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1.
The kinetics of the formation of the purple-colored species between FeIII-EDTA and peroxynitrite were studied as a function of pH (10.4–12.3) at 22°C in aqueous solutions using a stopped-flow technique. A purple-colored species was immediately formed upon mixing, which had an absorbance maximum at 520 nm. The increase in absorbance with time could be fit empirically by a power function with two parameters a and b. The power equation determined was absorbance = a*t b , where a increased linearly with pH and the concentration of peroxynitrite, while b almost remained constant with a value of ~0.25. The molar extinction coefficient ε520 nm for the colored species was determined as 13 M−1cm−1, which is much lower than ε520 nm = 520 M−1 cm−1 for the [FeIII(EDTA)O2]3−, a purple species observed in the FeIII–EDTA–H2O2 system. The results of kinetics and spectral measurements of the present study are briefly discussed and compared with those of the reaction between Fe(III)-EDTA and hydrogen peroxide.  相似文献   

2.
Laboratory culture experiments have been conducted to evaluate the effects of light intensity on the growth of Cryptomonas sp. (Cryptophyceae) and the discrepancy in absorption of iron and phosphorus under different light conditions. Results show that there is an exponential correlation between algal growth rate and light intensity. The saturating and semi-saturating light values for Cryptomonas sp. cells are 150 and 47 μmol photons m−2 s−1, respectively. More uptake of Fe, P, and other trace elements such as Zn, Mn, Co, and Mo is observed in the low light cultures, although the algal growth rates are slow. The growth rate at 10 μmol photons m−2 s−1 is only 10% of that at 150 μmol photons m−2 s−1, whereas Fe and P uptake increases by 150 and 100%, respectively. These results suggest potential implications of differentiation in absorption of iron and phosphorus at different light intensities for the occurrence of harmful algal blooms (HABs). The mechanisms of light intensity regulating nutrient uptake as well as the occurrence of HABs are also discussed.  相似文献   

3.
OH in zoned amphiboles of eclogite from the western Tianshan,NW-China   总被引：1，自引：0，他引：1  
Chemically-zoned amphibole porphyroblast grains in an eclogite (sample ws24-7) from the western Tianshan (NW-China) have been analyzed by electron microprobe (EMP), micro Fourier-transform infrared (micro-FTIR) and micro-Raman spectroscopy in the OH-stretching region. The EMP data reveal zoned amphibole compositions clustering around two predominant compositions: a glaucophane end-member ( B Na2 C M2+ 3 M3+ 2 T Si8(OH)2) in the cores, whereas the mantle to rim of the samples has an intermediate amphibole composition ( A 0.5 B Ca1.5Na0.5 C M 2+ 4.5 M 0.53+ T Si7.5Al0.5(OH)2) (A = Na and/or K; M 2+ = Mg and Fe2+; M 3+ = Fe3+ and/or Al) between winchite (and ferro-winchite) and katophorite (and Mg-katophorite). Furthermore, we observed complicated FTIR and Raman spectra with OH-stretching absorption bands varying systematically from core to rim. The FTIR/Raman spectra of the core amphibole show three lower-frequency components (at 3,633, 3,649–3,651 and 3,660–3,663 cm−1) which can be attributed to a local O(3)-H dipole surrounded by M(1) M(3)Mg3, M(1) M(3)Mg2Fe2+ and M(1) M(3) Fe2+ 3, respectively, an empty A site and T Si8 environments. On the other hand, bands at higher frequencies (3,672–3,673, 3,691–3,697 and 3,708 cm−1) are observable in the rims of the amphiboles, and they indicate the presence of an occupied A site. The FTIR and Raman data from the OH-stretching region allow us to calculate the site occupancy of the A, M(1)–M(3), T sites with confidence when combined with EPM data. By contrast M(2)- and M(4) site occupancies are more difficult to evaluate. We use these samples to highlight on the opportunities and limitations of FTIR OH-stretching spectroscopy applied to natural high pressure amphibole phases. The much more detailed cation site occupancy of the zoned amphibole from the western Tianshan have been obtained by comparing data from micro-chemical and FTIR and/or Raman in the OH-stretching data. We find the following characteristic substitutions Si(T-site) (Mg, Fe)[M(1)–M(3)-site] → Al(T-site) Al[M(1)–M(3)-site] (tschermakite), Ca(M4-site)□ (A-site) → Na(M4-site) Na + K(A-site) (richterite), and Ca(M4-site) (Mg, Fe) [M(1)–M(3)-site] → Na(M4-site) Al[M(1)–M(3)-site] (glaucophane) from the configurations observed during metamorphism.  相似文献   

4.
The thermoelastic behaviour of anthophyllite has been determined for a natural crystal with crystal-chemical formula ANa0.01 B(Mg1.30Mn0.57Ca0.09Na0.04) C(Mg4.95Fe0.02Al0.03) T(Si8.00)O22 W(OH)2 using single-crystal X-ray diffraction to 973 K. The best model for fitting the thermal expansion data is that of Berman (J Petrol 29:445–522, 1988) in which the coefficient of volume thermal expansion varies linearly with T as α V,T  = a 1 + 2a 2 (T − T 0): α298 = a 1 = 3.40(6) × 10−5 K−1, a 2 = 5.1(1.0) × 10−9 K−2. The corresponding axial thermal expansion coefficients for this linear model are: α a ,298 = 1.21(2) × 10−5 K−1, a 2,a  = 5.2(4) × 10−9 K−2; α b ,298 = 9.2(1) × 10−6 K−1, a 2,b  = 7(2) × 10−10 K−2. α c ,298 = 1.26(3) × 10−5 K−1, a 2,c  = 1.3(6) × 10−9 K−2. The thermoelastic behaviour of anthophyllite differs from that of most monoclinic (C2/m) amphiboles: (a) the ε 1 − ε 2 plane of the unit-strain ellipsoid, which is normal to b in anthophyllite but usually at a high angle to c in monoclinic amphiboles; (b) the strain components are ε 1 ≫ ε 2 > ε 3 in anthophyllite, but ε 1 ~ ε 2 ≫ ε 3 in monoclinic amphiboles. The strain behaviour of anthophyllite is similar to that of synthetic C2/m ANa B(LiMg) CMg5 TSi8 O22 W(OH)2, suggesting that high contents of small cations at the B-site may be primarily responsible for the much higher thermal expansion ⊥(100). Refined values for site-scattering at M4 decrease from 31.64 epfu at 298 K to 30.81 epfu at 973 K, which couples with similar increases of those of M1 and M2 sites. These changes in site scattering are interpreted in terms of Mn ↔ Mg exchange involving M1,2 ↔ M4, which was first detected at 673 K.  相似文献   

5.
Horizontal, vertical and temporal distribution of a cyclonic (counterclockwise) eddy, where biological productivity is high, downstream of the Tsushima Islands in the eastern channel of the Tsushima Straits in November 2007 was revealed using conductivity–temperature–depth and acoustic Doppler current profiler data. The eddy had a horizontal scale of approximately 40–60 km, and the accompanying baroclinic current was more than 15 cm s−1 at the edge of the eddy. The island-induced cyclonic eddy moved east-northeastward at about 10 km day−1 (∼10 cm s−1) along the Tsushima Warm Current and was intensified by the barotropic instability in the current shear. The cyclonic eddy with high surface chlorophyll a concentrations intensified in the vicinity of the Tsushima Islands and was advected by the Tsushima Warm Current towards the southwestern Japan Sea.  相似文献   

6.
The thermoelastic behavior of a natural clintonite-1M [with composition: Ca1.01(Mg2.29Al0.59Fe0.12)Σ3.00(Si1.20Al2.80)Σ4.00O10(OH)2] has been investigated up to 10 GPa (at room temperature) and up to 960°C (at room pressure) by means of in situ synchrotron single-crystal and powder diffraction, respectively. No evidence of phase transition has been observed within the pressure and temperature range investigated. P–V data fitted with an isothermal third-order Birch–Murnaghan equation of state (BM-EoS) give V 0 = 457.1(2) ?3, K T0 = 76(3)GPa, and K′ = 10.6(15). The evolution of the “Eulerian finite strain” versus “normalized stress” shows a linear positive trend. The linear regression yields Fe(0) = 76(3) GPa as intercept value, and the slope of the regression line leads to a K′ value of 10.6(8). The evolution of the lattice parameters with pressure is significantly anisotropic [β(a) = 1/3K T0(a) = 0.0023(1) GPa−1; β(b) = 1/3K T0(b) = 0.0018(1) GPa−1; β(c) = 1/K T0(c) = 0.0072(3) GPa−1]. The β-angle increases in response to the applied P, with: βP = β0 + 0.033(4)P (P in GPa). The structure refinements of clintonite up to 10.1 GPa show that, under hydrostatic pressure, the structure rearranges by compressing mainly isotropically the inter-layer Ca-polyhedron. The bulk modulus of the Ca-polyhedron, described using a second-order BM-EoS, is K T0(Ca-polyhedron) = 41(2) GPa. The compression of the bond distances between calcium and the basal oxygens of the tetrahedral sheet leads, in turn, to an increase in the ditrigonal distortion of the tetrahedral ring, with ∂α/∂P ≈ 0.1°/GPa within the P-range investigated. The Mg-rich octahedra appear to compress in response to the applied pressure, whereas the tetrahedron appears to behave as a rigid unit. The evolution of axial and volume thermal expansion coefficient α with temperature was described by the polynomial α(T) = α0 + α1 T −1/2. The refined parameters for clintonite are as follows: α0 = 2.78(4) 10−5°C−1 and α1 = −4.4(6) 10−5°C1/2 for the unit-cell volume; α0(a) = 1.01(2) 10−5°C−1 and α1(a) = −1.8(3) 10−5°C1/2 for the a-axis; α0(b) = 1.07(1) 10−5°C−1 and α1(b) = −2.3(2) 10−5°C1/2 for the b-axis; and α0(c) = 0.64(2) 10−5°C−1 and α1(c) = −7.3(30) 10−6°C1/2for the c-axis. The β-angle appears to be almost constant within the given T-range. No structure collapsing in response to the T-induced dehydroxylation was found up to 960°C. The HP- and HT-data of this study show that in clintonite, the most and the less expandable directions do not correspond to the most and the less compressible directions, respectively. A comparison between the thermoelastic parameters of clintonite and those of true micas was carried out.  相似文献   

7.
The Fe M 2,3-edge spectra of solid solutions of garnets (almandine-skiagite Fe3(Al1–xFex)2[SiO4]3 and andradite-skiagite (Fe1–xCax)3Fe2[SiO4]3), pyroxenes (acmite-hedenbergite (Ca1–xNax)(Fe2+ 1−xFe3+ x)Si2O6), and spinels (magnetite-hercynite Fe(Al1–xFex)2O4) have been measured using the technique of parallel electron energy-loss spectroscopy (EELS) conducted in a transmission electron microscope (TEM). The Fe M 2,3 electron energy-loss near-edge structures (ELNES) of the minerals exhibit a characteristic peak located at 4.2 eV and 2.2 eV for trivalent and divalent iron, respectively, prior to the main maximum at about 57 eV. The intensity and energy of the pre-edge feature varies depending on Fe3+/ΣFe. We demonstrate a new quantitative method to extract the ferrous/ferric ratio in minerals. A systematic relationship between Fe3+/ΣFe and the integral intensity ratio of the main maximum and the pre-edge peak of the Fe M 2,3 edge is observed. Since the partial cross sections of the Fe M 2,3 edges are some orders of magnitude higher than those of the Fe L 2,3 edges, the Fe M 2,3 edges are interesting for valence-specific imaging of Fe. The possibility of iron valence-specific imaging is illustrated by Fe M 2,3-ELNES investigations with high lateral resolution from a sample of ilmenite containing hematite exsolution lamellae that shows different edge shapes consistent with variations in the Fe3+/ΣFe ratio over distances on the order of 100 nm. Received: 14 April 1998 / Revised, accepted: 8 March 1999  相似文献   

8.
Benthic oxygen, dinitrogen, and nutrient fluxes (NH4+, NO3−, and PO43−) were measured monthly during a 1-year period at two locations in Weeks Bay, a shallow (1.4 m) and eutrophic estuary in Alabama. Gross primary productivity (GPP), ecosystem respiration (R), and net ecosystem metabolism were determined from high-frequency dissolved oxygen measurements. Peak water column NO3− (55 μM) and chlorophyll a (138 μg/l) concentrations were measured during spring and fall, respectively. Sediments were a net source of NH4+ (102 μmol m−2 h−1) and PO43− (0.9 μmol m−2 h−1) but a sink for NO3− (−30 μmol m−2 h−1). Benthic N2 fluxes indicated net N fixation (12 μmol N m−2 h−1). Sediment oxygen demand (0.55 g O2 m−2 day−1) accounted for <10% of R (7.3 g O2 m−2 day−1). Despite high GPP rates (4.7 g O2 m−2 day−1), the estuary was net heterotrophic. Benthic regeneration supplied, on average, 7.5% and 4% of primary productivity N and P demands, respectively. These results contrast with the conventional view that benthic regeneration accounts for a large fraction of phytoplankton nutrient demand in shallow estuaries.  相似文献   

9.
Phengite samples (2M 1 and 3T politypes) and a synthetic end-member muscovite specimen were studied by in situ high-temperature synchrotron radiation X-ray diffraction. The measured volume thermal expansion of 2M 1 phengite (<α V> ≈ 36.6 × 10−6 K−1) was systematically greater than <α V> of the 3T polytype (≈33.3 × 10−6 K−1). A positive linear correlation between the average thermal expansion on (001) plane and the mean tetrahedral rotation angle at ambient condition is proposed on the ground of new measurements and literature data. Dehydroxylation processes were observed in 2M 1, starting at 1,000 K in 3T at 800 and 945 K in synthetic muscovite. Rietveld refinements allowed a determination of structural variations upon heating of phengite samples and their dehydroxylate phases. The phengite structure expands by regularizing the tetrahedral sheet and by reducing the bond length differences between the outer and inner coordination shell of the interlayer site. The dehydroxylate phase derived from 2M 1 is characterized by fivefold polyhedra in the low temperature form as a consequence of two OH groups reacting to form H2O + O (residual). The dehydroxylate exhibits an increase of the cation–cation distances along the M–Or–M bonds with respect to low-temperature phengite structures. For the 3T phase, we were unable to achieve completion of dehydroxylation. The refined structural model of the dehydroxylate phase shows two hydroxyl sites, but at a short distance from one another. This result suggests that the dehydroxylation reaction did not proceed to completion. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

10.
Surface water optical characteristics, nutrients, and planktonic chlorophyll a concentrations were analyzed in the Cape Fear River (CFR) plume over a 2-year period. CFR discharge during the dry year (109 ± 105 m3s−1) was only 25% of the wet year discharge (429 ± 337 m3s−1). Partitioning the contributions of phytoplankton pigments, non-pigmented particles, and colored dissolved organic matter (CDOM) to the absorption of photosynthetically active radiation (PAR) indicated that CDOM was the dominant contributor to PAR absorption. Particulate absorption was relatively greater during the dry year. Pigment absorption was minor and varied little among stations or between years. Chlorophyll a concentrations were reduced at the most plume-influenced stations during the wet year, despite lower turbidity and higher nitrate concentrations. Ammonium and orthophosphate concentrations were not different between years. CDOM absorption [a CDOM (412)] ranged from 0.05 to 8.25 m−1 with highest values occurring near the CFR mouth. Our results suggest that for coastal ecosystems with significant blackwater river inputs, CDOM may exert a major limiting influence over near-shore primary production.  相似文献   

11.
Simulated acidic precipitation (1:1 equivalent basis H2SO4:HNO3) at pH values of 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 7.0 were conducted using column leaching to determine impacts of simulated acid rain on phosphorus (P) leaching from a calcareous sandy loam soil over a 40-day period. Soil columns were irrigated every day to make a total of 1,061 mm, equivalent to 3.5 years of rainfall (based on average annual rainfall). Leachates were collected and analyzed for anions and cations. There was significant nonlinear correlation between the amount of P leached and the simulated acid rain (R 2 = 0.61). Losses of P from the pH 2.5 and 7.0 treatments were 1.23, and 1.32 mg kg−1, respectively. The results showed that the amount of P leached from pH 4 (1.46 mg kg−1) and 5 treatments (1.52 mg−1 kg−1) were significantly larger than other treatments. Linear equation adequately described leaching of P in different treatments. The slope (mg kg−1 day−1) in the linear equation was defined as the leaching rate and for the pH 2.5 was 0.0354, and 0.0382 and 0.0406 for pH 4.5 and 7.0, respectively. The geochemical code Visual MINTEQ was used to calculate saturation indices. Leaching of P in different treatments was controlled by rate-limited dissolution of hydroxyapatite, β-tricalcium phosphate and to some extent octacalcium phosphate. The results indicate that acid rain in calcareous sandy loam soils may pose a risk in terms of groundwater contamination with P.  相似文献   

12.
The thermo-elastic behavior of a natural epidote [Ca1.925 Fe0.745Al2.265Ti0.004Si3.037O12(OH)] has been investigated up to 1,200 K (at 0.0001 GPa) and 10 GPa (at 298 K) by means of in situ synchrotron powder diffraction. No phase transition has been observed within the temperature and pressure range investigated. P–V data fitted with a third-order Birch–Murnaghan equation of state (BM-EoS) give V 0 = 458.8(1)Å3, K T0 = 111(3) GPa, and K′ = 7.6(7). The confidence ellipse from the variance–covariance matrix of K T0 and K′ from the least-square procedure is strongly elongated with negative slope. The evolution of the “Eulerian finite strain” vs “normalized stress” yields Fe(0) = 114(1) GPa as intercept values, and the slope of the regression line gives K′ = 7.0(4). The evolution of the lattice parameters with pressure is slightly anisotropic. The elastic parameters calculated with a linearized BM-EoS are: a 0 = 8.8877(7) Å, K T0(a) = 117(2) GPa, and K′(a) = 3.7(4) for the a-axis; b 0 = 5.6271(7) Å, K T0(b) = 126(3) GPa, and K′(b) = 12(1) for the b-axis; and c 0 = 10.1527(7) Å, K T0(c) = 90(1) GPa, and K’(c) = 8.1(4) for the c-axis [K T0(a):K T0(b):K T0(c) = 1.30:1.40:1]. The β angle decreases with pressure, βP(°) = βP0 −0.0286(9)P +0.00134(9)P 2 (P in GPa). The evolution of axial and volume thermal expansion coefficient, α, with T was described by the polynomial function: α(T) = α0 + α1 T −1/2. The refined parameters for epidote are: α0 = 5.1(2) × 10−5 K−1 and α1 = −5.1(6) × 10−4 K1/2 for the unit-cell volume, α0(a) = 1.21(7) × 10−5 K−1 and α1(a) = −1.2(2) × 10−4 K1/2 for the a-axis, α0(b) = 1.88(7) × 10−5 K−1 and α1(b) = −1.7(2) × 10−4 K1/2 for the b-axis, and α0(c) = 2.14(9) × 10−5 K−1 and α1(c) = −2.0(2) × 10−4 K1/2 for the c-axis. The thermo-elastic anisotropy can be described, at a first approximation, by α0(a): α0(b): α0(c) = 1 : 1.55 : 1.77. The β angle increases continuously with T, with βT(°) = βT0 + 2.5(1) × 10−4 T + 1.3(7) × 10−8 T 2. A comparison between the thermo-elastic parameters of epidote and clinozoisite is carried out.  相似文献   

13.
Arsenic and Antimony in Groundwater Flow Systems: A Comparative Study   总被引：3，自引：0，他引：3  
Arsenic (As) and antimony (Sb) concentrations and speciation were determined along flow paths in three groundwater flow systems, the Carrizo Sand aquifer in southeastern Texas, the Upper Floridan aquifer in south-central Florida, and the Aquia aquifer of coastal Maryland, and subsequently compared and contrasted. Previously reported hydrogeochemical parameters for all three aquifer were used to demonstrate how changes in oxidation–reduction conditions and solution chemistry along the flow paths in each of the aquifers affected the concentrations of As and Sb. Total Sb concentrations (SbT) of groundwaters from the Carrizo Sand aquifer range from 16 to 198 pmol kg−1; in the Upper Floridan aquifer, SbT concentrations range from 8.1 to 1,462 pmol kg−1; and for the Aquia aquifer, SbT concentrations range between 23 and 512 pmol kg−1. In each aquifer, As and Sb (except for the Carrizo Sand aquifer) concentrations are highest in the regions where Fe(III) reduction predominates and lower where SO4 reduction buffers redox conditions. Groundwater data and sequential analysis of the aquifer sediments indicate that reductive dissolution of Fe(III) oxides/oxyhydroxides and subsequent release of sorbed As and Sb are the principal mechanism by which these metalloids are mobilized. Increases in pH along the flow path in the Carrizo Sand and Aquia aquifer also likely promote desorption of As and Sb from mineral surfaces, whereas pyrite oxidation mobilizes As and Sb within oxic groundwaters from the recharge zone of the Upper Floridan aquifer. Both metalloids are subsequently removed from solution by readsorption and/or coprecipitation onto Fe(III) oxides/oxyhydroxides and mixed Fe(II)/Fe(III) oxides, clay minerals, and pyrite. Speciation modeling using measured and computed Eh values predicts that Sb(III) predominate in Carrizo Sand and Upper Floridan aquifer groundwaters, occurring as the Sb(OH)30 species in solution. In oxic groundwaters from the recharge zones of these aquifers, the speciation model suggests that Sb(V) occurs as the negatively charged Sb(OH)6− species, whereas in sufidic groundwaters from both aquifers, the thioantimonite species, HSb2S4 − and Sb2S4 2−, are predicted to be important dissolved forms of Sb. The measured As and Sb speciation in the Aquia aquifer indicates that As(III) and Sb(III) predominate. Comparison of the speciation model results based on measured Eh values, and those computed with the Fe(II)/Fe(III), S(-II)/SO4, As(III)/As(V), and Sb(III)/Sb(V) couples, to the analytically determined As and Sb speciation suggests that the Fe(II)/Fe(III), S(-II)/SO4 couples exert more control on the in situ redox condition of these groundwaters than either metalloid redox couple.  相似文献   

14.
Creep strength of oriented orthopyroxene single crystals was investigated via shear deformation experiments under lithospheric conditions [P (pressure) = 1.3 GPa and T (temperature) = 973–1,373 K]. For the A-orientation (shear direction [001] on (100) plane), the samples have transformed completely to clinoenstatite and much of the deformation occurred after transformation. In contrast, for the B-orientation (shear direction [001] on (010) plane), samples remained orthoenstatite and deformation occurred through dislocation motion in orthoenstatite. The strength of orthopyroxene with these orientations is smaller than for olivine aggregates under all experimental conditions. Flow of the B-orientation samples is described by a power-law, and the pre-exponential constant, the apparent activation energy, and the stress exponent are determined to be A = 10−9.5 s−1·MPa−4.2, Q = 114 kJ/mol and n = 4.2. However, for the A-orientation, the results cannot be fit by a single flow law and we obtained the following: A = 108.9 s−1·MPa−3.0, Q = 459 kJ/mol and n = 3.0 at high temperatures (≥1,173 K), and A = 10−27.4 s−1·MPa−14.3, Q = 296 kJ/mol and n = 14.3 at low temperatures (<1,173 K). The stress exponent for the low-temperature regime is high, suggesting that deformation involves some processes where the activation energy decreases with stress such as the Peierls mechanism. Our study shows that orthopyroxene with these orientations is significantly weaker than olivine under the lithospheric conditions suggesting that orthopyroxene may reduce the strength of the lithosphere, although the extent to which orthopyroxene weakens the lithosphere depends on its orientation and connectivity.  相似文献   

15.
The chemical quality of groundwater of western Haryana, India was assessed for its suitability for drinking purposes. A total of 275 water samples were collected from deep aquifer based hand-pumps situated in 37 different villages/towns of Bhiwani region. The water samples were analyzed for different physico-chemical properties, e.g., pH, total dissolved solids (TDS), total harness (TH), total alkalinity (TA), calcium, magnesium, carbonate, bicarbonate, sulphate, chloride and fluoride concentrations. In this study, the average TDS content was greater ranging 1,692 (Bhiwani block) to 2,560 mg l−1 (Siwani block), and other important parameters of water, e.g., TA (442–1,232 mg l−1), TH (437–864 mg l−1) and bicarbonate (554–672 mg l−1), were also higher than maximum permissible limit by WHO or BIS. The fluoride appeared as a major problem of safe drinking water in this region. We recorded greater fluoride concentration, i.e., 86.0 mg l−1 from Motipura village that is highest fluoride level ever recorded for Haryana state. The average fluoride concentration ranged between 7.1 and 0.8 mg l−1 in different blocks of western Haryana. On the basis of fluoride concentration, Siwani block showed the maximum number of water samples (84% of total collected samples) unsuitable for drinking purposes (containing fluoride >1.5 mg l−1) followed by Charki Dadri block (58%), Bhiwani block (52%), Bawani Khera block (33%) and Loharu block (14%). This study clearly suggest that some health deteriorating chemicals in drinking water were at dangerous level and; therefore, water quality could be a major health threat for local residents of western Haryana. The high fluoride level in drinking water has posed some serious dental health risks in local residents.  相似文献   

16.
This article reported a wind tunnel test of sediment transport related to surface moisture content and wind velocity using sands from tropical humid coastal area. A 1 mm-thick portion of surface sand was scraped using a self-made sediment sampler, and the gravimetric moisture content was determined. Sand transport was measured via a standard vertical sand trap with a 60 cm height. The result shows that the sand transport profile above the wet surface can be expressed with an exponential equation. In general, the influence of moisture content on sand transport profile mainly focuses on the bottom of the blowing sand cloud. Meanwhile, with moisture content increased, total sand transport dropped, and a relatively larger proportion is transported at greater heights. The vertical movement of particles on higher moisture surface (0.587% < M < 1.448%) is more sensitive to moisture content variation as compared to those on low wet surface (M < 0.587%), total sand transport rate tends to be rather low (0.99 g cm−1 s−1) when M > 1.448%. The total sand transport rate varying with moisture content is divided into three regions of differing gradient at the moisture contents of 0.587 and 1.448%. The gradient of the curve reflected the different influences of the various water forms in surface sediments. The higher moisture surface (M > 1.448%) merely functions as a transport plain for the saltation material. Surface moisture content was the dominant control factor for saltation activity between the moisture contents of 0.587 and 1.448%, wind velocity could resume control saltation after the surface dried to the extent (M < 0.587%).  相似文献   

17.
A sulfur hexafluoride (SF6) tracer release experiment was conducted in the Stockton Deep Water Ship Channel (DWSC) to quantify mixing and transport rates. SF6 was injected in the San Joaquin River upstream of the DWSC and mapped for 8 days. From the temporal change in SF6 distributions, the longitudinal dispersion coefficient (K x ) was determined to be 32.7 ± 3.6 m2 s−1 and the net velocity was 1.75 ± 0.03 km day−1. Based on the decrease in SF6 inventory during the experiment, the pulsed residence time for waters in the DWSC was estimated at ∼17 days. Within the DWSC from Stockton downstream to Turner Cut, dissolved oxygen concentrations maintained a steady state value of 4 mg l−1. These values are below water quality objectives for the time of year. The low flow rates observed in the DWSC and the inability of oxygen-rich waters from downstream to mix into the DWSC upstream of Turner Cut contribute to the low dissolved oxygen concentration.  相似文献   

18.
Acid mine drainage (AMD) is a common pollution in mining areas due to the oxidation of pyrite and associated sulfide minerals at mines, tailings and mine dumps. Elevated metals (Fe, Mn, Al) and metalloids (As, Hg) in AMD would deteriorate the local aquatic environment and influence the water supply. A carbonate basin with deposits of high-arsenic coal in Xingren County, southwestern China, was chosen to study the behavior of As and other chemical constituents along a river receiving AMD. Heavy metals (Fe, Mn) and major ions such as (Ca2+, Mg2+, Cl−, SO4 2−) in surface water, and As in sediment and surface water were analyzed. It was found that high concentrations of SO4 2− (1,324–7,560 mg/L) and Fe (369–1,472 mg/L) in surface water were mainly controlled by the interactions between water and rocks such as the oxidation of pyrite in the local coal seams, precipitation and adsorption of iron minerals. Although ubiquitous carbonate minerals in the bedrock and the riverbeds, low pH (<3) water was maintained until 2 km downstream from the AMD source due to the Fe(hydro)oxide minerals coating on the surface of carbonate minerals to restrain the neutralization of acidic water. Moreover, the formation of Fe(hydro)oxide precipitations absorbed As was dominated the attenuation of As from water to sediment. Whereas, the dilution also played an important role in decrease of As in river water.  相似文献   

19.
Hydraulic properties of the crystalline basement   总被引：1，自引：1，他引：1  
Hydraulic tests in boreholes, up to 4.5 km deep, drilled into continental crystalline basement revealed hydraulic conductivity (K) values that range over nine log-units from 10−13−10−4 m s−1. However, K values for fractured basement to about 1 km depth are typically restricted to the range from 10−8 to 10−6 m s−1. New data from an extended injection test at the KTB research site (part of the Continental Deep Drilling Program in Germany) at 4 km depth provide K=5 10−8 m s−1. The summarized K-data show a very strong dependence on lithology and on the local deformation history of a particular area. In highly fractured regions, granite tends to be more pervious than gneiss. The fracture porosity is generally saturated with Na–Cl or Ca–Na–Cl type waters with salinities ranging from <1 to >100 g L−1. The basement permeability is well within the conditions for advective fluid and heat transport. Consequently, fluid pressure is hydrostatic and a Darcy flow mechanism is possible to a great depth. Topography-related hydraulic gradients in moderately conductive basement may result in characteristic advective flow rates of up to 100 L a−1 m−2 and lead to significant advective heat and solute transfer in the upper brittle crust. An erratum to this article can be found at  相似文献   

20.
In order to avoid the pollution of trace metals in marine environment, it is necessary to establish the data and understand the mechanisms influencing the distribution of trace metals in marine environment. The concentration of heavy metals (Fe, Mn, Cr, Cu, Ni, Pb, Zn, Co and Cd) were studied in sediments of Ennore shelf, to understand the metal contamination due to heavily industrialized area of Ennore, south-east coast of India. Concentration of metals shows significant variability and range from 1.7 to 3.7% for Fe, 284–460 μg g−1 for Mn, 148.6–243.2 μg g−1 for Cr, 385–657 μg g−1 for Cu, 19.8–53.4 μg g−1 for Ni, 5.8–11.8 μg g−1 for Co, 24.9–40 μg g−1 for Pb, 71.3–201 μg g−1 for Zn and 4.6–7.5 μg g−1 for Cd. For various metals the contamination factor (CF) and geoaccumulation index (I geo) has been calculated to assess the degree of pollution in sediments. The geoaccumulation index shows that Cd, Cr and Cu moderately to extremely pollute the sediments. This study shows that the major sources of metal contamination in the Ennore shelf are land-based anthropogenic ones, such as discharge of industrial wastewater, municipal sewage and run-off through the Ennore estuary. The intermetallic relationship revealed the identical behavior of metals during its transport in the marine environment.  相似文献   

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