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1.
Estuarine systems adjacent to urban areas are at risk of contamination by contaminants from anthropogenic sources, such as heavy metals. We anticipated that the sediments of the Swan River estuary, which runs through metropolitan Perth in Western Australia, would show metal contamination related to industrialization and inputs of stormwater. Total Cu, Pb and Cd concentrations, and Cu, Pb, Cr and Zn inoperationally-defined fractions, were determined inseparate sampling exercises in near-shore sediments ofthe upper Swan River estuary.Total metal concentrations in sediments were not high (maximum values of 297 mg kg-1 for Cu, 184 mg kg-1 for Pb and 0.9 mg kg-1 for Cd) when compared with Australian environmental assessmentguidelines for soils. On the basis of linear regressions between sediment metal concentrations andphysicochemical properties of the sediments (pH, organic carbon, particle size distribution), no single parameter could explain the variation in metal concentrations for all metals. Sediment organic carbon content was positively correlated with Cu concentration; Cu concentrations also increased significantly with increasing clay content anddecreasing sand content. Pb concentrations showed a significant increase with increasing sediment pH, and were approximately three-fold higher in sediments adjacent to stormwater drain outfalls than in sediments remote from drains; no such effect was observed for Cu or Cd. No effect of distance downstream was observed. Sequential extraction of sediments showed that most of the metals were in relatively immobile forms, for example bound to Feoxides, or only extractable by aqua regia. The enhanced concentrations of Pb near stormwater outfalls suggest that vehicle-derived Pb may be an important contributor of Pb to the estuary.  相似文献   

2.
Heavy metal transport in Cauvery river chiefly takes place in the particulate form. Tributaries Hemevathi and Kabini draining highly mineralized areas contribute significantly to the heavy metal load of the Cauvery river. Particulate metal transport is influenced by the presence of major dams built across the river. Factor analysis of the elemental data identifies two major group of heavy metals, (a) Fe, Mn, Cr, V and Ti and (b) Cu, Pb and Zn in the suspended sediments of Cauvery river. Heavy metals in surface sediments show wide variations in their concentrations due to the non-uniform grain size distribution of the sediments. The elements Fe, Mn, Pb, Cu, Zn, Ni, Co and As are dominantly present in the <20 μm fraction of the river sediments. Speciation studies show that Fe-Mn oxide phase held the largest share of heavy metals in the sediments. The depth variation of heavy metals in the core sediments suggest their similar mobility during diagenesis. Geoaccumulation indices calculated suggest that Cd, Zn, Cr, Pb, Cu and Ni are enriched in sediments several times over background values.  相似文献   

3.
Background, aim, and scope  Elevated levels of heavy metals in the aquatic and soil systems can be caused by the weathering of mineralized rocks. This enrichment is often considerably enlarged by historical and current mining and smelting activities. In Poland, the most contaminated river systems are those in the Silesia region. The metalliferous ore mining and smelting industries have been the main sources of heavy metal pollutions over the last 100–170 years. The previous and present studies have shown very high concentrations of heavy metals in the bottom sediments of the Mala Panew River, the most polluted tributary of the Oder River. The main objective of this work was to study temporary changes of selected metal (Zn, Pb, and Cd) concentrations in upper layer of bottom sediments at the measuring point near the outlet of the Mala Panew River into the Oder River, and to determine the vertical distribution of the metals in the sediment cores from the most polluted middle part of this river. The mobility of the metals and their potential bioavailability were assessed based on metal partitioning in the sediments and metal concentrations in pore waters. The presented data were compared with metal concentrations in aquatic sediments from similar historical mining and smelting sites in Poland and other countries. Methods  The upper layer of bottom sediment samples from the same Mala Panew River measuring point were collected six times in the period 1997–2005, while five sediment cores were collected once from the middle course of Mala Panew River in 2006. Abiotic parameters such as pH and Eh have been determined in situ. Metal contents were determined in the <20 and <63 μm size fractions of sediments after digestion in a microwave oven with aqua regia or concentrated nitric acid. Metal mobility was assessed in the selected sediment cores by the chemical forms of metals (sequential extraction method) and their concentrations in pore waters were investigated. Results  The concentrations of Cd, Pb, and Zn in the upper layer of sediments varied, depending on both the season and the year of sampling. Their mean concentrations (from six samplings) are [mg/kg]: Zn 1,846, Pb 229 and Cd 73. The metal concentrations in the sediment cores varied with the depth in the range of [mg/kg]: 0.18–559 for Cd, 26.2–3,309 for Pb and 126–11,153 for Zn, although the highest accumulations generally could be observed in the deeper layers. The most mobile metal fractions, i.e., exchangeable, carbonate and easily reducible fractions, are typical of Zn and Cd. Cadmium was found to be the most mobile metal and its relative contribution ranges from 84 to 96%, while in the case of Zn it ranged from 45 to 94%. Lead is mainly associated with the moderately reducible fraction (30–60%). Relative contributions of metal chemical forms slightly vary with the depth in the sediment profile. The results obtained for the pore water samples show very high concentrations of the metals studied, especially in the case of Cd (31–960 μg/dm3) and Zn (300–4,400 μg/dm3). Discussion  Accumulation of Cd, Pb, and Zn in the upper layer of the bottom sediments and in the sediment core samples from the Mala Panew River is very high, considerably exceeding the local geochemical background. High contributions of mobile Cd and Zn and the toxicity of cadmium can cause environmental risk. Our measurements also suggest that mobile metals can migrate into groundwater, whereas the groundwater itself can leach some chemicals from river sediments, because of a relatively high water table in the study area, especially during rainfall periods. Comparison of the results obtained with the literature data from the last decade shows that the concentrations of Cd and Zn in the sediments from the Mala Panew River are the highest among other submersed sediments in Poland and other regions (e.g., the Mulde River, Germany). Conclusions  The Mala Panew River is one of the most polluted rivers when compared with similar historical mining and smelting areas in Poland and elsewhere. The sediments studied are strongly polluted with the metals analyzed. In the upper layer of the bottom sediments there has been no reduction of Zn and Cd amounts over the last decade, which could suggests a long-term migration and a secondary contamination. Considerably higher accumulations of metals in overbank sediment cores and in the deeper core section could result from strong contamination in previous decades and translocation of Cd and Zn (secondary pollutants). The relatively high concentrations of the two metals in pore waters support these findings. Cadmium is crucial in the environmental risk assessment because of its high mobility and toxicity. These data are important for water/sediment management in the transboundary Oder River catchment, situated in Poland, Germany and the Czech Republic. Recommendations and perspectives  It is important to assess mobility phase and pore water in the contaminated historical aquatic sediments. Such studies may help explain the changes, which take place in the sediment layers as well as at the water–sediment interface. Obtained results should be used for the risk assessment of the historical contaminated sediments at the local river-basin scale. The treatment of contaminated sediments, e.g., dragging activity, should be considered as very important in management strategies in order to avoid remobilization of metals.  相似文献   

4.
The Schelde estuary is heavily polluted with many different (micro)pollutants. This results in high concentrations in the abiotic and biotic compartments of the Schelde estuary and in various effects. the present day suboxic and anoxic conditions in the upper estuary are probably responsible for the high distribution coefficients for some trace metals in the lower Schelde estuary (Western Schelde). a future reduction in discharges with a high biological oxygen demand will therefore not only result in higher oxygen concentrations, but probably also in lower distribution coefficients for trace metals in the Western Schelde. Simulations show that lower trace metal distribution coefficients will probably result in higher concentrations of dissolved (bioavailable) trace metals, even with substantially reduced discharge rates, due to the desorption of trace metals from resuspended bottom sediments.  相似文献   

5.
The behaviour of Co, Fe, Mn, and Ni was investigated in the mixing area of the Po river in six surveys over the period March 1992 to June 1995 during low-to-medium solid load and flow conditions. The concentrations (nM) of dissolved elements for the riverine and marine end-members respectively were in the ranges 0.09 to 0.93 and 0.24 to 0.98 for Co, 10 to 53 and 5 to 20 for Ni, 12 to 87 and 5 to 33 for Fe, and 10 to 155 and 26 to 105 for Mn. Co and Mn behave non-conservatively in the Po estuary; an addition to the dissolved phase occurred for these elements that was more marked in the summer period. The concentrations of dissolved and particulate Ni decreased almost linearly with increase in salinity, with more marked variations in dissolved Ni concentration in winter than summer. The concentrations of dissolved and particulate Fe also varied conservatively with salinity. This unusual behaviour for dissolved Fe is attributed to the analytical procedure which excluded kinetically inert colloidal species.  相似文献   

6.
An analysis of the spatial trend of concentrations and of the correlation between heavy metals and total suspended matter was performed in a multidisciplinary study of transport of pollutants in the marine coastal area involving in situ investigations, remote sensing techniques and modeling. This paper presents results concerning the chemical behavior of heavy metals (Cu, Cd, Pb) in the North Adriatic Sea and in particular in the marine deltaic area of the Po river. The samples were collected during the JRC Remote Sensing Campaigns ADRIA 84 and ADRIA 85, carried out in the entire North Adriatic Sea and in the selected area in front of the Po when passing from the fluvial to the marine environment. In the dissolved phase, Cu undergoes a dilution process consistent with the mixing theory, while there is a tenfold increase in Pb concentrations. A pronounced tendency to augment the level in the dissolved phase is observed for all three elements in the pelagic waters. In the particulate phase, Cd and Cu, after a diminution in the nearshore stations, their concentration increases as the pelagic area is approached. The total amount of heavy metals in solid phase of the water decreases according to the dispersion and the sedimentation processes of the fluvial load in the marine water. A satisfactory correlation was found between the Cu and Pb with the total suspended matter (TSS). An attempt was made to characterize sediments and suspended matter in order to assess the role of the organic and mineralogical components on heavy metal behavior.  相似文献   

7.
The sediments of the Tagus estuary North Channel arecharacterised by high concentrations of trace metals andmonosulphides. During dredging operations Cd, Cu and Pb wereanalysed in water and suspended sediments collected 50 to 100 m around the dredging point. Concentrations in bothfractions fluctuated randomly: 2–3 fold for Cd and Cu and 10 for Pb. Since sampling in the dredging point reflectsintegration of rapid chemical reactions, a short-termlaboratory experiment was conducted to follow the geochemicalalterations occurring in the highest turbidity sites. Theexperiment was monitored as a function of time over a period of4 hr in short time intervals. Dissolved oxygen, pH, EH,AVS, SO4 2-, Cl- and metals were monitored in theslurry samples. Iron, Mn, Cd, Pb and Cu were determined in thedissolved fraction (<0.45 μm), in the reactive solid phaseand in the total fraction. Resuspension resulted in asignificant release of Fe, Mn, Cd, Cu and Pb from the solids.Following the release Pb and Cu were almost totally scavengedin the 4 hr by the newly precipitated Fe oxyhydroxides, while more than 50% of the mobilised Cd remained in the dissolved fraction. The less efficient removal of Cd from solution implies a prolonged availability of this metal in the environment.  相似文献   

8.
Heavy metal inputs to Mississippi Delta sediments   总被引：1，自引：0，他引：1  
Heavy metal concentrations were determined in suspended particulates, filtered water and sediment collected in the Mississippi River and from its marine delta. More than 90% of the metal load of the river is associated with particulate matter, which is relatively constant in chemical composition with time and place. The Mississippi River suspended material is similar to average crystal rocks in Fe, Al, V, Cr, Cu, Co, Mn, and Ni concentration but is generally enriched in Zn, Cd and Pb. Sediment cores dated by the Pb 210 method show that the Cd and Pb enrichments are recent phenomenon and are most likely due to the activities of man. About 6000 tonne of Pb and 300 tonne of Cd are being added to the delta sediments by man each year, more than 30 times the amount added to the Southern California Bight. River particulate matter is essentially identical to deltaic sediments in Al, Fe, Cr, V, Cd and Pb concentration, but the sediments are depleted in Co, Cu, Mn, Ni and Zn by 20 to 40%. Chemical leaching of the solids show the metal losses to be primarily from the oxide phase, suggesting diagenetic reduction and mobilization as a mechanism. Trace metal concentrations in filtered Mississippi River water were below the limits for safe drinking water and were similar to world average river values. The abundant river suspended matter and high pH combine to keep dissolved trace metal concentrations low.  相似文献   

9.
Sediment pollution by metals is of high interest considering that it can affect marine life. The estuaries' quality may be reflected by the environmental intertidal zone condition. Subsurface sediments collected at the nude tidal flats from three sampling stations in the Bahía Blanca Estuary were analyzed for total metals concentrations (Hg, Cd, Pb, and Cr), distribution, and geochemical partitioning. Most of the elements (Hg, Cd, and Cr) have shown highest concentration values in the industrial-influenced area. Maximum value of Pb was obtained where the main freshwater input discharges. Intertidal sediments have presented higher values of Cr than the subtidal ones. Cd and Pb contents near the industrial area were strongly higher in the subtidal zones. The distribution of Cd and Pb demonstrated the occurrence of a diffusion pattern from the land toward the sea, showing a dependence on both the metal itself and/or the source. Not all studied metals have shown the highest content in the fine fraction. The chemical partitioning in the fine fractions offered evidence that the tidal flats were an important source as well as sink of metals to the adjacent coastal area. The studies of intertidal sediments provide an integrative knowledge on the potential effects of different trace metals in the environment and they must be used in the contamination studies within coastal areas.  相似文献   

10.
The relationships between heavy metal concentrations and physico-chemical properties of natural lake waters and also with chemical fractions of these metals in lake sediments were investigated in seven natural lakes of Kumaun region of Uttarakhand Province of India during 2003–2004 and 2004–2005. The concentrations of Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb in waters of different lakes ranged from 0.29–2.39, 10.3–38.3, 431–1407, 1.0–6.6, 5.3–12.1, 12.6–166.3, 0.7–2.7 and 3.9–27.1 μg l?1 and in sediments 14.3–21.5, 90.1–197.5, 5,265–6,428, 17.7–45.9, 13.4–32.0, 40.0–149.2, 11.1–14.6 and 88.9–167.4 μg g?1, respectively. The concentrations of all metals except Fe in waters were found well below the notified toxic limits. The concentrations of Cr, Mn, Ni, Cu, Zn, Cd and Pb were positively correlated with pH, electrical conductivity, biological oxygen demand, chemical oxygen demand and alkalinity of waters, but negatively correlated with dissolved oxygen. The concentrations of Cr, Ni, Zn, Cd and Pb in waters were positively correlated with water soluble + exchangeable fraction of these metals in lake sediments. The concentrations of Zn, Cd and Pb in waters were positively correlated with carbonate bound fraction of these metals in lake sediments. Except for Ni, Zn and Cd, the concentrations of rest of the heavy metals in waters were positively correlated with organically bound fraction of these metals in lake sediments. The concentrations of Cr, Mn, Ni, Cu and Zn in waters were positively correlated with reducible fraction of these metals in lake sediments. Except for Cd, the concentrations of rest of the metals in waters were positively correlated with residual fraction and total content of these heavy metals in lake sediments.  相似文献   

11.
Poses dam in the Seine River estuary acts as receptacle of water drain-offs from highly urbanized and industrialized catchment area; therefore, this water is highly contaminated by trace metals. Most trace elements are mainly bound to particulate matter and are incorporated rapidly into the sediments. Scavenging of these metals in the sediments can be reversible due to several perturbations so as sediments also act as a source of pollutants for the overlying water. For instance, natural events (tide, flood, storm) and anthropogenic processes (water management actions) can cause disturbance of sediments and subsequent remobilization of pollutants to the water column, thereby posing a potential threat for aquatic organisms. The purpose of this study was to evaluate the mobility of trace metals by different methods in the Seine estuary sediments. The surface sediment sampled at Poses dam was characterized by high pollution level of Cd, Cu, Zn, and Pb. The estimation of metal bioavailability through ratio ΣSEM/AVS (simultaneously extracted metals/acid volatile sulfides) indicates a potential bioavailability of trace metals. The chemical partitioning using the European Community of Bureau of Reference sequential extraction method revealed that over 85, 82, and 80 % of the total Cd, Zn, and Pb, respectively, were found to be associated with the exchangeable and reducible fractions of the sediment. Another approach used consists in the quantification of dissolved metals released by sediment resuspension experiments in laboratory under controlled conditions. The results indicated that metals are released rapidly from sediment with a sharp peak at the beginning of the experiment, followed by a fast coprecipitation and/or adsorption processes on the suspended particles. Also, the Cd, Pb, and Ni mobility is higher compared to that of the other metals.  相似文献   

12.
The accumulation and speciation of Zn, Cu, Fe and Pb in the sediments of an artificial surface-flow wetland used to treat domestic wastewater near Christchurch, New Zealand, were examined. Water metal concentrations and total suspended solid (TSS) content were determined at the inflow and outflow both in winter and summer, and metal concentrations were analysed in shoots and roots of selected plants. Water and sediment data suggest that the wetland is acting as a sink for Zn, Cu and Pb, while Fe uptake is minimal and the wetland appears to be releasing Fe in the winter. Metal concentrations in the most mobile fractions (exchangeable and bound to carbonates) are negligible. Cu is mostly associated with the organic/sulphide phase, whereas Zn and Pb show a strong affinity for hydroxides and organics/sulphides. A large fraction of all metals is also present in the residual phase, and is therefore unlikely to be released into the overlying water. Metal concentrations are below the low trigger values of the ANZECC sediment quality guidelines, except for Pb near the inflow. However, results of sequential extraction suggest that a significant proportion of Pb occurs in the detrital phase and is therefore not bio-available. Metal concentrations were higher in the roots than in the shoots of both Juncus sp. and Lythrum hyssopifolia. This study shows that, although metal concentrations are low, TSS and metals, except Fe, are effectively removed by the wetland system. The low removal rate of Fe is possibly due to the young age of the wetland and low loading rates.  相似文献   

13.
In Godavari estuary, the enhanced metal concentration in the sediment is localized, and is accompanied by marked enrichment in organic carbon, Kjeldahl nitrogen, and humic acid. High concentration of organic carbon was observed near the riverside sampling stations. A similar pattern was found for the humic acid concentrations. Relatively high organic carbon content was observed in pre-monsoon/monsoon compared to post-monsoon seasons which can be attributed to higher productivity due to upwelling in the former and landrunoff due to excessive rainfall in the later seasons. The trace metals in the sediments were found to be in the following order of their abundanceFe≥Mn≥Zn≥Pb≥Ni≥Cu≥Cd. In monsoon season relatively high levels of trace metals were reported in surface sediments which are transported by currents. The dominant process controllingthe metal enrichment may be either precipitation of metal-humic acid type of complexes. Our results indicate that in the Godavari estuary, the metal distribution is mainly influenced by sedimentarydynamics, while the contamination effect is very limited.  相似文献   

14.
Changes in metal speciation occurring along the river Vormbäckenhave been investigated, and the potential for using such changes to reduce metal transport to areas further downstream has been evaluated.Vormbäcken is situated in a mining region in northern Sweden. Catchment area features likely to influence metal speciation include wetlands situated along the river, addition of treated (liming) effluent water from a mine area, and addition of other surface waters and groundwater. Surface water samples were collected from seven stations along the river on six occasions, representing different flow regimes. The total As, Ca, Cd, Cu, Fe, Pb, and Zn concentrations in the samples were partitioned into particulate (>0.4 μm and 0.2–0.4 μm, or only >0.2 μm) and dissolved (<0.2 μm, either associated with organiccarbon, or as free metal ions and inorganic complexes) fractions by means of filtration and an ion-exchange technique. The most important finding is that, with the exception of Ca, the fraction of particulate bound metals increased with increasing concentrations of particulate Fe. This Fe has its origin in surface waters and groundwater that join the river on its way through the catchment area. It is suggested that adsorption to, or co-precipitation with, such Fe-containing particles may have potential to be used as the initial step in a treatment method based on natural attenuation processes. Furthermore, the fraction of particulate bound metals decreased dramatically upon passing the lake Vormträsket, suggesting that some of these metals may be removed from the river system, at least temporally.  相似文献   

15.
Zabowski  D.  Henry  C. L.  Zheng  Z.  Zhang  X. 《Water, air, and soil pollution》2001,131(1-4):261-273
The impacts of mining to watersheds are highly variabledepending on the type of mining, processing of ores, andenvironmental factors. This study examined the Hei River incentral China, for impacts of gold and iron mining onconcentrations of metals in river water, river sediments andstream-channel soils. No production processing of ores occurson-site at either mine. Total metal content and extractablemetals using DTPA were determined. Total concentrations of Cd,Cu, Pb and Zn were high in some stream sediments and soils nearthe mine sites; metal concentrations ranged from 4–24, 11–100,11–380, and 33–1600 μg g-1 for Cd, Cu, Pb, and Zn,respectively, in soil. Total cadmium was high in all soilsand sediments. Extractable metals were low, with the exceptionof Pb and Cu. At the gold mine, extractable Pb ranged from 8 to33%; extractable Cu ranged from 3 to 21% of total metalconcentration. Chromium and Ni were not above typicalconcentrations in either soils or river sediments. An abundance of carbonates, high river water pH, and high water flow rates all appear to contribute to limiting quantities of metals in the river water. If mining activities are not changed, impacts of mining on downstream metal concentrations in river water should be nominal.  相似文献   

16.
Discontinuous sampling of water for toxic chemicals is unreliable in lotic ecosystems or in systems subjected to sporadic discharges. Such sampling either fails to detect the contaminants or seriously underestimates their concentrations. This study explored the use of resident aquatic insects as biomonitors of trace metal contamination in a river subjected to episodic spills of Mo mill tailings. Aquatic insects at sites downstream from the mill accumulated more Mo and Cu than upstream insects. Due to a prolonged shutdown at the mine, no tailings spills were recorded during this study and Mo and Cu levels in water and bottom sediments declined to near background levels. However, concentrations of these metals in insects declined only slightly. This study indicates that aquatic insects are useful biomonitors of trace metal contamination in an intermittently impacted system. Reduction of elevated trace metal concentrations from the insects occurred at a slower rate than from the non-living components of the river ecosystem thereby facilitating detection of the spills.  相似文献   

17.
Background, Aim and Scope.  The compositional study of suspended matter in water from rivers of different latitudes and climates has revealed that the fine fraction reflects both substrate lithology from source areas or topsoil composition along the course. Metal distribution patterns are also strongly related to the clay mineral fate in fluvial aquatic systems. For the particular case of the coastal area of the Río de la Plata estuary in South America, previous studies have, on the one hand, focused on the analysis of distribution patterns of heavy metals in bottom river sediments and, on the other hand, on the assessment of metal contents in topsoils. The present study was conducted to evaluate the Cu, Pb and Zn distribution in soils and sediments from four drainage basins crossing two differentiated geomorphologic units composed of unconsolidated materials and to understand the metal behaviour. Methods  Data used included the existent, self-produced soil and sediment data sets (grain size, organic matter and Cu, Pb and Zn contents from 124 samples). Analyses were performed by using standardised methods: grain size analysis by sieving and settling; organic matter content based on the reduction of dichromate ion followed by titration; metal content by atomic absorption spectrophotometry following acid digestion. Results and Discussion. The average (% w/w) clay and organic matter content were 45.9 ± 17.1 and 1.5 ± 1.7 for sediments and 32.0 ± 19.8, and 7.5 ± 7.6 for soils, respectively. The raw mean metal concentrations (mg-kg-1 dry weight) for sediments and soils were: Cu: 28.02 ± 27.28, 32.08 ± 21.64; Pb: 32.08 ± 46.94, 68.44 ± 69.25 and Zn: 83.09 ± 150.33, 118.22 ± 74.20, respectively. A good correlation for each clay-normalised metal concentration was found between soil and sediments using regression analysis considering average data for each basin sampling site (r > 0.89, p < 0.05). A comparison between metal concentration levels taking into account geomorphologic units by a t independent sample test showed significant differences for the normalised soil-sediment metal data (p < 0.001), responding to differences in grain size, clay mineralogy, organic matter and neoformed Fe-Mn oxide composition. Conclusion, Recommendation and Outlook  A clear parenthood between the topsoils and the bottom sediments in the study area was found. The Argiudolls from the inner zone are frequently affected by rainwater erosion, which washes the fine materials with sorbed metals and carries them to the streams. These watercourses reach the flat coastal plain, where soil flooding and bottom sediment depositional processes predominate. Here, both soils and bottom sediments are enriched in clay, organic matter and metals. The topography and lithology, under the environmental conditions of a temperate and humid climate control the fate of metals within these small basins. The influence of the physical media on the distribution and fate of pollutants should not be minimised in the understanding of the governing processes from natural systems.  相似文献   

18.
Surface waters, sediments and interstitial waters were collected from 9 sites of the River Stour, UK, during June 1987. The aim was to identify the sources of EC List I (Hg, Cd) and List II (As, Cr, Cu, Ni, Pb, Zn) metals and metalloids to this lowland river system and to assess the magnitude of metal enrichment. The study reach spanned some 60 km, traversing rural and urban landscapes. Results indicate that the larger municipal sewage treatment works (STW), which receive industrial effluents, were the major source of metals, but smaller rural works also exerted some contaminative influences. Metal concentrations in bottom sediments, displayed 2–11 fold increases over catchment background levels with maximum loadings coinciding with discharges from the Great Cornard and Sudbury STWs. Elevations in water column metal concentrations were also apparent downstream of point source inputs, but concentrations were consistently below designated ‘Water Quality Standards’. Distance from the point source, sediment texture and hydrology appeared to be the main factors responsible for the observed distribution of metals within this river system.  相似文献   

19.
The sediments of four rivers in Northern Germany were analysed for heavy metals. 371 sediment samples were taken from 24 investigation sites of the rivers Elbe, Eider, Trave and Schwentine and from North Sea tidal flat areas. Within each investigation site strong positive relationships exist between the heavy metal contents and the contents of the fine size fractions < 2 μm and < 20 μm of the sediments. To compare the metal contents in the sediments from different areas, differences in grain size were eliminated by computing the metal contents for a clay content of 25% by means of regression equations.The fluvial sediments at a few inland investigation sites, as well as the tidal flat sediments are not detectably polluted with heavy metals. Their metal contents could be used as background values for computing enrichment factors of polluted fluvial deposits.Sediments from the river Elbe in and upstream of the port of Hamburg, and from some parts of the rivers Eider and Trave near industrial and densely populated districts, are highly enriched with heavy metals. The highest enrichment factors are for Hg 85, Cd 56, Pb 37, Cu 34, Zn 29, As 19, Cr 6, Ni 4 and Co 3 times the background values.The ecological importance of the heavy metal contents in the sediments is discussed.  相似文献   

20.
The Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn contents of the sand, silt, and clay fractions were determined for soils, urban street dust and bottom- and suspended-sediments sampled in the Menomonee River watershed, Wisconsin. The samples were dispersed by ultrasound prior to fractionation. The ultrasound dispersion avoids chemical contamination or alteration resulting from use of chemical dispersants and insures the dispersion of aggregates present in mechanically-sieved samples. Chemical analyses of fractionated samples were more precise than analyses of unfractionated samples in identifying areas in the watershed receiving pollutant inputs. Higher levels of Cr, Cu, Fe, and Ni were found in the coarser particles than in the finer particles of urban street dust samples. The Cd, Pb and Zn contents of some bottom and suspended sediments were greater than in the soils of the watershed. Contents of these metals were correlated significantly with each other in the clay-sized fraction of sediments but not in soils. The metal contents of sediments were largely controlled by vehicular emission.  相似文献   

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