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111.
Shuping Bi 《Environmental Geology》2001,40(3):300-304
The aim of this paper was to analyze the processing and transport of aluminum speciation through the terrestrial and aquatic
ecosystems of the Chesapeake Bay landscape. Stream waters were sampled in 14 different streams from the Susquehanna River
watershed to the upper reach of Chesapeake Bay. The basic water quality data were documented and Al speciation was evaluated
by modified MINEQL computer model. It was found that the increase in acidity in some of the stream waters near New York were
closely linked with a marked decline in basic cation concentrations. In these areas, the sum of the toxic forms of Al3+ plus AlOH2+ and Al(OH)2
+ concentrations exceeds the critical level of 5 μmol l–1. A potential threat from aluminum may occur.
Received: 3 January 2000 · Accepted: 21 March 2000 相似文献
112.
Christoph M. Menzel Zsolt Berner Doris Stüben 《Geostandards and Geoanalytical Research》2001,25(2-3):239-251
The applicability of size-exclusion chromatography (SEC) coupled online with a high resolution ICP-MS (HR-ICP-MS) to investigate the speciation of the platinum-group elements (PGE), Rh, Pd and Pt, was evaluated. Experiments were carried out to determine the efficiency of different hydrophilic and hydrophobic size-exclusion gel materials to select the optimal eluent in respect of resolution, recovery, reproducibility and limit of detection. The suitability of HR-ICP-MS as a reliable detection instrument at low pg ml−1 levels was investigated by examining possible mass interferences with Rh, Pd and Pt. Laboratory experiments demonstrated the interaction and capability of forming complexes of humic substances with PGE, demonstrating the potential role of these ubiquitous natural substances in the mobilisation of PGE in the environment. 相似文献
113.
The reactivity of dissolved iron compounds towards different pollutants and photooxidants in atmospheric liquid water depends upon the oxidation state and speciation of iron. Our measurements of the oxidation state of dissolved iron eluted from aerosol particles (Dae: 0.4–1.6 m) collected in the urban atmosphere of Ljubljana showed that a large fraction of the iron content is present as Fe(II). The concentration ratio [Fe(II)]/[Fe(III)] varied between 0.9 and 3.1. The kinetics of S(IV) autoxidation catalyzed by Fe(II) under the conditions representative for acidified atmospheric liquid water and the influence of oxalate on this reaction under dark conditions was investigated. The reaction rate is the same if Fe(II) or Fe(III) is used as a catalyst under the condition that Fe(II) can be oxidized in Fe(III), which is the catalytically active species. Oxalate has a strong inhibiting effect on the S(IV) autoxidation in the presence of Fe(II). The reaction is autocatalytic with an induction period, that increases with higher concentrations of oxalate. The inhibiting effect of oxalate differs according to whether iron is initially in the Fe(II) or Fe(III) state. However, in both cases the inhibition by oxalate is a result of the formation of complexes with the catalyst. 相似文献
114.
Claudia Foti Antonio Gianguzza Frank J. Millero Silvio Sammartano 《Aquatic Geochemistry》1999,5(4):381-398
Hydrolysis constants of dimethyltin(IV) cation, in different salt solutions (CaCl2: 0.15 I 0.90; MgCl2: 0.30 I 0.60; NaCl-–NaClO4, NaCl-–NaNO3 mixtures: I = 3; NaCl-–Na2SO4 mixtures: I = 1 mol dm-3) were determined by potentiometric ([H+]-glass electrode) measurements. These data, together with previous data (De Stefano et al., 1996b) were interpreted in terms of DHT (Debye–Hückel type) and Pitzer equations. The mixed electrolyte solution results also allowed us to obtain and parameters for the Pitzer equation. Calorimetric measurements were made at different ionic strengths in order to find the temperature dependence of hydrolysis constants and of the relative interaction parameters. The body of results allows us to determine the speciation of natural waters in a wide range of ionic strengths and temperatures. 相似文献
115.
116.
A decoupling in MORB of measured Th/U (κ = 2.5) from that calculated by Pb isotopes (κ = 3.8) for the depleted asthenosphere is well established, and has been referred to as the second Pb paradox (Kramers, J.D., and Tolstikhin, I.N., 1997. Two terrestrial lead isotope paradoxes, forward transport modelling, core formation and the history of the continental crust. Chem. Geol., 139, 75–110.) or the kappa conundrum (Elliott, T., Zindler, A., and Bourdon, B., 1999. Exploring the kappa conundrum: the role of recycling in the lead isotope evolution of the mantle. Earth Planet. Sci. Lett., 169, 129–145.). More controversial has been the cause and timing of this phenomenon, although a higher return flux of U6+ relative to Th4+ and(or) the recycling of crustal Pb into the mantle have become the preferred explanations of most workers. Such a combined mechanism effectively operating over the past 2.5 Ga was modelled in plumbotectonics (Zartman, R.E., and Haines, S., 1988. The plumbotectonics model for Pb isotopic systematics among major terrestrial reservoirs—a case for bi–directional transport. Geochim. Cosmochim. Acta, 52, 1327–1339. 709.33.), and found to be quantitatively feasible.A large TIMS, SIMS and LA-ICPMS database of Th and U concentrations for kimberlite-hosted zircon, particularly from Cr-poor megacrystic suites, now exists (Kinny et al., 1989, Berryman et al., 1999, Griffin et al., 2000 and Spetsius et al., 2002; Appendix A and Appendix B, this work). Six suites comprising 10 or more zircon grains with ages between 90 and 2550 Ma reveal consistent patterns when plotted on Th/U vs. U diagrams. We interpret these patterns as resulting from fractional crystallization of a melt with kimberlite affinity presumably derived from the asthenosphere, permitting the extrapolation to an initial Th/U at the time zircon crystallization began. A two-fold decrease is seen in this ratio over the past 2.5 Ga, suggesting that during this time a similar change has occurred in the parent silicate melt. Estimates of Th and U distribution coefficients between zircon and coexisting melt permit calculation of Th/U in the melt, which, for these highly incompatible elements, presumably is the same as for its mantle source rock. Kimberlitic zircon may thus indeed give evidence of a reduction in κ, tentatively calculated as from 4 to 2, since the Archean for the depleted asthenosphere. 相似文献
117.
Aya Sakaguchi Masayoshi Yamamoto Keiichi Sasaki Kenji Kashiwaya 《Journal of Paleolimnology》2006,35(4):807-818
Distribution of uranium and thorium isotopes in a short sediment core obtained offshore of the Selenga Delta in Lake Baikal,
Siberia, was investigated to establish their sedimentary behaviors and to look for a linkage to paleoenvironmental changes.
The sediments were composed of dominantly fine detrital materials (70–85%) and a relatively high sedimentation rate (ca. 0.03 cm y−1). The depth profile of 238U content in bulk sediment samples showed a large variation of 70–123 Bq kg−1, while 232Th profile showed a relatively narrow range from 36 to 56 Bq kg−1. The observed 234U/238U activity ratios revealed a marked disequilibrium ranging from 1.53 to 1.84 with a mean value of 1.71 ± 0.07, demonstrating
the presence of 50–80% authigenic 238U in the bulk sediments. The distribution of this authigenic 238U did not display any clear correlation with variations in sediment composition (organic, carbonate, Bio-SiO2 and mineral contents) including grain size median. The profile of terrigenous 238U showed a relatively similar pattern to that of 232Th. Results of sequential leaching indicate that 238U in Fe–Mn oxyhydroxides fractions were responsible for the distribution of authigenic 238U rather than in Bio-SiO2 fraction. The distribution of authigenic 238U in the bottom sediments may be explained by the fluctuation of U adsorption capacity on particles including organic matter
and Fe–Mn oxyhydroxides before they entered the lake. This study highlights the potential use of authigenic and terrigenous
U (Th) signatures in sediments to trace the behavior of U (Th) and to reconstruct environmental (e.g., hydrological) changes
in the lake catchment area. 相似文献
118.
Hui ZHANG 《中国地球化学学报》2006,25(B08):197-197
The speciation of heavy metals is very important to evaluate their environmental impact. This issue has become an interested topic many decades ago and many significative studies were carried out such as direct detecting, calculation with mathematical model represented in recent years as well as Tessier's work in 1979, BCR's work in 1993, etc. In all of them, the methods recommended by Tessier and BCR are most often used in practical study today. But it should be seen that experimental schedule and agents define these methods including BCR's method, which improved on Tessier's method, only. In many cases, there always are deviations between analytical results and real content of the speciation. Otherwise, steps of the extraction experiment are always strict and excessive in the experimental process. The method, which is fitting to extract the speciation of bioavailability and easy to assess the effect of metals in the environment, is very anticipant. In this paper, the sequential three steps schedule of speciation analysis of copper in soil and water sediment is discussed as an example based on the comparative results of experimental analysis with the schedules of BCR's (mended by Rauret et al. in 1999) and TDPA (diethylenetriamine pentacetic acid) extraction, respectively. The results from sequential three steps method and other methods recommended by prevenient work suggest that the analytical schedule of sequential three steps of separating speciation (the speciation of easy effect to life-form, the speciation available to life-form, and the speciation of no effect to life-form) is valuable for copper speciation analysis in soil and sediment. Because of easy process and saving time to evaluate its availability for life form, 相似文献
119.
Hiroshi Tsuno Atsuyuki Ohta Hiroyuki Kagi Noboru Imai Hiroaki Tao Masaharu Nomura 《Geostandards and Geoanalytical Research》2006,30(1):55-62
The oxidation states of chromium in GSJ JSO-2 (artificially contaminated soil) and three other geochemical reference materials (GSJ JSO-1, JLS-1 and JMS-1) were observed using X-ray near edge structure (XANES). For comparison, other artificially contaminated soil materials (mimic-JSO-2) were prepared by adding Cr(VI) into JSO-1. Their oxidation states of chromium were determined using XANES. The chromium contents were 1118 μg g-1 for JSO-2, 1352 μg g-1 for mimic-JSO-2 and 69-113 μg g-1 for the other reference materials. Most chromium was present as hexavalent in mimic-JSO-2. No hexavalent species were detected in other samples. These results for chromium oxidation state in JSO-2 and mimic-JSO-2 obtained with XANES resembled those obtained from a chemical extraction method. The present JSO-2 has no trace of Cr(VI), although Cr(VI) was added as a major species during preparation. On the other hand, the content of Cr(VI) obtained in mimic-JSO-2 agreed with the original Cr(VI) content. A time-elapse study showed that Cr(VI) contents in mimic-JSO-2 decreased gradually to 70% of the original abundance during 240-day preservation in dry conditions. Moreover, the abundance of Cr(VI) decreased markedly to 15% after 240 days in the wet mimic-JSO-2 containing 20% m/m of water. These experiments suggested that soil humidity enhanced the reduction of Cr(VI) and that Cr(VI) was reduced even in dry conditions. Consequently, it is reasonable to infer that Cr(VI) doped into JSO-2 was completely reduced to Cr(III) during the preservation period of 5 years. The certification of the long-term stability of the chemical form in reference materials will be much more important in future. 相似文献
120.
Kathryn L. Linge 《Geostandards and Geoanalytical Research》2006,30(3):157-174
This review describes significant developments in trace element determination using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS) that were reported in 2004 and 2005. It focuses on the application of ICP techniques to geological and environmental samples; fundamental studies in ICP-MS and ICP-AES instrumentation are not included. The literature reviewed indicated that the majority of new publications concerned advances in ICP-MS analysis rather than ICP-AES. However, ICP-AES developments are still being published, particularly in the areas of sample preconcentration and sample introduction. The trend in increasing publication of developments in hyphenated speciation techniques looks set to persist as knowledge of elemental speciation becomes critical for many environmental studies. Collision or reactions cells were the most reported technique for spectral interference removal in ICP-MS, probably reflecting the growing adoption of cell instruments in laboratories during the last few years. 相似文献