共查询到20条相似文献,搜索用时 15 毫秒
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Robert A. Berner 《Earth and Planetary Science Letters》1973,18(1):77-86
Chemical data presented in this paper indicate a good correlation between P2O5 and Fe2O3 in some iron-rich volcanogenic sediments from the East Pacific Rise. In addition, adsorption experiments and chemical analyses of deuterically altered and unaltered samples of submarine basalts strongly suggest that this association is due to the reaction of phosphate in sea water with poorly crystallized hydrous ferric oxides. East Pacific Rise sediments adsorb far greater amounts of phosphate from sea water than either carbonate or non-carbonate sediments from other areas of the ocean. From geochemical flux calculations it is concluded that an appreciable proportion of dissolved phosphate delivered to the oceans by rivers is removed by ridge crest volcanogenic iron oxides either as absorbed surface coatings or as discrete, but highly disordered, ferric phosphate phases. This process should be taken into consideration when considering oceanic phosphate budgets, both in the present and past oceans. 相似文献
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Vulnerability indicators of sea water intrusion 总被引:5,自引:0,他引:5
In this paper, simple indicators of the propensity for sea water intrusion (SWI) to occur (referred to as "SWI vulnerability indicators") are devised. The analysis is based on an existing analytical solution for the steady-state position of a sharp fresh water-salt water interface. Interface characteristics, that is, the wedge toe location and sea water volume, are used in quantifying SWI in both confined and unconfined aquifers. Rates-of-change (partial derivatives of the analytical solution) in the wedge toe or sea water volume are used to quantify the aquifer vulnerability to various stress situations, including (1) sea-level rise; (2) change in recharge (e.g., due to climate change); and (3) change in seaward discharge. A selection of coastal aquifer cases is used to apply the SWI vulnerability indicators, and the proposed methodology produces interpretations of SWI vulnerability that are broadly consistent with more comprehensive investigations. Several inferences regarding SWI vulnerability arise from the analysis, including: (1) sea-level rise impacts are more extensive in aquifers with head-controlled rather than flux-controlled inland boundaries, whereas the opposite is true for recharge change impacts; (2) sea-level rise does not induce SWI in constant-discharge confined aquifers; (3) SWI vulnerability varies depending on the causal factor, and therefore vulnerability composites are needed that differentiate vulnerability to such threats as sea-level rise, climate change, and changes in seaward groundwater discharge. We contend that the approach is an improvement over existing methods for characterizing SWI vulnerability, because the method has theoretical underpinnings and yet calculations are simple, although the coastal aquifer conceptualization is highly idealized. 相似文献
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As vegetation usually excludes salt during water uptake, transpiration will increase the salinity of the residual water. If the source water is sea water, then the residual water may become highly saline. In the unconfined coastal aquifer of the tropical Burdekin River delta, northeastern Australia, areas of highly saline ground water with chloride concentrations up to almost three times that of sea water occur up to 15 km from the present coastline, and are attributed to transpiration by mangrove vegetation during periods of high sea level. Radiogenic ((14)C) carbon isotope analyses indicate that ground water with chloride concentrations between 15,000 and 35,000 mg/L is mostly between 4000 and 6000 years old, at which time sea level was 2 to 3 m higher than present. Stable isotope analyses of oxygen-18 and deuterium show no evidence for evaporative enrichment of this water. Oxygen-18, deuterium, and stable (delta(13)C) carbon isotope analyses of ground water and soil water point to a recharge environment beneath the mangrove forests during this postglacial sea level high stand. During that period, transpiration of the mangrove forests would have led to high chloride concentrations in the residual ground water, without inducing isotopic fractionation. Due to the higher density, this hypersaline water moved downward through the aquifer by gravity and has formed lenses of highly saline ground water at the bottom of the unconfined aquifer. 相似文献
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Marine sediments are the ultimate recipient of mercury introduced into aquatic ecosystem either by man or by weathering. In the surficial sediments of the northern Tyrrhenian sea high concentrations of this metal were found in an area close to the effluent of a chlor-alkali plant and in the bays of La Spezia and Leghorn, which receive wastes from numerous industries and from port activities.The sediments of a much larger marine area off the mouths of the Ombrone, Albegna and Fiora rivers also contain high levels of Hg, part of which derives from the weathering of the rich cinnabar deposits of Mount Amiata and part from mining and processing the cinnabar. 相似文献
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In a laboratory experiment to simulate mine tailings disposal into a coastal inlet of British Columbia, initial rapid increases in dissolved iron, copper and lead were observed in the first three hours with subsequent slow decreases to background values within one month. Manganese and nickel increased slowly during the experiment while cadmium and zinc did not increase. 相似文献
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A two-dimensional finite element model for density dependent groundwater flow was calibrated to simulate sea water intrusion in Nauru Island in the Central Pacific Ocean. Nauru Island occupies an area of 22 km2 and supports a population of 8500. The island has been mined for its phosphate deposits and current reserves indicate that the mine has about eight years life remaining. The water supply of the island is about one third dependent on imported water which is also used as ballast on the phosphate ships. Imported water will not be available in the future, and a hydrogeological investigation shows that the island is underlain by a fresh water layer, less than 5 m thick. The freshwater layer overlies a thick transition zone of brackish water which in turn overlies sea water. Simulation of several management options shows that it is possible to substitute current importation of fresh water by careful extraction from the groundwater resources of the island. 相似文献
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Salsvatn,a lake with old sea water 总被引:1,自引:0,他引:1
Dr. Anders Bøyum 《Aquatic Sciences - Research Across Boundaries》1973,35(2):262-277
Salsvatn is a 464 m deep lake laying 16 m above sea level in North Trøndelag, Norway. The lake was isolated from the sea some 3,000 years ago. It is assumed that salt-water in the deepest 50 m of the lake is the remain of sea water being trapped in the lake at this time. The concentration of cloride in the salt-water layer corresponds to a salinity of 29‰ in ordinary sea water. Hydrography of the lake and changes in some components of the salt water compared with ordinary sea water are discussed. Comparison is made with changes in the stagnant layers of the Black Sea and Lake Rørholtjorden. The latest is another lake with old sea-water at its bottom. Surface sediment samples have been collected from the freshwater and salt-water layers in Lake Rørholtfjorden and from the salt-water layer of Lake Salsvatn. Some chemical components of the sediments and interstitial water have been analysed and discussed. 相似文献
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《Acta Geochimica》2021,(1)
To understand its source,distribution,storage,and translocation in the subtropical forest ecosystems,mercury(Hg) concentrations and stable isotopes in forest biomass tissues(foliage,branch,bark,and trunk) were investigated at Ailao Mountain National Nature Reserve,Southwest China.The total Hg(THg) concentrations in the samples show the following trend:mature foliage(57 ± 19 ng g~(-1)) bark(11 ± 4.0 ng g~(-1)) branch(5.4 ± 2.5 ng g~(-1)) trunk(1.6 ± 0.7 ng g~(-1)).Using the measured THg concentrations and the quantity of respective biomasses,the Hg pools in the forest are:wood(60 ± 26 μg m~(-2)) bark(51 ± 18 μg m~(-2)) foliage(41 ± 11 μg m~(-2)) branch(26 ± 8.3 μg m~(-2)).The tree biomasses displayed negative δ~(202)Hg(-1.83‰ to-3.84‰) and Δ~(199)Hg(-0.18‰ to-0.62‰).The observed Δ~(200)Hg(-0.08‰ to 0.04‰) is not significantly from zero.A Δ~(199)Hg/Δ~(201)Hg ratio of 1.05 was found in tree biomasses,suggesting that mercury has undergone Hg~((Ⅱ)) photoreduction processes.A Hg-isotope based binary mixing model suggests that Hg in the tree biomasses mainly originated from foliage uptake of atmospheric Hg~0,constituting 67%,80%,and 77% of Hg in wood,branch,and bark,respectively.Our study sheds new light on the transportation and sources of Hg in the subtropical forest ecosystems. 相似文献
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《地震地磁观测与研究》2015,(5)
通过对下关温泉水样汞含量异常进行调查、核实与判定,探讨异常核实、判定方法及步骤,分析引起地下水汞含量异常变化的干扰因素,对水汞观测和汞含量异常应用于地震预测研究工作具有参考价值。 相似文献
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Impact of coastal land reclamation on ground water level and the sea water interface 总被引:6,自引:0,他引:6
Land reclamation in coastal areas may have a significant effect on local ground water systems. Steady-state analytic solutions based on Dupuit and Ghyben-Herzberg assumptions are derived to evaluate this effect. Two situations are considered, both with ground water flow resulting from precipitation recharge: the coastal aquifer of an extensive landmass and an island. The results show that after reclamation, the water table rises and the salt water-fresh water interface moves seaward. The degree of these changes depends on the extent of reclamation and the hydraulic conductivity of the fill material. For the island situation, the reclamation displaces the ground water divide and changes the ground water conditions in the entire island. An unintended advantage of the reclamation is an increase of fresh ground water resource because the reclaimed land can be an additional aquifer and rain recharge takes place over a larger area. 相似文献
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The El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) are two important climate oscillations that affect hydrological processes at global and regional scales. However, few studies have attempted to identify their single and combined influences on water discharge variability at multiple timescales. In this study, we examine temporal variation in water discharge from the Yangtze River into the sea and explore the influence of the ENSO and the PDO on multiscale variations in water discharge over the last century. The results of the wavelet transform analysis of the water discharge series show significant periodic variations at the interannual timescale of 2 to 8 years and the decadal timescale of 15 to 17 years. Water discharge tended to be higher during the La Niña–PDO cold phase and lower during the El Niño–PDO warm phase. The results of the cross wavelet spectrum and wavelet coherence analyses confirm the relationship between the interannual (i.e., 2 to 8 years) and decadal (i.e., 15 to 17 years) periodicities in water discharge with the ENSO and the PDO, respectively. As an important large‐scale climate background, the PDO can modulate the influence of the ENSO on water discharge variability. In general, the warm PDO enhances the influence of El Niño events, and the cold PDO enhances the influence of La Niña events. Our study is helpful in understanding the influencing mechanism of climate change on hydrological processes and provides an important scientific guideline for water resource prediction and management. 相似文献