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1.
Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the coastal ocean? 总被引:1,自引:0,他引:1
Alberto V. Borges 《Estuaries and Coasts》2005,28(1):3-27
Annually integrated air-water CO2 flux data in 44 coastal environments were compiled from literature. Data were gathered in 8 major ecosystems (inner estuaries,
outer estuaries, whole estuarine systems, mangroves, salt marshes, coral reefs, upwelling systems, and open continental shelves),
and up-scaled in the first attempt to integrate air-water CO2 fluxes over the coastal ocean (26×106 km2), taking into account its geographical and ecological diversity. Air-water CO2 fluxes were then up-scaled in global ocean (362×106 km2) using the present estimates for the coastal ocean and those from Takahashi et al. (2002) for the open ocean (336×106 km2). If estuaries and salt marshes are not taken into consideration in the up-scaling, the coastal ocean behaves as a sink for
atmospheric CO2(−1.17 mol C m−2 yr−1) and the uptake of atmospheric CO2 by the global ocean increases by 24% (−1.93 versus −1.56 Pg C yr−1). The inclusion of the coastal ocean increases the estimates of CO2 uptake by the global ocean by 57% for high latitude areas (−0.44 versus −0.28 Pg C yr−1) and by 15% for temperate latitude areas (−2.36 versus −2.06 Pg C yr−1) At subtropical and tropical latitudes, the contribution from the coastal ocean increases the CO2 emission to the atmosphere from the global oceam by 13% (0.87 versus 0.77 Pg C yr−1). If estuaries and salt marshes are taken into consideration in the upscaling, the coastal ocean behaves as a source for
atmospheric CO2 (0.38 mol C m−2 yr−1) and the uptake of atmospheric CO2 from the global ocean decreases by 12% (−1.44 versus −1.56 Pg C yr−1) At high and subtropical and tropical latitudes, the coastal ocean behaves as a source for atmospheric CO2 but at temperate latitudes, it still behaves as a moderate CO2 sink. A rigorous up-scaling of air-water CO2 fluxes in the coastal ocean is hampered by the poorly constrained estimate of the surface area of inner estuaries. The present
estimates clearly indicate the significance of this biogeochemically, highly active region of the biosphere in the global
CO2 cycle. 相似文献
2.
The production of organic matter and calcium carbonate by a dense population of the brittle star Acrocnida brachiata (Echinodermata) was calculated using demographic structure, population density, and relations between the size (disk diameter)
and the ash-free dry weight (AFDW) or the calcimass. During a 2-year survey in the Bay of Seine (Eastern English Channel,
France), organic production varied from 29 to 50 gAFDW m−2 year−1 and CaCO3 production from 69 to 104 gCaCO3 m−2 year−1. Respiration was estimated between 1.7 and 2.0 molCO2 m−2 year−1. Using the molar ratio (ψ) of CO2 released: CaCO3 precipitated, this biogenic precipitation of calcium carbonate would result in an additional release between 0.5 and 0.7 molCO2 m−2 year−1 that represented 23% and 26% of total CO2 fluxes (sum of calcification and respiration). The results of the present study suggest that calcification in temperate shallow
environments should be considered as a significant source of CO2 to seawater and thus a potential source of CO2 to the atmosphere, emphasizing the important role of the biomineralization (estimated here) and dissolution (endoskeletons
of dead individuals) in the carbon budget of temperate coastal ecosystems. 相似文献
3.
Mangrove ecosystems play an important, but understudied, role in the cycling of carbon in tropical and subtropical coastal
ocean environments. In the present study, we examined the diel dynamics of seawater carbon dioxide (CO2) and dissolved oxygen (DO) for a mangrove-dominated marine ecosystem (Mangrove Bay) and an adjacent intracoastal waterway
(Ferry Reach) on the island of Bermuda. Spatial and temporal trends in seawater carbonate chemistry and associated variables
were assessed from direct measurements of dissolved inorganic carbon, total alkalinity, dissolved oxygen (DO), temperature,
and salinity. Diel pCO2 variability was interpolated across hourly wind speed measurements to determine variability in daily CO2 fluxes for the month of October 2007 in Bermuda. From these observations, we estimated rates of net sea to air CO2 exchange for these two coastal ecosystems at 59.8 ± 17.3 in Mangrove Bay and 5.5 ± 1.3 mmol m−2 d−1 in Ferry Reach. These results highlight the potential for large differences in carbonate system functioning and sea-air CO2 flux in adjacent coastal environments. In addition, observation of large diel variability in CO2 system parameters (e.g., mean pCO2: 390–2,841 μatm; mean pHT: 8.05–7.34) underscores the need for careful consideration of diel cycles in long-term sampling regimes and flux estimates. 相似文献
4.
Anne S. Marsh Daniel P. Rasse Bert G. Drake J. Patrick Megonigal 《Estuaries and Coasts》2005,28(5):694-704
The effects of long-term exposure to elevated atmospheric CO2 (ambient + 340 ppmv) on carbon cycling were investigated for two plant communities in a Chesapeake Bay brackish marsh, one
dominated by the C3 sedgeSchoenplectus americanus and the other by the C4 grassSpartina patens. Elevated CO2 resulted in a significant increase in porewater concentrations of DIC at 30 cm depth (p < 0.1). The CO2 treatment also yielded increases in DOC (15 to 27%) and dissolved CH4 (12–18%) in the C3 marsh (means for several depths over the period of June 1998 and June 1999), but not at a significant level. Elevated CO2 increased mean ecosystem emissions of CO2 (34–393 g C m−2 yr−1) and CH4 (0.21–0.40 g C m−2 yr−1) in the C3 community, but the effects were only significant on certain dates. For example, CO2 enrichment increased C export to the atmosphere in the C3 community during one of two winter seasons measured (p = 0.09). In the C4 community, gross photosynthesis responded relatively weakly to elevated CO2 (18% increase, p > 0.1), and the concomitant effects on dissolved carbon concentrations, respiration, and CH4 emissions were small or absent. We concluded that elevated CO2 has the potential to increase dissolved inorganic carbon export to estuaries. 相似文献
5.
This paper estimates CO2 fluxes in a municipal site for final disposal of solid waste, located in Gualeguaychu, Argentina. Estimations were made using
the accumulation chamber methods, which had been calibrated previously in laboratory. CO2 fluxes ranged from 31 to 331 g m−2 day−1. Three different populations were identified: background soil gases averaging 46 g m−2 day−1, intermediate anomalous values averaging 110 g m−2 day−1 and high anomalous values averaging 270 g m−2 day−1. Gas samples to a depth of 20 cm were also taken. Gas fractions, XCO2 < 0.1, XCH4 < 0.01, XN2 ~0.71 and XO2 ~0.21, δ13C of CO2 (−34 to −18‰), as well as age of waste emplacement, suggest that the study site may be at the final stage of aerobic biodegradation.
In a first approach, and following the downstream direction of groundwater flow, alkalinity and δ13C of dissolved inorganic carbon (−15 to 4‰) were observed to increase when groundwater passed through the disposal site. This
suggests that the CO2 generated by waste biodegradation dissolves or that dissolved organic matter appears as a result of leachate degradation. 相似文献
6.
Morgane Lejart Jacques Clavier Laurent Chauvaud Christian Hily 《Estuaries and Coasts》2012,35(2):622-632
Respiration and calcification rates of the Pacific oyster Crassostrea gigas were measured in a laboratory experiment in the air and underwater, accounting for seasonal variations and individual size,
to estimate the effects of this exotic species on annual carbon budgets in the Bay of Brest, France. Respiration and calcification
rates changed significantly with season and size. Mean underwater respiration rates, deducted from changes in dissolved inorganic
carbon (DIC), were 11.4 μmol DIC g−1 ash-free dry weight (AFDW) h−1 (standard deviation (SD), 4.6) and 32.3 μmol DIC g−1 AFDW h−1 (SD 4.1) for adults (80–110 mm shell length) and juveniles (30–60 mm), respectively. The mean daily contribution of C. gigas underwater respiration (with 14 h per day of immersion on average) to DIC averaged over the Bay of Brest population was 7.0 mmol DIC m−2 day−1 (SD 8.1). Mean aerial CO2 respiration rate, estimated using an infrared gas analyzer, was 0.7 μmol CO2 g−1 AFDW h−1 (SD 0.1) for adults and 1.1 μmol CO2 g−1 AFDW h−1 (SD 0.2) for juveniles, corresponding to a mean daily contribution of 0.4 mmol CO2 m−2 day−1 (SD 0.50) averaged over the Bay of Brest population (with 10 h per day of emersion on average). Mean CaCO3 uptake rates for adults and juveniles were 4.5 μmol CaCO3 g−1 AFDW h−1 (SD 1.7) and 46.9 μmol CaCO3 g−1 AFDW h−1 (SD 29.2), respectively. The mean daily contribution of net calcification in the Bay of Brest C. gigas population to CO2 fluxes during immersion was estimated to be 2.5 mmol CO2 m−2 day−1 (SD 2.9). Total carbon release by this C. gigas population was 39 g C m−2 year−1 and reached 334 g C m−2 year−1 for densely colonized areas with relative contributions by underwater respiration, net calcification, and aerial respiration
of 71%, 25%, and 4%, respectively. These observations emphasize the substantial influence of this invasive species on the
carbon cycle, including biogenic carbonate production, in coastal ecosystems. 相似文献
7.
Biogeochemistry of the Russian Arctic. Kara Sea: Research results under the SIRRO project, 1995–2003
E. M. Galimov L. A. Kodina O. V. Stepanets G. S. Korobeinik 《Geochemistry International》2006,44(11):1053-1104
The Kara Sea is an area uniquely suitable for studying processes in the river-sea system. This is a shallow sea into which
two great Siberian rivers, Yenisei and Ob, flow. From 1995 to 2003, the sea was studied by six international expeditions aboard
the R/V Akademik Boris Petrov. This publication summarizes the results obtained, within the framework of this project, at the Vernadsky Institute of Geochemistry
and Analytical Chemistry, Russian Academy of Sciences. Various hydrogeochemical parameters, concentrations and isotopic composition
of organic and carbonate carbon of the sediments, plankton, particulate organic matter, hydrocarbons, and dissolved CO2 were examined throughout the whole sea area at more than 200 sites. The δ13C varies from −22 and −24‰ where Atlantic waters enter the Kara Sea and in the North-eastern part of the water area to −27‰
in the Yenisei and Ob estuaries. The value of δ13C of the plankton is only weakly correlated with the δ13C of the organic matter from the sediments and is lower by as much as 3–4‰. The paper presents the results obtained from a
number of meridional river-sea profiles. It was determined from the relations between the isotopic compositions of plankton
and particulate matter that the riverwaters carry material consisting of 70% detrital-humus matter and 30% planktonogenic
material in the river part, and the material contained in the off-shore waters consists of 30% terrigenous components, with
the contribution of bioproducers amounting to 70%. The carbon isotopic composition of the plankton ranges from −29 to −35‰
in the riverine part, from −28 to −27‰ in the estuaries, and from −27.0 to −25% in the marine part. The relative lightness
of the carbon isotopic composition of plankton in Arctic waters is explained by the temperature effect, elevated CO2 concentrations, and long-distance CO2 supply to the sea with riverwaters. The data obtained on the isotopic composition of CO2 in the surface waters of the Kara Sea were used to map the distribution of δ13CCO
2. The complex of hydrocarbon gases extracted from the waters included methane, C2–C5, and unsaturated C2=–C4= hydrocarbons, for which variations in the concentrations in the waters were studied along river-estuary-sea profiles. The
geochemistry of hydrocarbon gases in surface fresh waters is characterized by comparable concentrations of methane (0.3–5
μl/l) and heavier hydrocarbons, including unsaturated ones. Microbiological methane with δ13C from −105 to −90‰ first occurs in the sediments at depths of 40–200 cm. The sediments practically everywhere display traces
of methane oxidation in the form of a shift of the δ13C of methane toward higher values and the occurrence of autogenic carbonate material, including ikaite, enriched in the light
isotope. Ikaite (δ13C from −25 to −60‰) was found and examined in several profiles. The redox conditions in the sediments varied from normal in
the southern part of the sea to highly oxidized along the Novaya Zemlya Trough. Vertical sections through the sediments of
the latter exemplify the complete suppression of the biochemical activity of microorganisms. Our data provide insight into
the biogeochemistry of the Kara Sea and make it possible to specify the background values needed for ecological control during
the future exploration operations and extraction of hydrocarbons in the Kara Sea.
Original Russian Text ? E.M. Galimov, L.A. Kodina, O.V. Stepanets, G.S. Korobeinik, 2006, published in Geokhimiya, 2006, No.
11, pp. 1139–1191. 相似文献
8.
Steven W. Leavitt 《Environmental Geology》1982,4(1):15-21
Continuing interest in the effects of carbon dioxide on climate has been promoted by the exponentially increasing anthropogenic
production of CO2. Volcanoes are also a major source of carbon dioxide, but their average input to the atmosphere is generally considered minor
relative to anthropogenic input. This study examines eruption chronologies to determine a new estimate of the volcanic CO2 input and to test if temporal fluctuations may be resolved. Employing representative average values of 2.7 g cm−3 as density of erupted material, 0.2 wt percent CO2 in the original melt, 60 percent degassing during eruption, and an average volume of 0.1 km3 for each of the eruptions in the recently published eruption chronology of Hirschboeck (1980), a volcanic input of about
1.5 · 1011 moles CO2 yr−1 was determined for the period 1800–1969. The period 1800–1899 had a somewhat lower input than 1900–1969, which could well
be related more to completeness of observational data than to a real increase in volcanic CO2. This input is well below man's current CO2 production of 4–5 · 1014 moles CO2 yr−1.
The average values above together with specific volumetric estimates were employed to calculate CO2 input from individual historic eruptions, massive flood basalts, and ash-flow eruptions. Total CO2 release from the largest of flood basalt and ash-flow sequences was 1015-1016 moles of CO2. The impact of these sources on global atmospheric CO2 and climate, however, will be limited by the duration and spacing of the major individual eruptive periods in the sequences. 相似文献
9.
CO<Subscript>2</Subscript> absorption by alkaline soils and its implication to the global carbon cycle 总被引:2,自引:0,他引:2
Motivated by the rapid increase in atmospheric CO2 due to human activities since the Industrial Revolution, and the climate changes it produced, the world’s concerned scientific
community has made a huge effort to investigate the global carbon cycle. However, the results reveal that the global CO2 budget cannot be balanced, unless a “missing sink” is invoked. Although numerous studies claimed to find the “missing sink”,
none of those claims has been widely accepted. This current study showed that alkaline soil on land are absorbing CO2 at a rate of 0.3–3.0 μmol m−2 s−1 with an inorganic, non-biological process. The intensity of this CO2 absorption is determined by the salinity, alkalinity, temperature and water content of the saline/alkaline soils, which are
widely distributed on land. Further studies revealed that high salinity or alkalinity positively affected the CO2 absorbing intensity, while high temperature and water content had a negative effect on the CO2 absorbing intensity of these soils. This inorganic, non-biological process of CO2 absorption by alkaline soils might have significant implications to the global carbon budget accounting. 相似文献
10.
Hydrogeochemical and Stable Isotope Characteristics of the River Idrijca (Slovenia), the Boundary Watershed Between the Adriatic and Black Seas 总被引:1,自引:0,他引:1
The hydrogeochemical and isotope characteristics of the River Idrijca, Slovenia, where the world’s second largest mercury
(Hg) mine is located, were investigated. The River Idrijca, a typical steep mountain river, has an HCO3
−–Ca2+–Mg2+ chemical composition. Its Ca2+/Mg2+ molar ratio indicates that dolomite weathering prevails in the watershed. The River Idrijca and its tributaries are oversaturated
with respect to calcite and dolomite. The pCO2 pressure is up to 13 times over atmospheric pressure and represents a source of CO2 to the atmosphere. δ18O values in river water indicate primary control from precipitation and enrichment of the heavy oxygen isotope of infiltrating
water recharging the River Idrijca from its slopes. The δ13CDIC values range from −10.8 to −6.6‰ and are controlled by biogeochemical processes in terrestrial environments and in the stream:
(1) exchange with atmospheric CO2, (2) degradation of organic matter, (3) dissolution of carbonates, and (4) tributaries. The contributions of these inputs
were calculated according to steady state equations and are estimated to be—11%:19%:30%:61% in the autumn and 0%:26%:39%:35%
in the spring sampling seasons. 相似文献
11.
Derrick Y. F. Lai 《Environmental Geology》2009,58(6):1197-1206
Peatlands are a large potential source of methane (CH4) to the atmosphere. In order to investigate the effects of climate change on CH4 emission from northern ombrotrophic peatlands, a simulation model coupling water table dynamics with methane emission was
developed for the Mer Bleue Bog in Ontario, Canada. The model was validated against reported values of CH4 flux from field measurements and the model outputs exhibited high sensitivity to acrotelm thickness, leaf area index, transmissivity
and slope of water table. With a 2–4°C temperature rise over the 4-year simulation period, the rate of CH4 release dropped significantly to under 0.1 mg m−2 day−1. On the other hand, mean CH4 emission increased by >26-fold when the increase in precipitation was >15%. When looking at the combined effects, the highest
CH4 release (13.3 mg m−2 day−1) was attained under the scenario of 2°C temperature rise and 25% precipitation increase. Results obtained in this study highlight
the importance of avoiding more extreme climate change, which would otherwise lead to enhanced methane release from peatlands
and further atmospheric warming through positive feedback. 相似文献
12.
Zongqiang Chang Qi Feng Jianhua Si Yonghong Su Haiyang Xi Jianlin Li 《Environmental Geology》2009,58(3):483-490
Field experiments on the CO2 flux of alpine meadow soil in the Qilian Mountain were conducted along the elevation gradient during the growing season of
2004 and 2005. The soil CO2 flux was measured using the Li-6400-09 soil respiration chamber attached to the Li-6400 portable photosynthesis system. The
effects of water and heat and roots on the soil CO2 flux were statistically analyzed. The results show that soil CO2 flux along the elevation gradient gradually decreases. The soil CO2 flux was low at night, with lowest value occurring between 0200 and 0600 hours, started to rise rapidly during 0700–0830
hours, and then descend during 1600–1830 hours. The peak CO2 efflux appears during 1100–1600 hours. The diurnal average of soil CO2 efflux was between 0.56 ± 0.32 and 2.53 ± 0.76 μmol m−2 s−1. Seasonally, soil CO2 fluxes are relatively high in summer and autumn and low in spring and winter. The soil CO2 efflux, from the highest to the lowest in the ranking order, occurred in July and August (4.736 μmol m−2 s−1), June and September, and May and October, respectively. The soil CO2 efflux during the growing season is positively correlated with soil temperature, root biomass and soil water content. 相似文献
13.
S CHAKRABORTY B N JANA S K BHATTACHARYA I ROBERTSON 《Journal of Earth System Science》2011,120(4):703-711
Stable carbon isotope analysis of fossil leaves from the Bhuj Formation, western India was carried out to infer the prevailing
environmental conditions. Compression fossil leaves such as Pachypteris indica, Otozamite kachchhensis, Brachyphyllum royii and Dictyozamites sp. were recovered from three sedimentary successions of the Bhuj Formation, Early Cretaceous in age. A chronology was established
based on faunal assemblage and palyno-stratigraphy and further constrained by carbon isotope stratigraphy. The three sampling
sites were the Karawadi river bank near Dharesi; the Chawad river bank near Mathal; and the Pur river section near Trambau
village in Gujarat. The Dharesi sample was also analyzed to investigate intra-leaf δ
13C variability. The mean δ
13C of the leaf was − 24.6 ± 0.4‰ which implied negligible systematic change along the leaf axis. The Mathal sample was fragmented
in nature and showed considerable variation in carbon isotopic composition. The Trambau sample considered to be the oldest,
dating to the middle of Aptian (ca. 116 Ma), shows the most depleted value in δ
13C among all of them. The overall δ
13C trend ranging from mid Aptian (ca. 116 Ma) to early Albian (ca. 110 Ma) shows a progressive increase in δ
13C from −26.8 to −20.5‰. Based on these measurements the carbon isotopic composition of atmospheric carbon dioxide of the Aptian–Albian
period is estimated to be between −7.4 and −1.7‰. The ratio of the partial pressure of carbon dioxide in leaf to that of the
ambient atmosphere calculated based on a model is estimated to be similar to that of the modern plants. This indicates that
the Early-Cretaceous plants adapted to the prevailing high carbon dioxide regime by increasing their photosynthetic uptake. 相似文献
14.
Xi Bin Ji Wen Zhi Zhao Er Si Kang Zhi Hui Zhang Bo Wen Jin 《Environmental Earth Sciences》2011,64(3):619-629
Fluxes of carbon dioxide, water vapor, and heat were measured above crop canopy using the eddy covariance method during the
2008 maize growing season, over an agricultural field within an oasis located in the middle reaches of Heihe River basin,
northwest China. The values for friction velocity, the Monin–Obukhov stability parameter, and energy balance closure indicated
that the eddy covariance system at this study site provided reliable flux estimates. Results from measurements showed that
the mean sensible heat flux was 70 W m−2 with a maximum value of 164 W m−2 (May) and a minimum value of 45 W m−2 (July) during the maize growing season. In contrast, the mean latent heat was 278 W m−2 with a maximum value of 383 W m−2 (July) and minimum of 101 W m−2 (May). The mean downward soil heat flux was 55 W m−2 with a maximum value of 127 W m−2 (May) and minimum of 49 W m−2 (July). The magnitude of mean daytime net CO2 uptake was −11.50 μmol m−2 s−1 with a maximum value of −28.32 μmol m−2 s−1 (18 and 19 July) and a minimum values of −0.32 μmol m−2 s−1 (18 and 19 May). Correlation was observed between daytime half-hourly carbon dioxide flux and canopy conductance. In addition,
the relationship between carbon dioxide flux and photosynthetically active radiation for selected days during different stages
of maize growing season indicated the carbon dioxide flux uptake by the canopy was controlled by actual photosynthetic activity
related to the variation of green leaf area index for the different growing stages. 相似文献
15.
Geochemical detection of carbon dioxide in dilute aquifers 总被引:1,自引:0,他引:1
Background
Carbon storage in deep saline reservoirs has the potential to lower the amount of CO2 emitted to the atmosphere and to mitigate global warming. Leakage back to the atmosphere through abandoned wells and along faults would reduce the efficiency of carbon storage, possibly leading to health and ecological hazards at the ground surface, and possibly impacting water quality of near-surface dilute aquifers. We use static equilibrium and reactive transport simulations to test the hypothesis that perturbations in water chemistry associated with a CO2 gas leak into dilute groundwater are important measures for the potential release of CO2 to the atmosphere. Simulation parameters are constrained by groundwater chemistry, flow, and lithology from the High Plains aquifer. The High Plains aquifer is used to represent a typical sedimentary aquifer overlying a deep CO2 storage reservoir. Specifically, we address the relationships between CO2 flux, groundwater flow, detection time and distance. The CO2 flux ranges from 103 to 2 × 106 t/yr (0.63 to 1250 t/m2/yr) to assess chemical perturbations resulting from relatively small leaks that may compromise long-term storage, water quality, and surface ecology, and larger leaks characteristic of short-term well failure. 相似文献16.
Contribution of a sewage sludge application to the short-term carbon sequestration across a wide range of agricultural soils 总被引:1,自引:0,他引:1
José Martín Soriano-Disla J. Navarro-Pedreño I. Gómez 《Environmental Earth Sciences》2010,61(8):1613-1619
The atmospheric levels of carbon dioxide (CO2) and other greenhouse gases (GHGs) have increased dramatically since the industrial revolution. The atmospheric enrichment
with CO2 and other GHGs has resulted in multiple negative consequences: such as the increase in the average temperature and the rise
of the sea level. Hence, there is a growing interest in developing feasible methods to reduce the atmospheric levels of these
gases. One of these strategies is to enhance C sequestration through the increase of soil organic carbon (SOC) pool by the
amendment of agricultural soils with sewage sludge. However, there is considerable uncertainty about the effects (positive
or negative) of sewage sludge applications on the SOC pool. Thus, a simple approach developed under laboratory conditions
is presented to discern the effect of a single sewage sludge application of 50 t ha−1 on the short-term SOC pool in 60 contrasting agricultural soils. The role of soil factors in the C sequestration of the recently
added carbon was also studied. The application of sewage sludge supposed a mean increase of 1.7 ± 1.6 g SOC kg−1, with peak increases of up to 3.8 g SOC kg−1 and decreases of up to 4.6 g SOC kg−1. The initial SOC contents conditioned the C sequestration after sewage sludge application, and no other soil property was
related. 相似文献
17.
Hydrogeochemical processes in the groundwater environment of Heihe River Basin,northwest China 总被引:5,自引:0,他引:5
Zhu Gaofeng Su Yonghong Huang Chunlin Feng Qi Liu Zhiguang 《Environmental Earth Sciences》2010,60(1):139-153
The Heihe River Basin is a typical arid inland river basin for examining stress on groundwater resources in northwest China.
The basin is composed of large volumes of unconsolidated Quaternary sediments of widely differing grain size, and during the
past half century, rapid socio-economic development has created an increased demand for groundwater resources. Understanding
the hydrogeochemical processes of groundwater and water quality is important for sustainable development and effective management
of groundwater resources in the Heihe River basin. To this end, a total of 30 representative groundwater samples were collected
from different wells to monitor the water chemistry of various ions and its quality for irrigation. Chemical analysis shows
that water presents a large spatial variability of chemical facies (SO4
2−–HCO3−, SO4
2−–Cl−, and Cl−–SO4
2−) as groundwater flow from recharge area to discharge area. The ionic ratio indicates positive correlation between the flowing
pairs of parameters: Cl− and Na+(r = 0.95), SO4
2− and Na+ (r = 0.84), HCO3
− and Mg2+(r = 0.86), and SO4
2− and Ca2+ (r = 0.91). Dissolution of minerals, such as halite, gypsum, dolomite, silicate, and Mirabilite (Na2SO4·10H2O) in the sediments results in the Cl−, SO4
2−, HCO3
−, Na+, Ca2+ and Mg2+ content in the groundwater. Other reactions, such as evaporation, ion exchange, and deposition also influence the water composition.
The suitability of the groundwater for irrigation was assessed based on the US Salinity Laboratory salinity classification
and the Wilcox diagram. The results show that most of the groundwater samples are suitable for irrigation uses barring a few
locations in the dessert region in the northern sub-basin. 相似文献
18.
Sigurdur Jakobsson 《Contributions to Mineralogy and Petrology》1997,127(1-2):129-135
The concentrations of water and carbon dissolved in an icelandite glass quenched from 1400 °C and 10 kbar were measured using
Fourier transform infra-red spectroscopy and elemental analyses of carbon and hydrogen. Only carbon dioxide and water were
observed in the fluid phase as analysed after quenching with a qudrupole mass analyser. The mole fraction of carbon dioxide
in the fluid phase ranged from 0.36 to 0.95. Carbon is dissolved as carbonate except at the highest CO2 fluid fugacity, where a small amount of molecular CO2 is observed. Dissolved carbon in the glasses, calculated as CO2, remained constant at approximately 1 wt %, in spite of the different CO2 fluid fugacities. Water was dissolved as molecular water and as hydroxyl groups, the hydroxyl concentration in the quenched
glasses remaining almost constant over the whole interval, whereas the molecular water dissolves in accordance with Henry's
law. Molecular water peaks at 5200␣cm−1 and 1630 cm−1, the hydroxyl peak at 4500␣cm−1, and the carbonate peaks at 1400 cm−1–1550 cm−1 have been calibrated using elemental analyses of C and H in the quenched glasses. As molecular water decreases in the melt
the higher wavenumber carbonate peak is observed to move towards the molecular water peak at 1630 cm−1 causing a split of the carbonate peaks, ranging from 45 cm−1 to 100 cm−1.
Received: 15 November 1995 / Accepted: 21 September 1996 相似文献
19.
Chemical and Strontium Isotopic Compositions of the Hanjiang Basin Rivers in China: Anthropogenic Impacts and Chemical Weathering 总被引:1,自引:0,他引:1
The Hanjiang River, the largest tributaries of the Changjiang (Yangtze) River, is the water source area of the Middle Route
of China’s South-to-North Water Transfer Project. The chemical and strontium isotopic compositions of the river waters are
determined with the main purpose of understanding the contribution of chemical weathering processes and anthropogenic inputs
on river solutes, as well as the associated CO2 consumption in the carbonate-dominated basin. The major ion compositions of the Hanjiang River waters are characterized by
the dominance of Ca2+ and HCO3
−, followed by Mg2+ and SO4
2−. The increase in TDS and major anions (Cl−, NO3
−, and SO4
2−) concentrations from upstream to downstream is ascribed to both extensive influences from agriculture and domestic activities
over the Hanjiang basin. The chemical and Sr isotopic analyses indicate that three major weathering sources (dolomite, limestone,
and silicates) contribute to the total dissolved loads. The contributions of the different end-members to the dissolved load
are calculated with the mass balance approach. The calculated results show that the dissolved load is dominated by carbonates
weathering, the contribution of which accounts for about 79.4% for the Hanjiang River. The silicate weathering and anthropogenic
contributions are approximately 12.3 and 6.87%, respectively. The total TDS fluxes from chemical weathering calculated for
the water source area (the upper Hanjiang basin) and the whole Hanjiang basin are approximately 3.8 × 106 and 6.1 × 106 ton/year, respectively. The total chemical weathering (carbonate and silicate) rate for the Hanjiang basin is approximately
38.5 ton/km2/year or 18.6 mm/k year, which is higher than global mean values. The fluxes of CO2 consumption by carbonate and silicate weathering are estimated to be 56.4 × 109 and 12.9 × 109 mol/year, respectively. 相似文献
20.
Streams and rivers are major exporters of C and other dissolved materials from watersheds to coastal waters. In streams and rivers, substantial amounts of terrigenous organic C is metabolized and degassed as CO2 to the atmosphere. A long-term evaluation of CO2 dynamics in streams is essential for understanding factors controlling CO2 dynamics in streams in response to changes in climate and land-use. Long-term changes in the partial pressure of CO2 (pCO2) were computed in the Anacostia River and the lower Potomac River in the Chesapeake Bay watershed. Long-term estimates were made using routine monitoring data of pH, total alkalinity, and dissolved nutrients from 1985 to 2006 at 14 stations. Longitudinal variability in pCO2 dynamics was also investigated along these rivers downstream of the urban Washington D.C. metropolitan area. Both rivers were supersaturated with CO2 with respect to atmospheric CO2 levels (392 μatm) and the highly urbanized Anacostia waters (202–9694 μatm) were more supersaturated than the Potomac waters (557–3800 μatm). Long-term variability in pCO2 values may be due to changes in river metabolism and organic matter and nutrient loadings. Both rivers exchange significant amounts of CO2 with the atmosphere (i.e., Anacostia at 0.2–72 mmol m−2 d−1 and Potomac at 0.12–24 mmol m−2 d−1), implying that waterways receiving organic matter and nutrient subsidies from urbanized landscapes have the potential to increase river metabolism and atmospheric CO2 fluxes along the freshwater–estuarine continuum. 相似文献