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141.
142.
Jean-Luc Loizeau Daniel Span Véronique Coppee Janusz Dominik 《Journal of Paleolimnology》2001,25(2):205-214
Lake Annecy sediments have been studied to provide an insight into the evolution of the lake trophic state in response to climate changes during the Holocene. Determination of the concentration of carbonate, Fe, Mn, and different forms of P in conjunction with total sediment fluxes derived from 14C ages allows an estimation of yearly fluxes of these sediment components. High fluxes of endogenic carbonate occur during the early to middle Holocene. Non apatitic inorganic phosphorus flux is variable but shows some higher-than-present values during this period. These observations are interpreted as being a result of enhanced productivity by favourable conditions for phytoplankton development. In addition, the low Mn/Fe ratio of the redox-sensitive forms of these elements recorded during this period suggests low oxygen concentrations in the bottom waters. Therefore it appears that the lake may have undergone oxygen depletion in the bottom water during the warmer-than-present periods, due to increased productivity and subsequent oxygen consumption from the decay of organic matter. With future climate changes, this suggests that lake water quality may likely degrade under global warming. 相似文献
143.
Post-mine metal transport and attenuation in the Keno Hill mining district, central Yukon, Canada 总被引:6,自引:0,他引:6
The Keno Hill mining district in central Yukon was the second largest silver producer in Canada with mines operating from
1913 to 1989 on more than 65 vein silver deposits. The seven and a half decades of mining activities have generated large
volumes of mine waste disposed on the land surface, resulting in elevated metal contents in numerous small drainages. To assess
the extent of metal mobilization, old mine workings and the associated mine waste were examined and the water courses draining
to a major river valley sampled. The results of field observations and an array of water and sediment analyses led to three
major conclusions. 1. Acid mine drainage is not widespread because of galvanic protection of pyrite from oxidative dissolution
and neutralization by carbonates in the country rock. 2. Mechanisms operative to limit aqueous metal transport in small streams
in the district include cryogenic precipitation, coprecipitation and sorption. 3. The near-surface concentration of metals
limits the options of waste disposal in future mining developments due to potential metal-leaching problems.
Received: 12 December 1995 · Accepted: 26 March 1996 相似文献
144.
本文将NaDDC—泡塑用于分离富集天然水中的痕量镉。对富集和洗脱条件、共存离子的影响及干扰的消除作了详细研究。试验结果表明,在pH8—10的氨性环境,以柠檬酸和酒石酸作掩蔽剂,NaDDC—泡塑可定量富集天然水中的痕量镉。每克NaDDC—泡塑对镉的饱和富集容量高达45mg。富集于NaDDC—泡塑上的镉用2%磺基水杨酸在沸水浴中定量洗脱后,可直接用火焰AAS法测定。 相似文献
145.
Previous work has shown that the type and pH history of an aerosol governs trace metal solubility in rainwater. This study concentrates on the crustal elements Al, Fe and Mn and identifies additional processes which affect dissolution not only in the atmosphere but also on mixing into seawater. Aerosol dissolution experiments (at aerosol concentrations of about 30 mg 1–1) show manganese exhibiting high solubility at the low pH values typical of clouds (54±2.5% at pH 2, with results expressed in mole percent units) with 85% of this increase occurring within 6 hours of acidification. The percentage dissolution decreases to 50% at pH values representative of rainwater (pH 5.5) and to 26±4% at pH 8, typical of seawater. No such dramatic solution phase removal occurs at pH 8 in the presence of inorganic anions (to a final solubility of 44±2%). Thus the extent of manganese dissolution depends strongly on whether aerosols are cycled through acidic environments and on subsequent inorganic complexation once rainwater mixes into sea. Aluminium shows highest dissolution (7.1±0.6%) at low pH with 78% of this increase occurring within 6 hours of acidification. Rapid solution phase removal occurs on increasing the pH to that representative of rainwater (to 0.9±0.4% with 87% of this decrease occurring within 15 min). As a consequence of acid cycling and aluminium's amphoteric nature, solubility is enhanced at seawater pH (2.3±0.3%) over that in rain. Iron shows a strong pH-solubility relationship with highest solubility at low pH (4.7±0.2%), 70% of this value being reached within 6 hours of acidification, and decreasing rapidly to 0.17% as pH is raised to 8. Addition of inorganic anions at pH 8 to simulate mixing into seawater causes a further decrease in solubility, perhaps due to anion induced colloid destabilisation. Photochemical reduction also effects solubility under low pH conditions with Fe(II) comprising 1% of the total iron in the Saharan Aerosol used and 8.4% in an Urban material at a pH of 2. This element shows rapid solution phase removal with increasing particulate load which is tentatively rationalised in terms of a simple Kd approach. 相似文献
146.
Barbara J. Cade-Menun Claudia R. Benitez-Nelson Perry Pellechia Adina Paytan 《Marine Chemistry》2005,97(3-4):293-306
Solution 31P nuclear magnetic resonance (NMR) spectroscopy has recently been used to characterize phosphorus species within marine particles. However, the effects of sample collection, storage and preparation have not been thoroughly examined. In this study, samples of settling particulates collected from a 1200-m sediment trap located in Monterey Bay, California, were subjected to various storage options (i.e., no storage, refrigeration, freezing, and oven-drying and grinding) prior to extraction for solution 31P-NMR spectroscopy. Freezing, refrigerating and drying samples for periods of up to 6 months prior to extraction with 0.25 M NaOH + 0.05 M Na2EDTA increased the concentration of extracted P by an average of 16% relative to samples extracted without storage. Pre-extraction storage also introduced some minor changes in P speciation, by increasing the percentage of orthophosphate by up to 15% and decreasing the percentage of pyrophosphate by up to 5%, relative to the abundances of these P species in samples extracted without storage. Drying caused the biggest changes in speciation, specifically decreasing more extensively the relative percentage of pyrophosphate compared to other treatments. Nevertheless, observed changes in speciation due to sample storage within a specific sample were small relative to differences observed among samples collected sequentially in the same area, or reported differences among samples collected at different locations. Samples were also analyzed by solid-state 31P-NMR spectroscopy before and after extraction, to examine extraction-related changes in P speciation. Comparison of solution with solid-state 31P NMR indicates that extraction with NaOH–EDTA removes the majority of organic esters, but only a variable portion of phosphonates (39–67%). In addition, there was preferential extraction of Ca-associated phosphate over Mg-, Fe- and Al-associated phosphate. Solution 31P NMR enables much higher resolution of P species within samples, particularly when it is important to speciate orthophosphate monoesters and diesters, or if polyphosphates are present. However, combining solid-state 31P NMR with solution 31P NMR spectroscopy for marine particles should be conducted when examining inorganic P speciation and the abundance of phosphonates. 相似文献
147.
148.
149.
研究了1990年6月和10月闽江口溶解态镉、铜、铅的行为及其与营养盐的关系。结果表明,在6月和10月镉呈添加行为,铜呈保守行为,而铅呈除去行为、镉的添加主要源自浮游生物碎屑的再矿化作用,而铅的去除受非生物无机过程控制。 相似文献
150.
对胶州湾水体、浮游生物、悬浮颗粒物和沉积物中锡的测定、形式、生物累积等进行研究。不同季节(1987年和1988年)的水体、浮游植物和沉积物测定表明:1.水体总还原无机锡和总锡含量分别为4.2~38.8ng/dm~3,65.6~209ng/dm~3;浮游植物总锡含量为22.4~414mg/kg(干重);沉积物总锡含量为0.015~0.98mg/kg(干重),且在胶州湾港口区测得水体总锡的最大值209ng/dm~3。以上结果与目前世界其它海域、河口类似。2.有些区域有机锡含量已达到或超过某些生物的致毒阈值(对双壳类,其TBT≤0.1μg/dm~3)从而引起水质恶化。3.水体总锡含量与悬浮颗粒量密切相关;浮游植物对锡的生物富集因子高达10~5,说明无机或有机颗粒及生物体在水体锡的循环迁移过程中起重要作用。 相似文献