogenesis

We report the presence of coenzyme factor 430 (F430), a prosthetic group of methyl coenzyme M reductase for archaeal methanogenesis, in the deep sub-seafloor biosphere. At 106.7 m depth in sediment collected off Shimokita Peninsula, northwestern Pacific, its concentration was estimated to be at least 40 fmol g sediment⁻¹ (i.e. 36 pg g⁻¹ wet sediment). This is about three orders of magnitude lower than typical concentrations of archaeal intact polar lipids in similar sub-seafloor sediments. On the basis of the concentration of F430 in methanogens and conversion to biomass composed of typical sub-seafloor microbial cells, we estimated that ca. 2 × 10⁶ cells g⁻¹ could be methanogens in the deeply buried marine sediment.     

Assessing soil erosion and control factors by radiometric technique in the source region of the Yellow River,Tibetan Plateau

Measurements of ¹³⁷Cs concentration in soils were made in a representative catchment to quantify erosion rates and identify the main factors involved in the erosion in the source region of the Yellow River in the Tibetan Plateau. In order to estimate erosion rates in terms of the main factors affecting soil loss, samples were collected taking into account the slope and vegetation cover along six selected transects within the Dari County catchment. The reference inventory for the area was established at a stable, well-preserved, site of small thickness (value of 2324 Bq·m^− 2). All the sampling sites had been eroded and ¹³⁷Cs inventories varied widely in the topsoil (14.87–25.56 Bq·kg^− 1). The effective soil loss values were also highly variable (11.03–28.35 t·km^− 1·yr^− 1) in line with the vegetation cover change. The radiometric approach was useful in quantifying soil erosion rates and examining patterns of soil movement.     

Cosmogenic 10Be and 36Cl ages from Late Pleistocene terminal moraine complexes in the Taylor River drainage basin,central Colorado,USA

Cosmogenic surface-exposure ages from boulders on a terminal moraine complex establish the timing of the local last glacial maximum (LGM) in the Taylor River drainage basin, central Colorado. Five zero-erosion ¹⁰Be ages have a mean of 19.5±1.8 ka while that for three ³⁶Cl ages is 20.7±2.3 ka. Corrections for modest rates (∼1 mm ka⁻¹) of boulder surface erosion result in individual and mean ages that are generally within 2% of their zero-erosion values. Both the means and the range in ages of individual boulders are consistent with those reported for late Pleistocene moraines elsewhere in the southern and middle Rocky Mountains, and thus suggest local LGM glacier activity was regionally synchronous. Two anomalously young (?) zero-erosion ¹⁰Be ages (mean 14.4±0.8 ka) from a second terminal moraine are tentatively attributed to the boulders having been melted out during a late phase of ice stagnation.     

Caesium-137 in Southeast Asia: Is there enough left for soil erosion and sediment redistribution studies?

Low reference inventories of the fallout radionuclide ¹³⁷Cs in low latitudes may limit its present and future application for studies of soil erosion and sediment redistribution in Southeast Asia. ¹³⁷Cs reference inventories and concentrations in surface materials measured in nine and five areas, respectively, across Southeast Asia are here reported and reviewed. The compiled reference inventories decrease from north to south. Three global estimates of ¹³⁷Cs total fallout are also reviewed and compared to the measured data while taking into account factors that affect the fallout estimates and the reference inventory. The results are presented as a schematic regional distribution map of ¹³⁷Cs reference inventories for the year 2012. A relationship between a reference inventory and topsoil concentration is also provided. The measured ¹³⁷Cs concentrations suggest that a minimum detectable activity (MDA) less than 0.5 Bq/kg is required for detection of ¹³⁷Cs activity in topsoils in the lowest reference inventory areas. This sensitivity should allow, at present, ¹³⁷Cs to be a useful tool for analysis of soil erosion in Southeast Asia, should also be a useful chronometer, and will be a useful tracer at least where the reference inventory is more than 500–600 Bq/m². This level of MDA has been demonstrated in previous studies to be achievable by gamma-ray spectrometry using non-destructive sample treatment. As the nuclide decays, sufficient will remain to be useful until the middle of this century in most areas in Peninsular Malaysia and southern maritime Southeast Asia, and a few decades more in the rest of the region.     

Coal-derived rates of atmospheric dust deposition during the Permian

Despite widespread evidence for atmospheric dust deposition prior to the Quaternary, quantitative rate data remains sparse. As dust influences both climate and biological productivity, the absence of quantitative dust data limits the comprehensiveness of models of pre-Quaternary climate and biogeochemical cycles. Here, we propose that inorganic matter contained in coal primarily records atmospheric dust deposition. To test this, we use the average concentration of inorganic matter in Permian coal to map global patterns and deposition rates of atmospheric dust over Pangea. The dust accumulation rate is calculated assuming Permian peat carbon accumulation rates in temperate climates were similar to Holocene rates and accounting for the loss of carbon during coalification. Coal-derived rates vary from 0.02 to 25 g m^− 2 year^− 1, values that fall within the present-day global range. A well-constrained East–West pattern of dust deposition corresponding to expected palaeoclimate gradients extends across Gondwana with maximum dust deposition rates occurring close to arid regions. A similar pattern is partially defined over the northern hemisphere. Patterns are consistent with the presence of two large global dust plumes centred on the tropics. The spatial patterns of dust deposition were also compared to dust cycle simulations for the Permian made with the Community Climate System Model version 3 (CCSM3). Key differences between the simulations and the coal data are the lack of evidence for an Antarctic dust source, higher than expected dust deposition over N and S China and greater dust deposition rates over Western Gondwana. This new coal-based dust accumulation rate data expands the pre-Neogene quantitative record of atmospheric dust and can help to inform and validate models of global circulation and biogeochemical cycles over the past 350 Myr.