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Sample records for carbonate weathering southern

  1. Carbon dioxide fluxes associated with synoptic weather events over a southern inland water

    NASA Astrophysics Data System (ADS)

    Liu, H.; Zhang, Q.; Gao, Z.

    2015-12-01

    Evidence indicates that inland waters play an important role in regional and global carbon budget through releasing a substantial carbon into the atmosphere. To better quantify how environmental variables affect CO2 exchange between inland waters and the atmosphere and its temporal variations, we have conducted direct, long-term measurements of CO2 fluxes across the water-atmosphere interface over a large southern open water of Ross Barnett Reservoir in central Mississippi. Our data indicate that large CO2 flux pulses occurred occasionally throughout the course of a year with the duration of a few days for each pulse. Here we analyzed and demonstrated that these CO2 flux pulses were associated with the passages of synoptic weather events. Our preliminary results indicated that these synoptic weather events (e.g., extratropical clones and cold air bursts) led to the enhanced mechanical mixing due to increasing wind speeds and the instability of the atmospheric surface layer due to the decreasing air temperature. As a consequence, in-water processes were also substantially altered accordingly. Due to the dramatic decrease in air temperature caused by the events, the temperature in the water surface layer was largely reduced, generating in-water convection conditions and thus leading to the increased depths of the mixing layer in the water, as reflected by the water temperature profiles. The enhanced mechanical mixing in the atmospheric surface layer may have further contributed to the deepened mixing layer in the water. Our suggestions suggest that high CO2 effluxes during the pulse events were largely attributed to changes in the water-side physical processes that are directly linked to rapid changes in atmospheric processes associated with synoptic weather events. Given its substantial contribution of CO2 flux pulses to carbon emission, such physical processes should be taken into account when carbon emissions from inland waters are quantified.

  2. Silicate or Carbonate Weathering: Fingerprinting Sources of Dissolved Inorganic Carbon Using δ13C in a Tropical River, Southern India

    NASA Astrophysics Data System (ADS)

    Bhagat, H.; Ghosh, P.

    2015-12-01

    Rivers are an inherently vital resource for the development of any region and their importance is highlighted by the presence of many ancient human civilizations adjacent to river systems. δ13C - Si/HCO3 systematics has been applied to large south Indian rivers which drain the Deccan basaltic traps in order to quantify their relative contributions from silicate and carbonate weathering. This study investigates δ13C - Si/HCO3 systematics of the Cauvery River basin which flows through silicate lithology in the higher reaches and carbonate lithology with pedogenic and marine carbonates dominating the terrain in the lower reaches of the basin. The samples for the present study were collected at locations within the watershed during Pre-Monsoon and Monsoon Season 2014. The measurements of stable isotope ratios of δ13CDIC and were accomplished through a Thermo Scientific GasBench II interface connected to a MAT 253 IRMS. We captured a large spatial variation in δ13C and Si/HCO3 values during both seasons; Pre-Monsoon δ13C values ranges between -17.57‰ to -4.02‰ and during Monsoon it varies between -9.19‰ to +0.61‰. These results indicate a two end-member mixing component i.e. a silicate and a carbonate end member; governing the weathering interactions of the Cauvery River. Within the drainage basin, we identified silicate and carbonate dominating sources by using contributions of DIC and δ13C. Si/HCO3 values for Pre-Monsoon ranges between 0.028 - 0.67 and for Monsoon it varies between 0.073 - 0.80. Lighter δ13C composition was observed at sampling sites at higher altitude in contrast to sampling sites at flood plain which show relatively enriched δ13C which indicate mixing of soil derived CO2 with C4 plants. Result suggests dominance of carbonate weathering during the Monsoon Period, while silicate weathering is pronounced during Pre- Monsoon period.

  3. Carbon-14 terrestrial ages and weathering of 27 meteorites from the southern high plains and adjacent areas (USA)

    NASA Astrophysics Data System (ADS)

    Jull, A. J. T.; Donahue, D. J.; Cielaszyk, E.; Wlotzka, F.

    1993-06-01

    We report on a series of 27 C-14 terrestrial ages of meteorites from four states in the central and southwestern U.S. These results were compared to the earlier work of Boeckl (1972). Our results showed that the weathering rate for destruction of meteorites is lower than suggested by Boeckl. We estimate a 'half-life' for removal of meteorites of about 10 to 15 ka, similar to that derived for Roosevelt County meteorites. We also studied the weathering of these meteorites compared to terrestrial age. Only a weak correlation was observed, and for these meteorites the degree of weathering can only be taken as a weak indicator of terrestrial residence time. We also measured the delta-C-13 and C-14 and amount of weathering-product carbonates which show some interesting variations with the length of time the meteorites have been exposed to weathering.

  4. Rapid soil production and weathering in the Southern Alps, New Zealand.

    PubMed

    Larsen, Isaac J; Almond, Peter C; Eger, Andre; Stone, John O; Montgomery, David R; Malcolm, Brendon

    2014-02-07

    Evaluating conflicting theories about the influence of mountains on carbon dioxide cycling and climate requires understanding weathering fluxes from tectonically uplifting landscapes. The lack of soil production and weathering rate measurements in Earth's most rapidly uplifting mountains has made it difficult to determine whether weathering rates increase or decline in response to rapid erosion. Beryllium-10 concentrations in soils from the western Southern Alps, New Zealand, demonstrate that soil is produced from bedrock more rapidly than previously recognized, at rates up to 2.5 millimeters per year. Weathering intensity data further indicate that soil chemical denudation rates increase proportionally with erosion rates. These high weathering rates support the view that mountains play a key role in global-scale chemical weathering and thus have potentially important implications for the global carbon cycle.

  5. Landslide disturbance: implications for chemical weathering, vegetation and carbon cycling

    NASA Astrophysics Data System (ADS)

    Milledge, D.; Hilton, R. G.

    2011-12-01

    Landslides disturb physical and ecological systems by periodically stripping away soil and vegetation. This turnover influences the makeup and productivity of vegetation as well as the chemical weathering rate for the soil. Recent research has highlighted these links focusing on landslide magnitude and frequency and calculating turnover on a catchment wide basis. However, landslide probability and therefore turnover is not uniform in space. We investigate the influence of this spatial variability on the frequency distribution of landslide turnover and its implications for: vegetation disturbance, carbon cycling and chemical weathering. We use first synthetic landslide risk distributions then real distributions from the Western Southern Alps and Oregon Coast Range. We use these to generate turnover distributions then compare these with the turnover rate predicted assuming spatially uniform landslide probability. We use published relations to work through the implications for: vegetation disturbance, carbon cycling and chemical weathering. We find that: 1) landslide turnover rates are too slow even in the most active parts of the landscape to chronically disturb the vegetation; 2) the changes to productivity are generally subtle leading to only minor changes in the carbon flux; and 3) landslide related chemical weathering rates are reduced in areas with strongly non-uniform landslide risk distributions.

  6. Large-Scale Weather Disturbances in Mars’ Southern Extratropics

    NASA Astrophysics Data System (ADS)

    Hollingsworth, Jeffery L.; Kahre, Melinda A.

    2015-11-01

    Between late autumn and early spring, Mars’ middle and high latitudes within its atmosphere support strong mean thermal gradients between the tropics and poles. Observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that this strong baroclinicity supports intense, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). These extratropical weather disturbances are key components of the global circulation. Such wave-like disturbances act as agents in the transport of heat and momentum, and generalized scalar/tracer quantities (e.g., atmospheric dust, water-vapor and ice clouds). The character of large-scale, traveling extratropical synoptic-period disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a moderately high-resolution Mars global climate model (Mars GCM). This Mars GCM imposes interactively lifted and radiatively active dust based on a threshold value of the surface stress. The model exhibits a reasonable "dust cycle" (i.e., globally averaged, a dustier atmosphere during southern spring and summer occurs). Compared to their northern-hemisphere counterparts, southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are examined. Simulations that adapt Mars’ full topography compared to simulations that utilize synthetic topographies emulating key large-scale features of the southern middle latitudes indicate that Mars’ transient barotropic/baroclinic eddies are highly influenced by the great impact basins of this hemisphere (e.g., Argyre and Hellas). The occurrence of a southern storm zone in late winter and early spring appears to be anchored to the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre

  7. How accurate are the weather forecasts for Bierun (southern Poland)?

    NASA Astrophysics Data System (ADS)

    Gawor, J.

    2012-04-01

    Weather forecast accuracy has increased in recent times mainly thanks to significant development of numerical weather prediction models. Despite the improvements, the forecasts should be verified to control their quality. The evaluation of forecast accuracy can also be an interesting learning activity for students. It joins natural curiosity about everyday weather and scientific process skills: problem solving, database technologies, graph construction and graphical analysis. The examination of the weather forecasts has been taken by a group of 14-year-old students from Bierun (southern Poland). They participate in the GLOBE program to develop inquiry-based investigations of the local environment. For the atmospheric research the automatic weather station is used. The observed data were compared with corresponding forecasts produced by two numerical weather prediction models, i.e. COAMPS (Coupled Ocean/Atmosphere Mesoscale Prediction System) developed by Naval Research Laboratory Monterey, USA; it runs operationally at the Interdisciplinary Centre for Mathematical and Computational Modelling in Warsaw, Poland and COSMO (The Consortium for Small-scale Modelling) used by the Polish Institute of Meteorology and Water Management. The analysed data included air temperature, precipitation, wind speed, wind chill and sea level pressure. The prediction periods from 0 to 24 hours (Day 1) and from 24 to 48 hours (Day 2) were considered. The verification statistics that are commonly used in meteorology have been applied: mean error, also known as bias, for continuous data and a 2x2 contingency table to get the hit rate and false alarm ratio for a few precipitation thresholds. The results of the aforementioned activity became an interesting basis for discussion. The most important topics are: 1) to what extent can we rely on the weather forecasts? 2) How accurate are the forecasts for two considered time ranges? 3) Which precipitation threshold is the most predictable? 4) Why

  8. Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks.

    PubMed

    Torres, Mark A; Moosdorf, Nils; Hartmann, Jens; Adkins, Jess F; West, A Joshua

    2017-08-15

    Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO2, we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean-atmosphere CO2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O2 Future work on glaciation-weathering-carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals.

  9. Carbonate weathering along a climatic gradient in the Jura Mountains

    NASA Astrophysics Data System (ADS)

    Gaillardet, J.; Calmels, D.; Francois, L. M.

    2013-12-01

    A significant portion of the Critical Zone of the Earth is developed on carbonate rocks. In order to investigate the control of carbonate weathering and in particular its response to climate change, we sampled rivers and springs in a well-drained pure carbonate area subjected to strong environmental gradients, the Jura Mountains, Western Europe. The intensity of carbonate weathering, shows a gradual two-fold increase with decreasing elevation from 1200m to 300m. These changes cannot be interpreted in terms of thermodynamic equilibrium and changes of the thermodynamic constants with temperature. The change in vegetation species from deciduous forest in plains to coniferous forest in altitude appears as a major control. Using the ecological and hydrological ASPECTS model, we show that the availability of soil CO2, known as a main weathering agent of rocks, is directly linked to the spatial distribution of vegetation species over the study area. The type of vegetation drives temporal and spatial variations of the carbon and water budgets in soils and therefore partly controls both carbonate weathering intensity and rates. At a given runoff, carbonate weathering rates are classically 20-30% higher under deciduous vegetation cover than under coniferous forest. This study demonstrates that carbonate weathering is strongly sensitive to the ecosystem dynamics, a conclusion that may be much more general, and suggests that carbonate weathering quickly reacts to any global change and/or land use modification.

  10. Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

    NASA Astrophysics Data System (ADS)

    Torres, Mark A.; Moosdorf, Nils; Hartmann, Jens; Adkins, Jess F.; West, A. Joshua

    2017-08-01

    Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO2, we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean–atmosphere CO2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O2. Future work on glaciation–weathering–carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals.

  11. Carbon dioxide efficiency of terrestrial enhanced weathering.

    PubMed

    Moosdorf, Nils; Renforth, Phil; Hartmann, Jens

    2014-05-06

    Terrestrial enhanced weathering, the spreading of ultramafic silicate rock flour to enhance natural weathering rates, has been suggested as part of a strategy to reduce global atmospheric CO2 levels. We budget potential CO2 sequestration against associated CO2 emissions to assess the net CO2 removal of terrestrial enhanced weathering. We combine global spatial data sets of potential source rocks, transport networks, and application areas with associated CO2 emissions in optimistic and pessimistic scenarios. The results show that the choice of source rocks and material comminution technique dominate the CO2 efficiency of enhanced weathering. CO2 emissions from transport amount to on average 0.5-3% of potentially sequestered CO2. The emissions of material mining and application are negligible. After accounting for all emissions, 0.5-1.0 t CO2 can be sequestered on average per tonne of rock, translating into a unit cost from 1.6 to 9.9 GJ per tonne CO2 sequestered by enhanced weathering. However, to control or reduce atmospheric CO2 concentrations substantially with enhanced weathering would require very large amounts of rock. Before enhanced weathering could be applied on large scales, more research is needed to assess weathering rates, potential side effects, social acceptability, and mechanisms of governance.

  12. Cenozoic carbon cycle imbalances and a variable weathering feedback

    NASA Astrophysics Data System (ADS)

    Caves, Jeremy K.; Jost, Adam B.; Lau, Kimberly V.; Maher, Kate

    2016-09-01

    The long-term stability of Earth's climate and the recovery of the ocean-atmosphere system after carbon cycle perturbations are often attributed to a stabilizing negative feedback between silicate weathering and climate. However, evidence for the operation of this feedback over million-year timescales and in response to tectonic and long-term climatic change remains scarce. For example, the past 50 million years of the Cenozoic Era are characterized by long-term cooling and declining atmospheric CO2 (pCO2). During this interval, constant or decreasing carbon fluxes from the solid Earth to the atmosphere suggest that stable or decreasing weathering fluxes are needed to balance the carbon cycle. In contrast, marine isotopic proxies of weathering (i.e., 87Sr/86Sr, δ7 Li , and 187Os/188Os) are interpreted to reflect increasing weathering fluxes. Here, we evaluate the existence of a negative feedback by reconstructing the imbalance in the carbon cycle during the Cenozoic using the surface inventories of carbon and alkalinity. Only a sustained 0.25-0.5% increase in silicate weathering is necessary to explain the long-term decline in pCO2 over the Cenozoic. We propose that the long-term decrease in pCO2 is due to an increase in the strength of the silicate weathering feedback (i.e., the constant of proportionality between the silicate weathering flux and climate), rather than an increase in the weathering flux. This increase in the feedback strength, which mirrors the marine isotope proxies, occurs as transient, <1 million year increases in the weathering flux, which remove CO2. As runoff and temperature decline in response, the integrated weathering flux over >1 million year timescales remains invariant to match the long-term inputs of carbon. Over the Cenozoic, this results in stable long-term weathering fluxes even as pCO2 decreases. We attribute increasing feedback strength to a change in the type and reactivity of rock in the weathering zone, which collectively has

  13. Seafloor Weathering Dependence on Temperature and Dissolved Inorganic Carbon

    NASA Astrophysics Data System (ADS)

    Abbot, D. S.; Farahat, N. X.; Archer, D. E.

    2015-12-01

    Most thinking on Earth's carbon cycle implicates silicate weathering as the dominant control of atmospheric CO2 concentration over long timescales. Recent analyses of alteration of basalt at the seafloor, however, suggest that seafloor weathering (low-temperature (<60C) chemical alteration of the upper oceanic crust due to hydrothermal seawater circulation) increases dramatically in warm, high CO2 periods of Earth's history. This raises the possibility that seafloor weathering could complement silicate weathering in maintaining Earth's long term climate stability. Moreover, seafloor weathering would be the only type of weathering available on an exoplanet entirely covered by water, so understanding how it might work is essential for understanding the habitable zones of such waterworlds. We have built a 2D numerical model of the flow of seawater through porous basalt coupled to chemical alteration reactions that can calculate alkalinity fluxes and carbonate deposition (seafloor weathering). I will present simulations in which we vary the seawater temperature and dissolved inorganic carbon concentration, which are boundary conditions to our model, over large ranges. These results will provide a constraint on the ability of seafloor weathering to act as an effective climate buffer on Earth and other planets. I can't give you a preview of the results yet because at the time of writing this abstract we haven't completed the simulations!

  14. Enhanced oxidative weathering in glaciated mountain catchments: A stabilising feedback on atmospheric carbon dioxide?

    NASA Astrophysics Data System (ADS)

    Horan, K.; Hilton, R. G.; Burton, K. W.; Selby, D. S.; Ottley, C. J.

    2015-12-01

    Mountain belts act as sources of carbon dioxide (CO2) to the atmosphere if physical erosion and exhumation expose rock-derived organic carbon ('petrogenic' organic carbon, OCpetro) to chemical weathering. Estimates suggest 15x1021g of carbon is stored in rocks globally as OCpetro, ~25,000 times the amount of carbon in the pre-industrial atmosphere. Alongside volcanic and metamorphic degassing, OCpetro weathering is thought to be the main source of CO2 to the atmosphere over geological timescales. Erosion in mountain river catchments has been shown to enhance oxidative weathering and CO2 release. However, we still lack studies which quantify this process. In addition, it is not clear how glaciation may impact OCpetro oxidation. In analogy with silicate weathering, large amounts of fine sediment in glacial catchments may enhance oxidative weathering. Here we quantify oxidative weathering in nine catchments draining OCpetro bearing rocks in the western Southern Alps, New Zealand. Using rhenium (Re) as a tracer of oxidative weathering, we develop techniques to precisely measure Re concentration at sub-ppt levels in river waters. Using [Re]water/[Re]rock as a weathering tracer, we estimate that the weathering efficiency in glacial catchments is >4 times that of non-glacial catchments. Combining this with the OCpetro content of rocks and dissolved Re flux, we estimate the CO2 release by OCpetro oxidation. The analysis suggests that non-glacial catchments in the western Southern Alps release similar amounts of CO2 as catchments in Taiwan where erosion rates are comparable. In this mountain belt, the CO2 release does not negate CO2 drawdown by silicate weathering and by riverine transfer of organic matter. Based on our results, we propose that mountain glaciation may greatly enhance OCpetro oxidation rates. Depending on the global fluxes involved, this provides a feedback to damp low atmospheric CO2 levels and global cooling. During glacial periods (low CO2, low global

  15. Geophysics in the Critical Zone: Constraints on Deep Weathering and Water Storage Potential in the Southern Sierra CZO

    NASA Astrophysics Data System (ADS)

    Holbrook, W.; Riebe, C. S.; Hayes, J. L.; Reeder, K.; Harry, D. L.; Malazian, A. I.; Dosseto, A.; Hartsough, P. C.; Hopmans, J. W.

    2012-12-01

    Quantifying the depth and degree of subsurface weathering in landscapes is crucial for quantitative understanding of the biogeochemistry of weathering, the mechanics of hillslope sediment transport, and biogeochemical cycling of nutrients and carbon over both short and long timescales. Although the degree of weathering can be readily measured from geochemical and physical properties of regolith and rock, many distributed samples are needed to measure it over broad spatial scales. Moreover, quantifying the thickness of subsurface weathering has remained challenging, in part because the interface between altered and unaltered rock is often buried at difficult to access depths. To overcome these challenges, we combined seismic refraction and resistivity surveys to estimate regolith thickness and generate representative hillslope-scale images of subsurface weathering and water storage at the Southern Sierra Critical Zone Observatory (SSCZO). Inferred seismic velocities and electrical resistivities of the subsurface provide evidence for a weathering zone with thickness ranging from 10 to 35 m (average = 23 m) along one intensively studied transect. This weathering zone consists of roughly equal thicknesses of saprolite (P-velocity < 2 km/s) and moderately weathered bedrock (P-velocity < 4 km/s). We use a rock physics model of seismic velocities, based on Hertz-Mindlin contact theory, to estimate lateral and vertical variations in porosity as a metric of water storage potential along the transect. Inferred porosities are as high as 55% near the surface and decrease to zero at the base of weathered rock. Model-predicted porosities are broadly consistent with values measured from physical properties of saprolite, suggesting that our analysis of the geophysical data provides realistic estimates of subsurface water storage potential. A major advantage of our geophysical approach is that it quickly and non-invasively quantifies porosity over broad vertical and lateral scales

  16. Carbon in weathered ordinary chondrites from Roosevelt County

    NASA Technical Reports Server (NTRS)

    Ash, R. D.; Pillinger, C. T.

    1993-01-01

    A suite of Roosevelt County ordinary chondrites of known terrestrial age have been analyzed for carbon content and isotopic composition. Initial results indicate that significant carbon contamination is evident only in samples with a terrestrial age greater than 40 ka. These samples are of weathering grade D and E and contain three times more carbon than the less weathered samples. The soil in which they were preserved has a carbon content of ca. 1.5 percent. Over 200 meteorites have been recovered from a series of soil depleted areas of New Mexico and West Texas. Most have been recovered from blowouts near Clovis in Roosevelt County (RC) on the high plains of New Mexico. The mineralogical and petrologic Al effects of weathering upon these samples have been studied previously and show that the degree of weathering is largely depend ant upon the terrestrial residence time. The study was undertaken to determine the effects of prolonged exposure to the soil and climate of Roosevelt County upon ordinary chondrites in the hope that this will enable a better understanding of the problems associated with the collection of meteoritic falls. A suite of ten grade 4 to 6 H, L, and LL ordinary chondrites were analyzed for carbon content and isotopic composition.

  17. Carbon in weathered ordinary chondrites from Roosevelt County

    NASA Technical Reports Server (NTRS)

    Ash, R. D.; Pillinger, C. T.

    1993-01-01

    A suite of Roosevelt County ordinary chondrites of known terrestrial age have been analyzed for carbon content and isotopic composition. Initial results indicate that significant carbon contamination is evident only in samples with a terrestrial age greater than 40 ka. These samples are of weathering grade D and E and contain three times more carbon than the less weathered samples. The soil in which they were preserved has a carbon content of ca. 1.5 percent. Over 200 meteorites have been recovered from a series of soil depleted areas of New Mexico and West Texas. Most have been recovered from blowouts near Clovis in Roosevelt County (RC) on the high plains of New Mexico. The mineralogical and petrologic Al effects of weathering upon these samples have been studied previously and show that the degree of weathering is largely depend ant upon the terrestrial residence time. The study was undertaken to determine the effects of prolonged exposure to the soil and climate of Roosevelt County upon ordinary chondrites in the hope that this will enable a better understanding of the problems associated with the collection of meteoritic falls. A suite of ten grade 4 to 6 H, L, and LL ordinary chondrites were analyzed for carbon content and isotopic composition.

  18. Topographic imprint on chemical weathering in deeply weathered soil-mantled landscapes (southern Brazil)

    NASA Astrophysics Data System (ADS)

    Vanacker, Veerle; Schoonejans, Jerome; Ameijeiras-Marino, Yolanda; Opfergelt, Sophie; Minella, Jean

    2017-04-01

    The regolith mantle is defined as the thin layer of unconsolidated material overlaying bedrock that contributes to shape the Earth's surface. The development of the regolith mantle in a landscape is the result of in-situ weathering, atmospheric input and downhill transport of weathering products. Bedrock weathering - the physical and chemical transformations of rock to soil - contributes to the vertical development of the regolith layer through downward propagation of the weathering front. Lateral transport of soil particles, aggregates and solutes by diffusive and concentrated particle and solute fluxes result in lateral redistribution of weathering products over the hillslope. In this study, we aim to expand the empirical basis on long-term soil evolution at the landscape scale through a detailed study of soil weathering in subtropical soils. Spatial variability in chemical mass fluxes and weathering intensity were studied along two toposequences with similar climate, lithology and vegetation but different slope morphology. This allowed us to isolate the topographic imprint on chemical weathering and soil development. The toposequences have convexo-concave slope morphology, and eight regolith profiles were analysed involving the flat upslope, steep midslope and flat toeslope part. Our data show a clear topographic imprint on soil development. Along hillslope, the chemical weathering intensity of the regolith profiles increases with distance from the crest. In contrast to the upslope positions, the soils in the basal concavities develop on in-situ and transported regolith. While the chemical weathering extent on the slope convexities (the upslope profiles) is similar for the steep and gentle toposequence, there is a clear difference in the rate of increase of the chemical weathering extent with distance from the crest. The increase of chemical weathering extent along hillslope is highest for the steep toposequence, suggesting that topography enhances soil particle

  19. Weather types and strokes in the Augsburg region (Southern Germany)

    NASA Astrophysics Data System (ADS)

    Beck, Christoph; Ertl, Michael; Giemsa, Esther; Jacobeit, Jucundus; Naumann, Markus; Seubert, Stefanie

    2017-04-01

    Strokes are one of the leading causes of morbidity and mortality worldwide and the main reason for longterm care dependency in Germany. Concerning the economical impact on patients and healthcare systems it is of particular importance to prevent this disease as well as to improve the outcome of the affected persons. Beside the primary well-known risk factors like hypertension, cigarette smoking, physical inactivity and others, also weather seems to have pronounced influence on the occurrence and frequency of strokes. Previous studies most often focused on effects of singular meteorological variables like ambient air temperature, air pressure or humidity. An advanced approach is to link the entire suite of daily weather elements classified to air mass- or weather types to cerebrovascular morbidity or mortality. In a joint pilot study bringing together climatologists, environmental scientists and physicians from the University of Augsburg and the clinical centre Augsburg, we analysed relationships between singular meteorological parameters as well as combined weather effects (e.g. weather types) and strokes in the urban area of Augsburg and the surrounding rural region. A total of 17.501 stroke admissions to Neurological Clinic and Clinical Neurophysiology at Klinikum Augsburg between 2006 and 2015 are classified to either "ischaemic" (16.354) or "haemorrhagic" (1.147) subtype according to etiology (based on the International Classification of Diseases - 10th Revision). Spearman correlations between daily frequencies of ischaemic and haemorrhagic strokes and singular atmospheric parameters (T, Tmin, Tmax, air pressure, humidity etc.) measured at the DWD (German weather service) meteorological station at Augsburg Muehlhausen are rather low. However, higher correlations are achieved when considering sub-samples of "homogenous weather conditions" derived from synoptic circulation classifications: e.g. within almost all of 10 types arising from a classification of

  20. Combined effect of carbonate and biotite dissolution in landslides biases silicate weathering proxies

    NASA Astrophysics Data System (ADS)

    Emberson, R.; Galy, A.; Hovius, N.

    2017-09-01

    Long-term estimates of the dissolution of silicate rock are generally derived from a range of isotopic proxies, such as the radiogenic strontium isotope ratio (87Sr/86Sr), which are preserved in sediment archives. For these systems to fairly represent silicate weathering, the changes in isotopic ratios in terrestrial surface waters should correspond to changes in the overall silicate dissolution. This assumes that the silicate mineral phases that act as sources of a given isotope dissolve at a rate that is proportional to the overall silicate weathering. Bedrock landsliding exhumes large quantities of fresh rock for weathering in transient storage, and rapid weathering in these deposits is controlled primarily by dissolution of the most reactive phases. In this study, we test the hypothesis that preferential weathering of these labile minerals can decouple the dissolution of strontium sources from the actual silicate weathering rates in the rapidly eroding Western Southern Alps (WSA) of New Zealand. We find that rapid dissolution of relatively radiogenic calcite and biotite in landslides leads to high local fluxes in strontium with isotopic ratios that offer no clear discrimination between sources. These higher fluxes of radiogenic strontium are in contrast to silicate weathering rates in landslides that are not systematically elevated. On a mountain belt scale, radiogenic strontium fluxes are not coupled to volumes of recent landslides in large (>100 km2) catchments, but silicate weathering fluxes are. Such decoupling is likely due first to the broad variability in the strontium content of carbonate minerals, and second to the combination of radiogenic strontium released from both biotite and carbonate in recent landslides. This study supports previous work suggesting the limited utility of strontium isotopes as a system to study silicate weathering in the WSA. Crucially however, in settings where bedrock landsliding is a dominant erosive process there is

  1. Rock weathering on the eastern mountains of southern Africa: Review and insights from case studies

    NASA Astrophysics Data System (ADS)

    Sumner, P. D.; Hall, K. J.; van Rooy, J. L.; Meiklejohn, K. I.

    2009-12-01

    The mountains in the eastern region of southern Africa are of significant regional importance, providing for a diverse range of land use including conservation, tourism and subsistence agriculture. The higher regions are comprised of flood basalts and are immediately underlain by predominantly aeolian-origin sandstones. Our understanding of the weathering of these basalts and sandstones is reviewed here, with particular focus on the insights gained from the Lesotho Highlands Water Project and an ongoing study into the deterioration of rock art. While the chemical weathering attributes of the basalts have been substantially investigated, it is evident that the environmental surface conditions of rock moisture and temperature, as affecting weathering processes, remain largely unknown. Within the sandstones, studies pertaining to rock art deterioration present insights into the potential surface weathering processes and highlight the need for detailed field monitoring. Outside of these site-specific studies, however, little is understood of how weathering impacts on landscape development; notably absent, are detail on weathering rates, and potential effects of biological weathering. Some palaeoenvironmental inferences have also been made from weathering products, both within the basalts and the sandstones, but aspects of these remain controversial and further detailed research can still be undertaken.

  2. Accelerating the carbon cycle: the ethics of enhanced weathering.

    PubMed

    Lawford-Smith, H; Currie, A

    2017-04-01

    Enhanced weathering, in comparison to other geoengineering measures, creates the possibility of a reduced cost, reduced impact way of decreasing atmospheric carbon, with positive knock-on effects such as decreased oceanic acidity. We argue that ethical concerns have a place alongside empirical, political and social factors as we consider how to best respond to the critical challenge that anthropogenic climate change poses. We review these concerns, considering the ethical issues that arise (or would arise) in the large-scale deployment of enhanced weathering. We discuss post-implementation scenarios, failures of collective action, the distribution of risk and externalities and redress for damage. We also discuss issues surrounding 'dirty hands' (taking conventionally immoral action to avoid having to take action that is even worse), whether enhanced weathering research might present a moral hazard, the importance of international governance and the notion that the implementation of large-scale enhanced weathering would reveal problematic hubris. Ethics and scientific research interrelate in complex ways: some ethical considerations caution against research and implementation, while others encourage them. Indeed, the ethical perspective encourages us to think more carefully about how, and what types of, geoengineering should be researched and implemented. © 2017 The Author(s).

  3. Carbon Dioxide Effects on Soil-Chemical Weathering: Laboratory Column Studies with Saprolite Materials

    NASA Astrophysics Data System (ADS)

    Oh, N.; Richter, D. D.

    2001-12-01

    Column leaching experiments have evaluated effects of sulfuric, nitric, and hydrochloric acids on chemical weathering in soils and rocks. In contrast, research to investigate effects of carbonic acid on chemical weathering is notably absent. Given that rising aboveground CO2 may increase photosynthesis and may enhance soil respiration, elevated soil CO2 and carbonic acid may enhance cation leaching via a combination of cation exchange and mineral dissolution. Column leaching studies were conducted using deep soil materials of the southern Piedmont (Enon, Tarrus, and Cecil series soils). Deionized water equilibrated with CO2 (at 1, 10, and 100%) was used as eluent and soluble products from exchangeable and mineral-bound sources were estimated. Results demonstrated that elevated CO2 accelerated cation release by both cation exchange and mineral dissolution. Highest cation release rates were from the Enon C horizon, a smectite-rich material from diabase with 23cmol(+)/kg ECEC and 98% base saturation. Lowest releases were from the Cecil Cr horizon, a kaolin-micaceous material derived from granitic gneiss with 1.2cmol(+)/kg ECEC and 40% B.S. Cation exchange was the predominant source of cations released, although mineral dissolution occurred in all three soils in response to elevated CO2. Remarkably, upto 35% of the cations released by the Cecil Cr horizon was attributed to weathering dissolution, probably from micaceous minerals.

  4. Weather.

    ERIC Educational Resources Information Center

    Ruth, Amy, Ed.

    1996-01-01

    This theme issue of "The Goldfinch" focuses on weather in Iowa and weather lore. The bulletin contains historical articles, fiction, activities, and maps. The table of contents lists: (1) "Wild Rosie's Map"; (2) "History Mystery"; (3) "Iowa's Weather History"; (4) "Weather Wonders"; (6)…

  5. Estimation of the annual yield of organic carbon released from carbonates and shales by chemical weathering

    NASA Astrophysics Data System (ADS)

    Di-Giovanni, Christian; Disnar, Jean Robert; Macaire, Jean Jacques

    2002-04-01

    The aim of this paper is to propose an initial estimation of the annual organic matter yield induced by chemical weathering of carbonates and shales, considering their global surface at outcrop and their organic matter content. The calculation also uses data on river fluxes resulting from carbonate rocks and shales weathering in major world watersheds, published by numerous authors. The results obtained from the studied watersheds have then been extrapolated to a global scale. Despite rather large uncertainty to such an approach, the calculated value of ca. 0.1 Gt implies that the annual organic carbon yield related to carbonates and shales chemical weathering might be a non-negligible component of the global carbon cycle. The individual contributions of different watersheds necessarily depend on the organic matter content of altered rocks. They are also obviously controlled by climatic parameters. The calculated yields do not constitute a direct supply to soils and rivers because of mineralisation when organic carbon is brought in contact with the atmosphere. Even so, the release of fossil organic matter would have implications for the global carbon cycle through the efficiency of the global chemical weathering as a carbon sink. Whatever the chosen hypothesis, the results of this study suggest that the recycled organic yield is a neglected component in the global organic carbon cycle assessment. Because it exists and, in addition, because it might represent a non-negligible carbon pool, fossil organic carbon deserves to be taken into account for a better evaluation of the organic stocks in soils and rivers presently only based on climatic data and current vegetal production.

  6. Bone weathering patterns of metatarsal v. femur and the postmortem interval in Southern Ontario.

    PubMed

    Janjua, Martyna A; Rogers, Tracy L

    2008-06-10

    Twenty-five defleshed pig femora and 25 metatarsals were placed outdoors and observed over 291 days to establish: (1) bone weathering patterns for use in estimating time since death in Southern Ontario and (2) whether larger (femora) or smaller (metatarsals) bones provide a better indicator of time since death. Pig hind limbs were observed to determine a timeline for decomposition of soft tissues during the fall and winter. Ambient air temperature, humidity, precipitation, sunlight, soil pH, and freezing and thawing were considered as factors affecting the breakdown of bone. Weathering patterns were observed based on the extent of bleaching, amount of periosteum and soft tissues present, as well as the appearance of greasiness, cracking and flaking of cortical bone. Both entomological activity and climatic conditions affected soft tissue decomposition. Animal activity affected both the process of bone weathering and soft tissue decomposition, causing variability in sample decomposition and bone breakdown. The variation in microenvironment, partially caused by soil composition, introduced variability in bone weathering rates. Four bone weathering stages were established based on patterns observed. Femora proved to be more resilient and showed more degrees of change due to weathering, thus proving to be a better indicator of time since death than metatarsals.

  7. Traveling Weather Disturbances in Mars Southern Extratropics: Sway of the Great Impact Basins

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.

    2016-01-01

    As on Earth, between late autumn and early spring on Mars middle and high latitudes within its atmosphere support strong mean thermal contrasts between the equator and poles (i.e. "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that this strong baroclinicity supports vigorous, large-scale eastward traveling weather systems (i.e. transient synoptic-period waves). Within a rapidly rotating, differentially heated, shallow atmosphere such as on Earth and Mars, such large-scale, extratropical weather disturbances are critical components of the global circulation. These wave-like disturbances act as agents in the transport of heat and momentum, and moreover generalized tracer quantities (e.g., atmospheric dust, water vapor and water-ice clouds) between low and high latitudes of the planet. The character of large-scale, traveling extratropical synoptic-period disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a high-resolution Mars global climate model (Mars GCM). This global circulation model imposes interactively lifted (and radiatively active) dust based on a threshold value of the instantaneous surface stress. Compared to observations, the model exhibits a reasonable "dust cycle" (i.e. globally averaged, a more dusty atmosphere during southern spring and summer occurs). In contrast to their northern-hemisphere counterparts, southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense synoptically. Influences of the zonally asymmetric (i.e. east-west varying) topography on southern large-scale weather disturbances are examined. Simulations that adapt Mars' full topography compared to simulations that utilize synthetic topographies emulating essential large-scale features of the southern middle latitudes indicate that Mars

  8. Traveling Weather Disturbances in Mars' Southern Extratropics: Sway of the Great Impact Basins

    NASA Astrophysics Data System (ADS)

    Hollingsworth, Jeffery L.

    2016-04-01

    As on Earth, between late autumn and early spring on Mars middle and high latitudes within its atmosphere support strong mean thermal contrasts between the equator and poles (i.e., "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that this strong baroclinicity supports vigorous, large-scale eastward traveling weather systems (i.e., transient synoptic-period waves). Within a rapidly rotating, differentially heated, shallow atmosphere such as on Earth and Mars, such large-scale, extratropical weather disturbances are critical components of the global circulation. These wave-like disturbances act as agents in the transport of heat and momentum, and moreover generalized tracer quantities (e.g., atmospheric dust, water vapor and water-ice clouds) between low and high latitudes of the planet. The character of large-scale, traveling extratropical synoptic-period disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a high-resolution Mars global climate model (Mars GCM). This global circulation model imposes interactively lifted (and radiatively active) dust based on a threshold value of the instantaneous surface stress. Compared to observations, the model exhibits a reasonable "dust cycle" (i.e., globally averaged, a more dusty atmosphere during southern spring and summer occurs). In contrast to their northern-hemisphere counterparts, southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense synoptically. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather disturbances are examined. Simulations that adapt Mars' full topography compared to simulations that utilize synthetic topographies emulating essential large-scale features of the southern middle latitudes indicate that Mars

  9. The USDA Southern Plains Climate Hub: Regional agricultural management in the context of weather and climate variability and change

    USDA-ARS?s Scientific Manuscript database

    In the Southern Great Plains of the United States, extremes of weather and climate are the norm. Farmers, ranchers, and foresters rely upon timely and authoritative data and information when making management decisions that are weather- and climate-dependent. In response to the needs of these agricu...

  10. Soil Organic Carbon Loss: An Overlooked Factor in the Carbon Sequestration Potential of Enhanced Mineral Weathering

    NASA Astrophysics Data System (ADS)

    Dietzen, Christiana; Harrison, Robert

    2016-04-01

    Weathering of silicate minerals regulates the global carbon cycle on geologic timescales. Several authors have proposed that applying finely ground silicate minerals to soils, where organic acids would enhance the rate of weathering, could increase carbon uptake and mitigate anthropogenic CO2 emissions. Silicate minerals such as olivine could replace lime, which is commonly used to remediate soil acidification, thereby sequestering CO2 while achieving the same increase in soil pH. However, the effect of adding this material on soil organic matter, the largest terrestrial pool of carbon, has yet to be considered. Microbial biomass and respiration have been observed to increase with decreasing acidity, but it is unclear how long the effect lasts. If the addition of silicate minerals promotes the loss of soil organic carbon through decomposition, it could significantly reduce the efficiency of this process or even create a net carbon source. However, it is possible that this initial flush of microbial activity may be compensated for by additional organic matter inputs to soil pools due to increases in plant productivity under less acidic conditions. This study aimed to examine the effects of olivine amendments on soil CO2 flux. A liming treatment representative of typical agricultural practices was also included for comparison. Samples from two highly acidic soils were split into groups amended with olivine or lime and a control group. These samples were incubated at 22°C and constant soil moisture in jars with airtight septa lids. Gas samples were extracted periodically over the course of 2 months and change in headspace CO2 concentration was determined. The effects of enhanced mineral weathering on soil organic matter have yet to be addressed by those promoting this method of carbon sequestration. This project provides the first data on the potential effects of enhanced mineral weathering in the soil environment on soil organic carbon pools.

  11. Synoptic weather types and long-range transport patterns for ozone precursors during high-ozone events in southern Sweden.

    PubMed

    Tang, Lin; Karlsson, Per Erik; Gu, Yongfeng; Chen, Deliang; Grennfelt, Peringe

    2009-12-01

    We studied long-range transport patterns and related weather types in relation to high-ozone events in southern Sweden. The aim was to deepen the understanding of the relationship between Lamb-Jenkinson weather types and surface ozone concentration variation, thus widening the application of the weather type analysis of air quality at 4 sites in this region. The long-range transport patterns associated with high-ozone events were classified into trajectories from Western Europe, Eastern Europe, and in the vicinity of southern Sweden (VIC). The VIC type, characterized by short and whirling curves, represented more than 40% of the high-ozone events at the studied rural sites. More than half of the high-ozone events occurred under high-pressure conditions, belonging to weather type A (anticyclones). The high correlation coefficient between annual counts of weather type A and those of long-range transport pattern VIC confirmed the strong link between stagnant weather conditions and high-ozone events, especially during the summer. Furthermore, a strong linear anticorrelation was detected between high-ozone events and annual counts of weather type C (cyclones) during the summer. This relationship implies that the frequency of weather type C is a useful indicator for low risk of summertime high-ozone events in southern Sweden. Moreover, the relationship between the weather type and high ozone risk may be useful in examining the potential effect of climate change on the regional air quality.

  12. Weathering Of Plutonic Rocks: A Case Study From Calabria, Southern Italy

    NASA Astrophysics Data System (ADS)

    Le Pera, E.; Viola, S.; Ietto, F.

    2003-04-01

    The effect of chemical and mechanical weathering on the mineralogy and microfabric of Paleozoic tonalite of the Serre massif, in southern Calabria, has been recognised from the analysis of samples have been taken from cores and field exposure. The original rock contains euhedral zoned plagioclase (andesine-oligoclase), ortoclase, anhedral patches of quartz, green hornblende and biotite, and opaques, apatite and sphene as accessory minerals. Complete weathering profiles of the Serre tonalite are often up to 30 m deep. Petrography of buried and exposed lithology indicates that the transition from the parent rock to saprolite is consistent with the process of grussification and arenisation, similar to granitoid rock weathering in northern Calabria, and it is marked by both chemical alteration and granular disintegration. The mineralogical changes identified suggest in situ weathering was selective with biotite, plagioclase feldspar and their secondary deuteric products altering before K-feldspar and quartz. Quartz crystals are affected by microcracks showing some fissures. Biotite in various degrees of chloritization, or replaced by iron oxides, along cleavage planes, has been observed. Feldspars have an opaque appearance, due to a microcrystalline secondary product, that is probably an aggregate of clayey mineral replacement during weathering. Evidence of chemical dissolution (etch pits) on plagioclase has been identified. Green hornblende alters to ferruginous products growing as linings along mineral cleavage. The loss of the original structure of the rock and the progress of weathering have been characterised through calculation of the Decomposition Index (X_d), indicating the extent to which the rock microfabric and composition are affected by weathering, leading to soil formation. X_d values in the tonalite from the Serre massif range from 0.1 to 0.75, with increasing decomposition. X_d<0.5 samples exceed those having X_d>0.5. These two microfabric types can be

  13. The impact of future changes in weather patterns on extreme sea levels over southern Australia

    NASA Astrophysics Data System (ADS)

    Colberg, Frank; McInnes, Kathleen L.

    This study first compares two methods by which the global, variable resolution Cubic Conformal Atmospheric Model (CCAM) is forced by reanalysis over Australia. The methods are the spectral nudging and bias-corrected sea surface temperature (SST) forcing. Surface winds and sea level pressure are compared since these influence coastal sea levels. SST forcing was found to better preserve the mean and standard deviation of these quantities. Second, a hydrodynamic model is used to model sea levels over southern Australia over 1980-1999 and 2080-2099 to investigate how changes in weather patterns affect extreme sea levels. Forcing from one Global Climate Model (GCM) and two CCAM simulations in which CCAM was used to downscale two GCMs over Australia with bias-corrected SST forcing (including the GCM considered in this study) were used. While there are differences in the spatial patterns of change between seasons over the modeled coastline between the three models, extreme sea levels were mostly lower in the future period over the southern mainland coastline from autumn to spring due to reduced westerlies in the climate models. The sea level changes around Tasmania varied from positive to negative depending on the model and season. The projected extreme sea level changes were within 10 cm of current climate values. This suggests that over southern Australia extreme sea level changes will be dominated by changes in mean sea level due to thermal expansion and ice sheet and glacier melt rather than changes in weather patterns.

  14. Southern giant Petrel Macronectes giganteus nest attendance patterns under extreme weather conditions.

    PubMed

    Schulz, Uwe Horst; Krüger, Lucas; Petry, Maria Virginia

    2014-08-01

    Differences in nest attendance between genders in seabirds may be related to morphological differences. Southern giant petrel is a dimorphic species with gender-specific foraging behavior. The objective of this study was to investigate sex-related differences in nest attendance during the breeding period of southern giant petrels by presence/absence patterns of both sexes during incubation and compare use of the colony after nest failure. Fourteen birds were tagged with digitally coded radio-transmitters in a colony at Elephant Island, Antarctica, in the beginning of 2009/2010 breeding season. Females were present during 18 periods (min. 3 days, max. 9 days) and males only in five periods (min. 2 days, max. 13 days). The difference in mean number of radio signals per day between females (4330; s.e. 313.5) and males (2691; s.e. 248.6) was highly significant (t = 4.3; d.f. = 199; P < 0.001; Fig. 4 ). As consequence of the severe weather conditions that year, all tagged birds failed to reproduce. After abandonment of the nests, the presence of both genders decreased drastically, although the tagged individuals stayed in the area. Under severe weather conditions female Southern Giant Petrels continue breeding while males abandon the nest earlier.

  15. Paleopedological reconstruction and quantitative analysis of weathering processes in the Southern Piedmont Province

    SciTech Connect

    Feldman, S.B.; Zelazny, L.W. ); Pavich, M.J. )

    1992-01-01

    Soils and paleosols are commonly used to estimate ages of deposits and geomorphic surfaces, and to infer paleoenvironmental conditions during pedogenesis. Accurate interpretation of these and other parameters is currently limited, however, by considerable uncertainty in many fundamental areas of soils-geomorphic research. These include: (1) lack of accurate estimates of weathering rates for reliably-dated surfaces, (2) inability to quantitatively differentiate between the complex effects of climate vs. geomorphic age on weathering rates, processes, and pedogenic properties, and (3) difficulty in assessing which soil properties persist, alter, or become obliterated in the weathering environment as conditions change. In this paper, the authors discuss a method for assessing, on a regional basis, the quantitative relationships between climate, time, and weathering processes along a soil climosequence in the Southern Piedmont Province. Their approach involves sampling exclusively in areas of granitic plutons that exhibit a high degree of homogeneity with regard to total Fe content, bulk mineralogy, and absence of secondary phyllosilicates or sesquioxides. Independent age control is being established by [sup 10]Be dating, and analytical techniques include, in part, (1) geochemical speciation of soil solution and mineral equilibrium determination, (2) elemental analysis and mass balance calculations of elemental flux during pedogenesis, and (3) detailed analysis of Fe-oxide crystallinity, structure, and Al substitution using selective dissolution analysis, and both X-ray and differential X-ray diffraction.

  16. Stable carbon isotope evidence for nitrogenous fertilizer impact on carbonate weathering in a small agricultural watershed.

    PubMed

    Brunet, F; Potot, C; Probst, A; Probst, J-L

    2011-10-15

    The isotopic signature of Dissolved Inorganic Carbon (DIC), δ(13)C(DIC), has been investigated in the surface waters of a small agricultural catchment on calcareous substratum, Montoussé, located at Auradé (south-west France). The Montoussé catchment is subjected to intense farming (wheat/sunflower rotation) and a moderated application of nitrogenous fertilizers. During the nitrification of the NH(4)(+), supplied by fertilization, nitrate and H(+) ions are produced in the soil. This anthropogenic acidity is combined with the natural acidity due to carbonic acid in weathering processes. From an isotopic point of view, with 'natural weathering', using carbonic acid, δ(13)C(DIC) is intermediate between the δ(13)C of soil CO(2) produced by organic matter oxidation and that of the carbonate rocks, while it has the same value as the carbonates when carbonic acid is substituted by another acid like nitric acid derived from nitrogen fertilizer. The δ(13)C(DIC) values range from -17.1‰ to -10.7‰ in Montoussé stream waters. We also measured the δ(13)C of calcareous molassic deposits (average -7.9‰) and of soil organic carbon (between -24.1‰ and -26‰) to identify the different sources of DIC and to estimate their contribution. The δ(13) C(DIC) value indicates that weathering largely follows the carbonic acid pathway at the springs (sources of the stream). At the outlet of the basin, H(+) ions, produced during the nitrification of N-fertilizer, also contribute to weathering, especially during flood events. This result is illustrated by the relationship between δ(13)C(DIC) and the molar ratio NO(3)(-)/(Ca(2+) + Mg(2+)). Consequently, when the contribution of nitrate increases, the δ(13)C(DIC) increases towards the calcareous end-member. This new isotopic result provides evidence for the direct influence of nitrogen fertilizer inputs on weathering, CO(2) consumption and base cation leaching and confirms previous results obtained using the chemistry of the

  17. The reinvigoration of the Southern Ocean carbon sink.

    PubMed

    Landschützer, Peter; Gruber, Nicolas; Haumann, F Alexander; Rödenbeck, Christian; Bakker, Dorothee C E; van Heuven, Steven; Hoppema, Mario; Metzl, Nicolas; Sweeney, Colm; Takahashi, Taro; Tilbrook, Bronte; Wanninkhof, Rik

    2015-09-11

    Several studies have suggested that the carbon sink in the Southern Ocean-the ocean's strongest region for the uptake of anthropogenic CO2 -has weakened in recent decades. We demonstrated, on the basis of multidecadal analyses of surface ocean CO2 observations, that this weakening trend stopped around 2002, and by 2012, the Southern Ocean had regained its expected strength based on the growth of atmospheric CO2. All three Southern Ocean sectors have contributed to this reinvigoration of the carbon sink, yet differences in the processes between sectors exist, related to a tendency toward a zonally more asymmetric atmospheric circulation. The large decadal variations in the Southern Ocean carbon sink suggest a rather dynamic ocean carbon cycle that varies more in time than previously recognized. Copyright © 2015, American Association for the Advancement of Science.

  18. Critical zone weathering in the southern Sierra Nevada and Laramie Mountains imaged by seismic tomography

    NASA Astrophysics Data System (ADS)

    Hayes, J. L.; Holbrook, W. S.; Riebe, C. S.

    2011-12-01

    Near-surface variations in seismic velocity reflect differences in physical properties such as density and porosity, which in turn reflect differences in alteration of parent material by exposure to water and biologic activity. Here we present tomographic analysis of the extent of weathering from seismic refraction experiments at two areas underlain by granite: the Southern Sierra Critical Zone Observatory (SSCZO) in the fall of 2010 & 2011 and the Laramie Mountains in the spring of 2010. A 48-channel geophone array and hammer source was deployed in both surveys. In both areas seismic velocities suggest that weathering has progressed to depths of 10 m or more. When coupled with geochemical measurements of the degree of regolith weathering, these depths imply that the potential for subsurface water storage in regolith may be a larger component of the water budget than previously thought at the SSCZO. The velocity of granite bedrock was determined independently in both studies to be ~4 km/s by seismic experiments directly on outcropping granite. Two other ranges of seismic velocities seem consistent between the studies: a saprolite layer of chemically altered but still intact rock (2-4 km/s) and a regolith layer more altered than the underlying saprolite layer (<2 km/s). Using these parameters we tested hypotheses in two different granite-weathering environments. In the SSCZO a velocity-depth profile that crosses a water-saturated meadow and an adjoining forest reveal relatively low gradients in the first ten meters beneath the forest (0.75 km/s per 10 m) and higher gradients beneath the meadow (3 km/s per 10 m). From these observations, we hypothesize that the saturated meadow may provide a reducing environment that inhibits chemical weathering relative to better-drained, more oxidizing conditions in the forest. In the 1.4 Ga Sherman batholith of the Laramie Mountains we observe isolated outcrops of Lincoln Granite within the Sherman Granite. Two 0.5 km profiles

  19. El Niño-Southern Oscillation, local weather and occurrences of dengue virus serotypes

    NASA Astrophysics Data System (ADS)

    Huang, Xiaodong; Clements, Archie C. A.; Williams, Gail; Devine, Gregor; Tong, Shilu; Hu, Wenbiao

    2015-11-01

    Severe dengue fever is usually associated with secondary infection by a dengue virus (DENV) serotype (1 to 4) that is different to the serotype of the primary infection. Dengue outbreaks only occur following importations of DENV in Cairns, Australia. However, the majority of imported cases do not result in autochthonous transmission in Cairns. Although DENV transmission is strongly associated with the El Niño-Southern Oscillation (ENSO) climate cycle and local weather conditions, the frequency and potential risk factors of infections with the different DENV serotypes, including whether or not they differ, is unknown. This study used a classification tree model to identify the hierarchical interactions between Southern Oscillation Index (SOI), local weather factors, the presence of imported serotypes and the occurrence of the four autochthonous DENV serotypes from January 2000-December 2009 in Cairns. We found that the 12-week moving average of SOI and the 2-week moving average of maximum temperature were the most important factors influencing the variation in the weekly occurrence of the four DENV serotypes, the likelihoods of the occurrence of the four DENV serotypes may be unequal under the same environmental conditions, and occurrence may be influenced by changes in global and local environmental conditions in Cairns.

  20. El Niño-Southern Oscillation, local weather and occurrences of dengue virus serotypes.

    PubMed

    Huang, Xiaodong; Clements, Archie C A; Williams, Gail; Devine, Gregor; Tong, Shilu; Hu, Wenbiao

    2015-11-19

    Severe dengue fever is usually associated with secondary infection by a dengue virus (DENV) serotype (1 to 4) that is different to the serotype of the primary infection. Dengue outbreaks only occur following importations of DENV in Cairns, Australia. However, the majority of imported cases do not result in autochthonous transmission in Cairns. Although DENV transmission is strongly associated with the El Niño-Southern Oscillation (ENSO) climate cycle and local weather conditions, the frequency and potential risk factors of infections with the different DENV serotypes, including whether or not they differ, is unknown. This study used a classification tree model to identify the hierarchical interactions between Southern Oscillation Index (SOI), local weather factors, the presence of imported serotypes and the occurrence of the four autochthonous DENV serotypes from January 2000-December 2009 in Cairns. We found that the 12-week moving average of SOI and the 2-week moving average of maximum temperature were the most important factors influencing the variation in the weekly occurrence of the four DENV serotypes, the likelihoods of the occurrence of the four DENV serotypes may be unequal under the same environmental conditions, and occurrence may be influenced by changes in global and local environmental conditions in Cairns.

  1. Assessment of marine weather forecasts over the Indian sector of Southern Ocean

    NASA Astrophysics Data System (ADS)

    Gera, Anitha; Mahapatra, D. K.; Sharma, Kuldeep; Prakash, Satya; Mitra, A. K.; Iyengar, G. R.; Rajagopal, E. N.; Anilkumar, N.

    2017-09-01

    The Southern Ocean (SO) is one of the important regions where significant processes and feedbacks of the Earth's climate take place. Expeditions to the SO provide useful data for improving global weather/climate simulations and understanding many processes. Some of the uncertainties in these weather/climate models arise during the first few days of simulation/forecast and do not grow much further. NCMRWF issued real-time five day weather forecasts of mean sea level pressure, surface winds, winds at 500 hPa & 850 hPa and rainfall, daily to NCAOR to provide guidance for their expedition to Indian sector of SO during the austral summer of 2014-2015. Evaluation of the skill of these forecasts indicates possible error growth in the atmospheric model at shorter time scales. The error growth is assessed using the model analysis/reanalysis, satellite data and observations made during the expedition. The observed variability of sub-seasonal rainfall associated with mid-latitude systems is seen to exhibit eastward propagations and are well reproduced in the model forecasts. All cyclonic disturbances including the sub-polar lows and tropical cyclones that occurred during this period were well captured in the model forecasts. Overall, this model performs reasonably well over the Indian sector of the SO in medium range time scale.

  2. Enhanced carbonate and silicate weathering accelerates recovery from fossil fuel CO2 perturbations

    NASA Astrophysics Data System (ADS)

    Lenton, Timothy M.; Britton, Clare

    2006-09-01

    Increasing atmospheric CO2 and surface temperatures should increase carbonate and silicate weathering rates, directly via warming, and indirectly via the CO2 fertilization effect enhancing plant productivity. Enhanced weathering should in turn increase alkalinity input to the ocean and accelerate long-term CO2 uptake. We added silicate and carbonate weathering and carbonate sediments to an existing global carbon cycle and surface temperature model and subjected it to a range of long-term fossil fuel emissions scenarios, spanning 1100-15,000 GtC in total. Emissions of ≥7350 GtC dissolve all carbonate sediments, and enhanced carbonate and silicate weathering accelerate subsequent CO2 removal from the atmosphere by up to a factor of 4. For 1100-4000 GtC emissions, enhanced weathering accelerates CO2 removal by a factor of 1.5-2.5. However, it takes >1 Myr for silicate weathering to stabilize atmospheric CO2. If land use tends to suppress vegetation and weathering rates on this timescale, then CO2 will stabilize above preindustrial levels.

  3. Chemical weathering of silicate rocks as a function of elevation in the southern Swiss Alps

    NASA Astrophysics Data System (ADS)

    Drever, James I.; Zobrist, Jürg

    1992-08-01

    Surface water and soil samples were collected from a series of small catchments on granitic gneiss in the Canton of Ticino in southern Switzerland. Elevations of the sampling points ranged from 220 to 2400 m; vegetation varied correspondingly from deciduous forest through coniferous forest to alpine pasture and essentially unvegetated rock and talus. Annual precipitation averaged 1.9 to 2.4 m. The concentrations of the major cations and silica in surface waters decreased more or less exponentially with elevation. The cationic denudation rate decreased from about 500 meq/m 2 · y at the lower elevations to about 20 meq/m 2 · y at the highest. Alkalinity decreased from 250 to about -7 μeq/1. Although total concentrations decreased with elevation, there were no clear systematic trends in the ratios of the concentrations of the major cations and silica. This suggests that the nature of the secondary minerals formed during weathering in the area does not change with elevation, despite great changes in soil type and environmental conditions. The clay mineralogy of the soils is dominated by unweathered and slightly weathered bedrock minerals: mica and chlorite, hydrobiotite, and poorly characterized mixed-layer material. Small amounts of kaolinite and smectite were observed in a few samples, but there do not appear to be any systematic trends in clay mineralogy with elevation. Mass-balance arguments suggest that the major (in terms of solute generation) weathering product is either kaolinite or a mixture of A1(OH) 3 and 2:1 clays. The lack of dependence of weathering stoichiometry on elevation (a surrogate for several environmental variables) or solute concentrations perhaps reflects the importance of local relief, which did not vary systematically with elevation.

  4. Where is the carbon? Carbon sequestration potential from private forestland in the Southern United States

    Treesearch

    Christopher S. Galik; Brian C. Murray; D. Evan Mercer

    2013-01-01

    Uncertainty surrounding the future supply of timber in the southern United States prompted the question, “Where is all the wood?” (Cubbage et al. 1995). We ask a similar question about the potential of southern forests to mitigate greenhouse gas (GHG) emissions by sequestering carbon. Because significant carbon sequestration potential occurs on individual nonindustrial...

  5. Hydrologic regulation of chemical weathering and the geologic carbon cycle.

    PubMed

    Maher, K; Chamberlain, C P

    2014-03-28

    Earth's temperature is thought to be regulated by a negative feedback between atmospheric CO2 levels and chemical weathering of silicate rocks that operates over million-year time scales. To explain variations in the strength of the weathering feedback, we present a model for silicate weathering that regulates climatic and tectonic forcing through hydrologic processes and imposes a thermodynamic limit on weathering fluxes, based on the physical and chemical properties of river basins. Climate regulation by silicate weathering is thus strongest when global topography is elevated, similar to the situation today, and lowest when global topography is more subdued, allowing planetary temperatures to vary depending on the global distribution of topography and mountain belts, even in the absence of appreciable changes in CO2 degassing rates.

  6. Sensitivity of chemical weathering and dissolved carbon dynamics to hydrological conditions in a typical karst river.

    PubMed

    Zhong, Jun; Li, Si-Liang; Tao, Faxiang; Yue, Fujun; Liu, Cong-Qiang

    2017-02-21

    To better understand the mechanisms that hydrological conditions control chemical weathering and carbon dynamics in the large rivers, we investigated hydrochemistry and carbon isotopic compositions of dissolved inorganic carbon (DIC) based on high-frequency sampling in the Wujiang River draining the carbonate area in southwestern China. Concentrations of major dissolved solute do not strictly follow the dilution process with increasing discharge, and biogeochemical processes lead to variability in the concentration-discharge relationships. Temporal variations of dissolved solutes are closely related to weathering characteristics and hydrological conditions in the rainy seasons. The concentrations of dissolved carbon and the carbon isotopic compositions vary with discharge changes, suggesting that hydrological conditions and biogeochemical processes control dissolved carbon dynamics. Biological CO2 discharge and intense carbonate weathering by soil CO2 should be responsible for the carbon variability under various hydrological conditions during the high-flow season. The concentration of DICbio (DIC from biological sources) derived from a mixing model increases with increasing discharge, indicating that DICbio influx is the main driver of the chemostatic behaviors of riverine DIC in this typical karst river. The study highlights the sensitivity of chemical weathering and carbon dynamics to hydrological conditions in the riverine system.

  7. Sensitivity of chemical weathering and dissolved carbon dynamics to hydrological conditions in a typical karst river

    PubMed Central

    Zhong, Jun; Li, Si-liang; Tao, Faxiang; Yue, Fujun; Liu, Cong-Qiang

    2017-01-01

    To better understand the mechanisms that hydrological conditions control chemical weathering and carbon dynamics in the large rivers, we investigated hydrochemistry and carbon isotopic compositions of dissolved inorganic carbon (DIC) based on high-frequency sampling in the Wujiang River draining the carbonate area in southwestern China. Concentrations of major dissolved solute do not strictly follow the dilution process with increasing discharge, and biogeochemical processes lead to variability in the concentration-discharge relationships. Temporal variations of dissolved solutes are closely related to weathering characteristics and hydrological conditions in the rainy seasons. The concentrations of dissolved carbon and the carbon isotopic compositions vary with discharge changes, suggesting that hydrological conditions and biogeochemical processes control dissolved carbon dynamics. Biological CO2 discharge and intense carbonate weathering by soil CO2 should be responsible for the carbon variability under various hydrological conditions during the high-flow season. The concentration of DICbio (DIC from biological sources) derived from a mixing model increases with increasing discharge, indicating that DICbio influx is the main driver of the chemostatic behaviors of riverine DIC in this typical karst river. The study highlights the sensitivity of chemical weathering and carbon dynamics to hydrological conditions in the riverine system. PMID:28220859

  8. Sensitivity of chemical weathering and dissolved carbon dynamics to hydrological conditions in a typical karst river

    NASA Astrophysics Data System (ADS)

    Zhong, Jun; Li, Si-Liang; Tao, Faxiang; Yue, Fujun; Liu, Cong-Qiang

    2017-02-01

    To better understand the mechanisms that hydrological conditions control chemical weathering and carbon dynamics in the large rivers, we investigated hydrochemistry and carbon isotopic compositions of dissolved inorganic carbon (DIC) based on high-frequency sampling in the Wujiang River draining the carbonate area in southwestern China. Concentrations of major dissolved solute do not strictly follow the dilution process with increasing discharge, and biogeochemical processes lead to variability in the concentration-discharge relationships. Temporal variations of dissolved solutes are closely related to weathering characteristics and hydrological conditions in the rainy seasons. The concentrations of dissolved carbon and the carbon isotopic compositions vary with discharge changes, suggesting that hydrological conditions and biogeochemical processes control dissolved carbon dynamics. Biological CO2 discharge and intense carbonate weathering by soil CO2 should be responsible for the carbon variability under various hydrological conditions during the high-flow season. The concentration of DICbio (DIC from biological sources) derived from a mixing model increases with increasing discharge, indicating that DICbio influx is the main driver of the chemostatic behaviors of riverine DIC in this typical karst river. The study highlights the sensitivity of chemical weathering and carbon dynamics to hydrological conditions in the riverine system.

  9. Influence of Weather Variables and Plant Communities on Grasshopper Density in the Southern Pampas, Argentina

    PubMed Central

    de Wysiecki, María Laura; Arturi, Marcelo; Torrusio, Sandra; Cigliano, María Marta

    2011-01-01

    A study was conducted to evaluate the influence of weather (precipitation and temperature) and plant communities on grasshopper density over a 14-year period (1996–2009) in Benito Juárez County, Southern Pampas, Argentina. Total density strongly varied among plant communities. Highest values were registered in 2001 and 2003 in highly disturbed pastures and in 2002 and 2009 in halophilous grasslands. Native grasslands had the lowest density values. Seasonal precipitation and temperature had no significant effect on total grasshopper density. Dichroplus elongatus (Giglio-Tos) (Orthoptera: Acridoidea), Covasacris pallidinota (Bruner), Dichroplus pratensis Bruner, Scotussa lemniscata Stål, Borellia bruneri (Rehn) and Dichroplus maculipennis (Blanchard) comprised, on average, 64% of the grasshopper assemblages during low density years and 79% during high density years. Dichroplus elongatus, S. lemniscata and C. pallidinota were the most abundant species in 2001, 2002 and 2003, while D. elongatus, B. brunneri and C. pallidinota in 2009. Dichroplus elongatus and D. pratensis, mixed feeders species, were positively affected by summer rainfall. This suggests that the increase in summer precipitation had a positive effect on the quantity and quality forage production, affecting these grasshopper populations. Scotussa lemniscata and C. pallidinota were negatively affected by winter and fall temperature, possibly affecting the embryonic development before diapause and hatching. Dichroplus elongatus and D. pratensis were associated with highly disturbed pastures, S. lemniscata with pastures and B. bruneri and D. maculipennis with halophilous grasslands. Covasacris pallidinota was closely associated with halophilous grasslands and moderately disturbed pastures. Weather conditions changed over the years, with 2001, 2002 and 2003 having excessive rainfall while 2008 and 2009 were the driest years since the study started. We suggest that although seasonal precipitation and

  10. Influence of weather variables and plant communities on grasshopper density in the Southern Pampas, Argentina.

    PubMed

    de Wysiecki, María Laura; Arturi, Marcelo; Torrusio, Sandra; Cigliano, María Marta

    2011-01-01

    A study was conducted to evaluate the influence of weather (precipitation and temperature) and plant communities on grasshopper density over a 14-year period (1996-2009) in Benito Juárez County, Southern Pampas, Argentina. Total density strongly varied among plant communities. Highest values were registered in 2001 and 2003 in highly disturbed pastures and in 2002 and 2009 in halophilous grasslands. Native grasslands had the lowest density values. Seasonal precipitation and temperature had no significant effect on total grasshopper density. Dichroplus elongatus (Giglio-Tos) (Orthoptera: Acridoidea), Covasacris pallidinota (Bruner), Dichroplus pratensis Bruner, Scotussa lemniscata Stål, Borellia bruneri (Rehn) and Dichroplus maculipennis (Blanchard) comprised, on average, 64% of the grasshopper assemblages during low density years and 79% during high density years. Dichroplus elongatus, S. lemniscata and C. pallidinota were the most abundant species in 2001, 2002 and 2003, while D. elongatus, B. brunneri and C. pallidinota in 2009. Dichroplus elongatus and D. pratensis, mixed feeders species, were positively affected by summer rainfall. This suggests that the increase in summer precipitation had a positive effect on the quantity and quality forage production, affecting these grasshopper populations. Scotussa lemniscata and C. pallidinota were negatively affected by winter and fall temperature, possibly affecting the embryonic development before diapause and hatching. Dichroplus elongatus and D. pratensis were associated with highly disturbed pastures, S. lemniscata with pastures and B. bruneri and D. maculipennis with halophilous grasslands. Covasacris pallidinota was closely associated with halophilous grasslands and moderately disturbed pastures. Weather conditions changed over the years, with 2001, 2002 and 2003 having excessive rainfall while 2008 and 2009 were the driest years since the study started. We suggest that although seasonal precipitation and

  11. Constraining climate sensitivity and continental versus seafloor weathering using an inverse geological carbon cycle model.

    PubMed

    Krissansen-Totton, Joshua; Catling, David C

    2017-05-22

    The relative influences of tectonics, continental weathering and seafloor weathering in controlling the geological carbon cycle are unknown. Here we develop a new carbon cycle model that explicitly captures the kinetics of seafloor weathering to investigate carbon fluxes and the evolution of atmospheric CO2 and ocean pH since 100 Myr ago. We compare model outputs to proxy data, and rigorously constrain model parameters using Bayesian inverse methods. Assuming our forward model is an accurate representation of the carbon cycle, to fit proxies the temperature dependence of continental weathering must be weaker than commonly assumed. We find that 15-31 °C (1σ) surface warming is required to double the continental weathering flux, versus 3-10 °C in previous work. In addition, continental weatherability has increased 1.7-3.3 times since 100 Myr ago, demanding explanation by uplift and sea-level changes. The average Earth system climate sensitivity is  K (1σ) per CO2 doubling, which is notably higher than fast-feedback estimates. These conclusions are robust to assumptions about outgassing, modern fluxes and seafloor weathering kinetics.

  12. Constraining climate sensitivity and continental versus seafloor weathering using an inverse geological carbon cycle model

    NASA Astrophysics Data System (ADS)

    Krissansen-Totton, Joshua; Catling, David C.

    2017-05-01

    The relative influences of tectonics, continental weathering and seafloor weathering in controlling the geological carbon cycle are unknown. Here we develop a new carbon cycle model that explicitly captures the kinetics of seafloor weathering to investigate carbon fluxes and the evolution of atmospheric CO2 and ocean pH since 100 Myr ago. We compare model outputs to proxy data, and rigorously constrain model parameters using Bayesian inverse methods. Assuming our forward model is an accurate representation of the carbon cycle, to fit proxies the temperature dependence of continental weathering must be weaker than commonly assumed. We find that 15-31 °C (1σ) surface warming is required to double the continental weathering flux, versus 3-10 °C in previous work. In addition, continental weatherability has increased 1.7-3.3 times since 100 Myr ago, demanding explanation by uplift and sea-level changes. The average Earth system climate sensitivity is K (1σ) per CO2 doubling, which is notably higher than fast-feedback estimates. These conclusions are robust to assumptions about outgassing, modern fluxes and seafloor weathering kinetics.

  13. Constraining climate sensitivity and continental versus seafloor weathering using an inverse geological carbon cycle model

    PubMed Central

    Krissansen-Totton, Joshua; Catling, David C.

    2017-01-01

    The relative influences of tectonics, continental weathering and seafloor weathering in controlling the geological carbon cycle are unknown. Here we develop a new carbon cycle model that explicitly captures the kinetics of seafloor weathering to investigate carbon fluxes and the evolution of atmospheric CO2 and ocean pH since 100 Myr ago. We compare model outputs to proxy data, and rigorously constrain model parameters using Bayesian inverse methods. Assuming our forward model is an accurate representation of the carbon cycle, to fit proxies the temperature dependence of continental weathering must be weaker than commonly assumed. We find that 15–31 °C (1σ) surface warming is required to double the continental weathering flux, versus 3–10 °C in previous work. In addition, continental weatherability has increased 1.7–3.3 times since 100 Myr ago, demanding explanation by uplift and sea-level changes. The average Earth system climate sensitivity is  K (1σ) per CO2 doubling, which is notably higher than fast-feedback estimates. These conclusions are robust to assumptions about outgassing, modern fluxes and seafloor weathering kinetics. PMID:28530231

  14. Continental and Seafloor Weathering in the Global Carbon Cycle: Inverse Modeling and Implications for the Precambrian

    NASA Astrophysics Data System (ADS)

    Krissansen-Totton, J.; Catling, D. C.

    2016-12-01

    The relative importance of tectonics and continental versus seafloor weathering in controlling the geological carbon cycle are unknown. Here, we present a new open-source, carbon cycle model that explicitly captures the temperature-dependent and pH-dependent kinetics of seafloor weathering to investigate carbon fluxes and the evolution of atmospheric CO2 and ocean pH.We first apply the model to the last 100 Ma and validate model outputs using proxy data. Model parameters are rigorously constrained using Bayesian inverse methods. To fit proxies, the temperature dependence of continental weathering must be much weaker than commonly assumed: we find 14-30°C surface warming is required to double the continental weathering flux, compared to 3-10°C in previous work. Additionally, continental weatherability has approximately doubled since 100 Ma, demanding explanation by uplift and sea level changes. The average Earth system climate sensitivity is also found to be notably higher than fast-feedback estimates. These conclusions are robust to assumptions about outgassing, modern fluxes, and the kinetics of seafloor weathering. Finally, the model is extended to the Precambrian to investigate the relative importance of continental vs. seafloor weathering over Earth history. We contast our results against existing carbon cycle models of the early Earth.

  15. Space Weathering Effects on Sulfates and Carbonates: Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Dukes, Catherine; Bu, Caixia; Rodriguez lopez, Gerard; McFadden, Lucy Ann; Li, Jian-Yang; Ruesch, Ottaviano

    2016-10-01

    Introduction: The solar wind plasma continuously streams from the Sun, interacting with the surfaces of airless bodies throughout the solar system. Sulfates and carbonates, identified by the UV-Vis spectral slope [1] and 3.4 / 4.0 μm absorption features [2] on the surface of Ceres, will be exposed to solar H, He at ~1keV/amu. We investigate the stability of anhydrous salts under 4 keV He+ irradiation as proxy for the solar wind.Experiment: Anhydrous MgSO4, Na2SO4, and Na2CO3 powders are pressed into pellets, with compositions confirmed by XRD. Pellet samples are placed in ultra-high vacuum (10-9 Torr) and the effects of 4keV He+ irradiation on surface composition and chemistry are monitored by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy, as a function of ion fluence. We measure ex situ diffuse optical reflectance prior and subsequent to irradiation through ranges 0.2-2.5µm (Lambda 1050) and 0.6-10µm (Thermo Nicolet 670).Results: Ion irradiation of MgSO4 damages the crystal structure, preferentially removing oxygen along with sulfur. XPS measurements imply the formation of MgO after 5x1017 He+cm-2 (~15,000 years at 2.7AU). During irradiation, we observe secondary ion ejection (Mg, MgO, O, OH, H, S, and SO) and neutral SO2. In addition, XPS sulfur spectra suggest the presence of a small amount of trapped SO2, confirming this decomposition product observed in the optical UV spectra at ~240 and 280nm [3,4] with dehydration, as well as in the IR at ~7.8μm [5] with irradiation. Our observations are consistent with the potential decomposition pathway for MgSO4 to SO2 provided by McCord et al. (2001) [6]. Spectral darkening and reddening in the UV-Vis region after irradiation are observed by ex situ optical spectroscopy. We suggest that space weathering by solar ions limits the stability of salts on Ceres and other airless bodies, which influences the optical reflectance.Acknowledgements: We thank the NASA SSW program for support

  16. Provenance and weathering depth of carbonaceous gotland sandstone by use of carbon and oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Åberg, G.; Löfvendahl, R.; Stijfhoorn, D.; Råheim, A.

    Carbon and oxygen isotope ratios of carbonates (calcite) from different sites and stratigraphic levels of the Gotland sandstone show that it might be possible to fingerprint the different quarries. Preliminary tests of nine samples of Gotland sandstone from different buildings show that the laser microprobe is an excellent tool for estimating depth of weathering on this carbonaceous sandstone. Analyses perpendicular to the stone surface gave a similar trend for the carbon and oxygen isotope ratios, although changes go deeper with δ13C than δ18O. Depth of weathering is controlled by exposure, location, biologic overgrowth and salt efflorescence. The effect of earlier conservation treatment with linseed oil can also be traced.

  17. Anthropogenically enhanced chemical weathering and carbon evasion in the Yangtze Basin.

    PubMed

    Guo, Jingheng; Wang, Fushun; Vogt, Rolf David; Zhang, Yuhang; Liu, Cong-Qiang

    2015-07-07

    Chemical weathering is a fundamental geochemical process regulating the atmosphere-land-ocean fluxes and earth's climate. It is under natural conditions driven primarily by weak carbonic acid that originates from atmosphere CO2 or soil respiration. Chemical weathering is therefore assumed as positively coupled with its CO2 consumption in contemporary geochemistry. Strong acids (i.e. sulfuric- and nitric acid) from anthropogenic sources have been found to influence the weathering rate and CO2 consumption, but their integrated effects remain absent in the world largest river basins. By interpreting the water chemistry and overall proton budget in the Yangtze Basin, we found that anthropogenic acidification had enhanced the chemical weathering by 40% during the past three decades, leading to an increase of 30% in solute discharged to the ocean. Moreover, substitution of carbonic acid by strong acids increased inorganic carbon evasion, offsetting 30% of the CO2 consumption by carbonic weathering. Our assessments show that anthropogenic loadings of sulfuric and nitrogen compounds accelerate chemical weathering but lower its CO2 sequestration. These findings have significant relevance to improving our contemporary global biogeochemical budgets.

  18. Anthropogenically enhanced chemical weathering and carbon evasion in the Yangtze Basin

    PubMed Central

    Guo, Jingheng; Wang, Fushun; Vogt, Rolf David; Zhang, Yuhang; Liu, Cong-Qiang

    2015-01-01

    Chemical weathering is a fundamental geochemical process regulating the atmosphere-land-ocean fluxes and earth’s climate. It is under natural conditions driven primarily by weak carbonic acid that originates from atmosphere CO2 or soil respiration. Chemical weathering is therefore assumed as positively coupled with its CO2 consumption in contemporary geochemistry. Strong acids (i.e. sulfuric- and nitric acid) from anthropogenic sources have been found to influence the weathering rate and CO2 consumption, but their integrated effects remain absent in the world largest river basins. By interpreting the water chemistry and overall proton budget in the Yangtze Basin, we found that anthropogenic acidification had enhanced the chemical weathering by 40% during the past three decades, leading to an increase of 30% in solute discharged to the ocean. Moreover, substitution of carbonic acid by strong acids increased inorganic carbon evasion, offsetting 30% of the CO2 consumption by carbonic weathering. Our assessments show that anthropogenic loadings of sulfuric and nitrogen compounds accelerate chemical weathering but lower its CO2 sequestration. These findings have significant relevance to improving our contemporary global biogeochemical budgets. PMID:26150000

  19. Anthropogenically enhanced chemical weathering and carbon evasion in the Yangtze Basin

    NASA Astrophysics Data System (ADS)

    Guo, Jingheng; Wang, Fushun; Vogt, Rolf David; Zhang, Yuhang; Liu, Cong-Qiang

    2015-07-01

    Chemical weathering is a fundamental geochemical process regulating the atmosphere-land-ocean fluxes and earth’s climate. It is under natural conditions driven primarily by weak carbonic acid that originates from atmosphere CO2 or soil respiration. Chemical weathering is therefore assumed as positively coupled with its CO2 consumption in contemporary geochemistry. Strong acids (i.e. sulfuric- and nitric acid) from anthropogenic sources have been found to influence the weathering rate and CO2 consumption, but their integrated effects remain absent in the world largest river basins. By interpreting the water chemistry and overall proton budget in the Yangtze Basin, we found that anthropogenic acidification had enhanced the chemical weathering by 40% during the past three decades, leading to an increase of 30% in solute discharged to the ocean. Moreover, substitution of carbonic acid by strong acids increased inorganic carbon evasion, offsetting 30% of the CO2 consumption by carbonic weathering. Our assessments show that anthropogenic loadings of sulfuric and nitrogen compounds accelerate chemical weathering but lower its CO2 sequestration. These findings have significant relevance to improving our contemporary global biogeochemical budgets.

  20. Subglacial biochemical weathering and transport drove fertilization in the Southern Ocean during Antarctic temperature maxima and NH Heinrich events

    NASA Astrophysics Data System (ADS)

    Frisia, S.; Augustinus, P. M.; Hellstrom, J.; Borsato, A.; Drysdale, R.; Weyrich, L.; Cooper, A.; Johnston, V. E.; Cotte, M.

    2013-12-01

    Changes in bioproductivity in the subantarctic region have been observed to coincide with episodes of significant iceberg discharge in the North Atlantic (Heinrich events), thus linking iron delivery to the Southern Ocean (SO) with abrupt climate changes in the Northern Hemisphere. Whilst upwelling has been proposed as a likely source of bioavailable iron during Heinrich events, it is well known that, today, subglacial metabolic pathways under limited carbon supply may accumulate divalent iron, which could have been mobilized and delivered to the SO during full glacial conditions. This alternative hypothesis remains largely untested for the SO because of the difficulties in accessing palaeoenvironmental archives from beneath the Antarctic ice sheets. We present a record of the subglacial production and fate of nutrients from calcite crusts formed beneath a tributary of the Rennick outlet glacier (East Antarctic Ice Sheet, EAIS) during the Last Glacial Maximum. Chemistry, stratigraphy and preliminary ancient DNA characterization of the microbial consortium of 27- to 17-kyr-old calcites suggest that bioweathering released iron in hypoxic pools of local basal meltwater. Anaerobic methane oxidising microbes released bicarbonate and sulfuric acid in the isolated pockets, which facilitated local weathering of the amphibolite rock. During episodes of channelized flow, identified by clast-rich microsparites, and which have ages near-commensurate with Antarctic Isotope Maximum2 (AIM2) and Heinrich event 2, ferrous iron may have been mobilized and transported subglacially to the ice shelf. The calcites formed during this phase preserve evidence of microbes using sulfite dehydrogenase, which explains the accumulation of sulfate in the calcite. Our data thus indicate that subglacial processes contributed to SO productivity increases at the time of Heinrich event 2, ultimately leading to drawdawn of atmospheric carbon dioxide at millennial scale.

  1. Dissolved rhenium in river waters: Insight into the chemical weathering of fossil organic carbon?

    NASA Astrophysics Data System (ADS)

    Hilton, Robert; Gaillardet, Jerome

    2010-05-01

    The store of carbon in rock as fossil organic matter represents ~15x1021 g, which is almost 400 times the total amount of carbon present in the oceans and atmosphere. Oxidation of fossil organic carbon (FOC) during chemical weathering returns CO2 that was sequestered from the atmosphere in the geological past, back into the contemporary carbon cycle. Despite this recognition, the natural rates of FOC weathering are poorly constrained in the modern environment, as are the precise controls on its variability. This is primarily due to the difficultly in tracking the dissolved and gaseous carbon produced during FOC weathering, where biology and carbonate weathering mask its influence at a catchment-scale. Here we investigate the use of rhenium (Re) as a tracer of FOC weathering, focusing on a series of mountain catchments in Taiwan. We present dual methodology for determining dissolved Re content in river waters by ICP-MS, using pre-concentration and matrix removal via anion exchange chemistry and by direct analysis through standard-addition. Precision (2sigma) and accuracy at the ppt level are found to be better than 7%. In the 16 sampled catchments, the dissolved Re concentrations span the entire range from the published literature. We investigate the source of dissolved Re in the catchments using measurements of bedrocks and river sediments, and the comparative behavior of Re to major dissolved phases. A preliminary estimate of the Re budget derived from the weathering of FOC is presented, and the implications for the rates of FOC weathering discussed.

  2. Hand-foot-and-mouth disease and weather factors in Guangzhou, southern China.

    PubMed

    Li, T; Yang, Z; DI, B; Wang, M

    2014-08-01

    Hand-foot-and-mouth disease (HFMD) is becoming one of the common airborne and contact transmission diseases in Guangzhou, southern China, leading public health authorities to be concerned about its increased incidence. In this study, we aimed to examine the effect of weather patterns on the incidence of HFMD in the subtropical city of Guangzhou for the period 2009-2012, and assist public health prevention and control measures. A negative binomial multivariable regression was used to identify the relationship between meteorological variables and HFMD. During the study period, a total of 166,770 HFMD-confirmed cases were reported, of which 11 died, yielding a fatality rate of 0·66/10,000. Annual incidence rates from 2009 to 2012 were 132·44, 311·40, 402·76, and 468·59/100,000 respectively. Each 1°C rise in temperature corresponded to an increase of 9·38% (95% CI 8·17-10·51) in the weekly number of HFMD cases, while a 1 hPa rise in atmospheric pressure corresponded to a decrease in the number of cases by 6·80% (95% CI -6·99 to -6·65), having an opposite effect. Similarly, a 1% rise in relative humidity corresponded to an increase of 0·67% or 0·51%, a 1 m/h rise in wind velocity corresponded to an increase of 4·01% or 2·65%, and a 1 day addition in the number of windy days corresponded to an increase of 24·73% or 25·87%, in the weekly number of HFMD cases, depending on the variables considered in the model. Our findings revealed that the epidemic status of HFMD in Guangzhou is characterized by high morbidity but low fatality. Weather factors had a significant influence on occurrence and transmission of HFMD.

  3. Preservation of overmature, ancient, sedimentary organic matter in carbonate concretions during outcrop weathering.

    PubMed

    Loyd, S J

    2017-01-01

    Concretions are preferentially cemented zones within sediments and sedimentary rocks. Cementation can result from relatively early diagenetic processes that include degradation of sedimentary organic compounds or methane as indicated by significantly (13) C-depleted or enriched carbon isotope compositions. As minerals fill pore space, reduced permeability may promote preservation of sediment components from degradation during subsequent diagenesis, burial heating and outcrop weathering. Discrete and macroscopic organic remains, macro and microfossils, magnetic grains, and sedimentary structures can be preferentially preserved within concretions. Here, Cretaceous carbonate concretions of the Holz Shale are shown to contain relatively high carbonate-free total organic carbon (TOC) contents (up to ~18.5 wt%) compared to the surrounding host rock (with <2.1 wt%). TOC increases with total inorganic carbon (TIC) content, a metric of the degree of cementation. Pyrite contents within concretions generally correlate with organic carbon contents. Concretion carbonate carbon isotope compositions (δ(13) Ccarb ) range from -22.5 to -3.4‰ (VPDB) and do not correlate strongly with TOC. Organic carbon isotope compositions (δ(13) Corg ) of concretions and host rock are similar. Thermal maturity data indicate that both host and concretion organic matter are overmature and have evolved beyond the oil window maturity stage. Although the organic matter in general has experienced significant oxidative weathering, concretion interiors exhibit lower oxygen indices relative to the host. These results suggest that carbonate concretions can preferentially preserve overmature, ancient, sedimentary organic matter during outcrop weathering, despite evidence for organic matter degradation genetic mechanisms. As a result, concretions may provide an optimal proxy target for characterization of more primary organic carbon concentrations and chemical compositions. In addition, these findings

  4. Chemical weathering and the role of sulfuric and nitric acids in carbonate weathering: Isotopes (13C, 15N, 34S, and 18O) and chemical constraints

    NASA Astrophysics Data System (ADS)

    Li, Cai; Ji, Hongbing

    2016-05-01

    Multiple isotopes (13C-DIC, 34S and 18O-SO42-, 15N and 18O-NO3-) and water chemistry were used to evaluate weathering rates and associated CO2 consumption by carbonic acid and strong acids (H2SO4 and HNO3) in a typical karst watershed (Wujiang River, Southwest China). The dual sulfate isotopes indicate that sulfate is mainly derived from sulfide oxidation in coal stratum and sulfide-containing minerals, and dual nitrate isotopes indicate that nitrate is mainly derived from soil N and nitrification. The correlation between isotopic compositions and water chemistry suggests that sulfuric and nitric acids, in addition to carbonic acid, are involved in carbonate weathering. The silicate and carbonate weathering rates are 7.2 t km-2 yr-1 and 76 t km-2 yr-1, respectively. In comparison with carbonate weathering rates (43 t km-2 yr-1) by carbonic acid alone, the subsequent increase in rates indicates significant enhancement of weathering when combined with sulfuric and nitric acids. Therefore, the role of sulfuric and nitric acids in the rock weathering should be considered in the global carbon cycle.

  5. The role of forest trees and their mycorrhizal fungi in carbonate rock weathering and its significance for global carbon cycling.

    PubMed

    Thorley, Rachel M S; Taylor, Lyla L; Banwart, Steve A; Leake, Jonathan R; Beerling, David J

    2015-09-01

    On million-year timescales, carbonate rock weathering exerts no net effect on atmospheric CO2 concentration. However, on timescales of decades-to-centuries, it can contribute to sequestration of anthropogenic CO2 and increase land-ocean alkalinity flux, counteracting ocean acidification. Historical evidence indicates this flux is sensitive to land use change, and recent experimental evidence suggests that trees and their associated soil microbial communities are major drivers of continental mineral weathering. Here, we review key physical and chemical mechanisms by which the symbiotic mycorrhizal fungi of forest tree roots potentially enhance carbonate rock weathering. Evidence from our ongoing field study at the UK's national pinetum confirms increased weathering of carbonate rocks by a wide range of gymnosperm and angiosperm tree species that form arbuscular (AM) or ectomycorrhizal (EM) fungal partnerships. We demonstrate that calcite-containing rock grains under EM tree species weather significantly faster than those under AM trees, an effect linked to greater soil acidification by EM trees. Weathering and corresponding alkalinity export are likely to increase with rising atmospheric CO2 and associated climate change. Our analyses suggest that strategic planting of fast-growing EM angiosperm taxa on calcite- and dolomite-rich terrain might accelerate the transient sink for atmospheric CO2 and slow rates of ocean acidification.

  6. Weathering controls on mechanisms of carbon storage in grassland soils

    SciTech Connect

    Masiello, C.A.; Chadwick, O.A.; Southon, J.; Torn, M.S.; Harden, J.W.

    2004-09-01

    On a sequence of soils developed under similar vegetation, temperature, and precipitation conditions, but with variations in mineralogical properties, we use organic carbon and 14C inventories to examine mineral protection of soil organic carbon. In these soils, 14C data indicate that the creation of slow-cycling carbon can be modeled as occurring through reaction of organic ligands with Al3+ and Fe3+ cations in the upper horizons, followed by sorption to amorphous inorganic Al compounds at depth. Only one of these processes, the chelation of Al3+ and Fe3+ by organic ligands, is linked to large carbon stocks. Organic ligands stabilized by this process traverse the soil column as dissolved organic carbon (both from surface horizons and root exudates). At our moist grassland site, this chelation and transport process is very strongly correlated with the storage and long-term stabilization of soil organic carbon. Our 14C results show that the mechanisms of organic carbon transport and storage at this site follow a classic model previously believed to only be significant in a single soil order (Spodosols), and closely related to the presence of forests. The presence of this process in the grassland Alfisol, Inceptisol, and Mollisol soils of this chronosequence suggests that this process is a more significant control on organic carbon storage than previously thought.

  7. Weathering controls on mechanisms of carbon storage in grassland soils

    USGS Publications Warehouse

    Masiello, C.A.; Chadwick, O.A.; Southon, J.; Torn, M.S.; Harden, J.W.

    2004-01-01

    On a sequence of soils developed under similar vegetation, temperature, and precipitation conditions, but with variations in mineralogical properties, we use organic carbon and 14C inventories to examine mineral protection of soil organic carbon. In these soils, 14C data indicate that the creation of slow-cycling carbon can be modeled as occurring through reaction of organic ligands with Al3+ and Fe3+ cations in the upper horizons, followed by sorption to amorphous inorganic Al compounds at depth. Only one of these processes, the chelation Al3+ and Fe3+ by organic ligands, is linked to large carbon stocks. Organic ligands stabilized by this process traverse the soil column as dissolved organic carbon (both from surface horizons and root exudates). At our moist grassland site, this chelation and transport process is very strongly correlated with the storage and long-term stabilization of soil organic carbon. Our 14C results show that the mechanisms of organic carbon transport and storage at this site follow a classic model previously believed to only be significant in a single soil order (Spodosols), and closely related to the presence of forests. The presence of this process in the grassland Alfisol, Inceptisol, and Mollisol soils of this chronosequence suggests that this process is a more significant control on organic carbon storage than previously thought. Copyright 2004 by the American Geophysical Union.

  8. Seasonally different carbon flux changes in the Southern Ocean in response to the southern annular mode

    NASA Astrophysics Data System (ADS)

    Hauck, J.; Völker, C.; Wang, T.; Hoppema, M.; Losch, M.; Wolf-Gladrow, D. A.

    2013-12-01

    Stratospheric ozone depletion and emission of greenhouse gases lead to a trend of the southern annular mode (SAM) toward its high-index polarity. The positive phase of the SAM is characterized by stronger than usual westerly winds that induce changes in the physical carbon transport. Changes in the natural carbon budget of the upper 100 m of the Southern Ocean in response to a positive SAM phase are explored with a coupled ecosystem-general circulation model and regression analysis. Previously overlooked processes that are important for the upper ocean carbon budget during a positive SAM period are identified, namely, export production and downward transport of carbon north of the polar front (PF) as large as the upwelling in the south. The limiting micronutrient iron is brought into the surface layer by upwelling and stimulates phytoplankton growth and export production but only in summer. This leads to a drawdown of carbon and less summertime outgassing (or more uptake) of natural CO2. In winter, biological mechanisms are inactive, and the surface ocean equilibrates with the atmosphere by releasing CO2. In the annual mean, the upper ocean region south of the PF loses more carbon by additional export production than by the release of CO2 into the atmosphere, highlighting the role of the biological carbon pump in response to a positive SAM event.

  9. Predictive zoning of rice stem borer damage in southern India through spatial interpolation of weather-based models.

    PubMed

    Reji, G; Chander, Subhash; Kamble, Kalpana

    2014-09-01

    Rice stem borer is an important insect pest causing severe damage to rice crop in India. The relationship between weather parameters such as maximum (T(max)) and minimum temperature (T(min)), morning (RH1) and afternoon relative humidity (RH2) and the severity of stem borer damage (SB) were studied. Multiple linear regression analysis was used for formulating pest-weather models at three sites in southern India namely, Warangal, Coimbatore and Pattambi as SB = -66.849 + 2.102 T(max) + 0.095 RH1, SB = 156.518 - 3.509 T(min) - 0.785 RH1 and SB = 43.483 - 0.418 T(min) - 0.283 RH1 respectively. The pest damage predicted using the model at three sites did not significantly differ from the observed damage (t = 0.442; p > 0.05). The range of weather parameters favourable for stem borer damage at each site were also predicted using the models. Geospatial interpolation (kriging) of the pest-weather models were carried out to predict the zones of stem borer damage in southern India. Maps showing areas with high, medium and low risk of stem borer damage were prepared using geographical information system. The risk maps of rice stem borer would be useful in devising management strategies for the pest in the region.

  10. Hydrological controls on chemical weathering in the typical carbonated river basin, SW China

    NASA Astrophysics Data System (ADS)

    LI, S. L.; Jin, L.; Zhong, J., Sr.

    2016-12-01

    The dynamics of dissolved load in the riverine system could provide an insight in understanding the surface processes, such as chemical weathering and carbon cycle. The Xijiang River is a typical carbonated river basin, located at southwestern China. The Xijiang River catchment is controlled by a humid subtropical climate. In spite of being impacted by monsoonal climate and with significant variations of discharge, the temporal variations of compositions of main ions and chemical weathering of Xijiang River are rarely documented. In this study, a systematic investigation on the seasonal and episodic water geochemistry (major ions and d13CDIC) of the major branch and outlet of Xijiang River were carried out with the purpose of 1) characterizing temporal variations of aqueous geochemistry and its controlling factors, 2) exploring the impact of hydrological controls on chemical weathering of the Xijiang River Basin. The results show that the concentrations of Cl, Na, Ca, Mg, and HCO3 are generally decreased during monsoon season, which should be mainly caused by dilution. However, the dilution effect does not strictly follow the theoretical dilution curve. Moreover, d13CDIC in the high-flow period has more negative values than in low-flow period. More negative δ13CDIC values in the river during the wet season reflected the influx of rain water with biological CO2 during the rain event. This study suggested that hydrochemistry and d13CDIC had a large variation responding to rainstorm events. The calculated results show that the weathering rates of silicate and carbonate as well as that of related CO2 consumption have a positive relation with water discharge, highlighting the hydrological controls on chemical weathering and CO2 consumption rates. The results indicated carbonated weathering rate responding to hydrological condition sensitivity in the typical carbonate river basin. This work was supported by The China National Science Fund for Outstanding Young Scholars

  11. Atomic Carbon in the Southern Milky Way

    NASA Astrophysics Data System (ADS)

    Oka, Tomoharu; Kamegai, Kazuhisa; Hayashida, Masaaki; Nagai, Makoto; Ikeda, Masafumi; Kuboi, Nobuyuki; Tanaka, Kunihiko; Bronfman, Leonardo; Yamamoto, Satoshi

    2005-04-01

    We present a coarsely sampled longitude-velocity (l-V) map of the region l=300deg-354°, b=0deg in the 492 GHz fine-structure transition of neutral atomic carbon (C0 3P1-3P0 [C I]), observed with the Portable 18 cm Submillimeter-wave Telescope (POST18). The l-V distribution of the [C I] emission resembles closely that of the CO J=1-0 emission, showing a widespread distribution of atomic carbon on the Galactic scale. The ratio of the antenna temperatures, RCI/CO, concentrates on the narrow range from 0.05 to 0.3. A large velocity gradient (LVG) analysis shows that the [C I] emission from the Galactic disk is dominated by a population of neutral gas with high C0/CO abundance ratios and moderate column densities, which can be categorized as diffuse translucent clouds. The ratio of bulk emissivity, JCI/JCO, shows a systematic trend, suggesting the bulk C0/CO abundance ratio increasing with the Galactic radius. A mechanism related to kiloparsec-scale structure of the Galaxy may control the bulk C0/CO abundance ratio in the Galactic disk. Two groups of high-ratio (RCI/CO>0.3) areas reside in the l-V loci several degrees inside of tangential points of the Galactic spiral arms. These could be gas condensations just accumulated in the potential well of spiral arms and be in the early stages of molecular cloud formation.

  12. Production of sulfur gases and carbon dioxide by synthetic weathering of crushed drill cores from the Santa Cruz porphyry copper deposit near Casa Grande, Pinal County, Arizona

    USGS Publications Warehouse

    Hinkle, M.E.; Ryder, J.L.; Sutley, S.J.; Botinelly, T.

    1990-01-01

    Samples of ground drill cores from the southern part of the Santa Cruz porphyry copper deposit, Casa Grande, Arizona, were oxidized in simulated weathering experiments. The samples were also separated into various mineral fractions and analyzed for contents of metals and sulfide minerals. The principal sulfide mineral present was pyrite. Gases produced in the weathering experiments were measured by gas chromatography. Carbon dioxide, oxygen, carbonyl sulfide, sulfur dioxide and carbon disulfide were found in the gases; no hydrogen sulfide, organic sulfides, or mercaptans were detected. Oxygen concentration was very important for production of the volatiles measured; in general, oxygen concentration was more important to gas production than were metallic element content, sulfide mineral content, or mineral fraction (oxide or sulfide) of the sample. The various volatile species also appeared to be interactive; some of the volatiles measured may have been formed through gas reactions. ?? 1990.

  13. Fluoride in weathered rock aquifers of southern India: Managed Aquifer Recharge for mitigation.

    PubMed

    Brindha, K; Jagadeshan, G; Kalpana, L; Elango, L

    2016-05-01

    Climatic condition, geology, and geochemical processes in an area play a major role on groundwater quality. Impact of these on the fluoride content of groundwater was studied in three regions-part of Nalgonda district in Telangana, Pambar River basin, and Vaniyar River basin in Tamil Nadu, southern India, which experience semi-arid climate and are predominantly made of Precambrian rocks. High concentration of fluoride in groundwater above 4 mg/l was recorded. Human exposure dose for fluoride through groundwater was higher in Nalgonda than the other areas. With evaporation and rainfall being one of the major contributors for high fluoride apart from the weathering of fluoride rich minerals from rocks, the effect of increase in groundwater level on fluoride concentration was studied. This study reveals that groundwater in shallow environment of all three regions shows dilution effect due to rainfall recharge. Suitable managed aquifer recharge (MAR) methods can be adopted to dilute the fluoride rich groundwater in such regions which is explained with two case studies. However, in deep groundwater, increase in fluoride concentration with increase in groundwater level due to leaching of fluoride rich salts from the unsaturated zone was observed. Occurrence of fluoride above 1.5 mg/l was more in areas with deeper groundwater environment. Hence, practicing MAR in these regions will increase the fluoride content in groundwater and so physical or chemical treatment has to be adopted. This study brought out the fact that MAR cannot be practiced in all regions for dilution of ions in groundwater and that it is essential to analyze the fluctuation in groundwater level and the fluoride content before suggesting it as a suitable solution. Also, this study emphasizes that long-term monitoring of these factors is an important criterion for choosing the recharge areas.

  14. Carbon mineralization in the southern Sonoran Desert

    NASA Astrophysics Data System (ADS)

    Núñez, Silvia; Martínez-Yrízar, Angelina; Búrquez, Alberto; García-Oliva, Felipe

    2001-12-01

    We measured carbon mineralization in four different desert habitats (Arroyos, Hillsides, Canopies-Plains and Open-Plains) and the separate effect of litter addition from annual and perennial plants on soil microbial respiration using two laboratory soil incubation experiments. The differences in total aboveground phytomass among habitats correlates with soil nutrient content, soil particulate organic matter (POM) and consequently, C mineralization. The Arroyos habitat with the highest perennial plant phytomass and litter production, had the highest soil nutrient content, soil POM and C mineralization. Litter from annual plants had twice the P concentration than litter from the perennials, but only half the N concentration. Soil microbial respiration was higher with annual plant litter than with perennial plant litter in the Hillsides and Canopies-Plains, suggesting that microbial activity in both habitats was improved by litter with a higher C quality. In contrast, in the poorest habitat, the Open-Plains, the better response to the addition of perennial plant litter suggests that microbial activity may have been constrained by N input.

  15. An observing system simulation for Southern Ocean carbon dioxide uptake.

    PubMed

    Majkut, Joseph D; Carter, Brendan R; Frölicher, Thomas L; Dufour, Carolina O; Rodgers, Keith B; Sarmiento, Jorge L

    2014-07-13

    The Southern Ocean is critically important to the oceanic uptake of anthropogenic CO2. Up to half of the excess CO2 currently in the ocean entered through the Southern Ocean. That uptake helps to maintain the global carbon balance and buffers transient climate change from fossil fuel emissions. However, the future evolution of the uptake is uncertain, because our understanding of the dynamics that govern the Southern Ocean CO2 uptake is incomplete. Sparse observations and incomplete model formulations limit our ability to constrain the monthly and annual uptake, interannual variability and long-term trends. Float-based sampling of ocean biogeochemistry provides an opportunity for transforming our understanding of the Southern Ocean CO2 flux. In this work, we review current estimates of the CO2 uptake in the Southern Ocean and projections of its response to climate change. We then show, via an observational system simulation experiment, that float-based sampling provides a significant opportunity for measuring the mean fluxes and monitoring the mean uptake over decadal scales. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  16. Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon.

    PubMed

    Daines, Stuart J; Mills, Benjamin J W; Lenton, Timothy M

    2017-02-02

    It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of order pO2∼0.1 PAL (present atmospheric level), but that stability is lost at pO2<0.01 PAL. Within these limits, the carbonate carbon isotope (δ(13)C) record becomes insensitive to changes in organic carbon burial rate, due to counterbalancing changes in the weathering of isotopically light organic carbon. This can explain the lack of secular trend in the Precambrian δ(13)C record, and reopens the possibility that increased biological productivity and resultant organic carbon burial drove the Great Oxidation Event.

  17. Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon

    PubMed Central

    Daines, Stuart J.; Mills, Benjamin J. W.; Lenton, Timothy M.

    2017-01-01

    It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of order pO2∼0.1 PAL (present atmospheric level), but that stability is lost at pO2<0.01 PAL. Within these limits, the carbonate carbon isotope (δ13C) record becomes insensitive to changes in organic carbon burial rate, due to counterbalancing changes in the weathering of isotopically light organic carbon. This can explain the lack of secular trend in the Precambrian δ13C record, and reopens the possibility that increased biological productivity and resultant organic carbon burial drove the Great Oxidation Event. PMID:28148950

  18. Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon

    NASA Astrophysics Data System (ADS)

    Daines, Stuart J.; Mills, Benjamin J. W.; Lenton, Timothy M.

    2017-02-01

    It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of order pO2~0.1 PAL (present atmospheric level), but that stability is lost at pO2<0.01 PAL. Within these limits, the carbonate carbon isotope (δ13C) record becomes insensitive to changes in organic carbon burial rate, due to counterbalancing changes in the weathering of isotopically light organic carbon. This can explain the lack of secular trend in the Precambrian δ13C record, and reopens the possibility that increased biological productivity and resultant organic carbon burial drove the Great Oxidation Event.

  19. Concentration of atmospheric carbon dioxide at Ocean Weather Station P from 1969 to 1981

    SciTech Connect

    Keeling, C.D.; Whorf, T.P.; Wong, C.S.; Bellagay, R.D.

    1985-10-20

    From May 1959 to June 1981 the concentration of atmospheric carbon dioxide was measured in 2419 samples of air collected on a weather ship situated at 50/sup 0/N and 145/sup 0/W in the North Pacific Ocean. Three principal characteristics of the variation in concentration of atmospheric CO/sub 2/ are revealed by these data: an annual variation that repeats with nearly the same pattern each year, an interannual variation that correlates with the large-scale circulation of the atmosphere, and a long-term increase that is nearly proportional to the global input of CO/sub 2/ from the combustion of fossil fuels. The peak-to-trough amplitude of the smoothed annual signal increased from 13.3 ppM in 1969 to 14.5 ppM in 1981. The phasing of the annual CO/sub 2/ cycle suggests a close relation to the activity of land plants in the broad region of the northern hemisphere where plants grow mainly during the summer. The increasing amplitude suggests a heightening plant activity. The interannual variation and its first derivative correlate with the Southern Oscillation. A lag of 6 months in the derivative suggests a distant oceanic or terrestrial source-sink in the tropics or southern hemisphere. The seasonally adjusted CO/sub 2/ concentration increased from 324.9 ppM in May 1969 to 340.8 ppM in June 1981. This increase is 60% of the increase that would have occurred if all the CO/sub 2/ from fossil fuel combustion had remained in the atmosphere and had been uniformly distributed there. The seasonally adjusted concentration, when averaged from 1975 to 1981, is 0.8 ppM lower than that found at Point Barrow, Alaska, at 71/sup 0/N and 0.9 ppM higher than that found at Mauna Loa Observatory, Hawaii, at 19/sup 0/N, suggesting a steadily decreasing concentration in CO/sub 2/ from north to south in the broad band from 70/sup 0/N to 20/sup 0/N.

  20. The contribution of weathering of the main Alpine rivers on the global carbon cycle

    NASA Astrophysics Data System (ADS)

    Donnini, Marco; Probst, Jean-Luc; Probst, Anne; Frondini, Francesco; Marchesini, Ivan; Guzzetti, Fausto

    2013-04-01

    On geological time-scales the carbon fluxes from the solid Earth to the atmosphere mainly result from volcanism and metamorphic-decarbonation processes, whereas the carbon fluxes from atmosphere to solid Earth mainly depend on weathering of silicates and carbonates, biogenic precipitation and removal of CaCO3 in the oceans and volcanic gases - seawater interactions. Quantifying each contribution is critical. In this work, we estimate the atmospheric CO2 uptake by weathering in the Alps, using results of the study of the dissolved loads transported by 33 main Alpine rivers. The chemical composition of river water in unpolluted areas is a good indicator of surface weathering processes (Garrels and Mackenzie, 1971; Drever, 1982; Meybeck, 1984; Tardy, 1986; Berner and Berner, 1987; Probst et al., 1994). The dissolved load of streams originates from atmospheric input, pollution, evaporite dissolution, and weathering of carbonate and silicate rocks, and the application of mass balance calculations allows quantification of the different contributions. In this work, we applied the MEGA (Major Element Geochemical Approach) geochemical code (Amiotte Suchet, 1995; Amiotte Suchet and Probst, 1996) to the chemical compositions of the selected rivers in order to quantify the atmospheric CO2 consumed by weathering in Alpine region. The drainage basins of the main Alpine rivers were sampled near the basin outlets during dry and flood seasons. The application of the MEGA geochemical consisted in several steps. First, we subtracted the rain contribution in river waters knowing the X/Cl (X = Na, K, Mg, Ca) ratios of the rain. Next, we considered that all (Na+K) came from silicate weathering. The average molar ratio Rsil = (Na+K)/(Ca+Mg) for rivers draining silicate terrains was estimated from unpolluted French stream waters draining small monolithological basins (Meybeck, 1986; 1987). For the purpose, we prepared a simplified geo-lithological map of Alps according to the lithological

  1. Rapid growth of magnesium-carbonate weathering products in a stony meteorite from Antarctica

    NASA Technical Reports Server (NTRS)

    Jull, A. J. T.; Cheng, S.; Gooding, J. L.; Velbel, M. A.

    1988-01-01

    Nesquehonite, a hydrous magnesium carbonate, occurs as a weathering product on the surface of the Antarctic meteorite LEW 85320 (H5 chondrite). Isotopic measurements of delta(C-13) and delta(O-18) indicate that the nesquehonite formed at near freezing temperatures by reaction of meteoritic minerals with terrestrial water and carbon dioxide. Results from carbon-14 dating suggest that, although the meteorite has been in Antarctica for at least 32,000 to 33,000 years, the nesquehonite formed after AD 1950.

  2. Rapid growth of magnesium-carbonate weathering products in a stony meteorite from Antarctica

    NASA Technical Reports Server (NTRS)

    Jull, A. J. T.; Cheng, S.; Gooding, J. L.; Velbel, M. A.

    1988-01-01

    Nesquehonite, a hydrous magnesium carbonate, occurs as a weathering product on the surface of the Antarctic meteorite LEW 85320 (H5 chondrite). Isotopic measurements of delta(C-13) and delta(O-18) indicate that the nesquehonite formed at near freezing temperatures by reaction of meteoritic minerals with terrestrial water and carbon dioxide. Results from carbon-14 dating suggest that, although the meteorite has been in Antarctica for at least 32,000 to 33,000 years, the nesquehonite formed after AD 1950.

  3. Can enhanced weathering remove carbon dioxide from the atmosphere to prevent climate change? (Invited)

    NASA Astrophysics Data System (ADS)

    Renforth, P.; Pogge von Strandmann, P.; Henderson, G. M.

    2013-12-01

    On long timescales, silicate weathering provides the ultimate sink for CO2 released by volcanic degassing and, because the rate of such weathering is temperature dependant, this sink is thought to respond to climate change to provide a strong negative feedback stabilising Earth's climate. An increase of global weathering rates is expected in response to anthropogenic warming and this increased weathering will ultimately (on the timescale of hundreds of thousands of years) serve to remove additional CO2 and return the climate system to lower temperatures. Some have proposed that accelerating this natural process by adding ground minerals to the land surface may help to prevent climate change. However, a major challenge in assessing such a proposal is the lack of experimental kinetic data for minerals added to the environment. Here we will present results from an experiment in which a forsterite rich olivine (Mg2SiO4) was added to the top of a soil column extracted from an agricultural field. A solution was passed through the columns over a period of 5 months and the drainage waters were collected and analysed. The greater flux of Mg measured eluting from the treated soil can be used to constrain the weathering rate of the olivine. A weathering rate can be determined by normalising the rate of magnesium flux to the surface area of olivine in the soil. By combining this information with a simple shrinking core model, we can estimate that an average particle size less than 1 μm would be required in order for the olivine to completely dissolve in a year. Therefore, the energy requirements for enhanced weathering are large >2 GJ(electrical) per net tonne of CO2 sequestered, but it is at least comparable to direct air capture technologies. These preliminary results suggest limited carbon capture potential for enhanced weathering in temperate agricultural soils. However, some environments may be better suited (e.g. humid tropical agricultural soils) and additional

  4. Contribution of forests to the carbon sink via biologically-mediated silicate weathering: A case study of China.

    PubMed

    Song, Zhaoliang; Liu, Hongyan; Strömberg, Caroline A E; Wang, Hailong; Strong, Peter James; Yang, Xiaomin; Wu, Yuntao

    2017-09-29

    During silicate weathering, atmospheric carbon dioxide (CO2) is consumed and base cations are released from silicate minerals to form carbonate and bicarbonate ions, which are finally deposited as carbonate complexes. Continental silicate weathering constitutes a stable carbon sink that is an important influence on long-term climate change, as it sequesters atmospheric carbon dioxide at a million-year time scale. Traditionally, CO2 sequestered through silicate weathering is estimated by measuring the flux of the base cations to watersheds. However, plants also absorb considerable amounts of base cations. Plant biomass is often removed from ecosystems during harvesting. The base cations are subsequently released after decomposition of the harvested plant materials, and thereby enhance CO2 consumption related to weathering. Here, we analyze plant biomass storage-harvest fluxes (production and removal of biomass from forests) of base cations in forests across China to quantify the relative contribution of forest trees to the terrestrial weathering-related carbon sink. Our data suggest that the potential CO2 consumption rate for biomass-related silicate weathering (from the combined action of with afforestation/reforestation, controlled harvesting and rock powder amendment) in Chinese forests is 7.9±4.1Tg CO2yr(-1). This represents ~34% of the chemical weathering rate in China. Globally, forests may increase CO2 sequestration through biologically-mediated silicate weathering by ~32%. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Carbonate weathering as a driver of CO2 supersaturation in lakes

    NASA Astrophysics Data System (ADS)

    Marcé, Rafael; Obrador, Biel; Morguí, Josep-Anton; Lluís Riera, Joan; López, Pilar; Armengol, Joan

    2015-02-01

    Most lakes and reservoirs have surface CO2 concentrations that are supersaturated relative to the atmosphere. The resulting CO2 emissions from lakes represent a substantial contribution to the continental carbon balance. Thus, the drivers of CO2 supersaturation in lakes need to be understood to constrain the sensitivity of the land carbon cycle to external perturbations. Carbon dioxide supersaturation has generally been attributed to the accumulation of inorganic carbon in lakes where respiration exceeds photosynthesis, but this interpretation has faced challenges. Here we report analyses of water chemistry data from a survey of Spanish reservoirs that represent a range of lithologies, using simple metabolic models. We find that, above an alkalinity threshold of 1 mequiv. l-1, CO2 supersaturation in lakes is directly related to carbonate weathering in the watershed. We then evaluate the global distribution of alkalinity in lakes and find that 57% of the surface area occupied by lakes and reservoirs--particularly in tropical and temperate latitudes--has alkalinity exceeding 1 mequiv. l-1. We conclude that lake inputs of dissolved inorganic carbon from carbonate weathering should be considered for the CO2 supersaturation of lakes at both regional and global scales.

  6. Weathering resistance of carbonate fault mirrors promotes rupture localization

    NASA Astrophysics Data System (ADS)

    Goldberg, R.; Siman-Tov, S.; Emmanuel, S.

    2016-04-01

    Fractured rocks in fault zones regain their mechanical strength through a process called healing. A central pathway for healing involves the dissolution and reprecipitation of minerals in the fault zone which cements the fractured rocks during interseismic periods. However, some faults contain highly polished surfaces—coated in a thin nanoparticle layer—along which slip is localized. Crucially, these surfaces show little evidence of postseismic mineralization and healing. Here we use atomic force microscopy to show that naturally polished rocks from carbonate fault zones are resistant to dissolution, in stark contrast to the reactive minerals that make up the fault breccia. Our results suggest that the low reactivity of the nanoparticle layer could retard healing, helping to maintain the localization of the fault zone between seismic slip events. As fault localization affects seismic motion, the geochemical reactivity of fault mirrors could be an important control on seismicity along faults.

  7. Carbon and oxygen isotope composition of carbonates from an L6 chondrite: Evidence for terrestrial weathering from the Holbrook meteorite

    NASA Technical Reports Server (NTRS)

    Socki, R. A.; Gibson, E. K.; Jull, A. J. T.; Karlsson, H. R.

    1991-01-01

    Terrestrial weathering in meteorites is an important process which alters pristine elemental and isotopic abundances. The Holbrook L6 chondrite fell in 1912. Material was recovered at the time of the fall, in 1931, and 1968. The weathering processes operating on the freshly fallen meteorite in a semi-arid region of northeastern Arizona have been studied after a ground residence of 19 and 56 years. It has been shown that a large portion of the carbonate material in 7 Antarctic ordinary chondrites either underwent extensive isotopic exchange with atmospheric CO2, or formed recently in the Antarctic environment. In fact it has been demonstrated that hydrated Mg-carbonates, nesquehonite and hydromagnesite, formed in less than 40 years on LEW 85320. In order to help further constrain the effects of terrestrial weathering in meteorites, the carbon and oxygen isotopes extracted from carbonates of three different samples of Holbrook L6: a fresh sample at the time of the fall in 1912, a specimen collected in 1931, and a third specimen collected at the same site in 1968.

  8. From the surface to the deep critical zone: Linking soil carbon, fluid saturation and weathering rate

    NASA Astrophysics Data System (ADS)

    Druhan, Jennifer; Lawrence, Corey; Oster, Jessica; Rempe, Daniella; Dietrich, William

    2017-04-01

    Shallow soils from a wide range of ecosystems demonstrate a clear and consistent relationship between effective fluid saturation and the rate at which organic carbon is converted to CO2. While the underlying mechanisms contributing to this dependence are diverse, a consistent pattern of maximum CO2 production at intermediate soil moisture supports a generalized functional relationship, which may be incorporated into a quantitative reactive transport framework. A key result of this model development is a prediction of the extent to which the inorganic carbon content of water in biologically active soils varies as a function of hydrologic parameters (i.e. moisture content and residence time), and in turn influences weathering reactions. Deeper in the CZ, the consistency of this relationship and the influence of hydrologically - regulated CO2 production on the rates of water - rock interaction are largely unknown. Here, we use a novel reactive transport model incorporating this functional relationship to consider how variations in the reactive potential of water entering the vadose zone influences subsurface weathering rates. We leverage two examples of variably saturated natural systems to consider (1) CO2 production and associated weathering potential regulated by seasonal hydrologic shifts and (2) the preservation of soil carbon signatures in the deep CZ over millennial timescales. First, at the Eel River CZ Observatory in Northern California, USA, a novel Vadose Zone Monitoring System (VMS) installed in a 14 - 20 m thick unsaturated section offers an unprecedented view into the physical, chemical and biological behavior of the depth profile separating soils from groundwater. Based on soil moisture, gas and fluid phase samples, we demonstrate a predictive relationship between seasonal hydrologic variations and the location and magnitude of geochemical weathering rates. Second, an environmental monitoring project in the Blue Springs Cave, Sparta, TN, USA, provides

  9. Comparison of field and laboratory weathering rates in carbonate rocks from an Eastern Mediterranean drainage basin

    NASA Astrophysics Data System (ADS)

    Levenson, Yael; Ryb, Uri; Emmanuel, Simon

    2017-05-01

    The rates of carbonate rock weathering affect the global carbon cycle over timescales of hundreds to thousands of years. While field measurements show that the rate of carbonate denudation increases with rainfall, significant variability exists. To determine whether the mineralogical composition of the rocks causes this variability, we compare published long-term field denudation rates determined from cosmogenic isotopes (36Cl) with the weathering rates measured in laboratory experiments conducted on the same rock samples. The samples were collected from natural-rock outcrops across the Soreq drainage basin (Israel) that experience similar mean annual precipitation, but exhibit long-term denudation rates that vary from 6 mm ky-1 to 20 mm ky-1. In laboratory experiments, we found that the laboratory rates also varied, decreasing as the ratio of dolomite to calcite increased. However, no correlation was evident between the long-term denudation rates and mineral composition, suggesting that the variability in field rates was not controlled by the kinetics of dissolution. Other factors, such as rain intensity, biological activity, and mechanical erosion are likely to control the variability in the rates by inhibiting or accelerating the weathering of carbonate surfaces in natural settings.

  10. Carbonate-hosted nonsulphide Zn-Pb mineralization of southern British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Paradis, Suzanne; Keevil, Halley; Simandl, George J.; Raudsepp, Mati

    2015-12-01

    Many carbonate-hosted sulphide deposits in the Salmo district of southern British Columbia have near-surface Zn- and Pb-bearing iron oxide-rich gossans. The gossans formed when carbonate-hosted, base metal sulphides were subjected to intense supergene weathering processes and metals were liberated by the oxidation of sulphide minerals. Two types of supergene carbonate-hosted nonsulphide deposits, direct replacement (`red ore') and wallrock replacement (`white ore'), are present in the Salmo district. The direct replacement deposits formed by the oxidation of primary sulphides; the base metals passed into solution and were redistributed and trapped within the space occupied by the oxidized portion of the sulphide protore. Depending on the extent of replacement of the sulphides by Zn-, Pb- and Fe-bearing oxides, silicates, carbonates and phosphates, the resulting ore can be called `mixed' (sulphides and nonsulphides) or simply `nonsulphide'. The wallrock replacement deposits formed when base metals liberated by the oxidation of sulphides were transported by circulating supergene solutions down and/or away from the sulphides to form wallrock replacement deposits. The direct replacement nonsulphide zones of the Salmo district overlay the sulphide bodies in which they replaced the sulphides and carbonates, forming large irregular replacement masses, encrustations and open-space fillings. They consist predominantly of hematite, goethite, hemimorphite [Zn4Si2O7(OH)2·H2O], minor hydrozincite [Zn5(CO3)2(OH)6], cerussite [PbCO3] and traces of willemite [Zn2SiO4]. The wallrock replacement zones consist mainly of hemimorphite with local occurrences of iron oxides, hopeite [Zn3(PO4)2·4H2O] and tarbuttite [Zn2(PO4)(OH)]. No remnants of sulphides were observed in the replacement zones. The Salmo nonsulphide deposits were formed by prolonged weathering of Mississippi Valley-type (MVT) mineralization that underwent dissolution and oxidation of the pyrite, sphalerite and galena

  11. Impact of different fertilizers on carbonate weathering in a typical karst area, Southwest China: a field column experiment

    NASA Astrophysics Data System (ADS)

    Song, Chao; Liu, Changli; Han, Guilin; Liu, Congqiang

    2017-09-01

    Carbonate weathering, as a significant vector for the movement of carbon both between and within ecosystems, is strongly influenced by agricultural fertilization, since the addition of fertilizers tends to change the chemical characteristics of soil such as the pH. Different fertilizers may exert a different impact on carbonate weathering, but these discrepancies are as yet not well-known. In this study, a field column experiment was conducted to explore the response of carbonate weathering to the addition of different fertilizers. We compared 11 different treatments, including a control treatment, using three replicates per treatment. Carbonate weathering was assessed by measuring the weight loss of limestone and dolostone tablets buried at the bottom of soil-filled columns. The results show that the addition of urea, NH4NO3, NH4HCO3, NH4Cl and (NH4)2CO3 distinctly increased carbonate weathering, which was attributed to the nitrification of NH4+. The addition of Ca3(PO4)2, Ca-Mg-P and K2CO3 induced carbonate precipitation due to the common ion effect. The addition of (NH4)3PO4 and NaNO3 had a relatively small impact on carbonate weathering in comparison to those five NH4-based fertilizers above. The results of NaNO3 treatment raise a new question: the negligible impact of nitrate on carbonate weathering may result in an overestimation of the impact of N fertilizer on CO2 consumption by carbonate weathering on the regional/global scale if the effects of NO3 and NH4 are not distinguished.

  12. Opportunities and challenges of indigenous biotic weather forecasting among the Borena herders of southern Ethiopia.

    PubMed

    Ayal, Desalegn Yayeh; Desta, Solomon; Gebru, Getachew; Kinyangi, James; Recha, John; Radeny, Maren

    2015-01-01

    The practical utilization of available modern as well as traditional weather forecasting systems builds herders' resiliency capacity to climatic shocks. The precision and reliability of the forecasting system determines its creditability and acceptance by the users to be proactive in the decisions they make based on the forecasted information. It has been postulated that traditional weather forecasting systems are becoming less reliable due to repeated faulty forecasts. The study assesses the current status of the Borana traditional weather forecasting system and how traditional experts make weather forecasts based on biotic indicators such as intestinal readings, changes in plant and animal body languages. Questionnaire survey, field observations, focus group discussions and interviews with relevant key informants were employed to obtain data. Collected field data was compared with National Metrological Service Agency instrumental data for consistency. Results reveal that herders made short term weather forecasts using intestinal readings, and observed changes in plant and animal body languages. The study shows the extent how public confidence in the accuracy of indigenous weather forecasting skills has been gradually eroded overtime due to faulty forecasts. The precision and credibility of the traditional weather forecast steadily declined and led to repeated faulty predictions. Poor documentation, oral based knowledge transfer system, influence of religion and modern education, aging and extinction of traditional experts were identified as the major causes undermining the vitality of traditional climate forecast. Traditional weather foresting knowledge and skill could have some utility and also serve as a starting point to scientifically study the relationship between various signs and implied climatic events. This article recommends before traditional Borana weather forecasting system completely disappears, a remedial action should be carried out to rescue this

  13. Engineering-Geological Properties of Carbonate Rocks in Relation to Weathering Intensity

    NASA Astrophysics Data System (ADS)

    Pollak, Davor

    For most of the purposes engineering-geological explorations are done on the surface. Afterwards the surface data get correlated with other exploration results in order to produce rock mass quality model. The modelling of subsurface and deeper zones in karst areas in Croatia is usually a difficult task because of a complex geology. The evaluation of rock mass quality in those zones is even more demanding mainly because of the specific weathering processes of carbonate rocks. Since karstification significantly changes engineering-geological properties of carbonate rocks, it is of vital importance to determine the degree of weathering in surface and subsurface zones. Engineering-geological properties of carbonate rocks in the surface zone, subsurface and deeper zones are compared and discussed in the paper. Facts and examples are taken from recent highway projects in Croatia. From those data it has been recognized, that depending on the basic block size, two basic weathering models can be established. Each of the models has its specific engineering-geological properties.

  14. Effect of carbonic anhydrase on silicate weathering and carbonate formation at present day CO₂ concentrations compared to primordial values.

    PubMed

    Xiao, Leilei; Lian, Bin; Hao, Jianchao; Liu, Congqiang; Wang, Shijie

    2015-01-13

    It is widely recognized that carbonic anhydrase (CA) participates in silicate weathering and carbonate formation. Nevertheless, it is still not known if the magnitude of the effect produced by CA on surface rock evolution changes or not. In this work, CA gene expression from Bacillus mucilaginosus and the effects of recombination protein on wollastonite dissolution and carbonate formation under different conditions are explored. Real-time fluorescent quantitative PCR was used to explore the correlation between CA gene expression and sufficiency or deficiency in calcium and CO₂ concentration. The results show that the expression of CA genes is negatively correlated with both CO₂ concentration and ease of obtaining soluble calcium. A pure form of the protein of interest (CA) is obtained by cloning, heterologous expression, and purification. The results from tests of the recombination protein on wollastonite dissolution and carbonate formation at different levels of CO₂ concentration show that the magnitudes of the effects of CA and CO₂ concentration are negatively correlated. These results suggest that the effects of microbial CA in relation to silicate weathering and carbonate formation may have increased importance at the modern atmospheric CO₂ concentration compared to 3 billion years ago.

  15. Effect of carbonic anhydrase on silicate weathering and carbonate formation at present day CO2 concentrations compared to primordial values

    PubMed Central

    Xiao, Leilei; Lian, Bin; Hao, Jianchao; Liu, Congqiang; Wang, Shijie

    2015-01-01

    It is widely recognized that carbonic anhydrase (CA) participates in silicate weathering and carbonate formation. Nevertheless, it is still not known if the magnitude of the effect produced by CA on surface rock evolution changes or not. In this work, CA gene expression from Bacillus mucilaginosus and the effects of recombination protein on wollastonite dissolution and carbonate formation under different conditions are explored. Real-time fluorescent quantitative PCR was used to explore the correlation between CA gene expression and sufficiency or deficiency in calcium and CO2 concentration. The results show that the expression of CA genes is negatively correlated with both CO2 concentration and ease of obtaining soluble calcium. A pure form of the protein of interest (CA) is obtained by cloning, heterologous expression, and purification. The results from tests of the recombination protein on wollastonite dissolution and carbonate formation at different levels of CO2 concentration show that the magnitudes of the effects of CA and CO2 concentration are negatively correlated. These results suggest that the effects of microbial CA in relation to silicate weathering and carbonate formation may have increased importance at the modern atmospheric CO2 concentration compared to 3 billion years ago. PMID:25583135

  16. Effect of carbonic anhydrase on silicate weathering and carbonate formation at present day CO2 concentrations compared to primordial values

    NASA Astrophysics Data System (ADS)

    Xiao, Leilei; Lian, Bin; Hao, Jianchao; Liu, Congqiang; Wang, Shijie

    2015-01-01

    It is widely recognized that carbonic anhydrase (CA) participates in silicate weathering and carbonate formation. Nevertheless, it is still not known if the magnitude of the effect produced by CA on surface rock evolution changes or not. In this work, CA gene expression from Bacillus mucilaginosus and the effects of recombination protein on wollastonite dissolution and carbonate formation under different conditions are explored. Real-time fluorescent quantitative PCR was used to explore the correlation between CA gene expression and sufficiency or deficiency in calcium and CO2 concentration. The results show that the expression of CA genes is negatively correlated with both CO2 concentration and ease of obtaining soluble calcium. A pure form of the protein of interest (CA) is obtained by cloning, heterologous expression, and purification. The results from tests of the recombination protein on wollastonite dissolution and carbonate formation at different levels of CO2 concentration show that the magnitudes of the effects of CA and CO2 concentration are negatively correlated. These results suggest that the effects of microbial CA in relation to silicate weathering and carbonate formation may have increased importance at the modern atmospheric CO2 concentration compared to 3 billion years ago.

  17. Typical Infrasonic Daily Changes Associated with Weather Conditions in Southern Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Lee, S. T.

    2015-12-01

    The dominant source of infrasonic waves in Korean peninsula is associated with weather changes around 0.1 to several hertz. The microbarom are mainly observed with KMA(Korea Meteorological Administration) infrasound station and other activity associated with typhoon in summer. The period of observation was processed during year of 2012. The KMA running two permanent infrasound stations at the middle of Korean peninsula which located DeMilitarized Zone from the 2011. For the special event that recorded from the Northern Korean Peninsula was missle launch 12-Dec 2012 which was clearly recorded. The Korean peninsula is located on Northern Hemisphere that induce the typhoon visit in summer rainy season, so main infrasonic activity was associated this weather changes concentrated general weather activity frequency area. We focused on seasonal changes induced by weather activities and processed infrasonic data related with typhoon report by KMA's weather report. The progressing results was reviewed for the infrasonic noise level changes which associated with typhoon and missle launch record on Dec-2012 for the special event.

  18. Effects of paleogeology, chemical weathering, and climate on the global geochemical cycle of carbon dioxide

    SciTech Connect

    Bluth, G.J.S.

    1990-01-01

    A new method of geologic reconstruction has been developed that determines areas of exposure for each epoch of the Phanerozoic. The paleogeologic maps reveal that the relative proportions of exposed rock types show few abrupt changes through Phanerozoic time, compared to the secular changes in areal extent of rock deposition. Chemical weathering of silicate minerals acts as a long-term transfer of CO{sub 2} from the atmosphere to carbonate sediments via river runoff. Thus, the roles of silicate and non-silicate rocks must be differentiated. Chemical records of streams draining monolithologic basins confirm that the relative weathering susceptibility of lithologies clearly favors carbonate over silicate rocks; surprisingly, among the silicates (clastic and igneous) there is no significant distinction. A survey of basalt catchments shows no correlation between temperature and weathering. Although a warm, wet climate promotes mineral weathering, this may be countered over time by soil shielding of bedrock-groundwater interactions. Mean annual runoff rates are 60% higher at {minus}100 my (using 4x current CO{sub 2}) from CCM simulations but, since Cretaceous land area is 30% smaller, total runoff changes very little. However, in a spatially distributed model of the Earth the annual bicarbonate flux of the Cretaceous (4x CO{sub 2}) is 59 {times} 10{sup 12}eq, compared to 39 {times} 10{sup 12}eq for the present-day. Net HCO{sub 3}{sup {minus}} flux from silicate weathering is 25% higher in the Cretaceous, because the distribution of silicate exposures coincides with regions of intense runoff. Thus, by adding spatial dimensions of runoff and geology to preexisting models, the balance of CO{sub 2} levels by silicate dissolution can be achieved without severe changes in either atmospheric chemistry or rock proportions.

  19. The carbon cycle implications of chemical weathering in retrogressive thaw slump-impacted streams

    NASA Astrophysics Data System (ADS)

    Zolkos, S.; Tank, S. E.; Kokelj, S. V.

    2016-12-01

    Permafrost thaw is "unlocking" and exposing significant amounts of sediment, solutes and organic carbon previously maintained in frozen soils to biochemical processing and fluvial transport. While microbial respiration of permafrost organic carbon contributes significantly to CO2 in Arctic headwater streams, chemical weathering of minerals unearthed by thawing permafrost may fix CO2 as bicarbonate (HCO3), thus removing it from the active carbon cycle. However, the degree to which mineral weathering acts to temper CO2 generated during permafrost thaw is largely unknown. During summer 2015, we investigated these dynamics in eight streams (orders 1-3) impacted by retrogressive thaw slumps across the Peel Plateau (NT, Canada), where thaw slumps expose permafrost that is comprised of abundant glacial tills, and glaciofluvial and glaciolacustrine sediments. Thaw slump activity had a discernible signature in all streams: conductivity, pH, dissolved inorgnaic carbon (DIC), and solute concentrations (Ca, Mg, Na, K, SO4, Cl) increased in the downstream (thaw slump-impacted) reach, relative to upstream, while CO2 decreased. This corresponded with an isotopically-enriched DIC pool in impacted streams (mean δ13CDIC = -9.80‰), perhaps indicating the dissolution of carbonate minerals following exposure by thaw slump activity. Despite a general decrease downstream of thaw slumps, CO2 remained supersaturated in impacted streams (mean pCO2 = 915 µatm). However, the highest partial pressures of CO2 were found in thaw slump runoff (mean pCO2 = 4,600 µatm), above the point where runoff entered downstream systems. High pCO2 levels in slump runoff may be derived from microbial respiration of slump-released dissolved organic carbon or, for some slumps, carbonate dissolution (range δ13CDIC = 0.67 - -23.37‰). While this work suggests thaw slumps in the Western Canadian Arctic may act to partially temper CO2 in headwater streams, these stream networks will likely persist as

  20. Extreme weather events in southern Germany - Climatological risk and development of a large-scale identification procedure

    NASA Astrophysics Data System (ADS)

    Matthies, A.; Leckebusch, G. C.; Rohlfing, G.; Ulbrich, U.

    2009-04-01

    Extreme weather events such as thunderstorms, hail and heavy rain or snowfall can pose a threat to human life and to considerable tangible assets. Yet there is a lack of knowledge about present day climatological risk and its economic effects, and its changes due to rising greenhouse gas concentrations. Therefore, parts of economy particularly sensitve to extreme weather events such as insurance companies and airports require regional risk-analyses, early warning and prediction systems to cope with such events. Such an attempt is made for southern Germany, in close cooperation with stakeholders. Comparing ERA40 and station data with impact records of Munich Re and Munich Airport, the 90th percentile was found to be a suitable threshold for extreme impact relevant precipitation events. Different methods for the classification of causing synoptic situations have been tested on ERA40 reanalyses. An objective scheme for the classification of Lamb's circulation weather types (CWT's) has proved to be most suitable for correct classification of the large-scale flow conditions. Certain CWT's have been turned out to be prone to heavy precipitation or on the other side to have a very low risk of such events. Other large-scale parameters are tested in connection with CWT's to find out a combination that has the highest skill to identify extreme precipitation events in climate model data (ECHAM5 and CLM). For example vorticity advection in 700 hPa shows good results, but assumes knowledge of regional orographic particularities. Therefore ongoing work is focused on additional testing of parameters that indicate deviations of a basic state of the atmosphere like the Eady Growth Rate or the newly developed Dynamic State Index. Evaluation results will be used to estimate the skill of the regional climate model CLM concerning the simulation of frequency and intensity of the extreme weather events. Data of the A1B scenario (2000-2050) will be examined for a possible climate change

  1. Carbon balance of a drained forested bog in southern Finland

    NASA Astrophysics Data System (ADS)

    Minkkinen, Kari; Penttilä, Timo; Ojanen, Paavo; Lohila, Annalea

    2016-04-01

    Carbon and greenhouse gas (GHG) dynamics of a drained forested peatland in southern Finland were measured over multiple years, including one with severe drought during growing season. Net ecosystem carbon dioxide exchange (NEE) was measured with an eddy covariance method from a tower above the forest. Soil and forest floor CO2, CH4 and N2O fluxes were measured from the strips and from ditches with closed chambers. Biomasses and litter production were sampled, and soil subsidence was measured by consequtive levelings of the peat surface. The data were used to estimate the ecosystem C pools and annual fluxes of carbon and GHGs of the peatland and to analyse the impact of periodical drought on the carbon fluxes. The drained peatland was a strong sink of carbon dioxide in all studied years. Soil CO2 balance was estimated by subtracting the carbon sink of the growing tree stand from NEE, and it showed that also the soil was a sink of carbon in all studied years. A drought period in one summer significantly decreased the sink through decreased GPP. Drought also decreased the ecosystem respiration, including soil respiration. Decreasing water table thus did not increase, but rather decreased CO2 efflux from the peat soil. The site was a small sink for CH4, even when emissions from ditches were included. N2O emissions were small from all surfaces. Despite of the continuous carbon sink, peat surface subsided slightly (1.4 mm a-1) during the 10-year measurement period, which is interpreted to mean mainly compaction, rather than oxidation of the peat. It is concluded that this drained peatland acts as a continuous soil C sink similarly to an undrained peatland. The reason may be the relatively small water-level drawdown compared to an undrained situation, the consequently rather small changes in plant community structure and the significantly improved tree stand growth and litter production. The consequences of continuing production forestry vs. restoration of the site on the

  2. 14C-dead living biomass: evidence for microbial assimilation of ancient organic carbon during shale weathering.

    PubMed

    Petsch, S T; Eglington, T I; Edwards, K J

    2001-05-11

    Prokaryotes have been cultured from a modern weathering profile developed on a approximately 365-million-year-old black shale that use macromolecular shale organic matter as their sole organic carbon source. Using natural-abundance carbon-14 analysis of membrane lipids, we show that 74 to 94% of lipid carbon in these cultures derives from assimilation of carbon-14-free organic carbon from the shale. These results reveal that microorganisms enriched from shale weathering profiles are able to use a macromolecular and putatively refractory pool of ancient organic matter. This activity may facilitate the oxidation of sedimentary organic matter to inorganic carbon when sedimentary rocks are exposed by erosion. Thus, microorganisms may play a more active role in the geochemical carbon cycle than previously recognized, with profound implications for controls on the abundance of oxygen and carbon dioxide in Earth's atmosphere over geologic time.

  3. The importance of terrestrial weathering changes in multimillennial recovery of the global carbon cycle: a two-dimensional perspective

    NASA Astrophysics Data System (ADS)

    Brault, Marc-Olivier; Damon Matthews, H.; Mysak, Lawrence A.

    2017-06-01

    In this paper, we describe the development and application of a new spatially explicit weathering scheme within the University of Victoria Earth System Climate Model (UVic ESCM). We integrated a dataset of modern-day lithology with a number of previously devised parameterizations for weathering dependency on temperature, primary productivity, and runoff. We tested the model with simulations of future carbon cycle perturbations, comparing a number of emission scenarios and model versions with each other and with zero-dimensional equivalents of each experiment. Overall, we found that our two-dimensional weathering model versions were more efficient in restoring the carbon cycle to its pre-industrial state following the pulse emissions than their zero-dimensional counterparts; however, in either case the effect of this weathering negative feedback on the global carbon cycle was small on timescales of less than 1000 years. According to model results, the largest contribution to future changes in weathering rates came from the expansion of tropical and mid-latitude vegetation in grid cells dominated by weathering-vulnerable rock types, whereas changes in temperature and river runoff had a more modest direct effect. Our results also confirmed that silicate weathering is the only mechanism that can lead to a full recovery of the carbon cycle to pre-industrial levels on multimillennial timescales.

  4. Soil Atterberg limits of different weathering profiles of the collapsing gullies in the hilly granitic region of southern China

    NASA Astrophysics Data System (ADS)

    Deng, Yusong; Cai, Chongfa; Xia, Dong; Ding, Shuwen; Chen, Jiazhou; Wang, Tianwei

    2017-04-01

    Collapsing gullies are one of the most serious soil erosion problems in the tropical and subtropical areas of southern China. However, few studies have been performed on the relationship of soil Atterberg limits with soil profiles of the collapsing gullies. Soil Atterberg limits, which include plastic limit and liquid limit, have been proposed as indicators for soil vulnerability to degradation. Here, the soil Atterberg limits within different weathering profiles and their relationships with soil physicochemical properties were investigated by characterizing four collapsing gullies in four counties in the hilly granitic region of southern China. The results showed that with the fall of weathering degree, there was a sharp decrease in plastic limit, liquid limit, plasticity index, soil organic matter, cation exchange capacity and free iron oxide. Additionally, there was a gradual increase in liquidity index, a sharp increase in particle density and bulk density followed by a slight decline, a decrease in the finer soil particles, a noticeable decline in the clay contents, and a considerable increase in the gravel and sand contents. The plastic limit varied from 19.43 to 35.93 % in TC, 19.51 to 33.82 % in GX, 19.32 to 35.58 % in AX and 18.91 to 36.56 % in WH, while the liquid limit varied from 30.91 to 62.68 % in TC, 30.89 to 57.70 % in GX, 32.48 to 65.71 % in AX and 30.77 to 62.70 % in WH, respectively. The soil Atterberg limits in the sandy soil layers and detritus layers were lower than those in the surface layers and red soil layers, which results in higher vulnerability of the sandy soil layers and detritus layers to erosion and finally the formation of the collapsing gully. The regression analyses showed that soil Atterberg limits had significant and positive correlation with SOM, clay content, cationic exchange capacity and Fed, significant and negative correlation with sand content and no obvious correlation with other properties. The results of this study

  5. Space and Time Variability of the Southern Ocean Carbon Budget

    NASA Astrophysics Data System (ADS)

    Rosso, I.; Mazloff, M. R.; Verdy, A.; Talley, L. D.

    2016-12-01

    The upper ocean dissolved inorganic carbon (DIC) concentration is regulated by advective and diffusive transport divergence, biological processes, and CO2 and fresh water fluxes. The relative importance of these mechanisms in the Southern Ocean are uncertain, as observations in this area have been limited. A biogeochemical-sea ice-ocean model of the Southern Ocean, run at 1/3 degree resolution, is used to investigate the drivers of the change in DIC concentration between January 2006 and December 2014.We find that advective transport governs the local upper ocean (down to 650 m) DIC budget on all time scales. Other components are influential, however, in setting the interannual variability: in particular, biological production in western boundary currents, at large topographic features (such as the Kerguelen Plateau) and in the Weddell and Ross gyres, or sea ice processes in Antarctic regions. For regional budgets, advection is less influential: in subpolar gyres biology and dilution shape the seasonal cycle, whereas air-sea exchanges are a primary driver of DIC changes in the subtropics. Meanwhile, all processes have a significant impact on the DIC budget in the ACC, with topographic features influencing the relative importance of advection, biological mechanisms and air-sea flux.

  6. Chrome spinels and accessory mineralization in the weathering crust of the Vladimir deposit, Varshavsky ultramafic massif, southern Urals

    NASA Astrophysics Data System (ADS)

    Ankushev, M. N.; Zaykov, V. V.; Kotlyarov, V. A.; Romanenko, M. E.

    2016-12-01

    The paper presents the characteristics of chrome spinels from an ore-bearing packet of the Vladimir chromite deposit. Three main types of chrome spinels are distinguished by morphology and chemical composition: medium-chrome ore-forming, high-chrome transformed, and low-chrome relict accessory. The significant role of weathering conditions is expressed in alteration of accessory chrome spinel. The formation of high-chrome spinels is explained by the hydrothermal effect of the Varshavsky granitoid massif with accompanying dikes and talc-carbonate metasomatic rocks. Characteristic accessory minerals are represented by native gold and nickel, millerite, pentlandite, chalcopyrite, maucherite, PGE sulfides, and picroilmenite.

  7. The effect of an exchanger phase, carbon dioxide, and mineralogy on the rate of geochemical weathering

    SciTech Connect

    Amrhein, C.

    1984-01-01

    The dissolution (weathering) of soil minerals can have an appreciable effect on soil water chemistry. The rate at which mineral dissolution in water approaches equilibrium is dependent upon the type of minerals present, the surface area/solution volume ratio, the ionic composition of the solution, the nature of the exchanger phase of the soil, the temperature and the local partial pressure of carbon dioxide. Geochemical weathering has an important effect on the processes relating to sodic soil reclamation, nutrient availability, soil genesis, management of overburden materials from mining activities, and salt loading to surface and ground waters. Research was conducted to determine, quantitatively, the effects of CO{sub 2} and exchanger phase composition on the kinetics of calcium mineral dissolution. It was found that the presence of exchangeable sodium greatly increased the initial rate of mineral dissolution by acting to keep the soil solution low in Ca{sup 2+} ions. The kinetics of calcite dissolution were controlled by the gas transfer reaction, CO{sub 2}(gas) {yields} CO{sub 2}(ag), at CO{sub 2} levels below .03 atmospheres. A mechanistic kinetic model was proposed that included the CO{sub 2} reaction kinetics and an adsorption/hydration reaction with the calcite surface. In general, mineral weathering was found to rarely obey a diffusion controlled model and was better described by mechanistic kinetics invoking elementary chemical reactions. In addition, it was found that the weathering rate of anorthite (a calcium silicate) was too slow to contribute significant amounts of Ca{sup 2+} ions to the soil solution and the phenomenon of calcite supersaturation commonly found in soil solutions is attributed to carbon dioxide dynamics.

  8. Mesocosm-Scale Experimental Quantification of Plant-Fungi Associations on Carbon Fluxes and Mineral Weathering

    NASA Astrophysics Data System (ADS)

    Andrews, M. Y.; Palmer, B.; Leake, J. R.; Banwart, S. A.; Beerling, D. J.

    2009-12-01

    The rise of land plants in the Paleozoic is classically implicated as driving lower atmospheric CO2 levels through enhanced weathering of Ca and Mg bearing silicate minerals. However, this view overlooks the fact that plants coevolved with associated mycorrhizal fungi over this time, with many of the weathering processes usually ascribed to plants actually being driven by the combined activities of roots and mycorrhizal fungi. Here we present initial results from a novel mesocosm-scale laboratory experiment designed to allow investigation of plant-driven carbon flux and mineral weathering at different soil depths under ambient (400 ppm) and elevated (1500 ppm) atmospheric CO2. Four species of plants were chosen to address evolutionary trends in symbiotic mycorrhizal association and rooting depth on biologically driven silicate weathering under the different CO2 regimes. Gymnosperms were used to investigate potential differences in weathering capabilities of two fungal symbioses: Sequoia sempervirens and Metasequoia glyptostroboides (arbuscular mycorrhizal, AM) and Pinus sylvestris (ectomycorrhizal, EM), and the shallow rooted ancient fern, Osmunda regalis, used to provide a contrast to the three more deeply rooted trees. Plants were grown in a cylindrical mesocosm with four horizontal inserts at each depth. These inserts are a mesh-covered dual-core unit whereby an inner core containing silicate minerals can be rotated within an outer core. The mesh excludes roots from the cylinders allowing fungal-rock pairings to be examined at each depth. Each core contains either basalt or granite, each with severed (rotated cores) or intact (static cores) mycorrhizae. This system provides a unique opportunity to examine the ability of a plant to weather minerals with and without its symbiotic fungi. Preliminary results indicate marked differences in nutritional and water requirements, and response to elevated CO2 between the species. The bulk solution chemistries (p

  9. Seasonal weather, nutrients, and conspecific presence impacts on the southern house mosquito oviposition dynamics in combined sewage overflows.

    PubMed

    Nguyen, An T; Williams-Newkirk, Amanda J; Kitron, Uriel D; Chaves, Luis F

    2012-11-01

    Combined sewage overflows have created favorable conditions for the establishment of the southern house mosquito, Culex quinquefasciatus Say (Diptera: Culicidae), larvae in natural creeks that would otherwise be unsuitable for the development of this mosquito species. Here, we show the results from a seminatural experiment carried over the three seasons of mosquito activity (spring, summer, and fall) in Tanyard Creek, Atlanta, GA. In this study we manipulated the amount of nutrients by further enriching combined sewage overflow water, and tracked weather variables, organic nutrient concentration, exposure time to conspecifics, and the number of egg rafts collected in experimental containers. We found season and nutrient enrichment to be the most important variables explaining the differences in egg rafts counts. Further analyses suggest that temperature may also play a role in seasonal oviposition patterns. The results from this study suggest that nutrient enrichment and adequate temperatures are important factors shaping Cx. quinquefasciatus oviposition seasonality in combined sewage overflows.

  10. Silicate versus carbonate weathering in Iceland: New insights from Ca isotopes

    NASA Astrophysics Data System (ADS)

    Jacobson, Andrew D.; Grace Andrews, M.; Lehn, Gregory O.; Holmden, Chris

    2015-04-01

    Several studies have measured riverine fluxes of Ca and carbonate alkalinity in Iceland with the aim of quantifying the role of basalt weathering in the long-term carbon cycle. A major assumption is that all of the Ca and alkalinity originates from the dissolution of Ca-bearing silicate minerals, such as plagioclase and clinopyroxene. However, hydrothermal calcite occurs throughout Iceland, and even trace levels are expected to impact river geochemistry owing to the mineral's high solubility and fast dissolution rate. To test this hypothesis, we used a new, high-precision Ca isotope MC-TIMS method (δ44/40Ca; 2σSD = ± 0.04 ‰) to trace sources of Ca in Icelandic rivers. We report elemental and Ca isotope data for rivers, high- and low-temperature groundwater, basalt, hydrothermal calcite (including Iceland Spar), and stilbite and heulandite, which are two types of zeolites commonly formed during low-grade metamorphism of basalt. In agreement with previous research, we find that rivers have higher δ44/40Ca values than basalt, with a maximum difference of ∼0.40‰. This difference may reflect isotope fractionation in the weathering zone, i.e., preferential uptake of 40Ca during clay mineral formation, adsorption, and other geochemical processes that cycle Ca. However, calcite δ44/40Ca values are also up to ∼0.40‰ higher than bedrock values, and on a diagram of δ44/40Ca versus Sr/Ca, nearly all waters plot within a plausible mixing domain bounded by the measured compositions of basalt and calcite, with glacial rivers plotting closer to calcite than non-glacial rivers. Calcite and heulandite form during hydrothermal alteration of basalt in the deep lava pile and often occur together in metabasalts now exposed at the surface. Because heulandite δ44/40Ca values are ∼1-2‰ lower than basalt, we suggest that 40Ca uptake by heudlandite explains the relatively high δ44/40Ca values of calcite and that calcite weathering in turn elevates riverine δ44/40Ca

  11. Neogene weathering and terrestrial sedimentation in southern New Caledonia; inference on post-obduction tectonics and climate change

    NASA Astrophysics Data System (ADS)

    Folcher, Nicolas; Ricordel-Prognon, Caroline; Sevin, Brice; Maurizot, Pierre; Cluzel, Dominique; Quesnel, Florence

    2014-05-01

    Iron-rich sediments that fill up karst-like depressions and paleo-valleys in southern New Caledonia are mainly composed of re-sedimented laterite and saprolite. These fluvial sediments come from the erosion of an older regolith that developed upon peridotites and gabbros of the Peridotite Nappe during Late Oligocene times. At the bottom, conglomeratic facies fill incised valleys and contain some metre-size cobbles of ferricrete that record dissection of pre-existing weathering profiles and were deposited in alluvial fan environment. The basal conglomerate is overlain by sand, then dominantly silty fluvial sediments 40 to 50 m thick, with a few thin conglomerate channels. Brutal grain size reduction suggests that erosion was short-lived and followed by quiescence. Multiple interbedded ferruginous duricrusts and rhizocretions made of goethite (and secondary hematite) and liesegang rings reveal iron mobility and several iron oxi-hydroxides concretion/ cementation episodes alternating with sedimentation, probably as a consequence of water table variations. The top of the succession is overlain by a weathering profile and capped by a nodular lateritic ferricrete. Finally, reactivated erosion profoundly incised the fluvial succession and locally reached the bedrock which today crops out upstream along the main river beds. In southern New Caledonia some ferricretes and ferruginous duricrusts have been dated at -25 Ma and -20 to -10 Ma by paleomagnetic method (in progress). They could be correlated to some warming events of the Late Oligocene and Early Miocene or to the Middle Miocene Climatic Optimum. Erosion that predates the accumulation of terrestrial sediments may be tentatively correlated to the uplift that accompanied the emplacement of the Saint-Louis and Koum plutons, and some internal dissection episodes could be related to the Lower Miocene post-obduction slab break off. The final erosion is most probably related to the southward tilt of New Caledonia due to

  12. Serpentinite Carbonation in the Pollino Massif (southern Italy) for CO2 Sequestration

    NASA Astrophysics Data System (ADS)

    Carmela Dichicco, Maria; Mongelli, Giovanni; Paternoster, Michele; Rizzo, Giovanna

    2015-04-01

    Anthropogenic gas emissions are projected to change future climates with potentially nontrivial impacts (Keller et al., 2008 and references therein) and the impacts of the increased CO2 concentration are, among others, the greenhouse effect, the acidification of the surface of the ocean and the fertilization of ecosystems (e.g. Huijgen and Comans, 2003). Geologic Sequestration into subsurface rock formations for long-term storage is part of a process frequently referred to as "carbon capture and storage" or CCS. A major strategy for the in situ geological sequestration of CO2 involves the reaction of CO2 with Mg-silicates, especially in the form of serpentinites, which are rocks: i) relatively abundant and widely distributed in the Earth's crust, and ii) thermodynamically convenient for the formation of Mg-carbonates (e.g., Brown et al., 2011). In nature, carbonate minerals can form during serpentinization or during hydrothermal carbonation and weathering of serpentinites whereas industrial mineral carbonation processes are commonly represented by the reaction of olivine or serpentine with CO2 to form magnesite + quartz ± H2O (Power et al., 2013). Mineral carbonation occurs naturally in the subsurface as a result of fluid-rock interactions within serpentinite, which occur during serpentinization and carbonate alteration. In situ carbonation aims to promote these reactions by injecting CO2 into porous, subsurface geological formations, such as serpentinite-hosted aquifers. In the northern sector of the Pollino Massif (southern Italy) extensively occur serpentinites (Sansone et. al., 2012) and serpentinite-hosted aquifers (Margiotta et al., 2012); both serpentinites and serpentinite-hosted aquifers are the subject of a comprehensive project devoted to their possible use for in situ geological sequestration of CO2. The serpentinites derived from a lherzolitic and subordinately harzburgitic mantle, and are within tectonic slices in association with metadolerite dykes

  13. Ecosystem Greenhouse Gas Fluxes Respond Directly to Weather Not Climate: A Case Study on the Relationship of Global Atmospheric Circulation, Foehn Frequency, and Winter Weather to Northern Alps Regional Grassland Phenology and Carbon Cycling

    NASA Astrophysics Data System (ADS)

    Desai, A. R.; Wohlfahrt, G.; Zeeman, M. J.; Katata, G.; Mauder, M.; Schmid, H. P. E.

    2014-12-01

    The impact of climate change on regional ecosystem structure and biogeochemical cycling has two important aspects that require better elaboration to improve projections of these effects. The first is that ecosystems don't respond directly to climate, but indirectly via frequency and occurrence of weather systems, which are driven by climatic shifts in global circulation and radiative processes. The second is that many responses of ecosystems to these weather patterns and extremes are lagged in time. Here, we examine these aspects for northern Alpine grasslands. Long-term eddy covariance flux tower and phenology observations in Austria and Germany and biophysical models reveal a strong influence of winter air temperature, snowfall, and snowmelt frequency on winter grass mortality and spring grassland carbon uptake. Further, the mode of climate variability that drives winter air temperature and snow depth patterns is primarily the frequency of strong regional southerly Foehn flow that promotes warm, dry conditions in winter. Finally, we demonstrate that much of the interannual variance in Foehn frequency and southerly flow is driven by statistics and climatic trends of 500 hPa pressure patterns in Greenland, part of the Arctic Oscillation. However, a few years, including the unusually warm and dry winter of 2013-2014 appear to have secondary, possibly local thermotopographic circulation factors that promoted its weather conditions regionally, which also included primarily cool and wet conditions in northern Europe and the southern Alps. These findings demonstrate that the regional response of ecosystems to climate change is modulated by how large-scale circulation patterns influence local meteorology and topographic flows both during and outside the growing season and provides a framework for future assessment and climate model improvements of linkages of climate change, weather patterns, and ecosystem responses.

  14. Evaluation of the dry and wet weather recreational health risks in a semi-enclosed marine embayment in Southern California.

    PubMed

    Lim, Keah-Ying; Shao, Stella; Peng, Jian; Grant, Stanley B; Jiang, Sunny C

    2017-03-15

    For many coastal regions around the world, recreational beach water quality is assessed using fecal indicator bacteria (FIB). However, the utility of FIB as indicators of recreational water illness (RWI) risk has been questioned, particularly in coastal settings with no obvious sources of human sewage. In this study we employed a source-apportionment quantitative microbial risk assessment (SA-QMRA) to assess RWI risk at a popular semi-enclosed recreational beach in Southern California (Baby Beach, City of Dana Point) with no obvious point sources of human sewage. Our SA-QMRA results suggest that, during dry weather, the median RWI risk at this beach is below the U.S. EPA recreational water quality criteria (RWQC) of 36 illness cases per 1000 bathers. During wet weather, the median RWI risk predicted by SA-QMRA depends on the assumed level of human waste associated with stormwater; the RWI risk is below the EPA RWQC illness risk benchmark 100% of the time provided that <2% of the FIB in stormwater are of human origin. However, these QMRA outcomes contrast strongly with the EPA RWQC for 30-day geometric mean of enterococci bacteria. Our results suggest that SA-QMRA is a useful framework for estimating robust RWI risk that takes into account local information about possible human and non-human sources of FIB.

  15. Comparison of the pollutant loads in dry and wet weather runoff in a southern California urban watershed.

    PubMed

    McPherson, T N; Burian, S J; Turin, H J; Stenstrom, M K; Suffet, I H

    2002-01-01

    This research compares the relative contributions of potential contaminants discharged in dry weather flow (DWF) and wet weather flow (WWF) from the highly urbanized Ballona Creek watershed (BCW) in southern California using empirical and deterministic models. These models were used to compare the loading of the following pollutants: total suspended solids, biochemical oxygen demand, total nitrogen, total inorganic nitrogen, total Kjeldahl nitrogen, total phosphorus, copper, lead, arsenic, nickel, cadmium, and chromium. The results indicate DWF contributes approximately 10-30% of the total annual flow discharged from Ballona Creek. The annual DWF volume was fairly consistent; the variation in DWF percentage contribution was dependent on the highly variable volume of WWF. The relative contribution to the annual pollutant load varied considerably between each pollutant. In general, the DWF load was found to be significant, especially in years with lower precipitation totals. The results from this investigation have identified the relative relationship between DWF and WWF loads in the BCW and will aid in the decision-making process during the development of an integrated DWF-WWF management plan and allocation of water pollution control funds between DWF and WWF management.

  16. Deep critical zone weathering at the southern Sierra Nevada Critical Zone Observatory imaged by seismic waveform tomography

    NASA Astrophysics Data System (ADS)

    Hayes, J. L.; Holbrook, W.; Riebe, C. S.

    2012-12-01

    We present seismic velocity profiles that constrain the extent of weathering and frequency of velocity heterogeneities at depths less than 40 m in the southern Sierra Nevada Critical Zone Observatory (SSCZO) from waveform tomography modeling of a seismic refraction experiment. Near-surface variations in seismic velocity reflect differences in alteration of parent material by chemical, hydrological and biological processes. Previous traveltime tomography models from these data suggest that the depth to bedrock in the SSCZO is typically ~25 m; thus the potential for subsurface water storage in regolith may be a larger component of water storage than previously thought. Traveltime tomography is unable to resolve heterogeneities with horizontal wavelengths less than 10 m, such as those observed along a surveyed road cut beneath our seismic profile. For a higher resolution seismic image, we apply waveform tomography, which is more robust than traveltime tomography at approximating the wave equation and thus should provide images of subsurface heterogeneities such as corestones and fracture networks. This technique uses a weak scattering approximation to account for the amplitude and phase of the recorded waveforms, rather than just the traveltimes. A 48-channel vertical geophone array and hammer source was deployed over a 7 m high road cut with receiver and shot spacing of 2 m and 4 m respectively. The road cut displays lateral variation in weathering from a friable saprolite to coherent granodiorite which are compared to velocity variations modeled using waveform tomography.

  17. Acid rock drainage and rock weathering in Antarctica: important sources for iron cycling in the Southern Ocean.

    PubMed

    Dold, B; Gonzalez-Toril, E; Aguilera, A; Lopez-Pamo, E; Cisternas, M E; Bucchi, F; Amils, R

    2013-06-18

    Here we describe biogeochemical processes that lead to the generation of acid rock drainage (ARD) and rock weathering on the Antarctic landmass and describe why they are important sources of iron into the Antarctic Ocean. During three expeditions, 2009-2011, we examined three sites on the South Shetland Islands in Antarctica. Two of them displayed intensive sulfide mineralization and generated acidic (pH 3.2-4.5), iron-rich drainage waters (up to 1.78 mM Fe), which infiltrated as groundwater (as Fe(2+)) and as superficial runoff (as Fe(3+)) into the sea, the latter with the formation of schwertmannite in the sea-ice. The formation of ARD in the Antarctic was catalyzed by acid mine drainage microorganisms found in cold climates, including Acidithiobacillus ferrivorans and Thiobacillus plumbophilus. The dissolved iron (DFe) flux from rock weathering (nonmineralized control site) was calculated to be 0.45 × 10(9) g DFe yr(-1) for the nowadays 5468 km of ice-free Antarctic rock coastline which is of the same order of magnitude as glacial or aeolian input to the Southern Ocean. Additionally, the two ARD sites alone liberate 0.026 and 0.057 × 10(9) g DFe yr(-1) as point sources to the sea. The increased iron input correlates with increased phytoplankton production close to the source. This might even be enhanced in the future by a global warming scenario, and could be a process counterbalancing global warming.

  18. Major, trace and REE geochemistry in contrasted chlorite schist weathering profiles from southern Cameroon: Influence of the Nyong and Dja Rivers water table fluctuations in geochemical evolution processes

    NASA Astrophysics Data System (ADS)

    Onana, Vincent Laurent; Ntouala, Roger Firmin Donald; Tang, Sylvie Noa; Effoudou, Estelle Ndome; Kamgang, Veronique Kabeyene; Ekodeck, Georges Emmanuel

    2016-12-01

    Three weathering profiles developed on chlorite schists, formations on which little studies have been conducted, were chosen to understand the weathering processes prevailing downslope in Southern Cameroon. The materials nearest to Nyong River at Ayos weather under the influence of the fluctuations of groundwater table and acid rain, while those from Bengbis and Mbalmayo weather under the influence of acid rain. The result is the thickening of materials and weathering profiles, without formation of a nodular ferruginous horizon at Ayos. The Ayos weathered materials (CIA ∼ 92) are the most altered and the least lateritised (IOL ∼ 32). The most stable systems are Hf - U - Nb - Ti - Zr - Mo - W (Bengbis), Yb - U - Nb - Ti - Zr - Hf - Mo - W - Th (Mbalmayo) and Th - Nb - Zr - Hf - Mo - Ta (Ayos). Molybdenum accumulations are important in the studied materials. Uranium accumulations are found only in Mbalmayo. Coarse saprolitic materials at Ayos are the most depleted and fractionated in REE ((La/Yb)N = 0.07, Ce/Ce* = 2.24), while superficial clayey materials are less fractionated. This process is reversed at Bengbis and Mbalmayo. By contrast, weathered materials at Ayos do not show any Eu anomalies (as in Bengbis and Mbalmayo). Weathered materials from Bengbis, nearest to the Dja River, have (La/Yb)N < 1 ratios, indicating the relative immobility of HREE relative to LREE due to xenotime abnormally rich in HREE (HREE-PO4). Weak Ce anomalies (1.05-2.24) are ubiquitous in all the studied materials.

  19. The effects of weather conditions on measles incidence in Guangzhou, Southern China

    PubMed Central

    Yang, Qiongying; Fu, Chuanxi; Wang, Naizhen; Dong, Zhiqiang; Hu, Wensui; Wang, Ming

    2014-01-01

    Background: Few studies were conducted to examine the effects of weather conditions on the incidence of measles. Methods: We used a distributed lag non-linear model (DLNM) to analyze the relationship between meteorological factors and measles incidence in Guangzhou, China. Results: Nonlinear effects of temperature and relative humidity on measles incidence were observed. The relative risk (RR) for the measles incidence associated with the 75th percentile of mean temperature (27.9 °C) relative to the median of mean temperature (24.7 °C) was 1.00 (0.86,1.16) for lags 0–10 days. The RR for the measles incidence associated with the 25th percentile of relative humidity (64%) relative to the median of relative humidity (73%) was 1.36 (1.01,1.82) for lags 0–30 days. The wet effects and dry effects were larger in females than in males. The wet effects were generally increased with ages. Significantly negative effects of cold spells on measles incidence were observed. Conclusion: Both hot and cold temperatures result in decreases in the incidence of measles, and low relative humidity is a risk factor of measles morbidity. An increased number of measles cases might occur before and after a cold spell. Our findings highlight the need to pay more attention to the weather transformation and improve the immunity of susceptible population for measles elimination. Catch-up vaccination campaigns should be initiated among young adults. PMID:24509358

  20. The effects of weather conditions on measles incidence in Guangzhou, Southern China.

    PubMed

    Yang, Qiongying; Fu, Chuanxi; Dong, Zhiqiang; Hu, Wensui; Wang, Ming

    2014-01-01

    Few studies were conducted to examine the effects of weather conditions on the incidence of measles. We used a distributed lag nonlinear model (DLNM) to analyze the relationship between meteorological factors and measles incidence in Guangzhou, China. Nonlinear effects of temperature and relative humidity on measles incidence were observed. The relative risk (RR) for the measles incidence associated with the 75th percentile of mean temperature (27.9 °C) relative to the median of mean temperature (24.7 °C) was 1.00 (0.86,1.16) for lags 0-10 days. The RR for the measles incidence associated with the 25th percentile of relative humidity (64%) relative to the median of relative humidity (73%) was 1.36 (1.01,1.82) for lags 0-30 days. The wet effects and dry effects were larger in females than in males. The wet effects were generally increased with ages. Significantly negative effects of cold spells on measles incidence were observed. Both hot and cold temperatures result in decreases in the incidence of measles, and low relative humidity is a risk factor of measles morbidity. An increased number of measles cases might occur before and after a cold spell. Our findings highlight the need to pay more attention to the weather transformation and improve the immunity of susceptible population for measles elimination. Catch-up vaccination campaigns should be initiated among young adults.

  1. Lithium and carbon isotopes in river catchment: combined tracers to constrain chemical weathering processes

    NASA Astrophysics Data System (ADS)

    Rad, S.; Rive, K.; Assayag, N.; Dictor, M.; Garcin, M.

    2012-12-01

    Water-rock interactions produced in river catchment are accompanied by fractionation or changes in stable isotopes such as H, Li, C and O during chemical weathering processes. Li is a fluid-mobile element that tends to preferentially partition into the fluid phase during water-rock interaction. The relative mass difference between the two isotopes is considerable, generating large mass dependent fractionation during chemical weathering processes. The CO2 dissolves into the water providing the main acid that attack the rock during chemical weathering. Carbon stable isotopes and concentration of Dissolved Inorganic Carbon (DIC) in the river catchment can be used to determine the origin and consumption rates of CO2. In the present work, stable isotopes were analyzed in Allier River, one of the major river basins of France. The lithology is dominated by granite rocks within current upstream, while it is mainly basaltic and Oligocene sediments in the downstream with hydrothermal manifestations. We propose a new isotopic approach by combining δ7Li and δ13CDIC analyses in river catchment waters. A first method has been applied to volcanic tropical environments with Li concentrations correlated to δ13CDIC (Rad et al., 2011). Here, we have completed this approach by lithium isotopes. Water samples were collected during several field trips. Our results show a large variation in Li isotopes and C isotopes within the catchment from 3.3 ‰ to 30.3 ‰ and from -17.9‰ to -3.5‰, respectively. Chemical weathering rates linearly increase from upstream to downstream over 400km distance, whereas Li isotope signatures decrease and global C signature increases. This is due to low water-rock interaction dominated in upstream, whereas the downstream is punctually impacted by hydrothermalism. From Li and C isotopes, our results show 4 groups reflecting different chemical weathering processes: the first group with high fractionation of Li and C, for Li, the heavy lithium

  2. Precipitation pulse dynamics of carbon sequestration and efflux in highly weatherable soils

    NASA Astrophysics Data System (ADS)

    Barron-Gafford, G.; Minor, R.; Van Haren, J. L.; Dontsova, K.; Troch, P. A.

    2013-12-01

    Soils are the primary pool for terrestrial carbon on Earth, and loss of that carbon to the atmosphere or hydrosphere represents a significant efflux that can impact a host of other downstream processes. Soil respiration (Rsoil), the efflux of CO2 to the atmosphere, represents the major pathway by which carbon is lost from the soil system in more weathered soils. However, in newly formed soils, chemical weathering can significantly deplete soil CO2 concentrations. As vegetation colonizes these soils, multiple interacting and contradictory pathways evolve such that soil CO2 concentrations increase in response to plant inputs but are decreased through chemical reactions. Furthermore, abiotic drivers of soil temperature and moisture likely differentially affect these processes. Understanding the bio-geo-chemical drivers and feedbacks associated with soil CO2 production and efflux in the critical zone necessitates an integrated science approach, drawing on input from plant physiologists, bio- and geochemists, and hydrologists. Here, we created a series of 1-meter deep mesocosms filled with granular basalt that supported either a woody mesquite shrub, a bunchgrass, or was left as bare soil. Use of multiple plant functional types allowed us to explore the impacts of plant structure (primarily rooting profiles) on critical zone function in terms of water and carbon exchange surrounding precipitation pulse dynamics. Each mesocosm was outfitted with an array of soil moisture, temperature, water potential, and CO2 concentration sensors at the near-surface, 30, 55, and 80cm depths to quantify patterns of soil moisture and respiratory CO2 efflux in response to rainfall events of varying magnitude and intervening periods of drought. Five replicates of each were maintained under current ambient or projected (+4oC) air temperatures. In addition, we used minirhizotrons to quantify the response of roots to episodic rainfall and confirm differences among plant types and collected

  3. Climate-change effects on soils: Accelerated weathering, soil carbon and elemental cycling

    SciTech Connect

    Qafoku, Nikolla

    2015-04-01

    Climate change [i.e., high atmospheric carbon dioxide (CO2) concentrations (≥400 ppm); increasing air temperatures (2-4°C or greater); significant and/or abrupt changes in daily, seasonal, and inter-annual temperature; changes in the wet/dry cycles; intensive rainfall and/or heavy storms; extended periods of drought; extreme frost; heat waves and increased fire frequency] is and will significantly affect soil properties and fertility, water resources, food quantity and quality, and environmental quality. Biotic processes that consume atmospheric CO2, and create organic carbon (C) that is either reprocessed to CO2 or stored in soils are the subject of active current investigations, with great concern over the influence of climate change. In addition, abiotic C cycling and its influence on the inorganic C pool in soils is a fundamental global process in which acidic atmospheric CO2 participates in the weathering of carbonate and silicate minerals, ultimately delivering bicarbonate and Ca2+ or other cations that precipitate in the form of carbonates in soils or are transported to the rivers, lakes, and oceans. Soil responses to climate change will be complex, and there are many uncertainties and unresolved issues. The objective of the review is to initiate and further stimulate a discussion about some important and challenging aspects of climate-change effects on soils, such as accelerated weathering of soil minerals and resulting C and elemental fluxes in and out of soils, soil/geo-engineering methods used to increase C sequestration in soils, soil organic matter (SOM) protection, transformation and mineralization, and SOM temperature sensitivity. This review reports recent discoveries, identifies key research needs, and highlights opportunities offered by the climate-change effects on soils.

  4. Impact of surface processes and climate variability on clumped isotope thermometry of soil carbonates, southern Central Andes, Argentina (Invited)

    NASA Astrophysics Data System (ADS)

    Huntington, K. W.; Peters, N.; Roe, G.; Hoke, G. D.; Eiler, J.

    2010-12-01

    Soil carbonates archive a potentially rich record of past climate, but rates of pedogenic carbonate formation, erosion, and deposition impact how the isotopic composition and formation temperature of carbonate-bearing paleosols reflect the local environmental conditions under which they form. We investigate these processes using conventional stable isotope (δ18O and δ13C) and clumped isotope thermometry data for Quaternary pedogenic carbonates from the southern Central Andes at ~33°S, Argentina. The study area spans over 2 km of relief in the Río Mendoza and Río de las Cuevas valleys, accessing a range of mean annual temperature conditions and vegetative cover and exhibiting large seasonal variations in temperature, precipitation, and soil moisture. Variations in soil conditions influence carbonate precipitation and dissolution reactions and the rate and depth of pedogenic carbonate formation. Because soil temperature varies predictably as a function of depth in the soil and seasonal and secular variations in air temperature, clumped isotope thermometry of samples collected in soil pits offers a direct way to estimate the seasonality of pedogenic carbonate formation and potential biases in the long-term climate record. We explore potential complications due to the effects of radiative solar heating on the relationship between air and soil temperatures by examining clumped isotope thermometry results in the context of site-to-site variations in vegetative cover. Temperature estimates from clumped isotope thermometry of pedogenic carbonate collected 5-110 cm below geomorphically stable soil surfaces from 1200-3400 m a.s.l. are compared to temperature profiles predicted by simple rule-based models of soil carbonate formation. The models use climate reanalysis daily diagnostic data (soil temperature, soil moisture, and latent heat flux as a proxy for evaporation) and weather station data as input to assess how varying rates of pedogenic carbonate formation

  5. Iron defecation by sperm whales stimulates carbon export in the Southern Ocean.

    PubMed

    Lavery, Trish J; Roudnew, Ben; Gill, Peter; Seymour, Justin; Seuront, Laurent; Johnson, Genevieve; Mitchell, James G; Smetacek, Victor

    2010-11-22

    The iron-limited Southern Ocean plays an important role in regulating atmospheric CO(2) levels. Marine mammal respiration has been proposed to decrease the efficiency of the Southern Ocean biological pump by returning photosynthetically fixed carbon to the atmosphere. Here, we show that by consuming prey at depth and defecating iron-rich liquid faeces into the photic zone, sperm whales (Physeter macrocephalus) instead stimulate new primary production and carbon export to the deep ocean. We estimate that Southern Ocean sperm whales defecate 50 tonnes of iron into the photic zone each year. Molar ratios of C(export):Fe(added) determined during natural ocean fertilization events are used to estimate the amount of carbon exported to the deep ocean in response to the iron defecated by sperm whales. We find that Southern Ocean sperm whales stimulate the export of 4 × 10(5) tonnes of carbon per year to the deep ocean and respire only 2 × 10(5) tonnes of carbon per year. By enhancing new primary production, the populations of 12 000 sperm whales in the Southern Ocean act as a carbon sink, removing 2 × 10(5) tonnes more carbon from the atmosphere than they add during respiration. The ability of the Southern Ocean to act as a carbon sink may have been diminished by large-scale removal of sperm whales during industrial whaling.

  6. Iron defecation by sperm whales stimulates carbon export in the Southern Ocean

    PubMed Central

    Lavery, Trish J.; Roudnew, Ben; Gill, Peter; Seymour, Justin; Seuront, Laurent; Johnson, Genevieve; Mitchell, James G.; Smetacek, Victor

    2010-01-01

    The iron-limited Southern Ocean plays an important role in regulating atmospheric CO2 levels. Marine mammal respiration has been proposed to decrease the efficiency of the Southern Ocean biological pump by returning photosynthetically fixed carbon to the atmosphere. Here, we show that by consuming prey at depth and defecating iron-rich liquid faeces into the photic zone, sperm whales (Physeter macrocephalus) instead stimulate new primary production and carbon export to the deep ocean. We estimate that Southern Ocean sperm whales defecate 50 tonnes of iron into the photic zone each year. Molar ratios of Cexport ∶Feadded determined during natural ocean fertilization events are used to estimate the amount of carbon exported to the deep ocean in response to the iron defecated by sperm whales. We find that Southern Ocean sperm whales stimulate the export of 4 × 105 tonnes of carbon per year to the deep ocean and respire only 2 × 105 tonnes of carbon per year. By enhancing new primary production, the populations of 12 000 sperm whales in the Southern Ocean act as a carbon sink, removing 2 × 105 tonnes more carbon from the atmosphere than they add during respiration. The ability of the Southern Ocean to act as a carbon sink may have been diminished by large-scale removal of sperm whales during industrial whaling. PMID:20554546

  7. Terrestrial sedimentation and the carbon cycle: coupling weathering and erosion to carbon burial

    USGS Publications Warehouse

    Stallard, R.F.

    1998-01-01

    This paper examines the linkages between the carbon cycle and sedimentary processes on land. Available data suggest that sedimentation on land can bury vast quantities of organic carbon, roughly 1015 g C yr-1. To evaluate the relative roles of various classes of processes in the burial of carbon on land, terrestrial sedimentation was modeled as a series of 864 scenarios. Each scenario represents a unique choice of intensities for seven classes of processes and two different global wetland distributions. Comparison was made with presumed preagricultural conditions. The classes of processes were divided into two major component parts: clastic sedimentation of soil-derived carbon and organic sedimentation of autochthonous carbon. For clastic sedimentation, masses of sediment were considered for burial as reservoir sediment, lake sediment, and combined colluvium, alluvium, and aeolian deposits. When the ensemble of models is examined, the human-induced burial of 0.6-1.5.1015 g yr-1 of carbon on land is entirely plausible. This sink reaches its maximum strength between 30 ?? and 50??N. Paddy lands stand out as a type of land use that warrants future study, but the many faces of rice agriculture limit generalization. In an extreme scenario, paddy lands alone could be made to bury about 1.1015 g C yr-1. Arguing that terrestrial sedimentation processes could be much of the sink for the so called 'missing carbon' is reasonable. Such a hypothesis, however, requires major redesign of how the carbon cycle is modeled. Unlike ecosystem processes that are amenable to satellite monitoring and parallel modeling, many aspects of terrestrial sedimentation are hidden from space.

  8. Estimations of Soil organic carbons pools in Southern Greenland

    NASA Astrophysics Data System (ADS)

    Ogric, Mateja; Chellasamy, Menaka; Knadel, Maria; Greve, Mogens H.; Adhikari, Kabindra; Jakobsen, Bjarne H.; Kristiansen, Søren M.

    2015-04-01

    Terrestrial areas hold large pools of soil organic carbon (SOC), which is a fundamental soil feature. It is known that SOC can be destabilized due to climate changes and land use, what can lead to accelerated emissions of greenhouse gasses into the atmosphere. Arctic soil, which is strongly sensitive to climate changes, stores about 14% of the Earth's organic carbon (Elberling et al., 2004). Therefore, the high-latitude soils are an important factor for investigation and determination of carbon pools. Recent advances in analytical methods offer various improvements regarding data acquisition. For example, near-infrared spectroscopy (NIRS) analyses of soils is often cost-effective and faster as compared to traditional wet-chemical methods for C and N determination, while it also gives reliable results. The aim of this study is i) to estimate the SOC pool in a remote area with poor soil data, i.e. Southern Greenland, and ii) to compare estimation techniques based on two independent SOC analytical approaches. The study area comprises approx. 17,500 km2 large non-glaciated land in south Greenland, from the Labrador Sea coast line to the margins of the Greenland Ice Sheet (46° 47'W-44° 16'W and 60° 07'N-61° 24'N). A large number of the abandoned Norse Viking Age settlements, i.e. Gardar, Hvalsø and Igaliku, are found here. A soil resource database was compiled from existing sources and recently collected soil samples to improve the data density for the area. The majority of the dataset represents 233 soil samples, which were collected in summer 2013 following Globalsoilmap.net specifications (Ogric et al., 2014). The focus of the investigation was on the top soil (down to 25 cm depth). These samples were analyzed for total soil carbon, nitrogen, and sulphur contents. The NIRS method was used on the same soil samples in an attempt to improve the data interpretation. Chemometric methods of NIRS data were applied with The Unscrambler X (Camo, 2014). Next, all known

  9. Weathering, mineralogical evolution and soil organic matter along a Holocene soil toposequence developed on carbonate-rich materials

    NASA Astrophysics Data System (ADS)

    Egli, Markus; Merkli, Christian; Sartori, Giacomo; Mirabella, Aldo; Plötze, Michael

    2008-05-01

    A toposequence of Holocene soils located between 1100-2400 m asl in the Italian Alps served as the basis for the following analyses: the weathering of limestone and dolomite, the calculation of mass balances, understanding the formation of pedogenic Fe and Al, the determination of soil mineral and clay mineral reactions and transformation and the measurement of accumulation and stabilisation mechanisms of soil organic matter. Leaching of carbonates is most intense at the lower elevations, although calcite and dolomite have a higher solubility at low temperatures. The pCO 2 in the soil is higher at lower elevations and weathering is driven mainly by carbonic acids. At higher elevations, organic acids appear to determine the mineral transformations and weathering reactions to a greater extent. This suggests that two very different weathering regimes (carbonic and organic acid weathering) exist along the toposequence. The transformation of mica into vermiculite is the main process in both the clay and fine-earth fraction. Weathering of silicate minerals started even before the carbonates had been completely removed from the soils. The transformation mechanisms of silicate minerals in the A and O horizon at higher elevations was at least as intensive as that at the climatically warmer sites. The neoformation of pedogenetic clays at climatically cooler sites was slightly greater than that at the warmer sites. However, the formation rate of secondary Fe and Al phases was more pronounced at lower elevation, which means that this process seemed to be driven dominantly by carbonic acid (weathering of primary minerals). Soil organic matter (SOM) abundance in the mineral soil is nearly 15 kg/m 2 at all sites and, surprisingly, no climate-driven effect could be detected. In general, the preservation and stabilisation of SOM was due to poorly crystalline Al and Fe phases and vermiculite, regardless of some variations in the composition of the parent material (varying calcite

  10. Weathering profiles in granitoid rocks of the Sila Massif uplands, Calabria, southern Italy: New insights into their formation processes and rates

    NASA Astrophysics Data System (ADS)

    Scarciglia, Fabio; Critelli, Salvatore; Borrelli, Luigi; Coniglio, Sabrina; Muto, Francesco; Perri, Francesco

    2016-05-01

    In this paper we characterized several weathering profiles developed on granitoid rocks in the Sila Massif upland (Calabria, southern Italy), integrating detailed macro- and micromorphological observations with physico-mechanical field tests and petrographic, mineralogical and geochemical analyses. We focused our attention on the main weathering and pedogenetic processes, trying to understand apparent discrepancies between weathering grade classes based on field description and geomechanical properties, and two common weathering indices, such as the micropetrographic index (Ip) and the chemical index of alteration (CIA). Our results showed that sericite on plagioclase and biotite chloritization, that represent inherited features formed during late-stage hydrothermal alteration of granitoid rocks, may cause an overestimation of the real degree of weathering of primary mineral grains under meteoric conditions, especially in lower weathering grade classes. Moreover, the frequent identification of Fe-Mn oxides and clay coatings of illuvial origin (rather than or in addition to those formed in situ), both at the macro- and microscale, may also explain an overestimation of the weathering degree with respect to field-based classifications. Finally, some apparent inconsistencies between field geomechanical responses and chemical weathering were interpreted as related to physical weathering processes (cryoclastism and thermoclastism), that lead to rock breakdown even when chemical weathering is not well developed. Hence, our study showed that particular caution is needed for evaluating weathering grades, because traditional field and geochemical-petrographic tools may be biased by inherited hydrothermal alteration, physical weathering and illuvial processes. On the basis of chronological constraints to soil formation obtained from a 42 ka-old volcanic input (mixed to granite parent materials) detected in the soil cover of the Sila Massif upland, a first attempt to estimate

  11. Stable carbon isotopes in dissolved inorganic carbon: extraction and implications for quantifying the contributions from silicate and carbonate weathering in the Krishna River system during peak discharge.

    PubMed

    Laskar, Amzad H; Gandhi, Naveen; Thirumalai, Kaustubh; Yadava, Madhusudan G; Ramesh, Rengaswamy; Mahajan, Ramakant R; Kumar, Dharmendra

    2014-06-01

    We present a comparative study of two offline methods, a newly developed method and an existing one, for the measurement of the stable carbon isotopic composition (δ(13)C) of dissolved inorganic carbon (DIC; δ(13)CDIC) in natural waters. The measured δ(13)CDIC values of different water samples, prepared from laboratory Na2CO3, ground and oceanic waters, and a laboratory carbonate isotope standard, are found to be accurate and reproducible to within 0.5 ‰\\ (1σ). The extraction of CO2 from water samples by these methods does not require pre-treatment or sample poisoning and can be applied to a variety of natural waters to address carbon cycling in the hydrosphere. In addition, we present a simple method (based on a two-end-member mixing model) to estimate the silicate-weathering contribution to DIC in a river system by using the concentration of DIC and its δ(13)C. This approach is tested with data from the Krishna River system as a case study, thereby quantifying the contribution of silicate and carbonate weathering to DIC, particularly during peak discharge.

  12. Uncertainty in projections of Southern Ocean carbon uptake and acidification

    NASA Astrophysics Data System (ADS)

    Lovenduski, Nicole; Hauri, Claudine

    2017-04-01

    We investigate projections of carbon uptake and the associated acidification of the Southern Ocean over 2006-2080 using output from two ensembles of the Community Earth System Model run under business as usual (RCP8.5) and mitigation (RCP4.5) emission scenarios. On basin-wide and regional scales we observe a rapid onset of aragonite undersaturation in surface waters by mid-century that may be detrimental to calcareous organisms. An analysis of variance reveals that the speed of transition from supersaturation to undersaturation is driven almost entirely by emission scenario, as internal variability in saturation depth across ensemble members is small. Regional differences are observed in the timing and magnitude of aragonite saturation state changes. In the Patagonian Shelf region, undersaturation of the top 200m of the water column is observed by 2080 regardless of emission scenario. Whereas, in the Weddell Sea, saturation state is significantly different between the two emission scenarios by 2080, and undersaturation of the surface waters is "avoidable" if we follow RCP4.5, rather than RCP8.5.

  13. Contribution of carbonate weathering to the CO2 efflux from temperate forest soils.

    PubMed

    Schindlbacher, Andreas; Borken, Werner; Djukic, Ika; Brandstätter, Christian; Spötl, Christoph; Wanek, Wolfgang

    Temperate forests provide favorable conditions for carbonate bedrock weathering as the soil CO2 partial pressure is high and soil water is regularly available. As a result of weathering, abiotic CO2 can be released and contribute to the soil CO2 efflux. We used the distinct isotopic signature of the abiotic CO2 to estimate its contribution to the total soil CO2 efflux. Soil cores were sampled from forests on dolomite and limestone and were incubated under the exclusion of atmospheric CO2. Efflux and isotopic signatures of CO2 were repeatedly measured of cores containing the whole mineral soil and bedrock material (heterotrophic respiration + CO2 from weathering) and of cores containing only the mineral top-soil layer (A-horizon; heterotrophic respiration). An aliquot of the cores were let dry out during incubation to assess effects of soil moisture. Although the δ(13)C values of the CO2 efflux from the dolomite soil cores were within a narrow range (A-horizon -26.2 ± 0.1 ‰; whole soil profile wet -25.8 ± 0.1 ‰; whole soil profile dry -25.5 ± 0.1 ‰) the CO2 efflux from the separated A-horizons was significantly depleted in (13)C when compared to the whole soil profiles (p = 0.015). The abiotic contribution to the total CO2 efflux from the dolomite soil cores was 2.0 ± 0.5 % under wet and 3.4 ± 0.5 % under dry conditions. No abiotic CO2 efflux was traceable from the limestone soil cores. An overall low contribution of CO2 from weathering was affirmed by the amount and (13)C signature of the leached dissolved inorganic carbon (DIC) and the radiocarbon signature of the soil CO2 efflux in the field. Together, our data point towards no more than 1-2 % contribution of abiotic CO2 to the growing season soil CO2 efflux in the field.

  14. Sustained growth of the Southern Ocean carbon storage in a warming climate

    NASA Astrophysics Data System (ADS)

    Ito, Takamitsu; Bracco, Annalisa; Deutsch, Curtis; Frenzel, Hartmut; Long, Matthew; Takano, Yohei

    2015-06-01

    We investigate the mechanisms controlling the evolution of Southern Ocean carbon storage under a future climate warming scenario. A subset of Coupled Model Intercomparison Project Phase 5 models predicts that the inventory of biologically sequestered carbon south of 40°S increases about 18-34 Pg C by 2100 relative to the preindustrial condition. Sensitivity experiments with an ocean circulation and biogeochemistry model illustrates the impacts of the wind and buoyancy forcings under a warming climate. Intensified and poleward shifted westerly wind strengthens the upper overturning circulation, not only leading to an increased uptake of anthropogenic CO2 but also releasing biologically regenerated carbon to the atmosphere. Freshening of Antarctic Surface Water causes a slowdown of the lower overturning circulation, leading to an increased Southern Ocean biological carbon storage. The rectified effect of these processes operating together is the sustained growth of the carbon storage in the Southern Ocean, even under the warming climate with a weaker global ocean carbon uptake.

  15. The Santa AnaWinds of Southern California in the context of Fire Weather

    NASA Astrophysics Data System (ADS)

    Cao, Yang

    The Santa Ana winds represent a high-impact weather event owing to the intimate relationship between the extremely dry, fast winds and the wildfire threat. The winds can be locally gusty, particularly in the complex terrain of San Diego county, where the airflow has characteristics of downslope windstorms. These winds can cause and/or rapidly spread wildfires, the threat of which is particularly acute during the autumn season before the onset of winter rains. It remains a day-to-day challenge to accurately predict wind gust speed, especially in the mountainous regions. Our study employs large physics ensembles composed of high-resolution simulations of severe downslope windstorms that involve an exhaustive examination of available model physical parameterizations. Model results are calibrated and validated against the San Diego Gas and Electric (SDG&E) mesonet observations, a dense, homogenous, and well-positioned network with uniform high quality. Results demonstrate model horizontal resolution, model physics, random perturbations and landuse database can have a material effect on the strength, location and timing of Santa Ana winds in real-data simulations. A large model physics ensemble reveals the land surface model to be most crucial in skillful wind predictions, which are particularly sensitive to the surface roughness length. A surprisingly simple gust parameterization is proposed for the San Diego network, based on the discovery that this homogeneous mesonet has a nearly invariant network-averaged gust factor. The gust forecast technique is of special interest in the context of routine weather combined with atmospheric humidity and fuel moisture information. A real-time wildfire threat warning system, the Santa Ana Wildfire Threat Index (SAWTI), has been developed to effectively communicate the upcoming Santa Ana wind strength with respect to the anticipated fire danger to first responders and the public. In addition to the wind and gust forecast techniques

  16. Carbon isotope ratios and impurities in diamonds from Southern Africa

    NASA Astrophysics Data System (ADS)

    Kidane, Abiel; Koch-Müller, Monika; Morales, Luiz; Wiedenbeck, Michael; De Wit, Maarten

    2015-04-01

    We are investigating the sources of diamonds from southern Africa by studying both their carbon isotopic composition and chemical impurities. Our samples include macro-sized diamonds from River Ranch kimberlite in Zimbabwe and the Helam and Klipspringer kimberlitic deposits from South Africa, as well as micro-sized diamonds from Klipspringer and Premier kimberlites in South Africa. We have characterized the samples for their structurally bounded nitrogen, hydrogen and platelets defect using a Fourier Transmission Infrared Spectroscopy (FTIR). Using the DiaMap routine, open source software (Howell et al., 2012), IR spectra were deconvulated and quantified for their nitrogen (A, B and D components) and hydrogen contents. High to moderate nitrogen concentrations (1810 to 400 µg/g; 400 to 50 µg/g respectively) were found in diamonds from Klipspringer and Helam. Moderate to low (<50 µg/g) nitrogen concentrations were observed in diamonds from Premier and River Ranch. Type II diamonds, i.e. diamonds with no N impurities, which are presumed to have been derived from ultramafic sources, are found in the River Ranch deposit. The macro- and micro-size diamonds from the Klipspringer deposit display similar nitrogen defects, with higher nitrogen concentration and more frequent D components found in the macro-size diamonds. One of the first steps towards reliable carbon isotope studies is the development of calibration materials for SIMS carbon isotopic analyses. We have investigated candidate materials both from a polycrystalline synthetic diamond sheet and two natural gem quality diamonds from Juina (Brazil). Electron-based images of the synthetic diamond sheet, obtained using GFZ Potsdam's dual beam FIB instrument, show many diamond grains with diameters greater than 35 µm. SIMS testing of the isotopic homogeneity of the back and front sides of the synthetic sheets reveal similar 13C/12C ratio within a RSD of <1 ‰ . SIMS isotopic analyses of the two natural diamond RMs

  17. The Southern Ocean's role in carbon exchange during the last deglaciation.

    PubMed

    Burke, Andrea; Robinson, Laura F

    2012-02-03

    Changes in the upwelling and degassing of carbon from the Southern Ocean form one of the leading hypotheses for the cause of glacial-interglacial changes in atmospheric carbon dioxide. We present a 25,000-year-long Southern Ocean radiocarbon record reconstructed from deep-sea corals, which shows radiocarbon-depleted waters during the glacial period and through the early deglaciation. This depletion and associated deep stratification disappeared by ~14.6 ka (thousand years ago), consistent with the transfer of carbon from the deep ocean to the surface ocean and atmosphere via a Southern Ocean ventilation event. Given this evidence for carbon exchange in the Southern Ocean, we show that existing deep-ocean radiocarbon records from the glacial period are sufficiently depleted to explain the ~190 per mil drop in atmospheric radiocarbon between ~17 and 14.5 ka.

  18. Impact of sub-horizontal discontinuities and vertical heterogeneities on recharge processes in a weathered crystalline aquifer in southern India

    NASA Astrophysics Data System (ADS)

    Nicolas, Madeleine; Selles, Adrien; Bour, Olivier; Maréchal, Jean-Christophe; Crenner, Marion; Wajiduddin, Mohammed; Ahmed, Shakeel

    2017-04-01

    In the face of increasing demands for irrigated agriculture, many states in India are facing water scarcity issues, leading to severe groundwater depletion. Because perennial water resources in southern India consist mainly of crystalline aquifers, understanding how recharge takes place and the role of preferential flow zones in such heterogeneous media is of prime importance for successful and sustainable aquifer management. Here we investigate how vertical heterogeneities and highly transmissive sub-horizontal discontinuities may control groundwater flows and recharge dynamics. Recharge processes in the vadose zone were examined by analysing the propagation of an infiltration front and mass transfers resulting from the implementation of a managed aquifer recharge (MAR) structure. Said structure was set up in the Experimental Hydrogeological Park in Telangana (Southern India), a well-equipped and continuously monitored site, which is periodically supplied with surface water deviated from the nearby Musi river, downstream of Hyderabad. An initial volume balance equation was applied to quantify the overall inputs from the MAR structure into the groundwater system, which was confirmed using a chloride mass balance approach. To understand how this incoming mass is then distributed within the aquifer, we monitored the evolution of water volumes in the tank, and the resulting lateral propagation front observed in the surrounding borehole network. Borehole logs of temperature and conductivity were regularly performed to identify preferential flow paths. As a result we observed that mass transfers take place in the way of preferential lateral flow through the most transmissive zones of the profile. These include the interface between the lower portion of the upper weathered horizon (the saprolite) and the upper part of the underlying fissured granite, as well as the first flowing fractures. This leads to a rapid lateral transfer of recharge, which allows quick

  19. Linking the SASSCAL WeatherNet and data management/rescue activities to provide consistent information for climate change assessments in Southern Africa

    NASA Astrophysics Data System (ADS)

    Helmschrot, J.; Kaspar, F.; Muche, G.; Hillmann, T.; Kanyanga, J.; Butale, M.; Nascimento, D.; Josenhans, K.; Falanga, E.; Neto, F. O. S.; Kruger, S.; Juergens, N.

    2014-12-01

    Many countries of Southern Africa face inadequate weather monitoring networks to provide reliable and consistent information for the development of efficient management strategies for sustainable water and land resources management, drought and flood risk analysis and forecasts as well as climate change impacts assessments. In addition, some existing networks are characterized by station data showing notable gaps in long-term observations. On the other hand, useful climate information is saved in historical documents and archives, but only barely explored up to now. Such documents are also available in archives of European meteorological services, partly also not yet in digital format. A main aim of the SASSCAL Initiative (Southern African Science Service Centre for Climate Change and Adaptive Land Management; www.sasscal.org) is to improve the availability of reliable meteorological baseline data along with a set of analytical methods to strengthen the research capacities in the SASSCAL region including Angola, Botswana, Namibia, South Africa and Zambia, and therewith to support and integrate information of existing national monitoring networks of the Southern African region. In close cooperation with the national weather authorities and various research institutions of the SASSCAL region, the above mentioned deficits are specifically addressed by i) extending the existing national monitoring networks through additional automatic weather stations and their integration in the SASSCAL WeatherNet which in near future hosts about 130 stations, ii) contributing to the development of Climate Data Management Systems (CDMS) at the national weather authorities in Angola, Botswana and Zambia and iii) the provision of additional time series of climate data based on the historic documents from various archives in all countries. The paper presents first results and shows how these efforts are linked to provide consistent climate information for Southern Africa in order to

  20. An observed database to characterize the weather conditions associated with subtropical cyclogenesis over southern-southeastern Brazil

    NASA Astrophysics Data System (ADS)

    Yamamoto, R.; Porfirio da Rocha, R.

    2012-04-01

    A project to study the climatic, dynamic and synoptic aspects of subtropical cyclones that develop in southern-southeastern coast of Brazil is in development. The weather conditions associated with such cyclones is an important question that must be answered in this project. However, for such characterization it is necessary to use the local meteorological observations of wind, wind gust, rainfall, air temperature, etc. The NCEP (National Center for Environmental Prediction) reanalysis have spatial and time resolutions that provide elements to study the synoptic and dynamics of meteorological events (cyclone, anticyclones, troughs, ridges, monsoons circulations, etc) until the production of complex climatology. However, this analysis has coarse horizontal resolution (~250 Km) that often does not allow the identification of intense meteorological phenomena. A more precise characterization of location and intensity of weather conditions associated with subtropical cyclones would be performed using local observations. Therefore, this work describes the methodology to construct a database of surface weather observations using a relational database management system (RDBMS) MySQL. The data source are SYNOP (Surface Synoptic Observations), METAR (Meteorological Aerodrome Report), NCDC (National Climatic Data Center) and CETESB (Environmental Agency of Sao Paulo State) that are available online through dynamic web page. An iterative algorithm robot was developed to automate the data extraction. Most of the data source are encoded or at non-standard format, hence was developed an algorithm in C++, using the REGEX library, an engine of text pattern search, for decode and handle the exception (erroneous and corrupted data). After the data decoding and formatting it is stored into the MySQL database. The structure of database was divided into categories of tables: a table with the source of data definition, a table with stations information and two sets of tables (for hourly

  1. Uranium-series dated authigenic carbonates and Acheulian sites in southern Egypt

    NASA Technical Reports Server (NTRS)

    Szabo, B. J.; Mchugh, W. P.; Schaber, G. G.; Breed, C. S.; Haynes, C. V., Jr.

    1989-01-01

    Field investigations of aggraded paleovalleys, which were identified in southern Egypt using SIR, are discussed. Acheulian artifacts were found in authigenic carbonate deposites along the edges of the paleovalleys. Uranium series dating of 25 carbonate samples shows that widespread carbonate deposition in the area occurred about 45, 141, and 212 thousand years ago. Analysis of the carbonate suggests that the deposition may be related to late Pleistocene humid climates that facilitated human settlement in the region.

  2. Seasonally different carbon flux changes in the Southern Ocean in response to the southern annular mode.

    PubMed

    Hauck, J; Völker, C; Wang, T; Hoppema, M; Losch, M; Wolf-Gladrow, D A

    2013-12-01

    Stratospheric ozone depletion and emission of greenhouse gases lead to a trend of the southern annular mode (SAM) toward its high-index polarity. The positive phase of the SAM is characterized by stronger than usual westerly winds that induce changes in the physical carbon transport. Changes in the natural carbon budget of the upper 100 m of the Southern Ocean in response to a positive SAM phase are explored with a coupled ecosystem-general circulation model and regression analysis. Previously overlooked processes that are important for the upper ocean carbon budget during a positive SAM period are identified, namely, export production and downward transport of carbon north of the polar front (PF) as large as the upwelling in the south. The limiting micronutrient iron is brought into the surface layer by upwelling and stimulates phytoplankton growth and export production but only in summer. This leads to a drawdown of carbon and less summertime outgassing (or more uptake) of natural CO2. In winter, biological mechanisms are inactive, and the surface ocean equilibrates with the atmosphere by releasing CO2. In the annual mean, the upper ocean region south of the PF loses more carbon by additional export production than by the release of CO2 into the atmosphere, highlighting the role of the biological carbon pump in response to a positive SAM event.

  3. Carbon Dioxide Weathering Flux Since the Last Glacial Maximum to the Present, its Control of River Water Composition, and its Role in the Global Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Lerman, A.; Wu, L.; MacKenzie, F. T.

    2006-12-01

    A weathering potential ψ = (net CO2 consumed)/(HCO3- produced) describes the consumption of CO2 in mineral weathering reactions. Based on the reaction stoichiometry, ψ = 0.5 for pure carbonates and 1.0 for the crystalline silicate continental crust, with intermediate values for mixed- mineralogy rocks. Carbon dioxide is the main driver of mineral weathering reactions as an acid derived from the atmosphere and(or) remineralization of organic matter in soil, and it is supplemented by small, but perhaps regionally important, amounts of H2SO4 forming in the oxidation of pyrite. The projected anthropogenic emissions of SO2 to the atmosphere may provide H2SO4 to the continental surface at a rate that is 3 to 5 times greater than its natural production by the oxidation of sedimentary pyrite. The higher H2SO4 input may increase the main ionic concentrations in rivers by ~13%, without significantly affecting the CO2 weathering consumption. Sulfuric acid produces HCO3- or CO2 by reactions with the carbonates. In the global carbon cycle from the Last Glacial Maximum to the present, the CO2 uptake in the weathering layer is comparable to other major fluxes in the atmosphere-land-ocean system. The weathering layer thickness depends on the mineral dissolution rates, reactive mineral surface area, particle size, and rock porosity, not all of which are generally well known. In an average world river, the mass proportions of the main cations and anions differ from those in the weathering source consisting of the sediments and part of the continental crust, because of the differences in mineral solubilities and dissolution rates. A dissolution model of a weathering source (63 weight % average sediment and 37% upper continental crust) gives an average river water composition that agrees very well with the composition ranges of other investigators. This dissolution model gives an average CO2 consumption potential of ψ = 0.72 and a sequence of relative stability or persistence in

  4. Electrochemical Acceleration of Carbonate and Silicate Weathering for CO2 Mitigation

    NASA Astrophysics Data System (ADS)

    Rau, G. H.; Carroll, S.

    2011-12-01

    Carbonate and many silicate minerals dissolve in strong acids, and such acids are commonly generated at the anode of a conventional saline water electrolysis cell. It was therefore reasoned that encasing such an anode with base minerals would lead to enhanced mineral dissolution and hence increased hydroxide (base) generation at the cathode, formed in course of splitting water, generating H2 and OH-. Subsequent exposue of the alkalized solution to CO2 (e.g., as in air) would lead to absorption of the CO2 and formation of stable dissolved or solid (bi)carbonates for carbon sequestration. Previously, it has been demonstrated that mineral carbonate encasement of a seawater electrolysis cell anode indeed generated basic solutions in excess of pH 9 that were subsequently neutralized via contact with air CO2, increasing the carbon content of the initial seawater by 30% (Rau, G.H. 2008. Environ Sci. Techol. 42, 8935-). To test such a weathering/CO2 capture scheme using silicate minerals, either powdered wollastonite or ultramafic rock standard (UM-4) was encased around the anode of an electrolysis cell composed of graphite electrodes and a 0.25M Na2SO4 electrolyte solution. After 0.5 to 1.5 hrs of electricity application (3.5Vdc, 5-10mA), the electrolyte pH rose to as much as 11.1 (initial and blank solution pH's <6.6). Subequent bubbling of these basic solutions with air lowered pH by at least 2 units and increased dissolve carbon content (primarily bicarbonate) by as much as 50X that of the blanks. While Ca2+ and Mg2+ concentrations were elevated, these were insufficient to balance the majority of the bicarbonate anions formed in solution. This suggests that in these experiments the silicate minerals acted as a neutralizer of the anolyte acid, H2SO4, forming mostly insoluble CaSO4 and MgSO4 at the anode. This then allowed NaOH normally produced at the cathode to accumulate in solution, in turn reacting with air CO2 to form NaHCO3. Longer electrolysis times and

  5. Preparing for NEO Sample Return: Simulating the Effects of Laser Space Weathering on Macromolecular Carbon

    NASA Astrophysics Data System (ADS)

    Gasda, P. J.; Gillis-Davis, J.; Bradley, J. P.; ChengYu, S.

    2014-12-01

    The NASA OSIRIS-REx mission plans to visit a B-type asteroid and return pristine regolith samples to Earth. These regolith samples, like those returned by the JAXA Hayabusa mission from Itokawa, will likely exhibit some modification by space weathering (SW). Further, these samples may contain up to ~5% organic carbon, mainly in the form of macromolecular carbon (MMC). MMC in meteorites can be studied with Raman spectroscopy; changes in its Raman spectral parameters have been shown to correlate with the petrographic grade of the meteorite. But these petrographic studies are calibrated with internal pieces of meteorite samples, so the MMC seen in meteorites has not experienced SW. Hence, it is important to determine the effects of SW may have on the MMC and its Raman spectrum. Laser pulse heating experiments that simulate the micrometeorite impact component of SW have been carried out in samples of pure graphite, and carbonaceous chondrites Allende (CV3) and Murchison (CM2). Pulse heating was done in vacuum (1×10-6 torr) with a 20 Hz 1064 nm Nd:YAG laser, a 6 ns pulse duration (30 mJ/pulse), and a 200 μm spot size. Raman spectra were collected on the each sample using a WITec alpha300 R confocal Raman microscope, with a 1 mW 532 nm continuous laser and a ~10 μm laser spot size. UVVIS-NIR (0.4-2.5 µm) reflectance was measured using an Analytical Spectral Devices Inc. FieldSpec 4 spectrometer. Based on its Raman spectra, the original pure graphite is modified to nanocrystalline graphite by 10 minutes (12,000 laser pulses), and further modified to glassy carbon (amorphous 3-coordinate carbon) within 20 minutes (24,000 laser pulses). Vapor deposited on the side of the sample holder has a Raman spectrum consistent with amorphous carbon glass (3- and 4-coordinate carbon). Laser SW carried out on a slab of Murchison resulted in the production of glassy carbon inside siliceous melt blobs in the laser craters. Surprisingly, the Raman spectrum for MMC in Allende powder

  6. Atmospheric Rivers and floods in Southern California: Climate forcing of extreme weather events.

    NASA Astrophysics Data System (ADS)

    Hendy, I. L.; Heusser, L. E.; Napier, T.; Pak, D. K.

    2016-12-01

    Southern California has a Mediterranean type climate characterized by warm dry summers associated with the North Pacific High pressure system and cool, wet winters primarily associated in low pressure systems originating in the high latitude North Pacific. Extreme precipitation, however, is connected to strong zonal flow that brings warm, moist tropical across the Pacific (AKA atmospheric river). Here we present a revised record of flood events in Santa Barbara Basin that have been linked to atmospheric rivers focusing on events associated with transitions between known climate events using new radiocarbon chronology and detailed sediment composition. Flood events identified by homogenous grey layers are present throughout the Holocene with a recurrence every 110 years, but are particularly common (85 year recurrence) between 4,200 and 2,000 years BP. Interval between 6,500 and 4,500 commonly associated with dry conditions in California was associated with fewer flood events (recurrence interval increased to 176 years). Intervals of high lake levels in California associated with pluvials appear to be associated with more frequent extreme precipitation events. The longest recurrence interval (535 years) is associated with the Medieval Climate Anomaly. The season in which the atmospheric river occurs was estimated using the relative abundance of pollen within the flood deposit. The 735 and 1270 C.E. flood events are associated with May-June flowering vegetation, while the most recent events (1861-2 and 1761 C.E.) were associated with November to March flowering vegetation. This agrees with the December-January rainfall records of the historic 1861-62. We conclude the frequency of extreme precipitation events appears to increase as climate cools (e.g. the Little Ice Age).

  7. Rapid Conversion from Carbohydrates to Large-Scale Carbon Quantum Dots for All-Weather Solar Cells.

    PubMed

    Tang, Qunwei; Zhu, Wanlu; He, Benlin; Yang, Peizhi

    2017-02-28

    A great challenge for state-of-the-art solar cells is to generate electricity in all weather. We present here the rapid conversion of carbon quantum dots (CQDs) from carbohydrates (including glucose, maltol, sucrose) for an all-weather solar cell, which comprises a CQD-sensitized mesoscopic titanium dioxide/long-persistence phosphor (m-TiO2/LPP) photoanode, a I(-)/I3(-) redox electrolyte, and a platinum counter electrode. In virtue of the light storing and luminescent behaviors of LPP phosphors, the generated all-weather solar cells can not only convert sunlight into electricity on sunny days but persistently realize electricity output in all dark-light conditions. The maximized photoelectric conversion efficiency is as high as 15.1% for so-called all-weather CQD solar cells in dark conditions.

  8. Early formation of gnammas (weathering pits) in a recently glaciated area of Torres del Paine, southern Patagonia (Chile)

    NASA Astrophysics Data System (ADS)

    Domínguez-Villar, David

    2006-06-01

    Incipient gnammas (weathering pits) were identified and measured in the Francés Valley of Torres del Paine, southern Patagonia. The gnammas were located on the granite blocks of a lateral moraine deposited during a Late Holocene neoglacial advance. The gnammas were measured for maximum and minimum depth, length, and width in addition to other observations. Based on these measurements, the surface area and the volume of the gnammas were calculated. Most of the gnammas have < 1 L of rock volume eroded, and the maximum depth is always < 10 cm. The gnammas do not develop erosional spillways. A high correlation exists between maximum and minimum depths, indicating these values are not completely independent. Thus, the depth ratio has been used to characterize the gnammas for discrete locations. The gnammas from Francés Valley belong to a unique normal population and a δ-value based on the depth ratio was defined to represent this population. The δ of Francés Valley is 1.33 ± 0.07, comparable with the lowest values of other stations around the globe. I suggest that the δ-value could be used as an indicator of gnamma evolution.

  9. Low-temperature alteration of dredged volcanics from the Southern Chile Ridge: Additional information about early stages of seafloor weathering

    USGS Publications Warehouse

    Pichler, T.; Ridley, W.I.; Nelson, E.

    1999-01-01

    A suite of submarine volcanic rocks from the Southern Chile Ridge has been examined in order to investigate the early stages of low temperature alteration. Alteration in these samples proceeded as follows: (1) Fe-staining on sample surface and along fractures, (2) filling of vesicles with secondary material, (3) breakdown of glassy matrix, (4) breakdown of microcrystalline matrix, and (5) breakdown and replacement of olivine. Plagioclase and pyroxene were sometimes found to be slightly altered along internal fissures. Secondary or alteration phases generally showed high K (3-5 wt.%), Fe (30-70 wt.%) and low Al ( Rb > K. During initial stages of alteration the behavior of some trace elements such as rare-earth elements (REE), Ba, Zr, Hf, Ta, Nb, and Mo are solely controlled by the precipitation of Mn-rich Fe-oxyhydroxides. The preferred incorporation of Ce into Mn-rich Fe-oxyhydroxides may be a principal factor explaining the Ce depletion in seawater. We conclude that the earliest stages of submarine weathering are controlled by Eh and pH gradients between the rock and seawater. In the absence of a buffer, oxidation of ferrous iron causes a decrease in solution pH.

  10. IODP Expedition 354: A Bengal fan record of Himalayan erosion, weathering and organic carbon burial during the Neogene.

    NASA Astrophysics Data System (ADS)

    France-Lanord, C.; Spiess, V.; Klaus, A.; Galy, A.; Galy, V.

    2015-12-01

    The development of the Himalayan orogen induced a major change in continental distribution, topography and climate that impacted the global biogeochemical cycles. The development of the highest mountain range coupled to the intense monsoonal precipitation regime generated an intense erosional flux that enhanced both organic carbon burial and silicate weathering. The largest part of the sediment flux was exported to the Bengal Fan, accumulating a long-term archive of this erosion. These sediments record the nature of eroded formations in the Himalaya and allow the documentation of weathering as well as organic carbon fluxes. In February-March 2015, IODP Expedition 354 drilled an E-W transect in the middle fan at 8°N to investigate interactions between the growth of the Himalaya, the development of the Indian monsoon, and processes affecting the carbon cycle. This expedition obtained a comprehensive record of turbiditic deposition since the Late Oligocene. Shipboard results reveal that the chemical and mineralogical compositions of turbiditic sediments cored across the transect are relatively stable throughout the Neogene. They reveal a weak regime of chemical weathering with no significant variation through time. This differs from the distal fan record (Leg 116) where from ~7 to 1 Ma, weathered and smectite rich sediments dominated. This difference implies that the distal fan record is not related to a direct evolution of the erosion regime but rather is controlled by a change in sediment transport within the fan. Shipboard estimates of organic carbon loading and behavior resemble observations made in the modern Ganga-Brahmaputra river sediments, suggesting efficient terrestrial organic carbon burial in the Bengal Fan [1]. Preliminary observations support the idea that Himalayan erosion has consumed atmospheric CO2 through the burial of organic carbon, more than by silicate weathering. [1] http://dx.doi.org/10.1038/nature06273

  11. The influence of Southern Ocean winds on the North Atlantic carbon sink

    NASA Astrophysics Data System (ADS)

    Bronselaer, Ben; Zanna, Laure; Munday, David R.; Lowe, Jason

    2016-06-01

    Observed and predicted increases in Southern Ocean winds are thought to upwell deep ocean carbon and increase atmospheric CO2. However, Southern Ocean dynamics affect biogeochemistry and circulation pathways on a global scale. Using idealized Massachusetts Institute of Technology General Circulation Model (MITgcm) simulations, we demonstrate that an increase in Southern Ocean winds reduces the carbon sink in the North Atlantic subpolar gyre. The increase in atmospheric CO2 due to the reduction of the North Atlantic carbon sink is shown to be of the same magnitude as the increase in atmospheric CO2 due to Southern Ocean outgassing. The mechanism can be described as follows: The increase in Southern Ocean winds leads to an increase in upper ocean northward nutrient transport. Biological productivity is therefore enhanced in the tropics, which alters the chemistry of the subthermocline waters that are ultimately upwelled in the subpolar gyre. The results demonstrate the influence of Southern Ocean winds on the North Atlantic carbon sink and show that the effect of Southern Ocean winds on atmospheric CO2 is likely twice as large as previously thought in past, present, and future climates.

  12. Reverse weathering, the carbonate-feldspar system, and porosity evolution during burial of sandstones

    SciTech Connect

    Milliken, K.L.; Land, L.S. )

    1991-03-01

    Acid generated by reverse weathering in mudrocks drives linked reactions involving carbonates and feldspars that in turn have a profound impact on the evolution of porosity during burial diagenesis of sandstones. In the Oligocene Frio Formation along the Texas Gulf Coast, petrographic evidence at various scales in both sandstones and shales, and modern pore fluid compositions are all consistent with this idea. Acid released during illitization of smectite dissolves marine skeletal and detrital carbonate in shales. Shales export excess H+, dissolved CA++, and CO{sub 2} to the sandstones. Resultant interaction of sandstones with these shale-derived fluids is primarily controlled by the feldspar content of the sandstones. If the sandstones contain reactive feldspar content of the sandstones. If the sandstones contain reactive feldspar, acid from the shales is effectively buffered, thus allowing precipitation of calcite as cements and grain replacements in the sandstones and maintenance of fluids with low pCO{sub 2}. Once the supply of reactive detrital feldspar is exhausted through dissolution and albitization, shale-derived H+ remobilizes carbonate in sandstones, generating secondary porosity and fluids with high pCO{sub 2}. Acid generated through thermal maturation of organic matter plays only a trivial role in this system of reactions because the quantity of acid required for dissolution of carbonate and feldspar far exceeds the amount of kerogen in the system. The balance between the local acid generation capacity of shales, the local buffering capacity of feldspars in sandstones, and the availability of externally derived acids and ions is the primary control on the sequence of reactions occurring during burial metamorphism of sandstones.

  13. Southern Ocean heat and carbon uptake: mechanisms, recent trends, and future changes

    NASA Astrophysics Data System (ADS)

    Froelicher, T. L.

    2015-12-01

    The Southern Ocean's dominant influence on the global heat balance and nutrient and carbon cycles stems from the fact that it is the primary gateway through which Earth's cold, centuries old and nutrient rich deep and bottom waters interact with the atmosphere. The westerly winds in the Southern Hemisphere drive a strongly divergent surface flow that draws up water from below in a wide ring circling the Antarctic continent. In the first part of the talk, we assess the uptake, transport, and storage of oceanic anthropogenic carbon and heat in the Southern Ocean over the period 1861-2005 in a new set of carbon-climate Earth System Models. Simulations show that the Southern Ocean south of 30°S, covering only 30% of the global surface ocean area, accounts for more than 40% of global anthropogenic carbon uptake. Furthermore, the Southern Ocean takes up three quarters of the total excess heat generated by the increasing levels of greenhouse gases in the atmosphere. Anthropogenic carbon and heat storage show a common broad-scale pattern of change, but ocean heat storage is more structured than ocean carbon storage suggesting that different mechanisms are important. The Southern Ocean, however, remains the region where models differ the most in the representation of anthropogenic carbon and, in particular, heat uptake. While the Southern Ocean carbon uptake has increased considerably in recent decades, as expected based on the substantial increase in atmospheric CO2, there is considerable concern that this sink will saturate or even reverse in response to warming, changing ocean circulation and chemistry. In the second part of the talk, novel multi-millennial global warming simulations with a comprehensive Earth System Model under a 1% yr-1 atmospheric CO2 increase to 2xCO2 and constant forcing thereafter scenario will be used to explore future long-term changes in the Southern Ocean carbon uptake. We show that after full equilibration of the model with doubling of

  14. Effects of short-term weathering on the stable carbon isotope compositions of crude oils and fuel oils.

    PubMed

    Liu, Yu; Xu, Jixiang; Chen, Wenjing; Li, Ying

    2017-06-15

    A short-term simulated weathering experiment was performed on two crude oils and two heavy fuel oils under natural conditions to evaluate the effects of natural weathering processes by using gas chromatography-mass spectrometry combined with gas chromatography-isotopic ratio mass spectrometry. The results of diagnostic ratios of n-alkanes show that only odd to even predominance (OEP1, OPE2) and carbon preference index (CPI) remain stabilized during the 28 d weathering process, but they cannot effectively distinguish the four types of oils. Statistical analyses based on paired sample t-test and principal component analysis (PCA) revealed that stable carbon isotope compositions of n-alkanes in the four studied oils have no significant changes over the weathering time, and that the carbon isotope discrimination (Δδ(13)C) of n-alkanes is <3‰. We have provided evidence that the stable carbon isotope compositions of n-alkanes compared to n-alkanes diagnostic ratios significantly improve the efficiency and fidelity of the oil fingerprint identification. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Pilot Inter-Laboratory Studies for Evaluating Weathering-Induced Release of Carbon Nanotubes from Solid Matrices

    EPA Science Inventory

    Nanomaterials are increasingly being used in polymer composites to enhance the properties of these materials. Here we present results of a pilot inter-laboratory study to simulate the effects of weathering on the potential release of multiwalled carbon nanotubes (MWCNT) from thei...

  16. Pilot Inter-Laboratory Studies for Evaluating Weathering-Induced Release of Carbon Nanotubes from Solid Matrices

    EPA Science Inventory

    Nanomaterials are increasingly being used in polymer composites to enhance the properties of these materials. Here we present results of a pilot inter-laboratory study to simulate the effects of weathering on the potential release of multiwalled carbon nanotubes (MWCNT) from thei...

  17. Meeting global policy commitments carbon sequestration and southern pine forests

    Treesearch

    Kurt H. Johnsen; David N. Wear; R. Oren; R.O. Teskey; Felipe Sanchez; Rodney E. Will; John Butnor; D. Markewitz; D. Richter; T. Rials; H.L. Allen; J. Seiler; D. Ellsworth; Christopher Maier; G. Katul; P.M. Dougherty

    2001-01-01

    In managed forests, the amount of carbon further sequestered will be determined by (1) the increased amount of carbon in standing biomass (resulting from land-use changes and increased productivity); (2) the amount of recalcitrant carbon remaining below ground at the end of rotations; and (3) the amount of carbon sequestered in products created from harvested wood....

  18. Land use change effects on forest carbon cycling throughout the southern United States

    Treesearch

    Peter B. Woodbury; Linda S. Heath; James E. Smith

    2006-01-01

    We modeled the effects of afforestation and deforestation on carbon cycling in forest floor and soil from 1900 to 2050 throughout 13 states in the southern United States. The model uses historical data on gross (two-way) transitions between forest, pasture, plowed agriculture, and urban lands along with equations describing changes in carbon over many decades for each...

  19. Weather and climate controls over the seasonal carbon isotope dynamics of sugars from subalpine forest trees.

    PubMed

    Hu, Jia; Moore, David J P; Monson, Russell K

    2010-01-01

    We examined the environmental variables that influence the delta(13)C value of needle and phloem sugars in trees in a subalpine forest. We collected sugars from Pinus contorta, Picea engelmannii and Abies lasiocarpa from 2006 to 2008. Phloem and needle sugars were enriched in (13)C during the autumn, winter and early spring, but depleted during the growing season. We hypothesized that the late-winter and early-spring (13)C enrichment was due to the mobilization of carbon assimilated the previous autumn; however, needle starch concentrations were completely exhausted by autumn, and we observed evidence of new starch production during episodic warm weather events during the winter and early-spring. Instead, we found that (13)C enrichment was best explained by the occurrence of cold night-time temperatures. We also observed seasonal decoupling in the (13)C/(12)C ratios of needle and phloem sugars. We hypothesized that this was due to seasonally-changing source-sink patterns, which drove carbon translocation from the needles towards the roots early in the season, before bud break, but from the roots towards the needles later in the season, after bud break. Overall, our results demonstrate that the (13)C/(12)C ratio of recently-assimilated sugars can provide a sensitive record of the short-term coupling between climate and tree physiology.

  20. Plants, Weathering, and the Evolution of Atmospheric Carbon Dioxide and Oxygen

    SciTech Connect

    Berner, Robert A

    2008-02-05

    Over the past six years we have published 24 papers that can be divided into three sections: (1) Study of plants and weathering, (2) modeling the evolution of atmospheric CO2 over Phanerozoic time (past 550 million years). (3) Modeling of atmospheric O2 over Phanerozoic time. References to papers published acknowledging this grant can be found at the end of this report and almost all are supplied in pdf form. (1) In the temperate forests of the Cascade Mountains, USA, calcium and magnesium meet vastly different fates beneath angiosperms vs gymnosperms. Calcium is leached beneath both groves of trees, but leached 20-40% more beneath the angiosperms. Magnesium is retained in the forest system beneath the angiosperms and leached from beneath the gymnosperms. (2) We have shown that climate and CO2, based on both carbon cycle modeling and hundreds of independent proxies for paleo-CO2, correlate very well over the past 550 million year. In a recent paper we use this correlation to deduce the sensitivity of global mean temperature to a doubling of atmospheric CO2, and results are in excellent agreement with the results of climatologists based on the historical record and on theoretical climate models (GCM’s).(3) We have shown that concentrations of atmospheric oxygen, calculated by a combined carbon-sulfur cycle model, over the past 550 million years have varied with and influenced biological evolution.

  1. Carbon - Bulk Density Relationships for Highly Weathered Soils of the Americas

    NASA Astrophysics Data System (ADS)

    Nave, L. E.

    2014-12-01

    Soils are dynamic natural bodies composed of mineral and organic materials. As a result of this mixed composition, essential properties of soils such as their apparent density, organic and mineral contents are typically correlated. Negative relationships between bulk density (Db) and organic matter concentration provide well-known examples across a broad range of soils, and such quantitative relationships among soil properties are useful for a variety of applications. First, gap-filling or data interpolation often are necessary to develop large soil carbon (C) datasets; furthermore, limitations of access to analytical instruments may preclude C determinations for every soil sample. In such cases, equations to derive soil C concentrations from basic measures of soil mass, volume, and density offer significant potential for purposes of soil C stock estimation. To facilitate estimation of soil C stocks on highly weathered soils of the Americas, I used observations from the International Soil Carbon Network (ISCN) database to develop carbon - bulk density prediction equations for Oxisols and Ultisols. Within a small sample set of georeferenced Oxisols (n=89), 29% of the variation in A horizon C concentrations can be predicted from Db. Including the A-horizon sand content improves predictive capacity to 35%. B horizon C concentrations (n=285) were best predicted by Db and clay content, but were more variable than A-horizons (only 10% of variation explained by linear regression). Among Ultisols, a larger sample set allowed investigation of specific horizons of interest. For example, C concentrations of plowed A (Ap) horizons are predictable based on Db, sand and silt contents (n=804, r2=0.38); gleyed argillic (Btg) horizon concentrations are predictable from Db, sand and clay contents (n=190, r2=0.23). Because soil C stock estimates are more sensitive to variation in soil mass and volume determinations than to variation in C concentration, prediction equations such as

  2. A generic weather-driven model to predict mosquito population dynamics applied to species of Anopheles, Culex and Aedes genera of southern France.

    PubMed

    Ezanno, P; Aubry-Kientz, M; Arnoux, S; Cailly, P; L'Ambert, G; Toty, C; Balenghien, T; Tran, A

    2015-06-01

    An accurate understanding and prediction of mosquito population dynamics are needed to identify areas where there is a high risk of mosquito-borne disease spread and persistence. Simulation tools are relevant for supporting decision-makers in the surveillance of vector populations, as models of vector population dynamics provide predictions of the greatest risk periods for vector abundance, which can be particularly helpful in areas with a highly variable environment. We present a generic weather-driven model of mosquito population dynamics, which was applied to one species of each of the genera Anopheles, Culex, and Aedes, located in the same area and thus affected by similar weather conditions. The predicted population dynamics of Anopheles hyrcanus, Culex pipiens, and Aedes caspius were not similar. An. hyrcanus was abundant in late summer. Cx. pipiens was less abundant but throughout the summer. The abundance of both species showed a single large peak with few variations between years. The population dynamics of Ae. caspius showed large intra- and inter-annual variations due to pulsed egg hatching. Predictions of the model were compared to longitudinal data on host-seeking adult females. Data were previously obtained using CDC-light traps baited with carbon dioxide dry ice in 2005 at two sites (Marais du Viguerat and Tour Carbonnière) in a favourable temperate wetland of southern France (Camargue). The observed and predicted periods of maximal abundance for An. hyrcanus and Cx. pipiens tallied very well. Pearson's coefficients for these two species were over 75% for both species. The model also reproduced the major trends in the intra-annual fluctuations of Ae. caspius population dynamics, with peaks occurring in early summer and following the autumn rainfall events. Few individuals of this species were trapped so the comparison of predicted and observed dynamics was not relevant. A global sensitivity analysis of the species-specific models enabled us to

  3. Major carbon-14 deficiency in modern snail shells from southern Nevada springs

    USGS Publications Warehouse

    Riggs, A.C.

    1984-01-01

    Carbon-14 contents as low as 3.3 ?? 0.2 percent modern (apparent age, 27,000 years) measured from the shells of snails Melanoides tuberculatus living in artesian springs in southern Nevada are attributed to fixation of dissolved HCO3- with which the shells are in carbon isotope equilibrium. Recognition of the existence of such extreme deficiencies is necessary so that erroneous ages are not attributed to freshwater biogenic carbonates.

  4. Snapshot prediction of carbon productivity, carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy.

    PubMed

    Sackett, Olivia; Petrou, Katherina; Reedy, Brian; Hill, Ross; Doblin, Martina; Beardall, John; Ralph, Peter; Heraud, Philip

    2016-02-01

    Diatoms, an important group of phytoplankton, bloom annually in the Southern Ocean, covering thousands of square kilometers and dominating the region's phytoplankton communities. In their role as the major food source to marine grazers, diatoms supply carbon, nutrients and energy to the Southern Ocean food web. Prevailing environmental conditions influence diatom phenotypic traits (for example, photophysiology, macromolecular composition and morphology), which in turn affect the transfer of energy, carbon and nutrients to grazers and higher trophic levels, as well as oceanic biogeochemical cycles. The paucity of phenotypic data on Southern Ocean phytoplankton limits our understanding of the ecosystem and how it may respond to future environmental change. Here we used a novel approach to create a 'snapshot' of cell phenotype. Using mass spectrometry, we measured nitrogen (a proxy for protein), total carbon and carbon-13 enrichment (carbon productivity), then used this data to build spectroscopy-based predictive models. The models were used to provide phenotypic data for samples from a third sample set. Importantly, this approach enabled the first ever rate determination of carbon productivity from a single time point, circumventing the need for time-series measurements. This study showed that Chaetoceros simplex was less productive and had lower protein and carbon content during short-term periods of high salinity. Applying this new phenomics approach to natural phytoplankton samples could provide valuable insight into understanding phytoplankton productivity and function in the marine system.

  5. Snapshot prediction of carbon productivity, carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy

    PubMed Central

    Sackett, Olivia; Petrou, Katherina; Reedy, Brian; Hill, Ross; Doblin, Martina; Beardall, John; Ralph, Peter; Heraud, Philip

    2016-01-01

    Diatoms, an important group of phytoplankton, bloom annually in the Southern Ocean, covering thousands of square kilometers and dominating the region's phytoplankton communities. In their role as the major food source to marine grazers, diatoms supply carbon, nutrients and energy to the Southern Ocean food web. Prevailing environmental conditions influence diatom phenotypic traits (for example, photophysiology, macromolecular composition and morphology), which in turn affect the transfer of energy, carbon and nutrients to grazers and higher trophic levels, as well as oceanic biogeochemical cycles. The paucity of phenotypic data on Southern Ocean phytoplankton limits our understanding of the ecosystem and how it may respond to future environmental change. Here we used a novel approach to create a ‘snapshot' of cell phenotype. Using mass spectrometry, we measured nitrogen (a proxy for protein), total carbon and carbon-13 enrichment (carbon productivity), then used this data to build spectroscopy-based predictive models. The models were used to provide phenotypic data for samples from a third sample set. Importantly, this approach enabled the first ever rate determination of carbon productivity from a single time point, circumventing the need for time-series measurements. This study showed that Chaetoceros simplex was less productive and had lower protein and carbon content during short-term periods of high salinity. Applying this new phenomics approach to natural phytoplankton samples could provide valuable insight into understanding phytoplankton productivity and function in the marine system. PMID:26230047

  6. Validation of Multi-Scale Simulations of the Flow over Big Southern Butte Using Weather Research and Forecasting Model

    NASA Astrophysics Data System (ADS)

    Kosovic, B.; Jimenez, P. A.

    2015-12-01

    Advances in high performance computational resources and frameworks now make possible the use of Numerical Weather Predication (NWP) models for high-resolution simulations of atmospheric flows. In order to develop best practices, standards, and procedures for multi-scale simulations, we need to carry out extensive validation of NWP models across unprecedented range of scales from hundreds of kilometers to tens of meters. However, there are limited observational data available for evaluating high-resolution models. Recently, Nunalee et al (2015) validated large-eddy simulations (LES) using WRF for flow and dispersion based on the Cinder Cone Butte experiment carried out in Idaho in 1982. This study involved moderately complex terrain. We now extend the study to a significantly more complex terrain based on a more recent field study in Idaho. This field study include two experiments: the first one carried out in 2010 and centered on the Big Southern Butte (BSB) and the second in 2011 centered on the Salmon River Canyon both in Idaho (Butler et al., 2015). As a first step, here we focus on using the observations from the BSB experiment to validate multi-scale simulations using the WRF model. We carry out both mesoscale simulations and large-eddy simulations (LES). Nested mesoscale simulations are carried out using the innermost nest with grid cell size of 300m while nested WRF-LES are carried with grid cell size of ~50m. We analyze the performance of PBL scheme in mesoscale simulations and the resulting interplay between subgrid parameterization and numerical advection scheme in LES. The results of this analysis are used to assess performance of PBL schemes in complex terrain where the assumption of horizontal homogeneity on which these schemes are based are violated and to suggest the modifications to PBL scheme to account for the effect of heterogeneity.

  7. Cool-water Eocene-Oligocene carbonate sedimentation on a paleobathymetric high, Kangaroo Island, southern Australia

    NASA Astrophysics Data System (ADS)

    James, Noel P.; Matenaar, Joanne; Bone, Yvonne

    2016-07-01

    The Kingscote Limestone is a thin, biofragmental 41 m thick Paleogene subtropical to cool-temperate carbonate interpreted to have accumulated in a seaway developed between a series of mid-shelf islands. It is a pivotal section that allows interpretation of a region in which there is little exposure of early Cenozoic shelf sediments. Sedimentation occurred on part of the shelf along the northern margin of an extensive Eocene embayment that evolved into a narrow Oligocene ocean following collapse of the Tasman Gateway. Eocene strata are subtropical echinoid-rich floatstones with conspicuous bryozoans, and mollusks, together with large and small benthic foraminifers. Numerous echinoid rudstone storm deposits punctuate the succession. Correlation with coeval Eocene strata across southern Australia supports a regional facies model wherein inner neritic biosiliceous spiculitic sediments passed outboard into calcareous facies. The silica was derived from land covered by a thriving subtropical forest and attendant deep weathering. Oligocene rocks are distinctively cooler cyclic cross-bedded bryozoan rudstones and floatstones with a similar benthic biota but dominated by bryozoans and containing no large benthic foraminifers. These deposits are interpreted as flood-dominated tidal subaqueous dunes that formed in a flood-tide dominated inter-island strait. Omission surfaces at the top of the Eocene and at the top of most Oligocene cycles are Fe-stained hardgrounds that underwent extensive multigeneration seafloor and meteoric diagenesis prior to deposition of the next cycle. Cycles in the Kingscote Limestone, although mostly m-scale and compositionally distinct are similar to those across the region and point to a recurring cycle motif controlled by icehouse eustasy and local paleogeography.

  8. Evaluating effects of climate variability, extreme weather events and thinning on carbon and water exchanges in managed temperate forests in eastern Canada

    NASA Astrophysics Data System (ADS)

    Arain, M.; Brodeur, J. J.; Trant, J.; Thorne, R.; Peichl, M.; Kula, M.; Parsaud, A.; Khader, R.

    2013-12-01

    In this study the impact of climate variability and extreme weather events on gross ecosystem productivity (GEP), ecosystem respiration (RE), net ecosystem productivity (NEP) and evapotranspiration (E) is evaluated in an age-sequence (74-, 39- and 11-years old) of temperate pine (Pinus strobus L.) forests, north of Lake Erie in southern Ontario, Canada using ten years (2003-2012) of eddy covariance flux and meteorological data. Fluxes from conifer stands are also compared with measurements made in an 80-year-old deciduous (Carolinian) forest, established in 2012. All four sites are managed forests and part of the Turkey Point Flux Station and global Fluxnet. Ten-year mean NEP values were 169 (75 to 312), 371 (305 to 456, over 2008-2012) and 141 (-10 to 420) g C/m2/year in the 74-, 39-, and 11-year-old stand, respectively, while mean NEP in the 80-year-old deciduous stand was 286 g C/m2/year in 2012. This region is affected by low frequency climate oscillations, such as El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). The study period experienced four distinct extreme weather patterns: warm and dry springs in 2005 and 2012, extremely wet and warm summer in 2006, a summer drought in 2007 and warm summers in 2010 and 2012. In February-March 2012, the 74-year-old stand was selectively thinned and approximately 30% of trees were removed to improve light and water availability and stimulate growth of remaining trees. Thinning and warm/dry spring reduced NEP in the first post-thinning year, with mean annual NEP of 75 g C/m2/year in 2012. Increased supply of dead organic matter and warm temperatures in 2012 increased RE much more than GEP, resulting in lower annual NEP. Heat stress and drought in spring of 2005 reduced NEP of the 74-year stand to 78 g C/m2/year. The impact of this extreme weather event on NEP was similar to that observed in 2012 when stand experienced a drastic structural change, dry spring and warm temperatures throughout the

  9. Carbon Sequestration Potential in Mangrove Wetlands of Southern of India

    NASA Astrophysics Data System (ADS)

    Chokkalingam, L.; Ponnambalam, K.; Ponnaiah, J. M.; Roy, P.; Sankar, S.

    2012-12-01

    Mangrove forest and the soil on which it grows are major sinks of atmospheric carbon. We present the results of a study on the carbon sequestration in the ground biomass of Avicennia marina including the organic carbon deposition, degradation and preservation in wetland sediments of Muthupet mangrove forest (southeast coast of India) in order to evaluate the influence of forests in the global carbon cycle. The inventory for estimating the ground biomass of Avicennia marina was carried out using random sampling technique (10 m × 10 m plot) with allometric regression equation. The carbon content in different vegetal parts (leaves, stem and root) of mangrove species and associated marshy vegetations was estimated using the combustion method. We observe that the organic carbon was higher (ca. 54.8%) recorded in the stems of Aegiceras corniculatum and Salicornia brachiata and lower (ca. 30.3%) in the Sesuvium portulacastrum leaves. The ground biomass and carbon sequestration of Avicennia marina are 58.56±12.65 t/ ha and 27.52±5.95 mg C/ha, respectively. The depth integrated organic carbon model profiles indicate an average accumulation rate of 149.75gC/m2.yr and an average remineralization rate of 32.89gC/m2.yr. We estimate an oxidation of ca. 21.85% of organic carbon and preservation of ca. 78.15% of organic carbon in the wetland sediments. Keywords: Above ground biomass, organic carbon, sequestration, mangrove, wetland sediments, Muthupet.

  10. The role of internal variability for decadal carbon uptake anomalies in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Spring, Aaron; Hi, Hongmei; Ilyina, Tatiana

    2017-04-01

    The Southern Ocean is a major sink for anthropogenic CO2 emissions and hence it plays an essential role in modulating global carbon cycle and climate change. Previous studies based on observations (e.g., Landschützer et al. 2015) show pronounced decadal variations of carbon uptake in the Southern Ocean in recent decades and this variability is largely driven by internal climate variability. However, due to limited ensemble size of simulations, the variability of this important ocean sink is still poorly assessed by the state-of-the-art earth system models (ESMs). To assess the internal variability of carbon sink in the Southern Ocean, we use a large ensemble of 100 member simulations based on the Max Planck Institute-ESM (MPI-ESM). The large ensemble of simulations is generated via perturbed initial conditions in the ocean and atmosphere. Each ensemble member includes a historical simulation from 1850 to 2005 with an extension until 2100 under Representative Concentration Pathway (RCP) 4.5 future projections. Here we use model simulations from 1980-2015 to compare with available observation-based dataset. We found several ensemble members showing decadal decreasing trends in the carbon sink, which are similar to the trend shown in observations. This result suggests that MPI-ESM large ensemble simulations are able to reproduce decadal variation of carbon sink in the Southern Ocean. Moreover, the decreasing trends of Southern Ocean carbon sink in MPI-ESM are mainly contributed by region between 50-60°S. To understand the internal variability of the air-sea carbon fluxes in the Southern Ocean, we further investigate the variability of underlying processes, such as physical climate variability and ocean biological processes. Our results indicate two main drivers for the decadal decreasing trend of carbon sink: i) Intensified winds enhance upwelling of old carbon-rich waters, this leads to increase of the ocean surface pCO2; ii) Primary production is reduced in area

  11. The DACCIWA model evaluation project: representation of the meteorology of southern West Africa in state-of-the-art weather, seasonal and climate prediction models

    NASA Astrophysics Data System (ADS)

    Kniffka, Anke; Benedetti, Angela; Knippertz, Peter; Stanelle, Tanja; Brooks, Malcolm; Deetz, Konrad; Maranan, Marlon; Rosenberg, Philip; Pante, Gregor; Allan, Richard; Hill, Peter; Adler, Bianca; Fink, Andreas; Kalthoff, Norbert; Chiu, Christine; Vogel, Bernhard; Field, Paul; Marsham, John

    2017-04-01

    DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) is an EU-funded project that aims to determine the influence of anthropogenic and natural emissions on the atmospheric composition, air quality, weather and climate over southern West Africa. DACCIWA organised a major international field campaign in June-July 2016 and involves a wide range of modelling activities. Here we report about the coordinated model evaluation performed in the framework of DACCIWA focusing on meteorological fields. This activity consists of two elements: (a) the quality of numerical weather prediction during the field campaign, (b) the ability of seasonal and climate models to represent the mean state and its variability. For the first element, the extensive observations from the main field campaign in West Africa in June-July 2016 (ground supersites, radiosondes, aircraft measurements) will be combined with conventional data (synoptic stations, satellites data from various sensors) to evaluate models against. The forecasts include operational products from centres such as the ECMWF, UK MetOffice and the German Weather Service and runs specifically conducted for the planning and the post-analysis of the field campaign using higher resolutions (e.g., WRF, COSMO). The forecast and the observations are analysed in a concerted way to assess the ability of the models to represent the southern West African weather systems and secondly to provide a comprehensive synoptic overview of the state of the atmosphere. In a second step the process will be extended to long-term modelling periods. This includes both seasonal and climate models, respectively. In this case, the observational dataset contains long-term satellite observations and station data, some of which were digitised from written records in the framework of DACCIWA. Parameter choice and spatial averaging will build directly on the weather forecasting evaluation to allow an assessment of the impact of short-term errors on

  12. Stock, turnover and functions of carbon in heavily weathered soils under lowland rainforest transformation systems

    NASA Astrophysics Data System (ADS)

    Guillaume, Thomas; Kuzyakov, Yakov

    2013-04-01

    Tropical rainforest are experiencing worldwide a strong lost through deforestation and transformation into agricultural systems. Land use changes in such ecosystems leads to major modifications of soils properties and processes. One indication of it are the losses of organic carbon content (Corg); an important soil fertility parameter in heavily weathered soil. Between 1985 and 2007, Sumatra (Indonesia) has lost half of his remaining natural rainforest, which currently covers only 30% the island. The deforestation is still ongoing and the main drivers of deforestation are oil palm, rubber and timber industries. Our study aims to identify and quantify the impacts of lowland rainforest transformation systems (TS): oil palm, rubber and jungle rubber plantations on soil organic carbon (SOC) and nitrogen (SON) quality, turnover and stocks and so, on soil fertility and functions. We hypothesize that transformation of natural lowland rainforest changes not only C stock and budget throughout quantity and quality of C input, but also DOM production and water consumption by vegetation, leading to a relocation of C in the subsoil. This should be reflected in C and N content in soil profile horizons as well as their δ13C and δ15N isotopic signatures. We will evaluate also C stability through biological, thermal and chemical stability in bulk soil and aggregate fractions. The TS investigated, including lowland rainforest as reference sites, are located in Jambi Province (Sumatra). Soil has been described and sampled per horizon on 4 replicates of each TS in 2 different regions (32 sites) in Autumn 2012. As hypothesized, first results show strong effects of forest transformation on C and N content, as well as on isotopic signatures of soil. Those results will also be used further to select DOM sampling depths and adequate horizons to perform sorption and incubation experiments.

  13. Carbon Monoxide Distributions and Atmosphere Transports over Southern Africa. Pt-2

    NASA Technical Reports Server (NTRS)

    Garstang, Michael; Swap, Robert J.; Piketh, Stuart; Mason, Simon; Connors, Vickie

    1999-01-01

    Sources and transports of CO as measured by the Measurement of Air Pollution from Space (MAPS) over a substantial sector of the southern hemisphere between South America and southern Africa are described by air parcel trajectories based upon European Center for Medium Range Weather Forecasts (ECMWF) model data fields. Observations, made by NASA Shuttle astronauts during the October 1994 mission, of vegetation fires suggest a direct relationship between in situ biomass burning, at least over South America and southern Africa, and coincident tropospheric measurements of CO. Results of this paper indicate that the transport of CO from the surface to the levels of maximum MAPS sensitivity (about 450 hPa) over these regions is not of a direct nature due largely to the well stratified atmospheric environment. The atmospheric transport of CO from biomass burning within this region is found to occur over intercontinental scales over numbers of days to more than a week. Three distinct synoptic circulation and transport classes are found to have occurred over southern Africa during the October 1994 MAPS experiment: (1) transport from South America and Africa to southern Africa associated with elevated MAPS measured CO (> 150 ppbv); (2) weakening anticyclonic transport from South America associated with moderate CO (< 150 ppbv and > 105 ppbv); and (3) transport from the high southern latitudes associated with low CO (<105 ppbv).

  14. Can iron-making and steelmaking slag products be used to sequester CO2? Passive weathering and active carbonation experiments.

    NASA Astrophysics Data System (ADS)

    Worrall, Fred; Dobrzański, Andrew

    2015-04-01

    The high calcium content of iron and steel-making slags has been highlighted as providing a suitable feedstock material and medium with which to sequester CO2 into geologically stable carbonate phases. Optimisation of the natural carbonation process provides the potential for increasing the degree of carbonation above that possible via passive weathering. This study has assessed the baseline passive carbonation potential of several different slag products (graded steel slag aggregate, pellite, GBFS) within the climate of the northern UK. This baseline was then used as a comparison to the carbonation values achieved by the same products when actively reacted in a CO2-rich environment. The active carbonation phase of the project involved a factorial experimental study of materials reacted at 1MPa/10MPa CO2 pressure and 25˚C/125˚C. This study has shown: 1) That active carbonation of these products can successfully sequester additional CO2. 2) Carbonation potential in general is highly dependent upon grain size within material types, 3) There is a material-dependant cost-benefit issue when using different active carbonation conditions as well as the choice to use active vs. passive carbonation. The median sequestration potential of the slag products in this study is equivalent to the total emissions from 910 people from the UK; the CO2 emissions from 10000 tonnes of cement production; or 340000 tonnes of steel production.

  15. Major role of microbes in carbon fluxes during Austral winter in the Southern Drake Passage.

    PubMed

    Manganelli, Maura; Malfatti, Francesca; Samo, Ty J; Mitchell, B Greg; Wang, Haili; Azam, Farooq

    2009-09-14

    Carbon cycling in Southern Ocean is a major issue in climate change, hence the need to understand the role of biota in the regulation of carbon fixation and cycling. Southern Ocean is a heterogeneous system, characterized by a strong seasonality, due to long dark winter. Yet, currently little is known about biogeochemical dynamics during this season, particularly in the deeper part of the ocean. We studied bacterial communities and processes in summer and winter cruises in the southern Drake Passage. Here we show that in winter, when the primary production is greatly reduced, Bacteria and Archaea become the major producers of biogenic particles, at the expense of dissolved organic carbon drawdown. Heterotrophic production and chemoautotrophic CO(2) fixation rates were substantial, also in deep water, and bacterial populations were controlled by protists and viruses. A dynamic food web is also consistent with the observed temporal and spatial variations in archaeal and bacterial communities that might exploit various niches. Thus, Southern Ocean microbial loop may substantially maintain a wintertime food web and system respiration at the expense of summer produced DOC as well as regenerate nutrients and iron. Our findings have important implications for Southern Ocean ecosystem functioning and carbon cycle and its manipulation by iron enrichment to achieve net sequestration of atmospheric CO(2).

  16. Contributions of weather and fuel mix to recent declines in U.S.energy and carbon intensity

    SciTech Connect

    Davis, W. Bart; Sanstad, Alan H.; Koomey, Jonathan G.

    2002-10-20

    A recent (1996-2000) acceleration of declines in energy andcarbon intensity in the U.S. remains largely unexplained. This study usesDivisia decomposition and regression to test two candidate explanations -fuel mix and weather. The Divisia method demonstrates that fuel mix doesnot explain the declines in carbon intensity. The fuel mix, both overalland for electricity generation, became slightly more carbon intensiveover the study period (though the slight trend reversed before the end ofthe period). A regression-based correction to the Divisia indices,accounting for variation in heating- and cooling-degree-days, indicatesthat warmer weather accounts for about 30 percent ofthe total declines.This leaves declines of more than 2 percent per year (and an accelerationof more than 1 percent over previous decade) remaining to beexplained.

  17. Carbon balance of an intensively grazed permanent grassland in southern Belgium

    NASA Astrophysics Data System (ADS)

    Gourlez de la Motte, Louis; Jérôme, Elisabeth; Mamadou, Ossénatou; Beckers, Yves; Bodson, Bernard; Heineisch, Bernard; Aubinet, Marc

    2016-04-01

    Grasslands are an important component of the global carbon balance but their carbon storage potential is still highly uncertain. Especially, the impact of weather variability and management practices on grassland carbon budgets need to be assessed. This study investigates the carbon balance of an intensively managed permanent grassland (Dorinne Terrestrial Observatory (DTO)) and its uncertainties by combining 5-years of eddy covariance measurements and other organic carbon exchanges estimates. The specificities of this study lie in: (i) the age of the pasture, which has probably been established since more than one century; (ii) the intensive character of the management with a mean grazing pressure larger than 2 livestock unit ha-1 and stocking cycle including stocking and rest periods, (iii) the livestock production system, typical of Wallonia, farming intensively Belgian Blue breed of cattle in order to produce meat. The results showed that, despite the high stocking rate and the old age of the pasture and the high stocking rate, the site acted as a relatively stable carbon sink from year to year with a 5-year average Net Biome Productivity of ‒173 [‒128 ‒203] g C m-2 yr-1. The carbon sink behavior of the pasture was directly increased by management practices through food complementation and organic fertilization and indirectly by mineral fertilization. The relatively low carbon budget inter-annual variability could be explained both by: (i) grazing management of the farmer that regulated Growth Primary Productivity by adapting the stocking rate to the Leaf Area Index which itself depends on weather conditions, (ii) carbon imports through food complements only when grass regrowth was not sufficient to feed the cattle. The results suggest that management practices that tend to optimize forage availability for meat production could contribute to maintaining a carbon sink. Keywords : grassland, carbon budget, carbon dioxide flux, management, eddy covariance

  18. The Seasonal Cycle of Carbon in the Southern Pacific Ocean Observed from Biogeochemical Profiling Floats

    NASA Astrophysics Data System (ADS)

    Sarmiento, J. L.; Gray, A. R.; Johnson, K. S.; Carter, B.; Riser, S.; Talley, L. D.; Williams, N. L.

    2016-02-01

    The Southern Ocean is thought to play an important role in the ocean-atmosphere exchange of carbon dioxide and the uptake of anthropogenic carbon dioxide. However, the total number of observations of the carbonate system in this region is small and heavily biased towards the summer. Here we present 1.5 years of biogeochemical measurements, including pH, oxygen, and nitrate, collected by 11 autonomous profiling floats deployed in the Pacific sector of the Southern Ocean in April 2014. These floats sampled a variety of oceanographic regimes ranging from the seasonally ice-covered zone to the subtropical gyre. Using an algorithm trained with bottle measurements, alkalinity is estimated from salinity, temperature, and oxygen and then used together with the measured pH to calculate total carbon dioxide and pCO2 in the upper 1500 dbar. The seasonal cycle in the biogeochemical quantities is examined, and the factors governing pCO2 in the surface waters are analyzed. The mechanisms driving the seasonal cycle of carbon are further investigated by computing budgets of heat, carbon, and nitrogen in the mixed layer. Comparing the different regimes sampled by the floats demonstrates the complex and variable nature of the carbon cycle in the Southern Ocean.

  19. Understanding the recent changes in the Southern Ocean carbon cycle: A multidisciplinary approach

    NASA Astrophysics Data System (ADS)

    Manizza, M.; Kahru, M.; Menemenlis, D.; Nevison, C. D.; Mitchell, B. G.; Keeling, R. F.

    2016-12-01

    The Southern Ocean represents a key area of the global ocean for the uptake of the CO2 originating from fossil fuels emissions. In these waters, cold temperatures combined with high rates of biological production drive the carbon uptake that accounts for about one-third of the global ocean uptake.Recent studies showed that changes in the Southern Annular Mode (SAM) index, mainly a proxy of the intensity of westerly winds, had a significant impact on the temporal variability of the CO2 uptake in the Southern Ocean. In order to shed light on this problem we propose to use both satellite-derived estimates of ocean productivity and carbon export in combinations of ocean physical and biogeochemical state estimates focusing on the 2006-2013 period. While the estimates of carbon fixation and export based on remote sensing will provide key information on the spatial and temporal variations of the biological carbon pump, the ocean state estimates will provide additional information on physical and carbon cycle processes, including the air-sea CO2 fluxes of the Southern Ocean in the 2006-2013 period where model solutions have been optimized.These physical estimates will be used to force an ocean biogeochemical model (ECCO2-Darwin) that will compute the CO2 uptake for each year. The physical model, forced with optimized atmospheric forcing, aims to realistically simulate interannual ocean climate variability that drives changes in both physical and biogeochemical processes ultimately impacting the carbon uptake of the Southern Ocean, and potentially responding to the SAM index variations.Although in this study great emphasis is given to the role of physical climate variations at driving the CO2 uptake of these polar waters, we will integrate model results with estimates from remote sensing techniques to better understand role of the biological carbon pump and its variability potentially responding to the SAM index changes.

  20. Impact of organic carbon on weathering and chemical denudation of granular basalt

    NASA Astrophysics Data System (ADS)

    Dontsova, Katerina; Zaharescu, Dragos; Henderson, Whitney; Verghese, Sarah; Perdrial, Nicolas; Hunt, Edward; Chorover, Jon

    2014-08-01

    Bench-scale experiments were conducted to determine rates and patterns of coupled organic matter infusion and weathering in a San Francisco volcanic field (Flagstaff, AZ) basalt sample under experimentally-modeled biotic and abiotic condition and to inform larger-scale collaborative studies at the landscape evolution observatory (LEO), Biosphere 2 (Tucson, AZ), where the same basaltic media is being used in a synthetic hillslope experiment. We postulated that mineral transformations depend significantly on the presence of organic carbon compounds including dissolved natural organic matter (DOM), with organic C simultaneously imprinting the chemical and mineralogical properties of primary and secondary solids undergoing incongruent dissolution. The present work reports on solute releases from Flagstaff basalt (FB) along laboratory-controlled gradients in DOM type and concentration. Loamy sand textured FB was subjected to flow-through, saturated column dissolution experiments using influent solutions with and without DOM compounds. Solutions included Ponderosa pine forest soil O-horizon extracts at three target concentrations: 7, 35, and 70 mg L-1 C, malic acid (MA) solutions at 7, 35, 70, and 140 mg L-1 C, and a control without DOM but having comparable inorganic solution composition. Chemical denudation rates for FB dissolution products were calculated from the concentration difference between outflow and inflow solutions. In addition, changes in the composition of the solid phase over the course of the experiment were determined using X-ray diffraction (XRD), X-ray fluorescence (XRF), and selective dissolution (SE). Column experiments supported dissolution rates derived from the literature and indicated a potentially strong effect of plant-derived organic ligands on mineral dissolution congruency and secondary phase precipitation. Both malic acid and DOM enhanced basalt dissolution, with malic acid having larger effect on per unit C basis. The largest relative

  1. The Carbon Balance of Semi-Arid Ecosystems: Why Southern Africa Carbon-Climate Dynamics are uniquely different

    NASA Astrophysics Data System (ADS)

    Lawal, S. A.; Fisher, J. B.

    2015-12-01

    Previous studies by Poulter et al (2014) and Alhstrom et al (2015) have shown that the semi-arid ecosystems (e.g. Australia) can dramatically alter the regional and global net carbon sink/source status depending on sporadic precipitation. For example, the unprecedented huge carbon sink which occurred in 2011 was mainly due to the growth semi-arid vegetation over Australia; which was driven by increased precipitation. Thus, we sought to uncover if this was the case with the semi-arid ecosystems in southern Africa. We used 10 models from the "Trends In Net Land-Atmosphere Carbon Exchange - Model Inter comparison Project (TRENDY-MIP)" to evaluate response of southern Africa semi-arid ecosystems to precipitation in the 20th century. Our study revealed that the sensitivities and net carbon source/sink dynamics in these ecosystems are distinctly different from those elsewhere owing to opposite climate anomalies; i.e. the region receives sporadic precipitation drops, rather than spikes which is the case in other semi-arid regions. The implications for this study is explored in an ecosystem services context for future trajectories of the region as the ability of the ecosystems to continually provide such services directly depends on the soaring population rise in the region. Key words: Semi-arid ecosystem, Southern Africa, TRENDY-MIP, Carbon dynamics and climate change.

  2. Weathering of a carbon nanotube/epoxy nanocomposite under UV light and in water bath: impact on abraded particles

    NASA Astrophysics Data System (ADS)

    Schlagenhauf, Lukas; Kianfar, Bahareh; Buerki-Thurnherr, Tina; Kuo, Yu-Ying; Wichser, Adrian; Nüesch, Frank; Wick, Peter; Wang, Jing

    2015-11-01

    Weathering processes can influence the surface properties of composites with incorporated nanoparticles. These changes may affect the release behavior of nanoparticles when an abrasion process is applied. Therefore, the influence of two different weathering processes, immersion in water and exposure to UV light, on the properties of abraded particles from a carbon nanotube (CNT)/epoxy nanocomposite was investigated. The investigation included the measurement of the weathering impact on the surface chemistry of the exposed samples, the particle size of abraded particles, the quantity of exposed CNTs in the respirable part of the abraded particles, and the toxicity of abraded particles, measured by in vitro toxicity tests using the THP-1 monocyte-derived macrophages. The results showed that weathering by immersion in water had no influence on the properties of abraded particles. The exposure to UV light caused a degradation of the epoxy on the surface, followed by delamination of an approx. 2.5 μm thick layer. An increased quantity of exposed CNTs in abraded particles was not found; on the contrary, longer UV exposure times decreased the released fraction of CNTs from 0.6% to 0.4%. The toxicity tests revealed that abraded particles from the nanocomposites did not induce additional acute cytotoxic effects compared to particles from the neat epoxy.Weathering processes can influence the surface properties of composites with incorporated nanoparticles. These changes may affect the release behavior of nanoparticles when an abrasion process is applied. Therefore, the influence of two different weathering processes, immersion in water and exposure to UV light, on the properties of abraded particles from a carbon nanotube (CNT)/epoxy nanocomposite was investigated. The investigation included the measurement of the weathering impact on the surface chemistry of the exposed samples, the particle size of abraded particles, the quantity of exposed CNTs in the respirable part of

  3. Southern Milky Way carbon stars - New candidates, JHK photometry, and radial velocities

    SciTech Connect

    Blanco, V.M.; Cook, K.H.; Schechter, P.L.; Aaronson, M.; Steward Observatory, Tucson, AZ; Mount Wilson and Las Campanas Observatories, Pasadena, CA )

    1989-07-01

    Data are presented for low-latitude southern Milky Way carbon stars. Coordinates and cross identifications are given for carbon stars (67 of which are confirmed new discoveries) in seven fields deemed to be unusually transparent. JHK photometry is presented for 520 stars. Velocities are presented for 393 stars. Improved coordinates are presented for selected stars in Westerlund's catalog. Averaged photometry and velocities are presented for a sample of 336 stars. 26 refs.

  4. Carbonate Mineral Weathering Contributions to the HCO3- Flux from Headwater Mid-latitude Streams in the Face of Increasing Atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Szramek, K.; Ogrinc, N.; Walter, L. M.

    2007-12-01

    As anthropogenic liberated CO2 increases in the atmosphere, landscape level responses of the carbon cycle to perturbations associated with global warming are likely to be observed in carbonate bearing regions. Within physically open weathering environments, carbonate (calcite and dolomite) mineral solubility is proportional to pCO2 and inversely proportional to temperature, with the solubility of dolomite progressively greater than calcite below 25°C. Changes in weathering zone CO2 occur as CO2 drawdown is increased due to CO2 fertilization effects on plant growth, to warmer mean annual temperatures, or to land use changes. The rise in weathering zone CO2 will significantly augment the open system solubility of carbonate minerals and increase the DIC content of surface waters (unconfined groundwaters and rivers). The thermodynamic relationships between calcite and dolomite indicate the further need to examine the role of dolomite on the global riverine DIC budget. On a continental scale, the global weathering budget indicates the importance of northern hemisphere landmasses to riverine fluxes of Ca2+, Mg2+ and DIC as HCO3-. The results of a hydrogeochemical study of carbonate mineral equilibria and weathering fluxes for headwater streams within the Danube, the James and the St. Lawrence River Basins is presented. Available long-term geochemical and discharge data along with detailed catchment geochemical views of surface water and soil weathering zones were determined to examine the historical and current contribution of carbonate weathering to the geochemical fluctuations of the these headwater regions and the ability of these watersheds to maintain current conditions in the facing of increasing CO2. In order to gauge how these streams with variable climates, land use practices, lithologies, and weathering zone thicknesses compare to each other, river runoff and HCO3- concentrations are normalized to catchment area. The resulting carbonate weathering intensity on

  5. Effects of Carbon Addition on Iron and Phosphorus in a Highly Weathered Tropical Soil

    NASA Astrophysics Data System (ADS)

    Liptzin, D.; Silver, W. L.

    2008-12-01

    In the highly weathered iron (Fe)-rich soils of wet tropical forests, Fe may play a key role in controlling ecosystem processes because of its interactions with carbon (C) and phosphorus (P). The high NPP typical of tropical forests contributes significantly to the global C cycle. In Fe-rich tropical soils, NPP is thought to be limited by P. The periodic reducing conditions that occur in upland tropical soils may be associated with pulses of increased P availability because of the release of Fe-bound P during iron reduction. While little is known about the factors controlling Fe reduction in soils, it is likely that C availability plays a role. Typically, only simple C sources like acetate or glucose have been used to examine this limitation. However, the source of much of the C in nature is the complex mixture of organic compounds leached from leaves and litter. To investigate the linkages between Fe, C, and P, we compared the effects adding either acetate (200 mg C/L) or leaf leachate in low (50-100 mg C/L) or high (150-200 mg C/L) concentrations to incubated soils from a tropical rain forest in Puerto Rico under ambient atmospheric conditions. We measured pools of iron and phosphorus as well as pH at four time points over a month. Both Fe(II) and pH exhibited significant treatment effects, but not until the last sampling date. At this time, the Fe(II) concentration could explain 49% of the variability in soil pH. The pH was significantly higher in the acetate treatments than both the leaf leachate treatments. While Fe(II) concentration was significantly higher in the acetate treatment than the control and low leaf leachate treatment, there was no difference compared to the high leaf leachate treatment After one month microbial biomass P had increased significantly while the NaOH extractable organic P had decreased significantly. These changes suggest the rapid microbial uptake of P liberated from Fe. In conclusion, microbes appear to utilize more complex C in

  6. Using silviculture to influence carbon sequestration in southern Appalachian spruce-fir forests

    Treesearch

    Patrick T. Moore; R. Justin DeRose; James N. Long; Helga. van Miegroet

    2012-01-01

    Enhancement of forest growth through silvicultural modification of stand density is one strategy for increasing carbon (C) sequestration. Using the Fire and Fuels Extension of the Forest Vegetation Simulator, the effects of even-aged, uneven-aged and no-action management scenarios on C sequestration in a southern Appalachian red spruce-Fraser fir forest were modeled....

  7. Estimating long-term carbon sequestration patterns in even- and uneven-aged southern pine stands

    Treesearch

    Don C. Bragg; James M. Guldin

    2010-01-01

    Carbon (C) sequestration has become an increasingly important consideration for forest management in North America, and has particular potential in pine-dominated forests of the southern United States. Using existing literature on plantations and long-term studies of naturally regenerated loblolly (Pinus taeda) and shortleaf (Pinus echinata) pine-dominated stands on...

  8. Forest and pasture carbon pools and soil respiration in the southern Appalachian mountains

    Treesearch

    Paul V. Bolstad; James M. Vose

    2005-01-01

    Our ability to estimate the changes in carbon (C) pools and fluxes due to forest conversion is hampered by a lack of comparative studies. We measured above- and belowground C pools and soil respiration flux at four forested and four pasture sites in the southern Appalachian Mountains. Above- and belowground C pools were significantly larger (P

  9. Comparison of recreational health risks associated with surfing and swimming in dry weather and post-storm conditions at Southern California beaches using quantitative microbial risk assessment (QMRA).

    PubMed

    Tseng, Linda Y; Jiang, Sunny C

    2012-05-01

    Southern California is an increasingly urbanized hotspot for surfing, thus it is of great interest to assess the human illness risks associated with this popular ocean recreational water sport from exposure to fecal bacteria contaminated coastal waters. Quantitative microbial risk assessments were applied to eight popular Southern California beaches using readily available enterococcus and fecal coliform data and dose-response models to compare health risks associated with surfing during dry weather and storm conditions. The results showed that the level of gastrointestinal illness risks from surfing post-storm events was elevated, with the probability of exceeding the US EPA health risk guideline up to 28% of the time. The surfing risk was also elevated in comparison with swimming at the same beach due to ingestion of greater volume of water. The study suggests that refinement of dose-response model, improving monitoring practice and better surfer behavior surveillance will improve the risk estimation.

  10. Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, supply nutrients, and mitigate ocean acidification

    NASA Astrophysics Data System (ADS)

    Hartmann, Jens; West, A. Joshua; Renforth, Phil; KöHler, Peter; de La Rocha, Christina L.; Wolf-Gladrow, Dieter A.; Dürr, Hans H.; Scheffran, Jürgen

    2013-04-01

    weathering is an integral part of both the rock and carbon cycles and is being affected by changes in land use, particularly as a result of agricultural practices such as tilling, mineral fertilization, or liming to adjust soil pH. These human activities have already altered the terrestrial chemical cycles and land-ocean flux of major elements, although the extent remains difficult to quantify. When deployed on a grand scale, Enhanced Weathering (a form of mineral fertilization), the application of finely ground minerals over the land surface, could be used to remove CO2 from the atmosphere. The release of cations during the dissolution of such silicate minerals would convert dissolved CO2 to bicarbonate, increasing the alkalinity and pH of natural waters. Some products of mineral dissolution would precipitate in soils or be taken up by ecosystems, but a significant portion would be transported to the coastal zone and the open ocean, where the increase in alkalinity would partially counteract "ocean acidification" associated with the current marked increase in atmospheric CO2. Other elements released during this mineral dissolution, like Si, P, or K, could stimulate biological productivity, further helping to remove CO2 from the atmosphere. On land, the terrestrial carbon pool would likely increase in response to Enhanced Weathering in areas where ecosystem growth rates are currently limited by one of the nutrients that would be released during mineral dissolution. In the ocean, the biological carbon pumps (which export organic matter and CaCO3 to the deep ocean) may be altered by the resulting influx of nutrients and alkalinity to the ocean. This review merges current interdisciplinary knowledge about Enhanced Weathering, the processes involved, and the applicability as well as some of the consequences and risks of applying the method.

  11. Carbon-14 Measurements in Atmospheric CO2 from Northern and Southern Hemisphere Sites, 1962-1993

    SciTech Connect

    Nydal, R.; Loevseth, K.

    1996-11-01

    In the 1960s, thermonulcear bomb test released significant pulses of radioactive carbon 14 into the atmosphere. This major perturbation allowed scientist to study the dynamics of the global carbon cycle by measuring and observing rates isotopic exchange. The Radiological Dating Laboratory at the Norwegian Institute to Technology performed carbon 14 measurements in atmospheric carbon dioxide from 1962 until 1993 at a network of ground stations in the Northern and Southern hemispheres. These measurements were supplemented during 1965 with high- altitude samples collected using aircraft from the Norwegian Air Force. The resulting database, coupled with other carbon 14 measurements, broad spatial coverage of sampling, consistency of sampling method, and the change in carbon 14 calculation results corrected for isotopic fractionation and radioactive decay. This database replaces previous versions published by the authors and the Radiological Dating Laboratory.

  12. Anthropogenic carbon dioxide transport in the Southern Ocean driven by Ekman flow.

    PubMed

    Ito, T; Woloszyn, M; Mazloff, M

    2010-01-07

    The Southern Ocean, with its large surface area and vigorous overturning circulation, is potentially a substantial sink of anthropogenic CO(2) (refs 1-4). Despite its importance, the mechanism and pathways of anthropogenic CO(2) uptake and transport are poorly understood. Regulation of the Southern Ocean carbon sink by the wind-driven Ekman flow, mesoscale eddies and their interaction is under debate. Here we use a high-resolution ocean circulation and carbon cycle model to address the mechanisms controlling the Southern Ocean sink of anthropogenic CO(2). The focus of our study is on the intra-annual variability in anthropogenic CO(2) over a two-year time period. We show that the pattern of carbon uptake is correlated with the oceanic vertical exchange. Zonally integrated carbon uptake peaks at the Antarctic polar front. The carbon is then advected away from the uptake regions by the circulation of the Southern Ocean, which is controlled by the interplay among Ekman flow, ocean eddies and subduction of water masses. Although lateral carbon fluxes are locally dominated by the imprint of mesoscale eddies, the Ekman transport is the primary mechanism for the zonally integrated, cross-frontal transport of anthropogenic CO(2). Intra-annual variability of the cross-frontal transport is dominated by the Ekman flow with little compensation from eddies. A budget analysis in the density coordinate highlights the importance of wind-driven transport across the polar front and subduction at the subtropical front. Our results suggest intimate connections between oceanic carbon uptake and climate variability through the temporal variability of Ekman transport.

  13. Radiocarbon Depression in Aquatic Foodwebs of the Colorado River, USA: Coupling Between Carbonate Weathering and the Biosphere

    NASA Astrophysics Data System (ADS)

    Sickman, J. O.; Huang, W.; Lucero, D.; Anderson, M.

    2012-12-01

    The 14C isotopic composition of living organisms is generally considered to be in isotopic equilibrium with atmosphere CO2. During the course of investigations of aquatic foodwebs of the Colorado River, we measured substantial radiocarbon depression of organisms within planktonic and benthic foodwebs of Copper Basin Reservoir, a short residence-time water body at the intake to the Colorado River Aqueduct. All trophic levels had depressed radiocarbon content with inferred "age" of ca. 1,200 radiocarbon years (range: 0.85 to 0.87 fraction modern carbon (fmc)). Additional measurements of the radiocarbon content of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) were made in other major rivers in California (New (near Salton Sea), Santa Ana (near Riverside), San Joaquin (near Fresno) and Salinas (near San Luis Obispo)). In the New River (which is composed primarily of irrigation tailwater derived from the Colorado River), the radiocarbon values for DIC closely matched those found in biota of the Copper Basin Reservoir (0.85 to 0.87 fmc), but radiocarbon values for DOC were slightly higher (0.91 to 0.95 fmc). In the other California rivers, radiocarbon concentrations in DIC were generally below modern and lower than corresponding levels in DOC; in the case of the Santa Ana River, DOC was older than DIC as a result of wastewater inputs from upstream treatment plants. Together these data suggest that the carbonate equilibrium of California rivers is influenced by weathering of carbonate minerals which produces HCO3- with no 14C. We hypothesize that this dead carbon can move into aquatic foodwebs via algae and phytoplankton uptake during photosynthesis, depressing the 14C content of aquatic foodwebs below that of the atmosphere. Based on a simple two-component mixing model incorporating carbonate weathering and atmospheric CO2, we estimate that 15-17% of the carbon in the aquatic foodweb of Copper Basin is derived directly from mineral weathering of

  14. The significance of biomass burning as a source of carbon monoxide and ozone in the Southern Hemisphere tropics - A satellite analysis

    NASA Technical Reports Server (NTRS)

    Watson, Catherine E.; Fishman, Jack; Reichle, Henry G., Jr.

    1990-01-01

    Carbon monoxide mixing ratios obtained by the October 1984 Measurement of Air Pollution from Satellites (MAPS) experiment are compared with the distribution of October 1984 Total Ozone Mapping Spectrometer (TOMS) ozone concentrations. The TOMS and MAPS data show coincident high values of ozone and carbon monoxide over central South America and southeastern Africa. The 1984 MAPS data are also compared with tropospheric ozone concentrations derived from 6 years of TOMS and Stratospheric Aerosol and Gas Experiment (SAGE) I and II measurements. Examination of the October climatological distribution of tropospheric ozone also reveals high concentrations over central South America and southeastern Africa. These coincident high values of CO and ozone in the rural southern tropics are most likely due to biomass burning and the subsequent transport of CO and ozone by large-scale weather patterns. It appears that both CO and ozone are being transported thousands of kilometers from their source regions by the prevailing winds.

  15. Silicate Weathering and Pervasive Authigenic Carbonate Precipitation Coupled to Methanogenesis in the Krishna-Godavari Basin, Offshore India

    NASA Astrophysics Data System (ADS)

    Solomon, E. A.; Spivack, A. J.; Kastner, M.; Torres, M. E.

    2014-12-01

    The cycling of methane in marine sediments has been actively studied for the past several decades, but less attention has been paid to the cycling of CO2 produced in methanogenic sediments. The National Gas Hydrate Program Expedition 01 cored 10 sites with the Joides Resolution drillship in the Krishna-Godavari basin, located on the southeastern margin of India. A comprehensive suite of pore water solute concentrations and isotope ratios were analyzed to investigate the distribution and concentration of gas hydrate along the margin, in situ diagenetic and metabolic reactions, fluid migration and flow pathways, and fluid and gas sources. This represents one of the most comprehensive pore water geochemical datasets collected at a continental margin to date, and provides the necessary tracers to better understand the processes and sinks controlling CO2 in margin sediments. Our results show that the CO2 produced through net microbial methanogenesis is effectively neutralized through silicate weathering throughout the sediment column drilled at each site (~100-300 m), buffering the pH of the sedimentary pore water and generating excess alkalinity through the same reaction sequence as continental silicate weathering. Most of the excess alkalinity produced through silicate weathering in the Krishna-Godavari basin is sequestered in Ca- and Fe-carbonates as a result of ubiquitous calcium release from weathering detrital silicates and Fe-reduction within the methanogenic sediments. Formation of secondary hydrous silicates (e.g. smectite) related to incongruent primary silicate dissolution acts as a significant sink for pore water Mg, K, Li, Rb, and B. The consumption of methane through anaerobic oxidation of methane, sequestration of methane in gas hydrate, and sequestration of dissolved inorganic carbon in authigenic carbonates keeps methanogenesis as a thermodynamically feasible catabolic pathway. Our results combined with previous indications of silicate weathering in

  16. A Spatial Hierarchical Analysis of the Temporal Influences of the El Niño-Southern Oscillation and Weather on Dengue in Kalutara District, Sri Lanka

    PubMed Central

    Liyanage, Prasad; Tissera, Hasitha; Sewe, Maquins; Quam, Mikkel; Amarasinghe, Ananda; Palihawadana, Paba; Wilder-Smith, Annelies; Louis, Valérie R.; Tozan, Yesim; Rocklöv, Joacim

    2016-01-01

    Dengue is the major public health burden in Sri Lanka. Kalutara is one of the highly affected districts. Understanding the drivers of dengue is vital in controlling and preventing the disease spread. This study focuses on quantifying the influence of weather variability on dengue incidence over 10 Medical Officer of Health (MOH) divisions of Kalutara district. Weekly weather variables and data on dengue notifications, measured at 10 MOH divisions in Kalutara from 2009 to 2013, were retrieved and analysed. Distributed lag non-linear model and hierarchical-analysis was used to estimate division specific and overall relationships between weather and dengue. We incorporated lag times up to 12 weeks and evaluated models based on the Akaike Information Criterion. Consistent exposure-response patterns between different geographical locations were observed for rainfall, showing increasing relative risk of dengue with increasing rainfall from 50 mm per week. The strongest association with dengue risk centred around 6 to 10 weeks following rainfalls of more than 300 mm per week. With increasing temperature, the overall relative risk of dengue increased steadily starting from a lag of 4 weeks. We found similarly a strong link between the Oceanic Niño Index to weather patterns in the district in Sri Lanka and to dengue at a longer latency time confirming these relationships. Part of the influences of rainfall and temperature can be seen as mediator in the causal pathway of the Ocean Niño Index, which may allow a longer lead time for early warning signals. Our findings describe a strong association between weather, El Niño-Southern Oscillation and dengue in Sri Lanka. PMID:27827943

  17. A Spatial Hierarchical Analysis of the Temporal Influences of the El Niño-Southern Oscillation and Weather on Dengue in Kalutara District, Sri Lanka.

    PubMed

    Liyanage, Prasad; Tissera, Hasitha; Sewe, Maquins; Quam, Mikkel; Amarasinghe, Ananda; Palihawadana, Paba; Wilder-Smith, Annelies; Louis, Valérie R; Tozan, Yesim; Rocklöv, Joacim

    2016-11-04

    Dengue is the major public health burden in Sri Lanka. Kalutara is one of the highly affected districts. Understanding the drivers of dengue is vital in controlling and preventing the disease spread. This study focuses on quantifying the influence of weather variability on dengue incidence over 10 Medical Officer of Health (MOH) divisions of Kalutara district. Weekly weather variables and data on dengue notifications, measured at 10 MOH divisions in Kalutara from 2009 to 2013, were retrieved and analysed. Distributed lag non-linear model and hierarchical-analysis was used to estimate division specific and overall relationships between weather and dengue. We incorporated lag times up to 12 weeks and evaluated models based on the Akaike Information Criterion. Consistent exposure-response patterns between different geographical locations were observed for rainfall, showing increasing relative risk of dengue with increasing rainfall from 50 mm per week. The strongest association with dengue risk centred around 6 to 10 weeks following rainfalls of more than 300 mm per week. With increasing temperature, the overall relative risk of dengue increased steadily starting from a lag of 4 weeks. We found similarly a strong link between the Oceanic Niño Index to weather patterns in the district in Sri Lanka and to dengue at a longer latency time confirming these relationships. Part of the influences of rainfall and temperature can be seen as mediator in the causal pathway of the Ocean Niño Index, which may allow a longer lead time for early warning signals. Our findings describe a strong association between weather, El Niño-Southern Oscillation and dengue in Sri Lanka.

  18. Weathering of a carbon nanotube/epoxy nanocomposite under UV light and in water bath: impact on abraded particles.

    PubMed

    Schlagenhauf, Lukas; Kianfar, Bahareh; Buerki-Thurnherr, Tina; Kuo, Yu-Ying; Wichser, Adrian; Nüesch, Frank; Wick, Peter; Wang, Jing

    2015-11-28

    Weathering processes can influence the surface properties of composites with incorporated nanoparticles. These changes may affect the release behavior of nanoparticles when an abrasion process is applied. Therefore, the influence of two different weathering processes, immersion in water and exposure to UV light, on the properties of abraded particles from a carbon nanotube (CNT)/epoxy nanocomposite was investigated. The investigation included the measurement of the weathering impact on the surface chemistry of the exposed samples, the particle size of abraded particles, the quantity of exposed CNTs in the respirable part of the abraded particles, and the toxicity of abraded particles, measured by in vitro toxicity tests using the THP-1 monocyte-derived macrophages. The results showed that weathering by immersion in water had no influence on the properties of abraded particles. The exposure to UV light caused a degradation of the epoxy on the surface, followed by delamination of an approx. 2.5 μm thick layer. An increased quantity of exposed CNTs in abraded particles was not found; on the contrary, longer UV exposure times decreased the released fraction of CNTs from 0.6% to 0.4%. The toxicity tests revealed that abraded particles from the nanocomposites did not induce additional acute cytotoxic effects compared to particles from the neat epoxy.

  19. Forest carbon trends in the Southern United States

    Treesearch

    Robert A. Mickler; James E. Smith; Linda S. Heath

    2004-01-01

    Forest, agricultural, rangeland, wetland, and urban landscapes have different rates of carbon (C) sequestration and total C sequestration potential under alternative management options. Future changes in the proportion and spatial distribution of land use could increase or decrease the capacity of areas to sequester C in terrestrial ecosystems. As the ecosystems within...

  20. Controls on carbon storage and weathering in volcanic soils across a high-elevation climate gradient on Mauna Kea, Hawaii.

    PubMed

    Kramer, Marc G; Chadwick, Oliver A

    2016-09-01

    Volcanic ash soils retain the largest and most persistent soil carbon pools of any ecosystem. However, the mechanisms governing soil carbon accumulation and weathering during initial phases of ecosystem development are not well understood. We examined soil organic matter dynamics and soil development across a high-altitude (3,560-3,030 m) 20-kyr climate gradient on Mauna Kea in Hawaii. Four elevation sites were selected (~250-500 mm rainfall), which range from sparsely vegetated to sites that contain a mix of shrubs and grasses. At each site, two or three pits were dug and major diagnostic horizons down to bedrock (intact lava) were sampled. Soils were analyzed for particle size, organic C and N, soil pH, exchangeable cations, base saturation, NaF pH, phosphorous sorption, and major elements. Mass loss and pedogenic metal accumulation (hydroxlamine Fe, Al, and Si extractions) were used to measure extent of weathering, leaching, changes in soil mineralogy and carbon accumulation. Reactive-phase (SRO) minerals show a general trend of increasing abundance with increasing rainfall. However carbon accumulation patterns across the climate gradient are largely decoupled from these trends. The results suggest that after 20 kyr, pedogenic processes have altered the nature and composition of the volcanic ash such that it is capable of retaining soil C even where organic acid influences from plant material and leaching from rainfall are severely limited. Carbon storage comparisons with lower-elevation soils on Mauna Kea and other moist mesic (2,500 mm rainfall) sites on Hawaii suggest that these soils have reached only between 1% and 15% of their capacity to retain carbon. Our results suggest that, after 20 kyr in low rainfall and a cold climate, weathering was decoupled from soil carbon accumulation patterns and the associated influence of vegetation on soil development. Overall, we conclude that the rate of carbon supply to the subsoil (driven by coupling of rainfall

  1. Biotic enhancement of weathering, atmospheric oxygen and carbon dioxide in the Neoproterozoic

    NASA Astrophysics Data System (ADS)

    Lenton, Timothy M.; Watson, Andrew J.

    2004-03-01

    It has been suggested that biological colonization of the land surface began in the Neoproterozoic 1000-544 million years ago (Ma). We hypothesize that this colonization involved selective weathering of P from rocks, as well as an amplification of overall weathering rates. We show that two recent models, despite differences in the feedback mechanisms represented, predict that an increase in the weathering flux of P to the ocean would have caused a rise in atmospheric O2 in the Neoproterozoic. This in turn may have provided a necessary condition for the evolution of animals with hard skeletons seen in the 'Cambrian explosion'. Increased weathering of silicate rocks would also have caused a decline in atmospheric CO2, which could have been a causal factor in the Neoproterozoic glaciations.

  2. Uranium-series dated authigenic carbonates and acheulian sites in southern Egypt

    USGS Publications Warehouse

    Szabo, B. J.; McHugh, W.P.; Schaber, G.G.; Haynes, C.V.; Breed, C.S.

    1989-01-01

    Field investigations in southern Egypt have yielded Acheulian artifacts in situ in authigenic carbonate deposits (CaCO3-cemented alluvium) along the edges of nowaggraded paleovalleys (Wadi Arid and Wadi Safsaf). Uranium-series dating of 25 carbonate samples from various localities as far apart as 70 kilometers indicates that widespread carbonate deposition occurred about 45, 141 and 212 ka (thousand years ago). Most of the carbonate appears to have been precipitated from groundwater, which suggests that these three episodes of deposition may be related to late Pleistocene humid climates that facilitated human settlement in this now hyperarid region. Carbonate cements from sediments containing Acheulian artifacts provide a minimum age of 212 ka for early occupation of the paleovalleys.

  3. A stochastic ensemble-based model to predict crop water requirements from numerical weather forecasts and VIS-NIR high resolution satellite images in Southern Italy

    NASA Astrophysics Data System (ADS)

    Pelosi, Anna; Falanga Bolognesi, Salvatore; De Michele, Carlo; Medina Gonzalez, Hanoi; Villani, Paolo; D'Urso, Guido; Battista Chirico, Giovanni

    2015-04-01

    Irrigation agriculture is one the biggest consumer of water in Europe, especially in southern regions, where it accounts for up to 70% of the total water consumption. The EU Common Agricultural Policy, combined with the Water Framework Directive, imposes to farmers and irrigation managers a substantial increase of the efficiency in the use of water in agriculture for the next decade. Ensemble numerical weather predictions can be valuable data for developing operational advisory irrigation services. We propose a stochastic ensemble-based model providing spatial and temporal estimates of crop water requirements, implemented within an advisory service offering detailed maps of irrigation water requirements and crop water consumption estimates, to be used by water irrigation managers and farmers. The stochastic model combines estimates of crop potential evapotranspiration retrieved from ensemble numerical weather forecasts (COSMO-LEPS, 16 members, 7 km resolution) and canopy parameters (LAI, albedo, fractional vegetation cover) derived from high resolution satellite images in the visible and near infrared wavelengths. The service provides users with daily estimates of crop water requirements for lead times up to five days. The temporal evolution of the crop potential evapotranspiration is simulated with autoregressive models. An ensemble Kalman filter is employed for updating model states by assimilating both ground based meteorological variables (where available) and numerical weather forecasts. The model has been applied in Campania region (Southern Italy), where a satellite assisted irrigation advisory service has been operating since 2006. This work presents the results of the system performance for one year of experimental service. The results suggest that the proposed model can be an effective support for a sustainable use and management of irrigation water, under conditions of water scarcity and drought. Since the evapotranspiration term represents a staple

  4. Southern Ocean Carbon Sink Constraints from Radiocarbon in Drake Passage Air

    NASA Astrophysics Data System (ADS)

    Lindsay, C. M.; Lehman, S.; Miller, J. B.

    2014-12-01

    The Southern Ocean is one of the earth's largest regional net carbon sinks due to strong westerly winds, which drive surface gas exchange, deep mixing and upwelling. The strength of the sink is set by complex interactions between the physical circulation, gas exchange and biological activity in surface waters. Recent work by others has predicted that global warming may weaken the sink by strengthening the regional winds, increasing upwelling and the flux of deep, naturally carbon-rich and radiocarbon-depleted water into the surface mixed layer. The resulting decrease in the air-sea pCO2 gradient is thought to overwhelm other compensating changes, causing a weakened net sink. Here we demonstrate the use of precise measurements of radiocarbon in Drake Passage air (14CO2) to detect short-term fluctuations in the Southern Ocean gross sea-to-air C flux, and by extension, possible changes in the net carbon sink and their underlying causes. Drake Passage boundary layer air has been sampled since 2006 at roughly fortnightly intervals as part of NOAA's Cooperative Air Sampling Network, resulting in a 5-year high-resolution 14CO2 time-series with accompanying same-flask CO2 concentration measurements. Atmospheric measurements at Drake Passage are representative of zonal average exchange fluxes due to strong mixing by the westerly winds. In preliminary results, anomalously low ∆14C values are correlated with positive states of the Southern Annular Mode, a hemispheric-scale indicator of stronger westerly winds in the high latitude Southern Ocean. Simulations from the TM5 atmospheric transport model with a detailed global radiocarbon budget are used to interpret the results. These results appear to support the hypothesized link between stronger westerly winds and a weaker Southern Ocean carbon sink.

  5. Salt-enhanced chemical weathering of building materials and bacterial mineralization of calcium carbonate as a treatment

    NASA Astrophysics Data System (ADS)

    Schiro, M.; Ruiz-Agudo, E.; Jroundi, F.; Gonzalez-Muñoz, M. T.; Rodriguez-Navarro, C.

    2012-04-01

    Salt weathering is an important mechanism contributing to the degradation and loss of stone building materials. In addition to the physical weathering resulting from crystallization pressure, the presence of salts in solution greatly enhances the chemical weathering potential of pore waters. Flow through experiments quantify the dissolution rates of calcite and quartz grains (63-125 micrometer diameter) when subjected to 1.0 ionic strength solutions of MgSO4, MgCl, Na2SO4 or NaCl. Results indicate that the identity of the cation is the primary control over the dissolution rate of both calcite and quartz substrates, with salt-enhanced dissolution occurring most rapidly in Mg2+ bearing solutions. It has been observed that weathering rates of rocks in nature, as well as building stones, are slowed down by naturally occurring or artificially produced patinas. These tend to be bacterially produced, durable mineralized coatings that lend some degree of protection to the underlying stone surface [1]. Our research shows that bacterially produced carbonate coatings can be quite effective at reducing chemical weathering of stone by soluble salts. The calcite-producing-bacteria used in this study were isolated from stone monuments in Granada, Spain [2] and cultivated in an organic-rich culture medium on a variety of artificial and natural substrates (including limestone, marble, sandstone, quartz, calcite single crystals, glass cover-slips, and sintered porous glass). Scanning electron microscopy (FESEM) was used to image bacterial calcite growth and biofilm formation. In-situ atomic force microscopy (AFM) enabled calculation of dissolution rates of untreated and bacterially treated surfaces. 2D-XRD showed the mineralogy and crystallographic orientation of bacterial calcium carbonate. Results indicate that bacterially produced calcite crystals form a coherent, mechanically resistant surface layer in perfect crystallographic continuity with the calcite substrate (self

  6. Landslide-induced weathering: insight from a deep bedrock tunnel in Taiwan and implications for the carbon cycle

    NASA Astrophysics Data System (ADS)

    Martin, C. E.; Galy, A.; Calmels, D.; Hovius, N.; Bickle, M.; Chen, M.

    2012-12-01

    We present new groundwater chemistry data from inside a 520 m-long, un-cased bedrock tunnel in Taroko Gorge, Taiwan. The tunnel cuts through a ~ 250 m ridge of steeply-dipping meta-sediments (schists and marbles) and exhibits water flow characteristic of deep groundwater and slow surface runoff as defined by Calmels et al. (2011). For comparison, surface runoff from the tunnel face is also presented. In October 2009, catastrophic failure resulted in a landslide, removing ~ 10 m-deep of bedrock from the entire ridge face directly above the tunnel entrance. Groundwater was collected from several drip sites in September 2009 and from the same drip sites in May, June, July and August 2010. The chemistry of the water dripping close to the tunnel entrance disrupted by the landslide implies that the post-landslide groundwater was from a meteoric source with negligible evapotranspiration demonstrating that the geomorphic perturbation allowed for the relatively rapid flushing of underlying bedrock fractures. The drop in [Cl-] of ~ 60 % was associated with a rise in the [SO42-] by a factor of ~ 4 and a positive shift in δ13C of the dissolved inorganic carbon (DIC) of ~ 12 ‰. This could imply that weathering products in the fresh post-landslide groundwater resulted from sulphuric acid weathering associated with a rise in the carbonate-derived DIC. The rise in the [SO42-] suggests that the landslide-induced exposure of fresh mineral surfaces resulted in the relatively rapid oxidation of pyrite, generating sulphuric acid, which then acted as the primary weathering agent. Given that [Ca2+] and [HCO3-] remained constant, secondary carbonate precipitation also took place and the rise in the [Na+] by a factor of >7 associated with a rise in [Mg2+] and [K+] suggest that silicate dissolution had also been enhanced by the oxidation of pyrite. These results imply that landslides provide a mechanism for weathering in the deep critical zone, which in this case constitutes a net output

  7. Carbon isotope records reveal precise timing of enhanced Southern Ocean upwelling during the last deglaciation.

    PubMed

    Siani, Giuseppe; Michel, Elisabeth; De Pol-Holz, Ricardo; Devries, Tim; Lamy, Frank; Carel, Mélanie; Isguder, Gulay; Dewilde, Fabien; Lourantou, Anna

    2013-01-01

    The Southern Ocean plays a prominent role in the Earth's climate and carbon cycle. Changes in the Southern Ocean circulation may have regulated the release of CO₂ to the atmosphere from a deep-ocean reservoir during the last deglaciation. However, the path and exact timing of this deglacial CO₂ release are still under debate. Here we present measurements of deglacial surface reservoir ¹⁴C age changes in the eastern Pacific sector of the Southern Ocean, obtained by ¹⁴C dating of tephra deposited over the marine and terrestrial regions. These results, along with records of foraminifera benthic-planktic ¹⁴C age and δ¹³C difference, provide evidence for three periods of enhanced upwelling in the Southern Ocean during the last deglaciation, supporting the hypothesis that Southern Ocean upwelling contributed to the deglacial rise in atmospheric CO₂. These independently dated marine records suggest synchronous changes in the Southern Ocean circulation and Antarctic climate during the last deglaciation.

  8. One-Dimensional Coupled Ecosystem-Carbon Flux Model for the Simulation of Biogeochemical Parameters at Ocean Weather Station P

    NASA Technical Reports Server (NTRS)

    Signorini, S.; McClain, C.; Christian, J.; Wong, C. S.

    2000-01-01

    In this Technical Publication, we describe the model functionality and analyze its application to the seasonal and interannual variations of phytoplankton, nutrients, pCO2 and CO2 concentrations in the eastern subarctic Pacific at Ocean Weather Station P (OWSP, 50 deg. N 145 deg. W). We use a verified one-dimensional ecosystem model, coupled with newly incorporated carbon flux and carbon chemistry components, to simulate 22 years (1958-1980) of pCO2 and CO2 variability at Ocean Weather Station P (OWS P). This relatively long period of simulation verifies and extends the findings of previous studies using an explicit approach for the biological component and realistic coupling with the carbon flux dynamics. The slow currents and the horizontally homogeneous ocean in the subarctic Pacific make OWS P one of the best available candidates for modeling the chemistry of the upper ocean in one dimension. The chlorophyll and ocean currents composite for 1998 illustrates this premise. The chlorophyll concentration map was derived from SeaWiFS data and the currents are from an OGCM simulation (from R. Murtugudde).

  9. Elemental and organic carbon in aerosols over urbanized coastal region (southern Baltic Sea, Gdynia).

    PubMed

    Lewandowska, Anita; Falkowska, Lucyna; Murawiec, Dominika; Pryputniewicz, Dorota; Burska, Dorota; Bełdowska, Magdalena

    2010-09-15

    Studies on PM 10, total particulate matter (TSP), elemental carbon (EC) and organic carbon (OC) concentrations were carried out in the Polish coastal zone of the Baltic Sea, in urbanized Gdynia. The interaction between the land, the air and the sea was clearly observed. The highest concentrations of PM 10, TSP and both carbon fractions were noted in the air masses moving from southern and western Poland and Europe. The EC was generally of primary origin and its contribution to TSP and PM 10 mass was on average 2.3% and 3.7% respectively. Under low wind speed conditions local sources (traffic and industry) influenced increases in elemental carbon and PM 10 concentrations in Gdynia. Elemental carbon demonstrated a pronounced weekly cycle, yielding minimum values at the weekend and maximum values on Thursdays. The role of harbors and ship yards in creating high EC concentrations was clearly observed. Concentration of organic carbon was ten times higher than that of elemental carbon, and the average OC contribution to PM 10 mass was very high (31.6%). An inverse situation was observed when air masses were transported from over the Atlantic Ocean, the North Sea and the Baltic Sea. These clean air masses were characterized by the lowest concentrations of all analysed compounds. Obtained results for organic and elemental carbon fluxes showed that atmospheric aerosols can be treated, along with water run-off, as a carbon source for the coastal waters of the Baltic Sea. The enrichment of surface water was more effective in the case of organic carbon (0.27+/-0.19 mmol m(-2) d(-1)). Elemental carbon fluxes were one order of magnitude smaller, on average 0.03+/-0.04 mmol m(-2) d(-1). We suggest that in some situations atmospheric carbon input can explain up to 18% of total carbon fluxes into the Baltic coastal waters. Copyright 2010 Elsevier B.V. All rights reserved.

  10. Southern Ocean deep-water carbon export enhanced by natural iron fertilization.

    PubMed

    Pollard, Raymond T; Salter, Ian; Sanders, Richard J; Lucas, Mike I; Moore, C Mark; Mills, Rachel A; Statham, Peter J; Allen, John T; Baker, Alex R; Bakker, Dorothee C E; Charette, Matthew A; Fielding, Sophie; Fones, Gary R; French, Megan; Hickman, Anna E; Holland, Ross J; Hughes, J Alan; Jickells, Timothy D; Lampitt, Richard S; Morris, Paul J; Nédélec, Florence H; Nielsdóttir, Maria; Planquette, Hélène; Popova, Ekaterina E; Poulton, Alex J; Read, Jane F; Seeyave, Sophie; Smith, Tania; Stinchcombe, Mark; Taylor, Sarah; Thomalla, Sandy; Venables, Hugh J; Williamson, Robert; Zubkov, Mike V

    2009-01-29

    The addition of iron to high-nutrient, low-chlorophyll regions induces phytoplankton blooms that take up carbon. Carbon export from the surface layer and, in particular, the ability of the ocean and sediments to sequester carbon for many years remains, however, poorly quantified. Here we report data from the CROZEX experiment in the Southern Ocean, which was conducted to test the hypothesis that the observed north-south gradient in phytoplankton concentrations in the vicinity of the Crozet Islands is induced by natural iron fertilization that results in enhanced organic carbon flux to the deep ocean. We report annual particulate carbon fluxes out of the surface layer, at three kilometres below the ocean surface and to the ocean floor. We find that carbon fluxes from a highly productive, naturally iron-fertilized region of the sub-Antarctic Southern Ocean are two to three times larger than the carbon fluxes from an adjacent high-nutrient, low-chlorophyll area not fertilized by iron. Our findings support the hypothesis that increased iron supply to the glacial sub-Antarctic may have directly enhanced carbon export to the deep ocean. The CROZEX sequestration efficiency (the amount of carbon sequestered below the depth of winter mixing for a given iron supply) of 8,600 mol mol(-1) was 18 times greater than that of a phytoplankton bloom induced artificially by adding iron, but 77 times smaller than that of another bloom initiated, like CROZEX, by a natural supply of iron. Large losses of purposefully added iron can explain the lower efficiency of the induced bloom(6). The discrepancy between the blooms naturally supplied with iron may result in part from an underestimate of horizontal iron supply.

  11. Using U-series Isotopes To Determine Sources Of Pedogenic Carbonates: Comparison Of Natural And Agricultural Soils In The Semi-arid Southern New Mexico And Western Texas

    NASA Astrophysics Data System (ADS)

    Nyachoti, S. K.; Ma, L.; Borrok, D. M.; Jin, L.; Tweedie, C. E.

    2012-12-01

    Pedogenic carbonates commonly precipitate from infiltrating soil water in arid and semi-arid lands and are observed in soils of southern New Mexico and western Texas. These carbonates could form an impermeable layer in the soil horizons impairing water infiltration, thus affecting crop growth and yield. It is important to determine the source of C and Ca in these carbonates and to understand conditions favoring their formation, kinetics and precipitation rates. In this study, major elements and U-series isotopes in bulk calcic soils, and weak acid leachates and residues were measured from one irrigated alfalfa site in the Hueco basin near El Paso, TX and one natural shrubland site on the USDA Jornada experimental range in southern NM. The combined geochemical and isotopic results allow us to determine the formation ages of the carbonates; investigate the mobility of U, Th, and major elements in these soils; and infer for the effects of irrigation on carbonate formation in agricultural soils. Our results show distinctive U and Th isotope systems in the two soil profiles analyzed. For example, (234U/238U) ratios in the Jornada bulk soils decrease from ~1.01 to 0.96 towards the surface, consistent with a preferential loss of 234U over 238U during chemical weathering. At the Jornada site, (238U/232Th) ratios decrease while (230Th/238U) increase towards the surface, consistent with a general depletion of U and the immobility of Th in the natural soils. By contrast at the Alfalfa site, (234U/238U) ratios of bulk soils increase from ~ 0.97 to 1.02 towards the surface, suggesting an additional source of external uranium, most likely the irrigation water from Rio Grande which has a (234U/238U) ratio of ~ 1.5 near El Paso. The (238U/232Th) and (230Th/238U) ratios also imply leaching of U from shallower soils but precipitation in greater depths at Alfalfa site; suggests that partial dissolution and re-precipitation of younger carbonates occur. Calculated carbonate ages from U

  12. Soil carbon stocks and carbon sequestration rates in seminatural grassland in Aso region, Kumamoto, Southern Japan.

    PubMed

    Toma, Yo; Clifton-Brown, John; Sugiyama, Shinji; Nakaboh, Makoto; Hatano, Ryusuke; Fernández, Fabián G; Ryan Stewart, J; Nishiwaki, Aya; Yamada, Toshihiko

    2013-06-01

    Global soil carbon (C) stocks account for approximately three times that found in the atmosphere. In the Aso mountain region of Southern Japan, seminatural grasslands have been maintained by annual harvests and/or burning for more than 1000 years. Quantification of soil C stocks and C sequestration rates in Aso mountain ecosystem is needed to make well-informed, land-use decisions to maximize C sinks while minimizing C emissions. Soil cores were collected from six sites within 200 km(2) (767-937 m asl.) from the surface down to the k-Ah layer established 7300 years ago by a volcanic eruption. The biological sources of the C stored in the Aso mountain ecosystem were investigated by combining C content at a number of sampling depths with age (using (14) C dating) and δ(13) C isotopic fractionation. Quantification of plant phytoliths at several depths was used to make basic reconstructions of past vegetation and was linked with C-sequestration rates. The mean total C stock of all six sites was 232 Mg C ha(-1) (28-417 Mg C ha(-1) ), which equates to a soil C sequestration rate of 32 kg C ha(-1)  yr(-1) over 7300 years. Mean soil C sequestration rates over 34, 50 and 100 years were estimated by an equation regressing soil C sequestration rate against soil C accumulation interval, which was modeled to be 618, 483 and 332 kg C ha(-1)  yr(-1) , respectively. Such data allows for a deeper understanding in how much C could be sequestered in Miscanthus grasslands at different time scales. In Aso, tribe Andropogoneae (especially Miscanthus and Schizoachyrium genera) and tribe Paniceae contributed between 64% and 100% of soil C based on δ(13) C abundance. We conclude that the seminatural, C4 -dominated grassland system serves as an important C sink, and worthy of future conservation. © 2013 Blackwell Publishing Ltd.

  13. The formation of weathering products on the LEW 85320 ordinary chondrite - Evidence from carbon and oxygen stable isotope compositions and implications for carbonates in SNC meteorites

    NASA Technical Reports Server (NTRS)

    Grady, Monica M.; Wright, I. P.; Pillinger, C. T.; Gibson, E. K., Jr.

    1989-01-01

    Isotopic analysis of nesquehonite recovered from the surface of the LEW 85320 H5 ordinary chondrite shows that the delta C-13 and delta O-18 values of the two generations of bicarbonate (Antarctic and Texas) are different: delta C-13 = + 7.9 per mil and + 4.2 per mil; delta O-18 = + 17.9 per mil and + 12.1 per mil, respectively. Carbon isotopic compositions are consistent with equilibrium formation from atmospheric carbon dioxide at - 2 + or - 4 C (Antarctic) and + 16 + or - 4 C (Texas). Oxygen isotopic data imply that the water required for nesquehonite precipitation was derived from atmospheric water vapor or glacial meltwater which had locally exchanged with silicates, either in the meteorite or in underlying bedrock. Although carbonates with similar delta C-13 values have been identified in the SNC meteorites EETA 79001 and Nakhla, petrographic and temperature constraints argue against their simply being terrestrial weathering products.

  14. The formation of weathering products on the LEW 85320 ordinary chondrite - Evidence from carbon and oxygen stable isotope compositions and implications for carbonates in SNC meteorites

    NASA Technical Reports Server (NTRS)

    Grady, Monica M.; Wright, I. P.; Pillinger, C. T.; Gibson, E. K., Jr.

    1989-01-01

    Isotopic analysis of nesquehonite recovered from the surface of the LEW 85320 H5 ordinary chondrite shows that the delta C-13 and delta O-18 values of the two generations of bicarbonate (Antarctic and Texas) are different: delta C-13 = + 7.9 per mil and + 4.2 per mil; delta O-18 = + 17.9 per mil and + 12.1 per mil, respectively. Carbon isotopic compositions are consistent with equilibrium formation from atmospheric carbon dioxide at - 2 + or - 4 C (Antarctic) and + 16 + or - 4 C (Texas). Oxygen isotopic data imply that the water required for nesquehonite precipitation was derived from atmospheric water vapor or glacial meltwater which had locally exchanged with silicates, either in the meteorite or in underlying bedrock. Although carbonates with similar delta C-13 values have been identified in the SNC meteorites EETA 79001 and Nakhla, petrographic and temperature constraints argue against their simply being terrestrial weathering products.

  15. Antarctic black carbon tracks Southern Hemisphere climate throughout the Holocene

    NASA Astrophysics Data System (ADS)

    Arienzo, M. M.; McConnell, J.

    2015-12-01

    Biomass-burning and fossil-fuel combustion emit black carbon (BC) aerosols which impact climate directly by changing Earth's radiation budget and indirectly by changing cloud formation and reducing albedo when deposited on bright surfaces such as snow and ice. BC aerosols have been shown to be the second most important anthropogenic climate-forcing agent today, after carbon dioxide. However, on longer timescales, knowledge of natural variations in BC emissions and climate drivers of regional-scale biomass burning is limited. Here we present the first high-resolution 14,000-year record of BC aerosol deposition in Antarctica. The two ice cores analyzed were the West Antarctic Ice Sheet Divide (WD) core from 14,000 years before 1950 (yr BP) to 2,475 yr BP and the East Antarctic B40 core from 2,485 yr BP to present. BC and a wide range of trace elements were analyzed via a continuous melter system allowing for sub-annual resolution in both cores. For BC concentration determinations, a Single Particle Soot Photometer (SP2; Droplet Measurement Technologies) was used. BC fluxes in the WD and B40 Holocene composite more than doubled from <25 μg m-2 yr-1 at the end of the last glacial termination (14 kyr BP) to >50 μg m-2 yr-1 in the mid-Holocene (~7.5 kyr BP), and then declined to <20 μg m-2 yr-1 in the late Holocene, with lowest BC fluxes observed during the Little Ice Age. We compare Antarctic BC fluxes to low-latitude paleoclimate proxies to investigate a potential link between low latitude climate, biomass burning and BC emissions.

  16. Air-sea carbon dioxide exchange in the Southern Ocean and Antarctic Sea ice zone

    NASA Astrophysics Data System (ADS)

    Butterworth, Brian J.

    The Southern Ocean is an important part of the global carbon cycle, responsible for roughly half of the carbon dioxide (CO2) absorbed by the global ocean. The air-sea CO2 flux (Fc) can be expressed as the product of the water-air CO2 partial pressure difference (DeltapCO2) and the gas transfer velocity ( k), an exchange coefficient which represents the efficiency of gas exchange. Generally, Fc is negative (a sink) throughout the Southern Ocean and Antarctic sea ice zone (SIZ), but uncertainty in k has made it difficult to develop an accurate regional carbon budget. Constraining the functional dependence of k on wind speed in open water environments, and quantifying the effect of sea ice on k, will reduce uncertainty in the estimated contribution of the Southern Ocean and Antarctic SIZ to the global carbon cycle. To investigate Fc in the Southern Ocean, a ruggedized, unattended, closed-path eddy covariance (EC) system was deployed on the Antarctic research vessel Nathaniel B. Palmer for nine cruises during 18 months from January 2013 to June 2014 in the Southern Ocean and coastal Antarctica. The methods are described and results are shown for two cruises chosen for their latitudinal range, inclusion of open water and sea ice cover, and large DeltapCO2. The results indicated that ship-based unattended EC measurements in high latitudes are feasible, and recommendations for deployments in such environments were provided. Measurements of Fc and DeltapCO2 were used to compute k. The open water data showed a quadratic relationship between k (cm hr-1) and the neutral 10-m wind speed (U10n, m s -1), k=0.245 U10n 2+1.3, in close agreement with tracer-based results and much lower than previous EC studies. In the SIZ, it was found that k decreased in proportion to sea ice cover. This contrasted findings of enhanced Fc in the SIZ by previous open-path EC campaigns. Using the NBP results a net annual Southern Ocean (ocean south of 30°S) carbon flux of -1.1 PgC yr-1 was

  17. The Southern Ocean Carbon and Climate Observations and Modeling Program (SOCCOM)

    NASA Astrophysics Data System (ADS)

    Russell, Joellen

    2016-04-01

    SOCCOM is a 6-year observational and modeling research program focused on the role of the Southern Ocean in the anthropogenic carbon budget, ocean biogeochemistry, and climate change. The operational goal of SOCCOM is to deploy nearly 200 Argo-compatible biogeochemically-sensored (BGC) profiling floats equipped with pH, oxygen, nitrate and bio-optical sensors throughout the Southern Ocean waters south of 30°S. These climate-ready BGC-floats are calibrated at the time of deployment by high accuracy biogeochemical measurements, and they operate year around, including in ice-covered waters. The data from the BGC-floats is being assimilated by a Southern Ocean State Estimate (SOSE) model that incorporates biogeochemical processes, and this gridded SOSE output is used to constrain high-resolution coupled atmosphere-ocean model simulations designed to both increase our understanding of Southern Ocean processes and to reduce the uncertainty of projections of the future trajectory of the Earth's carbon, climate and biogeochemistry. We will present an overview of the organization and recent results of SOCCOM as well as the exciting next steps being developed.

  18. Land use change effects on forest carbon cycling throughout the southern United States.

    PubMed

    Woodbury, Peter B; Heath, Linda S; Smith, James E

    2006-01-01

    We modeled the effects of afforestation and deforestation on carbon cycling in forest floor and soil from 1900 to 2050 throughout 13 states in the southern United States. The model uses historical data on gross (two-way) transitions between forest, pasture, plowed agriculture, and urban lands along with equations describing changes in carbon over many decades for each type of land use change. Use of gross rather than net land use transition data is important because afforestation causes a gradual gain in carbon stocks for many decades, while deforestation causes a much more rapid loss in carbon stocks. In the South-Central region (Texas to Kentucky) land use changes caused a net emission of carbon before the 1980s, followed by a net sequestration of carbon subsequently. In the Southeast region (Florida to Virginia), there was net emission of carbon until the 1940s, again followed by net sequestration of carbon. These results could improve greenhouse gas inventories produced to meet reporting requirements under the United Nations Framework Convention on Climate Change. Specifically, from 1990 to 2004 for the entire 13-state study area, afforestation caused sequestration of 88 Tg C, and deforestation caused emission of 49 Tg C. However, the net effect of land use change on carbon stocks in soil and forest floor from 1990 to 2004 was about sixfold smaller than the net change in carbon stocks in trees on all forestland. Thus land use change effects and forest carbon cycling during this period are dominated by changes in tree carbon stocks.

  19. Post-harvest carbon emissions and sequestration in southern United States forest industries

    SciTech Connect

    Row, C.

    1997-12-31

    Whether the forest industries in the southern United States are net emitters or sequesters of carbon from the atmosphere depends on one`s viewpoint. In the short-term, the solid-wood industries-lumber, plywood, and panels--appear to sequester more carbon than is in the fossil fuels they use for processing. The paper industries, however, emit more carbon from fossil fuels than they sequester in the pulp and paper they manufacture. This viewpoint is quite limited. If one considers the life-cycles of solid-wood and paper products from seedlings to landfill, these industries sequester more carbon than they emit from burning fossil fuels. These industries also generate large amounts of energy by replacing fossil fuels with biofuels from processing residues, and wood-based products produce more energy from incineration and landfill gases. Use of the carbon in these biofuels in effect keeps fossil fuel carbon in the ground, considering that at least that amount of carbon would be emitted in producing alternative materials. Another way of looking the emission balances is that wood-based materials, pound for pound or use for use, are the most {open_quotes}carbon efficient{close_quotes} group of major industrial materials. 5 refs., 12 figs.

  20. Soil organic carbon fractionation for improving agricultural soil quality diagnosis in Southern Belgium (Wallonia).

    NASA Astrophysics Data System (ADS)

    Chartin, Caroline; Trigalet, Sylvain; Castaldi, Fabio; Krüger, Inken; Carnol, Monique; van Wesemael, Bas

    2017-04-01

    We propose a simple method for separating bulk Soil Organic Carbon (SOC) into meaningful fractions to better diagnose soil quality, related to soil ecosystem functions and C sequestration potential. Soils under croplands and grasslands, and under both conventional and conservation management practices, have been analyzed all over the Southern part of Belgium (Wallonia). By separating carbon associated with clay and fine silt particles (stable carbon with slow turnover rate, <20 µm) and carbon non-associated with this fraction (labile and intermediate carbon with higher turnover rates, > 20 µm), effects of long-term and medium/short-term managements can be detected more efficiently at different scales. Values of stable carbon fraction for soil under grasslands are analyzed and used to create a theoretical stable carbon saturation curve for assessing carbon sequestration potential of Walloon soils. This theoretical curve is compared to Hassink's (1997) equation. Thus a saturation deficit of cropland soils can be determined and the effect of management practices can be assessed. Besides, spectroscopic analyses are performed on the bulk soil samples to test the potential for accurately estimating total SOC and stable SOC fraction in soil routine analysis performed by Walloon Public Services for local farmers.

  1. Holocene carbon dynamics at the forest-steppe ecotone of southern Siberia.

    PubMed

    Mackay, Anson William; Seddon, Alistair W R; Leng, Melanie J; Heumann, Georg; Morley, David W; Piotrowska, Natalia; Rioual, Patrick; Roberts, Sarah; Swann, George E A

    2017-05-01

    The forest-steppe ecotone in southern Siberia is highly sensitive to climate change; global warming is expected to push the ecotone northwards, at the same time resulting in degradation of the underlying permafrost. To gain a deeper understanding of long-term forest-steppe carbon dynamics, we use a highly resolved, multiproxy, palaeolimnological approach, based on sediment records from Lake Baikal. We reconstruct proxies that are relevant to understanding carbon dynamics including carbon mass accumulation rates (CMAR; g C m(-2)  yr(-1) ) and isotope composition of organic matter (δ(13) CTOC ). Forest-steppe dynamics were reconstructed using pollen, and diatom records provided measures of primary production from near- and off-shore communities. We used a generalized additive model (GAM) to identify significant change points in temporal series, and by applying generalized linear least-squares regression modelling to components of the multiproxy data, we address (1) What factors influence carbon dynamics during early Holocene warming and late Holocene cooling? (2) How did carbon dynamics respond to abrupt sub-Milankovitch scale events? and (3) What is the Holocene carbon storage budget for Lake Baikal. CMAR values range between 2.8 and 12.5 g C m(-2)  yr(-1) . Peak burial rates (and greatest variability) occurred during the early Holocene, associated with melting permafrost and retreating glaciers, while lowest burial rates occurred during the neoglacial. Significant shifts in carbon dynamics at 10.3, 4.1 and 2.8 kyr bp provide compelling evidence for the sensitivity of the region to sub-Milankovitch drivers of climate change. We estimate that 1.03 Pg C was buried in Lake Baikal sediments during the Holocene, almost one-quarter of which was buried during the early Holocene alone. Combined, our results highlight the importance of understanding the close linkages between carbon cycling and hydrological processes, not just temperatures, in southern Siberian

  2. Prolonged acid rain facilitates soil organic carbon accumulation in a mature forest in Southern China.

    PubMed

    Wu, Jianping; Liang, Guohua; Hui, Dafeng; Deng, Qi; Xiong, Xin; Qiu, Qingyan; Liu, Juxiu; Chu, Guowei; Zhou, Guoyi; Zhang, Deqiang

    2016-02-15

    With the continuing increase in anthropogenic activities, acid rain remains a serious environmental threat, especially in the fast developing areas such as southern China. To detect how prolonged deposition of acid rain would influence soil organic carbon accumulation in mature subtropical forests, we conducted a field experiment with simulated acid rain (SAR) treatments in a monsoon evergreen broadleaf forest at Dinghushan National Nature Reserve in southern China. Four levels of SAR treatments were set by irrigating plants with water of different pH values: CK (the control, local lake water, pH ≈ 4.5), T1 (water pH=4.0), T2 (water pH=3.5), and T3 (water pH=3.0). Results showed reduced pH measurements in the topsoil exposed to simulated acid rains due to soil acidification. Soil respiration, soil microbial biomass and litter decomposition rates were significantly decreased by the SAR treatments. As a result, T3 treatment significantly increased the total organic carbon by 24.5% in the topsoil compared to the control. Furthermore, surface soil became more stable as more recalcitrant organic matter was generated under the SAR treatments. Our results suggest that prolonged acid rain exposure may have the potential to facilitate soil organic carbon accumulation in the subtropical forest in southern China. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Linking the variability of atmospheric carbon monoxide to climate modes in the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Buchholz, Rebecca; Monks, Sarah; Hammerling, Dorit; Worden, Helen; Deeter, Merritt; Emmons, Louisa; Edwards, David

    2017-04-01

    Biomass burning is a major driver of atmospheric carbon monoxide (CO) variability in the Southern Hemisphere. The magnitude of emissions, such as CO, from biomass burning is connected to climate through both the availability and dryness of fuel. We investigate the link between CO and climate using satellite measured CO and climate indices. Observations of total column CO from the satellite instrument MOPITT are used to build a record of interannual variability in CO since 2001. Four biomass burning regions in the Southern Hemisphere are explored. Data driven relationships are determined between CO and climate indices for the climate modes: El Niño Southern Oscillation (ENSO); the Indian Ocean Dipole (IOD); the Tropical Southern Atlantic (TSA); and the Southern Annular Mode (SAM). Stepwise forward and backward regression is used to select the best statistical model from combinations of lagged indices. We find evidence for the importance of first-order interaction terms of the climate modes when explaining CO variability. Implications of the model results are discussed for the Maritime Southeast Asia and Australasia regions. We also draw on the chemistry-climate model CAM-chem to explain the source contribution as well as the relative contributions of emissions and meteorology to CO variability.

  4. Interstratified vermiculite-mica in the gneiss-metapelite-serpentinite rocks at Hafafit area, Southern Eastern Desert, Egypt: From metasomatism to weathering

    NASA Astrophysics Data System (ADS)

    Harraz, H. Z.; Hamdy, M. M.

    2010-09-01

    The Hafafit vermiculite in the Southern Eastern Desert of Egypt at the contact of the metapelite and serpentinite rocks with the pegmatites and gneisses of the Hafafit uplift is the only known deposit in the Arabian-Nubian Shield (ANS) rocks of the Eastern Desert (ED). It is distinctively interstratified with mica. The mineralogy and mineral chemistry of this vermiculite at four sites (HV1, HV2, HV3 and HV4) were studied to better understand its origin, which might refers to a specific geologic setting retained to Hafafit area. The vermiculite at Hafafit forms with phlogopite, actinolite-tremolite, asbestos-anthophyllite-talc and talc zones that are arranged from pegmatite and gneisses to the metapelite and serpentinite rocks. These zones were probably formed by metasomatism that related to the intrusion of the granitoid rocks and the connected pegmatites in the upper Pan-African. The XRD and EMPA studies of the interstratified vermiculite-mica concluded that vermiculitization took place through a layer-by-layer transformation of original micas. This formed, in decreasing abundance, mixed-layer phases of biotite/vermiculite (hydrobiotite), phlogopite/vermiculite (hydrophlogopite) and chlorite/vermiculite (corrensite) and discrete phases of vermiculite, chlorite and smectite. A model is suggested, in which chemical weathering by the moving downward meteoric water led to replacement of the interlayer K, in biotite from gneiss and in phlogopite from metasomatic zones, by H 2O molecules, Fe 2+ was oxidized and (OH) - replaced O 2- forming hydrobiotite and hydrophlogopite. By more K remove, Fe was replaced by Mg with the introduction of more layers of H 2O molecules leading to formation of the vermiculite. Weathering formed corrensite mixed-layer and chlorite expandable minerals on the expense of chlorite. Formation of the incomplete smectite-like layers and Al-hydroxy interlayers (13.97 Ǻ) took place at the expense of vermiculite, replacing the Mg interlayer cations

  5. Land cover, more than monthly fire weather, drives fire-size distribution in Southern Québec forests: Implications for fire risk management.

    PubMed

    Marchal, Jean; Cumming, Steve G; McIntire, Eliot J B

    2017-01-01

    Fire activity in North American forests is expected to increase substantially with climate change. This would represent a growing risk to human settlements and industrial infrastructure proximal to forests, and to the forest products industry. We modelled fire size distributions in southern Québec as functions of fire weather and land cover, thus explicitly integrating some of the biotic interactions and feedbacks in a forest-wildfire system. We found that, contrary to expectations, land-cover and not fire weather was the primary driver of fire size in our study region. Fires were highly selective on fuel-type under a wide range of fire weather conditions: specifically, deciduous forest, lakes and to a lesser extent recently burned areas decreased the expected fire size in their vicinity compared to conifer forest. This has large implications for fire risk management in that fuels management could reduce fire risk over the long term. Our results imply, for example, that if 30% of a conifer-dominated landscape were converted to hardwoods, the probability of a given fire, occurring in that landscape under mean fire weather conditions, exceeding 100,000 ha would be reduced by a factor of 21. A similarly marked but slightly smaller effect size would be expected under extreme fire weather conditions. We attribute the decrease in expected fire size that occurs in recently burned areas to fuel availability limitations on fires spread. Because regenerating burned conifer stands often pass through a deciduous stage, this would also act as a negative biotic feedback whereby the occurrence of fires limits the size of nearby future for some period of time. Our parameter estimates imply that changes in vegetation flammability or fuel availability after fires would tend to counteract shifts in the fire size distribution favoring larger fires that are expected under climate warming. Ecological forecasts from models neglecting these feedbacks may markedly overestimate the

  6. Land cover, more than monthly fire weather, drives fire-size distribution in Southern Québec forests: Implications for fire risk management

    PubMed Central

    Marchal, Jean; Cumming, Steve G.; McIntire, Eliot J. B.

    2017-01-01

    Fire activity in North American forests is expected to increase substantially with climate change. This would represent a growing risk to human settlements and industrial infrastructure proximal to forests, and to the forest products industry. We modelled fire size distributions in southern Québec as functions of fire weather and land cover, thus explicitly integrating some of the biotic interactions and feedbacks in a forest-wildfire system. We found that, contrary to expectations, land-cover and not fire weather was the primary driver of fire size in our study region. Fires were highly selective on fuel-type under a wide range of fire weather conditions: specifically, deciduous forest, lakes and to a lesser extent recently burned areas decreased the expected fire size in their vicinity compared to conifer forest. This has large implications for fire risk management in that fuels management could reduce fire risk over the long term. Our results imply, for example, that if 30% of a conifer-dominated landscape were converted to hardwoods, the probability of a given fire, occurring in that landscape under mean fire weather conditions, exceeding 100,000 ha would be reduced by a factor of 21. A similarly marked but slightly smaller effect size would be expected under extreme fire weather conditions. We attribute the decrease in expected fire size that occurs in recently burned areas to fuel availability limitations on fires spread. Because regenerating burned conifer stands often pass through a deciduous stage, this would also act as a negative biotic feedback whereby the occurrence of fires limits the size of nearby future for some period of time. Our parameter estimates imply that changes in vegetation flammability or fuel availability after fires would tend to counteract shifts in the fire size distribution favoring larger fires that are expected under climate warming. Ecological forecasts from models neglecting these feedbacks may markedly overestimate the

  7. Diagnosis of the summertime warm and dry bias over the U. S. Southern Great Plains in the GFDL climate model using a weather forecasting approach

    SciTech Connect

    Klein, S A; Jiang, X; Boyle, J; Malyshev, S; Xie, S

    2006-07-11

    Weather forecasts started from realistic initial conditions are used to diagnose the large warm and dry bias over the United States Southern Great Plains simulated by the GFDL climate model. The forecasts exhibit biases in surface air temperature and precipitation within 3 days which appear to be similar to the climate bias. With the model simulating realistic evaporation but underestimated precipitation, a deficit in soil moisture results which amplifies the initial temperature bias through feedbacks with the land surface. The underestimate of precipitation is associated with an inability of the model to simulate the eastward propagation of convection from the front-range of the Rocky Mountains and is insensitive to an increase of horizontal resolution from 2{sup o} to 0.5{sup o} latitude.

  8. Isotope composition of carbon in the carbonates of the Gumbeykan scheelite deposits in the southern Urals

    SciTech Connect

    Korzhinskii, A.F.; Mamchur, G.P.; Yarynych, O.A.

    1980-10-01

    Through investigations of the isotope composition of carbon of various generations and carbonates from marbles, skarns, and nested and vein scheelite orebodies, the probable source of carbon of these carbonates has been established as a mixture of sedimentary carbonates, carbon dioxide with carbonic acid that was formed by oxidation of the organic matter from sedimentary terrane (..delta..C/sup 13/ - 0.05 to -0.62%). In the calcite and dolomite phenocrysts of marble and the coarse-grained dolostone, containing scheelite, the carbon was lighter (..delta..C/sup 13/ from -0.60 to -0.87%). For the dolomite and ankerite from scheelite pockets of the Balkan deposit and quartz veins of the Buranovo, ..delta..C/sup 13/ varied from -0.44 to -0.87%. The lightest carbon found in strontianite (..delta..C/sup 13/ = -1.32%), located near the coating of the organic matter (..delta..C/sup 13/ = -1.26%) in fractures of the quartz vein of the Buranovo deposit. In the section through the orebodies and near-ore diffusion-metasomatic zones of the Balkan deposit, the lessening of carbon in the carbonates was observed, with increasing distance away from the fracture. ..delta..C/sup 13/ in the altered granitoids ranged from -0.44 to -1.03%; while in the diopside-wollastonite hornfels, from -0.89 to 1.13%. The lessening in weight of the carbon is explained by diffusional fractionation of the isotopes caused apparently by the differential movement of volatile mixtures of carbon during ore-forming processes and the formation of their diffusion-metasomatic zones.

  9. Laboratory Experiments to Evaluate Matrix Diffusion of Dissolved Organic Carbon Carbon-14 in Southern Nevada Fractured-rock Aquifers

    SciTech Connect

    Hershey, Ronald L.; Fereday, Wyatt

    2016-05-01

    Dissolved inorganic carbon (DIC) carbon-14 (14C) is used to estimate groundwater ages by comparing the DIC 14C content in groundwater in the recharge area to the DIC 14C content in the downgradient sampling point. However, because of chemical reactions and physical processes between groundwater and aquifer rocks, the amount of DIC 14C in groundwater can change and result in 14C loss that is not because of radioactive decay. This loss of DIC 14C results in groundwater ages that are older than the actual groundwater ages. Alternatively, dissolved organic carbon (DOC) 14C in groundwater does not react chemically with aquifer rocks, so DOC 14C ages are generally younger than DIC 14C ages. In addition to chemical reactions, 14C ages may also be altered by the physical process of matrix diffusion. The net effect of a continuous loss of 14C to the aquifer matrix by matrix diffusion and then radioactive decay is that groundwater appears to be older than it actually is. Laboratory experiments were conducted to measure matrix diffusion coefficients for DOC 14C in volcanic and carbonate aquifer rocks from southern Nevada. Experiments were conducted using bromide (Br-) as a conservative tracer and 14C-labeled trimesic acid (TMA) as a surrogate for groundwater DOC. Outcrop samples from six volcanic aquifers and five carbonate aquifers in southern Nevada were used. The average DOC 14C matrix diffusion coefficient for volcanic rocks was 2.9 x 10-7 cm2/s, whereas the average for carbonate rocks was approximately the same at 1.7 x 10-7 cm2/s. The average Br- matrix diffusion coefficient for volcanic rocks was 10.4 x 10-7 cm2/s, whereas the average for carbonate rocks was less at 6.5 x 10-7 cm2/s. Carbonate rocks exhibited greater variability in

  10. A total electron content space weather study of the nighttime Weddell Sea Anomaly of 1996/1997 southern summer with TOPEX/Poseidon radar altimetry

    NASA Astrophysics Data System (ADS)

    Horvath, Ildiko

    2006-12-01

    This paper reports on a total electron content space weather study of the nighttime Weddell Sea Anomaly, overlooked by previously published TOPEX/Poseidon climate studies, and of the nighttime ionosphere during the 1996/1997 southern summer. To ascertain the morphology of spatial TEC distribution over the oceans in terms of hourly, geomagnetic, longitudinal and summer-winter variations, the TOPEX TEC, magnetic, and published neutral wind velocity data are utilized. To understand the underlying physical processes, the TEC results are combined with inclination and declination data plus global magnetic field-line maps. To investigate spatial and temporal TEC variations, geographic/magnetic latitudes and local times are computed. As results show, the nighttime Weddell Sea Anomaly is a large (˜1,600(°)2; ˜22 million km2 estimated for a steady ionosphere) space weather feature. Extending between 200°E and 300°E (geographic), it is an ionization enhancement peaking at 50°S-60°S/250°E-270°E and continuing beyond 66°S. It develops where the spacing between the magnetic field lines is wide/medium, easterly declination is large-medium (20°-50°), and inclination is optimum (˜55°S). Its development and hourly variations are closely correlated with wind speed variations. There is a noticeable (˜43%) reduction in its average area during the high magnetic activity period investigated. Southern summer nighttime TECs follow closely the variations of declination and field-line configuration and therefore introduce a longitudinal division of four (Indian, western/eastern Pacific, Atlantic). Northern winter nighttime TECs measured over a limited area are rather uniform longitudinally because of the small declination variation. TOPEX maps depict the expected strong asymmetry in TEC distribution about the magnetic dip equator.

  11. Carbonate mud bodies in middle Mississippian strata of southern Indiana and northern Kentucky: End members of a middle Mississippian mud mound spectrum

    SciTech Connect

    Brown, M.A. ); Dodd, J.R. )

    1990-06-01

    Relatively small, lens-shaped carbonate mud bodies are common features in the Ramp Creek Formation and Harrodsburg Limestone (Mississippian) of southern Indiana and northern Kentucky. The outcrop dimensions of the lenses range from approximately 10 cm thick and 3 m wide to as much as 2 m thick and in excess of 100 m wide; their three-dimensional geometry is unknown. The lens cores consist of dolomitic mudstone that grades laterally and vertically into increasingly more fossiliferous wackestone to grainstone with fenestrate bryozoans and echinoderms being the dominant fossils. The great abundance of fenestrate bryozoan fragments surrounding the lenses suggests that lens evolution was controlled by the trapping of carbonate mud by the baffling action of bryozoans. Wisps of organic material preserved in the lens cores may be remnants of some form of non-calcareous algae that also baffled and trapped carbonate mud. These mud lenses are end members of a spectrum of Mississippian carbonate mud bodies ranging in size from these small lenses to the classical Waulsortian mounds that may be hundreds of meters thick and a kilometer or more broad. All of these carbonate mud bodies may have in part formed by baffling and localizing of carbonate mud by organisms and in part by local production of carbonate mud. The major difference between large and small bodies is the water depth in which each formed. The Ramp Creek-Harrodsburg mud lenses may be miniature Waulsortian mounds that developed at or above fair-weather wave base on a relatively shallow carbonate platform rather than on shelf-to-basin slopes as proposed for the classical Waulsortian mounds.

  12. Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

    PubMed Central

    Taylor, Lyla L.; Banwart, Steve A.; Valdes, Paul J.; Leake, Jonathan R.; Beerling, David J.

    2012-01-01

    Global weathering of calcium and magnesium silicate rocks provides the long-term sink for atmospheric carbon dioxide (CO2) on a timescale of millions of years by causing precipitation of calcium carbonates on the seafloor. Catchment-scale field studies consistently indicate that vegetation increases silicate rock weathering, but incorporating the effects of trees and fungal symbionts into geochemical carbon cycle models has relied upon simple empirical scaling functions. Here, we describe the development and application of a process-based approach to deriving quantitative estimates of weathering by plant roots, associated symbiotic mycorrhizal fungi and climate. Our approach accounts for the influence of terrestrial primary productivity via nutrient uptake on soil chemistry and mineral weathering, driven by simulations using a dynamic global vegetation model coupled to an ocean–atmosphere general circulation model of the Earth's climate. The strategy is successfully validated against observations of weathering in watersheds around the world, indicating that it may have some utility when extrapolated into the past. When applied to a suite of six global simulations from 215 to 50 Ma, we find significantly larger effects over the past 220 Myr relative to the present day. Vegetation and mycorrhizal fungi enhanced climate-driven weathering by a factor of up to 2. Overall, we demonstrate a more realistic process-based treatment of plant fungal–geosphere interactions at the global scale, which constitutes a first step towards developing ‘next-generation’ geochemical models. PMID:22232768

  13. Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach.

    PubMed

    Taylor, Lyla L; Banwart, Steve A; Valdes, Paul J; Leake, Jonathan R; Beerling, David J

    2012-02-19

    Global weathering of calcium and magnesium silicate rocks provides the long-term sink for atmospheric carbon dioxide (CO(2)) on a timescale of millions of years by causing precipitation of calcium carbonates on the seafloor. Catchment-scale field studies consistently indicate that vegetation increases silicate rock weathering, but incorporating the effects of trees and fungal symbionts into geochemical carbon cycle models has relied upon simple empirical scaling functions. Here, we describe the development and application of a process-based approach to deriving quantitative estimates of weathering by plant roots, associated symbiotic mycorrhizal fungi and climate. Our approach accounts for the influence of terrestrial primary productivity via nutrient uptake on soil chemistry and mineral weathering, driven by simulations using a dynamic global vegetation model coupled to an ocean-atmosphere general circulation model of the Earth's climate. The strategy is successfully validated against observations of weathering in watersheds around the world, indicating that it may have some utility when extrapolated into the past. When applied to a suite of six global simulations from 215 to 50 Ma, we find significantly larger effects over the past 220 Myr relative to the present day. Vegetation and mycorrhizal fungi enhanced climate-driven weathering by a factor of up to 2. Overall, we demonstrate a more realistic process-based treatment of plant fungal-geosphere interactions at the global scale, which constitutes a first step towards developing 'next-generation' geochemical models.

  14. Carbon Sequestration and intensive silviculture: The southern U.S. Experience

    NASA Astrophysics Data System (ADS)

    Jose, S.

    2006-05-01

    Carbon sequestration by managed forests in the U.S. accounts for nearly 300 MMTC per year, which is eighteen times more than the C sequestered by croplands and 36 times more than that sequestered by rangelands. The Western forests used to produce majority of the forest biomass (as timber and fiber) in the U.S. However, changing social values and attitudes are shifting harvesting pressure from the western forests to the southeastern forests. As a result of these and other factors, the South's forest biomass production more than doubled between 1953 and 1997. Its share of U.S. production rose from 41 to 58 percent and its share of the world's production from 6.3 to 15.8 percent. This represents a significant gain in the carbon sequestration potential of managed forests in the South. It is estimated that the managed forests of the South sequester nearly 100 MMTC per year or accounts for third of the carbon storage capacity of the continental U.S. forests. The remarkable gain in carbon sequestration potential of the southern forests, despite a shrinking forestland base, was made possible by intensive silviculture. How did intensive silviculture help sequester more carbon? This paper examines the ecological and physiological basis for the observed increases in productivity and carbon sequestration potential of intensively managed forests of the South. It also explores ways by which carbon sequestration can be further enhanced in intensive forestry.

  15. Terrestrial weathering of Antarctic stone meteorites - Formation of Mg-carbonates on ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Velbel, Michael A.; Long, David T.; Gooding, James L.

    1991-01-01

    Results are presented on the mineralogy, chemistry, and origin of white efflorescences on the surface of Lewis Cliff (Antarctica) 85320 (H5) chondrite (LEW 85320). Particular attention is given to determining the sources of the cations and anions of the evaporite, in order to establish the relative importance of the meteoritic element distribution and terrestrial contamination in the evaporite formation during the weathering process. The data on Na, K, Ca, and Rb abundances in efflorescence from LEW 85320 suggest that cations in evaporite minerals on Antarctic meteorites are not the products of contamination by terrestrial (marine) salts. It is suggested that the Mg in efflorescence on LEW 85320 originated from weathering of meteoritic olivine.

  16. In-situ measurement of aerosol organic and elemental carbon, Southern California Air Quality Study. Final report

    SciTech Connect

    Turpin, B.J.; Huntzicker, J.J.

    1989-09-09

    An in situ carbon analyzer measured particulate organic and elemental carbon with two hour time resolution during the Southern California Air Quality Study. Organic and elemental carbon concentrations showed strong diurnal variations. Peak concentrations occurred during the daylight hours in the summer and at night in the fall. The maximum concentrations observed in the fall (maximum total carbon = 88 micrograms carbon per cubic meter) were two to three times higher than the summer maxima (maximum total carbon = 36 micrograms carbon per cubic meter). On several summer days the profiles of organic and elemental carbon were quite similar, and good correlations, comparable to those observed during the fall, were observed between organic and elemental carbon, suggesting that the organic aerosol on those days was principally primary. Comparison of the diurnal profile of organic carbon with those of elemental carbon and ozone provided evidence for considerable secondary formation of organic aerosol during three sampling periods.

  17. Machine learning and linear regression models to predict catchment-level base cation weathering rates across the southern Appalachian Mountain region, USA

    NASA Astrophysics Data System (ADS)

    Povak, Nicholas A.; Hessburg, Paul F.; McDonnell, Todd C.; Reynolds, Keith M.; Sullivan, Timothy J.; Salter, R. Brion; Cosby, Bernard J.

    2014-04-01

    Accurate estimates of soil mineral weathering are required for regional critical load (CL) modeling to identify ecosystems at risk of the deleterious effects from acidification. Within a correlative modeling framework, we used modeled catchment-level base cation weathering (BCw) as the response variable to identify key environmental correlates and predict a continuous map of BCw within the southern Appalachian Mountain region. More than 50 initial candidate predictor variables were submitted to a variety of conventional and machine learning regression models. Predictors included aspects of the underlying geology, soils, geomorphology, climate, topographic context, and acidic deposition rates. Low BCw rates were predicted in catchments with low precipitation, siliceous lithology, low soil clay, nitrogen and organic matter contents, and relatively high levels of canopy cover in mixed deciduous and coniferous forest types. Machine learning approaches, particularly random forest modeling, significantly improved model prediction of catchment-level BCw rates over traditional linear regression, with higher model accuracy and lower error rates. Our results confirmed findings from other studies, but also identified several influential climatic predictor variables, interactions, and nonlinearities among the predictors. Results reported here will be used to support regional sulfur critical loads modeling to identify areas impacted by industrially derived atmospheric S inputs. These methods are readily adapted to other regions where accurate CL estimates are required over broad spatial extents to inform policy and management decisions.

  18. Land-atmosphere carbon cycle research in the southern Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Bowling, D. R.; Blanken, P.; Brooks, P. D.; Ehleringer, J. R.; Ewers, B. E.; Lehman, S.; Litvak, M. E.; Massman, W. J.; Miller, J. B.; Stephens, B. B.; Vaughn, B. H.

    2013-12-01

    The majority of land-atmosphere carbon exchange in the southern U.S. Rocky Mountains (Wyoming, Utah, Colorado, Arizona, and New Mexico) occurs in mid- to high-elevation forests, and in urban metropolitan areas. Forest-atmosphere carbon exchange is highly variable from year to year due to fluctuations in environmental conditions (particularly water availability) and following disturbances by insects and fire. A wide variety of long-term carbon cycle datasets from many locations are freely available to the scientific community from this region, varying in length from a few years to several decades. These include flask observations from the NOAA Cooperative Air Sampling Network (UTA, NWR, NWF, and BAO sites) which include CO2, CO2 stable and radioisotopes, CH4, and CO, continuous CO2 observations from the Rocky RACCOON mountaintop and Salt Lake Valley urban CO2 monitoring sites, forest flux observations from several AmeriFlux towers (GLEES, Niwot Ridge, and Valles Caldera sites), and continuous CO2 isotope observations (Niwot Ridge). Many of these sites include measurements before and after major ecological disturbances. This presentation will describe the publicly available datasets that exist, examining some of the features of these datasets that highlight the regional carbon cycle in the southern Rocky Mountains. Our goal is to encourage use and synthesis of these data by the observational, modeling, and remote sensing communities.

  19. How do the westerlies influence the Southern Ocean subduction of anthropogenic carbon?

    NASA Astrophysics Data System (ADS)

    Downes, Stephanie; Langlais, Clothilde; Brook, Jordan; Spence, Paul

    2017-04-01

    The Southern Ocean is responsible for roughly a third of the global oceanic anthropogenic carbon uptake, and this uptake occurs in the upper ocean Sub-Antarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) layers. The process by which the anthropogenic carbon is transported into the ocean interior is commonly known as 'subduction'. Observationally-based and model studies have shown that the subduction of SAMW and AAIW occurs in hot spots primarily in the deep mixed layer depths in the Indian and Pacific sectors of the Southern Ocean. Two key atmospheric changes in recent decades in the Southern Ocean are increases in atmosphere to ocean buoyancy input, and the poleward intensification of the westerly wind stress band. Both buoyancy and winds are drivers of the Southern Ocean large scale circulation, and in this study we diagnose the impact of specifically the westerly winds on the upper ocean subduction. We evaluate the mean and eddy subduction components under three sensitivity experiments where the westerlies are increased, shifted poleward, and both shifted and increased. We use a 1/4-degree eddy-permitting ocean-ice model coupled to a reanalysis atmosphere. Our perturbation experiments reveal that intensified winds enhance the deep mixed layer depths locally, but a shift in the westerlies decreases (increases) the mixed layer depth in the Indian (southeast Pacific) sector. A poleward intensification of the westerlies combines the individual shift and intensified wind experiment change, as well as strongly enhancing Atlantic mixed layers. The mixed layer changes are associated with SAMW and AAIW subduction, and we find that the poleward intensification of the westerlies overall enhances both the eddy and large scale subduction rates. Using our subduction results and observations, we infer regional anthropogenic carbon inventory changes in a water mass framework under wind stress changes.

  20. Mid-Cretaceous carbon cycle perturbations and Oceanic Anoxic Events recorded in southern Tibet

    PubMed Central

    Zhang, Xiaolin; Chen, Kefan; Hu, Dongping; Sha, Jingeng

    2016-01-01

    The organic carbon isotope (δ13Corg) curve for ~1.7-km-thick mid-Cretaceous strata of the Chaqiela section in Gamba area, southern Tibet is presented in this study. C-isotopic chemostratigraphic correlation combined with biostratigraphic constraints show that the Chaqiela section spans early Aptian through early Campanian period, and that almost all of the carbon cycle perturbations and Oceanic Anoxic Events during the mid-Cretaceous period are well recorded in the continental margin area of the southeastern Tethys Ocean. Significantly, two levels of methane-derived authigenic carbonates were identified at the onset of OAE1b near the Aptian-Albian boundary. We suggest that an increase in methane release from gas hydrates, potentially driven by sea-level fall and bottom water temperature increase, may have contributed to the large negative δ13Corg excursions and global warming during OAE1b. PMID:28000797

  1. Mid-Cretaceous carbon cycle perturbations and Oceanic Anoxic Events recorded in southern Tibet.

    PubMed

    Zhang, Xiaolin; Chen, Kefan; Hu, Dongping; Sha, Jingeng

    2016-12-21

    The organic carbon isotope (δ(13)Corg) curve for ~1.7-km-thick mid-Cretaceous strata of the Chaqiela section in Gamba area, southern Tibet is presented in this study. C-isotopic chemostratigraphic correlation combined with biostratigraphic constraints show that the Chaqiela section spans early Aptian through early Campanian period, and that almost all of the carbon cycle perturbations and Oceanic Anoxic Events during the mid-Cretaceous period are well recorded in the continental margin area of the southeastern Tethys Ocean. Significantly, two levels of methane-derived authigenic carbonates were identified at the onset of OAE1b near the Aptian-Albian boundary. We suggest that an increase in methane release from gas hydrates, potentially driven by sea-level fall and bottom water temperature increase, may have contributed to the large negative δ(13)Corg excursions and global warming during OAE1b.

  2. Mid-Cretaceous carbon cycle perturbations and Oceanic Anoxic Events recorded in southern Tibet

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolin; Chen, Kefan; Hu, Dongping; Sha, Jingeng

    2016-12-01

    The organic carbon isotope (δ13Corg) curve for ~1.7-km-thick mid-Cretaceous strata of the Chaqiela section in Gamba area, southern Tibet is presented in this study. C-isotopic chemostratigraphic correlation combined with biostratigraphic constraints show that the Chaqiela section spans early Aptian through early Campanian period, and that almost all of the carbon cycle perturbations and Oceanic Anoxic Events during the mid-Cretaceous period are well recorded in the continental margin area of the southeastern Tethys Ocean. Significantly, two levels of methane-derived authigenic carbonates were identified at the onset of OAE1b near the Aptian-Albian boundary. We suggest that an increase in methane release from gas hydrates, potentially driven by sea-level fall and bottom water temperature increase, may have contributed to the large negative δ13Corg excursions and global warming during OAE1b.

  3. Bacterial weathering of fossil organic matter and organic carbon mobilization from subterrestrial Kupferschiefer black shale: long-term laboratory studies.

    PubMed

    Stasiuk, Robert; Włodarczyk, Agnieszka; Karcz, Przemysław; Janas, Marcin; Skłodowska, Aleksandra; Matlakowska, Renata

    2017-08-01

    A large part of the organic carbon present in the lithosphere is trapped in fossil organic matter deposited in sedimentary rocks. Only specialized microorganisms are able to degrade it contributing to the return of the carbon to the global cycle. The role of bacteria in this process is not yet completely understood. In the present laboratory studies, subterrestrial organic-rich ∼256-million-year-old Kupferschiefer black shale was exposed to the activity of an indigenous consortium of lithobiontic bacteria for 365 days under aerobic conditions. An interdisciplinary research approach was applied, consisting of a detailed comparison of the chemical composition of extractable bitumens as well as resistant to extraction kerogen of the unweathered black shale to that of the bioweathered and chemically weathered, identification of mobilized organic compounds and spectrometry-based determination of proteomic composition of the bacterial biofilm. The oxidative bioweathering of bitumens and kerogen was confirmed. The mobilization of organic carbon in the form of oxidized organic compounds, such as monohydroxy and dihydroxy alcohols, aldehydes, monocarboxylic and dicarboxylic acids and esters due to the microbial activity, was documented. The enzymes crucial for the aerobic metabolism of aliphatic and aromatic hydrocarbons such as monooxygenases and dehydrogenases were identified in the epilithic biofilm inhabiting the black shale. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  4. Air-sea exchange of carbon dioxide in the Southern Ocean and Antarctic marginal ice zone

    NASA Astrophysics Data System (ADS)

    Butterworth, Brian J.; Miller, Scott D.

    2016-07-01

    Direct carbon dioxide flux measurements using eddy covariance from an icebreaker in the high-latitude Southern Ocean and Antarctic marginal ice zone are reported. Fluxes were combined with the measured water-air carbon dioxide partial pressure difference (ΔpCO2) to compute the air-sea gas transfer velocity (k, normalized to Schmidt number 660). The open water data showed a quadratic relationship between k (cm h-1) and the neutral 10 m wind speed (U10n, m s-1), kopen = 0.245 U10n2 + 1.3, in close agreement with decades old tracer-based results and much lower than cubic relationships inferred from previous open ocean eddy covariance studies. In the marginal ice zone, the effective gas transfer velocity decreased in proportion to sea ice cover, in contrast with predictions of enhanced gas exchange in the presence of sea ice. The combined open water and marginal ice zone results affect the calculated magnitude and spatial distribution of Southern Ocean carbon flux.

  5. Year-round observations of carbon biomass and flux variability in the Southern Ocean

    SciTech Connect

    Bishop, James K.B.; Wood, Todd

    2009-02-01

    Three Carbon Explorer (CE) floats profiling to kilometer depths in the Southern Ocean tracked dawn-dusk variations of mixing/stratification, particulate organic carbon (POC), and light scattering and sedimentation at 100, 250, and 800 m continuously from January 2002 to April 2003. Data were analyzed in conjunction with contemporaneous satellite winds and chlorophyll and derived subsurface light fields. The CE deployed at 66{sup o}S 172{sup o}W operated in the ice edge zone in absence of light. Two CEs deployed at 55{sup o}S 172{sup o}W recorded wintertime mixing to {approx}400 m, yet observed very different bloom dynamics and sedimentation the following spring. Four hypotheses are explored. The strongest is that shallow transient stratification of the deep winter mixed layer to shallower than photosynthetic critical depth occurred more frequently in the non-bloom/higher sedimentation case. The lower particle export to 800 m under the bloom was hypothesized to be due to higher interception of sinking carbon by a relatively starved over wintering zooplankton population. In the Southern Ocean surface phytoplankton biomass may counter indicate particle flux at kilometer depths.

  6. Fluxes of biogenic carbon in the Southern Ocean: roles of large microphagous zooplankton1

    NASA Astrophysics Data System (ADS)

    Le Fèvre, Jacques; Legendre, Louis; Rivkin, Richard B.

    1998-11-01

    The Southern Ocean is an extreme environment, where waters are permanently cold, a seasonal ice cover extends over large areas, and the solar energy available for photosynthesis is severely restricted, either by vertical mixing to considerable depths or, especially south of the Antarctic Circle, by prolonged seasonal periods of low or no irradiance. Such conditions would normally lead to low productivity and a water column dominated by recycling processes involving microbial components of pelagic communities but this does not seem to be the case in the Southern Ocean, where there is efficient export to large apex predators and deep waters. This paper investigates the role of large microphagous zooplankton (salps, krill, and some large copepods) in the partitioning of biogenic carbon among the pools of short- and long-lived organic carbon and sequestered biogenic carbon. Large microphagous zooplankton are able to ingest microbial-sized particles and thus repackage small, non-sinking particles into both metazoan biomass and large, rapidly sinking faeces. Given the wide spatio-temporal extent of microbial trophic pathways in the Southern Ocean, large zooplankton that are omnivorous or able to ingest small food particles have a competitive advantage over herbivorous zooplankton. Krill efficiently transfer carbon to a wide array of apex predators and their faecal pellets are exported to depth during occasional brief sedimentation episodes in spring time. Salps may be a significant link towards some fish (directly) and other apex predators (indirectly) and, at some locations (especially in offshore waters) and time, they may account for most of the downward flux of biogenic carbon. Large copepods are a trophic link towards fish and at least one whale species, and their grazing activity generally impedes the export of organic particles to depth. As a result, biogenic carbon is channelled mainly towards apex predators and episodically into the deep ocean. Without these

  7. Southern Ocean biogeochemical control of glacial/interglacial carbon dioxide change

    NASA Astrophysics Data System (ADS)

    Sigman, D. M.

    2014-12-01

    In the effort to explain the lower atmospheric CO2 concentrations observed during ice ages, two of the first hypotheses involved redistributing dissolved inorganic carbon (DIC) within the ocean. Broecker (1982) proposed a strengthening of the ocean's biological pump during ice ages, which increased the dissolved inorganic carbon gradient between the dark, voluminous ocean interior and the surface ocean's sun-lit, wind-mixed layer. Boyle (1988) proposed a deepening in the ocean interior's pool of DIC associated with organic carbon regeneration, with its concentration maximum shifting from intermediate to abyssal depths. While not irrefutable, evidence has arisen that these mechanisms can explain much of the ice age CO2 reduction and that both were activated by changes in the Southern Ocean. In the Antarctic Zone, reduced exchange of water between the surface and the underlying ocean sequestered more DIC in the ocean interior (the biological pump mechanism). Dust-borne iron fertilization of the Subantarctic surface lowered CO2 partly by the biological pump mechanism and partly by Boyle's carbon deepening. Each mechanism owes a part of its CO2 effect to a transient increase in seafloor calcium carbonate dissolution, which raised the ice age ocean's alkalinity, causing it to absorb more CO2. However, calcium carbonate cycling also sets limits on these mechanisms and their CO2 effects, such that the combination of Antarctic and Subantarctic changes is needed to achieve the full (80-100 ppm) ice age CO2 decline. Data suggest that these changes began at different phases in the development of the last ice age, 110 and 70 ka, respectively, explaining a 40 ppm CO2 drop at each time. We lack a robust understanding of the potential causes for both the implied reduction in Antarctic surface/deep exchange and the increase in Subantarctic dust supply during ice ages. Thus, even if the evidence for these Southern Ocean changes were to become incontrovertible, conceptual gaps stand

  8. Estimates of Southern Ocean primary production—constraints from predator carbon demand and nutrient drawdown

    NASA Astrophysics Data System (ADS)

    Priddle, J.; Boyd, I. L.; Whitehouse, M. J.; Murphy, E. J.; Croxall, J. P.

    1998-11-01

    In view of the wide range of estimates for the total primary production for the Southern Ocean south of the Subantarctic Front—current estimates range from 1.2 to 3.5 Gtonne C year -1—we have examined two indirect methods for assessing primary production. First, we have estimated the primary production needed to sustain the carbon requirements of the endotherm top predators in the ecosystem. Estimation of the carbon requirements for crabeater seals of about 7 Mtonne C year -1 is extrapolated to a value for all endotherm predators of 15-30 Mtonne C year -1. Current data indicate that 70-80% of the diet of this suite of predators is zooplankton (predominantly the euphausiid krill), making for highly efficient transfer from primary production to top predators. Our best estimate of Southern Ocean primary production by this method is of the order of 1.7 Gtonne C year -1, or an averaged areal primary production of about 30-40 g C m -2 year -1. Our second approach is to estimate primary production from the drawdown of inorganic nutrients, based on the limited suite of studies from which an annual nutrient deficit can be calculated. Again, this indicates annual primary production of the order of 1.5 Gtonne. Although both methods have inherent uncertainties, taken together they provide a relatively robust constraint on annual primary production. For both methods to underestimate primary production by the 1-1.5 Gtonne C implied by the higher current estimates, carbon export from the Southern Ocean pelagic ecosystem would need to be much higher than is normally found in other oceans.

  9. Severe summer heatwave and drought strongly reduced carbon uptake in Southern China

    DOE PAGES

    Yuan, Wenping; Cai, Wenwen; Chen, Yang; ...

    2016-01-07

    Increasing heatwave and drought events can potentially alter the carbon cycle. Few studies have investigated the impacts of hundred-year return heatwaves and droughts, as those events are rare. In the summer of 2013, southern China experienced its strongest drought and heatwave on record for the past 113 years. We show that the record-breaking heatwave and drought lasted two months (from July to August), significantly reduced the satellite-based vegetation index and gross primary production, substantially altered the regional carbon cycle, and produced the largest negative crop yield anomaly since 1960. The event resulted in a net reduction of 101.54 Tg Cmore » in carbon sequestration in the region during these two months, which was 39–53% of the annual net carbon sink of China’s terrestrial ecosystems (190–260 Tg C yr-1). Moreover, model experiments showed that heatwaves and droughts consistently decreased ecosystem vegetation primary production but had opposite impacts on ecosystem respiration (TER), with increased TER by 6.78 ± 2.15% and decreased TER by 15.34 ± 3.57% assuming only changed temperature and precipitation, respectively. As a result, in light of increasing frequency and severity of future heatwaves and droughts, our study highlights the importance of accounting for the impacts of heatwaves and droughts in assessing the carbon sequestration in terrestrial ecosystems.« less

  10. Competition between ocean carbon pumps in simulations with varying Southern Hemisphere westerly wind forcing

    NASA Astrophysics Data System (ADS)

    Huiskamp, W. N.; Meissner, K. J.; d'Orgeville, M.

    2016-06-01

    We analyse the impact of migration and strength of Southern Hemisphere westerly winds on the ocean carbon cycle in a systematic sensitivity study with the University of Victoria Earth System Climate Model. We find that changes in the biological pump are mainly driven by changes in ocean residence times while changes in export production are negligible. Changes in the biological and physical pumps are always of opposite sign; with the physical pump being dominant for southward shifts and the biological pump being dominant for northward shifts. Furthermore, changes in the Pacific Ocean carbon budget dictate the overall changes in global marine and atmospheric carbon. Overall, atmospheric hbox {CO}_2 increases (and Δ ^{14}hbox {C} decreases) for northward shifts or a strengthening in wind forcing. The opposite is true for a southward shift or a weakening in wind forcing. Combining forcings (shift and intensity change) results in a combination of their impacts with the direction of the shift being the first order forcing. The terrestrial carbon reservoir absorbs (releases) 50-70 % of the net oceanic carbon loss (increase), counterbalancing the effect on atmospheric hbox {CO}_2.

  11. Severe summer heatwave and drought strongly reduced carbon uptake in Southern China

    PubMed Central

    Yuan, Wenping; Cai, Wenwen; Chen, Yang; Liu, Shuguang; Dong, Wenjie; Zhang, Haicheng; Yu, Guirui; Chen, Zhuoqi; He, Honglin; Guo, Weidong; Liu, Dan; Liu, Shaoming; Xiang, Wenhua; Xie, Zhenghui; Zhao, Zhonghui; Zhou, Guomo

    2016-01-01

    Increasing heatwave and drought events can potentially alter the carbon cycle. Few studies have investigated the impacts of hundred-year return heatwaves and droughts, as those events are rare. In the summer of 2013, southern China experienced its strongest drought and heatwave on record for the past 113 years. We show that the record-breaking heatwave and drought lasted two months (from July to August), significantly reduced the satellite-based vegetation index and gross primary production, substantially altered the regional carbon cycle, and produced the largest negative crop yield anomaly since 1960. The event resulted in a net reduction of 101.54 Tg C in carbon sequestration in the region during these two months, which was 39–53% of the annual net carbon sink of China’s terrestrial ecosystems (190–260 Tg C yr−1). Moreover, model experiments showed that heatwaves and droughts consistently decreased ecosystem vegetation primary production but had opposite impacts on ecosystem respiration (TER), with increased TER by 6.78 ± 2.15% and decreased TER by 15.34 ± 3.57% assuming only changed temperature and precipitation, respectively. In light of increasing frequency and severity of future heatwaves and droughts, our study highlights the importance of accounting for the impacts of heatwaves and droughts in assessing the carbon sequestration in terrestrial ecosystems. PMID:26739761

  12. Severe summer heatwave and drought strongly reduced carbon uptake in Southern China.

    PubMed

    Yuan, Wenping; Cai, Wenwen; Chen, Yang; Liu, Shuguang; Dong, Wenjie; Zhang, Haicheng; Yu, Guirui; Chen, Zhuoqi; He, Honglin; Guo, Weidong; Liu, Dan; Liu, Shaoming; Xiang, Wenhua; Xie, Zhenghui; Zhao, Zhonghui; Zhou, Guomo

    2016-01-07

    Increasing heatwave and drought events can potentially alter the carbon cycle. Few studies have investigated the impacts of hundred-year return heatwaves and droughts, as those events are rare. In the summer of 2013, southern China experienced its strongest drought and heatwave on record for the past 113 years. We show that the record-breaking heatwave and drought lasted two months (from July to August), significantly reduced the satellite-based vegetation index and gross primary production, substantially altered the regional carbon cycle, and produced the largest negative crop yield anomaly since 1960. The event resulted in a net reduction of 101.54 Tg C in carbon sequestration in the region during these two months, which was 39-53% of the annual net carbon sink of China's terrestrial ecosystems (190-260 Tg C yr(-1)). Moreover, model experiments showed that heatwaves and droughts consistently decreased ecosystem vegetation primary production but had opposite impacts on ecosystem respiration (TER), with increased TER by 6.78 ± 2.15% and decreased TER by 15.34 ± 3.57% assuming only changed temperature and precipitation, respectively. In light of increasing frequency and severity of future heatwaves and droughts, our study highlights the importance of accounting for the impacts of heatwaves and droughts in assessing the carbon sequestration in terrestrial ecosystems.

  13. Severe summer heatwave and drought strongly reduced carbon uptake in Southern China

    SciTech Connect

    Yuan, Wenping; Cai, Wenwen; Chen, Yang; Liu, Shuguang; Dong, Wenjie; Zhang, Haicheng; Yu, Guirui; Chen, Zhuoqi; He, Honglin; Guo, Weidong; Liu, Dan; Liu, Shaoming; Xiang, Wenhua; Xie, Zhenghui; Zhao, Zhonghui; Zhou, Guomo

    2016-01-07

    Increasing heatwave and drought events can potentially alter the carbon cycle. Few studies have investigated the impacts of hundred-year return heatwaves and droughts, as those events are rare. In the summer of 2013, southern China experienced its strongest drought and heatwave on record for the past 113 years. We show that the record-breaking heatwave and drought lasted two months (from July to August), significantly reduced the satellite-based vegetation index and gross primary production, substantially altered the regional carbon cycle, and produced the largest negative crop yield anomaly since 1960. The event resulted in a net reduction of 101.54 Tg C in carbon sequestration in the region during these two months, which was 39–53% of the annual net carbon sink of China’s terrestrial ecosystems (190–260 Tg C yr-1). Moreover, model experiments showed that heatwaves and droughts consistently decreased ecosystem vegetation primary production but had opposite impacts on ecosystem respiration (TER), with increased TER by 6.78 ± 2.15% and decreased TER by 15.34 ± 3.57% assuming only changed temperature and precipitation, respectively. As a result, in light of increasing frequency and severity of future heatwaves and droughts, our study highlights the importance of accounting for the impacts of heatwaves and droughts in assessing the carbon sequestration in terrestrial ecosystems.

  14. Chemically Accelerated Carbon Mineralization: Chemical and Biological Catalytic Enhancement of Weathering of Silicate Minerals as Novel Carbon Capture and Storage

    SciTech Connect

    2010-07-01

    IMPACCT Project: Columbia University is developing a process to pull CO2 out of the exhaust gas of coal-fired power plants and turn it into a solid that can be easily and safely transported, stored above ground, or integrated into value-added products (e.g. paper filler, plastic filler, construction materials, etc.). In nature, the reaction of CO2 with various minerals over long periods of time will yield a solid carbonate—this process is known as carbon mineralization. The use of carbon mineralization as a CO2 capture and storage method is limited by the speeds at which these minerals can be dissolved and CO2 can be hydrated. To facilitate this, Columbia University is using a unique process and a combination of chemical catalysts which increase the mineral dissolution rate, and the enzymatic catalyst carbonic anhydrase which speeds up the hydration of CO2.

  15. Assessing the Role of Seafloor Weathering in Global Geochemical Cycling

    NASA Astrophysics Data System (ADS)

    Farahat, N. X.; Abbot, D. S.; Archer, D. E.

    2015-12-01

    Low-temperature alteration of the basaltic upper oceanic crust, known as seafloor weathering, has been proposed as a mechanism for long-term climate regulation similar to the continental climate-weathering negative feedback. Despite this potentially far-reaching impact of seafloor weathering on habitable planet evolution, existing modeling frameworks do not include the full scope of alteration reactions or recent findings of convective flow dynamics. We present a coupled fluid dynamic and geochemical numerical model of low-temperature, off-axis hydrothermal activity. This model is designed to explore the the seafloor weathering flux of carbon to the oceanic crust and its responsiveness to climate fluctuations. The model's ability to reproduce the seafloor weathering environment is evaluated by constructing numerical simulations for comparison with two low-temperature hydrothermal systems: A transect east of the Juan de Fuca Ridge and the southern Costa Rica Rift flank. We explore the sensitivity of carbon uptake by seafloor weathering on climate and geology by varying deep ocean temperature, seawater dissolved inorganic carbon, continental weathering inputs, and basaltic host rock in a suite of numerical experiments.

  16. Temporal changes in ventilation and the carbonate system in the Atlantic sector of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Tanhua, Toste; Hoppema, Mario; Jones, Elizabeth M.; Stöven, Tim; Hauck, Judith; Dávila, Melchor González; Santana-Casiano, Magdalena; Álvarez, Marta; Strass, Volker H.

    2017-04-01

    The Southern Ocean is the most important area of anthropogenic carbon (Cant) uptake in the world ocean, only rivalled in importance by the North Atlantic Ocean. Significant variability on decadal time-scales in the uptake of Cant in the Southern Ocean has been observed and modelled, likely with consequences for the interior ocean storage of Cant in the region, and implications for the global carbon budget. Here we use eight cruises between 1973 and 2012 to assess decadal variability in Cant storage rates in the southeast Atlantic sector of the Southern Ocean. For this we employed the extended multiple linear regression (eMLR) method. We relate variability in DIC (dissolved inorganic carbon) storage, which is assumed to equal anthropogenic carbon storage, to changes in ventilation as observed from repeat measurements of transient tracers. Within the Antarctic Intermediate Water (AAIW) layer, which is the dominant transport conduit for Cant into the interior ocean, moderate Cant storage rates were found without any clear temporal trend. In Subantarctic Mode Water (SAMW), a less dense water mass found north of the Subantarctic Front and above AAIW, high storage rates of Cant were observed up to about 2005 but lower rates in more recent times. The transient tracer data suggest a significant speed-up of ventilation in the summer warmed upper part of AAIW between 1998 and 2012, which is consistent with the high storage rate of Cant. A shift of more northern Cant storage to more southern storage in near surface waters was detected in the early 2000s. Beneath the AAIW the eMLR method as applied here did not detect significant storage of Cant. However, the presence of the transient tracer CFC-12 all through the water column suggests that some Cant should be present, but at concentrations not reliably quantifiable. The observed temporal variability in the interior ocean seems at a first glance to be out of phase with observed surface ocean Cant fluxes, but this can be

  17. Regional Carbon Fluxes and Atmospheric Carbon Dynamics in the Southern Great Plains during the 2007 CLASIC intensive

    NASA Astrophysics Data System (ADS)

    Biraud, S. C.; Torn, M. S.; Riley, W. J.; Fischer, M. L.; Billesbach, D. P.; Avissar, R.; Berry, J. A.; Hirsch, A.; Loewenstein, M.; Lopez, J.

    2007-12-01

    In June 2007, a regional campaign took place in the Southern Great Plains (SGP) to estimate land-atmosphere exchanges of CO2, water, and energy at 1 to 100 km scales. The primary goals of this campaign were to evaluate top-down and bottom-up estimates of regional fluxes and to understand the influence of moisture gradients, surface heterogeneity, and atmospheric transport patterns on these fluxes (and their estimation). The work was integrated with the Cloud and Land Surface Interaction Campaign (CLASIC), centered on the US DOE Atmospheric Radiation Measurement (ARM) Program SGP region. CO2 concentration data were collected from tower and airborne platforms. Eddy flux towers were deployed in the four major land cover types, distributed over the region's SE to NW precipitation gradient. In addition, CO2, water, and energy fluxes were observed with the Duke Helicopter Observation Platform (HOP) at various heights in the boundary layer, including in the surface layer (the few meters near the surface). One aircraft carried precise CO2, CO, and CH4 continuous measurement systems, and 14C, radon, and NOAA 12-flask (carbon cycle gases and isotopes) packages. Continuous CO2, CO, and radon concentrations, NOAA 2-flask package, and isotope diel flasks (14C, 13C, and 18O) were also collected from a centrally located 60 m tower. Flights were planned to constrain simple boundary layer budget models and to conduct Lagrangian air mass following experiments. We present these data in the context of characterizing surface carbon exchanges via bottom-up and top-down approaches. We also describe results from forward (using MM5-LSM) and inverse (using STILT) modeling to estimate regional surface carbon and energy fluxes. In addition to characterizing the influence of the land surface on the atmosphere, the aircraft data (in combination with observations of atmospheric dynamics) provides a very well characterized southern boundary condition to the NACP Mid-Continent Intensive.

  18. Characterization of a Miocene carbonate reservoir analog in Southern Mallorca (Balearic Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Vandeginste, V.; Camoin, G.; Eisenhauer, A.; Pézard, P.; Lapointe, P.

    2009-04-01

    Carbonate reservoirs contain more than half the world's oil reserves, including highly productive reservoirs in Cretaceous and Cenozoic carbonates from the Middle East and Southeastern Asia. They are usually characterized by the complexity both of their internal architecture and of the distribution of their diagenetic fabrics which hampers crosshole correlations at various scales, and predictions regarding flow paths and volumes of fluids. Reservoir analogs can have the advantage of easier accessibility and sampling and less severe diagenetic alteration. Their study often provides information complementary to the knowledge of hydrocarbon reservoirs and it leads to a better understanding of carbonate systems, important to make better predictions on other potential reservoirs. Significant advances can be made from joint research in natural laboratories integrating outcrops and shallow boreholes, with extensive control on geophysical, geological and petrophysical parameters. The southern part of the island of Mallorca appears as a natural laboratory where a direct comparison between outcrop and shallow subsurface datasets is the objective of the current study. This region is characterized both by spectacular outcrops, especially in the Cabo Blanco area, which were previously studied [e.g. 1], and by shallow holes, 100 m deep on average, that have been drilled especially at Can Roses, Ses Pastores and Ses Sitjoles, from west to east. This geographical extension of the study area provides the opportunity to better explore and understand the Miocene carbonate complex which comprises the Llucmajor platform. This study incorporates a wide range of analytical techniques to characterize the reservoir aspects, such as conventional microscopy of thin sections, XRD analysis, isotopic carbon and oxygen analysis, isotopic strontium dating analysis, petrophysical measurements, high-resolution borehole images and CT scan data. These techniques are used to unravel the sedimentology

  19. Planetary surface weathering

    NASA Technical Reports Server (NTRS)

    Gooding, J. L.

    1986-01-01

    The weathering of planetary surfaces is treated. Both physical and chemical weathering (reactions between minerals or mineraloids and planetary volatiles through oxidation, hydration, carbonation, or solution processes) are discussed. Venus, earth, and Mars all possess permanent atmospheres such that weathering should be expected to significantly affect their respective surfaces. In contrast, Mercury and the moon lack permanent atmospheres but conceivably could experience surface weathering in response to transient atmospheres generated by volcanic or impact cratering events. Weathering processes can be postulated for other rocky objects including Io, Titan, asteroids, and comets.

  20. Comparison of CO2 capture by ex-situ accelerated carbonation and in in-situ naturally weathered coal fly ash.

    PubMed

    Muriithi, Grace N; Petrik, Leslie F; Fatoba, Olanrewaju; Gitari, Wilson M; Doucet, Frédéric J; Nel, Jaco; Nyale, Sammy M; Chuks, Paul E

    2013-09-30

    Natural weathering at coal power plants ash dams occurs via processes such as carbonation, dissolution, co-precipitation and fluid transport mechanisms which are responsible for the long-term chemical, physical and geochemical changes in the ash. Very little information is available on the natural carbon capture potential of wet or dry ash dams. This study investigated the extent of carbon capture in a wet-dumped ash dam and the mineralogical changes promoting CO2 capture, comparing this natural phenomenon with accelerated ex-situ mineral carbonation of fresh fly ash (FA). Significant levels of trace elements of Sr, Ba and Zr were present in both fresh and weathered ash. However Nb, Y, Sr, Th and Ba were found to be enriched in weathered ash compared to fresh ash. Mineralogically, fresh ash is made up of quartz, mullite, hematite, magnetite and lime while weathered and carbonated ashes contained additional phases such as calcite and aragonite. Up to 6.5 wt % CO2 was captured by the fresh FA with a 60% conversion of calcium to CaCO3 via accelerated carbonation (carried out at 2 h, 4Mpa, 90 °C, bulk ash and a S/L ratio of 1). On the other hand 6.8 wt % CO2 was found to have been captured by natural carbonation over a period of 20 years of wet disposed ash. Thus natural carbonation in the ash dumps is significant and may be effective in capturing CO2. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. The Influence of Weather Anomalies on Mercury Cycling in the Marine Coastal Zone of the Southern Baltic-Future Perspective.

    PubMed

    Bełdowska, Magdalena

    2015-01-01

    Despite the decreased emission loads of mercury, historical deposits of this metal in various compartments of the environment may become an additional diffuse source in the future. Global climate change manifests itself in the temperate zone in several ways: warmer winters, shorter icing periods, increased precipitation and heightened frequency of extreme events such as strong gales and floods, all of which cause disturbances in the rate and direction of mercury biogeochemical cycling. The present study was conducted at two sites, Oslonino and Gdynia Orlowo (both in the coastal zone of the Gulf of Gdansk), from which samples were collected once a month between January 2012 and December 2012. In the Southern Baltic region, climate changes can certainly enhance coast to basin fluxes of mercury and the transfer of bioavailable forms of this metal to the food web. They may also, in the future, contribute to uncontrollable increases of mercury in the seawater.

  2. Carbonate tidal flat in mixed carbonate-siliciclastic clore formation (upper chesterian) in Southern Illinois

    SciTech Connect

    Abegg, F.E.

    1988-01-01

    The upper Chesterian Clore Formation consists primarily of delta-front sandstones of the Tygett Sandstone Member and interbedded offshore mud-rich carbonates and prodelta shales of the Cora and Ford Station Limestone Members. The basal Ford Station limestone in south-central Illinois contains a carbonate sequence 1.0 m thick marked by (1) laminated pelletal lime mudstones, (2) bird's-eye structures containing internal sediment, (3) vertical burrows, (4) horizontal shrinkage cracks, (5) autoclastic brecciation, (6) root. tubes, and (7) calciphers. These features indicate tidal-flat deposition. Other examples of peritidal carbonate deposition are unknown in the Chesterian of the Illinois basin. Tidal-flat strata overlie 1.9 m of interbedded shale and lime mudstones containing linguloid brachiopods, pectin bivalves, and ostracods. The lime mudstones and shales are interpreted as shallow-subtidal, restricted-shelf deposits overlying crevasse-splay deposits of the upper Tygett sandstone. Carbonate tidal-flat deposition in the upper Chesterian of the Illinois basin is an exception to the generally accepted model of nearshore terrigenous and offshore carbonate sedimentation. Delta switching is the most plausible explanation for development of the Clore tidal flat. Following deposition of the deltaic Tygett sandstone, peritidal carbonate deposition occurred in the basal Ford Station limestone when terrigenous sedimentation was deflected westward, as indicated by thin delta-front sandstones in the basal Ford Station limestone in southwestern Illinois. The tidal flat developed locally because south-central Illinois was the region of maximum progradation of the Tygett delta and because upper Tygett crevasse-splay deposits compacted less than adjacent shales.

  3. NanoRelease: Pilot interlaboratory comparison of a weathering protocol applied to resilient and labile polymers with and without embedded carbon nanotubes

    EPA Science Inventory

    A major use of multi-walled carbon nanotubes (MWCNTs) is as functional fillers embedded in a solid matrix, such as plastics or coatings. Weathering and abrasion of the solid matrix during use can lead to environmental releases of the MWCNTs. Here we focus on a protocol to identif...

  4. NanoRelease: Pilot interlaboratory comparison of a weathering protocol applied to resilient and labile polymers with and without embedded carbon nanotubes

    EPA Science Inventory

    A major use of multi-walled carbon nanotubes (MWCNTs) is as functional fillers embedded in a solid matrix, such as plastics or coatings. Weathering and abrasion of the solid matrix during use can lead to environmental releases of the MWCNTs. Here we focus on a protocol to identif...

  5. Basalt Weathering, Nutrient Uptake, And Carbon Release By An Exotic And A Native Arizona Grass Species Under Different Temperature Conditions

    NASA Astrophysics Data System (ADS)

    Gallas, G.; Dontsova, K.; Chorover, J.; Hunt, E.; Ravi, S.

    2010-12-01

    During this past summer, the National Science Foundation funded a 10-week Research Experience for Undergraduates (REU) program “Environmental and Earth Systems Research at Biosphere 2”. This program provides undergraduates with an opportunity to conduct guided research in environmental and Earth systems science and has resulted in this work. Biosphere 2 allows for the exploration of complex questions in Earth sciences because of its large scale and the precise control allowed over many experimental elements. The goal of this study was to observe plant-mediated weathering of granular basalt under two temperature conditions. Two grass species were studied, one native to Arizona: Tanglehead, Heteropogan contortus, and one exotic to Arizona: Buffelgrass, Pennisetum ciliar. The grasses were grown in pots located in the Desert and the Savannah Biomes in the Biosphere 2 to take advantage of a 4° C temperature difference. Understanding differences in how native and invasive grasses weather soil and take up nutrients may explain the mechanism behind current invasion of Sonoran Desert by exotic species and help predict response of native and invasive vegetation to expected increase in temperatures. Each biome also contained three replicate “control” pots without vegetation, and mixtures of the two grass species to observe possible competition between the species. Three factors were compared in this study: 1. Temperature: the same species of grass under two different temperature conditions 2. Species: Native Arizonan species vs. a species exotic to Arizona 3. Temporal: How the grasses use resources differently as they grow Leachate samples were collected and analyzed for pH, electrical conductivity, total organic carbon, total nitrogen, inorganic carbon by high temperature combustion coupled with infrared gas analysis; F-, Cl-, Br-, NO3-, NO2-, SO42-, and PO43- by ion chromatography; and cations and metals by ICP-MS. The data trends indicate that plants enhanced

  6. Water quality assessment of carbonate aquifers in southern Latium region, Central Italy: a case study for irrigation and drinking purposes

    NASA Astrophysics Data System (ADS)

    Sappa, Giuseppe; Ergul, Sibel; Ferranti, Flavia

    2014-06-01

    In southern Latium region, Central Italy, groundwater and spring water resources in the carbonate aquifers are the major contributors of drinking and irrigation water supply. The aim of this study was to review hydrochemical processes that control the groundwater chemistry and to determine the suitability of springs and groundwater for irrigation and drinking purposes on the basis of the water quality indices. Physical (pH, electrical conductivity, total dissolved solids) and hydrochemical characteristics (Na+, K+, Ca2+, Mg2+, HCO3 -, Cl-, and SO4 -) of springs and groundwater were determined. To assess the water quality, chemical parameters like sodium adsorption ratio (SAR), total hardness, Mg-hazard (MH), sodium percentage (Na %), salinity hazard, permeability index, and Kelly's ratio were calculated based on the analytical results. A Durov diagram plot revealed that the groundwater has been evolved from Ca to HCO3 recharge water, followed by mixing and reverse ion exchange processes, due to the respective dominance of Na-Cl and Ca-Cl water types. According to Gibbs's diagram plots, chemical weathering of rock forming minerals is the major driving force controlling water chemistry in this area. Groundwater and spring samples were grouped into six categories according to irrigation water quality assessment diagram of US Salinity Laboratory classification and most of the water samples distributed in category C2-S1 and C3-S1 highlighting medium to high salinity hazard and low sodium content class. The results of hydrochemical analyses and the calculated water quality parameters suggest that most of the water samples are suitable for irrigation and drinking purposes, except for the samples influenced by seawater and enhanced water-rock interaction. High values of salinity, Na %, SAR, and MH at certain sites, restrict the suitability for agricultural uses.

  7. The anthropogenic contribution to atmospheric black carbon concentrations in southern Africa: a WRF-Chem modeling study

    NASA Astrophysics Data System (ADS)

    Kuik, F.; Lauer, A.; Beukes, J. P.; Van Zyl, P. G.; Josipovic, M.; Vakkari, V.; Laakso, L.; Feig, G. T.

    2015-08-01

    South Africa has one of the largest industrialized economies in Africa. Emissions of air pollutants are particularly high in the Johannesburg-Pretoria metropolitan area, the Mpumalanga Highveld and the Vaal Triangle, resulting in local air pollution. This study presents and evaluates a setup for conducting modeling experiments over southern Africa with the Weather Research and Forecasting model including chemistry and aerosols (WRF-Chem), and analyzes the contribution of anthropogenic emissions to the total black carbon (BC) concentrations from September to December 2010. The modeled BC concentrations are compared with measurements obtained at the Welgegund station situated ca. 100 km southwest of Johannesburg. An evaluation of WRF-Chem with observational data from ground-based measurement stations, radiosondes, and satellites shows that the meteorology is modeled mostly reasonably well, but precipitation amounts are widely overestimated and the onset of the wet season is modeled approximately 1 month too early in 2010. Modeled daily mean BC concentrations show a temporal correlation of 0.66 with measurements, but the total BC concentration is underestimated in the model by up to 50 %. Sensitivity studies with anthropogenic emissions of BC and co-emitted species turned off show that anthropogenic sources can contribute up to 100 % to BC concentrations in the industrialized and urban areas, and anthropogenic BC and co-emitted species together can contribute up to 60 % to PM1 levels. Particularly the co-emitted species contribute significantly to the aerosol optical depth (AOD). Furthermore, in areas of large-scale biomass-burning atmospheric heating rates are increased through absorption by BC up to an altitude of about 600hPa.

  8. Fire activity as a function of fire–weather seasonal severity and antecedent climate across spatial scales in southern Europe and Pacific western USA

    USGS Publications Warehouse

    Urbieta, Itziar R.; Zavala, Gonzalo; Bedia, Joaquin; Gutierrez, Jose M.; San Miguel-Ayanz, Jesus; Camia, Andrea; Keeley, Jon E.; Moreno, Jose M.

    2015-01-01

    Climate has a strong influence on fire activity, varying across time and space. We analyzed the relationships between fire–weather conditions during the main fire season and antecedent water-balance conditions and fires in two Mediterranean-type regions with contrasted management histories: five southern countries of the European Union (EUMED)(all fires); the Pacific western coast of the USA (California and Oregon, PWUSA)(national forest fires). Total number of fires (≥1 ha), number of large fires (≥100 ha) and area burned were related to mean seasonal fire weather index (FWI), number of days over the 90th percentile of the FWI, and to the standardized precipitation-evapotranspiration index (SPEI) from the preceding 3 (spring) or 8 (autumn through spring) months. Calculations were made at three spatial aggregations in each area, and models related first-difference (year-to-year change) of fires and FWI/climate variables to minimize autocorrelation. An increase in mean seasonal FWI resulted in increases in the three fire variables across spatial scales in both regions. SPEI contributed little to explain fires, with few exceptions. Negative water-balance (dry) conditions from autumn through spring (SPEI8) were generally more important than positive conditions (moist) in spring (SPEI3), both of which contributed positively to fires. The R2 of the models generally improved with increasing area of aggregation. For total number of fires and area burned, the R2 of the models tended to decrease with increasing mean seasonal FWI. Thus, fires were more susceptible to change with climate variability in areas with less amenable conditions for fires (lower FWI) than in areas with higher mean FWI values. The relationships were similar in both regions, albeit weaker in PWUSA, probably due to the wider latitudinal gradient covered in PWUSA than in EUMED. The large variance explained by some of the models indicates that large-scale seasonal forecast could help anticipating

  9. Differential weathering and erosion in an inselberg landscape in southern Zimbabwe: A morphometric study and some notes on factors influencing the long-term development of inselbergs

    NASA Astrophysics Data System (ADS)

    Römer, Wolfgang

    2007-05-01

    A morphometric analysis of inselberg systems in southern Zimbabwe indicated that there are two types of inselberg systems that differ in the mode of development. Inselberg systems characterized by backwearing tend to occur on granitoid rocks that are foliated, highly fractured, and prone to grusification. The inselbergs are mostly of the koppie-type and are covered to a great extent with regolith or debris. The second type of inselbergs consists of sparsely fractured granitoid rocks, and areas underlain by these rocks are characterized by clusters of closely spaced rock domes. In the case of these inselbergs, backwearing is not indicated. They appear to be the result of the exposure of structurally pre-designed, highly resistant rock compartments. The hypothesis that differences in lithology and structure may influence the rate and style of inselberg development was tested by means of a simulation model. The simulations are run under the same boundary conditions with differing assumptions concerning role of divergent weathering. The results show that both modes of inselberg development may occur alongside one another as long as a critical relief is maintained. The modelling provided also indicates that, although the inselberg systems must have integrated several sequences of environmental changes during their development, these changes were not able to divert the general trend of the process-response system away from its steady course. Lithological and structural factors, which are responsible for the differences in the mobility of material on the inselberg sideslopes, are thus considered to be the primary source of influence of the different modes of inselberg development. It is suggested that the compositional and structural diversity in granitoid rock terrains is what enables inselbergs to pass through different development modes and sequences as rocks of differing resistance become subject to weathering during the development of the landscape.

  10. Fire activity as a function of fire-weather seasonal severity and antecedent climate across spatial scales in southern Europe and Pacific western USA

    NASA Astrophysics Data System (ADS)

    Urbieta, Itziar R.; Zavala, Gonzalo; Bedia, Joaquín; Gutiérrez, José M.; San Miguel-Ayanz, Jesús; Camia, Andrea; Keeley, Jon E.; Moreno, José M.

    2015-11-01

    Climate has a strong influence on fire activity, varying across time and space. We analyzed the relationships between fire-weather conditions during the main fire season and antecedent water-balance conditions and fires in two Mediterranean-type regions with contrasted management histories: five southern countries of the European Union (EUMED)(all fires); the Pacific western coast of the USA (California and Oregon, PWUSA)(national forest fires). Total number of fires (≥1 ha), number of large fires (≥100 ha) and area burned were related to mean seasonal fire weather index (FWI), number of days over the 90th percentile of the FWI, and to the standardized precipitation-evapotranspiration index (SPEI) from the preceding 3 (spring) or 8 (autumn through spring) months. Calculations were made at three spatial aggregations in each area, and models related first-difference (year-to-year change) of fires and FWI/climate variables to minimize autocorrelation. An increase in mean seasonal FWI resulted in increases in the three fire variables across spatial scales in both regions. SPEI contributed little to explain fires, with few exceptions. Negative water-balance (dry) conditions from autumn through spring (SPEI8) were generally more important than positive conditions (moist) in spring (SPEI3), both of which contributed positively to fires. The R2 of the models generally improved with increasing area of aggregation. For total number of fires and area burned, the R2 of the models tended to decrease with increasing mean seasonal FWI. Thus, fires were more susceptible to change with climate variability in areas with less amenable conditions for fires (lower FWI) than in areas with higher mean FWI values. The relationships were similar in both regions, albeit weaker in PWUSA, probably due to the wider latitudinal gradient covered in PWUSA than in EUMED. The large variance explained by some of the models indicates that large-scale seasonal forecast could help anticipating fire

  11. Carbonate shelf edge off southern Australia: A prograding open-platform margin

    NASA Astrophysics Data System (ADS)

    James, Noel P.; von der Borch, Christopher C.

    1991-10-01

    The southern continental margin of Australia is an extensive shelf that has been a site of cool-water carbonate deposition since Eocene time. The platform has no rim and is swept by high-energy waves and swells throughout the year. The shelf is deep (40 to 100 m) and typified by bryozoan-rich sediments. The shelf margin is a gentle incline that becomes progressively steeper seaward, except where it laps down onto offshore terraces. The edge of the Eucla Platform in the Great Australian Bight is used to illustrate that the margin is a series of extensive prograding clinoforms. Progradation is interpreted to be the result of off-shelf sediment transport and in-place carbonate production by actively growing deep-water bryozoa and sponges. This area is a potential model for ancient high-energy platform margins during geologic periods when large skeletal reef-building metazoans were scarce.

  12. Carbonate-evaporite sequences of the late Jurassic, southern and southwestern Arabian Gulf

    SciTech Connect

    Alsharhan, A.S.; Whittle, G.L.

    1995-11-01

    The carbonate-evaporite sequences of the Upper Jurassic Arab and overlying Hith formations in the southern and southwestern Arabian Gulf form many supergiant and giant fields that produce from the Arab Formation and are excellent examples of a classic reservoir/seal relationship. The present-day sabkha depositional setting that extends along most of the southern and southwestern coasts of the Arabian Gulf provides an analog to these Upper Jurassic sedimentary rocks. In fact, sabkha-related diagenesis of original grain-supported sediments in the Arab and Hith formations has resulted in five distinct lithofacies that characterize the reservoir/seal relationship: (1) oolitic/peloidal grainstone, (2) dolomitic grainstone, (3) dolomitic mudstone, (4) dolomitized grainstone, and (5) massive anhydrite. Interparticle porosity in grainstones and dolomitic grainstones and intercrystalline porosity in dolomitized rocks provide the highest porosity in the study area. These sediments accumulated in four types of depositional settings: (1) supratidal sabkhas, (2) intertidal mud flats and stromatolitic flats, (3) shallow subtidal lagoons, and (4) shallow open-marine shelves. The diagenetic history of the Arab and Hith formations in the southern and southwestern Arabian Gulf suggests that the anhydrite and much of the dolomitization are a result of penecontemporaneous sabkha diagenesis. The character and timing of the paragenetic events are responsible for the excellent porosity of the Arab Formation and the lack of porosity in the massive anhydrites of the Hith, which together result in the prolific hydrocarbon sequences of these formations.

  13. Large igneous provinces and organic carbon burial: Controls on global temperature and continental weathering during the Early Cretaceous

    NASA Astrophysics Data System (ADS)

    Bodin, Stéphane; Meissner, Philipp; Janssen, Nico M. M.; Steuber, Thomas; Mutterlose, Jörg

    2015-10-01

    There is an abundance of evidence for short intervals of cold climatic conditions during the Early Cretaceous. However, the lack of a high-resolution, long-term Early Cretaceous paleotemperature record hampers a full-scale synthesis of these putative ;cold snap; episodes, as well as a more holistic approach to Early Cretaceous climate changes. We present an extended compilation of belemnite-based oxygen, carbon and strontium isotope records covering the Berriasian-middle Albian from the Vocontian Basin (SE France). This dataset clearly demonstrates three intervals of cold climatic conditions during the Early Cretaceous (late Valanginian-earliest Hauterivian, late early Aptian, latest Aptian-earliest Albian). Each of these intervals is associated with rapid and high amplitude sea-level fluctuations, supporting the hypothesis of transient growth of polar ice caps during the Early Cretaceous. As evidenced by positive carbon isotope excursions, each cold episode is associated with enhanced burial of organic matter on a global scale. Moreover, there is a relatively good match between the timing and size of large igneous province eruptions and the amplitude of Early Cretaceous warming episodes. Altogether, these observations confirm the instrumental role of atmospheric CO2 variations in driving Early Cretaceous climate change. From a long-term perspective, the coupling of global paleotemperature and seawater strontium isotopic ratio during the Early Cretaceous is best explained by temperature-controlled changes of continental crust weathering rates.

  14. The Southern Ocean as a constraint to reduce uncertainty in future ocean carbon sinks

    DOE PAGES

    Kessler, A.; Tjiputra, J.

    2016-04-07

    Earth system model (ESM) simulations exhibit large biases compares to observation-based estimates of the present ocean CO2 sink. The inter-model spread in projections increases nearly 2-fold by the end of the 21st century and therefore contributes significantly to the uncertainty of future climate projections. In this study, the Southern Ocean (SO) is shown to be one of the hot-spot regions for future uptake of anthropogenic CO2, characterized by both the solubility pump and biologically mediated carbon drawdown in the spring and summer. Here, we show, by analyzing a suite of fully interactive ESMs simulations from the Coupled Model Intercomparison Project phasemore » 5 (CMIP5) over the 21st century under the high-CO2 Representative Concentration Pathway (RCP) 8.5 scenario, that the SO is the only region where the atmospheric CO2 uptake rate continues to increase toward the end of the 21st century. Furthermore, our study discovers a strong inter-model link between the contemporary CO2 uptake in the Southern Ocean and the projected global cumulated uptake over the 21st century. This strong correlation suggests that models with low (high) carbon uptake rate in the contemporary SO tend to simulate low (high) uptake rate in the future. None the less, our analysis also shows that none of the models fully capture the observed biophysical mechanisms governing the CO2 fluxes in the SO. The inter-model spread for the contemporary CO2 uptake in the Southern Ocean is attributed to the variations in the simulated seasonal cycle of surface pCO2. Two groups of model behavior have been identified. The first one simulates anomalously strong SO carbon uptake, generally due to both too strong a net primary production and too low a surface pCO2 in December–January. The second group simulates an opposite CO2 flux seasonal phase, which is driven mainly by the bias in the sea surface temperature variability. Furthermore, we show that these biases are persistent throughout the 21st

  15. The Southern Ocean as a constraint to reduce uncertainty in future ocean carbon sinks

    SciTech Connect

    Kessler, A.; Tjiputra, J.

    2016-04-07

    Earth system model (ESM) simulations exhibit large biases compares to observation-based estimates of the present ocean CO2 sink. The inter-model spread in projections increases nearly 2-fold by the end of the 21st century and therefore contributes significantly to the uncertainty of future climate projections. In this study, the Southern Ocean (SO) is shown to be one of the hot-spot regions for future uptake of anthropogenic CO2, characterized by both the solubility pump and biologically mediated carbon drawdown in the spring and summer. Here, we show, by analyzing a suite of fully interactive ESMs simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5) over the 21st century under the high-CO2 Representative Concentration Pathway (RCP) 8.5 scenario, that the SO is the only region where the atmospheric CO2 uptake rate continues to increase toward the end of the 21st century. Furthermore, our study discovers a strong inter-model link between the contemporary CO2 uptake in the Southern Ocean and the projected global cumulated uptake over the 21st century. This strong correlation suggests that models with low (high) carbon uptake rate in the contemporary SO tend to simulate low (high) uptake rate in the future. None the less, our analysis also shows that none of the models fully capture the observed biophysical mechanisms governing the CO2 fluxes in the SO. The inter-model spread for the contemporary CO2 uptake in the Southern Ocean is attributed to the variations in the simulated seasonal cycle of surface pCO2. Two groups of model behavior have been identified. The first one simulates anomalously strong SO carbon uptake, generally due to both too strong a net primary production and too low a surface pCO2 in December–January. The second group simulates an opposite CO2 flux seasonal phase, which is driven mainly by the

  16. The Southern Ocean as a constraint to reduce uncertainty in future ocean carbon sinks

    NASA Astrophysics Data System (ADS)

    Kessler, A.; Tjiputra, J.

    2016-04-01

    Earth system model (ESM) simulations exhibit large biases compares to observation-based estimates of the present ocean CO2 sink. The inter-model spread in projections increases nearly 2-fold by the end of the 21st century and therefore contributes significantly to the uncertainty of future climate projections. In this study, the Southern Ocean (SO) is shown to be one of the hot-spot regions for future uptake of anthropogenic CO2, characterized by both the solubility pump and biologically mediated carbon drawdown in the spring and summer. We show, by analyzing a suite of fully interactive ESMs simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5) over the 21st century under the high-CO2 Representative Concentration Pathway (RCP) 8.5 scenario, that the SO is the only region where the atmospheric CO2 uptake rate continues to increase toward the end of the 21st century. Furthermore, our study discovers a strong inter-model link between the contemporary CO2 uptake in the Southern Ocean and the projected global cumulated uptake over the 21st century. This strong correlation suggests that models with low (high) carbon uptake rate in the contemporary SO tend to simulate low (high) uptake rate in the future. Nevertheless, our analysis also shows that none of the models fully capture the observed biophysical mechanisms governing the CO2 fluxes in the SO. The inter-model spread for the contemporary CO2 uptake in the Southern Ocean is attributed to the variations in the simulated seasonal cycle of surface pCO2. Two groups of model behavior have been identified. The first one simulates anomalously strong SO carbon uptake, generally due to both too strong a net primary production and too low a surface pCO2 in December-January. The second group simulates an opposite CO2 flux seasonal phase, which is driven mainly by the bias in the sea surface temperature variability. We show that these biases are persistent throughout the 21st century, which highlights the

  17. The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink

    PubMed Central

    Abelmann, Andrea; Gersonde, Rainer; Knorr, Gregor; Zhang, Xu; Chapligin, Bernhard; Maier, Edith; Esper, Oliver; Friedrichsen, Hans; Lohmann, Gerrit; Meyer, Hanno; Tiedemann, Ralf

    2015-01-01

    Reduced surface–deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface–subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring–summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall–winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink. PMID:26382319

  18. Dynamism of household carbon emissions (HCEs) from rural and urban regions of northern and southern China.

    PubMed

    Maraseni, Tek Narayan; Qu, Jiansheng; Yue, Bian; Zeng, Jingjing; Maroulis, Jerry

    2016-10-01

    China contributes 23 % of global carbon emissions, of which 26 % originate from the household sector. Due to vast variations in both climatic conditions and the affordability and accessibility of fuels, household carbon emissions (HCEs) differ significantly across China. This study compares HCEs (per person) from urban and rural regions in northern China with their counterparts in southern China. Annual macroeconomic data for the study period 2005 to 2012 were obtained from Chinese government sources, whereas the direct HCEs for different types of fossil fuels were obtained using the IPCC reference approach, and indirect HCEs were calculated by input-output analysis. Results suggest that HCEs from urban areas are higher than those from rural areas. Regardless of the regions, there is a similarity in per person HCEs in urban areas, but the rural areas of northern China had significantly higher HCEs than those from southern China. The reasons for the similarity between urban areas and differences between rural areas and the percentage share of direct and indirect HCEs from different sources are discussed. Similarly, the reasons and solutions to why decarbonising policies are working in urban areas but not in rural areas are discussed.

  19. The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink.

    PubMed

    Abelmann, Andrea; Gersonde, Rainer; Knorr, Gregor; Zhang, Xu; Chapligin, Bernhard; Maier, Edith; Esper, Oliver; Friedrichsen, Hans; Lohmann, Gerrit; Meyer, Hanno; Tiedemann, Ralf

    2015-09-18

    Reduced surface-deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface-subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring-summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall-winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink.

  20. The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink

    NASA Astrophysics Data System (ADS)

    Abelmann, Andrea; Gersonde, Rainer; Knorr, Gregor; Zhang, Xu; Chapligin, Bernhard; Maier, Edith; Esper, Oliver; Friedrichsen, Hans; Lohmann, Gerrit; Meyer, Hanno; Tiedemann, Ralf

    2015-09-01

    Reduced surface-deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface-subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring-summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall-winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink.

  1. Cambrian-lower Middle Ordovician passive carbonate margin, southern Appalachians: Chapter 14

    USGS Publications Warehouse

    Read, J. Fred; Repetski, John E.

    2012-01-01

    The southern Appalachian part of the Cambrian–Ordovician passive margin succession of the great American carbonate bank extends from the Lower Cambrian to the lower Middle Ordovician, is as much as 3.5 km (2.2 mi) thick, and has long-term subsidence rates exceeding 5 cm (2 in.)/k.y. Subsiding depocenters separated by arches controlled sediment thickness. The succession consists of five supersequences, each of which contains several third-order sequences, and numerous meter-scale parasequences. Siliciclastic-prone supersequence 1 (Lower Cambrian Chilhowee Group fluvial rift clastics grading up into shelf siliciclastics) underlies the passive margin carbonates. Supersequence 2 consists of the Lower Cambrian Shady Dolomite–Rome-Waynesboro Formations. This is a shallowing-upward ramp succession of thinly bedded to nodular lime mudstones up into carbonate mud-mound facies, overlain by lowstand quartzose carbonates, and then a rimmed shelf succession capped by highly cyclic regressive carbonates and red beds (Rome-Waynesboro Formations). Foreslope facies include megabreccias, grainstone, and thin-bedded carbonate turbidites and deep-water rhythmites. Supersequence 3 rests on a major unconformity and consists of a Middle Cambrian differentiated rimmed shelf carbonate with highly cyclic facies (Elbrook Formation) extending in from the rim and passing via an oolitic ramp into a large structurally controlled intrashelf basin (Conasauga Shale). Filling of the intrashelf basin caused widespread deposition of thin quartz sandstones at the base of supersequence 4, overlain by widespread cyclic carbonates (Upper Cambrian lower Knox Group Copper Ridge Dolomite in the south; Conococheague Formation in the north). Supersequence 5 (Lower Ordovician upper Knox in the south; Lower to Middle Ordovician Beekmantown Group in the north) has a basal quartz sandstone-prone unit, overlain by cyclic ramp carbonates, that grade downdip into thrombolite grainstone and then storm

  2. Regional variations in water quality and relationships to soil and bedrock weathering in the southern Sacramento Valley, California, USA

    USGS Publications Warehouse

    Wanty, R.B.; Goldhaber, M.B.; Morrison, J.M.; Lee, L.

    2009-01-01

    Regional patterns in ground- and surface-water chemistry of the southern Sacramento Valley in California were evaluated using publicly available geochemical data from the US Geological Survey's National Water Information System (NWIS). Within the boundaries of the study area, more than 2300 ground-water analyses and more than 20,000 surface-water analyses were available. Ground-waters from the west side of the Sacramento Valley contain greater concentrations of Na, Ca, Mg, B, Cl and SO4, while the east-side ground-waters contain greater concentrations of silica and K. These differences result from variations in surface-water chemistry as well as from chemical reactions between water and aquifer materials. Sediments that fill the Sacramento Valley were derived from highlands to the west (the Coast Ranges) and east (the Sierra Nevada Mountains), the former having an oceanic provenance and the latter continental. These geologic differences are at least in part responsible for the observed patterns in ground-water chemistry. Thermal springs that are common along the west side of the Sacramento Valley appear to have an effect on surface-water chemistry, which in turn may affect the ground-water chemistry.

  3. Organic and Elemental Carbon Aerosol Particulates at the Southern Great Plains Site Field Campaign Report

    SciTech Connect

    Cary, Robert

    2016-04-01

    The purpose of this study was to measure the organic carbon (OC) and elemental carbon (EC) fractions of PM2.5 particulate matter at the U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) Climate Research Facility Southern Great Plains (SGP) sampling site for a 6-month period during the summer of 2013. The site is in a rural location remote from any populated areas, so it would be expected to reflect carbon concentration over long-distance transport patterns. During the same period in 2012, a number of prairie fires in Oklahoma and Texas had produced large plumes of smoke particles, but OC and EC particles had not been quantified. In addition, during the summer months, other wild fires, such as forest fires in the Rocky Mountain states and other areas, can produce carbon aerosols that are transported over long distances. Both of these source types would be expected to contain mixtures of both OC and EC.

  4. Dynamics of the Particulate Organic Carbon in the southern Baltic Sea.

    NASA Astrophysics Data System (ADS)

    Dzierzbicka-Glowacka, L.; Maciejewska, A.; Kuliński, K.; Pempkowiak, J.

    2009-04-01

    This paper presents a one-dimensional Particulate Organic Carbon Dynamic Model 1D-POCD. The particulate organic carbon concentration is determined as the sum of phytoplankton, zooplankton and dead organic matter (detritus) concentrations. Mathematically, the pelagic variables of 1D-POCD model are described by a second-order partial differential equation of the diffusion type with biogeochemical sources and sinks. The temporal changes in the phytoplankton biomass are caused by primary production, respiration, mortality, grazing by zooplankton and sinking. The zooplankton biomass is affected by ingestion, excretion, respiration, fecal production, mortality, and carnivorous grazing. The changes in the pelagic detritus concentration are determined by input of: dead phytoplankton and zooplankton, natural mortality of predators, fecal pellets, and sinks: sedimentation, zooplankton grazing and decomposition. The 1D-POCD model was used to simulate the seasonal dynamics of particulate organic carbon fluxes in the southern Baltic Sea (Gdańsk Deep, Bornholm Deep and Gotland Deep). The results of the simulations were compared with the mean concentrations of particulate organic carbon recorded in situ at station situated at the Gdańsk Deep. Generally good agreement between the measured and modeled POC concentration was obtained.

  5. How deep is deep enough? Ocean iron fertilization and carbon sequestration in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Robinson, J.; Popova, E. E.; Yool, A.; Srokosz, M.; Lampitt, R. S.; Blundell, J. R.

    2014-04-01

    Artificial ocean iron fertilization (OIF) enhances phytoplankton productivity and is being explored as a means of sequestering anthropogenic carbon within the deep ocean. To be considered successful, carbon should be exported from the surface ocean and isolated from the atmosphere for an extended period (e.g., the Intergovernmental Panel on Climate Change's standard 100 year time horizon). This study assesses the impact of deep circulation on carbon sequestered by OIF in the Southern Ocean, a high-nutrient low-chlorophyll region known to be iron stressed. A Lagrangian particle-tracking approach is employed to analyze water mass trajectories over a 100 year simulation. By the end of the experiment, for a sequestration depth of 1000 m, 66% of the carbon had been reexposed to the atmosphere, taking an average of 37.8 years. Upwelling occurs predominately within the Antarctic Circumpolar Current due to Ekman suction and topography. These results emphasize that successful OIF is dependent on the physical circulation, as well as the biogeochemistry.

  6. Carbon Dioxide and Water Cycling in a Semiarid Savanna in Southern Arizona, USA

    NASA Astrophysics Data System (ADS)

    Scott, R. L.; Hultine, K.; Barron-Gafford, G.; Huxman, T.

    2007-12-01

    The consequences of recent woody plant encroachment on the carbon and water cycling of semiarid ecosystems are not well understood. In this presentation, we present measurements made from 2004 - 2006 using sap flow and eddy covariance techniques to examine the carbon dioxide and water fluxes that occurred over a semiarid savanna on the Santa Rita Experimental Range in southern Arizona, USA. Over the last one hundred years this site has been transformed from a desert grassland to a savanna with greater than 35% tree cover by the encroachment of the native woody plant, mesquite ( Prosopis velutina). We have found that mesquite, even when they were dormant above ground, readily redistributed water upwards and downwards in the soil profile via their roots. This redistribution had important ecohydrological consequences like extending the season over which photosynthesis occurred. During the study period the site experienced below normal precipitation especially during the winter and spring period, and the site each year appeared to be a net carbon source. The two decades that preceded our study had above average precipitation, and this possibly resulted in a great deal of carbon accumulation that is now being released due to the current drought that has truncated the growing season.

  7. Thinning, Age, and Site Quality Influence Live Tree Carbon Stocks in Upland Hardwood Forests of the Southern Appalachians

    Treesearch

    Tara L. Keyser; Stanley J. Zarnoch

    2012-01-01

    This study examines the effects of thinning, age, and site quality on aboveground live tree carbon (ATC) (Mg/ha) stocks in upland hardwood forests of mixed-species composition in the southern Appalachian Mountains. In 1974, 80 plots ranging in size from 0.06 to 0.1 ha were established in even-aged, mixed-hardwood forests throughout the southern Appalachians. All trees...

  8. Interdisciplinary Coordinated Experiment of the Southern Ocean Carbon Cycle (ICESOCC) - A Field Campaign Scoping Project

    NASA Astrophysics Data System (ADS)

    Mitchell, B. G.

    2015-12-01

    Accurate estimates in time and space of organic carbon export to the ocean interior via plankton net community production (NCP) for the global oceans (the biological pump) are essential for understanding the feedback between NCP, atmospheric CO2 and climate. Since integrated, multi-sensor satellite and in situ observations of many ocean variables are required to estimate NCP from space, this is a complex, interdisciplinary challenge. Satellite ocean color sensors are a fundamental component in estimating spatial and temporal variations in NCP. Therefore, NASA's PACE mission (NASA-PACE 2012), a mission included in NASA's Climate Architecture Plan (NASA-CAP, 2010), specifies a need for field programs to improve satellite algorithms and models to reduce uncertainties in estimates of NCP. Diverse data from sediment and glacial cores, and climate models, indicate that the Southern Ocean plays a large role in the glacial-interglacial variations in the biological pump, with considerable implications for variations in atmospheric CO2. The "Interdisciplinary Coordinated Experiment of the Southern Ocean Carbon Cycle (ICESOCC)" project is a NASA-funded field campaign scoping (planning) effort. Over 18 months and many public meetings and workshops, the ICESOCC team of 13 interdisciplinary scientists has integrated the input from scientific experts in ocean, atmosphere, ice physics, biogeochemistry, advanced observational tools (ship, autonomous, atmospheric gases and dust, cryosphere dynamics, winds), and models, to create a draft recommendation to NASA for field observations required to constrain uncertainty of NCP for the Southern Ocean. The ICESOCC team requests and encourages careful review and comments of the draft to ensure the most robust final recommendations are submitted in early 2016 for NASA consideration.

  9. Weathering Processes Across Extreme Erosional Gradients: Do Landslides Matter?

    NASA Astrophysics Data System (ADS)

    Emberson, R.; Hovius, N.; Galy, A.; Marc, O.

    2015-12-01

    A process-based understanding of weathering in actively eroding mountain belts is vital to understand how linkages between erosion and weathering affect global biogeochemical cycles on a range of timescales. Here we present surface water chemistry data from Southern Taiwan that demonstrates the impact of variable erosive processes on weathering budgets on a large range of scales, from tens of metres to large catchments (>50km2). Southern Taiwan is an excellent example of a number of gradients in erosive processes, with relief and median slope increasing from the southernmost small hills to mountainous threshold-hillslopes with up to 2.5km of relief approximately 100km to the north. Furthermore, Typhoon Morakot (2009) triggered extremely extensive landsliding in some catchments within this zone, allowing distinctions to be drawn between average topographic characteristics of catchments and the erosive processes (i.e. mass wasting) at work therein. Landslides play an important role in localising weathering in deposits with high internal surface area and slow throughflow of fluids, creating sites of rapid weathering which can be a first order control on catchment solute budgets in watersheds where landslides deposits and scars exceed 2% of drained area. Variation in the detailed chemistry of landslide seepages - particularly the carbonate/silicate weathering balance - indicates that this process has a different impact on inorganic weathering-driven carbon cycling than slower erosive processes; a strong positive correlation between landslide-affected area and Ca2+:Si ratios on catchment scale suggests rapid erosion is not strongly coupled to CO2 drawdown. Rapid oxidation of sulphides - ubiquitous in many rapidly eroding mountain belts - within highly fragmented landslide deposits, and associated sulphuric-acid driven weathering, further complicates the effect landsliding has on the carbon cycle.

  10. Proposal of a New Parameter for the Weathering Characterization of Carbonate Flysch-Like Rock Masses: The Potential Degradation Index (PDI)

    NASA Astrophysics Data System (ADS)

    Cano, M.; Tomás, R.

    2016-07-01

    The susceptibility of clay bearing rocks to weathering (erosion and/or differential degradation) is known to influence the stability of heterogeneous slopes. However, not all of these rocks show the same behaviour, as there are considerable differences in the speed and type of weathering observed. As such, it is very important to establish relationships between behaviour quantified in a laboratory environment with that observed in the field. The slake durability test is the laboratory test most commonly used to evaluate the relationship between slaking behaviour and rock durability. However, it has a number of disadvantages; it does not account for changes in shape and size in fragments retained in the 2 mm sieve, nor does its most commonly used index (Id2) accurately reflect weathering behaviour observed in the field. The main aim of this paper is to propose a simple methodology for characterizing the weathering behaviour of carbonate lithologies that outcrop in heterogeneous rock masses (such as Flysch slopes), for use by practitioners. To this end, the Potential Degradation Index (PDI) is proposed. This is calculated using the fragment size distribution curves taken from material retained in the drum after each cycle of the slake durability test. The number of slaking cycles has also been increased to five. Through laboratory testing of 117 samples of carbonate rocks, extracted from strata in selected slopes, 6 different rock types were established based on their slaking behaviour, and corresponding to the different weathering behaviours observed in the field.

  11. Lithological and Petrographic Analyses of Carbonates and Sandstones From the Southern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Garcia-Avendaño, A.; Urrutia-Fucugauchi, J.

    2012-04-01

    We present results of sedimentological and petrological studies of drill cores from the Bay of Campeche in the southern Gulf of Mexico. Based on reports on drill cores obtained from oil exploratory wells in the Cantarell Complex located 80 kilometres offshore in the Bay of Campeche and studies related to regional geology composite simplified stratigraphic columns for offshore Campeche region have been constructed up to depths of approximately 5000 m. The stratigraphic column is formed by a thick sediment sequence of Middle Jurassic age (evaporites, Callovian), Late Jurassic (terrigenous, calcareous clays and calcareous layers), Lower Cretaceous (carbonates), Upper Cretaceous-Paleogene (calcareous breccias), Paleogene-Neogene (terrigenous-carbonates intercalations) and Quaternary (terrigenous). The core samples studied come from wells in the Sihil and Akal fields in Cantarell. Analysis of reports on lithological descriptions indicates that these wells sample dolomitized sedimentary breccias from the Upper Cretaceous-Paleocene and fine-grained sandstones from the Late Jurassic Tithonian, respectively. Based on results of petrographic studies, the texture, cementing material and porosity of the units have been documented. The thin sections for carbonates were classified based on their texture according to Dunham (1962) for carbonate rocks, classified according to their components using the ternary diagrams of Folk (1974). Percentages refer to the data presented in tables, which were obtained by point-counting technique (with a total 250). Photomicrographs of scanning electron microscope (SEM) provide magnification for easy documentation of crystalline arrangements and description of micro-porous for different types of carbonates such as dolomite, in addition to the morphology of authigenic clays. Results of these studies and previous works in the area permit characterization of diagenetic processes of the carbonate sediments in the Campeche Bay, and provide

  12. Subsurface Permian reef complexes of southern Tunisia: Shelf carbonate setting and paleogeographic implications

    NASA Astrophysics Data System (ADS)

    Zaafouri, Adel; Haddad, Sofiene; Mannaî-Tayech, Beya

    2017-05-01

    2-D seismic reflection sections, borehole data as well as published and unpublished data have been investigated to reconstruct the paleogeography of southern Tunisia during Middle to Late Permian times. Paleogeographical reconstruction based on the integration of petroleum well data and 2-D seismic facies interpretation shows three main depositional areas with very contrasting sedimentary pile. These are 1) a subsiding basin; 2) an outer shelf carbonate, and 3) an inner shelf carbonate. Based on typical electric responses of reef buildups to seismic wave, we shall urge that during Middle Permian times, the outer carbonate shelf was subject of reef barrier development. Lithology evidences from core samples show that reef framework correspond mainly to fossiliferous limestone and dolomite. The WNW-ESE recognized reef barrier led between latitudes 33° 10‧ 00″N and 33° 20‧ 00″N. The Tebaga of Medenine outcrop constitutes the northern-edge of this barrier. Westward it may be extended to Bir Soltane area whereas its extension eastward is still to be determined. Biogenic buildups took place preferentially over faulted Carboniferous and lower Paleozoic paleohighs resulting likely from the Hercynian orogeny. The subsiding basin is located north of Tebaga of Medenine outcrop where Upper Permian sedimentary sequence is made entirely of 4000 m deep marine green silty shale facies. These are ascribed to unorganized and chaotic reflectors. Inner carbonate shelf facies succession corresponds to a typical interbedding of shallow marine carbonate deposits, shale, dolomite, and anhydrite inducing parallel-layered of strong amplitude and good continuity reflectors. Also within the inner carbonate shelf patch reef or reef pinnacles have been identified based on their seismic signature particularly their low vertical development as compared to reef complexes. Southward, towards Sidi Toui area, the Upper Permian depositional sequence thins out and bears witness of land

  13. Remagnetization of carbonate rocks in southern Tibet: Perspectives from rock magnetic and petrographic investigations

    NASA Astrophysics Data System (ADS)

    Huang, Wentao; Lippert, Peter C.; Zhang, Yang; Jackson, Michael J.; Dekkers, Mark J.; Li, Juan; Hu, Xiumian; Zhang, Bo; Guo, Zhaojie; van Hinsbergen, Douwe J. J.

    2017-04-01

    The latitudinal motion of the Tibetan Himalaya—the northernmost continental unit of the Indian plate—is a key component in testing paleogeographic reconstructions of the Indian plate before the India-Asia collision. Paleomagnetic studies of sedimentary rocks (mostly carbonate rocks) from the Tibetan Himalaya are complicated by potentially pervasive yet cryptic remagnetization. Although traditional paleomagnetic field tests reveal some of this remagnetization, secondary remanence acquired prior to folding or tilting easily escapes detection. Here we describe comprehensive rock magnetic and petrographic investigations of Jurassic to Paleocene carbonate and volcaniclastic rocks from Tibetan Himalayan strata (Tingri and Gamba areas). These units have been the focus of several key paleomagnetic studies for Greater Indian paleogeography. Our results reveal that while the dominant magnetic carrier in both carbonate and volcaniclastic rocks is magnetite, their magnetic and petrographic characteristics are distinctly different. Carbonate rocks have "wasp-waisted" hysteresis loops, suppressed Verwey transitions, extremely fine grain sizes (superparamagnetic), and strong frequency-dependent magnetic susceptibility. Volcaniclastic rocks exhibit "pot-bellied" hysteresis loops and distinct Verwey transitions. Electron microscopy reveals that magnetite grains in carbonate rocks are pseudomorphs of early diagenetic pyrite, whereas detrital magnetite is abundant and pyrite is rarely oxidized in the volcaniclastic rocks. We suggest that the volcaniclastic rocks retain a primary remanence, but oxidation of early diagenetic iron sulfide to fine-grained magnetite has likely caused widespread chemical remagnetization of the carbonate units. We recommend that thorough rock magnetic and petrographic investigations are prerequisites for paleomagnetic studies throughout southern Tibet and everywhere in general.

  14. Examining Patterns of Carbon Assimilation and Allocation to Defense Processes in a Restored Southern Pine Forest

    NASA Astrophysics Data System (ADS)

    Ritger, H.; Novick, K. A.

    2014-12-01

    Southern pine forests provide many important ecosystem services, including biodiversity, carbon sequestration, and softwood timber production, which is a vital component of local economies in the American South. However, all southern pine forests are sensitive to damage from infestations of bark beetles and drought events, which can lead to declines in productivity that may cause mortality in extreme cases, and which may increase in frequency in the future due to ongoing climate change. This study explores how southern pine management for restored, old-growth like conditions, in contrast with management for timber production, affects stand scale drought response and tree resistance to bark beetle herbivory by leveraging a suite of data from a new eddy covariance flux monitoring site in a 65-year-old restored loblolly (Pinus taeda) and shortleaf (Pinus echinata) pine forest situated in the Crossett Experimental Forest (Arkansas, USA). The sensitivity of ecosystem scale fluxes of CO2 and H2O to drought is interpreted through a synthesis with other long-running Ameriflux sites located in southern pine forests. The effects of the management regime on resin production, which is the pine trees' main defense against beetle attacks, are assessed by comparing monthly resin flow observations collected over the course of the 2013 growing season in the restored stand and in a co-located stand of even-age planted loblolly pines managed for timber production. Results show that loblolly in the uneven-aged stand consistently produced much larger amounts of resin than loblolly in the even-aged stand, and shortleaf pines were the lowest producers throughout the growing season. No significant relationship between resin flow and diameter at breast height was observed within or across species and sites; thus, species and management effects are independent of their effect on tree size.

  15. Mineral Occurrence, Translocation, and Weathering in Soils Developed on Four Types of Carbonate and Non-carbonate Alluvial Fan Deposits in Mojave Desert, Southeastern California

    NASA Astrophysics Data System (ADS)

    Deng, Y.; McDonald, E. V.

    2007-12-01

    Soil geomorphology and mineralogy can reveal important clues about Quaternary climate change and geochemical process occurring in desert soils. We investigated (1) the mineral transformation in desert soils developed on four types of alluvial fans (carbonate and non-carbonate) under the same conditions of climate and landscape evolution; and (2) the effects of age, parent materials, and eolian processes on the transformation and translocation of the minerals. Four types of alluvial-fan deposits along the Providence Mountains piedmonts, Mojave Desert, southeastern California, USA were studied: (1) carbonate rocks, primarily limestone and marble (LS), (2) fine-grained rhyodacite and rhyolitic tuff mixed with plutonic and carbonate rocks (VX), (3) fine- to coarse- grained mixed plutonic (PM) rocks, and (4) coarse-grained quartz monzonite (QM). These juxtaposed fan deposits are physically correlated in a small area (about 20 km by 15 km) and experienced the same climatic changes in the late Pleistocene and Holocene. The soils show characteristic mineral compositions of arid/semiarid soils: calcite is present in nearly all of the samples, and a few of the oldest soils contain gypsum and soluble salts. Parent material has profound influence on clay mineral composition of the soils: (1) talc were observed only in soils developed on the volcanic mixture fan deposits, and talc occurs in all horizons; (2) palygorskite occur mainly in the petrocalcic (Bkm) of old soils developed on the LS and VX fan deposits, indicating pedogenic origin; (3) chlorite was observed mainly in soils developed on VX fan deposits (all ages) and on some LS deposits, but it is absent in soils developed on PM and QM fan deposits; and (4) vermiculite was common throughout soils developed on plutonic rock fan deposits. These mineralogical differences suggest that minerals in the soils are primarily inherited from their parent materials and that mineral weathering in this area was weak. Except the

  16. Regional Carbon Fluxes and Atmospheric Carbon Dynamics in the Southern Great Plains during the 2007 Mid Continent Intensive of NACP

    NASA Astrophysics Data System (ADS)

    Torn, M. S.; Fischer, M. L.; Riley, W. J.; Jackson, T. J.; Avissar, R.; Biraud, S. C.; Billesbach, D. P.; Sweeney, C.; Tans, P. P.; Berry, J. A.

    2006-12-01

    In June 2007, an intensive regional campaign will take place in the Southern Great Plains (SGP) to estimate land-atmosphere exchanges of CO2, water, and energy at 1 to 100 km scales. The primary goals of this North American Carbon Program (NACP) campaign are to evaluate top-down and bottom-up estimates of regional fluxes and to understand the influence of moisture gradients, surface heterogeneity, and atmospheric transport patterns on these fluxes (and their estimation). The work will be integrated with the Cloud and Land Surface Interaction Campaign (CLASIC), centered on the US DOE Atmospheric Radiation Measurement Program SGP region. CLASIC will focus on interactions among the land surface, convective boundary layer, and cumulus clouds, and will utilize an array of atmospheric measurements. Carbon and meteorological data streams and logistical resources will be available to other NACP researchers. Carbon flux and concentration data will be collected from tower and airborne platforms. Eddy flux towers will be deployed in the four major land cover types, distributed over the region's SE to NW precipitation gradient. In addition, CO2, water, and energy fluxes will be observed with the Duke Helicopter Observation Platform (HOP) at various heights in the boundary layer, including in the surface layer (the few meters near the surface). Two aircraft will carry precise CO2 measurement systems and NOAA12-flask packages for carbon cycle gases and isotopes. Continuous CO2 and CO concentrations, NOAA flasks, and isotope diel flasks (14C, 13C, and 18O) will also be collected from a centrally located 60 m tower. Flights are planned to constrain simple boundary layer budget models and to conduct Lagrangian air mass following experiments. A distributed model of land surface fluxes will be run off line and coupled to MM5 with tracer capability. In addition to characterizing the influence of the land surface on the atmosphere, the aircraft data (in combination with observations of

  17. Annual carbon dioxide cycle in a montane soil: observations, modeling, and implications for weathering

    SciTech Connect

    Solomon, D.K.; Cerling, T.E.

    1987-12-01

    Profiles of CO/sub 2/ concentrations in soil and snow, soil respiration, soil and snow temperatures, and shallow ground water chemistry were monitored from March 1984 to July 1985 in a montane region neat Brighton, Utah. Significant seasonal variations in the concentrations of CO/sub 2/ in soil and snow occurred, and two principal rise-decline cycles were observed. During the first cycle the concentration of soil CO/sub 2/ at 35 cm rose from 4200 ppmv in July to a maximum of 12,400 ppmv in August and then declined to 4300 ppmv by October. This cycle is attributed to the changing production rate of soil CO/sub 2/ during the growing season. During the second cycle the concentration of CO/sub 2/ at 35 cm began to rise in November, reached a maximum of 7200 ppmv in early spring, and quickly declined to 3200 ppmv by late spring shortly after the snow cover had melted. This cycle is attributed to deterioration in the exchange of CO/sub 2/ between the soil and atmosphere due to a deep snowpack. A model based on Fick's second law of diffusion was developed to account for the temporal and spatial distribution of soil CO/sub 2/. The model predicts that soil CO/sub 2/ at 35 cm is increased by as much as 15 times due to the deep snowpack. The elevated concentration of soil CO/sub 2/, abundance of water, and above-freezing soil temperatures imply that significant soil weathering occurs during the winter in montane regions.

  18. A Southern Hemisphere atmospheric history of carbon monoxide from South Pole firn air

    NASA Astrophysics Data System (ADS)

    Verhulst, K. R.; Aydin, M.; Novelli, P. C.; Holmes, C. D.; Prather, M. J.; Saltzman, E. S.

    2013-12-01

    Carbon monoxide (CO) is a reactive trace gas and is important to tropospheric photochemistry as a major sink of hydroxyl radicals (OH). Major sources of CO are fossil fuel combustion, linked mostly to automotive emissions, biomass burning, and oxidation of atmospheric methane. Understanding changes in carbon monoxide over the past century will improve our understanding of man's influence on the reactivity of the atmosphere. Little observational information is available about CO levels and emissions prior to the 1990s, particularly for the Southern Hemisphere. The NOAA global flask network provides the most complete instrumental record of CO, extending back to 1988. Annually averaged surface flask measurements suggest atmospheric CO levels at South Pole were relatively stable from 2004-2009 at about 51 nmol mol-1 [Novelli and Masarie, 2013]. In this study, a 20th century atmospheric history of CO is reconstructed from South Pole firn air measurements, using a 1-D firn air diffusion model. Firn air samples were collected in glass flasks from two adjacent holes drilled from the surface to 118 m at South Pole, Antarctica during the 2008/2009 field season and CO analysis was carried out by NOAA/CCG. Carbon monoxide levels increase from about 45 nmol mol-1 in the deepest firn sample at 116 m to 52 nmol mol-1 at 107 m, and remain constant at about 51-52 nmol mol-1 at shallower depths. Atmospheric histories based on the firn air reconstructions suggest that CO levels over Antarctica increased by roughly 40% (from about 36 to 50 nmol mol-1) between 1930-1990, at a rate of about 0.18 nmol mol-1 yr-1. Firn air and surface air results suggest the rate of CO increase at South Pole slowed considerably after 1990. The firn air-based atmospheric history is used to infer changes in Southern Hemisphere CO emissions over the 20th century.

  19. Origin of enormous trace metal enrichments in weathering mantles of Jurassic carbonates: evidence from Sr, Nd and Pb isotopes

    NASA Astrophysics Data System (ADS)

    Hissler, C.; Stille, P.; Juilleret, J.; Iffly, J.; Perrone, T.; Morvan, G.

    2013-12-01

    Weathering mantels are widespread worldwide and include lateritic, sandy and kaolinite-rich saprolites and residuals of partially dissolved carbonate rocks. These old regolith systems have a complex history of formation and may present a polycyclic evolution due to successive geological and pedogenetic processes that affected the profile. Until now, only few studies highlighted the unusual content of associated trace elements in this type of weathering mantle. For instance, these enrichments can represent about five times the content of the underlying Bajocian to Oxfordian limestone/marl complexes, which have been relatively poorly studied compared to weathering mantle developed on magmatic bedrocks. Up to now, neither soil, nor saprolite formation has to our knowledge been geochemically elucidated. Therefore, the aim of this study was to examine more closely the soil forming dynamics and the relationship of the chemical soil composition to potential sources (saprolite, Bajocian silty marls and limestones, atmospheric particles deposition...). Of special interest has also been the origin of trace metals and the processes causing their enrichments. Especially Rare Earth Element (REE) distribution patterns and Sr, Nd and Pb isotope ratios are particularly well suited to identify trace element migration, to recognize origin and mixing processes and, in addition, to decipher possible anthropogenic and/or "natural" atmosphere-derived contributions to the soil. Moreover, leaching experiments shall help to identify mobile phases in the soil system. This may inform on the stability of trace elements and especially on their behaviour in these Fe-enriched carbonate systems. Trace metal migration and enrichments were studied on a cambisol developing on an underlying Jurassic limestone. The base is strongly enriched among others in rare earth elements (ΣREE: 2640ppm) or redox-sensitive elements such as Fe (44 wt.%), V (920ppm), Cr (700ppm), Zn (550ppm), As (260ppm), Co (45ppm

  20. Controls over the thickness and elemental enrichment patterns in microscopic weathering-zones in exposed and terra-rossa covered carbonate bedrock surfaces

    NASA Astrophysics Data System (ADS)

    Ryb, U.; Erel, Y.; Matmon, A.

    2014-12-01

    Weathering zone's mineral and chemical compositions reflect the processes that govern denudation. We study 0-2500 μm thick weathering zones that evolve below carbonate bedrock surfaces, which experienced prolong denudation under Mediterranean climate, in the Judea Hills, Israel. Samples were collected from exposed (n=13) and terra-rossa covered (n=12) surfaces. In a previous study, denudation rates were calculated for the exposed bedrock samples. Since most of the terra-rossa volume is derived from an aeolian source, we do not consider it an integral part of the rock weathering zone. Bulk rock compositions range from limestone to dolomite, and frequently consist of a mixture of calcite and dolomite minerals. We analyzed major and trace elements across the weathering zones using a laser-ablation ICPMS system. Selected samples were further analyzed with an electron-probe. The extent of weathering zones is marked by the variation of element concentrations near the rock surface (relatively to the bulk rock), at depths of 0-500 μm and 0-2500 μm in exposed and terra-rossa covered surfaces, respectively. These zones are characterized by a relatively high porosity resulting from carbonate-mineral dissolution below the surface. Correlation analyses within each profile reveal three major elemental correlations: (1) Mg-Sr-U correlation results from variation in the abundance of the mineral dolomite. These elements are typically depleted toward the surface, due to preferential dissolution of dolomite crystals and precipitation of secondary calcite; (2) Al-Si correlation results from variations in the abundance of clay minerals, which may concentrate as an insoluble residue, or derive from the outer environment; and, (3) P-Y-REE correlation is highly enriched toward the surface, suggesting contribution from the outer environment. In contrast to silicate rocks, the extent and intensity of the weathering zones of exposed carbonate surfaces are decoupled from denudation rates

  1. The contribution of changes in P release and CO2 consumption by chemical weathering to the historical trend in land carbon uptake

    NASA Astrophysics Data System (ADS)

    Goll, D. S.; Moosdorf, N.; Brovkin, V.; Hartmann, J.

    2013-12-01

    The atmospheric carbon dioxide (CO2) concentration has increased to a level unprecedented in the last 2 million years, and the concentration is projected to increase further with a rate unseen in geological past. The increase in CO2 cause a rise in surface temperatures and changes in the hydrological cycle through the redistribution of rainfall patterns. All of these changes will impact the weathering of rocks, which in turn affect atmospheric CO2 concentrations via two different pathways. On the one hand, CO2 is consumed by the dissolution reaction of the exposed minerals. And on the other hand, biological CO2 fixation is affected due to changes in phosphorus release from minerals, as biological activity is constrained by phosphorus availability at large scales. The traditional view is that both effects are negligible on a centennial time scale, but recent work on catchment scale challenge this view in favor of a potential high sensitivity of weathering to ongoing climate and land use changes. To globally quantify the contribution of CO2 fixation associated with weathering on the historical trend in terrestrial CO2 uptake, we applied a model of chemical weathering and phosphorus release under climate reconstructions from four Earth System Models. The simulations indicate that changes in weathering could have contributed considerably to the trend in terrestrial CO2 uptake since the pre-industrial revolution, with warming being the main driver of change. The increase in biological CO2 fixation is of comparable magnitude as the increase in CO2 consumption by chemical weathering. Our simulations support the previous findings on catchment scale that weathering can change significantly on a centennial time scale. This finding has implications for 21st century climate projections, which ignore changes in weathering, as well as for long-term airborne fraction of CO2 emissions, whose calculation usually neglects changes in phosphorus availability.

  2. The contribution of changes in P release and CO2 consumption by chemical weathering to the historical trend in land carbon uptake

    NASA Astrophysics Data System (ADS)

    Goodale, C. L.; Fredriksen, G.; McCalley, C. K.; Sparks, J. P.; Thomas, S. A.

    2011-12-01

    The atmospheric carbon dioxide (CO2) concentration has increased to a level unprecedented in the last 2 million years, and the concentration is projected to increase further with a rate unseen in geological past. The increase in CO2 cause a rise in surface temperatures and changes in the hydrological cycle through the redistribution of rainfall patterns. All of these changes will impact the weathering of rocks, which in turn affect atmospheric CO2 concentrations via two different pathways. On the one hand, CO2 is consumed by the dissolution reaction of the exposed minerals. And on the other hand, biological CO2 fixation is affected due to changes in phosphorus release from minerals, as biological activity is constrained by phosphorus availability at large scales. The traditional view is that both effects are negligible on a centennial time scale, but recent work on catchment scale challenge this view in favor of a potential high sensitivity of weathering to ongoing climate and land use changes. To globally quantify the contribution of CO2 fixation associated with weathering on the historical trend in terrestrial CO2 uptake, we applied a model of chemical weathering and phosphorus release under climate reconstructions from four Earth System Models. The simulations indicate that changes in weathering could have contributed considerably to the trend in terrestrial CO2 uptake since the pre-industrial revolution, with warming being the main driver of change. The increase in biological CO2 fixation is of comparable magnitude as the increase in CO2 consumption by chemical weathering. Our simulations support the previous findings on catchment scale that weathering can change significantly on a centennial time scale. This finding has implications for 21st century climate projections, which ignore changes in weathering, as well as for long-term airborne fraction of CO2 emissions, whose calculation usually neglects changes in phosphorus availability.

  3. Surface area dependence of calcium isotopic reequilibration in carbonates: Implications for isotopic signatures in the weathering zone

    NASA Astrophysics Data System (ADS)

    Fernandez, N. M.; Druhan, J. L.; Potrel, A.; Jacobson, A. D.

    2016-12-01

    The concept of dynamic equilibrium carries the implicit assumption of continued isotopic exchange between a mineral and the surrounding fluid. While this effect has received much attention in the marine paleoproxy literature, it has been relatively overlooked in application to the terrestrial environment. In weathering systems, a potential consequence is that rapid reequilibration may alter or erase isotopic signatures generated during secondary mineral formation. The extent and timescale over which isotopic signatures are reset in these hydrologic systems is unknown. Using reactive transport modeling, we show isotopic reequilibration under conditions reflecting terrestrial hydrologic settings to be significant and dependent on the reactive surface area of the solid. In particular, we suggest that the non-traditional stable isotopes commonly used in application to carbonates (e.g., Ca, Mg, Sr) are sensitive to these effects due to their rapid reaction rates. We aim to characterize the dependence of Ca isotopic reequilibration on surface area during calcite precipitation via batch experiments conducted at ambient temperature over 48-hour time periods. Calcite precipitation was performed in a closed batch reactor utilizing a controlled free-drift method. The batch reactors contained mixed supersaturated solutions of CaCl2 and NaHCO3 at an initial pH of 8.54. Precipitation was initiated by seed inoculation of calcite crystals with two distinct, pre-constrained surface areas. All experiments achieved the same final state of chemical equilibrium, but as expected, the fastest approach to equilibrium occurred for experiments employing calcite seeds with the highest surface area. This implies that differences in equilibrated Ca isotope ratios (δ44/40Ca) should reflect differences in surface area. This prediction is upheld by models of the experiments, indicating a measureable difference in δ44Ca during calcite precipitation where the higher surface area corresponds to

  4. Enhanced terrestrial weathering/runoff and surface ocean carbonate production during the recovery stages of the Paleocene-Eocene thermal maximum

    NASA Astrophysics Data System (ADS)

    Kelly, D. Clay; Zachos, James C.; Bralower, Timothy J.; Schellenberg, Stephen A.

    2005-12-01

    The carbonate saturation profile of the oceans shoaled markedly during a transient global warming event known as the Paleocene-Eocene thermal maximum (PETM) (circa 55 Ma). The rapid release of large quantities of carbon into the ocean-atmosphere system is believed to have triggered this intense episode of dissolution along with a negative carbon isotope excursion (CIE). The brevity (120-220 kyr) of the PETM reflects the rapid enhancement of negative feedback mechanisms within Earth's exogenic carbon cycle that served the dual function of buffering ocean pH and reducing atmospheric greenhouse gas levels. Detailed study of the PETM stratigraphy from Ocean Drilling Program Site 690 (Weddell Sea) reveals that the CIE recovery period, which postdates the CIE onset by ˜80 kyr, is represented by an expanded (˜2.5 m thick) interval containing a unique planktic foraminiferal assemblage strongly diluted by coccolithophore carbonate. Collectively, the micropaleontological and sedimentological changes preserved within the CIE recovery interval reflect a transient state when ocean-atmosphere chemistry fostered prolific coccolithophore blooms that suppressed the local lysocline to relatively deeper depths. A prominent peak in the abundance of the clay mineral kaolinite is associated with the CIE recovery interval, indicating that continental weathering/runoff intensified at this time as well (Robert and Kennett, 1994). Such parallel stratigraphic changes are generally consonant with the hypothesis that enhanced continental weathering/runoff and carbonate precipitation helped sequester carbon during the PETM recovery period (e.g., Dickens et al., 1997; Zachos et al., 2005).

  5. Carbon Balance Assessment of a Natural Steppe of Southern Siberia by Multiple Constraint Approach

    NASA Astrophysics Data System (ADS)

    Belelli, L.; Papale, D.; Reichstein, M.; Vuichard, N.; Tchebakova, N.; Valentini, R.

    2007-12-01

    Steppe ecosystems represent an interesting case in which the assessment of carbon balance may be performed through a cross validation of the eddy covariance measurements against ecological inventory estimates of carbon exchanges (Ehman et al., 2002; Curtis et al., 2002). Indeed, the widespread presence of ideal conditions for the applicability of the eddy covariance technique, as vast and homogeneous grass vegetation cover over flat terrains (Baldocchi, 2003), make steppes a suitable ground to ensure a constrain to flux estimates with independent methodological approaches. We report about the analysis of the carbon cycle of a true steppe ecosystem in southern Siberia during the growing season of 2004 in the framework of the TCOS-Siberia project activities performed by continuous monitoring of CO2 fluxes at ecosystem scale by the eddy covariance method, fortnightly samplings of phytomass, and ingrowth cores extractions for NPP assessment, and weekly measurements of heterotrophic component of soil CO2 effluxes obtained by an experiment of root exclusion. The carbon balance of the monitored natural steppe was, according to micrometeorological measurements, a sink of carbon of 151.7±36.9 gC m-2, cumulated during the growing season from May to September. This result was in agreement with the independent estimate through ecological inventory which yielded a sink of 150.1 gC m-2 although this method was characterized by a large uncertainty \\(±130%\\) considering the 95% confidence interval of the estimate. Uncertainties in belowground process estimates account for a large part of the error. Thus, in particular efforts to better quantify the dynamics of root biomass (growth and turnover) have to be undertaken in order to reduce the uncertainties in the assessment of NPP. This assessment should be preferably based on the application of multiple methods, each one characterized by its own merits and flaws.

  6. Response of the terrestrial carbon cycle to the El Niño-Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Qian, Haifeng; Joseph, Renu; Zeng, Ning

    2008-09-01

    Land plays a dominant role in the interannual variability of the global carbon cycle. The canonical warming and drying of the terrestrial tropics observed during El Niño events calls for the study of the role of precipitation and temperature on carbon cycle variability. Here we use a dynamic vegetation and terrestrial carbon model vegetation-global-atmosphere-soil (VEGAS) to investigate the response of terrestrial carbon cycle to El Niño-Southern Oscillation (ENSO) for the period 1980-2004. The simulated global total land-atmosphere flux (Fta) by VEGAS agrees well with the atmospheric CO2 inversion modelling results on ENSO timescales and is dominated by the tropics. Analysis of composites of terrestrial responses and climate factors during ENSO events and lead-lag correlations have identified that in the tropics, anomalous precipitation lags ENSO by 1 month and temperature by 5-6 months, while simulated soil moisture lags by 5 months. Warmer and drier conditions there cause suppression of Net Primary Production (NPP) and enhancement of Heteotrophic Respiration (Rh) simultaneously, resulting in the lagging of tropical Fta by 6 months. Sensitivity simulations reveal that 2/3 of Fta change comes from NPP and 1/3 from Rh. In VEGAS, fire burning accounts for about 25% of total Fta anomalies. Precipitation during ENSO events contributes 56% of variation of Fta; temperature accounts for 44%, which includes 25% from the enhancement of Rh and 7% from the increase of the vegetation respiration. We identify the remaining 12% variation of Fta to be from an indirect effect of temperature through its effect on soil wetness, which in turn affects NPP. Such insight into the direct and indirect effects of climatic factors highlights the critical role of soil moisture in ecosystem and carbon cycle-a poorly constrained factor.

  7. Lower Cretaceous carbon burial epidodes in the Gargano Promontory succession (southern Italy): geochemical and biotic response

    NASA Astrophysics Data System (ADS)

    Luciani, L.; Cobianchi, C.; Jenkyns, J.

    2003-04-01

    The Lower Cretaceous interval attracts increasingly attention by stratigraphers because of the occurrence of significant palaeoceanographic events, such as the widespread carbon burial within pelagic sediments. Some of these carbon-rich levels are related to global episodes of black-shale deposition and are interpreted as the sedimentary expression of productivity-driven Oceanic Anoxic Events (OAEs). The anoxic events caused perturbations of the global carbon budget, which in turn influenced oceanic chemistry and climate, and induced changes in the microfossil distribution. In the Lower Cretaceous pelagic succession of the Gargano Promontory, southern Italy, the equivalents of the Selli, Urbino and Amadeus levels, formally described in the Umbria-Marche Basin (Central Italy) and corresponding to the OAE1a, OAE1b and OAE 1c respectively, have been documented. An integrated micropaleontological (foraminifera, calcareous nannofossils) and geochemical (stable carbon- and oxygen-isotope) study has been carried out to improve understanding of the biotic response to, and palaeoceanographic implications of, anoxic events. The Aptian Selli Level equivalent correlates with the top of the interval of unchanging carbon-isotope values. The onset of the global "nannoconid crisis" is recorded and coincides with the beginning of the negative carbon-isotope excursion. The occurrence of an impoverished benthic foraminiferal fauna in the black shale documents dysaerobic rather than completely anoxic conditions on the sea floor, and there is no evidence for dramatically increased productivity. In line with evidence from elsewhere, bulk oxygen-isotope data suggest cooling immediately following the Selli Event. In the Albian interval of the Gargano Promontory, the carbon-isotope curve shows positive peaks succeeding negative trends, only partly corresponding to the pattern of global carbon burial documented elsewhere. The δ13C negative excursions related to the Albian black shales

  8. Seasonal variation in kangaroo tooth enamel oxygen and carbon isotopes in southern Australia

    NASA Astrophysics Data System (ADS)

    Brookman, Tom H.; Ambrose, Stanley H.

    2012-09-01

    Serial sampling of tooth enamel growth increments for carbon and oxygen isotopic analyses of Macropus (kangaroo) teeth was performed to assess the potential for reconstructing paleoseasonality. The carbon isotope composition of tooth enamel apatite carbonate reflects the proportional intake of C3 and C4 vegetation. The oxygen isotopic composition of enamel reflects that of ingested and metabolic water. Tooth enamel forms sequentially from the tip of the crown to the base, so dietary and environmental changes during the tooth's formation can be detected. δ13C and δ18O values were determined for a series of enamel samples drilled from the 3rd and 4th molars of kangaroos that were collected along a 900 km north-south transect in southern Australia. The serial sampling method did not yield pronounced seasonal isotopic variation patterns in Macropus enamel. The full extent of dietary isotopic variation may be obscured by attenuation of the isotopic signal during enamel mineralisation. Brachydont (low-crowned) Macropus teeth may be less sensitive to seasonal variation in isotopic composition due to time-averaging during mineralisation. However, geographic variations observed suggest that there may be potential for tracking latitudinal shifts in vegetation zones and seasonal environmental patterns in response to climate change.

  9. Carbonate platform evolution, Upper Paleozoic, southern Kazakhstan, USSR: A surface analog for the super giant Tengiz oil field western Kazakhstan

    SciTech Connect

    Cook, H.E. ); Gatosvseey, Y.A.; Ponoeearenko, S.B.; Styehtsyehnka, I.G.; Styehtsyennka, V.P.; Zoran, A.E. ); Zhemchuzhnikov, V. )

    1991-08-01

    The Upper Devonian and Carboniferous carbonate platform and associated bioherms in the Bolshoi Karatau Mountains of southern Kazakhstan are similar to coeval carbonate platform and biohermal reservoir facies recently described in the Tengiz oil field of western Kazakhstan on the southeastern margin of the Pre-Caspian basin. Like Tengiz, the Bolshoi Karatau carbonate platform developed upon Devonian siliciclastics. The size of the two platforms are also similar as both the Bolshoi Karatau and the Tengiz carbonate platform are about 2-4 km thick and about 100 km wide. In the Bolshoi Karatau Mountains, the carbonate platform trends northwest-southeast, with the continental land mass to the east, and the open ocean platform margin toward Tengiz. Within the Bolshoi Karatau carbonate platform are several types of bioherms and carbonate sand bodies that may be analogous to the reservoir facies in the Tengiz oil field. Some of these facies exhibit karsting and solution voids which probably developed during sea level fluctuation. The Bolshoi Karatau carbonate sequence provides new data on the stratigraphic and sedimentologic evolution of Upper Devonian and Carboniferous carbonate platforms in southern Kazakhstan. Depositional, diagenetic, and reservoir models of this outcrop belt that are currently being developed should be useful for making subsurface predictions in the Tengiz area and other stratigraphically similar areas of the Soviet Union.

  10. Bio-chemostratigraphy of the Barremian-Aptian shallow-water carbonates of the southern Apennines (Italy): pinpointing the OAE1a in a Tethyan carbonate platform

    NASA Astrophysics Data System (ADS)

    di Lucia, M.; Mutti, M.; Parente, M.

    2011-09-01

    Low resolution and lack of chronostratigraphic calibration of carbonate platform biostratigraphy hinder precise correlation with coeval deep-water successions. This is the main obstacle when studying the record of Mesozoic oceanic anoxic events in carbonate platforms. In this paper we use carbon isotope stratigraphy to produce the first chronostratigraphic calibration of the Barremian-Aptian biostratigraphy of the Apenninic carbonate platform of southern Italy. According to our calibration, the "Selli level" black shales of epicontinental and oceanic basins corresponds in the southern Apenninic carbonate platform to the interval between the "Orbitolina level", characterized by the association of Mesorbitolina parva and Mesorbitolina texana, and the second acme of Salpingoporella dinarica. The biocalcification crisis of nannoconids corresponds to the interval going from the first acme of S. dinarica to just above the top of the "Orbitolina level". Since these bioevents have been widely recognized beyond the Apenninic platform, our calibration can be used to pinpoint the interval corresponding to the Early Aptian oceanic anoxic event in other carbonate platforms of central and southern Tethys.

  11. Microbial utilization of litter carbon under the effect of extreme weather events

    NASA Astrophysics Data System (ADS)

    Heinrich, Steffen; Kuzyakov, Yakov; Glaser, Bruno

    2015-04-01

    Climate change is expected to not only lead to an increase of average annual temperature but also to increase the frequency of extreme meteorological events. For example, extreme summer-droughts followed by heavy rainfall events are likely to increase. This may change SOM quality, composition, microbial community functioning and thus C turnover in temperate forest ecosystems. Therefore, we performed a tracer experiment in the "Fichtelgebirge" (Northern Bavaria) to verify the influence of strong drying followed by intensive rewetting on the microbial community structure and decomposition of litter-derived 13C by individual microbial groups. In 2010, sheltered plots with artificially simulated drought, those with additional irrigation and control sites under natural conditions were established at a Norway spruce forest. At each plot, we added 13C enriched spruce litter to simulate annual litter fall. Thereafter, we assessed the effect of extreme weather events on microbial community structure by phospholipid fatty acid (PLFA) analysis. In addition, we analyzed the 13C incorporation into bulk soil, microbial biomass and PLFA of the organic horizon and the mineral soil up to 10 cm. Additionally respired CO2 was quantified by closed chambers. Drought reduced the microbial biomass only in the organic horizon, while in the mineral soil the microbial abundance did not decrease compared to the control and irrigated plots. The decrease in microbial biomass in the organic horizon of the drought plots resulted also in a strongly reduced incorporation of litter derived C: Incorporation of litter 13C was a magnitude of three lower in the drought plots compared to the control and irrigation plots. Furthermore, after the drought period of 90 days the proportion of 13C in CO2 from soil respiration was reduced by about 95% on the drought plots compared to the control and irrigated plots. This is in agreement with the reduced degradation of litter derived C and thus a reduced C

  12. Stable oxygen and carbon isotope characteristics in speleothems from Southern Africa - how good are they?

    NASA Astrophysics Data System (ADS)

    Holmgren, K.

    2009-04-01

    Much remains to be understood about the interaction between the African climate system, its surrounding ocean-atmosphere climate variability and the global climate system. A better understanding of the regional climate evolution is crucial for understanding global climate dynamics and issues surrounding environmental change throughout Africa and a prerequisite for increasing climate forecasting capabilities for the region. As part of developing this understanding, a longer term perspective that reaches beyond the information available from instrumental records is required. Speleothems are frequently abundant in southern Africa. Quite a few records are now available, reporting significant changes in climate and environmental conditions over longer and shorter time scales. Conclusions are mainly based on the stable isotopic composition of the speleothems. The interpretation of the stable isotope data is, however, not always straight-forward, since many processes contribute to the observed signal in the speleothem and these processes may influence the signal differently at different spatial and temporal scales. For example was the Makapansgat speleothem oxygen isotope record, originally interpreted as being generally determined by shifts in atmospheric circulation pattern (Lee-Thorp et al. 2001, Holmgren et al. 2003), recently challenged and re-interpreted by Partin et al. (2008) to reflect annual rainfall amounts. Historically, less attention has been paid to the stable carbon isotope composition in speleothems. Today, an increasing number of studies demonstrate the potential of stable carbon variations as providing additional information on climate and environment. Measured variations can be a function of the amount of C3 versus C4 vegetation, vegetation cover and soil biological activity, bedrock proportion, rainfall amount and the drip rate. Clearly the multitudes of plausible processes behind the isotopic composition of speleothems in southern Africa (as well as

  13. Secondary minerals of weathered orpiment-realgar-bearing tailings in Shimen carbonate-type realgar mine, Changde, Central China

    NASA Astrophysics Data System (ADS)

    Zhu, Xiangyu; Wang, Rucheng; Lu, Xiancai; Liu, Huan; Li, Juan; Ouyang, Bingjie; Lu, Jianjun

    2015-02-01

    The formation and dissolution of arsenic minerals commonly controls the mobility of As in sulfide mines. Here, we present the results of research based on X-ray powder diffraction (XRD), Raman microprobe spectrum, scanning electron microscope (SEM), and transmission electron microscope (TEM) analyses, Scanning transmission X-ray microscope (STXM) and X-ray absorption fine structure (XAFS) analyses to further understand the weathering of orpiment- and realgar-bearing tailings from the Shimen realgar deposit, the largest realgar deposit in Asia. These analyses indicate that four different types of As-bearing secondary minerals are present in the tailings, including arsenic oxides, arsenates, As-gypsum, and As-Fe minerals, and that arsenic in the tailings is present in +3 and +5 valence states. The precipitation of arsenates is attributed to the interaction between As-enriched run-off waters and carbonate minerals. The Ca-arsenates in the tailings are dominantly weilite and pharmacolite, both of which have Ca/As atomic ratios of 1. In addition, SO4 2-/HAsO4 2- substitution in gypsum is another important mechanism of arsenic precipitation.

  14. Carbon balance of a fertile forestry-drained peatland in southern Finland

    NASA Astrophysics Data System (ADS)

    Lohila, Annalea; Korkiakoski, Mika; Tuovinen, Juha-Pekka; Minkkinen, Kari; Penttilä, Timo; Ojanen, Paavo; Launiainen, Samuli; Laurila, Tuomas

    2016-04-01

    Forestry on peatlands is a significant land use form and has been economically important during the last decades particularly in the Nordic countries. While nutrient-poor forests are generally able to maintain their carbon sink status even after drainage, the peat soil at the fertile sites is typically considered as a large carbon dioxide (CO2) source. This means that despite of high timber production capacity, the fertile peatland forests gradually lose their peat carbon store. In addition, many of the nutrient-rich sites emit considerable amount of nitrous oxide (N2O) into the atmosphere. While the current estimates of the greenhouse gas (GHG) balance of forestry-drained peatlands are largely based on soil inventories or on data combining soil GHG fluxes and tree growth litter input measurements and modelling, only few studies have utilized the high-resolution, continuous eddy covariance (EC) data to address the short-term dynamics of the net CO2 fluxes covering both the soil, forest floor vegetation and the trees. Hence, little is known about the factors which control the year-to-year variation in fluxes. Here we present a 5-year dataset of CO2 fluxes measured with the EC method above a nutrient-rich forestry-drained peatland in southern Finland. The site, drained in the beginning of 1970's, is a well growing pine forest with some spruces and birches, the tree volume and carbon fixation rate equaling 8.0 kg C m-2 and 0.273 kg C m-2 yr-1, respectively. The average summer-time water level depth is -50 cm. By combining the gap-filled half-hourly net ecosystem exchange (NEE) data, the tree growth measurements, and the measurements on dissolved organic carbon (DOC) losses and soil methane (CH4) exchange, we will in this presentation estimate the total annual loss of peat carbon of this fertile peatland forest. In addition, using the N2O flux data we will estimate the contribution of different gases to the total GHG balance. Factors controlling the carbon balance and

  15. Meteorological Controls on Biomass Burning During Santa Ana Events in Southern California

    NASA Technical Reports Server (NTRS)

    Veraverbeke, Sander; Capps, Scott; Hook, Simon J.; Randerson, James T.; Jin, Yufang; Hall, Alex

    2013-01-01

    Fires occurring during Santa Ana (SA) events in southern California are driven by extreme fire weather characterized by high temperatures, low humidities, and high wind speeds. We studied the controls on burned area and carbon emissions during two intensive SA burning periods in 2003 and 2007. We therefore used remote sensing data in parallel with fire weather simulations of the Weather and Regional Forecast model. Total carbon emissions were approximately 1800 gigagrams in 2003 and 900 gigagrams in 2007, based on a daily burned area and a fire emission model that accounted for spatial variability in fuel loads and combustion completeness. On a regional scale, relatively strong positive correlations were found between the daily Fosberg fire weather index and burned area/emissions (probability is less than 0.01). Our analysis provides a quantitative assessment of relationships between fire activity and weather during severe SA fires in southern California.

  16. Meteorological Controls on Biomass Burning During Santa Ana Events in Southern California

    NASA Technical Reports Server (NTRS)

    Veraverbeke, Sander; Capps, Scott; Hook, Simon J.; Randerson, James T.; Jin, Yufang; Hall, Alex

    2013-01-01

    Fires occurring during Santa Ana (SA) events in southern California are driven by extreme fire weather characterized by high temperatures, low humidities, and high wind speeds. We studied the controls on burned area and carbon emissions during two intensive SA burning periods in 2003 and 2007. We therefore used remote sensing data in parallel with fire weather simulations of the Weather and Regional Forecast model. Total carbon emissions were approximately 1800 gigagrams in 2003 and 900 gigagrams in 2007, based on a daily burned area and a fire emission model that accounted for spatial variability in fuel loads and combustion completeness. On a regional scale, relatively strong positive correlations were found between the daily Fosberg fire weather index and burned area/emissions (probability is less than 0.01). Our analysis provides a quantitative assessment of relationships between fire activity and weather during severe SA fires in southern California.

  17. Magnetic fabric determined from ARM and IRM anisotropies in paleozoic carbonates, Southern Appalachian Basin

    NASA Astrophysics Data System (ADS)

    Lu, Gang; McCabe, Chad

    1993-06-01

    We have undertaken a comparative study of ARM and IRM anisotropies in Paleozoic carbonate rocks from the Nashville and Jessamine Domes in the Southern Appalachian Basin. The ARMA ellipsoids differ markedly from the IRMA ellipsoids. ARMA appears to reflect a predeformation magnetic fabric due to deposition and/or compaction with minimum axes near vertical and a weak lineation. Conversely, IRMA has minimum axes near horizontal and oriented NE-SW, which is compatible with a tectonic fabric due to Alleghanian deformation. Percent ARMA is consistently greater than IRMA. ARM was imparted at low alternating fields (30 mT), and thus ARMA may reflect the fabric residing in low and intermediate coercivity (coarse grained) magnetite. However, the IRM was imparted in saturating fields (300 mT) and appears to be dominated by the single domain fraction, which is believed to carry the observed Kiaman Superchron remagnetization.

  18. Using Dissolved Organic Carbon Isotopes for Groundwater Age Dating in Southern Nevada, USA

    NASA Astrophysics Data System (ADS)

    Thomas, James; Hershey, Ronald; Fereday, Wyatt

    2016-04-01

    Dissolved organic carbon (DOC) 14C offers a method to calculate groundwater ages that is more straightforward than dissolved inorganic carbon (DIC) 14C. To obtain corrected DIC 14C groundwater ages requires models that account for chemical and physical processes that affect both 13C and 14C. This is especially true in carbonate-rock aquifers where a fair amount of dissolution and precipitation of carbonate minerals can occur. A first important step in calculating 14C DOC groundwater ages is to determine the initial 14C DOC (A0) values of the groundwater recharge. For this study, recharge area groundwater samples of DOC 14C, collected from 14 different sites, were used to determine the recharge DOC 14C values. These values ranged from 96 to 120 percent modern carbon (pmc), with an average value of 106.2 pmc. These 14C A0 values support the use of a 100 pmc 14C A0 pre-bomb value to calculate DOC 14C groundwater ages for southern Nevada. Several conditions to successfully use DOC 14C to date groundwater need to be met. First, soluble organic carbon content of aquifers needs to be low, so that little DOC is added to the groundwater as it flows from recharge areas down gradient in an aquifer. For this study, volcanic and carbonate aquifer outcrop rocks showed that these rocks contained low soluble organic carbon. Second, it is important that the DOC does not change character down a flow path, which could indicate transformation of DOC along a flow path and/or addition of DOC to the groundwater. Although specific DOC compounds could not be identified for samples collected at four sites, all four groundwater sample spectra show the same general shape over the duration of the HPLC run indicating that the DOC compound composition of groundwater does not significantly change from up-gradient to down-gradient. Third, another factor that could greatly affect DOC 14C groundwater age calculations is matrix diffusion/adsorption of DOC 14C. Laboratory experiments showed that

  19. Does iron fertilization lead to rapid carbon export in the Southern Ocean?

    NASA Astrophysics Data System (ADS)

    Charette, Matthew A.; Buesseler, Ken O.

    2000-10-01

    The Southern Ocean has the potential to influence climate due to its large inventory of excess macronutrients such as nitrate and phosphate. It has been hypothesized that if the supply of the micronutrient iron increased, it would lead to enhanced uptake of atmospheric CO2 and hence the sequestration of carbon via sinking particles [Martin, 1990]. While much has been learned about iron limitation and low phytoplankton biomass in high-nutrient, low-chlorophyll regions [Martin, 1991; Coale et al., 1996], less is known about the effect of Fe on particle export. Here we present results from the first detailed study of particle export during a mesoscale iron fertilization experiment (the Southern Ocean Iron Release Experiment (SOIREE)). Measurements of the natural tracer thorium-234 indicate negligible particle export within 14 days after the initial infusion of iron. We attribute this lack of response to colder water temperatures that promote slower cell metabolism in phytoplankton and hence slower secondary responses of herbivores and particle aggregation.

  20. Soil Organic Carbon distribution in three contrasting olive orchards in Southern Spain

    NASA Astrophysics Data System (ADS)

    Taguas, Encarnación V.; Burguet, María; Guzmán, Gema; Pedrera-Parrila, Aura; Vanderlinden, Karl; Vanwalleghem, Tom; Pérez, Rafael; Ayuso, José L.; Gómez, José A.

    2013-04-01

    Soil organic carbon (SOC) shows a considerable spatial variability at the field, farm or catchment scales. This complicates its use as an indicator for soil quality, and is an important drawback for the efficient evaluation of carbon sequestration schemes, or for the certification of carbon sequestration potential of agricultural soils at these scales. This is especially significant for olive orchards in Mediterranean environments. We hypothesize that the typical row crop configuration of olive orchards, with cover crops or bare soil in the inter-row areas,can explain a vast proportion of this variability. In addition agricultural activities and topography-driven erosion processes at different scales contribute to SOC variability. Given the complexity of this problem and the important experimental effort required to address it, there are to our knowledgefew studies that have addressed this issue, specifically in agriculturalsoils under Mediterranean conditions. We present an analysis of SOC data obtained during 2011 and 2012 at three small (6-8 ha) catchmentsin Southern Spain, with contrasting soils (Vertisol, Luvisol and Cambisol) and covered by olive groves with different managements (conventional tillage, minimum tillage with mulch and non tillage with spontaneous grass cover). Soil organic carbon is analysed across tree rows, inter-row areas, and for different depths. The spatial SOC distribution is evaluated against the topography of the catchments and the intensity of the water erosion processes. The differences among the catchments are discussed and guidelines are provided for further exploring the sources of SOC variability and to improve SOC estimation at the field scale.

  1. Variability in carbon dioxide fluxes for dense urban, suburban and woodland environments in southern England

    NASA Astrophysics Data System (ADS)

    Ward, Helen; Kotthaus, Simone; Grimmond, C. Sue; Bjorkegren, Alex; Wilkinson, Matt; Morrison, Will; Evans, Jon; Morison, James; Christen, Andreas

    2014-05-01

    The net exchange of carbon dioxide between the surface and atmosphere can be measured using the eddy covariance technique. Fluxes from a dense urban environment (central London), a suburban landscape (Swindon) and a woodland ecosystem (Alice Holt) are compared. All sites are located in southern England and experience similar climatic and meteorological conditions, yet have very different land cover. The signatures of anthropogenic and biogenic processes are explored at various (daily, seasonal and annual) timescales. Particular emphasis is placed on identifying the mixture of controls that determine the flux. In summer, there are clear similarities between the suburban and woodland sites, as the diurnal behaviour is dominated by photosynthetic uptake. In winter, however, vegetation is largely dormant and human activity determines the pattern of fluxes at the urban and suburban sites. Emissions from building heating augment the net release of carbon dioxide in cold months. Road use is a major contributor to the total emissions, and the diurnal cycle in the observed fluxes reflects this: in central London roads are busy throughout the day, whereas in Swindon a double-peaked rush-hour signal is evident. The net exchange of carbon dioxide is estimated for each site and set in context with other studies around the world. Central London has the smallest proportion of vegetation and largest emissions amongst study sites in the literature to date. Although Swindon's appreciable vegetation fraction helps to offset the anthropogenic emissions, even in summertime the 24h total flux is usually positive, indicating carbon release. Comparison of these three sites in a similar region demonstrates the effects of increasing urban density and changing land use on the atmosphere. Findings are relevant in terms of characterising the behaviour of urban surfaces and for quantifying the impact of anthropogenic activities.

  2. Spread and establishment of Aedes albopictus in southern Switzerland between 2003 and 2014: an analysis of oviposition data and weather conditions.

    PubMed

    Flacio, Eleonora; Engeler, Lukas; Tonolla, Mauro; Müller, Pie

    2016-05-26

    The Asian tiger mosquito, Aedes albopictus, is a highly invasive mosquito species of public health importance. In the wake of its arrival in neighbouring Italy the authorities of the canton of Ticino in southern Switzerland initiated a surveillance programme in 2000 that is still on-going. Here we explored the unique data set, compiled from 2003 to 2014, to analyse the local dynamic of introduction and establishment of Ae. albopictus, its relative density in relation to precipitation and temperature, and its potential distribution at the passage from southern to northern Europe. The presence of Ae. albopictus was recorded by ovitraps placed across Ticino. In addition to presence-absence, the relationship between relative egg densities and year, month, temperature and precipitation was analysed by a generalised linear mixed model. Since its first detection in 2003 at Ticino's border with Italy Ae. albopictus has continuously spread north across the lower valleys, mainly along the trans-European motorway, E35. Detailed local analysis showed that industrial areas were colonised by the mosquito before residential areas and that, afterwards, the mosquito was more present in residential than in industrial areas. Ae. albopictus appeared sporadically and then became more present in the same places the following years, suggesting gradual establishment of locally reproducing populations that manage to overwinter. This trend continues as witnessed by both a growing area being infested and increasing egg counts in the ovitraps. There was a clear South-North gradient with more traps being repeatedly positive in the South and fewer eggs laid during periods of intensive precipitation. In the North, the mosquito appeared repeatedly through the years, but never managed to establish, probably because of unfavourable weather conditions and low road traffic. Given the present results we assume that additional areas may still become infested. While the current study provides good

  3. Century-Scale Responses of Ecosystem Carbon Storage and Flux to Multiple Environmental Changes in the Southern United States

    Treesearch

    Hanqin Tian; Guangsheng Chen; Chi Zhang; Mingliang Liu; Ge Sun; Arthur Chappelka; Wei Ren; Xiaofeng Xu; Chaoqun Lu; Shufen Pan; Hua Chen; Dafeng Hui; Steven McNulty; Graeme Lockaby; Eric Vance

    2012-01-01

    Terrestrial ecosystems in the southern United States (SUS) have experienced a complex set of changes in climate, atmospheric CO2 concentration, tropospheric ozone (O3), nitrogen (N) deposition, and land-use and land-cover change (LULCC) during the past century. Although each of these factors has received attention for its alterations on ecosystem carbon (C) dynamics,...

  4. Southern Ocean abyssal oxygenation linked to the air-sea partitioning of carbon throughout the last glacial cycle

    NASA Astrophysics Data System (ADS)

    Jaccard, S.; Galbraith, E. D.; Martinez-Garcia, A.; Anderson, R. F.

    2015-12-01

    Although no single mechanism can account for the full amplitude of past atmospheric CO2 variability over glacial interglacial cycles, a build-up of biologically-stored carbon in the deep ocean has emerged as a central mechanism for low CO2 during the Last Glacial Maximum (LGM). However, the mechanisms for which this deeply sequestered carbon was released, and the relative importance it played in the history of atmospheric CO2 prior to the LGM, remain subjects of debate. Here, we present new redox-sensitive trace metal records from the Antarctic Zone of the Southern Ocean that provide an unprecedented reconstruction of transient changes in deep ocean oxygenation and, by inference, respired carbon storage throughout the last glacial cycle. Our results show that respired carbon was removed from the abyssal Southern Ocean during the northern hemisphere cold phases of the deglaciation, when atmospheric CO2 rose rapidly, due to a combination of dwindling iron fertilization by dust and enhanced deep ocean ventilation. Furthermore, our new records show that the correlation between atmospheric CO2 and abyssal Southern Ocean oxygenation was maintained throughout most of the prior 80 kyrs, consistent with a unifying role of the Southern Ocean through a coupled control on deep ocean circulation and iron fertilization.

  5. Hemlock declines rapidly with hemlock woolly adelgid infestation: impacts on the carbon cycle of the Southern Appalachian forests

    Treesearch

    April E. Nuckolls; Nina Wurzburger; Chelcy R. Ford; Ronald L. Hendrick; James M. Vose; Brian D. Kloeppel

    2008-01-01

    The recent infestation of southern Appalachian eastern hemlock stands by hemlock woolly adelgid (HWA) is expected to have dramatic and lasting effects on forest structure and function. We studied the short-term changes to the carbon cycle in a mixed stand of hemlock and hardwoods, where hemlock was declining due to either girdling or HWA infestation. We expected that...

  6. Using stand replacement fires to restore southern Appalachian pine-hardwood ecosystems: effects on mass, carbon, and nutrient pools

    Treesearch

    James M. Vose; Wayne T. Swank; Barton D. Clinton; Jennifer D. Knoepp; Lloyd W. Swift

    1999-01-01

    Pine-hardwood ecosystems in the Southern Appalachians are in serious decline due to fire exclusion and insect infestations. Fire has been advanced as a tool to restore these ecosystems, yet there are few studies evaluating overall ecosystem effects. The authors’ objectives were to evaluate the effects of stand restoration burning on forest floor nitrogen (N) and carbon...

  7. Shifts in Aboveground and Forest Floor Carbon and Nitrogen Pools After Felling and Burning in the Southern Appalachians

    Treesearch

    Barton D. Clinton; James M. Vose; Wayne T. Swank

    1996-01-01

    Changes in aboveground and forest floor mass, carbon (C), and nitrogen (N) pools were quantified on three sites in the southern Appalachians 2 yr after felling and burning. Before felling and burning, stands were characterized by sparse overstories and dense Kalmia latifolia L. understories. Two years after burning, foliar C and N pools had reached 25% and 29% of...

  8. Synoptic weather patterns associated with carbon dioxide levels in Northern Spain.

    PubMed

    García, M Angeles; Sánchez, M Luisa; Pérez, Isidro A

    2010-07-15

    Measurements of atmospheric carbon dioxide, CO(2), were continuously carried out in the upper Spanish plateau over a three-year campaign, 2003-2005. Temporal CO(2) variations were examined. The results allow identification of the average data representative of background conditions, 382.9 ppm, with values ranging from 346.2 to 502.5 ppm. The weekly cycle evidences a difference of 0.2 ppm between weekday and weekend residuals, with levels increasing during the week. Seasonal variation in monthly means was inferred, the largest peak in appearing in spring, about 388 ppm. High values were also recorded in autumn, particularly in 2005 with an additional 5 ppm. By contrast, minimum values were obtained in July, between 374 and 379 ppm. A link between CO(2) concentrations and meteorological variables is explored. Analysis of surface wind speed intervals shows that low winds are the most frequent and are linked to the highest concentrations, around 395 ppm at night and in spring. CO(2) concentrations drop significantly for the 3.1-5.3 ms(-1) interval from which steady levels, around 378 ppm except in autumn, were observed. If different temperature intervals are considered, the 10-15 degrees C interval establishes the boundary between the extreme mean CO(2) levels, except for winter, 5-10 degrees C. The mean associated values ranged between 376.0 and 390.4 ppm, with a greater contrast in spring, 12.8 ppm. Finally, the relation between synoptic-scale atmospheric transport patterns and maximum CO(2) concentrations was also examined. The highest values occur in spring with some quite frequent synoptic situations: continental ridges, troughs to the west, interactions of the two and Atlantic ridges. Copyright 2010 Elsevier B.V. All rights reserved.

  9. Weather Watch

    ERIC Educational Resources Information Center

    Bratt, Herschell Marvin

    1973-01-01

    Suggests a number of ways in which Federal Aviation Agency weather report printouts can be used in teaching the weather section of meteorology. These weather sequence reports can be obtained free of charge at most major airports. (JR)

  10. Weather Watch

    ERIC Educational Resources Information Center

    Bratt, Herschell Marvin

    1973-01-01

    Suggests a number of ways in which Federal Aviation Agency weather report printouts can be used in teaching the weather section of meteorology. These weather sequence reports can be obtained free of charge at most major airports. (JR)

  11. Multiyear Climate Variability and Dengue—El Niño Southern Oscillation, Weather, and Dengue Incidence in Puerto Rico, Mexico, and Thailand: A Longitudinal Data Analysis

    PubMed Central

    Johansson, Michael A.; Cummings, Derek A. T.; Glass, Gregory E.

    2009-01-01

    Background The mosquito-borne dengue viruses are a major public health problem throughout the tropical and subtropical regions of the world. Changes in temperature and precipitation have well-defined roles in the transmission cycle and may thus play a role in changing incidence levels. The El Niño Southern Oscillation (ENSO) is a multiyear climate driver of local temperature and precipitation worldwide. Previous studies have reported varying degrees of association between ENSO and dengue incidence. Methods and Findings We analyzed the relationship between ENSO, local weather, and dengue incidence in Puerto Rico, Mexico, and Thailand using wavelet analysis to identify time- and frequency-specific association. In Puerto Rico, ENSO was transiently associated with temperature and dengue incidence on multiyear scales. However, only local precipitation and not temperature was associated with dengue on multiyear scales. In Thailand, ENSO was associated with both temperature and precipitation. Although precipitation was associated with dengue incidence, the association was nonstationary and likely spurious. In Mexico, no association between any of the variables was observed on the multiyear scale. Conclusions The evidence for a relationship between ENSO, climate, and dengue incidence presented here is weak. While multiyear climate variability may play a role in endemic interannual dengue dynamics, we did not find evidence of a strong, consistent relationship in any of the study areas. The role of ENSO may be obscured by local climate heterogeneity, insufficient data, randomly coincident outbreaks, and other, potentially stronger, intrinsic factors regulating transmission dynamics. Please see later in the article for the Editors' Summary PMID:19918363

  12. A Climatology of Fair-Weather Cloud Statistics at the Atmospheric Radiation Measurement Program Southern Great Plains Site: Temporal and Spatial Variability

    SciTech Connect

    Berg, Larry K.; Kassianov, Evgueni I.; Long, Charles N.; Gustafson, William I.

    2006-03-30

    In previous work, Berg and Stull (2005) developed a new parameterization for Fair-Weather Cumuli (FWC). Preliminary testing of the new scheme used data collected during a field experiment conducted during the summer of 1996. This campaign included a few research flights conducted over three locations within the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) Southern Great Plains (SGP) site. A more comprehensive verification of the new scheme requires a detailed climatology of FWC. Several cloud climatologies have been completed for the ACRF SGP, but these efforts have focused on either broad categories of clouds grouped by height and season (e.g., Lazarus et al. 1999) or height and time of day (e.g., Dong et al. 2005). In these two examples, the low clouds were not separated by the type of cloud, either stratiform or cumuliform, nor were the horizontal chord length (the length of the cloud slice that passed directly overhead) or cloud aspect ratio (defined as the ratio of the cloud thickness to the cloud chord length) reported. Lane et al. (2002) presented distributions of cloud chord length, but only for one year. The work presented here addresses these shortcomings by looking explicitly at cases with FWC over five summers. Specifically, we will address the following questions: •Does the cloud fraction (CF), cloud-base height (CBH), and cloud-top height (CTH) of FWC change with the time of day or the year? •What is the distribution of FWC chord lengths? •Is there a relationship between the cloud chord length and the cloud thickness?

  13. Methane-derived authigenic carbonates of mid-Cretaceous age in southern Tibet: Types of carbonate concretions, carbon sources, and formation processes

    NASA Astrophysics Data System (ADS)

    Liang, Huimin; Chen, Xi; Wang, Chengshan; Zhao, Dekun; Weissert, Helmut

    2016-01-01

    Methane-derived authigenic carbonates with distinctive structures and morphologies have been documented worldwide, but they are rarely found from ancient strata in the Eastern Tethys Ocean. The methane-derived authigenic carbonates found in southern Tibet are developed in calcareous or silty shales of mid-Cretaceous age in the Xigaze forearc basin and in the Tethyan Himalaya tectonic zone. The morphology, mineralogy, elemental geochemistry and composition of carbon and oxygen isotopes of these carbonates are studied in detail. The carbonates have nodular, tubular, and tabular morphologies. They are primarily composed of carbonate cement that binds and partly replaces host sediment grains; host siliciclastic sediments are composed mainly of quartz and plagioclase feldspar; a few foraminifers; and framboidal or subhedral to euhedral pyrite. Carbonate cements dominantly are micritic calcite, with minor contribution of dolomite. Nodular concretions are characterized by depleted δ13C values, commonly ranging from -30‰ to -5‰. The δ13C values show a gradual decrease from the periphery to the center, and the CaO, SiO2, Fe2O3, Al2O3, K2O, and TiO2 contents generally show a gradual change. These features indicate that the nodular concretions grew from an early-formed center toward the periphery, and that the carbon source of the nodular concretions was derived from a mixture of methane, methanogenic CO2, and seawater-dissolved inorganic carbon. The tubular concretions are characterized by δ13C values of -8.85‰ to -3.47‰ in the Shangba Section, and -27.37‰ to -23.85‰ in the upper Gamba Section. Unlike the nodular concretions, the tubular concretions show central conduits, which are possible pathways of methane-rich fluids, suggesting that the cementation of tubular concretions begins at the periphery and proceeds inward. Moreover, the tubular concretions show morphological similarity with the methane-derived carbonate chimneys, pipes and slabs reported in

  14. Implications of weather-induced tree mortality on forest carbon dynamics based on remeasured forest inventory plots in the Eastern United States

    NASA Astrophysics Data System (ADS)

    Di Vittorio, A. V.; Chambers, J. Q.

    2011-12-01

    Forest tree mortality plays an important role in the global carbon budget through so-called 'background' mortality rates and larger, less frequent mortality events. The actual mortality turnover rates of forest biomass are not well understood and can vary with forest type, stand characteristics, and environmental conditions. Different agents, such as fire, insects, disease, and weather, operate on different time scales and have different effects on ecosystems. These differences make it difficult, but important, to determine a continuum of return frequencies for agent-specific mortality, especially when making projections of forest carbon balance. Some regional and global ecosystem models include a separate fire component to account for burn emissions, but events such as hurricanes can also influence carbon dynamics and are not simulated. Thus, the effects of potential changes in hurricane frequency and intensity over time would not be captured by existing models. Furthermore, many regional and global ecosystem models assume a single, non-fire mortality rate for all forests, which likely introduces bias to projections of forest carbon balance. Using the United States Forest Service (USFS) Forest Inventory Analysis DataBase (FIADB) we estimated historic (~1970 - 2010) mortality rates for Eastern United States forests. We present spatially-explicit estimates of total mortality and of agent-specific mortality due to insects, disease, fire, weather, and harvest. These estimates show that uniform mortality rates in ecosystem models might be improved if varied spatially. The relative contribution of weather-induced mortality indicates that it results from smaller, more frequent events in addition to the effects of more extreme events such as hurricanes. Evidence of relatively high, hurricane-induced mortality suggests that the effects of extreme weather events should be explicitly modeled.

  15. Dissolved Organic Carbon 14C in Southern Nevada Groundwater and Implications for Groundwater Travel Times

    SciTech Connect

    Hershey, Ronald L.; Fereday, Wyall; Thomas, James M

    2016-08-01

    Dissolved inorganic carbon (DIC) carbon-14 (14C) ages must be corrected for complex chemical and physical reactions and processes that change the amount of 14C in groundwater as it flows from recharge to downgradient areas. Because of these reactions, DIC 14C can produce unrealistically old ages and long groundwater travel times that may, or may not, agree with travel times estimated by other methods. Dissolved organic carbon (DOC) 14C ages are often younger than DIC 14C ages because there are few chemical reactions or physical processes that change the amount of DOC 14C in groundwater. However, there are several issues that create uncertainty in DOC 14C groundwater ages including limited knowledge of the initial (A0) DOC 14C in groundwater recharge and potential changes in DOC composition as water moves through an aquifer. This study examines these issues by quantifying A0 DOC 14C in recharge areas of southern Nevada groundwater flow systems and by evaluating changes in DOC composition as water flows from recharge areas to downgradient areas. The effect of these processes on DOC 14C groundwater ages is evaluated and DOC and DIC 14C ages are then compared along several southern Nevada groundwater flow paths. Twenty-seven groundwater samples were collected from springs and wells in southern Nevada in upgradient, midgradient, and downgradient locations. DOC 14C for upgradient samples ranged from 96 to 120 percent modern carbon (pmc) with an average of 106 pmc, verifying modern DOC 14C ages in recharge areas, which decreases uncertainty in DOC 14C A0 values, groundwater ages, and travel times. The HPLC spectra of groundwater along a flow path in the Spring Mountains show the same general pattern indicating that the DOC compound composition does not change along this flow path

  16. Stages of weathering mantle formation from carbonate rocks in the light of rare earth elements (REE) and Sr-Nd-Pb isotopes

    NASA Astrophysics Data System (ADS)

    Hissler, Christophe; Stille, Peter

    2015-04-01

    Weathering mantles are widespread and include lateritic, sandy and kaolinite-rich saprolites and residuals of partially dissolved rocks. These old regolith systems have a complex history of formation and may present a polycyclic evolution due to successive geological and pedogenetic processes that affected the profile. Until now, only few studies highlighted the unusual high content of associated trace elements in weathering mantles originating from carbonate rocks, which have been poorly studied, compared to those developing on magmatic bedrocks. For instance, these enrichments can be up to five times the content of the underlying carbonate rocks. However, these studies also showed that the carbonate bedrock content only partially explains the soil enrichment for all the considered major and trace elements. Up to now, neither soil, nor saprolite formation has to our knowledge been geochemically elucidated. Therefore, the aim of this study was to examine more closely the soil forming dynamics and the relationship of the chemical soil composition to potential sources. REE distribution patterns and Sr-Nd-Pb isotope ratios have been used because they are particularly well suited to identify trace element migration, to recognize origin and mixing processes and, in addition, to decipher possible anthropogenic and/or "natural" atmosphere-derived contributions to the soil. Moreover, leaching experiments have been applied to identify mobile phases in the soil system and to yield information on the stability of trace elements and especially on their behaviour in these Fe-enriched carbonate systems. All these geochemical informations indicate that the cambisol developing on such a typical weathering mantle ("terra fusca") has been formed through weathering of a condensed Bajocian limestone-marl facies. This facies shows compared to average world carbonates important trace element enrichments. Their trace element distribution patterns are similar to those of the soil

  17. Use of molecular approaches in hydrogeological studies: the case of carbonate aquifers in southern Italy

    NASA Astrophysics Data System (ADS)

    Bucci, Antonio; Petrella, Emma; Celico, Fulvio; Naclerio, Gino

    2017-06-01

    Waterborne pathogens represent a significant health risk in both developed and developing countries with sensitive sub-populations including children, the elderly, neonates, and immune-compromised people, who are particularly susceptible to enteric infections. Annually, approximately 1.8 billion people utilize a faecally contaminated water source, and waterborne diseases are resulting in up to 2.1 million human mortalities globally. Although groundwater has traditionally been considered less susceptible to contamination by enteric pathogens than surface water due to natural attenuation by overlying strata, the degree of microbial removal attributable to soils and aquifers can vary significantly depending on several factors. Thus, accurate assessment of the variable presence and concentration of microbial contaminants, and the relative importance of potentially causative factors affecting contaminant ingress, is critical in order to develop effective source (well) and resource (aquifer) protection strategies. "Traditional" and molecular microbiological study designs, when coupled with hydrogeological, hydrochemical, isotopic, and geophysical methods, have proven useful for analysis of numerous aspects of subsurface microbial dynamics. Accordingly, this overview paper presents the principal microbial techniques currently being employed (1) to predict and identify sources of faecal contamination in groundwater, (2) to elucidate the dynamics of contaminant migration, and (3) to refine knowledge about the hydrogeological characteristics and behaviours of aquifer systems affected by microbial contamination with an emphasis on carbonate aquifers, which represent an important global water supply. Previous investigations carried out in carbonate aquifers in southern Italy are discussed.

  18. Carbon stocks of an old-growth forest and an anthropogenic peatland in southern Chile

    NASA Astrophysics Data System (ADS)

    Perez-Quezada, Jorge; Brito, Carla; Cabezas, Julian; Salvo, Patricia; Lemunao, Pedro; Flores, Ernesto; Valdés, Ariel; Fuentes, Juan Pablo; Galleguillos, Mauricio; Pérez, Cecilia

    2015-04-01

    The distribution of carbon in the different ecosystem stocks may change with direct human perturbation or climate change. We present a detailed description of the carbon stocks of an old-growth forest and an anthropogenic peatland (i.e., created by flooding, as a consequence of forest fires or logging). The study area was located in a private reserve in the Chiloé Island, southern Chile (41° 52' S, 73° 40' W). Sampling was done on plots separated 60 m from each other, in areas of approximately 30 ha for each ecosystem type. Total C was 1523 ± 117 Mg ha-1 in the forest and 130 ± 13.8 Mg ha-1 in the peatland, with 69.7% and 91.7% of this found belowground, respectively. In the forest, the necromass stock composed by logs and snags was high (183 Mg C ha-1), compared with the live-tree stock (264 Mg C ha-1) and with the C stored in the understory vegetation (14 Mg C ha-1). In the peatland, most of the C was stored in the most decomposed layer of peat, deeper in the ground. Because the anthropogenic peatland is experiencing a secondary succession, there is great potential to sequester back the C lost due to the perturbation. However, in most of the area where these ecosystems are found, the moss is being harvested for horticultural purposes.

  19. Carbon isotope stratigraphy of Lochkovian to Eifelian limestones from the Devonian of central and southern Europe

    NASA Astrophysics Data System (ADS)

    Buggisch, Werner; Mann, Ulrich

    2004-09-01

    Lower to Middle Devonian carbonates of the Prague Syncline, the Carnic Alps, the Montagne Noire, and the Cantabrian Mountains were investigated for δ13Ccarb and δ13Corg. These values were measured on bulk rocks, selected components and cements. Many carbonates exhibit primary marine values, but some are altered by diagenesis. A δ13C curve can be presented for the latest Pridolian to Emsian time interval. Several sharp or broad positive excursions are obvious in the woschmidti-postwoschmidti, sulcatus, kitabicus, Late serotinus, and kockelianus conodont zones. The excursion at the Silurian Devonian boundary is known worldwide and therefore considered global in nature. Some of the others are described for the first time from central and southern Europe, and their global nature has to be verified by further investigations in other regions. Most excursions relate to and/or started during major regressions whereas sea-level highstands correspond to minimal δ13C values. Similar relationships between sea-level changes and δ13C have been observed from other early Palaeozoic intervals. The transgressive Choteč (?) and Kačák events are marked by positive isotope excursions, this type of combination is usually observed in late Palaeozoic to Cenozoic black shale events.

  20. Black Carbon Aerosols in the Marine Boundary Layer on the West Coast of Southern Africa

    NASA Astrophysics Data System (ADS)

    Piketh, S.; Formenti, P.; Namwoonde, A.; Feron, A.; Gaimoz, C.; Cazaunau, M.; Hanghome, M.; Broccardo, S. P.; Walton, N.; Klopper, D.; Burger, R.; Desboeufs, K. V.; Siour, G.; Junkermann, W.; Maenhaut, W.

    2016-12-01

    Continuous measurements, since 2012, at the Henties Bay Aerosol Observatory (HBAO; 22°S, 14°05'E), Namibia, show that, during the austral wintertime, transport of black carbon aerosols occurs at low-level into the marine boundary layer towards the South East Atlantic coast. This is ahead of the dry season peak for southern Africa (August to October), when biomass burning aerosols outflow into the free troposphere above the stratocumulus clouds. The concentration of black carbon equivalent associated with this low-level transport is of the order of 100-150 ng m-3. Assuming that they are related to biomass burning, a particle mass concentration of 5-7 µg m-3 and to a number concentration of 300-400 cm-3 is estimated. These values are sufficiently high to enable them, by entrainment, to cause an almost doubling of the cloud optical depth as well as an increase of approximately 40% in cloud reflectivity with respect to pristine conditions. Their direct radiative effect is negligible.

  1. Characterizing englacial and subglacial weathering processes in a silicate-carbonate system at Robertson Glacier, Canada: Combining field measurements and remote sensing

    NASA Astrophysics Data System (ADS)

    Rutledge, A. M.; Christensen, P. R.

    2012-12-01

    Geologic weathering processes in cold environments, especially processes acting on subglacial and englacial sediments and rocks, are not well characterized due to the difficulty of accessing these environments. However, subglacial and englacial weathering of geologic materials contributes to the solute flux in meltwater and provides a potential source of energy to chemotrophic microbes, and is thus an important component to understand. In this study, we characterize the weathering products present in a glaciated silicate-carbonate system using infrared spectroscopy, x-ray diffraction, and geochemical analyses. We use Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data to determine whether glacial weathering products can be detected from remotely detected infrared spectra. The major goals of the project are to quantify weathering inputs to the glacial energy budget, and to link in situ sampling with remote sensing capabilities. Robertson Glacier, Alberta, Canada (115°20'W, 50°44'N) provides an excellent field site for this technique as it is accessible, and its retreating stage allows sampling of fresh subglacial and englacial sediments. This site is also of great significance to microbiology studies due to the recent detection of methanogens in the local subglacial till. Samples of glacially altered rock and sediments were collected on a downstream transect of the glacier in September 2011. Infrared laboratory spectroscopy and x-ray diffraction were used to determine the composition and abundance of minerals present. Infrared imagery of the region was collected at the time of sampling with the ASTER satellite instrument. Geochemical data were also collected at each location, and ice and water samples were analyzed for major and minor elements. pH values decreased in the downstream direction, and Ca+2 and SO4-2 in solution increased downstream. This is initially consistent with earlier studies of similar systems; however, the majority of

  2. Emplacement of the Jurassic Mirdita ophiolites (southern Albania): evidence from associated clastic and carbonate sediments

    NASA Astrophysics Data System (ADS)

    Robertson, Alastair H. F.; Ionescu, Corina; Hoeck, Volker; Koller, Friedrich; Onuzi, Kujtim; Bucur, Ioan I.; Ghega, Dashamir

    2012-09-01

    Sedimentology can shed light on the emplacement of oceanic lithosphere (i.e. ophiolites) onto continental crust and post-emplacement settings. An example chosen here is the well-exposed Jurassic Mirdita ophiolite in southern Albania. Successions studied in five different ophiolitic massifs (Voskopoja, Luniku, Shpati, Rehove and Morava) document variable depositional processes and palaeoenvironments in the light of evidence from comparable settings elsewhere (e.g. N Albania; N Greece). Ophiolitic extrusive rocks (pillow basalts and lava breccias) locally retain an intact cover of oceanic radiolarian chert (in the Shpati massif). Elsewhere, ophiolite-derived clastics typically overlie basaltic extrusives or ultramafic rocks directly. The oldest dated sediments are calpionellid- and ammonite-bearing pelagic carbonates of latest (?) Jurassic-Berrasian age. Similar calpionellid limestones elsewhere (N Albania; N Greece) post-date the regional ophiolite emplacement. At one locality in S Albania (Voskopoja), calpionellid limestones are gradationally underlain by thick ophiolite-derived breccias (containing both ultramafic and mafic clasts) that were derived by mass wasting of subaqueous fault scarps during or soon after the latest stages of ophiolite emplacement. An intercalation of serpentinite-rich debris flows at this locality is indicative of mobilisation of hydrated oceanic ultramafic rocks. Some of the ophiolite-derived conglomerates (e.g. Shpati massif) include well-rounded serpentinite and basalt clasts suggestive of a high-energy, shallow-water origin. The Berriasian pelagic limestones (at Voskopoja) experienced reworking and slumping probably related to shallowing and a switch to neritic deposition. Mixed ophiolite-derived clastic and neritic carbonate sediments accumulated later, during the Early Cretaceous (mainly Barremian-Aptian) in variable deltaic, lagoonal and shallow-marine settings. These sediments were influenced by local tectonics or eustatic sea

  3. Simulating natural carbon sequestration in the Southern Ocean: on uncertainties associated with eddy parameterizations and iron deposition

    NASA Astrophysics Data System (ADS)

    Dietze, Heiner; Getzlaff, Julia; Löptien, Ulrike

    2017-03-01

    The Southern Ocean is a major sink for anthropogenic carbon. Yet, there is no quantitative consensus about how this sink will change when surface winds increase (as they are anticipated to do). Among the tools employed to quantify carbon uptake are global coupled ocean-circulation-biogeochemical models. Because of computational limitations these models still fail to resolve potentially important spatial scales. Instead, processes on these scales are parameterized. There is concern that deficiencies in these so-called eddy parameterizations might imprint incorrect sensitivities of projected oceanic carbon uptake. Here, we compare natural carbon uptake in the Southern Ocean simulated with contemporary eddy parameterizations. We find that very differing parameterizations yield surprisingly similar oceanic carbon in response to strengthening winds. In contrast, we find (in an additional simulation) that the carbon uptake does differ substantially when the supply of bioavailable iron is altered within its envelope of uncertainty. We conclude that a more comprehensive understanding of bioavailable iron dynamics will substantially reduce the uncertainty of model-based projections of oceanic carbon uptake.

  4. Pronounced changes in carbonate system and temperature history of the Southern California margin from LGM to present

    NASA Astrophysics Data System (ADS)

    Quintana Krupinski, N. B.; Pak, D. K.; Hill, T. M.; Paytan, A.

    2012-12-01

    Millennial-scale records of the marine carbonate system and its natural variability provide long-term perspective on anthropogenically-induced ocean acidification, and provide a basis for determining whether there is a critical threshold at which organisms may be negatively affected by changing carbonate saturation and pH. The state, stability and natural variability of pre-anthropogenic marine carbonate systems can be reconstructed from carbonate system proxies in foraminiferal calcite. Using newly calibrated proxies, we quantify the long-term history and variability of the surface water carbonate system in the Southern California Borderland, a coastal region that experiences substantial pH fluctuations today. Our reconstruction of temperature also allows comparison with other nearby Southern California temperature reconstructions. We present trace metal (B/Ca, U/Ca and Mg/Ca), stable isotope (δ18O , δ13C ) and shell weight results from the planktonic foraminifera G. bulloides and N. incompta (N. pachyderma (d)) from Santa Monica Basin (SMB; ODP 1015) to reconstruct the past surface ocean carbonate system and temperature for the past ~32ka. We observe a gradual decrease in B/Ca in the thermocline-dwelling N. incompta from 20ka to ~12ka, likely reflecting the decrease in global ocean pH and [CO32-] during deglaciation. Changes in temperature and ocean carbonate chemistry can be observed during the Younger Dryas and Bolling-Allerod in trace metal, stable isotope and shell weight records. Compared with other nearby Southern California ODP sites, temperatures from Mg/Ca during deglaciation in SMB are cooler by ~1-3 degrees, and show a larger temperature difference between G. bulloides and N. incompta during glacial time than other regional sites. These results strengthen evidence that the southern California Borderland shows a strong atmospheric teleconnection to North Atlantic climate changes, and also provide the opportunity to assess what aspects of southern

  5. [Soil organic carbon and nitrogen mineralization along a forest successional gradient in Southern China].

    PubMed

    Ouyang, Xue-Jun; Zhou, Guo-Yi; Wei, Shi-Guang; Huang, Zhong-Liang; Li, Jiong; Zhang, De-Qiang

    2007-08-01

    With incubation test, this paper studied the characteristics of organic C and N mineralization in 0-10 cm soil layer under three forest types, i. e., pine (Pinus massoniana) forest (PMF), pine and broad-leaved mixed forest (PBMF) and monsoon evergreen broad-leaved forest (MEBF), which were in a successional series in Dinghushan Mountain of Southern China. The results showed that after incubation for 52 weeks, the cumulative emission of CO2-C from PMF, PBMF and MEBF soil was 30.66 +/- 3.36, 58.17 +/- 7.25 and 59.31 +/- 13.58 mg x kg(-1), respectively, and 64.12%, 64.41% and 65.12% of which were released in the first 9 weeks. The cumulative emission of CO2-C was always significantly smaller from PMF soil than from PBMF and MEBF soils, and its change pattern over time fitted well with a two-pool kinetic model. The parameters based on the model implicated that the mineralization rates of soil labile and recalcitrant organic carbon tended to decrease with the forest type changing from PMF to PBMF and MEBF. The cumulative amount of CH4 after 52 weeks incubation and the net production of available N and nitrate after 20 weeks incubation were significantly higher in MEBF soil than in PBMF soil, and also, in PBMF soil than in PMF soil. NO3(-) -N was the dominant form in net available N production. The change in soil organic carbon mineralization rate caused by forest type change was an inherent way to affect soil organic carbon content.

  6. Photosynthetically active radiation and carbon gain drives the southern orientation of Myrtillocactus geometrizans fruits.

    PubMed

    Ponce-Bautista, A; Valverde, P L; Flores, J; Zavala-Hurtado, A; Vite, F; López-Ortega, G; Pérez-Hernández, M A

    2017-03-01

    The equatorial orientation of reproductive structures is known in some columnar cacti from extratropical deserts. It has been hypothesised that photosynthetically active radiation (PAR) interception is the main reason for this orientation, because of its key effect on nocturnal CO2 uptake. However, there are no studies addressing both the effect of PAR and its consequence, carbon gain, on fruit orientation. Accordingly, we tested whether PAR and carbon gain could explain the southern fruit orientation of Myrtillocactus geometrizans, an inter-tropical columnar cactus. We studied three populations of M. geometrizans in Mexico. For each population, azimuth of fruits, total daily PAR, nocturnal acid accumulation (NAA) and fruit production were measured. The relationships between rib orientation and number of fruits, as well as total daily PAR, were evaluated using periodic regressions. The effect of total daily PAR and NAA on number of fruits was assessed using generalised linear models. During spring, mean fruit orientation had a south azimuth for three populations. Likewise, rib orientation had a significant effect on fruit production, with the south-facing ribs having the maximum number of fruits. Total daily PAR was highest in the south-facing ribs, at least for those in the northern and central populations. Furthermore, during spring, there was a significant positive effect of total daily PAR and NAA on fruit production. Our results provide strong evidence that the higher carbon gain in equatorial ribs, through a highest interception of PAR, would be the responsible factor for equatorial orientation of fruits in an inter-tropical columnar cactus.

  7. The contribution of zooplankton faecal pellets to deep carbon transport in the Scotia Sea (Southern Ocean)

    NASA Astrophysics Data System (ADS)

    Manno, C.; Stowasser, G.; Enderlein, P.; Fielding, S.; Tarling, G. A.

    2014-11-01

    The northern Scotia Sea contains the largest seasonal uptake of atmospheric carbon dioxide yet measured in the Southern Ocean. This study examines one of the main routes by which this carbon fluxes to the deep ocean, through the production of faecal pellets (FPs) by the zooplankton community. Deep sediment traps were deployed in two sites with contrasting ocean productivity regimes (P3, naturally iron-fertilized and P2, iron-limited), within the same water mass. The magnitude and seasonal pattern of particulate organic carbon (POC) and FPs in the traps was markedly different between the two sites. Maximum fluxes at P3 (22.91 mg C m-2 d-1; 2534 × 10 FP m-2 d-1) were an order of magnitude higher than at P2 (4.01 mg C m-2 d-1; 915 × 10 FP m-2 d-1), with flux at P3 exhibiting a double seasonal peak, compared to a single flatter peak at P2. The maximum contribution of FP carbon to the total amount of POC was twice as high at P3 (91%) compared to P2 (40%). The dominant FP category at P3 varied between round, ovoidal, cylindrical and tabular over the course of the year while, at P2, ovoidal FPs were consistently dominant, always making up more than 60% of the FP assemblage. There was also a difference in the FP state between the two sites, with FPs being relatively intact at P3, while FPs were often fragmented with broken peritrophic membranes at P2. The exception was ovoidal FPs, which were relatively intact at both sites. Our observations suggest that there was community shift from an herbivorous to an omnivorous diet from spring through to autumn at P3 while detritivores had a higher relative importance over the year at P2. Furthermore, the flux was mainly a product of the vertically migrating zooplankton community at P3 while the FP flux was more likely to be generated by deeper-dwelling zooplankton feeding on recycled material at P2. The results demonstrate that the feeding behavior and vertical distribution of the zooplankton community plays a critical role in

  8. Impact of switchgrass biochars with supplemental nitrogen on carbon-nitrogen mineralization in highly weathered Coastal Plain Ultisols.

    PubMed

    Sigua, G C; Novak, J M; Watts, D W; Szögi, A A; Shumaker, P D

    2016-02-01

    Although an increase in soil fertility is the most frequently reported benefit linked to adding biochar to soils, there is still a need to pursue additional research that will improve our understanding on the impact of soil fertility enhancement because the effect could vary greatly between switchgrass (Panicum virgatum, L) residues (USG) and switchgrass biochars (SG). We hypothesized that SG with supplemental nitrogen (N) would deliver more positive effects on carbon (C) and N mineralization than USG. The objective of this study was to evaluate the effects of USG and SG, with or without supplemental inorganic N fertilizer on C and N mineralization in highly weathered Coastal Plain Ultisols. The application rate for SG and USG based on a corn yield goal of 112 kg ha(-1) was 40 Mg ha(-1). Inorganic N was added at the rate of 100 kg N ha(-1), also based on a corn yield of 7.03 tons ha(-1). Experimental treatments were: control (CONT) soil; control with N (CONT + N); switchgrass residues (USG); USG with N (USG + N); switchgrass biochars at 250 °C (250SG); SG at 250 °C with N (250SG + N); SG at 500 °C (500SG); and SG at 500 °C with N (500SG + N). Cumulative and net CO2-C evolution was increased by the additions of SG and USG especially when supplemented with N. Soils treated with 250SG (8.6 mg kg(-1)) had the least concentration of total inorganic nitrogen (TIN) while the greatest amount of TIN was observed from the CONT + N (19.0 mg kg(-1)). Our results suggest that application of SG in the short term may cause N immobilization resulting in the reduction of TIN.

  9. Strong carbon sink of monsoon tropical seasonal forest in Southern Vietnam

    NASA Astrophysics Data System (ADS)

    Deshcherevskaya, Olga; Anichkin, Alexandr; Avilov, Vitaly; Duy Dinh, Ba; Luu Do, Phong; Huan Tran, Cong; Kurbatova, Julia

    2014-05-01

    Comparison between anthropogenic emission of carbon dioxide and atmospheric carbon pool change displays that only half of emitted CO2 remains in air, leaving so-called 'missing sink' of carbon. Terrestrial biosphere and ocean accumulate each about a half of this value (Gifford, 1994). Forest biomes play the decisive role in 'missing sink' because of high primary production flux and large carbon pool. Almost all the sink belongs to boreal forests, because warming and wetting coupled with increasing CO2 concentration and N deposition gives more favorable conditions for boreal ecosystems. On the contrary, tropical climate changes effect on forests is not obvious, probably cause more drought conditions; tropical forests suffer from 1.2 % per year area reduction and disturbance. Whether primary tropical forests act as carbon sink is still unclear. Biomass inventories at 146 forest plots across all the tropics in 1987-1997 revealed low carbon sink in humid forests biomass of 49 (29-66; 95% C.I.) g C m-2 year-1 on average (Malhi, 2010). Estimates for undisturbed African forests are close to global (Ciais et al., 2008). Eddy covariance (EC) observations with weak-turbulence correction in Amazonia reveal near-zero or small negative (i.e. sink) balance (Clark, 2004). Three EC sites in SE Asia primary forests give near-zero balance again (Saigusa et al., 2008; Kosugi et al., 2012). There are two main groups of explanations of moderate tropical carbon sink: (a) recovering of large-disturbance in the past or (b) response to current atmospheric changes: increase of CO2 concentration and/or climate change. So, strong carbon accumulation is not common for primary tropical forests. In this context sink of 402 g C m-2 in 2012 at EC station of Nam Cat Tien (NCT), Southern Vietnam (N 11°27', E 107°24', 134 m a.s.l.) in primary monsoon tropical forest looks questionably. EC instrument set at NCT consists of CSAT3 sonic anemometer and LI-7500A open-path gas analyzer. All the standard

  10. Identification of dissolved sulfate sources and the role of sulfuric acid in carbonate weathering using dual-isotopic data from the Jialing River, Southwest China

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Dong; Liu, Cong-Qiang; Liu, Xiao-Long; Bao, Li-Ran

    2011-08-01

    Rock weathering by carbonic acid has played a substantial role in both the global carbon cycle and related climate change. Carbonic acid as the major weathering agent has been accepted, whereas the importance of other acid (sulfuric, nitric or organic acids) as an agent is gradually recognized. Here, we examine sulfate dual-isotopic evidence ( δ34S and δ18O) and water chemistry from the Jialing River (Sichuan Basin, Southwest China) to identify dissolved sulfate sources and the role of sulfuric acid in carbonate weathering. A survey was carried out at 29 sites where surface water was sampled during the rainy (July, 2008) and dry (February, 2009) seasons in the Jialing River. The chemical composition of river water was characterized by a dominance of Ca 2+, Mg 2+ and HCO3-, and SO42-, which accounted for more than 90% of the total ion concentrations. Water chemistry varied greatly in time and space, particularly for Na +, Cl -, and SO42-. This variation was a result of anthropogenic influences, such as acid deposition and domestic sewage inputs. Co-variation of the equivalent ratios of [Ca 2+ + Mg 2+] and [ SO42- + HCO3-] indicate that it required significant additional SO42- to achieve ionic balance, which implied that sulfuric acid might play a relatively important role in carbonate weathering of this river basin. Water samples from the Jialing River were significantly rich in SO42-, and increased almost two times from 274 μM in the period of 1958-1990 to 499 μM in this study. The use of co-variations of δ34Svs. δ18O and of δ18Ovs. δ18OO allowed us to demonstrate that most of the sulfate in the waters of the Jialing River was derived from sulfide oxidation and atmospheric inputs by high sulfur-content coal combustion while the contribution of sulfate from domestic and industrial wastewater could be important in the dry season. Thus, the contribution of sulfuric acid, produced by such sulfide oxidation and the oxidation of atmospheric SO 2 emitted from coal

  11. Diagenesis, weathering and paleoenvironmental conditions from postglacial diamictite/cap carbonate transition layers of the Otavi Group (NW-Namibia)

    NASA Astrophysics Data System (ADS)

    Gyollai, I.; Popp, F.; Mader, D.; Koeberl, Ch.

    2012-04-01

    ,3 ]. The detritus of the basal cap carbonates is rich in kaolinite and montmorillonite and has low K/Cs values, indicating a high weathering rate. Specific results for the Marinoan postglacial transition layers: The Marinoan diamictites (Ghaub Fm.) and their superposed postglacial transition layers (basal Maieberg Fm) are characterized in a few cases by very high Th/Co, Th/Sc and LREE/HREE ratios, which indicate some influence of a felsic source area. The detrital/recrystallized components of these iron-poor diamictites are rich in pyrite and quartz and display a REE enrichment compared to PAAS, which indicates a hydrothermal component during their accumulation [3]. Conlusions 1) Sturtian layers: possibly different source areas supplied the sedimentary basins 2) Marinoan layers : sediments were influenced by hydrothermal fluids and diagenetic alteration 3) Reducing conditions existed in the marine environment during both of the "Snowball Earth" glaciation periods each followed by oxidative conditions reflected in the geochemical composition of related postglacial cap carbonates. Acknowledgement Our work is funded by the Austrian Academy of Sciences (IGCP 512) (to CK).

  12. Severe Weather

    ERIC Educational Resources Information Center

    Forde, Evan B.

    2004-01-01

    Educating the public about safety issues related to severe weather is part of the National Oceanic and Atmospheric Administration's (NOAA) mission. This article deals with a poster entitled, "Severe Weather," that has been created by NOAA to help educate the public about hazardous weather conditions. The four types of severe weather highlighted in…

  13. Severe Weather

    ERIC Educational Resources Information Center

    Forde, Evan B.

    2004-01-01

    Educating the public about safety issues related to severe weather is part of the National Oceanic and Atmospheric Administration's (NOAA) mission. This month's insert, Severe Weather, has been created by NOAA to help educate the public about hazardous weather conditions. The four types of severe weather highlighted in this poster are hurricanes,…

  14. Severe Weather

    ERIC Educational Resources Information Center

    Forde, Evan B.

    2004-01-01

    Educating the public about safety issues related to severe weather is part of the National Oceanic and Atmospheric Administration's (NOAA) mission. This article deals with a poster entitled, "Severe Weather," that has been created by NOAA to help educate the public about hazardous weather conditions. The four types of severe weather highlighted in…

  15. Severe Weather

    ERIC Educational Resources Information Center

    Forde, Evan B.

    2004-01-01

    Educating the public about safety issues related to severe weather is part of the National Oceanic and Atmospheric Administration's (NOAA) mission. This month's insert, Severe Weather, has been created by NOAA to help educate the public about hazardous weather conditions. The four types of severe weather highlighted in this poster are hurricanes,…

  16. Conservation tillage versus conventional tillage on carbon stock in a Mediterranean dehesa (southern Spain)

    NASA Astrophysics Data System (ADS)

    Parras-Alcántara, Luis; Lozano-García, Beatriz

    2014-05-01

    Understanding soil dynamics is essential for making appropriate land management decisions, as soils can affect the carbon content from the atmosphere, emitting large quantities of CO2 or storing carbon. This property is essential for climate change mitigation strategies as agriculture and forestry soil management can affect the carbon cycle. The dehesa is a Mediterranean silvopastoral system formed by grasslands with scattered oaks (Quercus ilex or Q. suber). The dehesa is a pasture where the herbaceous layer is comprised of either cultivated cereals such as oat, barley and wheat or native vegetation dominated by annual species, which are used as grazing resources. In addition, the dehesa is a practice dedicated to the combined production of Iberian swine, sheep, fuel wood, coal and cork, as well as hunting. The dehesa is characterized by the preservation of forest oaks. In this work, we compared two management practices such as organic farming (OF) and conventional tillage (CT) on soil organic carbon stocks (SOC-S) in Cambisols (CM) and Leptosols (LP), and we analyzed the quality of these soils based on stratification ratio (SR) in a Mediterranean dehesa. MATERIAL AND METHODS An analysis of 85 soil profiles was performed in 2009 in Los Pedroches Valley (Cordoba, southern Spain). Two soil management practices were selected: OF (isolated trees of variable densities —15-25— trees ha-1, mostly holm and cork oaks, and patches of shrubs — cistaceae, fabaceae and lamiaceae— with a herbaceous pasture layer mostly composed of therophytic species and livestock are introduced to provide organic fertilizer to the soil, without ploughing and animal manure from the farms may be incorporated) for 20 years and CT (similar to OF, with ploughing —annual passes with a disc harrow and/or cultivator— is aimed at growing grain for livestock or at clearing the encroaching shrubs) in CM and LP. The dehesas studied were silvopastoral systems without cropping. Soil properties

  17. Empirical ocean color algorithms for estimating particulate organic carbon in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Allison, David B.; Stramski, Dariusz; Mitchell, B. Greg

    2010-10-01

    We have examined empirical algorithms for estimating surface concentration of particulate organic carbon (POC) from remotely sensed ocean color in the Southern Ocean using field data of POC, spectral remote-sensing reflectance, Rrs(λ), and the inherent optical properties (IOPs) of seawater collected during a number of cruises. Several algorithm formulations have been considered, including direct relationships between POC and the blue-to-green band ratios of reflectance and a single-wavelength two-step algorithm that consists of relationships linking reflectance to the backscattering coefficient and POC to the particulate backscattering coefficient at 555 nm. The best error statistics among the algorithms tested were obtained for the power function fit POC (in mg m-3) = 189.29 [Rrs(443)/Rrs(555)]-0.87. This band ratio algorithm is based on 85 pairs of field data and shows a small mean bias of about 3%, the normalized root mean square error of 27%, and the determination coefficient of 0.93. These error statistics as well as the analysis of matchup comparisons of satellite-derived POC and in situ POC determinations support the prospect for reasonably good performance of this algorithm in the Southern Ocean. The two-step empirical algorithm operating at 555 nm shows inferior error statistics of the regression fits and matchup comparisons compared with the band ratio algorithm. The analysis of our data set also indicates that a general trend of variation in the blue-to-green reflectance band ratio over the examined range of POC values is driven primarily by the green-to-blue ratio of particulate absorption coefficient.

  18. Hydrochemical Modeling of Dissolved Organic Carbon in a Small, Undisturbed, Forested Watershed in Southern Chile

    NASA Astrophysics Data System (ADS)

    Valdivia, M. V.; Walter, M. T.; Salmon, C. D.; Hedin, L. O.; Walter, M. F.

    2004-12-01

    The objective of the present study is to model Dissolved Organic Carbon (DOC) concentrations in a stream draining a small, undisturbed, old-growth forested watershed in Southern Chile and test model results against measured data. DOC plays an important role in several processes in terrestrial and aquatic ecosystems. For example, through the formation of organic complexes, DOC can influence nutrient availability, affect the solubility, mobility, and toxicity of metals, and control the absorption of pesticides to soils. DOC also influences biological activity by absorbing UV-B radiation and can contribute significantly to freshwater acidity. Additionally, DOC is linked to the formation of trihalomethanes as by-products of the disinfection of drinking water with chlorine, which constitutes a potentially serious threat to human health. Despite plentiful research on biogeochemical processes controlling DOC production and consumption, there is little information from minimally impacted environments, which can provide valuable baseline information from which to evaluate the more impacted ecosystems. Our study focused on a virtually unpolluted old-growth forested watershed in Southern Chile. We developed a conceptual model that assumes DOC production in forest soils is a function of temperature and DOC transport from soil to stream water is a function of discharge and hydrological flow paths. The hydrological response of the catchment under study was simulated using a simple lumped model, based on two years of meteorological data previously collected. Three different equations were used to simulate DOC concentrations in soil water as a function of temperature, and ultimately to derive DOC concentrations in streamflow. Model results were tested against two years of measured DOC concentrations in streamflow, and all three models provided a reasonably good representation of the DOC response of the small studied watershed and a better agreement to the observed DOC than

  19. Impact of peatland restoration on nutrient and carbon leaching from contrasting sites in southern Finland

    NASA Astrophysics Data System (ADS)

    Vasander, Harri; Sallantaus, Tapani; Koskinen, Markku

    2010-05-01

    Impacts of peatland restoration on nutrient and carbon leaching from contrasting sites in southern Finland Tapani Sallantaus1, Markku Koskinen2, Harri Vasander2 1)Finnish Environment Institute, Biodiversity unit, Box 140, FIN-00251 Helsinki, Finland, tapani.sallantaus@ymparisto.fi 2)Department of Forest Sciences, University of Helsinki, Box 27, FIN-00014 University of Helsinki, Finland, markku.koskinen@helsinki.fi, harri.vasander@helsinki.fi Less than 20 % of the original mire area of southern Finland is still in natural state. Even many peatlands in today's nature conservation areas had been partly or totally drained before conservation. Until now, about 15000 ha of peatlands have been restored in conservation areas. Here we present data concerning changes in leaching due to restoration in two contrasting areas in southern Finland. The peatlands in Seitseminen have originally been fairly open, growing stunted pine, and unfertile, either bogs or poor fens. The responses of tree stand to drainage in the 1960s were moderate, and the tree stand before restoration was about 50 m3/ha, on average. The trees were partly harvested before filling in the ditches mainly in the years 1997-1999 . The peatlands of Nuuksio are much more fertile than those in Seitseminen, and had greatly responded to drainage, which took place already in the 1930s and 1950s. The tree stand consisted mainly of spruce and exceeded 300 m3/ha in large part of the area. The ditches were dammed in the autumn 2001 and the tree stand was left standing. Runoff water quality was monitored in three basins in both areas. To obtain the leaching rates, we used simulated runoff data obtained from the Finnish Environment Institute, Hydrological Services Division. The responses in leaching were in the same direction in both cases. However, especially when calculated per restored hectare (Table 1), the responses were much stronger in the more fertile areas of Nuuksio for organic carbon and nitrogen, but not so much

  20. The use of carbon and sulfur isotopes as correlation parameters for the source identification of beach tar in the southern California borderland

    NASA Astrophysics Data System (ADS)

    Hartman, Blayne; Hammond, Douglas E.

    1981-03-01

    Carbon and sulfur isotope ratios and total sulfur content are used to correlate beach tars depositing near Los Angeles with their probable sources. Analysis is confined strictly to the asphaltene fraction of petroleum owing to the insensitivity of this fraction to weathering processes. The δ 13C, δ 34S and % S of the asphaltene fraction of natural offshore seep oils range from -22.51 to -23.20%., +7.75 to + 15.01%. and 4.45 to 8.27%, respectively. Values for local offshore production wells overlapped those for the natural seepage, ranging from -22.10 to -22.85%., -2.96 to 13.90%., and 0.81 to 8.00%. Analytical values for these parameters show that tanker crudes imported into the area are not similar to the California oils. Analysis of the same parameters in beach tars collected during 1976-1977 indicates a close match with the potential source oils, thus it is concluded that these parameters are useful for identifying petroleum sources, even after 2-4 weeks of weathering. Results indicate that 55% of the tars in Santa Monica Bay are derived from natural oil seepage 150km to the northwest at Coal Oil Point, 26% are derived from natural oil seepage in Santa Monica Bay, and 19% are derived from unknown sources. Models of tar transport are inferred which are consistent with the seasonal deposition pattern. Tar from Coal Oil Point natural oil seeps is transported southward in the southern California gyre during the spring, summer and fall seasons, but probably undergoes northward transport during the winter season due to the surfacing of the Davidson Current. Tar from the Santa Monica Bay natural oil seeps moves onshore, but deposition rate seems to depend on seepage flow rate.

  1. Machine learning and linear regression models to predict catchment-level base cation weathering rates across the southern Appalachian Mountain region, USA

    Treesearch

    Nicholas A. Povak; Paul F. Hessburg; Todd C. McDonnell; Keith M. Reynolds; Timothy J. Sullivan; R. Brion Salter; Bernard J. Crosby

    2014-01-01

    Accurate estimates of soil mineral weathering are required for regional critical load (CL) modeling to identify ecosystems at risk of the deleterious effects from acidification. Within a correlative modeling framework, we used modeled catchment-level base cation weathering (BCw) as the response variable to identify key environmental correlates and predict a continuous...

  2. The southern Brazilian grassland biome: soil carbon stocks, fluxes of greenhouse gases and some options for mitigation.

    PubMed

    Pillar, V D; Tornquist, C G; Bayer, C

    2012-08-01

    The southern Brazilian grassland biome contains highly diverse natural ecosystems that have been used for centuries for grazing livestock and that also provide other important environmental services. Here we outline the main factors controlling ecosystem processes, review and discuss the available data on soil carbon stocks and greenhouse gases emissions from soils, and suggest opportunities for mitigation of climatic change. The research on carbon and greenhouse gases emissions in these ecosystems is recent and the results are still fragmented. The available data indicate that the southern Brazilian natural grassland ecosystems under adequate management contain important stocks of organic carbon in the soil, and therefore their conservation is relevant for the mitigation of climate change. Furthermore, these ecosystems show a great and rapid loss of soil organic carbon when converted to crops based on conventional tillage practices. However, in the already converted areas there is potential to mitigate greenhouse gas emissions by using cropping systems based on no soil tillage and cover-crops, and the effect is mainly related to the potential of these crop systems to accumulate soil organic carbon in the soil at rates that surpass the increased soil nitrous oxide emissions. Further modelling with these results associated with geographic information systems could generate regional estimates of carbon balance.

  3. Carbon export fluxes in the Southern Ocean: results from inverse modeling and comparison with satellite-based estimates

    NASA Astrophysics Data System (ADS)

    Schlitzer, Reiner

    The use of dissolved nutrients and carbon for photosynthesis in the euphotic zone and the subsequent downward transport of particulate and dissolved organic material strongly affect carbon concentrations in surface water and thus the air-sea exchange of CO 2. Efforts to quantify the downward carbon flux for the whole ocean or on basin-scales are hampered by the sparseness of direct productivity or flux measurements. Here, a global ocean circulation, biogeochemical model is used to determine rates of export production and vertical carbon fluxes in the Southern Ocean. The model exploits the existing large sets of hydrographic, oxygen, nutrient and carbon data that contain information on the underlying biogeochemical processes. The model is fitted to the data by systematically varying circulation, air-sea fluxes, production, and remineralization rates simultaneously. Use of the adjoint method yields model property simulations that are in very good agreement with measurements. In the model, the total integrated export flux of particulate organic matter necessary for the realistic reproduction of nutrient data is significantly larger than export estimates derived from primary productivity maps. Of the 10,000 TgC yr -1(10 GtC yr -1) required globally, the Southern Ocean south of 30°S contributes about 3000 TgC yr -1 (33%), most of it occurring in a zonal belt along the Antarctic Circumpolar Current and in the Peru, Chile and Namibia coastal upwelling regions. The export flux of POC for the area south of 50°S amounts to 1000±210 TgC yr -1, and the particle flux in 1000 m for the same area is 115±20 TgC yr -1. Unlike for the global ocean, the contribution of the downward flux of dissolved organic carbon is significant in the Southern Ocean in the top 500 m of the water column. Comparison with satellite-based productivity estimates (CZCS and SeaWiFS) shows a relatively good agreement over most of the ocean except for the Southern Ocean south of 50°S, where the model

  4. Oxidation of sulfides and rapid weathering in recent landslides

    NASA Astrophysics Data System (ADS)

    Emberson, Robert; Hovius, Niels; Galy, Albert; Marc, Odin

    2016-09-01

    Linking together the processes of rapid physical erosion and the resultant chemical dissolution of rock is a crucial step in building an overall deterministic understanding of weathering in mountain belts. Landslides, which are the most volumetrically important geomorphic process at these high rates of erosion, can generate extremely high rates of very localised weathering. To elucidate how this process works we have taken advantage of uniquely intense landsliding, resulting from Typhoon Morakot, in the T'aimali River and surrounds in southern Taiwan. Combining detailed analysis of landslide seepage chemistry with estimates of catchment-by-catchment landslide volumes, we demonstrate that in this setting the primary role of landslides is to introduce fresh, highly labile mineral phases into the surface weathering environment. There, rapid weathering is driven by the oxidation of pyrite and the resultant sulfuric-acid-driven dissolution of primarily carbonate rock. The total dissolved load correlates well with dissolved sulfate - the chief product of this style of weathering - in both landslides and streams draining the area (R2 = 0.841 and 0.929 respectively; p < 0.001 in both cases), with solute chemistry in seepage from landslides and catchments affected by significant landsliding governed by the same weathering reactions. The predominance of coupled carbonate-sulfuric-acid-driven weathering is the key difference between these sites and previously studied landslides in New Zealand (Emberson et al., 2016), but in both settings increasing volumes of landslides drive greater overall solute concentrations in streams. Bedrock landslides, by excavating deep below saprolite-rock interfaces, create conditions for weathering in which all mineral phases in a lithology are initially unweathered within landslide deposits. As a result, the most labile phases dominate the weathering immediately after mobilisation and during a transient period of depletion. This mode of

  5. Control of ocean carbon storage and atmospheric pCO2 by Southern Ocean sea ice dynamics

    NASA Astrophysics Data System (ADS)

    Zakem, E.; Ferreira, D.; Follows, M. J.

    2012-12-01

    Change in annual sea ice in the Southern ocean has been proposed as a control on atmospheric pCO2 levels since Antarctic glacial inception around 34 Ma. Sea ice coverage slows or prevents the degassing of carbon-rich upwelled water, increasing ocean carbon storage, though the significance of this process has been doubted due to the coincidental decrease of the biological pump with ice cover. Here we explore the mechanism by which southern ocean sea ice coverage and dynamics drive atmospheric pCO2 levels in the Southern Ocean. To this end, we analyze the biogeochemical output of coupled ocean-atmosphere-sea ice GCM models with simplified geometry. Bottom water formation rates are controlled by manipulating ice dynamics. We show that the dominant difference in the ocean carbon content between model states is mainly driven by air-sea disequilibrium, rather than by solubility or biological productivity. As bottom water formation strengthens, the overturning cell underneath the sea ice is enriched in DIC at depth, but ice cover prevents outgassing to the atmosphere upon return to the surface. When bottom water is present, the ocean fills with carbon-rich water, driving down atmospheric pCO2. Our results suggest that it is the processes driving sea ice production on Antarctica continental margins such as atmospheric circulation and ice-shelf interaction that influence ocean carbon storage, rather than solely the existence of sea ice. This suggests the mechanism by which the onset of Antarctic Bottom Water formation after the opening of the Southern ocean gateways may have served as a positive feedback to decreasing pCO2 and a cooling climate.

  6. Synsedimentary deformation and the paleoseismic record in Marinoan cap carbonate of the southern Amazon Craton, Brazil

    NASA Astrophysics Data System (ADS)

    Soares, Joelson Lima; Nogueira, Afonso César Rodrigues; Domingos, Fábio; Riccomini, Claudio

    2013-12-01

    , and fractures and folds of events 3 and 4 are consistent with regional extensional tectonics associated with earthquakes that triggered sediment deformation. The 200 km that separate the occurrences of cap carbonates suggest that important seismic events took place during the early Ediacaran in the southern Amazon Craton.

  7. What is the Origin of Carbonate Rich Chevron Dunes in Southern Madagascar?

    NASA Astrophysics Data System (ADS)

    Abbott, D. H.; Gusiakov, V. K.; Rambolamanana, G.; Galinskaya, K.; Raveloson, A.; Breger, D. L.

    2015-12-01

    Southern Madagascar contains extensive sets of chevron dunes along the coast. The largest dunes extend up to 185 meters above sea level and are more than 40 km in length. While most researchers have assumed that the sand in the dunes was transported inland by the wind, we instead have proposed that the deposits are from a megatsunami event. The present data appear to support our hypothesis. We used a coulometer to determine the bulk carbonate content of 22 samples from the Ampalaza and Fenambosy dunes and their vicinity. We found that the median CaCO3 content of the dunes was over 40% with a typical range from 22 to 58% CaCO3. At off dune sites, where the substrate was exposed, and at a few sites closer to the ocean, the CaCO3 content ranged from 0% to 9%. Local beach sands contained ~ 52-54% CaCO3. At a site on the Fenambosy chevron (elevation~180 meters, location ~22 km along strike of the dune and 8.0 km in a direct line to the ocean) at the edge of a steep escarpment, the sand contained abundant marine microfossils and ~52% CaCO3. Just below the escarpment (4.7 km from the ocean) the sand contained ~58% CaCO3. Microprobe analyses of 10 carbonate fossils from the distal end of the Ampalaza chevron (elevation 68 meters, location ~42 km along strike of the dune) showed MgO contents of 1 to 6% and CaO contents of 49 to 54%. SiO2 contents are typically less than 0.1%. The bulk sand at this latter site contained ~49% CaCO3. In all cases, the carbonate fossils appear as single shells with no signs of being eroded from pre-existing, lithified rock. The low bulk MgO and SiO2 contents of the carbonate fossils are consistent with unlithified marine sediment as their source. Individual mineral grains in the dune sand are relatively angular. The sands contain abundant heavy minerals and are poorly sorted. The maximum grain size at some sites exceeds 2 mm. These observations are most consistent with a tsunami origin for the chevron dunes. AMS 14C age dates on well

  8. Impact of nitrogenous fertilizers on carbonate dissolution in small agricultural catchments: Implications for weathering CO 2 uptake at regional and global scales

    NASA Astrophysics Data System (ADS)

    Perrin, Anne-Sophie; Probst, Anne; Probst, Jean-Luc

    2008-07-01

    The goal of this study was to highlight the occurrence of an additional proton-promoted weathering pathway of carbonate rocks in agricultural areas where N-fertilizers are extensively spread, and to estimate its consequences on riverine alkalinity and uptake of CO 2 by weathering. We surveyed 25 small streams in the calcareous molassic Gascogne area located in the Garonne river basin (south-western France) that drain cultivated or forested catchments for their major element compositions during different hydrologic periods. Among these catchments, the Hay and the Montoussé, two experimental catchments, were monitored on a weekly basis. Studies in the literature from other small carbonate catchments in Europe were dissected in the same way. In areas of intensive agriculture, the molar ratio (Ca + Mg)/HCO 3 in surface waters is significantly higher (0.7 on average) than in areas of low anthropogenic pressure (0.5). This corresponds to a decrease in riverine alkalinity, which can reach 80% during storm events. This relative loss of alkalinity correlates well with the NO3- content in surface waters. In cultivated areas, the contribution of atmospheric/soil CO 2 to the total riverine alkalinity (CO 2 ATM-SOIL/HCO 3) is less than 50% (expected value for carbonate basins), and it decreases when the nitrate concentration increases. This loss of alkalinity can be attributed to the substitution of carbonic acid (natural weathering pathway) by protons produced by nitrification of N-fertilizers (anthropogenic weathering pathway) occurring in soils during carbonate dissolution. As a consequence of these processes, the alkalinity over the last 30 years shows a decreasing trend in the Save river (one of the main Garonne river tributaries, draining an agricultural catchment), while the nitrate and calcium plus magnesium contents are increasing. We estimated that the contribution of atmospheric/soil CO 2 to riverine alkalinity decreased by about 7-17% on average for all the studied

  9. Weather & Weather Maps. Teacher's Manual.

    ERIC Educational Resources Information Center

    Metro, Peter M.; Green, Rachel E.

    This guide is intended to provide an opportunity for students to work with weather symbols used for reporting weather. Also included are exercises in location of United States cities by latitude and longitude, measurement of distances in miles and kilometers, and prediction of weather associated with various types of weather fronts. (RE)

  10. Weather & Weather Maps. Teacher's Manual.

    ERIC Educational Resources Information Center

    Metro, Peter M.; Green, Rachel E.

    This guide is intended to provide an opportunity for students to work with weather symbols used for reporting weather. Also included are exercises in location of United States cities by latitude and longitude, measurement of distances in miles and kilometers, and prediction of weather associated with various types of weather fronts. (RE)

  11. Sensitivity of carbon paleoproductivity in the Southern California Current System on different time scales for the last 2 ka

    NASA Astrophysics Data System (ADS)

    Abella-Gutiérrez, Jose; Herguera, Juan Carlos

    2016-07-01

    The San Lázaro Basin (SLB) sediment record is highly sensitive to the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) due to its location vertically underlying the dynamic boundary between the northern, cooler and fresher waters of the California Current System (CCS) and the southern, warmer and saltier surface waters from the subtropics and tropics. Warm sea surface temperatures (SSTs) and the ensuing stratified surface water column favor carbonate productivity, mostly dominated by the export of coccolithophorids as observed during El Niño events, while cool SSTs and a less stratified water column favor a relatively higher export of organic carbon. Here we show how during the last two millennia, the mechanisms that drive the organic carbon and carbonate export depend on the time scale considered. The organic carbon and carbonate records show opposite trends for the past 2000 years. On multicentennial periodicities, their variability is probably a result of precessional forcing and associated decreasing Northern Hemisphere insolation, which has been shown to affect the migration of the Intertropical Convergence Zone and the polar jet stream. On shorter time scales, interannual to centennial, the SLB records exhibit an ENSO-like variability; similarly, decadal to multidecadal variability is correlated with instrumental and reconstructed PDO records. We further show how interannual variance seems to have increased during the Little Ice Age, most likely related to large ENSO events, in contrast with an apparent reduction in this type of variability between 400 and 1350 Common Era, suggesting a changing sensitivity of the ENSO teleconnection in the southern CCS for the past two millennia.

  12. Isotopic disequilibrium in Globigerina bulloides and carbon isotope response to productivity increase in Southern Ocean

    PubMed Central

    Prasanna, K.; Ghosh, Prosenjit; Bhattacharya, S. K.; Mohan, K.; Anilkumar, N.

    2016-01-01

    Oxygen and carbon isotope ratios in planktonic foraminifera Globigerina bulloides collected from tow samples along a transect from the equatorial Indian ocean to the Southern Ocean (45°E and 80°E and 10°N to 53°S) were analysed and compared with the equilibrium δ18O and δ13C values of calcite calculated using the temperature and isotopic composition of the water column. The results agree within ~0.25‰ for the region between 10°N and 40°S and 75–200 m water depth which is considered to be the habitat of Globigerina bulloides. Further south (from 40°S to 55°S), however, the measured δ18O and δ13C values are higher than the expected values by ~2‰ and ~1‰ respectively. These enrichments can be attributed to either a ‘vital effect’ or a higher calcification rate. An interesting pattern of increase in the δ13C(DIC) value of the surface water with latitude is observed between 35°S and~ 60°S, with a peak at~ 42°S. This can be caused by increased organic matter production and associated removal. A simple model accounting for the increase in the δ13C(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude. PMID:26903274

  13. Aerosol black carbon characteristics over a high-altitude Western Ghats location in Southern India

    NASA Astrophysics Data System (ADS)

    Udayasoorian, C.; Jayabalakrishnan, R. M.; Suguna, A. R.; Gogoi, Mukunda M.; Babu, S. Suresh

    2014-10-01

    Aerosol black carbon (BC) mass concentrations were continuously monitored over a period of 2 years (April 2010 to May 2012) from a high-altitude location Ooty in the Nilgiris Mountain range in southern India to characterize the distinct nature of absorbing aerosols and their seasonality. Despite being remote and sparsely inhabited, BC concentrations showed significant seasonality with higher values (~ 0.96 ± 0.35 μg m-3) in summer (March to May), attributed to increased vertical transport of effluents in the upwind valley regions, which might have been confined to the surrounding valley regions within the very shallow winter boundary layer. The local atmospheric boundary layer (ABL) influence in summer was further modulated by the long-range transported aerosols from the eastern locations of Ooty. During monsoon (June-August), the concentrations were far reduced (~ 0.23 ± 0.06 μg m-3) due to intense precipitation. Diurnal variations were found conspicuous mainly during summer season associated with local ABL. The spectral absorption coefficients (αabs) depicted, in general, flatter distribution (mostly < 1.0 for more than 85% of daily mean values), suggesting the relative dominance of fossil fuel combustion, though showed marginal seasonal change with higher values of αabs in summer.

  14. Ultrahigh-Temperature Metamorphism in Madurai Granulites, Southern India: Evidence from Carbon Isotope Thermometry.

    PubMed

    Satish-Kumar

    2000-07-01

    Ultrahigh-temperature (UHT) metamorphism in the Madurai Block of the southern Indian granulite terrain has been verified using the calcite-graphite isotope exchange thermometer. Carbon isotope thermometry has been applied to marbles from a locality near the reported occurrence of sapphirine granulites that have yielded temperature estimates of around 1000 degrees C. The delta(13)C and delta(18)O values of calcite are homogenous, implying equilibration of the isotopes during metamorphism. However, the delta(13)C values of single graphite crystals show variations in the order of 1 per thousand within a hand specimen. Detailed isotopic zonation studies indicate that graphite preserves either the time-integrated crystal growth history or reequilibrium fractionation during its cooling history. The graphite cores preserve higher delta(13)C values than the rims. The fractionation between calcite and graphite cores gives the highest metamorphic temperature of about 1060 degrees C, which matches the petrologically inferred temperature estimates in the high-magnesian pelites. The fractionation between graphite rims and calcite suggests a temperature of around 750 degrees C, which is interpreted to reflect retrograde cooling. This event is also observed in the sapphirine granulites. Calcite-graphite thermometry thus provides a useful tool to define UHT metamorphism in granulite terrains.

  15. Isotopic disequilibrium in Globigerina bulloides and carbon isotope response to productivity increase in Southern Ocean.

    PubMed

    Prasanna, K; Ghosh, Prosenjit; Bhattacharya, S K; Mohan, K; Anilkumar, N

    2016-02-23

    Oxygen and carbon isotope ratios in planktonic foraminifera Globigerina bulloides collected from tow samples along a transect from the equatorial Indian ocean to the Southern Ocean (45°E and 80°E and 10°N to 53°S) were analysed and compared with the equilibrium δ(18)O and δ(13)C values of calcite calculated using the temperature and isotopic composition of the water column. The results agree within ~0.25‰ for the region between 10°N and 40°S and 75-200 m water depth which is considered to be the habitat of Globigerina bulloides. Further south (from 40°S to 55°S), however, the measured δ(18)O and δ(13)C values are higher than the expected values by ~2‰ and ~1‰ respectively. These enrichments can be attributed to either a 'vital effect' or a higher calcification rate. An interesting pattern of increase in the δ(13)C(DIC) value of the surface water with latitude is observed between 35°S and~ 60°S, with a peak at~ 42°S. This can be caused by increased organic matter production and associated removal. A simple model accounting for the increase in the δ(13)C(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude.

  16. Attenuation of particulate organic carbon flux in the Scotia Sea, Southern Ocean, is controlled by zooplankton fecal pellets

    NASA Astrophysics Data System (ADS)

    Cavan, E. L.; Le Moigne, F. A. C.; Poulton, A. J.; Tarling, G. A.; Ward, P.; Daniels, C. J.; Fragoso, G. M.; Sanders, R. J.

    2015-02-01

    The Southern Ocean (SO) is an important CO2 reservoir, some of which enters via the production, sinking, and remineralization of organic matter. Recent work suggests that the fraction of production that sinks is inversely related to production in the SO, a suggestion that we confirm from 20 stations in the Scotia Sea. The efficiency with which exported material is transferred to depth (transfer efficiency) is believed to be low in high-latitude systems. However, our estimates of transfer efficiency are bimodal, with stations in the seasonal ice zone showing intense losses and others displaying increases in flux with depth. Zooplankton fecal pellets dominated the organic carbon flux and at stations with transfer efficiency >100% fecal pellets were brown, indicative of fresh phytodetritus. We suggest that active flux mediated by zooplankton vertical migration and the presence of sea ice regulates the transfer of organic carbon into the oceans interior in the Southern Ocean.

  17. Quantification of Deeply Derived Carbon Dioxide in Central and Southern Italy.

    NASA Astrophysics Data System (ADS)

    Cardellini, C.; Chiodini, G.; Caliro, S.; Frondini, F.; Morgantini, N.

    2005-12-01

    A large portion of the total water discharge from the Apennine carbonate aquifers (~ 58 %) has been sampled and analysed for major chemical components and for the isotopic composition of dissolved inorganic carbon (DIC). On the basis the carbon mass balance has been estimated that DIC derives from the dissolution of carbonates hosting the aquifers (~ 33 %), from the biogenic CO2 of the soils (~ 24 %), and for the greatest part from a deep source (~ 43 %). The modelling of the water-rock-gas interaction allowed to assess that groundwater composition is compatible with the evolution of infiltrating waters dissolving variable amounts of deeply derived CO2 with an isotopic composition in the range of that of the CO2 emitted in Italy from active volcanoes, geothermal fields, and cold gas emissions located in the western sector of the central and southern Italy. On the base of the computed deeply derived carbon dissolved in the groundwater a regional map of CO2 Earth degassing has been recently elaborated (Chiodini et al., 2004), pointing out the presence in the Tyrrhenian side of the Italian peninsula of two large regional degassing structures that, for the magnitude and for the geochemical features, can be related to a regional process of mantle degassing. In the western part of these regions is characterized by the presence of many CO2 rich gas emission releasing by soil diffuse degassing significant amount of CO2, geothermal systems, dissolved carbon in volcanic aquifers (Gambardella et.al., 2004) and large travertine deposits. Here, at smaller scale, a strong correlation between shallow geological structures and CO2 diffuse degassing was observed, suggesting that in this sector mantle fluids may enter the lower crust and move upwards through the interconnected network of extensional fractures and normal faults, accumulate in shallow reservoir and generate the high CO2 flux anomalies at the surface. On contrary, in the Adriatic foreland, which is characterized by a

  18. The environmental impact on air quality and exposure to carbon monoxide from charcoal production in southern Brazil.

    PubMed

    Gomes, Gabriel Meneghetti Faé; Encarnação, Fábio

    2012-07-01

    Black wattle silviculture is an important activity in southern Brazil. Much of the wood is used in the production of charcoal and the pyrolysis products impacts on air quality. This paper estimates the level of atmospheric contamination from the production of charcoal in one region of Brazil. We describe a low-cost charcoal kiln that can capture condensable gases and we estimate the levels of exposure of kiln workers to carbon monoxide. The latter results indicated that exposure to carbon monoxide can be reduced from an average of 950 ppm to 907 ppm and the mass of gases reduced by 16.8%. Copyright © 2012 Elsevier Inc. All rights reserved.

  19. Comparisons of carbon storages in Cunninghamia lanceolata and Michelia macclurei plantations during a 22-year period in southern China.

    PubMed

    Dong, Niu; Silong, Wang; Zhiyun, Ouyang

    2009-01-01

    Tree species composition was important for carbon storage within the same climate range. To quantify the dynamics of ecosystem carbon allocation as affected by different tree species, we measured the above- and below-ground biomass accumulation in 22 years, as well as the tissue carbon concentrations of trees in Cunninghamia lanceolata plantation and Michelia macclurei plantation. Results indicated that M. macclurei plantation significantly stored more carbon (174.8 tons/hm2) than C. lanceolata plantation (154.3 tons/hm2). Most of the carbon was found in the soil pool (57.1% in M. macclurei plantation, 55.2% in C. lanceolata plantation). Tree and soil component of M. macclurei plantation possessed significantly higher carbon storage than that of C. lanceolata plantation (p <0.05). No significant difference was found in the carbon storage of understory and forest floor. These results suggest that the broadleaved species (M. macclurei) possesses greater carbon sequestration potential than the coniferous species (C. lanceolata) in southern China.

  20. Functional soil organic carbon pools for major soil units and land uses in southern Germany

    NASA Astrophysics Data System (ADS)

    Kögel-Knabner, Ingrid; Wiesmeier, Martin

    2015-04-01

    Soil management, especially the type and intensity of land use, affect the carbon cycle to a high extent as they modify carbon sequestration in a specific soil. Thus man is intervening in the natural carbon cycle on a global scale. In our study, the amount of active, intermediate and passive SOC pools was determined for major soil types and land uses of Bavaria in southern Germany. Our SOC inventory revealed only slightly lower total SOC stocks in cropland soils compared to forest soils, when both top- and subsoils were considered. In cropland and grassland soils around 90% of total SOC stocks can be assigned to the intermediate and passive SOC pool. High SOC stocks in grassland soils are partly related to a higher degree of soil aggregation compared to cropland soils. The contribution of intermediate SOC in cropland soils was similar to that in grassland soils due to an increased proportion of SOM associated with silt and clay particles. The cultivation-induced loss of SOC due to aggregate disruption is at least partly compensated by increased formation of organo-mineral associations as a result of tillage that continuously promotes the contact of crop residues with reactive mineral surfaces. Contrary, forest soils were characterized by distinctly lower proportions of intermediate and passive SOC and a high amount of active SOC in form of litter and particulate organic matter which accounted for almost 40% of total SOC stocks. The determination of the current SOC content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long-term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional SOC. A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. The high

  1. Carbon and Sulphur Geochemistry of Rift Valley Sediments and Hydrothermal Fluids at the Ultra-Slow Spreading Southern Knipovich Ridge

    NASA Astrophysics Data System (ADS)

    Baumberger, T.; Frueh-Green, G. L.; Pedersen, R. B.; Thorseth, I. H.; Bernasconi, S. M.; Lilley, M. D.

    2008-12-01

    The rift valley of the ultra-slow spreading southern Knipovich Ridge in the Norwegian-Greenland Sea (73°N) is partly buried by a thick sediment cover, as at Middle Valley, Escanaba Trough and Guaymas Basin. These glacial and post-glacial sediments (12000-20000 years) derived from the nearby Bear Island fan likely act as a thermal and hydrogeological boundary to heat and fluid flow and influence hydrothermal fluid compositions. Geochemical studies of the rift valley sediments and the hydrothermal vent fluids of the recently discovered black smoker vent field Loki's Castle provide insights into the influence of the sediment cover on the composition of the hydrothermal fluids at the southern Knipovich Ridge. Here we present an overview of preliminary data on the carbon and sulphur geochemistry of the sedimentary and hydrothermal components at Loki's Castle and compare these with other sedimented and un-sedimented mid-ocean ridge hydrothermal systems. The hydrothermal vent fluids have a pH of 5.5 and are characterized by elevated concentrations of hydrogen, methane, hydrogen sulphide and ammonia, which reflect a strong sedimentary input. Short gravity cores of the rift valley sediments show relatively constant total carbon contents of approximately 1 wt%, but locally reach up to 4 wt%. Varying carbon isotope compositions reflect a mix of marine carbonates with organic carbon. Extracted sediment pore fluids show an increase in alkalinity and dissolved inorganic carbon (DIC) concentrations with increasing burial depth. The corresponding δ13CDIC values show a clear depletion with increasing alkalinity and DIC concentrations. The vent fluid compositions and carbon and sulphur isotope geochemistry provide constraints on redox conditions and thermocatalysis of organic carbon during fluid-sediment interaction, and are distinct from un- sedimented mid-ocean ridge hydrothermal fluids.

  2. Hydrogeology and potential for ground-water development, carbonate-rock aquifers in southern Nevada and southeastern California

    USGS Publications Warehouse

    Burbey, T.J.

    1997-01-01

    Seventeen hydrographic areas in southern Nevada were assessed for the ground-water development potential of the underlying carbonate-rock aquifers on the basis of geologic and hydrologic information developed as part of the Nevada Carbonate Aquifers Study and information compiled from previous investigations. All selected areas lie within a miogeoclinal belt where thick accumulations of carbonate rock followed by major episodes of compression and extension have greatly modified the region. Most of the selected hydrographic areas lie within the less extended terranes; however, several areas, or parts of areas, lie within severely extended terranes where carbonate rocks have been greatly thinned, or where deformed blocks of carbonate rock are discontinuous and isolated from surrounding carbonate rock aquifers. Three principal criteria were used to assess the development potential of each selected hydrographic area. These quantitative criteria are: (1) depth to water, (2) depth to and thickness of carbonate rocks, and (3) water quality. Other site-specific factors, such as accessibility and potential effects of ground-water development, are also discussed. Results suggest that sites with high potential for development may be scarce in southern Nevada. Many areas described as favorable on the basis of the three quantitative criteria were deemed unfavorable on the basis of possible short- and long-term effects associated with development and on the amount of available data used to make the assessment. The most favorable sites may be in more severely extended terranes, where development of isolated blocks (of carbonate-rock aquifer material) would be less likely to affect neighboring areas.

  3. Weathering, landscape equilibrium, and carbon in four watersheds in eastern Puerto Rico: Chapter H in Water quality and landscape processes of four watersheds in eastern Puerto Rico

    USGS Publications Warehouse

    Stallard, Robert F.; Murphy, Sheila F.; Stallard, Robert F.

    2012-01-01

    The U.S. Geological Survey's Water, Energy, and Biogeochemical Budgets (WEBB) program research in eastern Puerto Rico involves a double pair-wise comparison of four montane river basins, two on granitic bedrock and two on fine-grained volcaniclastic bedrock; for each rock type, one is forested and the other is developed. A confounding factor in this comparison is that the developed watersheds are substantially drier than the forested (runoff of 900–1,600 millimeters per year compared with 2,800–3,700 millimeters per year). To reduce the effects of contrasting runoff, the relation between annual runoff and annual constituent yield were used to estimate mean-annual yields at a common, intermediate mean-annual runoff of 1,860 millimeters per year. Upon projection to this intermediate runoff, the ranges of mean-annual yields among all watersheds became more compact or did not substantially change for dissolved bedrock, sodium, silica, chloride, dissolved organic carbon, and calcium. These constituents are the primary indicators of chemical weathering, biological activity on the landscape, and atmospheric inputs; the narrow ranges indicate little preferential influence by either geology or land cover. The projected yields of biologically active constituents (potassium, nitrate, ammonium ion, phosphate), and particulate constituents (suspended bedrock and particulate organic carbon) were considerably greater for developed landscapes compared with forested watersheds, consistent with the known effects of land clearing and human waste inputs. Equilibrium rates of combined chemical and physical weathering were estimated by using a method based on concentrations of silicon and sodium in bedrock, river-borne solids, and river-borne solutes. The observed rates of landscape denudation greatly exceed rates expected for a dynamic equilibrium, except possibly for the forested watershed on volcaniclastic rock. Deforestation and agriculture can explain the accelerated physical

  4. Multi-proxy Reconstruction of Seawater Chemistry Across K-Pg Boundary: Tracking Weathering Feedbacks in Response to Extreme Carbon Cycle Perturbation

    NASA Astrophysics Data System (ADS)

    Misra, S.; Elderfield, H.

    2014-12-01

    On geologic time scales concentrations of atmospheric CO2, a greenhouse gas and critical mediator of Earth's surface temperature and climate, is thought to be controlled by a balance between CO2 input from mantle degassing through volcanism and metamorphism and consumption via temperature-sensitive chemical weathering of tectonically uplifted continental rocks. This interplay between global climate and tectonic uplift also controls the delivery of cations to the oceans. Hence, past changes in seawater chemistry provide a powerful archive of the interplay and feedback between climate and tectonics. Mass Extinction Events, like that at K-Pg boundary, are characterized by rapid, global Carbon Cycle Perturbations either from increased mantle degassing or by incineration of the continents due to extra-terrestrial impact. It is hypothesized that enhanced chemical weathering of continental silicate rocks consumes this excess CO2 and restores steady-state. Lithium, B, and Mg are conservative ions in seawater that are isotopically homogeneous with a residence time much longer than the oceanic mixing time. As a result, δ7LiSW, δ11BSW, and δ26MgSW, recorded by marine calcites reflect a global picture and secular variations in isotopic composition of these elements within periods shorter than their residence time must thus reflect imbalances between the sources and sinks of these elements to and from the ocean. Cenozoic δ7LiSW shows an abrupt 5‰ drop across the K-Pg boundary, simultaneous with the seawater Ir and Os isotope spikes. This rapid decrease in δ7LiSW is due to a large instantaneous delivery of isotopically light Li to the oceans and cannot be produced by an impactor nor by Deccan trap volcanism, suggesting large-scale continental denudation. We will create high-resolution δ7LiSW, δ11BSW, and δ26MgSW records across K-Pg boundary using planktonic and benthic foraminifera from multiple ODP/DSDP sites to quantify the amount of C excursion and the response of

  5. Sinkhole susceptibility in carbonate rocks of the Apulian karst (southern Italy)

    NASA Astrophysics Data System (ADS)

    Di Santo, Antonio; Fazio, Nunzio L.; Fiore, Antonio; Lollino, Piernicola; Luisi, Michele; Miccoli, Maria N.; Pagliarulo, Rosa; Parise, Mario; Perrotti, Michele; Pisano, Luca; Spalluto, Luigi; Vennari, Carmela; Vessia, Giovanna

    2016-04-01

    Apulia region, the foreland of the southern Italian Apennines, is made up of a 6-7 km-thick succession of Mesozoic shallow-water limestones and dolostones, locally covered by thin and discontinuous Tertiary and Quaternary carbonate and clastic deposits. Due to their long subaerial exposure, the Mesozoic carbonate bedrock recorded the development in the subsurface of a dense network of karst cavities, mostly controlled by tectonic discontinuities. As a result, a strong susceptibility to natural sinkholes has to be recorded in Apulia. In addition, the possibility of occurrence of other problems related to the high number of man-made cavities has to be added in the region. A great variety of different typologies of artificial cavities (mostly excavated in the Plio-Pleistocene soft calcarenites) is actually present, including underground quarries, worship sites, oil mills, civilian settlements, etc. Overall, 2200 natural and 1200 artificial cavities, respectively, have been so far surveyed in Apulia. Following the urban development in the last century in Apulia, many of these cavities lie nowadays below densely populated neighborhoods, roads or communication routes. These conditions are at the origin of the main geomorphological hazard for the human society in Apulia, which requires a careful evaluation, aimed at protecting and safeguarding the human life, and at providing the necessary information for a correct land use planning and management. The importance of the sinkhole hazard is further testified by the worrying increase in the number of events during the last 5-6 years. In response to these situations, joint research activities were started by the Institute of Research for Hydrological Protection of the National Research Council (CNR-IRPI) and the Basin Authority of Apulia, aimed at several goals, that include (but are not limited to) the collection of information on natural and anthropogenic sinkholes in Apulia, the implementation of numerical analyses for

  6. The Effects of Storm Events on Carbon Dioxide Exchange in Southern Kaneohe Bay, Hawaii

    NASA Astrophysics Data System (ADS)

    Solomon, R. F.; Ostrander, C. E.; Chung, M.; Paquay, F.; de Gelleke, L.; Akiba, M.; Fagan, K. E.; de Carlo, E. H.; MacKenzie, F. T.; McManus, M. A.; Sabine, C. L.; Feely, R. A.

    2006-12-01

    The purpose of this study is to investigate the effects of local climatic variability on the biogeochemistry of southern Kaneohe Bay, Oahu. Intense or prolonged rainfall over the bay and its watershed generate pulses of nutrient- and sediment-rich freshwater that subsequently induce phytoplankton blooms and impact carbon cycling. Variable land-based inputs, boundary layer dynamics, as well as changes in water circulation patterns make it difficult to classify coastal waters solely as CO2 sinks or sources on annual time scales. This issue has been examined by various research groups, which have produced contradictory results, and has gained complexity owing to increasing atmospheric CO2 concentrations due to anthropogenic input. High frequency surface water data collection was carried out from instruments on our Coral Reef Instrumented Monitoring and CO2 Platform (CRIMP-CO2), which was first deployed in November, 2005. In addition, water column properties throughout the South bay were investigated through synoptic sampling. The "La Niña" event that occurred since the deployment of the buoy represented one of the wettest winter seasons in the area over the past 30 years. The results from the sampling of the major rainfall events during this period have been examined and contrasted, including one which lasted for over 40 days causing floods, triggering periodic sewage spills, and leading to highly turbid plumes extending far out into the South bay. Phytoplankton blooms and a drawdown of CO2 occurred following each of the major storm events, with pCO2 minima of approximately 228 to 280 μatm, causing the South bay waters to switch from being a net source to a net sink of atmospheric CO2. Wind speed, along with the extent of the CO2 drawdown, was found to be the major control on the magnitude of this sink. Increasing atmospheric CO2 concentrations cause a greater difference between air and water pCO2 during the blooms, when bay water pCO2 is relatively low

  7. Determinants of the spatial distributions of elemental carbon and particulate matter in eight Southern Californian communities

    NASA Astrophysics Data System (ADS)

    Urman, Robert; Gauderman, James; Fruin, Scott; Lurmann, Fred; Liu, Feifei; Hosseini, Reza; Franklin, Meredith; Avol, Edward; Penfold, Bryan; Gilliland, Frank; Brunekreef, Bert; McConnell, Rob

    2014-04-01

    Emerging evidence indicates that near-roadway pollution (NRP) in ambient air has adverse health effects. However, specific components of the NRP mixture responsible for these effects have not been established. A major limitation for health studies is the lack of exposure models that estimate NRP components observed in epidemiological studies over fine spatial scale of tens to hundreds of meters. In this study, exposure models were developed for fine-scale variation in biologically relevant elemental carbon (EC). Measurements of particulate matter (PM) and EC less than 2.5 μm in aerodynamic diameter (EC2.5) and of PM and EC of nanoscale size less than 0.2 μm were made at up to 29 locations in each of eight Southern California Children's Health Study communities. Regression-based prediction models were developed using a guided forward selection process to identify traffic variables and other pollutant sources, community physical characteristics and land use as predictors of PM and EC variation in each community. A combined eight-community model including only CALINE4 near-roadway dispersion-estimated vehicular emissions accounting for distance, distance-weighted traffic volume, and meteorology, explained 51% of the EC0.2 variability. Community-specific models identified additional predictors in some communities; however, in most communities the correlation between predicted concentrations from the eight-community model and observed concentrations stratified by community was similar to those for the community-specific models. EC2.5 could be predicted as well as EC0.2. EC2.5 estimated from CALINE4 and population density explained 53% of the within-community variation. Exposure prediction was further improved after accounting for between-community heterogeneity of CALINE4 effects associated with average distance to Pacific Ocean shoreline (to 61% for EC0.2) and for regional NOx pollution (to 57% for EC2.5). PM fine spatial scale variation was poorly predicted in both

  8. Helium and carbon isotope systematics of Rungwe geothermal gases and fluids; southern Tanzania

    NASA Astrophysics Data System (ADS)

    Barry, P. H.

    2009-12-01

    P. H. BARRY1*, D. R. HILTON1, T. P. FISCHER2, J. M. DE MOOR2, F. MANGASINI3 C. RAMIREZ4 1 Geosciences Research Division, Scripps Institution of Oceanography, UCSD, La Jolla, California 92093-0244, USA (*Correspondence: pbarry@ucsd.edu) 2 Department of Earth and Planetary Sciences, MSC 03 2040, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, USA. 3 Department of Mining and Mineral Processing Engineering, University of Dar Es Salaam, PO Box 35131, Dar Es Salaam, Tanzania. 4 Centro de Investigaciones en Ciencias Geologicas, Escuela Centroamericana de Geologia, Universidad de Costa Rica. The East African Rift (EAR) is the largest modern example of continental rifting, extending from the Afar depression in the north to the Rungwe region in southern Tanzania. EAR volcanism is attributed to the presence of one or more mantle plumes [1]. Late Miocene to recent volcanism and geothermal activity mark the Rungwe region [2], with mafic eruptions as recently as 200 years ago. Our aim is to delineate the southern geographical extent of plume influence on the propagating EAR by investigating the He-CO2 characteristics of geothermal fluids in the Rungwe region. We report new helium (He) and carbon (C) isotopes (3He/4He, δ13C) and relative abundance (CO2/3He) characteristics for a suite of 20 geothermal gas and fluid samples from 11 different localities in the Rungwe region. He-isotopes are in good agreement with previous reports [3], and range from ~1 RA to ~7 RA (MORB-like values), indicating admixture between upper mantle He and variable proportions of radiogenic He. C-isotopes ranges from -2.8 to -6.5 ‰ (vs. PDB) with all falling in the MORB range (~4.5 ± 2‰). CO2/3He ratios vary over 5 orders of magnitude from ~3 x 10^9 (MORB-like) to higher values (up to ~3 x 10^13) normally associated with crustal lithologies. Taken together, the He-CO2 data can be explained by 2-component mixing of a deep-seated mantle source with crustal component(s). There are no

  9. Comparative development of the Western United States and southern Kazakhstan, Soviet Union - Two early Paleozoic carbonate passive margins

    SciTech Connect

    Cooke, H.E. ); Taylor, M.E. ); Zhemchuzhnikov, S.V.; Apollonov, M.K.; Ergaliev, G. Kh.; Sargaskaev, Z.S. ); Dubinina, S.V. )

    1991-02-01

    Early Paleozoic passive continental margins of the Western united States and southern Kazakhstan evolved at low latitudes on rifted Precambrian continental crust adjacent to the proto-Pacific Ocean. In the Western United States, early Paleozoic carbonate submarine fans and slides formed on continental slopes in central Nevada. Coeval shoal-water carbonate sediments occurred to the east, in Utah, where they interfingered with siliciclastic sediments and onlapped the craton. In contrast, early Paleozoic carbonate sediments of the Malyi Karatau, southern Kazakhstan, were deposited on isolated microcontinental blocks that developed during Late Proterozoic rifting of the continental crust. Comparison of stratigraphic sections from Nevada and Malyi Karatau indicate a similar upward-shallowing and seaward-prograding evolution. The Hot Creek Range section in Nevada consists of the Upper Cambrian Swarbrick Formation and Tybo Shale, and Upper Cambrian and lowest Ordovician Hales Limestone. These depositional facies include basin plain (about 500 m), carbonate submarine fan and slides (200 m), upperslope (150 m), and platform margin (150 m). The Kyrshabakty and Batyrbay sections in the Malyi Karatau consist of Cambrian and lowest Ordovician rocks of the Shabakty Suite. Stratigraphic sections in both the Western United States and Malyi Karatau record three coeval episodes of sea level lowstands. These lowstands, which the authors interpret to be eustatic, are recognized by times of seaward collapse of large segments of the platform margins and deeper water slopes and by solution breccias and faunal discontinuities in shoal-water platform-interior sites.

  10. Carbon Flux to the Deep in three open sites of the Southern European Seas

    NASA Astrophysics Data System (ADS)

    Gogou*, A.; Sanchez-Vidal*, A.; Stavrakakis, S.; Durrieu de Madron, X.; Calafat, A. M.; Stabholz, M.; Psarra, S.; Canals, M.; Heussner, S.; Stavrakaki, I.; Papathanassiou, E.

    2012-04-01

    In this study we investigate the functioning of the biological pump in the Southern European Seas (SES). In order to constrain the rates of carbon production and export to depth, we combine estimations of satellite primary production data, algorithm-generated fluxes out of the euphotic layer and particulate organic carbon (POC) fluxes, as measured by sediment traps at the mesopelagic and bathypelagic layers in three sites located in the Western Mediterranean (WMED), the Eastern Mediterranean (EMED), and the Black Sea (BS). POC fluxes were monitored during one year period (Sept 2007 - Sept 2008) in the frame of SESAME project. Annual primary production by satellite estimations yielded values of 396 mg C m-2d-1 (EMED), 563 mg C m-2d-1 (WMED) and 617 mg C m-2d-1 (BS) (SeaWiFS; http://emis.jrc.ec.europa.eu). At the scale of the whole Mediterranean and the Black Sea basins, spatiotemporal variability of Chl-a concentrations during the time of our experiments revealed significant differences in the seasonal cycles. While the WMED site showed increased biomass centred around spring (March-April 2008), the EMED site showed higher values in mid-winter (January 2008), even thought almost one order of magnitude lower than those recorded in the western site. In contrast, the BS site showed increased Chl-a concentration in autumn (Nov 2007) and a lower increase in early spring (March 2008). Overall, the observed Chl-a seasonal patterns for the WMED and EMED sites match quite well the typical seasonal patterns ascribed to their hosting areas, corresponding to "blooming" and "non-blooming" biogeographic regions, respectively, as proposed by D'Ortenzio and Ribera d'Alcala (D'Ortenzio and Ribera d'Alcala, 2009). Moreover, based on the timing of the bloom (late fall) the seasonal pattern of the BS site is quite similar to that observed in Mediterranean regions having a "coastal" regime. Thus, specific physical and biogeochemical settings in the three contrasting sites affect the

  11. Quantification of Lateral Carbon Flux in a Chaparral Ecosystem in Southern California Alessandra Rossi, Walter Oechel, Patrick Murphy

    NASA Astrophysics Data System (ADS)

    Rossi, A.; Oechel, W. C.; Murphy, P.

    2013-12-01

    The lateral transport of carbon is a horizontal transfer of carbon away from the area it was withdrawn from the atmosphere (Ciais et al. 2006). Research regarding horizontal C transport has received much less attention in arid and semi-arid regions compared to other types of ecosystems. Drylands represent around 47.2% (Lal 2004) of the global terrestrial area and despite characterized by relatively low carbon flux, drylands comprise approximately 15.5% of the world's total soil organic carbon (SOC) (Eswaran et al. 2000, Schlesinger, 1991). Moreover, these dry areas contain at least as much soil inorganic carbon (SIC) as SOC (Eswaran et al. 2000). Therefore, these areas potentially have a large contribution to the global carbon budget and they deserve attention. A long-term observation of CO2 flux with the eddy covariance technique has been conducted since 1997 at Sky Oaks Field Station in Southern California, an area of Mediterranean climate at the climatic transition between semiarid area and desert. The long term record of CO2 flux showed the area has been a sink of CO2 of over -0.2 kgCm-2yr-1. In addition to evaluating vertical carbon fluxes, we initiated a project to evaluate lateral carbon transports using litter traps, sediment fences and two small weirs adjacent to the eddy covariance site. Preliminary results indicate that the lateral transfer of C in the area may offset the vertical influx to this shrub ecosystem. However, it is still necessary to develop the methodology to compare vertical carbon flux and the lateral carbon fluxes more accurately.

  12. Soil organic carbon distribution in an agricultural catchment in Southern Brazil: from hillslope to catchment scale.

    NASA Astrophysics Data System (ADS)

    Trigalet, Sylvain; Chartin, Caroline; Van Oost, Kristof; van Wesemael, Bas

    2017-04-01

    Understanding the soil organic carbon (SOC) distribution a few decades after conversion to cropland and plantations in a hilly catchment in southern Brazil is challenging due to scale-dependent controlling factors. Firstly, SOC, bulk density (BD) and texture were measured by depth intervals along 18 soil profiles located in three topographical positions (sloping plateau, central back slope and concave foot slope) in cropland and forest with contrasting slopes. SOC stocks in concave footslope position were not significantly different between fields on steep (11.1 kg C m-2) and gentle slopes (12.8 kg C m-2). However, in eroding profiles, SOC stocks are twice as high in fields on gentle slopes (17.6/12.6 kg C m-2) compared to steep slopes (8.3/7.1 kg C m-2). SOC stocks on steep slope on cropland (8.8 kg C m-2) are three times lower than SOC stocks on steep slope under undisturbed forest (23.7 kg C m-2). On gentle slopes, the effect of deforestation on SOC stocks was not so drastic (14.3 and 14.4 kg C m-2). Therefore, contrasting topography generates different patterns of SOC redistribution in the catchment. The effect of conversion to cropland is probably due to soil redistribution by water and tillage erosion aggravated by the steep terrain. Secondly, in order to assess the heterogeneity of SOC distribution at catchment scale, samples were collected at 10-20; 40-50 and 75-85 cm in 167 soil profiles sampled with an auger. SOC concentrations (gC kg-1 ) in numerous bulk soil samples (n = 378) were predicted by VIS-NIR spectroscopy and partial least-square regression models. SOC stocks were assessed by a mass preserving spline tool by interpolating SOC mass at the three non-contiguous depth intervals. Samples of calibration-validation dataset (n = 95) were used for physical SOC fractionation allowing the measurement of carbon associated with < 20 μm fraction. Multivariate linear regression models and Pearson correlation coefficients were used to assess the influence of

  13. Unusually low carbon isotope ratios in plants from hanging gardens in southern Utah.

    PubMed

    Flanagan, Lawrence B; Cook, Craig S; Ehleringer, James R

    1997-08-01

    Leaf carbon isotope ratios (δ(13)C) and photosynthetic gas exchange were measured on plants growing in hanging garden communities in southern Utah, USA. Hanging gardens are unusual, mesic cliff communities occurring where water seeps from the sandstone bedrock in an otherwise extremely arid region; there is very limited overlap in species distributions inside and outside these gardens. Solar exposure in hanging gardens varied with orientation and one of the gardens (Ribbon Garden) was shaded throughout the day. The leaf δ(13)C values of plants in hanging gardens were significantly more negative than for plants from either nearby ephemeral wash or riparian communities. In Ribbon Garden, the observed δ(13)C values were as low as -34.8‰, placing them among the most negative values reported for any terrestrial plant species growing in a natural environment. Hanging garden plants were exposed to normal atmospheric CO2 with an average δ(13)C value of -7.9‰ and so the low leaf δ(13)C values could not be attributed to exposure to a CO2 source with low (13)C content. There was a seasonal change toward more negative leaf δ(13)C values at the end of the growing season. The observed leaf δ(13)C values were consistent with photosynthetic gas exchange measurements that indicated unusually high leaf intercellular CO2 concentrations associated with the relatively low light levels in hanging gardens. Thus, extremely negative leaf δ(13)C values would be expected if significant amounts of the seasonal carbon gain occur at light levels low enough to be near the light compensation point. Maximum observed photosynthetic rates varied with light levels at each of the gardens, with maximum rates averaging 20.3, 14.6, and 3.1 μmol m(-2 )s(-1) at Double Garden, Lost Garden, and Ribbon Garden, respectively. Leaf nitrogen contents averaged 18.5 mg g(-1) in species from the more shaded hanging gardens (Lost and Ribbon). When expressed on a leaf area basis, nitrogen contents

  14. Soil Carbon and Nutrient Changes Associated with Deforestation for Pasture in Southern Costa Rica

    NASA Technical Reports Server (NTRS)

    Huth, Timothy J.; Porder, Stephen; Chaves, Joaquin; Whiteside, Jessica H.

    2012-01-01

    We assessed the effects of deforestation on soil carbon (C) and nutrient stocks in the premontane landscape near Las Cruces Biological Station in southern Costa Rica, where forests were cleared for pasture in the mid-1960s. We excavated six soil pits to a depth of 1 m in both pasture and primary forest, and found that C stocks were 20 kg C per square meters in both settings. Nevertheless, soil delta C-13 suggests 50 percent of the forest-derived soil C above 40 cm depth has turned over since deforestation. Soil nitrogen (N) and phosphorus (P) stocks derived from the soil pits were not significantly different between land uses (P = 0.43 and 0.61, respectively). At a larger spatial scale, however, the ubiquity of ruts produced by cattle-induced erosion indicates that there are substantial soil effects of grazing in this steep landscape. Ruts averaged 13 cm deep and covered 45 percent of the landscape, and thus are evidence of the removal of 0.7 Mg C/ ha/yr, and 70, 9 and 40 kg/ha/yr of N, P and potassium (K), respectively. Subsoils in this region are 10 times less C- and N-rich, and 2 times less P- and K-rich than the topsoil. Thus, rapid topsoil loss may lead to a decline in pasture productivity in the coming decades. These data also suggest that the soil C footprint of deforestation in this landscape may be determined by the fate of soil C as it is transported downstream, rather than C turnover in situ.

  15. A carbon budget for a naturally iron fertilized bloom in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Morris, Paul J.; Sanders, Richard

    2011-09-01

    Subantarctic islands in the high-nutrient, low-chlorophyll (HNLC) Southern Ocean are natural sources of iron and stimulate blooms in their proximity, such as the one observed close to the Crozet Islands (52°E, 46°S). During 2004/2005, particulate organic carbon (POC) export was measured using the 234Th technique in the Crozet bloom and compared with an HNLC control region. Initial results showed that iron release had no effect on daily POC export rates, thus any iron-driven enhancement in POC export was due to a longer export phase in the bloom region when compared to the control region. The duration of the export event was empirically estimated by closing the silicon budget, thus allowing seasonal POC export to be calculated by applying the export duration to the daily rates of POC export. This yields a seasonal estimate of POC export that is 3.6 times larger (range 1.9-7.1) in the iron-fertilized region than in the HNLC control region. These estimates of POC export were then compared to independent estimates of organic matter storage in the upper ocean, which are significant in both the HNLC and control regions. Overall, integrated POC export was significantly (approximately 50%) lower than estimated seasonal new production, the fraction of production that is supported by inputs of new nutrients. Finally, the sequestration efficiency, the numerical relationship between the supply of the limiting nutrient, iron, and the key ecosystem function of POC export at 100 m, is estimated to be 16,790 mol:mol.

  16. Reconstruction of Holocene carbon dynamics in a large boreal peatland complex, southern Finland

    NASA Astrophysics Data System (ADS)

    Mathijssen, Paul J. H.; Väliranta, Minna; Korrensalo, Aino; Alekseychik, Pavel; Vesala, Timo; Rinne, Janne; Tuittila, Eeva-Stiina

    2016-06-01

    Holocene peatland development and associated carbon (C) dynamics were reconstructed for a southern boreal Finnish peatland complex with fen and bog areas. In order to assess the role of local factors and long-term allogenic climate forcing in peatland development patterns, we studied a total of 18 peat cores and reconstructed vertical peat growth and lateral peat area expansion rates, the C accumulation rate (CAR), past vegetation composition and past methane (CH4) fluxes. We combined fossil plant data with measured contemporary CH4 flux - vegetation relationship data to reconstruct CH4 fluxes over time. When these reconstructions were added to the CAR estimations, a more complete picture of Holocene-scale C dynamics was achieved. Basal peat ages showed that expansion of the peat area was rapid between 11,000 and 8000 cal. BP, but decreased during the dry mid-Holocene and is probably currently limited by basal topography. A similar pattern was observed for peat growth and CAR in the fen core, whereas in the bog core CAR increased after ombrotrophication, i.e. after 4400 cal. BP. The effect of fire on vegetation and CAR was more conspicuous at the bog site than at the fen site. The CH4 flux reconstructions showed that during the Holocene CH4 emissions at the fen site decreased from 19 ± 15 to 16 ± 8 g CH4 m-2 yr-1 and at the bog site from 20 ± 15 to 14 ± 8 g CH4 m-2 yr-1. Our results suggest that a combination of changing climate, fire events and local conditions have modified the autogenic peatland development and C dynamics.

  17. The macroalgal carbonate factory at a cool-to-warm temperate marine transition, Southern Australia

    NASA Astrophysics Data System (ADS)

    James, Noel P.; Reid, Catherine M.; Bone, Yvonne; Levings, Andrew; Malcolm, Isabelle

    2013-06-01

    The shallow neritic seafloor to depths of ~ 30 m along the coast of southwestern Victoria Australia, is the site of rocky reefs on volcanic and aeolianite bathymetric highs. The region, located near the warm- to cool-temperate environmental transition, is a site of prolific macroalgae (kelp) growth. Kelps are most prolific and diverse in high-energy, open-ocean environments whereas broad-leafed seagrasses, at their cold-water eastern limit, are restricted to local protected embayments. The seagrasses are reduced to one species of Amphibolis whereas the kelps are diverse and include the large intertidal bull kelp (Durvillaea), not present in warmer waters. The macroalgal forest extends from the intertidal to ~ 30 mwd (metres water depth) as a series of distinct biomes; 1) the Peritidal, 2) the Phaeophyte Forest (0-17 mwd), 3) the Rhodophyte Thicket (17-15 mwd), and 4) the Invertebrate Coppice (> 25 mwd). The Phaeophyte Forest is partitioned into a Durvillaea zone (0-2 mwd), a Phyllospora zone (2-10 mwd) and an Ecklonia zone (10-17mwd). The two major habitats within each biome comprise 1) an upward facing illuminated surface that supports a macroalgal canopy over an understorey of coralline algae and herbivorous gastropods, and 2) a separate, cryptic, shaded habitat dominated by a diverse community of filter-feeding invertebrates. These communities produce two different sediments; 1) geniculate and encrusting corallines and diverse gastropods from the upper surface, and 2) bryozoans, molluscs, barnacles, chitons, serpulids, and benthic foraminifers from the shaded, cryptic habitats. These particles are blended together with the latter becoming proportionally more abundant with increasing depth. Results of this study, when integrated with recent investigations in warm-temperate (South Australia) and cool-temperate (New Zealand) environments now define carbonate sedimentology of the macroalgal reef depositional system in this part of the northern Southern Ocean.

  18. Short-term favorable weather conditions are an important control of interannual variability in carbon and water fluxes

    Treesearch

    Jakob Zscheischler; Simone Fatichi; Sebastian Wolf; Peter D. Blanken; Gil Bohrer; Ken Clark; Ankur R. Desai; David Hollinger; Trevor Keenan; Kimberly A. Novick; Sonia I. Seneviratne

    2016-01-01

    Ecosystem models often perform poorly in reproducing interannual variability in carbon and water fluxes, resulting in considerable uncertainty when estimating the land-carbon sink. While many aggregated variables (growing season length, seasonal precipitation, or temperature) have been suggested as predictors for interannual variability in carbon fluxes, their...

  19. Assessment of weather-associated causes of red spruce winter injury and consequences to aboveground carbon sequestration

    Treesearch

    Paul G. Schaberg; Brynne E. Lazarus; Gary J. Hawley; Joshua M. Halman; Catherine H. Borer; Christopher F. Hansen

    2011-01-01

    Despite considerable study, it remains uncertain what environmental factors contribute to red spruce (Picea rubens Sarg.) foliar winter injury and how much this injury influences tree C stores. We used a long-term record of winter injury in a plantation in New Hampshire and conducted stepwise linear regression analyses with local weather and regional...

  20. Simulating carbon capture by enhanced weathering with croplands: an overview of key processes highlighting areas of future model development

    PubMed Central

    Quegan, Shaun; Banwart, Steven A.

    2017-01-01

    Enhanced weathering (EW) aims to amplify a natural sink for CO2 by incorporating powdered silicate rock with high reactive surface area into agricultural soils. The goal is to achieve rapid dissolution of minerals and release of alkalinity with accompanying dissolution of CO2 into soils and drainage waters. EW could counteract phosphorus limitation and greenhouse gas (GHG) emissions in tropical soils, and soil acidification, a common agricultural problem studied with numerical process models over several decades. Here, we review the processes leading to soil acidification in croplands and how the soil weathering CO2 sink is represented in models. Mathematical models capturing the dominant processes and human interventions governing cropland soil chemistry and GHG emissions neglect weathering, while most weathering models neglect agricultural processes. We discuss current approaches to modelling EW and highlight several classes of model having the potential to simulate EW in croplands. Finally, we argue for further integration of process knowledge in mathematical models to capture feedbacks affecting both longer-term CO2 consumption and crop growth and yields. PMID:28381633

  1. Simulating carbon capture by enhanced weathering with croplands: an overview of key processes highlighting areas of future model development.

    PubMed

    Taylor, Lyla L; Beerling, David J; Quegan, Shaun; Banwart, Steven A

    2017-04-01

    Enhanced weathering (EW) aims to amplify a natural sink for CO2 by incorporating powdered silicate rock with high reactive surface area into agricultural soils. The goal is to achieve rapid dissolution of minerals and release of alkalinity with accompanying dissolution of CO2 into soils and drainage waters. EW could counteract phosphorus limitation and greenhouse gas (GHG) emissions in tropical soils, and soil acidification, a common agricultural problem studied with numerical process models over several decades. Here, we review the processes leading to soil acidification in croplands and how the soil weathering CO2 sink is represented in models. Mathematical models capturing the dominant processes and human interventions governing cropland soil chemistry and GHG emissions neglect weathering, while most weathering models neglect agricultural processes. We discuss current approaches to modelling EW and highlight several classes of model having the potential to simulate EW in croplands. Finally, we argue for further integration of process knowledge in mathematical models to capture feedbacks affecting both longer-term CO2 consumption and crop growth and yields. © 2017 The Authors.

  2. Carbon stocks and greenhouse gas balance of an old-growth forest and an anthropogenic peatland in southern Chile

    NASA Astrophysics Data System (ADS)

    Perez-Quezada, J. F.; Brito, C. E.; Valdés, A.; Urrutia, P.

    2016-12-01

    Few studies have reported the effects of deforestation on carbon stocks and greenhouse gas balance in the temperate forests of the southern hemisphere. In some areas of southern Chile, after clear-cut or forest fires occurs a proliferation of Sphagnum moss, generating an anthropogenic type of peatland. We measured the effects of this change on the carbon stocks and the greenhouse gas balance, starting in 2013. Carbon stocks were measured in >30 plots on each site; ecosystem CO2 fluxes were measured continuously using eddy covariance stations; CH4 and N2O fluxes were measured monthly using closed chambers and cavity ring-down spectroscopy technology. Total ecosystem carbon stock was 1,523 Mg ha-1 in the forest and 130 Mg ha-1 in the peatland, representing a 91% difference. Both land use types were found to act as sinks of CO2 (NEE=-1094.2 and -31.9 g CO2 m-2 year-¹ for the forest and peatland, respectively); CH4 was mainly captured in the forest and peatland soils, generating balances of -0.70 and -0.12 g CH₄ m-2 year-¹. N2O fluxes were extremely low, so were considered as null. These results indicate that the greenhouse gas balance moved from -1134.6 to -38.8 g CO2-eq m-2 year-1 when land use changed from forest to anthropogenic peatland. These results provide evidence of the importance of preserving old-growth forests in southern Chile.

  3. A Sensitivity-Based Approach to Quantifying the Costs of Weather and Climate Impacts: A Case Study of the Southern Pennsylvania Transportation Authority Adaptation Pilot Project

    NASA Astrophysics Data System (ADS)

    Casola, J.; Johanson, E.; Groth, P.; Snow, C.; Choate, A.

    2012-12-01

    Southeastern Pennsylvania Transportation Authority (SEPTA), with support from the Federal Transit Administration, has been investigating its agency's vulnerability to weather-related disruption and damages as a way to inform an overall adaptation strategy for climate variability and change. Exploiting daily rail service records maintained by SEPTA and observations from nearby weather stations, we have developed a methodology for quantifying the sensitivity of SEPTA's Manayunk/Norristown rail line to various weather events (e.g., snow storms, heat waves, heavy rainfall and flooding, tropical storms). For each type of event, sensitivity is equated to the frequency and extent of service disruptions associated with the event, and includes the identification of thresholds beyond which impacts are observed. In addition, we have estimated the monetary costs associated with repair and replacement of infrastructure following these events. Our results have facilitated discussions with SEPTA operational staff, who have outlined the institutional aspects of their preparation and response processes for these weather events. We envision the methodology as being useful for resource and infrastructure managers across the public and private sector, and potentially scalable to smaller or larger operations. There are several advantageous aspects of the method: 1) the quantification of sensitivity, and the coupling of that sensitivity to cost information, provides credible input to SEPTA decision-makers as they establish the priorities and level of investment associated with their adaptation actions for addressing extreme weather; 2) the method provides a conceptual foundation for estimating the magnitude, frequency, and costs of potential future impacts at a local scale, especially with regard to heat waves; 3) the sensitivity information serves as an excellent discussion tool, enabling further research and information gathering about institutional relationships and procedures. These

  4. Organic carbon fluxes in the Atlantic and the Southern Ocean: relationship to primary production compiled from satellite radiometer data

    NASA Astrophysics Data System (ADS)

    Fischer, G.; Ratmeyer, V.; Wefer, G.

    Fluxes of organic carbon normalised to a depth of 1000 m from 18 sites in the Atlantic and the Southern Ocean are presented, comprising nine biogeochemical provinces as defined by Longhurst et al. (1995. Journal of Plankton Research 17, 1245-1271). For comparison with primary production, we used a recent compilation of primary production values derived from CZCS data (Antoine et al., 1996. Global Biogeochemical Cycles 10, 57-69). In most cases, the seasonal patterns stood reasonably well in accordance with the carbon fluxes. Particularly, organic carbon flux records from two coastal sites off northwest and southwest Africa displayed a more distinct correlation to the primary production in sectors (1×1°) which are situated closer to the coastal environments. This was primarily caused by large upwelling filaments streaming far offshore, resulting in a cross-shelf carbon transport. With respect to primary production, organic carbon export to a water depth of 1000 m, and the fraction of primary production exported to a depth of 1000 m (export fraction=EF 1000), we were able to distinguish between: (1) the coastal environments with highest values (EF 1000=1.75-2.0%), (2) the eastern equatorial upwelling area with moderately high values (EF 1000=0.8-1.1%), (3) and the subtropical oligotrophic gyres that yielded lowest values (EF 1000=0.6%). Carbon export in the Southern Ocean was low to moderate, and the EF 1000 value seems to be quite low in general. Annual organic carbon fluxes were proportional to primary production, and the export fraction EF 1000 increased with primary production up to 350 gC m -2 yr-1. Latitudinal variations in primary production were reflected in the carbon flux pattern. A high temporal variability of primary production rates and a pronounced seasonality of carbon export were observed in the polar environments, in particular in coastal domains, although primary production (according to Antoine et al., 1996. Global Biogeochemical Cycles 10, 57

  5. Sustainability of forest management under changing climatic conditions in the southern United States: adaptation strategies, economic rents and carbon sequestration.

    PubMed

    Susaeta, Andres; Carter, Douglas R; Adams, Damian C

    2014-06-15

    The impacts of climate change on profitability and carbon storage in even-aged forest stands of two dominant commercial pine species, loblolly and slash pine, in the southern United States were assessed under alternative assumptions about the impact of climate change on forest productivity and catastrophic disturbance rates. Potential adaptation strategies to reduce losses from disturbance included: 1) alternative planting densities, and 2) planting slash pine instead of loblolly pine. In addition, the amount of sequestered carbon was used to develop an index of economic efficiency for carbon sequestration, which further helps rank the suitability of alternative adaptation strategies. Our results indicate that greater economic rents from forests occur with lower planting densities and the substitution of slash pine for high density loblolly pine. However, less carbon is sequestered by low density loblolly pine compared to slash pine and high density loblolly pine. Both adaptation strategies are economically more effective in terms of carbon sequestration compared to the baseline since they generate more economic revenues per Mg of sequestered carbon. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Deep-water carbonate slope failure events in a newly discovered Silurian basin, Blue Ridge province, southern Appalachians, Tennessee

    SciTech Connect

    Unrug, R. )

    1991-03-01

    Siliciclastic deep-water turbidites of the Walden Creek Group, Ocoee Supergroup, underlying the foothills of the Great Smoky Mountains, contain olistolith blocks and olistostromal debris-flow breccia beds. Paleozoic fossils discovered recently in the olistoliths indicate Silurian age of the carbonates. The Walden Creek Group is therefore Silurian or younger, not late Proterozoic in age, as believed previously. The carbonate olistoliths and breccias formed by collapse of post-Taconic Silurian carbonate-dominated basin present in the Blue Ridge province of the Southern Appalachians into the younger basin of the Walden Creek Group. Two modes of occurrence of the olistoliths are present: (1) discrete horizons in which olistoliths are sitting spaced ten to hundreds of meters apart underneath a widespread conglomerate bed and (2) accumulations of olistoliths in localized stacked horizons in the vertical sequence of the enclosing siliciclastic rocks. Both modes can be related to failure of active fault scarps. Rocks of the olistolith are lithologically varied and record an older event of slope failure within the Silurian carbonate-dominated basin. Three facies assemblages representing two sedimentary environments are present in the olistoliths. Facies assemblage A includes oolitic limestone, stromatolite, carbonate breccia encrusted by stromatolite, and massive sandy limestone. It represents a high-energy, shallow-water, carbonate platform environment. Facies assemblage B consists of bedded dark limestone, alternating with black shale, and represents sediments of the carbonate platform slope. Facies assemblage C includes carbonate breccias intercalated in the bedded limestones and shales and is interpreted as deposits of the lower slope formed by failure of the carbonate platform margin.

  7. Types of secondary porosity of carbonate rocks in injection and test wells in southern peninsular Florida

    USGS Publications Warehouse

    Duerr, A.D.

    1995-01-01

    The types of secondary porosity present in carbonate injection intervals and in the overlying carbonate rocks were determined at 11 injection well sites and 3 test well sites in southern peninsular Florida. The hydrogeologic system consists of a thick sequence of carbonate rocks overlain by clastic deposits. Principal hydrogeologic units are the surficial aquifer system, the intermediate aquifer system or the intermediate confining unit,the Floridan aquifer system, and the sub-Floridan confining unit.The concept of apparent secondary porosity was used in this study because the secondary porosity features observed in a borehole television survey could have been caused by geologic processes as well as by drilling activities. The secondary porosity features identified in a television survey were evaluated using driller's comments and caliper, flowmeter, and temperature logs. Borehole intervals that produced or received detectable amounts of flow, as shown by flowmeter and temperature logs, provided evidence that the secondary porosity of the interval was spatially distributed and interconnected beyond the immediate vicinity of a borehole and, thus, was related to geologic processes. Features associated with interconnected secondary porosity were identified as effective secondary porosity. Fracture porosity was identified as the most common type of effective secondary porosity and was observed predominantly in dolomite and dolomitic limestone. Cavity porosity was the least common type of effective secondary porosity at the study sites. In fact, of the more than 17,500 feet of borehole studied a total of only three cavities constituting effective secondary porosity were identified at only two sites. These cavities were detected in dolomite rocks. Most apparent cavities were caused by drilling-induced collapse of naturally fractured borehole walls. Also, fractures usually were observed above and below cavities. The majority of vugs observed in the television surveys did

  8. Interactions between phytoplankton organisms and key carbonate system properties in the southern Adriatic Sea: seasonal variability within an annual cycle

    NASA Astrophysics Data System (ADS)

    Luchetta, Anna; Boldrin, Alfredo; Langone, Leonardo; Socal, Giorgio; Bernardi Aubry, Fabrizio; Cantoni, Carolina

    2013-04-01

    Although the impact of CO2 uptake on ocean chemistry has been recognizing for the last decades, ocean acidification has emerged as a key issue of global concern in less than a decade. Studies of the impacts on marine organisms, ecosystems and biogeochemical processes are only at the beginning and the results are still contrasting. In open sea, the pool of particulate organic carbon is mainly determined by phytoplankton production (controlled by light and nutrient availabilities). However pH and key carbonate system properties (AT, DIC, calcium carbonate saturation states), influencing phytoplankton population and communities can play a fundamental role in determining the autothrophic production and its cycle. In the perspective of lighting possible impacts of climatic changes on natural phytoplankton communities of the Southern Adriatic open sea region, this contribute describes the relationships between pH/carbonate system and the phytoplankton during almost one year (Sept 2007-June 2008), with particular regard to calcareous phytoplankton. A few seasonal campaigns were conducted within the frame of the Italian VECTOR project, on a repeated section from Bari to Dubrovnik. The dynamics of phytoplankton community have been analyzed considering the export of particulate organic matter from the photic layer (collected in sediment traps at 150 m). The phytoplankton cycle from September 07 to late June 08 was determined analysing samples collected from CTD bottles. It appears to be characterized by short time blooms of different groups: in autumn the main component (62%) was represented by siliceous plankton (diatoms), in late winter calcareous plankton (coccolithophores) reached 31% of total biomass, whereas flagellates appeared the dominant group (84%) during summer. Downward fluxes of organic carbon (at 150 m), strictly depending on the upper layer autotrophic activity, were well correlated with carbonate fluxes. A succession of different dominant productive groups

  9. The conservative behavior of dissolved organic carbon in surface waters of the southern Chukchi Sea, Arctic Ocean, during early summer

    PubMed Central

    Tanaka, Kazuki; Takesue, Nobuyuki; Nishioka, Jun; Kondo, Yoshiko; Ooki, Atsushi; Kuma, Kenshi; Hirawake, Toru; Yamashita, Youhei

    2016-01-01

    The spatial distribution of dissolved organic carbon (DOC) concentrations and the optical properties of dissolved organic matter (DOM) determined by ultraviolet-visible absorbance and fluorescence spectroscopy were measured in surface waters of the southern Chukchi Sea, western Arctic Ocean, during the early summer of 2013. Neither the DOC concentration nor the optical parameters of the DOM correlated with salinity. Principal component analysis using the DOM optical parameters clearly separated the DOM sources. A significant linear relationship was evident between the DOC and the principal component score for specific water masses, indicating that a high DOC level was related to a terrigenous source, whereas a low DOC level was related to a marine source. Relationships between the DOC and the principal component scores of the surface waters of the southern Chukchi Sea implied that the major factor controlling the distribution of DOC concentrations was the mixing of plural water masses rather than local production and degradation. PMID:27658444

  10. The conservative behavior of dissolved organic carbon in surface waters of the southern Chukchi Sea, Arctic Ocean, during early summer.

    PubMed

    Tanaka, Kazuki; Takesue, Nobuyuki; Nishioka, Jun; Kondo, Yoshiko; Ooki, Atsushi; Kuma, Kenshi; Hirawake, Toru; Yamashita, Youhei

    2016-09-23

    The spatial distribution of dissolved organic carbon (DOC) concentrations and the optical properties of dissolved organic matter (DOM) determined by ultraviolet-visible absorbance and fluorescence spectroscopy were measured in surface waters of the southern Chukchi Sea, western Arctic Ocean, during the early summer of 2013. Neither the DOC concentration nor the optical parameters of the DOM correlated with salinity. Principal component analysis using the DOM optical parameters clearly separated the DOM sources. A significant linear relationship was evident between the DOC and the principal component score for specific water masses, indicating that a high DOC level was related to a terrigenous source, whereas a low DOC level was related to a marine source. Relationships between the DOC and the principal component scores of the surface waters of the southern Chukchi Sea implied that the major factor controlling the distribution of DOC concentrations was the mixing of plural water masses rather than local production and degradation.

  11. Vertical Water Mass Structure of the Southern Ocean Inferred From Neodymium Isotopes: Implications for Organic Carbon Burial

    NASA Astrophysics Data System (ADS)

    Martin, E. E.; Scher, H. D.

    2006-12-01

    Neodymium isotope records from the Atlantic sector of the Southern Ocean have documented first order changes in ocean circulation, such as Pacific throughflow following the early opening of Drake Passage, initiation of deep water export from the North Atlantic, and intensification of the Antarctic Circumpolar Current (ACC). These studies have shed light on changes in deep water circulation and production areas, however the impact of these changes on the vertical structure of the Southern Ocean is has not been explored. We investigated the middle Eocene to early Miocene sections of three vertically and horizontally offset Ocean Drilling Program (ODP) sites in the Atlantic sector of the Southern Ocean (ODP Sites 689 (upper Maud Rise; paleodepth 1500 m), 690 (lower Maud Rise; paleodepth 2200 m), and 1090 (Agulhas Ridge; paleodepth 3700). Nd isotope records were generated from fossil fish teeth covering the interval from 45 to 25 Ma. Our goal was to investigate changes in the vertical water mass structure of the Atlantic sector of the Southern Ocean. The vertical water mass structure of the Southern Ocean has been influenced by the development of the ACC, which is believed to have exerted an important control on the relationship between opal deposition and organic carbon burial in this region. Thus, this work is relevant for assessing the mechanisms thought to be responsible for the draw down of atmospheric carbon dioxide, an important factor in global climate change over this interval. During the middle Eocene, around 42 Ma, the ɛNd gradient between intermediate and deep waters in the Atlantic sector was about 1 ɛNd unit. ɛNd values at Maud Rise were -9.2 and - 9.5 (Sites 689 and 690 respectively), while ɛNd values at Agulhas Ridge were -8.5. Between 41 and 35 Ma ɛNd values at all three locations became more radiogenic as Pacific seawater entered the Atlantic following the early opening of Drake Passage. Agulhas Ridge ɛNd values increased to -6, and values at

  12. Redistribution of forest carbon caused by patch blowdowns in subalpine forests of the Southern Rocky Mountains, USA

    NASA Astrophysics Data System (ADS)

    Wohl, Ellen

    2013-12-01

    blowdowns varying in size from 0.1 to 33 ha affected several areas in Rocky Mountain National Park, Colorado, USA, during the winter of 2011-2012. These blowdowns resulted in substantial redistribution of forest carbon by snapping and uprooting trees, thereby increasing instream wood recruitment, recruitment of dead wood to the forest floor, and exposure of organic soil on uprooted tree plates. Estimates of carbon redistribution at five sites in Rocky Mountain National Park range as high as 308 Mg C/ha in high-severity patches to 106 Mg C/ha in low-severity patches, of which typically 10-30% is soil C and the remainder is downed wood. Masses of carbon redistributed from living to dead biomass at high-severity sites represent a substantial portion of average total biomass in old-growth subalpine forests in the region. Consequently, the potential for increasing frequency and/or severity of blowdowns under a warming climate represents a significant potential source of terrestrial carbon to the atmosphere. The majority of this carbon is in the form of downed wood that becomes a carbon source to the atmosphere, although interactions between downed wood and river processes can locally increase carbon storage in floodplain soil. Predictions of changes in precipitation and wind patterns, and associated changes in wildfire and insect infestation, suggest that blowdowns may become more common in future in the Southern Rockies, but the consequences for carbon dynamics depend on site-specific interactions between blowdowns and other processes such as floodplain storage of organic matter.

  13. Chemical and Biological Catalytic Enhancement of Weathering of Silicate Minerals and industrial wastes as a Novel Carbon Capture and Storage Technology

    NASA Astrophysics Data System (ADS)

    Park, A. H. A.

    2014-12-01

    Increasing concentration of CO2 in the atmosphere is attributed to rising consumption of fossil fuels around the world. The development of solutions to reduce CO2 emissions to the atmosphere is one of the most urgent needs of today's society. One of the most stable and long-term solutions for storing CO2 is via carbon mineralization, where minerals containing metal oxides of Ca or Mg are reacted with CO2 to produce thermodynamically stable Ca- and Mg-carbonates that are insoluble in water. Carbon mineralization can be carried out in-situ or ex-situ. In the case of in-situ mineralization, the degree of carbonation is thought to be limited by both mineral dissolution and carbonate precipitation reaction kinetics, and must be well understood to predict the ultimate fate of CO2 within geological reservoirs. While the kinetics of in-situ mineral trapping via carbonation is naturally slow, it can be enhanced at high temperature and high partial pressure of CO2. The addition of weak organic acids produced from food waste has also been shown to enhance mineral weathering kinetics. In the case of the ex-situ carbon mineralization, the role of these ligand-bearing organic acids can be further amplified for silicate mineral dissolution. Unfortunately, high mineral dissolution rates often lead to the formation of a silica-rich passivation layer on the surface of silicate minerals. Thus, the use of novel solvent mixture that allows chemically catalyzed removal of this passivation layer during enhanced Mg-leaching surface reaction has been proposed and demonstrated. Furthermore, an engineered biological catalyst, carbonic anhydrase, has been developed and evaluated to accelerate the hydration of CO2, which is another potentially rate-limiting step of the carbonation reaction. The development of these novel catalytic reaction schemes has significantly improved the overall efficiency and sustainability of in-situ and ex-situ mineral carbonation technologies and allowed direct

  14. Assessing Actual and Potential Organic Carbon Pools in Southern Taiga and Forest-Steppe Ecosystems of Russia

    NASA Astrophysics Data System (ADS)

    Chernova, Olga; Ryzhova, Irina; Podvezennaya, Marina

    2014-05-01

    Recent debates on climate changes showed the importance of maintaining natural cycles of nutrients and preserving extensive areas of natural ecosystems to ensure sustainability of the biosphere. The size and distribution of nutrient pools within ecosystems are the key characteristics of the biological cycle reflecting changes in the functioning of natural systems. Carbon pools assessed in similar land-use types by different researchers are often poorly comparable due to various calculation algorithms, sampling techniques and sets of field data used. Model-based assessments often yield results that significantly depart from calculations based on actual field data. We estimated the actual and potential natural carbon pools using potential natural vegetation maps, soil maps, up-to-date statistics and results of regional studies. Organic carbon pools in biomass, forest litter, peat and soil were calculated for most typical natural (ecosystems, which experienced the least effect of historic land use) and modern ecosystems for two administrative regions of Russia: 1. Kursk region characterized by high productive natural steppe vegetation with predominance of chernozems - the country's most fertile soils, which were extensively transformed by agricultural activity; 2. Kostroma region, sparsely populated area with still abundant southern taiga forests. The average characteristics of vegetation productivity for natural and some human-modified ecosystems such as coniferous (pine, spruce) and noble broadleaf (oak, linden) forests, swamps, bogs, steppes, bottomland meadows, secondary forests, hayfields, pastures were calculated using the Database on the Productivity of Ecosystems in North Eurasia. The biological productivity of present-day forests and carbon pools in biomass were calculated using the program for assessing forest carbon budget (ROBUL model). Similar characteristics were used for agricultural areas. They were averaged according to crop rotations and recalculated

  15. The CO2 consumption potential during gray shale weathering: Insights from the evolution of carbon isotopes in the Susquehanna Shale Hills critical zone observatory

    NASA Astrophysics Data System (ADS)

    Jin, Lixin; Ogrinc, Nives; Yesavage, Tiffany; Hasenmueller, Elizabeth A.; Ma, Lin; Sullivan, Pamela L.; Kaye, Jason; Duffy, Christopher; Brantley, Susan L.

    2014-10-01

    Shale covers about 25% of the land surface, and is therefore an important rock type that consumes CO2 during weathering. We evaluated the potential of gray shale to take up CO2 from the atmosphere by investigating the evolution of dissolved inorganic carbon (DIC) concentrations and its carbon isotopic ratio (δ13CDIC) along water flow paths in a well-characterized critical zone observatory (Susquehanna Shale Hills catchment). In this catchment, chemical weathering in shallow soils is dominated by clay transformation as no carbonates are present, and soil pore waters are characterized by low DIC and pH. In shallow soil porewaters, the DIC, dominated by dissolved CO2, is in chemical and isotopic equilibrium with CO2 in the soil atmosphere where pCO2 varies seasonally to as high as 40 times that of the atmosphere. The degradation of ancient organic matter is negligible in contributing to soil CO2. The chemistry of groundwater varies along different flowpaths as soil pore water recharges to the water table and then dissolves ankerite or secondary calcite under the valley floor. Weathering of carbonate leads to much higher concentrations of DIC (∼2500 μmol/L) and divalent cations (Ca2+ and Mg2+) in groundwaters than soil waters. The depth to the ankerite weathering front is hypothesized to be roughly coincident with the water table but it varies due to heterogeneities in the protolith composition. Groundwater chemistry therefore shows different saturation indices with respect to ankerite depending upon location along the valley. The δ13CDIC values of these groundwaters document mixing between the ankerite and soil CO2. The major element concentrations, DIC, and δ13CDIC in the first-order stream incising the valley of the catchment are derived from groundwater and soil waters in proportions that vary both spatially and temporally. The CO2 degassed slightly in the stream but little evidence of C isotopic equilibration with the atmosphere is observed, due to the short

  16. Seasonality of Leaf Carbon Isotopic Composition and Leaf Water Isotopic Enrichment in a Mixed Evergreen Forest in Southern California

    NASA Astrophysics Data System (ADS)

    Santiago, L. S.; Sickman, J. O.; Goulden, M.; DeVan, C.; Pasquini, S. C.; Pivovaroff, A. L.

    2011-12-01

    Leaf carbon isotopic composition and leaf water isotopic enrichment reflect physiological processes and are important for linking local and regional scale processes to global patterns. We investigated how seasonality affects the isotopic composition of bulk leaf carbon, leaf sugar carbon, and leaf water hydrogen under a Mediterranean climate. Leaf and stem samples were collected monthly from four tree species (Calocedrus decurrens, Pinus lambertiana, Pinus ponderosa, and Quercus chrysolepis) at the James San Jacinto Mountain Reserve in southern California. Mean monthly bulk leaf carbon isotopic composition varied from -34.5 % in P. ponderosa to -24.7 % in P. lambertiana and became more depleted in 13C from the spring to the summer. Mean monthly leaf sugar varied from -29.3 % in P. ponderosa to -21.8 % in P. lambertiana and was enriched in 13C during the winter, spring and autumn, but depleted during the mid-summer. Leaf water hydrogen isotopic composition was 28.4 to 68.8 % more enriched in deuterium than source water and this enrichment was greater as seasonal drought progressed. These data indicate that leaf carbon and leaf water hydrogen isotopic composition provide sensitive measures that connect plant physiological processes to short-term climatic variability.

  17. Modelling a strike-slip fault system affecting porous carbonates in Favignana Island (Sicily, southern Italy)

    NASA Astrophysics Data System (ADS)

    Cilona, A.; Tondi, E.; Agosta, F.; Johnson, G.; Shackleton, R.

    2012-12-01

    Investigating the deformation processes as well as the characteristics and distribution of their end-products is a crucial issue to improve geo-fluid exploitation in carbonate reservoirs (≈50% of natural geo-fluids). Indeed, besides the primary controls on the petrophysical properties of limestones, which are due to nature and organization/shape of the constituent elements (i.e. grains, pores, cement, clay minerals), both containment and migration of fluids in these rocks are influenced by fault zones and fractures. In this contribution we integrate quantitative structural analysis and numerical modelling approaches aiming at testing a new workflow useful to create a 3D discrete fracture network (DFN) model of a reservoir starting from outcrop data collected in Favignana Island (Sicily, southern Italy). The presence of several quarries in the Island provides 3D exposures of ≈25 m-thick Lower-Pleistocene high-porosity grainstones crosscut by two conjugate sets of strike-slip faults. This fault system, documented by Tondi et al. (2012), is comprised of three types of structure: single compactive shear bands (CSB); zones of bands (ZB); and, faults. CSBs are narrow tabular features with porosity less than the surrounding host rocks, and have thicknesses and displacements on the order of a few mm. The growth process for these structures involves localizing further deformation within zones of closely-spaced CSBs and, possibly, along continuous slip surfaces within fault rocks overprinting older ZBs. The transitions from one growth step to another are recorded by different values of the dimensional parameters (i.e. length, thickness and displacement) for the structures. These transitions are also reflected by the ratios and distributions of the dimensional parameters. The DFN model was built by means of the Fracture Modelling module of the commercial software package Move from Midland Valley©. The analysis of an aerial photo was performed firstly to delimit the

  18. Carbon-14 Measurements in Atmospheric CO2 from Northern and Southern Hemisphere Sites, 1962-1993

    DOE Data Explorer

    Nydal, R.; Lovseth, K.

    1996-01-01

    In the 1960s, thermonuclear bomb tests released significant pulses of radioactive 14C into the atmosphere. This major perturbation allowed scientists to study the dynamics of the global carbon cycle by measuring and observing rates of isotopic exchange. The Radiological Dating Laboratory at the Norwegian Institute of Technology performed 14C measurements in atmospheric CO2 from 1962 to 1993 at a network of ground stations in the Northern and Southern hemispheres. These measurements were supplemented during 1965 with high-altitude (9-12.6 km) air samples collected using aircraft from the Norwegian Air Force. The resulting database, coupled with other 14C data sets, provides a greater understanding of the dynamic carbon reservoir and a crude picture of anomalous sources and sinks at different geographical latitudes. This database is outstanding for its inclusion of early 14C measurements, broad spatial coverage of sampling, consistency of sampling method, and 14C calculation results corrected for isotopic fractionation and radioactive decay. This database replaces previous versions published by the authors and the Radiological Dating Laboratory. Fourteen stations spanning latitudes from Spitsbergen (78° N) to Madagascar (21° S) were used for sampling during the lifetime of the Norwegian program. Some of the stations have data for only a brief period, while others have measurements through 1993. Sampling stations subject to local industrial CO2 contamination were avoided. The sites have sufficient separation to describe the latitudinal distribution of 14C in atmospheric models. The sampling procedure for all the surface (10-2400 m asl) 14C measurements in this database consisted of quantitative absorption of atmospheric CO2 in carbonate-free 0.5 N NaOH solution. The 14C measurements were made in a CO2 proportional counter and calculated (14C) as per mil excess above the normal 14C level