Sulfide-driven arsenic mobilization from arsenopyrite and black shale pyrite   总被引：1，自引：0，他引：1  

Wenyi Zhu  Nathan Yee  E. Danielle Rhine  John R. Reinfelder 《Geochimica et cosmochimica acta》2008,72(21):5243-5250

We examined the hypothesis that sulfide drives arsenic mobilization from pyritic black shale by a sulfide-arsenide exchange and oxidation reaction in which sulfide replaces arsenic in arsenopyrite forming pyrite, and arsenide (As−1) is concurrently oxidized to soluble arsenite (As+3). This hypothesis was tested in a series of sulfide-arsenide exchange experiments with arsenopyrite (FeAsS), homogenized black shale from the Newark Basin (Lockatong formation), and pyrite isolated from Newark Basin black shale incubated under oxic (21% O₂), hypoxic (2% O₂, 98% N₂), and anoxic (5% H₂, 95% N₂) conditions. The oxidation state of arsenic in Newark Basin black shale pyrite was determined using X-ray absorption-near edge structure spectroscopy (XANES). Incubation results show that sulfide (1 mM initial concentration) increases arsenic mobilization to the dissolved phase from all three solids under oxic and hypoxic, but not anoxic conditions. Indeed under oxic and hypoxic conditions, the presence of sulfide resulted in the mobilization in 48 h of 13-16 times more arsenic from arsenopyrite and 6-11 times more arsenic from isolated black shale pyrite than in sulfide-free controls. XANES results show that arsenic in Newark Basin black shale pyrite has the same oxidation state as that in FeAsS (−1) and thus extend the sulfide-arsenide exchange mechanism of arsenic mobilization to sedimentary rock, black shale pyrite. Biologically active incubations of whole black shale and its resident microorganisms under sulfate reducing conditions resulted in sevenfold higher mobilization of soluble arsenic than sterile controls. Taken together, our results indicate that sulfide-driven arsenic mobilization would be most important under conditions of redox disequilibrium, such as when sulfate-reducing bacteria release sulfide into oxic groundwater, and that microbial sulfide production is expected to enhance arsenic mobilization in sedimentary rock aquifers with major pyrite-bearing, black shale formations.  相似文献   

A high-resolution TEM-AEM, pH titration, and modeling study of Zn coprecipitation with ferrihydrite     

Stacin Martin  Chen Zhu  Joseph Rule  Robert Ford  Yee Soong 《Geochimica et cosmochimica acta》2005,69(6):1543-1553

Experiments of Zn²⁺ and Fe³⁺ coprecipitation as a function of pH were conducted in the laboratory at ambient temperature and pressure. X-ray diffraction patterns of the coprecipitates show two broad peaks at 0.149 and 0.258 nm, which is consistent with published patterns for pure 2-line ferrihydrite. Zn²⁺ uptake occurred at pH ≥5 while Fe³⁺ precipitation occurred between pH 3 and 4, although both Zn²⁺ and Fe³⁺ were present in the same solution during the entire range of pH titration. High-resolution transmission electron microscopy shows that the coprecipitates are 2 to 6 nm sized single crystalline particles but aggregated to 50 to 400 nm sized clusters. Analytical electron microscopy indicated that the 5% atomic Zn with respect to Fe was homogeneously distributed. No segregated phases were found in the clusters or at single crystal edges, which is consistent with published extended X-ray absorption fine structure (EXAFS) results at similar Zn/(Zn + Fe) ratios. Hence, occlusion and surface precipitation may be excluded as possible coprecipitation mechanisms. The bulk solution Zn²⁺ sorption edge was fitted to both solid solution and generalized diffuse layer surface complexation models. However, a solid solution model is inconsistent with published EXAFS results that show tetrahedral polydentate Zn²⁺ complexes sharing apices with Fe³⁺octahedra.  相似文献   

Uncertainty analysis of space–time prisms based on the moment-design method     

Yee Leung  Zi Zhao  Jiang-Hong Ma 《International journal of geographical information science》2016,30(7):1336-1358

Space–time prism (STP) is an important concept for the modeling of object movements in space and time. An STP can be conceptualized as the result of the potential path of a moving object revolving around in the three-dimensional space. Though the concept has found applications in time geography, research on the analysis and propagation of uncertainty in STPs, particularly under high degree of nonlinearity, is scanty. Based on the efficiency and effectiveness of the moment-design (M-D) method, this paper proposes an approach to deal with nonlinear error propagation problems in the potential path areas (PPAs) of STPs and their intersections. Propagation of errors to the PPA and its boundary, and to the intersection of two PPAs is investigated. Performance of the proposed method is evaluated via a series of experimental studies. In comparison with the Monte Carlo method and the implicit function method, simulation results show the advantages of the M-D method in the analysis of error propagation in STPs.  相似文献   

Application of nonlinear dynamical systems analysis to conditionally sampled concentration fluctuations of a passive scalar in the atmospheric boundary layer     

Eugene Yee 《Boundary-Layer Meteorology》1991,57(1-2):49-78

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Concentration fluctuation measurements in clouds released from a quasi-instantaneous point source in the atmospheric surface layer     

Eugene Yee  R. Chan  P. R. Kosteniuk  G. M. Chandler  C. A. Biltoft  J. F. Bowers 《Boundary-Layer Meteorology》1994,71(4):341-373

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Measurements of level-crossing statistics of concentration fluctuations in plumes dispersing in the atmospheric surface layer     

Eugene Yee  R. Chan  P. R. Kosteniuk  G. M. Chandler  C. A. Biltoft  J. F. Bowers 《Boundary-Layer Meteorology》1995,73(1-2):53-90

The statistics of level crossings and local extremes in concentration fluctuations in plumes dispersing in the atmosphere have been investigated. A set of concentration fluctuation tracer experiments has been utilized to measure the statistical propertics of the upcrossing interval (inter-arrival time between consecutive concentration bursts), excursion duration (persistence or width of concentration bursts), and concentration amplitude (difference between the maximum and minimum concentrations between successive upcrossings) with respect to a range of concentration crossing levels. In particular, the effect of downwind distance and atmospheric stratification on the level-crossing statistics has been studied in detail. It is shown that the effect of increasing atmospheric stability on level-crossing statistics is similar to the effect of increasing distance from the source in the sense that level-crossing statistics of concentration fluctuations in stable stratification resemble those in neutral stratification, but at a greater downwind distance. It is also found that the distribution of the interval between consecutive upcrossings of a concentration level, as well as the duration of an excursion across a concentration level, can be approximated by a lognormal distribution, whereas the distribution of the concentration amplitude is best characterized by a gamma distribution. Some implications of these results for the modeling of level-crossing statistics of concentration fluctuations are discussed.  相似文献   

An Analytical Model For Threshold Crossing Rates Of Concentration Fluctuations In Dispersing Plumes     

Eugene Yee 《Boundary-Layer Meteorology》2001,98(3):517-527

A simple analytical model is developed for the meanupcrossing rate of plume concentration fluctuations assuming that thisprocess can be well approximated by a lognormal process. The resultingexpression requires only the specification of the in-plume fluctuationintensity and in-plume Taylor micro-time scale and, hence, does notexplicitly involve the joint probability density function of theconcentration and its derivative. The analytical model provides agood fit to some field measurements of the mean upcrossing rate ina dispersing plume.  相似文献   

Reply to the ‘comments on: The PDF of concentration fluctuations’ by Kenneth R. Mylne     

Eugene Yee 《Boundary-Layer Meteorology》1992,61(1-2):195-204

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Wave-photochemistry coupling and its effect on water vapor, ozone and airglow variations in the atmosphere of Mars     

Xun Zhu  Jeng-Hwa Yee 《Icarus》2007,189(1):136-150

A one-dimensional photochemical-transport model for the martian lower atmosphere has been developed to study the diurnal cycles of wave-photochemistry coupling. The model self-consistently calculates water vapor mixing ratio profiles, which exhibit strong vertical and diurnal variations mainly due to the high sensitivity of the saturation vapor pressure to temperature variation. The dynamical coupling of water vapor caused by the temperature variation induced by tidal waves, vertical transport parameterized by eddy diffusion, and linear relaxation introduced in condensation-sublimation processes all have similar timescales of diurnal variation. This leads to a significant asymmetric distribution of water vapor concentration as a function of local time. As a result, the net effect of the temperature variation by tidal waves depletes the water vapor concentration in its diurnal mean. The coupling processes also deplete the diurnally averaged HO_x concentration, which in turn leads to significant enhancements of both ozone concentration and the associated airglow emissions in the martian atmosphere. The model also shows explicitly the importance of photochemical-transport coupling to the airglow emissions and its implications in species retrievals when the photochemical times of the excited states are comparable to the timescale of diurnal variation.  相似文献   

Use of fluorescein as a ground water tracer in brackish water aquifers     

Chua LH  Robertson AP  Yee WK  Shuy EB  Lo EY  Lim TT  Tan SK 《Ground water》2007,45(1):85-88

A drift and pumpback experiment was conducted in a brackish water sandfill. The sandfill was reclaimed from the sea in the eastern part of Singapore and contains sands with low organic and clay/silt contents. The high salinity in the ground water precludes the use of chloride and bromide as tracers in such an environment, and a field experiment was conducted to assess the viability of using fluorescein as a tracer in brackish water aquifers. Nitrate was used as a second tracer to serve as a check. Initial laboratory studies showed that fluorescence was unaffected over the range of electrical conductivity and pH of the ground water. Results from the field experiment show that fluorescein appears to behave conservatively.  相似文献