A comparative study of mercury contamination in the Tagus estuary (Portugal) and major French estuaries (Gironde,Loire, Rhône)     

G. Figueres  J.M. Martin  M. Meybeck  P. Seyler 《Estuarine, Coastal and Shelf Science》1985,20(2):183-203

Concentrations of mercury were determined for the waters, suspended matter and sediments of the Tagus and of major French estuaries.The Tagus estuary is one of the most contaminated by mercury derived from the outfalls of a chloralkali plant and from other industrial sources. In deposited sediments the median level, 1·0 μg Hg g^?1, is twenty times higher than the natural background and Hg contents depend on the sediment grain-size, age and the distance from waste-outfalls. Suspended matter is more regularly and highly contaminated (median value: 4·5 μg Hg g^?1). In the French estuaries Hg levels in the suspended material decrease with salinity due to dilution and/or remobilization processes. In June 1982, in the Loire estuary, high values of Hg are observed in the middle estuary and attributed to urban and industrial sources.In the Tagus estuary, the general distribution of total dissolved Hg confirms the contamination: it increases seaward from 10 ng 1^?1 in the river to 80 ng 1^?1 in the estuary outlet. The dissolved Hg is almost totally organic in the river, inorganic in the middle estuary due to inorganic Hg effluents and again organic in the lower estuary. This variation is related to the dissolved organic carbon values. The dissolved Hg levels in the Loire Estuary (5–300 ng 1^?1) are much higher than in the Gironde estuary (3–6 ng 1^?1) and of the same order as those observed in the Tagus estuary.  相似文献   

Benthic nutrient regeneration in South Texas coastal waters     

R.Warren Flint  Daniel Kamykowski 《Estuarine, Coastal and Shelf Science》1984,18(2):221-230

Because of the variable, unpredictable nature of many potential nutrient sources for coastal phytoplankton primary production needs in the north-western Gulf of Mexico, benthic regeneration was investigated as a more constant source of nutrients to this ecosystem. Water column ammonia profiles taken at several locations on the south Texas inner-shelf in the last seven years showed peak concentrations in bottom waters. Benthic chamber measurements verified the presence of ammonia fluxes at the mud-water interface in south Texas coastal waters. These fluxes were related to benthic faunal activity as measured by sediment metabolism. Laboratory experiments, designed to test the effect of benthic faunal removal on nutrient regeneration, suggested that the fauna play a role in regulating this process. How this regulation may occur is discussed. It was estimated that annual benthic regeneration rates can supply 69% of the nitrogen required to support phytoplankton primary production in these coastal waters.  相似文献   

Retention of mercury in sediments of the Baltic Sea near Oulu,Finland     

Kimmo Tolonen  Erkki Alasaarela  Anita Liehu 《Journal of Paleolimnology》1988,1(2):133-140

Several cores were compared to elucidate the grade of mercury retention in sediments of the Baltic Sea near Oulu, Finland. The known history of the mercury discharge to waste water from a chlor-alkali plant, the primary pollution source, was compared to that in the sedimentary record. One core was dated by lead-210 and varve counts. During the past thirty years, the rate of sedimentation was up to 10 mm per year corresponding to a dry matter accumulation rate of about 3 kg m^–2a^–1. Under these conditions, most of the mercury reaching the sediment was retained. Correspondingly, the mercury levels in fish were considerably lower, with a delay of some five years.The present mercury content of the upper layers is some 1/4 or 1/5 that of the late 1970's, but it is still some twentyfold compared to levels at the beginning of the century. The extent to which the present mercury level in the sediment represents the various phases of industrial emission remains unsolved due to the origin of mercury in this sea area from several other sources and due to difficulties in exact core correlations from different years.  相似文献   

A portable extruding device for close interval sectioning of unconsolidated core samples   总被引：11，自引：0，他引：11  

John R. Glew 《Journal of Paleolimnology》1988,1(3):235-239

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小秦岭─桐柏山区地层构造岩浆岩对金矿控制特征及成矿模式     

彭万夫 《河南国土资源》1994,(3)

河南金矿主要分布在小秦岭地区，其次是桐柏山、崤山─熊耳山地区。含矿地层为前寒武纪的片麻岩－混合岩、片岩－变粒岩和轻微变质的绿片岩，原岩皆属中基性火山岩夹火山沉积岩；控矿构造以近东西向和北东向为主，与成矿关系密切的岩浆岩主要是燕山期花岗岩及有关脉岩。本文拟从地层、构造、岩浆岩控矿特点入手，通过金矿的成矿机制试图揭示小秦岭─桐柏山地区金矿成矿模式。  相似文献   

Holocene millennial/centennial‐scale multiproxy cyclicity in temperate eastern Australian estuary sediments     

C. Gregory Skilbeck  Timothy C. Rolph  Natalie Hill  Jonathan Woods  Roy H. Wilkens 《第四纪科学杂志》2005,20(4):327-347

We have undertaken a comparative study of down‐core variation in multiproxy palaeoclimate data (magnetic susceptibility, calcium carbonate content and total organic carbon) from two coastal water bodies (Myall and Tuggerah Lakes) in temperate eastern Australia to identify local, regional and global‐forcing factors within Holocene estuarine sediments. The two lakes lie within the same temperate climate zone adjacent to the Tasman Sea, but are not part of the same catchment and drain different geological provinces. One is essentially a freshwater coastal lake whereas the other is a brackish back‐barrier lagoon. Despite these differences, data from two sites in each of the two lakes have allowed us to investigate and compare cyclicity in otherwise uniform, single facies sediments within the frequency range of 200–2000 years, limited by the sedimentation rate within the lakes and our sample requirements. We have auto‐ and cross‐correlated strong periodicities at ～360 years, ～500–530 years, ～270–290 years, 420–450 years and ～210 years, and subordinate periods of ～650 years, 1200–1400 years and ～1800 years. Our thesis is that climate is the only regionally available mechanism available to control common millennial and centennial scale cyclicity in these sediments, given the geographical and other differences. However, regional climate may not be the dominant effect at any single time and either location. Within the range of frequency spectral peaks we have identified, several fall within known long‐term periodical fluctuations of sun spot activity; however, feedback loops associated with short‐term orbital variation, such as Dansgaard–Oeschger cycles, and the relationship between these and palaeo‐ENSO variation, are also possible contributors. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

甬江河床演变及航道治理   总被引：3，自引：0，他引：3  

沈承烈 《地理研究》1988,7(3):58-66

本文分析甬江动力、泥沙、边界及河床演变的基本特征,提出甬江航道整治的原则和措施。  相似文献   

Lateglacial and Holocene climate and soil erosion in southeastern France: A case study from Etang du Pourra,Provence     

H. Laval  J. Medus  C. Parron  J. P. Simonnet  P. Trement 《第四纪科学杂志》1992,7(3):235-245

A synthesis of pollen evidence from Etang du Pourra, a small pond in Rhodanian Provence, France, complemented by new sedimentological, mineralogical and palynological data allow a reassessment of the Lateglacial-Holocene vegetation and climatic history of the area. The Etang du Pourra succession is shown to consist of two parts; the lower part dates from the Lateglacial and the upper reveals the Holocene pollen-stratigraphic succession typical of the region. In the Lateglacial, a humid and cooler phase is recorded before the Younger Dryas conditions progressively set in. In the Holocene succession, the consequences of human modifications on the environment are clearly visible in changes in mineralogy and pollen stratigraphy.  相似文献   

Tidal phase control of sediment discharge from the Yangtze River     

John D. Milliman  Ya Hsueh  Dun-Xin Hu  David J. Pashinski  Huan-ting Shen  Zuo-sheng Yang  Peter Hacker 《Estuarine, Coastal and Shelf Science》1984,19(1):119-128

Tidal phase plays a major role in controlling sediment discharge from the Yangtze River estuary in eastern China. Direct measurements indicate that during spring tide in mid-November 1981 approximately 3 times the sediment passed down the main channel of the river as during the next neap tide, 3 days later. The estuary presumably acts as a conduit for riverine sediment during spring tide but as a sink during neap tide. Tidal phase control of sediment discharge appears to be primarily dependent upon tidal range relative to estuarine depth rather than river discharge or absolute tidal range per se.  相似文献   

抚松大营铅锌矿床同位素地质特征及矿床成因     

于长霞 《吉林地质》1990,(3)

本文主要通过对抚松大营铅锌矿床同位素特征的研究,讨论了成矿物质来源、成矿流体性质、岩浆活动对成矿作用的影响,从而证明矿床成因属沉积—热液叠加型层控矿床。  相似文献