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1.
The results of studies aimed to assess the information significance of the coefficients of bottom accumulation of hydrophobic organic substances and heavy metals as indicators of pollution of freshwater bodies are presented. It is shown that the same value of the coefficient of bottom accumulation may correspond to different situations in water bodies. Methods for the interpretation of data on the state of water bodies based on the coefficient of bottom accumulation and its components are proposed to reliably determine the level and character of pollution. Chronic pollution of a number of freshwater bodies of the Russian Federation is assessed by data on the accumulation of pesticides, oil products, polycyclic aromatic hydrocarbons, and heavy metals in bottom deposits. 相似文献
2.
Variations in the Hydrological Regime of Kara-Bogaz-Gol Gulf,Lake Issyk-Kul,and the Aral Sea Assessed Based on Data of Bottom Sediment Studies 总被引：1，自引：0，他引：1
Ferronskii V. I. Polyakov V. A. Brezgunov V. S. Vlasova L. S. Karpychev Yu. A. Bobkov A. F. Romaniovskii V. V. Johnson T. Ricketts D. Rasmussen K. 《Water Resources》2003,30(3):252-259
The isotopic and material composition of bottom deposits, examined in the Kara-Bogaz-Gol Gulf, Lake Issyk-Kul, and the Aral Sea, is considered. The obtained data are used to characterize variations in the regime of the water bodies in the Holocene. 相似文献
3.
Iron migration forms and variations of its concentrations in water and bottom sediments of the Vygozero Reservoir were studied in period from 1993 to 2014. The decrease in wastewater volume discharged from the pulp and paper mill in the early 1990s caused stabilization of water oxidation regime and accumulation of iron in bottom sediments, from which it returns into the water mass when the environmental conditions change in the seasonal oxygen cycle. 相似文献
4.
The results of studies of the hydrological and hydrochemical regimes carried out in 2001 in Chayvo Bay and microbiological analyses of the abundance of geterotrophic microorganisms belonging to ecological-trophic groups are given. Data on the concentrations of petroleum hydrocarbons, phenols, and metals (Fe, Pb, and Cd) in water and bottom sediments were collected. The obtained data were used to assess the water quality in the bay. 相似文献
5.
6.
Sediment diffusive fluxes of Fe,Mn, and P in a eutrophic lake: Contribution from lateral vs bottom sediments 总被引：3，自引：0，他引：3
Nelson Belzile Jaime Pizarro Montserrat Filella Jacques Buffle 《Aquatic Sciences - Research Across Boundaries》1996,58(4):327-354
Water column data and porewater profiles are used to study the chemical evolution with time and with depth of a eutrophic lake. By using different approaches, diffusion fluxes for dissolved iron, manganese and phosphate are calculated and used to describe the processes occurring at the sediment-water interface as well as in the hypolimnion of the lake. These data are used in the elaboration of a qualitative model to describe the chemical behaviour of the sedimentary interface of an anoxic lake with emphasis on the Fe/P/S system. Acorona model is proposed to explain the evolution with time of the diffusion process by estimating the relative contribution of bottom and lateral sediment surfaces to the total fluxes of dissolved elements diffusing from the sediment to the overlying water. As the hypolimnion becomes more anoxic, it has been observed that lateral sediment surfaces (16 to 10 meters in depth) represents a larger supplier of diffusing dissolved components than the bottom sediment portion (bottom to 18 meters). 相似文献
7.
Peter Petrusevics John Bye John Luick Carlos E.P. Teixeira 《Continental Shelf Research》2011,31(7-8):849-856
Historical and recent oceanographic cruise data, MODIS chlorophyll-a satellite data, and an analytical model are used to examine SST fronts in the entrance to Spencer Gulf, South Australia. The fronts (2–3 °C) due to the contrast between warm Spencer Gulf waters and cooler waters of the continental shelf are readily observable on satellite imagery. Three water masses: cool, fresh upwelled shelf water; warm, salty Great Australian Bight water; and very warm and salty Spencer Gulf bottom water occupy the area. In consequence a summer density minimum is formed at the entrance to Spencer Gulf. The analytical model predicts that this thermohaline structure sets up an ageostrophic circulation, which favours upwelling in the central portion of the entrance. This is confirmed by the satellite data which show an increased chlorophyll-a concentration in the vicinity of the upwelling. 相似文献
8.
The results of first application of automated bottom station for studying chemical exchange across the water-bed interface
(IO RAS lander) were obtained for the case of sediments in the northwestern Black Sea near Gelendzhik (Golubaya Bay). The
lander is equipped with bottom chambers, sensors of environmental characteristics, and samplers, allowing fluxes of chemical
elements through the water-bed interface to be determined directly. Bottom sediments were represented by organogenous silts
containing hydrogen sulfide. The high activity of diagenetic processes resulted in a higher consumption of O2 by sediments (the flux from the bottom water was 130 mM/(m2/day), high fluxes of biogenic elements (P, Si,) and metals (Mn, Fe). At the same time, fluxes across the water-bed interface
were evaluated based on the difference between concentrations of these elements in the near-bed and silt water (Fick’s law).
The obtained data demonstrate the priority of direct measurements of fluxes (lander) over the calculation method. The first
application of the lander suggests the need for methodological improvements both of engineering character and in chemical-analytical
support. 相似文献
9.
Chau KW 《Marine pollution bulletin》2005,51(8-12):1078-1084
The eutrophication phenomenon often leads to undesirable water quality. This paper delineates an unsteady three-dimensional finite difference numerical model for eutrophication dynamics in the coastal waters of Tolo harbour, Hong Kong, employing the numerically generated, boundary-fitted, orthogonal curvilinear grid system as well as a grid “block” technique. It models the transport and interaction of nine water quality constituents. Adjustments of values of some kinetic coefficients in the model are effected through calibration with field data. It is demonstrated that the model can reasonably reproduce the interactions amongst all the water quality constituents, the eutrophication processes and, in particular, the featured bottom water anoxic condition during the summer in Tolo harbour. 相似文献
10.
Coastal embayments located downwind of large rivers under an upwelling-favorable wind are prone to develop low-oxygen or hypoxic conditions in their bottom water. One such embayment is Mirs Bay, off the Guangdong coast, which is affected by upwelling and the Pearl River Estuary (PRE) plume during summer. The relative importance of physical and biochemical processes on the interannual variability of hypoxia in Mirs Bay and its adjacent waters was investigated using statistical analyses of monthly hydrographic and water quality monitoring data from 2001 to 2015. The results reveal that the southwesterly wind duration and the PRE river discharge together explain 49% of the interannual variability in the size of the hypoxic area, whereas inclusion of the nutrient concentrations inside Mirs Bay and phytoplankton on the shelf explains 75% of the interannual variability in the size of the hypoxic area. This finding suggests that the interannual variability of hypoxia in Mirs Bay is regulated by coupled physical and biochemical processes. Increase of the hypoxic area under a longer-lasting southwesterly wind is caused by increased stratification, extended bottom water residence time, and onshore transport of a low-oxygen water mass induced by stable upwelling. In contrast, a reduction in the size of the hypoxic area may be attributed to a decrease in the surface water residence time of the particulate organic matter outside Mirs Bay due to increased discharge from the PRE. The results also show that the effects of allochthonous particulate organic matter outside Mirs Bay on bottom hypoxia cannot be neglected. 相似文献
11.
Western Port, Victoria, Australia is a tide-dominated embayment with an unusual and complex shape. Bottom currents and circulation and their effects on sediment processes were examined using instrumented tripods to measure currents, tides and wave activity, and to estimate sediment transport at nine locations in the bay. Overall bottom water movement patterns were determined by use of seabed drifters. The characteristics of the bay reflect a small catchment and low freshwater and sediment input. A complex system of channels is flanked by extensive intertidal areas. Tidal range varies up to more than 3 m, generating bottom currents up to 70cm s?1. Flow directions generally conform to channel alignments but major deviations are important. Net circulation in the bay is clockwise around the large central island. The ratio of tidal range to half-tidal period (ΔH/ΔT) when compared with measured currents gave a method of prediction of the annual frequency distribution of maximum bottom current velocities. Determination of threshold current velocities enabled prediction of annual frequency of bedload movement (generally 50–100 per cent of tide cycles). Bedload mass transport for all observed tide cycles was calculated, and estimates of annual mass transport capacity (between 102 and 106 g cm?1 a?1( were obtained from a relationship between predicted tidal conditions and mass transport. Seabed drifters delineated the major bottom water movements in the bay and adjacent Bass Strait, and also detailed circulation patterns. This linked the data from the tripod stations, in particular patterns of ebb- and flood-dominance. A coherent picture of the processes operating in Western Port is presented by integrating these studies with corroborative studies of sediment distribution and morphology, hydrochemistry, and mathematical modelling. Some morphological characteristics related to tide-dominance are discussed. 相似文献
12.
A longitudinal seismic reflection profile along the east flank of Reykjanes Ridge, from Charlie fracture zone to the vicinity of Iceland, has important implications both for bottom water movement and for hypotheses of crustal generation at the axis of the mid-oceanic ridge. In this paper bottom water movement is considered. Between 52°N and 57°N Reykjanes Ridge is cut by about 12 fractures whose trend, inferred from other data, is approximately east-west. North of 57° there is little or no indication of east-west fracturing. Fracture valley bottoms are typically 1 km below the surrounding basement level; sediment fills are about 0.5 km; present bottoms are 2.1 to 2.8 km below sea level. Depositional asymmetry is apparent in 9 cases, 7 of which have the deepest and generally least reflective bottom at the northern edge. This suggests predominately west-flowing bottom currents, carrying Norwegian Sea overflow water through the fracture valleys, a result consistent with previously published data. 相似文献
13.
《Continental Shelf Research》2006,26(17-18):2319-2334
Instrumented bottom tripods have provided important data on sediment transport processes on continental shelves and in estuaries for four decades. Since the initial deployment in a tidal channel in Puget Sound, WA, in 1965 numerous tripods have been constructed to investigate bottom boundary layer and sediment dynamics worldwide. Tripod data have led to new understanding of near-bottom wave and current flows in the coastal ocean, and have been crucial to the development of shelf circulation and sediment transport models. Calculations of bottom stress, bottom roughness, and sediment flux that resulted directly from tripod data have been compared to bottom boundary layer model results. Where these have differed, new or revised model components have been developed to improve the skill of the models. The many discoveries that have been made from tripod experiments include dense, near-bottom fluid mud layers that transport large quantities of suspended sediment offshore into deeper regions of the continental shelf. This process has been linked to the seaward progradation of subaqueous deltas and to the boundaries of mid-shelf mud deposits off rivers with high fine-sediment discharge. 相似文献
14.
甲烷(CH4)是一种重要的温室气体,对全球气候变化有不可忽视的影响.三峡水库是中国最大的水库,其潜在的CH4释放近年来备受关注.然而,此地区现存研究主要集中于水气界面通量观测,对库底沉积物同底层水体CH4浓度变化之间关系的认知仍然欠缺.为探究三峡水库泥沙主要沉降淤积的中段区域库底水体CH4浓度变化及其主要影响因素,本研究于2017年8月2018年11月在涪陵南沱镇、忠县石宝寨、万州小周镇采集库底上覆水体和底泥样本,并结合三峡水库调度运行特征进行分析.结果表明,三峡水库中段库底上覆水CH4浓度范围为0.02~0.91μmol/L,二氧化碳(CO 2)浓度范围为0.006~0.105 mmol/L,沉积物有机碳含量范围为7~90 g/kg,总氮含量范围为0.27~45.6 g/kg.另外,三峡水库低水位运行时期(59月),上游及陆源输入大量异源性有机碳是该时期三峡库中段底部CH4积累的充分条件.在水库高水位运行时期(10月次年4月),水位与径流变化对三峡水库中段底部CH4的影响并不明显,库底自源性有机质相对比重有所增加,温度是该时期影响水库底层水体CH4浓度分布的主要水环境因素. 相似文献
15.
Anatoliy Filonov 《Ocean Dynamics》2011,61(7):917-931
The dynamics of a semidiurnal internal tidal wave at a narrow Mexican Pacific shelf is discussed using the data of temperature
obtained by an anchored instrument and data of field surveys. The internal tide on the shelf is dominated by an inclined wave,
which propagates upward and onshore along a continental slope. Despite its reflection from the bottom and from the surface
of the ocean, they remain inclined and totally destroyed over the course of one wavelength. Due to wave reflection from the
inclined bottom, the horizontal and vertical wave number increase threefold when the wave goes into shallow waters. The wave
undergoes nonlinear transformation and overturns forming several homogeneous temperature layers up to 20 m thick. The most
intense disturbances of water layers are observed near the bottom, where the slope angle approaches its critical value. Because
of nonlinear effects, the wave carries cool deep water out to the shallow depth and causes coastal upwelling. Intense solar
warming together with vertical mixing results in a rapid rise of temperature in the 130-m water column that was observed. 相似文献
16.
Emmanuel Spadavecchia Vincenzo Lipari Nicola Bienati Giuseppe Drufuca 《Geophysical Prospecting》2013,61(4):725-734
Despite being less general than 3D surface‐related multiple elimination (3D‐SRME), multiple prediction based on wavefield extrapolation can still be of interest, because it is less CPU and I/O demanding than 3D‐SRME and moreover it does not require any prior data regularization. Here we propose a fast implementation of water‐bottom multiple prediction that uses the Kirchhoff formulation of wavefield extrapolation. With wavefield extrapolation multiple prediction is usually obtained through the cascade of two extrapolation steps. Actually by applying the Fermat’s principle (i.e., minimum reflection traveltime) we show that the cascade of two operators can be replaced by a single approximated extrapolation step. The approximation holds as long as the water bottom is not too complex. Indeed the proposed approach has proved to work well on synthetic and field data when the water bottom is such that wavefront triplications are negligible, as happens in many practical situations. 相似文献
17.
226Ra profiles have been measured in the western Indian Ocean as part of the 1977–1978 Indian Ocean GEOSECS program. These profiles show a general increase in deep and bottom water Ra concentration from the Circumpolar region to the Arabian Sea. A deep Ra maximum which originates in the Arabian Sea and in the Somali basin at about 3000 m depth spreads southward into the Mascarene basin and remains discernible in the Madagascar and Crozet basins. In the western Indian Ocean, the cold Antarctic Bottom Water spreads northward under the possibly southward-flowing deep water, forming a clear benthic front along the Crozet basin across the Southwest Indian Ridge into the Madagascar and Mascarene basins. The Antarctic Bottom Water continues to spread farther north to the Somali basin through the Amirante Passage at 10°S as a western boundary current. The benthic front and other characteristic features in the western Indian Ocean are quite similar to those observed in the western Pacific where the benthic front as a distinctive feature was first described by Craig et al. [15]. Across the Mid-Indian Ridge toward the Ceylon abyssal plain near the triple junction, Ra profiles display a layered structure, reflecting the topographic effect of the mid-ocean ridge system on the mixing and circulation of the deep and bottom waters. Both Ra and Si show a deep maximum north of the Madagascar basin. Linear relationships between these two elements are observed in the deep and bottom water with slopes increasing northward. This suggests a preferential input of Ra over Si from the bottom sediments of the Arabian Sea and also from the flank sediments of the Somali basin. 相似文献
18.
Lake Umbozero (the second largest in the area and the deepest in Murmansk province) was studied with the aim to establish
the biogeochemical features of the distribution of chalcophile elements (Hg, Cd, Pb, As) in water, bottom sediments, and whitefish
organs and tissues. Lake Umbozero is subject to the effect of emissions and effluents of mining-and-metallurgical plants in
Murmansk province, as well as airborne anthropogenic pollution of global character. Surface and near-bed peaks were recorded
in the distribution of Pb and Cd in water mass. Those peaks can be due to phytoplankton development in surface layers and
the precipitation of dead organisms and mechanical suspension into bed layers. The mean Pb and Cd concentrations in Umbozero
water mass exceed the mean for lake water in taiga zone. Water body pollution manifests itself in an increase in concentrations
of elements, such as heavy metals, in the surface layers of bottom sediments. The largest contamination factors were recorded
for Cd and Pb. Lake pollution by highly toxic chalcophile elements also caused their accumulation in whitefish organs and
tissues: the biological accumulation coefficient is >1 for Cd in kidneys (5.8) and for Hg in kidneys, liver, and muscles (3.6,
3.3, and 2.2, respectively). 相似文献
19.
Hailemariam Meaza Amaury Frankl Jean Poesen Amanuel Zenebe Veerle Van Eetvelde Biadgilgn Demissie 《水文科学杂志》2018,63(6):957-977
Marginal grabens are major development corridors in Ethiopia, and need to be understood for proper assessment of the hydrological budget. This study investigates the water balance of the Aba’ala graben (553 km2) in the period 2015–2016 under the challenge of data scarcity. We measured the rainfall and river discharge in order to analyse the runoff components of the graben. The rainfall volume in the Aba’ala graben showed erratic behaviour, which led to rapid flood runoff of the major river into the graben bottom. The average annual inflow and outflow of the graben bottom for the period 2015–2016 amounted to 364 and 254 hm3, respectively. However, flood runoff and evapotranspiration had a marked effect on water availability. Water storage took 36% of the water inflow into the graben bottom. Sustainable water management could reduce the temporal variation of the water storage in Aba’ala graben. 相似文献
20.
The state of the water area in the Bays of Koz’mina and Lake Vtoroe (Nakhodka Gulf is evaluated. The data given include water
temperature and salinity, biochemical oxygen demand, pH, alkalinity, chlorophyll a, organic matter, biogenic elements, oil
products, detergents, polycyclic aromatic hydrocarbons, phenols, and organochlorine pesticides in water and bottom sediments.
Pollutants may enter the system of bights from both onshore sources and the open part of the bay. The water and bottom sediments
in this part of the bay show higher values of BOD5 and the concentrations of oil products, polycyclic aromatic hydrocarbons,
phenols, and organochlorine pesticides. The anthropogenic load on the water body is shown to increase because of the new industrial
construction on its shore. 相似文献