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1.
《Comptes Rendus Geoscience》2015,347(2):77-83
Bacterial activity in the near-field environment of radioactive waste disposal facilities in deep argillaceous rocks is currently under investigation. Bacterial development could be enhanced by the availability of low-molecular-weight organic acids (LMWOA) dissolved in the pore water of clayey rocks. This study firstly aimed at isolating and characterizing the LMWOA of the Toarcian argillite from the Tournemire Underground Research Laboratory (France, Aveyron). It also aimed at assessing the disturbing effects that could be induced by a disposal facility on the type and release of LMWOA (exposure to oxygen, alkaline pH, temperature increase). Under the experimental conditions investigated at 60 °C, the mean dissolved organic carbon (DOC) is about 15 mg L−1 with a LMWOA proportion of 35 %. The main LMWOA are composed of formate, fumarate, propionate, acetate, and lactate. DOC is mainly influenced by both temperature and pH increases, whereas the LMWOA type nature and release are more specifically affected by the exposure to oxygen. 相似文献
2.
Samples from two argillaceous formations (Opalinus Clay and Posidonia Shale) of near-identical maturity from northern Switzerland were subjected to a geochemical characterisation of organic matter and to confined-system pyrolysis experiments. Throughout the study area, the characteristics of organic matter are similar, indicating a spatially homogeneous sedimentary facies. Posidonia Shale contains marine organic matter deposited in a reducing environment, while a predominantly terrigenous source and a more oxidising environment of deposition was identified for Opalinus Clay. In the western and central parts of the study area, organic maturity is close to the onset of oil generation. In the easternmost part, a higher maturity has been reached due to a deeper burial below thick Tertiary Molasse deposits.Isothermal pyrolysis experiments were conducted at temperatures between 250 and 390 °C over 24 h. Bitumen yields increase along similar pathways for both Opalinus Clay and Posidonia Shale, but the maximum values are displaced by 10–20 °C. Data pertaining to maturity were determined from GC–MS analyses of saturated hydrocarbons, and specific attention was given to C29-sterane and C32-hopane isomerisation ratios. The evolution of these parameters with rising temperature is slightly different in the two formations, which is attributed to the contrasting organic facies. The pyrolysis data, together with literature data from natural basins, were used to calculate kinetic parameters for C29-sterane and C32-hopane, assuming a single-step isomerisation scheme according to the Arrhenius law. The resulting values based on pyrolysis data alone are very similar to those based on the combination of pyrolysis and natural data. Activation energies are similar in both formations, while the frequency factors are up to one order of magnitude higher for Posidonia Shale when compared to Opalinus Clay. For the Benken site, maximum temperature during Cretaceous burial was calculated on the basis of the kinetic data, using the TTI approach. The resulting temperatures of 75–80 °C are 5–10 °C below those derived in the literature from apatite fission-track analysis, vitrinite reflectance and basin modelling. 相似文献
3.
Natural tracers (Cl? and stable water isotopes) in pore water of the Opalinus Clay and adjacent formations were studied in the motorway tunnel at Mont Russelin, Switzerland. The Opalinus Clay occurs in the core of an anticline which is cut by a complex system of thrust faults. Concentration profiles of natural tracers were taken from 17 boreholes along a 363 m long section. Pore waters of drillcore samples were analysed with indirect and direct methods. The Cl? and stable water isotope distribution in the pore water shows a regular and well defined profile, with a conspicuous decrease towards the overlying Dogger limestone aquifer. The highest Cl? values (approximately 23,000 mg/L) are found in the core of the anticline in Liassic claystones underlying the Opalinus Clay. To quantify the large-scale transport properties of the Opalinus Clay formation, a 2D transport model was constructed and used to reproduce the observed concentration profiles. The calculations indicate that the observed tracer distributions are consistent with diffusion as the dominant transport process. Groundwater flow in the overlying Dogger aquifer was initiated about 2–4 Ma ago, which is long after the folding of the Jura Mountains and probably coincides with the exposure of the aquifer to freshwater recharge following continued erosion of the anticline. The calculations suggest that tracer distributions are controlled by 1) the timing of freshwater recharge in the overlying limestone aquifer, 2) the shape of the anticline and 3) the magnitude and the anisotropy ratio of diffusion coefficients. 相似文献
4.
In Belgium, compatibility studies are performed in view of the final disposal of nitrate-containing bituminised intermediate-level radioactive waste in Boom Clay, which is considered as a potential host formation. Due to the presence of large amounts of nitrate in the waste, a slow release of nitrate (and to a smaller extent also nitrite) into the Boom Clay is expected. Nitrate and/or nitrite reduction by redox-active components of the host rock may cause a geochemical perturbation of the clay and subsequently might affect its barrier function against the migration of radionuclides. This paper therefore addresses the possible oxidation of one of the main redox-active components of the Boom Clay, i.e. dissolved organic matter, by nitrate and nitrite. For this, abiotic and microbially mediated nitrate and nitrite reduction was studied during long-term batch tests (2–2.5 years) in Boom Clay pore water, containing 155 ± 15 mg C/l present as humic and fulvic acids. Changes in the reducing capacity of the DOM due to oxidation were assessed successfully using two oxidants, namely ferricyanide and ferric citrate. The results of these experiments indicate that an abiotic reaction between DOM and nitrate does not occur or is characterised by very slow kinetics. On the other hand, a slow microbial nitrate reduction to nitrite was observed and the associated oxidation of DOM was confirmed by a decrease in the (partial) reducing capacity of DOM for ferric citrate. In contrast to nitrate, nitrite was shown to oxidise DOM both abiotically and mediated by microbes through (chemo)denitrification, although these reactions also seem to occur only at a rather slow rate. No significant change in the maximally obtainable reducing capacity of DOM (using ferricyanide) was detected during any of the observed reactions, suggesting that the impact of such a slow heterotrophic nitrate reduction is very limited. 相似文献
5.
Marek Pękala Jan Dirk Kramers Hans Niklaus Waber Thomas Gimmi Peter Alt-Epping 《Applied Geochemistry》2009
The Opalinus Clay formation in North Switzerland is a potential host rock for a deep underground radioactive waste repository. The distribution of 238U, 234U and 230Th was studied in rock samples of the Opalinus Clay from an exploratory borehole at Benken (Canton of Zurich) using MC-ICP-MS. The aim was to assess the in situ, long-term migration behaviour of 234U in this rock. Very low hydraulic conductivities of the Opalinus Clay, reducing potential of the pore water and its chemical equilibrium with the host rock are expected to render both 238U and 230Th immobile. If U is heterogeneously distributed in the Opalinus Clay, gradients in the supply of 234U from the rock matrix to the pore water by the decay of 238U will be established. Diffusive redistribution separates 234U from its immobile parent 238U resulting in bulk rock 234U/238U activity disequilibria. These may provide a means of estimating the mobility of 234U in the rock if the diffusion rate of 234U is significant compared to its decay rate. Sampling was carried out on two scales. Drilling of cm-spaced samples from the drill-core was done to study mobility over short distances and elucidate possible small-scale lithological control. Homogenized 25-cm-long portions of a 2-m-long drill-core section were prepared to provide information on transport over a longer distance. Variations in U and/or Th content on the cm-scale between clays and carbonate-sandy layers are revealed by β-scanning, which shows that the (dominant) clay is richer in both elements. 相似文献
6.
The full-scale mine-by (MB) test conducted in 2008 in the Mont Terri underground rock laboratory (Switzerland) investigated the deformation and the coupled hydro-mechanical behavior of the Opalinus Clay in response to tunnel excavations. The Opalinus Clay is currently under investigation in Switzerland as a potential host rock for geologic disposal of high-level radioactive waste. To further improve the understanding and modeling of the coupled processes and their impact on the performance of a geologic repository in Opalinus Clay, a newly developed two-part Hooke’s model (TPHM) was implemented into a geomechanical simulator. A three-dimensional simulation model based on the TPHM was then developed to predict the deformation and pore pressure responses in the near field of the MB Niche 2 test at the Mont Terri Site. The usefulness and validity of the TPHM are demonstrated by the consistency between simulation results and field observations. Simulation results show that the pore pressure disturbance becomes visible at about 11 m ahead of the mine-by excavation advancing face (along the longitudinal direction of the MB Niche). The results also demonstrate that there exists a good correlation between the excavation damage zone (EDZ) and the pore-pressure evolution, which may have important practical implications for monitoring EDZ evolution with pore-pressure sensors. The simulation results, which are sensitive to the constitutive relationships used in the model, capture both the observed displacements and the size of the damage zone, whereas the approach based on the conventional Hooke’s law underestimates both. The comparison between simulated and observed results also indicates that laboratory-measured mechanical properties can be used to accurately predict field-scale mechanical deformations, as long as valid constitutive relationships are employed. 相似文献
7.
The chemistry of pore water (particularly pH and ionic strength) is an important property of clay rocks being considered as host rocks for long-term storage of radioactive waste. Pore waters in clay-rich rocks generally cannot be sampled directly. Instead, their chemistry must be found using laboratory-measured properties of core samples and geochemical modelling. Many such measurements have been made on samples from the Opalinus Clay from the Mont Terri Underground Research Laboratory (URL). Several boreholes in that URL yielded water samples against which pore water models have been calibrated. Following a first synthesis report published in 2003, this paper presents the evolution of the modelling approaches developed within Mont Terri URL scientific programs through the last decade (1997-2009). Models are compared to the composition of waters sampled during dedicated borehole experiments. Reanalysis of the models, parameters and database enabled the principal shortcomings of the previous modelling efforts to be overcome. The inability to model the K concentrations correctly with the measured cation exchange properties was found to be due to the use of an inappropriate selectivity coefficient for Na-K exchange; the inability to reproduce the measured carbonate chemistry and pH of the pore waters using mineral-water reactions alone was corrected by considering clay mineral equilibria. Re-examination of the measured Ca/Mg activity ratios and consideration of the mineralogical composition of the Opalinus Clay suggested that Ca/Mg cation exchange rather than dolomite saturation may control the ratio of these ions in solution. This re-examination also suggests that the Ca/Mg ratio decreases with increasing pore-water salinity. Several possible reasons for this are proposed. Moreover, it is demonstrated that feldspar equilibria must not be included in Opalinus Clay modelling because feldspars are present only in very small quantities in the formation and because Na/K ratios measured in pore water samples are inconsistent with feldspar saturation. The principal need to improve future modelling is additional or better data on rock properties, in particular: (i) a more detailed identification of phases in the Opalinus Clay that include redox-sensitive elements together with evaluation of their thermodynamic properties; (ii) an improved understanding of the distribution of celestite throughout the Opalinus Clay for Sr/SO4 concentrations control; (iii) improvements in analytic and thermodynamic data for Ca-Mg rock cation exchange and mineral chemical properties and (iv) the measurement of composition and stability constants of clay minerals actually present in the formation. 相似文献
8.
Andreas Gautschi 《Hydrogeology Journal》2001,9(1):97-107
As part of the Swiss programme for high-level radioactive-waste disposal, a Jurassic shale (Opalinus Clay) is being investigated
as a potential host rock. Observations in clay pits and the results of a German research programme focusing on hazardous waste
disposal have demonstrated that, at depths of 10–30 m, the permeability of the Opalinus Clay decreases by several orders of
magnitude. Hydraulic tests in deeper boreholes (test intervals below 300 m) yielded hydraulic conductivities <10–12 m/s, even though joints and faults were included in some of the test intervals. These measurements are consistent with hydrogeological
data from Opalinus Clay sections in ten tunnels in the Folded Jura of northern Switzerland. Despite extensive faulting, only
a few indications of minor water inflow were encountered in more than 6,600 m of tunnel. All inflows were in tunnel sections
where the overburden is less than 200 m. The hydraulic data are consistent with clay pore-water hydrochemical and isotopic
data. The extensive hydrogeological data base – part of which derives from particularly unfavourable geological environments
– provides arguments that advective transport through faults and joints is not a critical issue for the suitability of Opalinus
Clay as a host rock for deep geological waste disposal.
Electronic Publication 相似文献
9.
对洱海沉积物间隙水中溶解有机质(DOM)含量、紫外可见吸收、荧光以及分子量等的垂直分布特征进行了研究。结果表明,DOC含量在沉积物水界面明显富集,随后急剧下降,6cm处达到最小值,随后呈上升趋势。DOC与吸光度值、荧光发射光谱强度之间具有一定的线性相关关系。DOM的E3/E4值范围在1～6之间,绝大多数在1～35之间。表征DOM中腐殖质来源的指标荧光指数值处于148～159之间,说明DOM以陆源输入为主。此外,洱海沉积物间隙水DOM分子量分布呈多峰分布模式,重均分子量(Mw)值在1462～1953Da之间,数均分子量(Mn)值在547～900Da之间,多分散性系数ρ值在202～305之间。随着沉积深度增大,Mw和Mn有略微的增大趋势,但变化不大。沉积物的氧化还原条件、微生物活动以及铁、锰氧化物等在沉积剖面的差异是控制间隙水中DOM各种地球化学特性的主要因素。 相似文献
10.
11.
Characterization of drying-induced deformation behaviour of Opalinus Clay and tuff in no-stress regime 总被引：1，自引：0，他引：1
Aung Ko Ko Soe Masahiko Osada Manabu Takahashi Tai Sasaki 《Environmental Geology》2009,58(6):1215-1225
The drying-induced deformation behaviour of Opalinus Clay and tuff, which are being investigated under international and local
collaborative projects for nuclear waste disposal in Switzerland and Japan, was investigated under a no-stress condition in
the laboratory to evaluate their generic susceptibility to the formation of excavation damaged zone. The cylindrical core
samples of Opalinus Clay and tuff were prepared to a one-dimensional drying condition and submitted to an uncontrolled laboratory
environment. The strain evolution, evaporative water loss and environmental entities, such as temperature and relative humidity,
were recorded simultaneously and quasi-continuously. It was observed that the drying phase induced significant strain magnitude
and damage in Opalinus Clay samples, which was evidenced by the formation of hairy cracks on the surface parallel to the bedding.
On the contrary, the strain occurrences in tuff samples were relatively insignificant, and no tendency of cracking was observed.
In addition, the quasi-continuous availability of volumetric strains was further used in poroelastic relation for the estimation
of capillary suction evolution. The calculated results were validated with pore size distributions obtained from mercury intrusion
porosimetry. 相似文献
12.
B. Garitte T. S. Nguyen J. D. Barnichon B. J. Graupner C. Lee K. Maekawa C. Manepally G. Ofoegbu B. Dasgupta R. Fedors P. Z. Pan X. T. Feng J. Rutqvist F. Chen Jens Birkholzer Q. Wang O. Kolditz H. Shao 《Environmental Earth Sciences》2017,76(9):345
Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in order to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding. 相似文献
13.
A series of cores were obtained from the Great Bay Estuary, New Hampshire during 1980 and 1981 in order to investigate the effects on the dissolved organic matter of exposure of anoxic marine pore water to atmospheric oxygen during laboratory handling. Sediment sections from these cores were homogenized and split into two equal parts, one of which was handled in a glove bag under a nitrogen atmosphere, and the other exposed to atmospheric oxygen during laboratory processing. Analysis of the pore water for dissolved organic carbon (DOC) indicated two effects: (1) in the top 15 cm, DOC was lost from the pore water of the oxidized subsections, probably as a consequence of co-precipitation with iron (III) oxi-hydroxides, whereas (2) deeper in the cores, the pore water from the oxidized subsections showed a net increase in DOC, possibly due to oxidation of sedimentary organic matter. In addition, structural changes in the dissolved organic matter in anoxic pore water following oxidation was indicated by high pressure liquid chromatography and ultrafiltration analysis. 相似文献
14.
The aim of this study is to estimate the C loss from forest soils due to the production of dissolved organic C (DOC) along a north–south European transect. Dissolved organic matter (DOM) was extracted from the forest soils incubated at a controlled temperature and water content. Soils were sampled from forest plots from Sweden to Italy. The plots represent monocultures of spruce, pine and beech and three selected chronosequences of spruce and beech spanning a range of mean annual temperature from 2 to 14 °C. The DOM was characterized by its DOC/DON ratio and the C isotope composition δ13C. The DOC/DON ratio of DOM varied from 25 to 15 after 16 days of incubation and it decreased to between 16 and 10 after 126 days. At the beginning of incubation the δ13C values of DOC were 1‰ or 2‰ less negative than incubated soils. At the end of the experiment δ13C of DOC were the same as soil values. In addition to DOC production heterotrophic respiration and N mineralization were measured on the incubated soils. The DON production rates decreased from 30 to 5 μgN gC−1 d−1 after 16 days of incubation to constant values from 5 to 2 μgN gC−1 d−1 after 126 days at the end of experiment. The DIN production rates were nearly constant during the experiments with values ranging from 20 to 4 μgN gC−1 d−1. DOC production followed first-order reaction kinetics and heterotrophic respiration followed zero-order reaction kinetics. Kinetic analysis of the experimental data yielded mean annual DOC and respiration productions with respect to sites. Mean annual estimates of DOC flux varied from 3 to 29 g of C m−2 (1–19 mg C g−1 of available C), corresponding to mean DOC concentrations from 2 to 85 mg C L−1. 相似文献
15.
G. J. Chen T. Maes F. Vandervoort X. Sillen P. Van Marcke M. Honty M. Dierick P. Vanderniepen 《Rock Mechanics and Rock Engineering》2014,47(1):87-99
Within the framework of the TIMODAZ project, permeameter tests and isostatic tests were performed on Boom Clay and Opalinus Clay in order to assess the impact of temperature, pore water composition, and confining stress on the sealing of damaged samples of Boom Clay and Opalinus Clay. A microfocus X-ray computed tomography technique was used to visualize the evolution of the sealing process. Compared to the fast sealing of Boom Clay, the sealing of Opalinus Clay was much slower. The heating showed a significant, favorable impact on the sealing behavior of Opalinus Clay under permeameter test conditions, while the sealing behavior of Boom Clay appeared to be unaffected. Tests performed under isostatic conditions did not reveal a significant influence of a heating–cooling cycle on the sealing behavior of these clays. The reappearance of the fractures or holes in the samples after dismantling confirms earlier observations which showed that after sealing, the original mechanical properties are not recovered. In other words, a heating cycle does not seem to induce healing. 相似文献
16.
We present a new stable isotope mass balance method for measuring the enhanced aqueous solubility of specific organic compounds in the presence of natural dissolved organic matter (DOM). It involves interfacing a standard dissolved organic carbon (DOC) analyzer with a stable isotope ratio monitoring system, is applicable to a wide range of model organic compounds and can be tuned to provide maximum precision for a given range of compound solubility and initial natural DOC concentration. Using 13C-labeled styrene as a model compound, we applied the method to investigate the reactivity of Dismal Swamp DOM as a function of season, nominal molecular size and chemical composition as determined using Fourier Transform Infrared Spectroscopy (FTIR). The solubility enhancement of styrene ranged from 23% to 118% relative to deionized water, while DOC-normalized enhancements varied from about 0.04 to 0.35 μM styrene/μM DOC as a function of season and nominal molecular weight. Statistical analysis of FTIR spectra reveals a strong positive correlation between the styrene concentration and the carboxyl content of the natural DOM. Reactivity differences between high molecular weight (HMW), low molecular weight (LMW) and total DOM samples are consistent with potential variations in their higher order structures. 相似文献
17.
18.
A. Huguet L. Vacher S. Relexans S. Saubusse J.M. Froidefond E. Parlanti 《Organic Geochemistry》2009,40(6):706-719
The isolation, characterization and study of the properties of aquatic dissolved organic matter (DOM) still represent a challenge because of the heterogeneity, complexity and low concentration of organic material in natural waters. Based on its ability to interact with contaminants and thus to modify their transport and bioavailability, DOM is of interest for environmental purposes. The objective of this work was to better characterize DOM in the Gironde Estuary (southwestern France). The estuary represents an exchange zone between the continent and the Atlantic Ocean and conditions the transfer of organic and inorganic substances from the continental to the oceanic environment. Several samples were collected along the estuary during three cruises in 2002 and 2006. They were analysed using excitation–emission matrix (EEM) spectroscopy, a sensitive technique that allows direct analysis of water samples. Fluorescent DOM and dissolved organic carbon (DOC) did not behave conservatively in this estuarine system, i.e. the organic material did not undergo simple dilution from the upstream to the downstream part of the estuary. A seasonal variability in DOC content was pointed out, whereas few seasonal variations in DOM fluorescence were observed. DOM sources and processing in the estuary were further evaluated by determining two fluorescence indices – the humification index (HIX) and the index of recent autochthonous contribution (BIX). By applying these indices, the relative degree of humification (HIX) and autotrophic productivity (BIX) could be assessed. Based on the fluorescence and DOC results, the estuary was divided into three zones depending on salinity (S) and characterized by specific DOM: (i) A turbid zone of low salinity (S < 5) and high suspended particulate matter concentration with increase in the intensities of the α′ and α fluorophores, characteristic of humic-like compounds. (ii) A mid-estuarine zone (5 < S < 25) characterized by low autotrophic productivity and containing strongly degraded organic material, as shown by the low values of BIX and high values of HIX. (iii) A higher salinity area (S > 25) characterized by increased autotrophic productivity and a marked marine influence, and associated with high and low values of BIX and HIX, respectively. The HIX and BIX indices were shown as useful tools for readily defining and classifying DOM characteristics in estuarine waters. 相似文献
19.
In the present study, we explored the use of various optical parameters to detect differences in the composition of the dissolved
organic matter (DOM) in a set of lakes that are all located on the Canadian Precambrian Shield, but within which Cu and Ni
speciation predictions were previously shown to diverge from measured values in some lakes but not in others. Water samples
were collected with in situ diffusion samplers in 2007 (N = 18 lakes) and 2008 (N = 8 lakes). Significant differences in DOM quality were identified between the sampling regions (Rouyn-Noranda, Québec and
Sudbury, Ontario) and among lakes, based on dissolved organic carbon concentrations ([DOC]), specific UV absorbance (SUVA254), fluorescence indices (FI), and excitation–emission matrix (EEM) fluorescence measurements. Parallel factor analysis (PARAFAC)
of the EEM spectra revealed four components, two of which (C3, oxidized quinone fluorophore of allochthonous origin, and C4,
tryptophan-like protein fluorescence of autochthonous origin) showed the greatest inter-regional variation. The inter-lake
differences in DOM quality were consistent with the regional watershed characteristics as determined from satellite imagery
(e.g., watershed-to-lake surface area ratios and relative percentages of surface water, rock outcrops vegetative cover and
urban development). Source apportionment plots, built upon PARAFAC components ratios calculated for our lakes, were used to
discriminate among DOM sources and to compare them to sources identified in the literature. These results have implications
for other areas of research, such as quantifying lake-to-lake variations in the influence of organic matter on the speciation
of trace elements in natural aquatic environments. 相似文献
20.
Electron accepting capacity of dissolved organic matter as determined by reaction with metallic zinc 总被引：2，自引：0，他引：2
Christian Blodau Markus Bauer Simona Regenspurg Donald Macalady 《Chemical Geology》2009,260(3-4):186-195
Information about the chemical electron accepting capacity (EAC) of dissolved organic matter (DOM) is scarce owing to a lack of applicable methods. We quantified the electron transfer from metallic Zn to natural DOM in batch experiments at DOC concentrations of 10–100 mg-C L− 1 and related it to spectroscopic information obtained from UV-, synchronous fluorescence, and FTIR- spectroscopy. The electron donating capacity of DOM and pre-reduced DOM was investigated using Fe(CN)63− as electron acceptor. Presence of DOM resulted in release of dissolved Zn, consumption of protons, and slower release of hydrogen compared to reaction of metallic Zn with water at pH 6.5. Comparison with reaction stoichiometry confirmed that DOM accepted electrons from metallic Zn. The release of dissolved Zn was dependent on pH, DOC concentration, ionic strength, and organic matter properties. The reaction appeared to be completed within about 24 h and was characterized by pseudo first order kinetics with rate constants of 0.5 to 0.8 h− 1. EAC per mass unit of carbon ranged from 0.22 mmol g− 1 C to 12.6 mmol g− 1 C. Depending on the DOM, a calculated 28–127% of the electrons transferred from metallic Zn to DOM could be subsequently donated to Fe(CN)63−. EAC decreased with DOC concentration, and increased with aromaticity, carboxyl, and phenolic content of the DOM. The results indicate that an operationally defined EAC of natural DOM can be quantified by reaction with metallic Zn and that DOM properties control the electron transfer. Shortcomings of the method are the coagulation and precipitation of DOM during the experiment and the production of hydrogen and dissolved Zn by reaction of metallic Zn with water, which may influence the determined EAC. 相似文献