The Diavik waste rock project: Initial geochemical response from a low sulfide waste rock pile

Three large-scale experimental waste rock piles (test piles) were constructed and instrumented at the Diavik Diamond Mine in the Northwest Territories, Canada, as part of an integrated field and laboratory study to measure and compare physical and geochemical characteristics of experimental, low sulfide waste rock piles at various scales. This paper describes the geochemical response during the first season from a test pile containing 0.053 wt.% S. Bulk drainage chemistry was measured at two sampling points for pH, Eh, alkalinity, dissolved cations and anions, and nutrients. The geochemical equilibrium model MINTEQA2 was used to interpret potential mineral solubility controls on water chemistry. The geochemical response characterizes the initial flushing response of blasting residues and oxidation products derived from sulfides in waste rock exposed to the atmosphere for less than 1 year. Sulfate concentrations reached 2000 mg L⁻¹ when ambient temperatures were >10 °C, and decreased as ambient temperatures declined to <0 °C. The pH decreased to <5, concomitant with an alkalinity minimum of <1 mg L⁻¹ (as total CaCO₃), suggesting all available alkalinity is consumed by acid-neutralizing reactions. Concentrations of Al and Fe were <0.36 and <0.11 mg L⁻¹, respectively. Trends of pH and alkalinity and the calculated saturation indices for Al and Fe (oxy)hydroxides suggest that dissolution of Al and Fe (oxy)hydroxide phases buffers the pH. The effluent water showed increased concentrations of dissolved Mn (<13 mg L⁻¹), Ni (<7.0 mg L⁻¹), Co (<1.5 mg L⁻¹), Zn (<0.5 mg L⁻¹), Cd (<0.008 mg L⁻¹) and Cu (<0.05 mg L⁻¹) as ambient temperatures increased. Manganese is released by aluminosilicate weathering, Ni and Co by pyrrhotite [Fe_1−xS] oxidation, Zn and Cd by sphalerite oxidation, and Cu by chalcopyrite [CuFeS₂] oxidation. No dissolved metals appear to have discrete secondary mineral controls. Changes in SO₄, pH and metal concentrations indicate sulfide oxidation is occurring and effluent concentrations are influenced by ambient temperatures and, possibly, increasing flow path lengths that transport reaction products from previously unflushed waste rock.     

Release,transport and attenuation of metals from an old tailings impoundment

The oxidation of sulfide minerals from mine wastes results in the release of oxidation products to groundwater and surface water. The abandoned high-sulfide Camp tailings impoundment at Sherridon, Manitoba, wherein the tailings have undergone oxidation for more than 70 a, was investigated by hydrogeological, geochemical, and mineralogical techniques. Mineralogical analysis indicates that the unoxidized tailings contain nearly equal proportions of pyrite and pyrrhotite, which make up to 60 wt% of the total tailings, and which are accompanied by minor amounts of chalcopyrite and sphalerite, and minute amounts of galena and arsenopyrite. Extensive oxidation in the upper 50 cm of the tailings has resulted in extremely high concentrations of dissolved SO₄ and metals and As in the tailings pore water (pH < 1, 129,000 mg L⁻¹ Fe, 280,000 mg L⁻¹ SO₄, 55,000 mg L⁻¹ Zn, 7200 mg L⁻¹ Al, 1600 mg L⁻¹ Cu, 260 mg L⁻¹ Mn, 110 mg L⁻¹ Co, 97 mg L⁻¹ Cd, 40 mg L⁻¹ As, 15 mg L⁻¹ Ni, 8 mg L⁻¹ Pb, and 3 mg L⁻¹ Cr). The acid released from sulfide oxidation has been extensive enough to deplete carbonate minerals to 6 m depth and to partly deplete Al-silicate minerals to a 1 m depth. Below 1 m, sulfide oxidation has resulted in the formation of a continuous hardpan layer that is >1 m thick. Geochemical modeling and mineralogical analysis indicate that the hardpan layer consists of secondary melanterite, rozenite, gypsum, jarosite, and goethite. The minerals indicated mainly control the dissolved concentrations of SO₄, Fe, Ca and K. The highest concentrations of dissolved metals are observed directly above and within the massive hardpan layer. Near the water table at a depth of 4 m, most metals and SO₄ sharply decline in concentration. Although dissolved concentrations of metals and SO₄ decrease below the water table, these concentrations remain elevated throughout the tailings, with up to 60,600 mg L⁻¹ Fe and 91,600 mg L⁻¹ SO₄ observed in the deeper groundwater. During precipitation events, surface seeps develop along the flanks of the impoundment and discharge pore water with a geochemical composition that is similar to the composition of water directly above the hardpan. These results suggest that shallow lateral flow of water from a transient perched water table is resulting in higher contaminant loadings than would be predicted if it were assumed that discharge is derived solely from the deeper primary water table. The abundance of residual sulfide minerals, the depletion of aluminosilicate minerals in the upper meter of the tailings and the presence of a significant mass of residual sulfide minerals in this zone after 70 a of oxidation suggest that sulfide oxidation will continue to release acid, metals, and SO₄ to the environment for decades to centuries.     

Diagenesis of organic matter in a 400 m organic rich sediment core from offshore Namibia using solid state 13C NMR and FTIR

Although rates and mechanisms of early diagenesis have been well studied, the effects of microbial metabolism on the molecular composition of the sedimentary organic matter (SOM) over long periods of time need more investigation. In this study, we characterize the early diagenesis of marine SOM from organic rich sediments of the Ocean Drilling Program site 1082 located off Namibia, in the vicinity of the Benguela coastal upwelling system. We used both Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (¹³C NMR) to assess the quantitative partitioning of the organic carbon into major compound classes (aliphatic, aromatic, ester, carboxylic, amide and carbons from carbohydrates). Then, we calculate the SOM composition in the main biomolecules (proteins, carbohydrates, lipids and lignin) on the basis of previous ¹³C NMR based estimates of the molecular composition of the organic mixtures. Results show that the SOM is still labile at 7 m below the seafloor (mbsf) and composed of about 25% proteins and 15% carbohydrates. With increasing depth, the protein content exponentially decreases to 13% at 367 mbsf, whereas the carbohydrate content decreases linearly to 11%. The lignin and lipid content consistently represent around 10% and 40% of the SOM, respectively, and show an increase with depth, due mostly to selective enrichment as the more labile components are lost by degradation. Thus, these components of the SOM are considered refractory at the depth scale considered. The calculated remineralization rates are extremely slow ranging from 5.6 mol C m⁻³ ky⁻¹ at the top of the core to 0.2 mol C m⁻³ ky⁻¹ according to the organic carbon flux to the seafloor. Knowing the labile carbon losses, we propose a method to calculate the initial TOC before the diagenesis took place.     

Comparison of dissolved inorganic and organic carbon yields and fluxes in the watersheds of tropical volcanic islands,examples from Guadeloupe (French West Indies)

Organic matter is an important factor that cannot be neglected when considering global carbon cycle. New data including organic matter geochemistry at the small watershed scale are needed to elaborate more constrained carbon cycle and climatic models. The objectives are to estimate the DOC and DIC yields exported from small tropical watersheds and to give strong constraints on the carbon hydrodynamic of these systems. To answer these questions, we have studied the geochemistry of eleven small watersheds around Basse-Terre volcanic Island in the French West Indies during different hydrological regimes from 2006 to 2008 (i.e. low water level versus floods). We propose a complete set of carbon measurements, including DOC and DIC concentrations, δ¹³C data, and less commonly, some spectroscopic indicators of the nature of organic matter. The DOC/DIC ratio varies between 0.07 and 0.30 in low water level and between 0.25 and 1.97 during floods, indicating that organic matter is mainly exported during flood events. On the light of the isotopic composition of DOC, ranging from ? 32.8 to ? 26.2‰ during low water level and from ? 30.1 to ? 27.2‰ during floods, we demonstrate that export of organic carbon is mainly controlled by perennial saprolite groundwaters, except for flood events during which rivers are also strongly influenced by soil erosion. The mean annual yields ranged from 2.5 to 5.7 t km^? 2 year^? 1 for the DOC and from 4.8 to 19.6 t km^? 2 year^? 1 for the DIC and exhibit a non-linear relationship with slopes of watersheds. The flash floods explain around 60% of the annual DOC flux and between 25 and 45% of the DIC flux, highlighting the important role of these extreme meteorological events on global carbon export in small tropical volcanic islands. From a carbon mass balance point of view the exports of dissolved carbon from small volcanic islands are important and should be included in global organic carbon budgets.     

Evaluation of the dissolved contaminant load transported by the Tinto and Odiel rivers (South West Spain)

The Tinto and Odiel rivers are heavily affected by acid mine drainage (AMD). However, the exact quantities of contaminants transported into the Huelva estuary and the Gulf of Cadiz are unknown. The existing previous investigations are, in general, based on studies with few data or incorrect methodology, and are therefore unreliable. This study aims to present a reliable estimation of the dissolved contaminant load transported by both rivers for the periods 1995/96 to 2002/03. The methodology used is based principally on the correlation between contaminant concentration and flow rate. The results show that both rivers transport enormous quantities of dissolved contaminants: 7900 t a⁻¹ of Fe, 5800 t a⁻¹ Al, 3500 t a⁻¹ Zn, 1700 t a⁻¹ Cu, 1600 t yr⁻¹ Mn and minor quantities of other metals. These values represent 60% of the global gross flux of dissolved Zn transported by rivers in to the ocean, and 17% of the global gross flux of dissolved Cu.     

Inorganic,isotopic, and organic composition of high-chloride water from wells in a coastal southern California aquifer

Chloride concentrations were as high as 230 mg/L in water from the surface discharge of long-screened production wells in Pleasant Valley, Calif., about 100 km NW of Los Angeles. Wells with the higher Cl⁻ concentrations were near faults that bound the valley. Depending on well construction, high-Cl⁻water from different sources may enter a well at different depths. For example, Cl⁻ concentration in the upper part of some wells completed in overlying aquifers influenced by irrigation return were as high as 220 mg/L, and Cl⁻ concentrations in water sampled within wells at depths greater than 450 m were as high as 500 mg/L. These high-Cl⁻ waters mix within the well during pumping and produce the water sampled at the surface discharge. Changes in the major ion, minor ion, trace element, and δ³⁴S and δ¹³C isotopic composition of water in wells with depth were consistent with changes resulting from SO₄ reduction, precipitation of calcite, and cation exchange. The chemical and isotopic composition of high-Cl⁻ water from deep wells trends towards the composition of oil-field production water from the study area. Chloride concentrations in oil-field production water present at depths 150 m beneath freshwater aquifers were 2200 mg/L, and Cl⁻ concentrations in underlying marine rock were as high as 4400 mg/L. High-Cl⁻ concentrations in water from deeper parts of wells were associated with dissolved organic C composed primarily of hydrophobic neutral compounds believed to be similar to those associated with petroleum in underlying deposits. These compounds would not be apparent using traditional sampling techniques and would not be detected using analytical methods intended to measure contamination.     

36Cl deposition rate reconstruction from bomb pulse until present: A study based on groundwater records

The radioactive isotope ³⁶Cl, with a half-life of 301 ka, is a valuable chronometer for estimation of groundwater residence time up to 2 millions of years. Aerial thermonuclear fission bomb tests, performed during the late 1950s, injected a massive amount of this isotope into the atmosphere, which exceeded the natural fallout signal. Since this bomb pulse, atmospheric ³⁶Cl deposition tends to return to natural fallout rate. The monitoring of this attenuation can provide a good opportunity to extend the use of this chronometer to shorter time spans. Venice’s lagoon alimentation zone shows groundwaters with residence times distributed over last fifty years. This permits the estimation of a continuous ³⁶Cl deposition curve, free from latitudinal and seasonal variations of the signal. Three old groundwater samples, with residence times comprised in the range −900 to −8000 BP, allow the estimation of a mean natural deposition of 49 at m⁻² s⁻¹ and are in good agreement with ³⁶Cl fallout observed for the last 40,000 years by (Plummer et al., 1997). For the bomb pulse period, a fallout of 5300 at m⁻² s⁻¹ was calculated. This was followed by a strong attenuation period, taking place until the 1980s, during which the fallout reached values ranging between 167 and 354 at m⁻² s⁻¹. The attenuation reached then a plateau: it experienced a slower lowering until the actual deposition, with fallout values calculated between 124 and 252 at m⁻² s⁻¹. This persistence of high deposition rate was classically attributed to biological and atmospherical recycling processes or underestimation of the natural atmospheric production of the ³⁶Cl. Additional source of ³⁶Cl production has been envisaged through the activation of chlorine radicals from stratospherical CFCs, leading to a ³⁶Cl production rate comparable with that of Ar spallation from the first approximation. Lastly, the latitudinal factor of the attenuation of the fallout rate is discussed and the impact of the jet streams is proposed as an explanation for the discrepancies in the attenuation rate.     

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.     

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.     

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.     

Solute generation and CO2 consumption during silicate weathering under subtropical,humid climate,northern Okinawa Island,Japan

The chemical characteristics of freshwaters draining the silicate rocks in the northern part of Okinawa Island were studied to understand solute generation processes, and to determine rates of chemical weathering and CO₂ consumption. It was observed that the water chemistry is highly influenced by marine aerosols, contributing more than 60% of total solute. Significant positive correlations observed for chloride versus dissolved silica and chloride versus bicarbonate suggest a strong influence of evapotranspiration on the seasonality of solute concentration. It was also found that chemical weathering has been highly advanced in which the dominant kaolinite minerals are being gibbsitized. Carbonic acid was found to be the major chemical weathering agent, releasing greater than 80% of weathering-derived dissolved cations and silica while the remaining portion was attributed to weathering by sulfuric acid generated via oxidation of pyrite contained in the rocks. The flux of basic cations, weathering-derived silica and CO₂ consumption were relatively high due to favourable climatic condition, topography and high rate of mechanical erosion. Silicate weathering rates for basic cations were estimated to be 6.7–9.7 ton km^− 2 y^− 1. Carbon dioxide consumed by silicate weathering was 334–471 kmol km^− 2 y^− 1 which was slightly higher than that consumed by carbonate weathering. In general, divalent cations (Mg and Ca) and bicarbonate alkalinity derived from carbonate dissolution were higher than those from silicate weathering. As a consequence, the evolution of chemical species in the freshwaters of northern area of Okinawa Island to a large extent could be explained by mixing of two components, characterized by waters with Na⁺ and Cl⁻ as predominant species and waters enriched with Ca²⁺ and HCO₃⁻.     

Modern carbon burial in Lake Qinghai,China

The quantification of carbon burial in lake sediments, and carbon fluxes derived from different origins are crucial to understand modern lacustrine carbon budgets, and to assess the role of lakes in the global carbon cycle. In this study, we estimated carbon burial in the sediment of Lake Qinghai, the largest inland lake in China, and the carbon fluxes derived from different origins. We find that: (1) The organic carbon burial rate in lake sediment is approximately 7.23 g m⁻² a⁻¹, which is comparable to rates documented in many large lakes worldwide. We determined that the flux of riverine particulate organic carbon (POC) is approximately 10 times higher than that of dissolved organic carbon (DOC). Organic matter in lake sediments is primarily derived from POC in lake water, of which approximately 80% is of terrestrial origin. (2) The inorganic carbon burial rate in lake sediment is slightly higher than that of organic carbon. The flux of riverine dissolved inorganic carbon (DIC) is approximately 20 times that of DOC, and more than 70% of the riverine DIC is drawn directly and/or indirectly from atmospheric CO₂. (3) Both DIC and DOC are concentrated in lake water, suggesting that the lake serves as a sink for both organic and inorganic carbon over long term timescales. (4) Our analysis suggests that the carbon burial rates in Lake Qinghai would be much higher in warmer climatic periods than in cold ones, implying a growing role in the global carbon cycle under a continued global warming scenario.     

CO2 emissions and heat flow through soil,fumaroles, and steam heated mud pools at the Reykjanes geothermal area,SW Iceland

Carbon dioxide emissions and heat flow through soil, steam vents and fractures, and steam heated mud pools were determined in the Reykjanes geothermal area, SW Iceland. Soil diffuse degassing of CO₂ was quantified by soil flux measurements on a 600 m by 375 m rectangular grid using a portable closed chamber soil flux meter and the resulting data were analyzed by both a graphical statistical method and sequential Gaussian simulations. The soil temperature was measured in each node of the grid and used to evaluate the heat flow. The heat flow data were also analyzed by sequential Gaussian simulations. Heat flow from steam vents and fractures was determined by quantifying the amount of steam emitted from the vents by direct measurements of steam flow rate. The heat loss from the steam heated mud pools was determined by quantifying the rate of heat loss from the pools by evaporation, convection, and radiation. The steam flow rate into the pools was calculated from the observed heat loss from the pools, assuming that steam flow was the only mechanism of heat transport into the pool. The CO₂ emissions from the steam vents and mud pools were determined by multiplying the steam flow rate from the respective sources by the representative CO₂ concentration of steam in the Reykjanes area. The observed rates of CO₂ emissions through soil, steam vents, and steam heated mud pools amounted to 13.5 ± 1.7, 0.23 ± 0.05, and 0.13 ± 0.03 tons per day, respectively. The heat flow through soil, steam vents, and mud pools was 16.9 ± 1.4, 2.2 ± 0.4, and 1.2  ± 0.1 MW, respectively. Heat loss from the geothermal reservoir, inferred from the CO₂ emissions through the soil amounts to 130 ± 16 MW of thermal energy. The discrepancy between the observed heat loss and the heat loss inferred from the CO₂ emissions is attributed to steam condensation in the subsurface due to interactions with cold ground water. These results demonstrate that soil diffuse degassing can be a more reliable proxy for heat loss from geothermal systems than soil temperatures. The soil diffuse degassing at Reykjanes appears to be strongly controlled by the local tectonics. The observed diffuse degassing defines 3–5 elongated N–S trending zones (000–020°). The orientation of the diffuse degassing structures at Reykjanes is consistent with reported trends of right lateral strike slip faults in the area. The natural CO₂ emissions from Reykjanes under the current low-production conditions are about 16% of the expected emissions from a 100 MWe power plant, which has recently been commissioned at Reykjanes.     

Rates and causes of recent global sea-level rise inferred from long tide gauge data records

Tide gauge data at seven sites of the Permanent Service for Mean Sea Level (PSMSL), with information for relative sea-level during the past 140–200 yr, were analyzed to examine the rates and causes of the global sea-level rise (GSLR) during the twentieth century. By subtracting linear trends for relative sea-level rise during the past 100 yr from the observed data, we get the apparent GSLRs of ∼1 mm yr⁻¹ for five sites around the Baltic Sea and Brest. The rate for San Francisco is significantly larger than this, with an optimum value ∼2 mm yr⁻¹. The spatial difference of ∼1 mm yr⁻¹ between these sites is reasonably explained by the recent melting of the Greenland ice sheet with an equivalent sea-level rise of ∼1 mm yr⁻¹. The predicted relative sea-level change for this melting scenario is 0.5 mm yr⁻¹ at sites around the Baltic Sea and Brest, and 1.5 mm yr⁻¹ for San Francisco. The residuals between observations and predictions, ∼0.5 mm yr⁻¹ at all sites, may be contributed by thermal expansion of seawater and/or other melting sources. These results suggest the rate of twentieth-century GSLR to be 1.5 mm yr⁻¹.     

Accumulation of terrestrial organic carbon on an active continental margin offshore southwestern Taiwan: Source-to-sink pathways of river-borne organic particles

Sediment samples (213 sites) collected from the tectonic-active continental margin, offshore southwestern Taiwan were analyzed for grain sizes, organic carbon, nitrogen and carbon isotopic composition to obtain mass accumulation rate of terrestrial organic carbon and carbon budget to evaluate fate of terrestrial organic carbon from small mountainous rivers on the continental margin offshore southwestern Taiwan. Terrestrial organic carbon accumulation rates range from 0.29 to 45.6 g C m⁻² yr⁻¹ with a total accumulation budget of 0.063 Mt yr⁻¹, which accounts for less than 13% of total river particulate organic carbon loads exported from the adjacent rivers, the Gaoping (a.k.a., Kaoping), Erhjen and Tsengwen rivers. This low burial efficiency of terrestrial organic carbon demonstrated that a majority of river-borne particles together with organic materials was moved away from the study area.For the river-borne particles from the Gaoping river, a pair of depocenters in the upper slope flanking the Gaoping submarine canyon are the locations where the maximum TC_org accumulation rate were observed which hold up to 45% (0.016 Mt yr⁻¹) of the calculated accumulation found in the study region. On the other hand, the occurrence of higher-fraction terrestrial organic carbon in the upper and middle Gaoping submarine canyon suggests that a majority of particulate organic carbon of the Gaoping river was transported directly into the deep-sea basin through the Gaoping submarine canyon. Our results demonstrated that active margin with narrow shelf and slope is not an efficient sink for the large amount of terrigenous organic carbon supplied by the small rivers, but, a transient environment for these river derived particles.     

Helium–carbon relationships in geothermal fluids of western Anatolia,Turkey

We investigate the helium, carbon and oxygen–hydrogen isotopic systematics and CO₂/³He ratios of 8 water and 6 gas samples collected from 12 geothermal fields in western Anatolia (Turkey). ³He/⁴He ratios of the samples (R) normalized to the atmospheric ³He/⁴He ratio (R_A = 1.39 × 10^? 6) range from 0.27 to 1.67 and are significantly higher than the crustal production value of 0.05. Fluids with relatively high R / R_A values are generally found in areas of significant heat potential (K?z?ldere and Tuzla fields). CO₂/³He ratios of the samples, ranging from 1.6 × 10⁹ to 2.3 × 10¹⁴, display significant variation and are mostly higher than values typical of an upper mantle source (2 × 10⁹). The δ¹³C (CO₂) and δ¹³C (CH₄) values of all fluids vary from ? 8.04 to + 0.35‰ and ? 25.80 to ? 23.92‰ (vs. PDB), respectively. Stable isotope values (δ¹⁸O–δD) of the geothermal waters are conformable with the Mediterranean Meteoric Water Line and indicate a meteoric origin. The temperatures calculated by gas geothermometry are significantly higher than estimates from chemical geothermometers, implying that either equilibrium has not been attained for the isotope exchange reaction or that isotopic equilibration was disturbed due to gas additions en route to the surface.Evaluation of He–CO₂ abundances indicates that hydrothermal degassing and calcite precipitation (controlled probably by adiabatic cooling due to degassing) significantly fractionate the elemental ratio (CO₂/³He) in geothermal waters. Such processes do not affect gas phase samples to anywhere near the same extent. For the gas samples, mixing between mantle and various crustal sources appears to be the main control on the observed He–C systematics: however, crustal inputs dominate the CO₂ inventory. Considering that limestone is the main source of carbon (～ 70 to 97% of the total carbon inventory), the carbon flux from the crust is found to be at least 20 times that from the mantle. As to the He-inventory, the mantle-derived component is found to vary up to 21% of the total He content and is probably transferred to the crust by fluids degassed from deep mantle melts generated in association with the elevated geotherm and adiabatic melting accompanying current extension. The range of ³He/enthalpy ratios (0.000032 to 0.19 × 10^? 12 cm³ STP/J) of fluids in western Anatolia is consistent with the release of both helium and heat from contemporary additions of mantle-derived magmas to the crust. The deep faults appear to have facilitated the deep circulation of the fluids and the transport of mantle volatiles and heat to the surface.     

Dissolved and particulate zinc and nickel in the Yangtze River (China): Distribution,sources and fluxes

Dissolved and particulate Zn and Ni concentrations were determined at 76 locations along the Yangtze River basin from the headwaters to the estuary during flood and dry seasons. Spatial and temporal variations of Zn and Ni were investigated and six major source zones were identified. The Three Gorges Dam (TGD) blocked most of the suspended loads and extremely low concentration of Zn and Ni were observed downstream of the dam. Dissolved (ranging from 0.062 to 8.0 μg L⁻¹) and particulate (ranging from 12 to 110 mg kg⁻¹) Ni showed similar levels of concentrations during flood and dry seasons, whereas dissolved (ranging from 0.43 to 49 μg L⁻¹) and particulate (ranging from 54 to 1100 mg kg⁻¹) Zn were slightly and much lower in the flood season than dry season, respectively. This was attributed to the increased water discharge during the flood season causing a dilution effect and sediment resuspension. In the flood season, average concentrations of Zn and Ni were higher in the main channel than in tributaries, due to soil erosion and mining activities providing the dominant inputs. The situation was opposite in the dry season, attributed to the contribution of municipal sewage, industrial activities, and waste disposal. During the flood season, dissolved Zn and Ni concentrations were negatively correlated with pH. Water and suspended particulate matter (SPM) from the upper reaches, middle reaches, and lower reaches of the Yangtze River were characterized by their Zn and Ni concentrations. The Panzhihua, Nanling and Tongling mining areas were considered as the most important source zones of particulate Zn and Ni. The Chongqing region, Wuhan region and the Yangtze River Delta provided most of the dissolved Zn and Ni inputs into the river. Annual net flux of Zn (10–72 × 10⁵ kg a⁻¹) and Ni (5.0–19 × 10⁵ kg a⁻¹) in each source zone were estimated according to their respective influent and effluent fluxes. Contributions of the source zones to Zn and Ni transport decreased from the upper reaches to the lower reaches.     

Groundwater fluxes into a submerged sinkhole area,Central Italy,using radon and water chemistry

The groundwater contribution into Green Lake and Black Lake (Vescovo Lakes Group), two cover collapse sinkholes in Pontina Plain (Central Italy), was estimated using water chemistry and a ²²²Rn budget. These data can constrain the interactions between sinkholes and deep seated fluid circulation, with a special focus on the possibility of the bedrock karst aquifer feeding the lake. The Rn budget accounted for all quantifiable surface and subsurface input and output fluxes including the flux across the sediment–water interface. The total value of groundwater discharge into Green Lake and Black Lake (∼540 ± 160 L s⁻¹) obtained from the Rn budget is lower than, but comparable with historical data on the springs group discharge estimated in the same period of the year (800 ± 90 L s⁻¹). Besides being an indirect test for the reliability of the Rn-budget “tool”, it confirms that both Green and Black Lake are effectively springs and not simply “water filled” sinkholes. New data on the water chemistry and the groundwater fluxes into the sinkhole area of Vescovo Lakes allows the assessment of the mechanism responsible for sinkhole formation in Pontina Plain and suggests the necessity of monitoring the changes of physical and chemical parameters of groundwater below the plain in order to mitigate the associated risk.     

Characterisation and isotopic evolution of saline waters of the Outokumpu Deep Drill Hole,Finland – Implications for water origin and deep terrestrial biosphere

The isotopic composition of water and dissolved Sr as well as other geochemical parameters at the 2516 m deep Outokumpu Deep Drill Hole, Finland were determined. The drill hole is hosted by Palaeoproterozoic turbiditic metasediments, ophiolite-derived altered ultramafic rocks and pegmatitic granitoids. Sodium–Ca–Cl and Ca–Na–Cl-rich waters (total dissolved solids up to ca. 70 g L⁻¹) containing significant amounts of gas, mainly CH₄ (up to 32 mmol L⁻¹), N₂ (up to 10 mmol L⁻¹), H₂ (up to 3.1 mmol L⁻¹) and He (up to 1.1 mmol L⁻¹) discharge from fracture zones into the drill hole. This water is distinct from the shallow fresh groundwater of the area, and has an isotopic composition typical of shield brines that have been modified during long-term water–rock interaction. Based on water stable isotopes and geochemistry, the drill hole water profile can be divided into five water types, each discharging from separate fracture systems and affected by the surrounding rocks. The δ²H varies from −90‰ to −56‰ (VSMOW) and δ¹⁸O from −13.5‰ to −10.4‰ (VSMOW), plotting clearly above the Global and Local Meteoric Water Lines on a δ²H vs. δ¹⁸O diagram. The ⁸⁷Sr/⁸⁶Sr ratios range between 0.72423 and 0.73668. Simple two-component mixing between ²H and ¹⁸O rich end-member brine and meteoric water cannot explain the water stable isotopic composition and trends observed. Instead, hydration of silicates by ancient groundwaters recharged under different climatic conditions, warmer than at present, is the most likely mechanism to have caused the variation of the δ²H and δ¹⁸O values. Water types correlate with changes in microbial communities implying that different ecosystems occur at different depths. The different water types and microbial populations have remained isolated from each other and from the surface for long periods of time, probably tens of millions of years.     

Assessing the potential for CO2 adsorption in a subbituminous coal,Huntly Coalfield,New Zealand,using small angle scattering techniques

Small angle scattering techniques (SAXS and SANS) have been used to investigate the microstructural properties of the subbituminous coals (R_max 0.42–0.45%) from the Huntly Coalfield, New Zealand. Samples were collected from the two thick (> 5 m) coal seams in the coalfield and have been analysed for methane and carbon dioxide sorption capacity, petrography, pore size distribution, specific surface area and porosity.Specific surface area (SSA) available for carbon dioxide adsorption, extrapolated to a probe size of 4 Å, ranged from 1.25 × 10⁶ cm^? 1 to 4.26 × 10⁶ cm^? 1 with total porosity varying from 16% to 25%. Porosity was found to be predominantly composed of microporosity, which contributed the majority of the available SSA. Although considerable variation was seen between samples, the results fit well with published rank trends.Gas holding capacity at the reservoir pressure (approximately 4 MPa) ranged from 2.63 to 4.18 m³/t for methane on a dry, ash-free basis (daf) and from 22.00 to 23.72 m³/t daf for carbon dioxide. The resulting ratio of CO₂:CH₄ ranged from 5.7 to 8.6, with an average of 6.7:1.Holding capacities for both methane and carbon dioxide on a dry ash free basis (daf) were found to be correlated with sample microporosity. However, holding capacities for the two gases on an as analysed (aa) basis (that is including mineral matter and moisture), showed no such correlation. Carbon dioxide (aa) does show a negative correlation with both specific surface area and microporosity. As the coals have low inorganic matter content, the reversal is thought to be related to moisture which is likely concentrated in the pore size range 12.5–125 Å. Methane holding capacity, both daf and aa, correlates with macroporosity, thus suggesting that the holding capacity of micropores is diminished by the presence of moisture in the pores.