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1.
Concentrations of copper (Cu), silver (Ag), and cadmium (Cd) in eastern oysters (Crassostrea virginica) from the upper Patuxent River estuary analyzed since 1986 (Cd since 1991) were high relative to concentrations in other sites in the United States analyzed by the National Oceanic and Atmospheric Administration National Status and Trends program. Patuxent River oysters had above average concentrations of Ag and Cu, and unusually high concentrations of Cd. Metal concentrations were highest in summer, a period in which oyster meat condition index was relatively low. Copper values were highest in 1986–1987, likely elevated by erosion from Cu-Ni alloy condensers at a local power plant. Silver and Cd values exhibited more year-to-year variation. A number of factors were examined as candidates to explain the interannual differences, including river flow, salinity, and oyster condition, but none was able to explain the high and low years. Samples collected in spring and late summer of 1996 at a number of oyster bars located along the length of the Patuxent River showed that concentrations of all three metals increased with distance up-river. For Cd, the upstream increase was linear with distance, while for Ag and Cu, there was a secondary maximum near river km 16. A close correlation was observed between Ag and Cu for individuals at each site, with a poorer correlation between Cd and either Ag or Cu.  相似文献   

2.
Nearly one thousand oysters (Crassostrea virginica) were collected at 15 sites on four sampling trips to Galveston Bay during 1992–1993. Iron, silver, arsenic, cadmium, copper, lead, and zinc were determined in the whole soft part of the individual oysters. Trace metal concentrations were found to vary among individuals within a site on a given trip, and spatially and temporally around the Galveston Bay estuarine system. Differences in metal concentrations from site to site were a factor of 5 or more for some metals, and similar differences were found from time to time at a given site. Zinc was found in anomalously high concentrations at several sites, mainly along the west side of Galveston Bay. Isolated high values of other metals were found scattered throughout the bay; however, only one site (GBSL, near Swan Lake in lower Galveston Bay) was found to have significantly higher than average concentrations for several metals (Ag, Cu, Pb, and Zn). One obvious trend found in this study was that metal concentrations, except for As, were highest in the summer, followed by the fall, and lowest in the winter and spring. The temporal changes in metal concentrations in oysters cannot be explained by changes in body weight in different seasons, and are apparently caused by changes in environmental conditions (e.g., metal input, salinity) or biological activity (e.g., metabolism, depuration).  相似文献   

3.
Trace element distributions, partitioning, and speciation were examined at 15 sites in the Patuxent River watershed from May 1995 through October 1997 to determine possible sources of trace elements to the river and estuary, to examine the relationship of the trace element discharges to freshwater discharges as well as to land use and geographic region, to validate previous estimates of loadings to the river, and to provide baseline data for trace elements in the Patuxent River watershed and estuary. Six freshwater sites were examined, representing different basins and geographic provinces, and nine sites along the estuarine salinity gradient. Subregions within the watershed varied considerably in concentrations and areal yields for some elements. Concentrations of As, Cd, Ni, Pb, and Zn were elevated in the Coastal Plain sites compared to the Piedmont sites, while Cu and Hg were more evenly distributed. Cadmium, Cu, Hg, Ni, Pb, and Zn showed overall positive correlations with river flow while As and methylHg (meHg) showed negative correlations with river flow. Concentrations of trace elements in the estuarine portion of the river were generally low, and consistent with mixing between Patuxent River water with elevated concentrations and the lower concentrations of the Chesapeake Bay. Interesting features included a local Cd maximum in the low salinity region of the estuary, probably caused by desorption from suspended sediments, and a significant input of water containing high As concentrations from the Chesapeake Bay and from As being released from bottom sediments in summer. Comparisons between the estimated annual flux of trace elements and the estimates of suspected source terms (atmospheric deposition, urban runoff, and known point sources) suggest that, except for Hg, direct atmospheric deposition is small compared to fluvial loads. Current estimates of trace element inputs from point sources or from urban runoff are inadequate for comparison with other sources, because of inappropriate techniques and/or unacceptably high detection limits. A complete examination of trace element dynamics in the Patuxent River (and in other coastal systems) will require better data for these potential sources.  相似文献   

4.
The continued urbanization of coastal watersheds can influence the quality of water that enters rivers and estuaries. Intelligent management of aquatic resources will require the capability to quantitatively assess and evaluate the impacts of alterations in surface waters that result from changes in patterns of land use. An aquatic ecosystem model was developed and linked to an empirical landscape model to estimate ecological risks posed by nutrients and potentially toxic trace elements (copper [Cu], cadmium [Cd], arsenic [As]) in the Patuxent River, Maryland. The empirical landscape model translated reductions in croplands within the Patuxent River watershed into corresponding changes in nitrate estimated to enter the river. Trace element concentrations were increased in relation to urbanization associated with the loss of agricultural lands in the watershed. The aquatic ecosystem model used the altered inputs of nutrients and trace elements to estimate changes in the annual production dynamics of selected producer and consumer populations within the Patuxent River. The models were implemented for four mainstem locations that defined a transect from the upper freshwater portion of the river to downstream estuarine locations. Ecological impacts were estimated for 4 hypothetical changes in land use that consisted of 10%, 7.5%, 5%, and 2.5% watershed coverage by cropland. Impacts were estimated as the probability (risk) of different magnitudes of increases or decreases in total annual production of populations representative of freshwater and estuarine food webs in the Patuxent River.  相似文献   

5.
Larvae of the naked goby,Gobiosoma bosci, were collected during the spring and early summer of 1977 in the upper tidal Patuxent River, Maryland. Larvae first appeared in the collections on May 5. Weekly night sampling at 26 stations covering 28 km of the Patuxent illustrated the upriver movement of larvae, at an estimated rate of about 1 km per day. Larval densities quickly reached high levels, with a maximum density of more than 6,000 larvae per 100 m3 at one station on June 16. By June 23, the mean larval density for the entire 28 km stretch of the river was 1,825 larvae per 100 m3. Length-frequency distributions of the larvae illustrate the growth of the larvae, continual recruitment into the population, and a gradient in mean population length over the sampling transect that was due to the presence of the smallest larvae in the lower stations.  相似文献   

6.
We used a sequential extraction technique and 210Pb dating to determine the chemical form and amount of particulate phosphorus (PP) that is retained during burial in 1-m-long sediment cores collected along a salinity gradient from tidal freshwater to the mesohaline waters of the Patuxent River, a subestuary of the Chesapeake Bay. PP buried in the study sites with salinity values ≤3 was similar in concentration and form to PP entering the Patuxent from the watershed, suggesting efficient sequestration by the sediments at these low-salinity sites. PP extracted with citrate–dithionite–bicarbonate was the dominant form of PP at all salinities and all depths, and organic-P was the second most abundant fraction. We estimated that 81% of PP entering from the watershed is trapped in the sediments of the upper Patuxent subestuary and that the subtidal sediments retain three times as much PP as the marshes adjacent to the study sites.  相似文献   

7.
Oysters from paired sites of high and low spatfall at three mid-Chesapeake Bay locations were analyzed for tissue copper and tissue zinc as well as copper in aufwuchs scraped from the upper (right valve) shell surface. Paired sites had no significant differences in oyster tissue copper, aufwuchs copper or oyster tissue copper-zinc ratio. In the laboratory, natural aufwuchs material on oyster shell rapidly concentrated copper up to 10× from copper-enriched estuarine water, with a partition coefficient (Ka) of 0.640 I kg?1. Aufwuchs-sorbed copper resisted depuration, suggesting a strong metal-binding substance in aufwuchs material. Eyed veliger oyster larvae (setting stage) exposed to oyster shell fragments having copper-enriched aufwuchs showed normal setting preference for bottoms and edges of shell surfaces but a slight decrease in total set with increasing aufwuchs copper concentration. Settled oyster spat died or failed metamorphosis with LD50=534 μg Cu g?1 aufwuchs. Since mid-Bay aufwuchs copper concentrations averaged 35.5 μg?1, ranging up to 103 μg g?1, oyster spatfall probably is not affected solely by present natural aufwuchs copper concentrations, but the potential for problems exists.  相似文献   

8.
Among environmental contaminants, heavy metals are currently considered to be some of the most toxic ones present worldwide due to their harmful effects on organisms and ability to bioaccumulate in aquatic systems. In this work, the concentration of heavy metals (Cd, Cu, Pb, Zn, Ni and Cr) in Brachidontes rodriguezii and in the fine sediments of several coastal sites at the southwest of Buenos Aires Province, Argentina is analyzed. The Bahía Blanca Estuary and Pehuen-Có beach are located in a highly complex oceanographic and ecological regional system, which creates the basis of one of the most valuable Argentinean habitats for fishing commercial species. An assessment, which involved analyzing distribution pattern of trace metals, comparative studies with sediment and ecological quality guidelines; and a sequential and integrated index analyses approach (containing Metal Pollution Index, Biosediment Accumulation Factor, Geo-accumulation Index (Igeo), Pollution Load Index and the mean Probable Effect Level quotients), was followed to estimate enrichment and risks of heavy metals in the sediments and in the mussels from these study areas. The results showed higher concentrations of some heavy metals (e.g., Cd, Cr and Ni) in mussels collected at Pehuen-Có, while no spatial differences in sediments were observed. According to the international environmental regulations, mean values of trace metals in mussels allowed to place both sites between “unpolluted and moderately polluted” and between the “low and medium category” of pollution. Furthermore, the mean concentrations found were within the detected ranges in other coastal sites worldwide.  相似文献   

9.
Water discharge from the Patuxent River into its estuary was near-average (95%) during the water year 1968–1969 although precipitation was only 79% of the average. Suspended-sediment discharge into the estuary, however, was more then double the normal yield (344 metric tons/km2 compared to 143 metric tons/km2). These increases in runoff and suspended-sediment yields, despite decreased precipitation, must be attributed to urbanization of the drainage basin.The maximum measured suspended-sediment concentrations in the rural Middle Patuxent basin (Piedmont Province) increased only 40-fold during an increase from “average” to high water runoff (15 mg/l to 600 mg/l). In the portion of the Little Patuxent River basin undergoing urbanization (Piedmont portion), stream concentrations increased by over two orders of magnitude (20 mg/l to 2400 mg/l) as a result of heavy rainfall. The area undergoing urbanization of the Little Patuxent yielded more than twice as much suspended sediment per unit area as the rural Middle Patuxent (620 metric tons/km2 versus 290 metric tons/km2). This increase also is interpreted to be the direct result of erosion of soils denuded or disturbed during urban construction.Using the Middle Patuxent as a “standard” for normal erosion rates in rural areas, construction sites contributed about 82% of the suspended sediment discharged by the Patuxent River into its estuary even though such sites represented only 23% of the drainage basin.  相似文献   

10.
Surface sediment samples were collected at 21 offshore sites in western Xiamen Bay, Southeast China. Total concentrations of Li, V, Cr, Co, Ni, Cu, Zn, Sr, Mn, Pb, Ba, Fe, and Ti were determined by inductively coupled plasma-optical emission spectrometry; Hg was determined by atomic fluorescence spectrometry. A modified BCR sequential extraction procedure was used to extract fractions of the above elements. Concentrations of Pb, Cr, and Hg at most sites met the primary standard criteria of Marine Sediment Quality except site S12 for Pb and S7 for Cr, while concentrations of Zn at 17 sites and Cu at seven sites exceeded the criteria. The mean concentration of Hg was three times higher than the background, with a possible source being the Jiulong River. Fe, Ti, Ba, Co, V, and Li dominated the residual phase, mainly from terrestrial input. Ni, Cr, Pb, and Hg in the non-residual phase varied largely between sites. Sr, Mn, Cu, and Zn were mainly in the non-residual fraction. Most sites showed considerable ecological risk; exceptions were site S7 (very high) and sites S10, S11, and S14 (moderate). Cu showed moderate-to-high pollution and Pb exhibited no-to-low pollution, while other metals had a non-pollution status according to their ratios of secondary phase to primary phase (RSP). Results of two assessment methods showed moderate pollution and a very high ecological risk for Cu, Zn, Ni, and Cr at site S7, which might be due to the local sewage treatment plant.  相似文献   

11.
The impact of waste disposal on trace metal contamination was investigated in eleven wetlands in the Lake Victoria Basin. Samples of soil, water and plants were analysed for total Zn, Cu, Pb and Ni concentrations using flame atomic absorption spectrophotometry. The trace metal concentrations in soil were the highest in Katanga wetland with the highest mean concentrations of 387.5±86.5 mg/kg Zn, 171.5±36.2 mg/kg Pb, 51.20±6.69 mg/kg Cu and 21.33±2.23 mg/kg Ni compared to the lowest levels observed at Butabika (30.7±3.2 mg/kg Zn, 15.3±1.7 mg/kg Pb, 12.77±1.35 mg/kg Cu and 6.97±1.49 mg/kg Ni). Katanga receives waste from multiple industrial sources including a major referral city hospital while Butabika is a former solid waste dumpsite. Wetland soil near a copper smelter had a Cu concentration of 5936.3±56.2 mg/kg. Trace metal concentrations in industrial effluents were above international limits for irrigation water with the highest concentrations of 357,000 μg/L Cu and 1480 μg/L Zn at a Cu smelter and 5600 μg/L Pb at a battery assembling facility compared to the lowest of 50 μg/L Cu and 50 μg/L Zn in water discharged from Wakaliga dumpsite. Uptake of trace metals from soil differed from plant to plant and site to site. Higher levels of trace metals accumulated in the root rather than in the rhizome and the least amount was in the leaf. The study identifies industry as a potential source of trace metal contamination of water and the environment pent-up need for policy intervention in industrial waste management.  相似文献   

12.
Industrialization, urbanization, and agricultural practices are 3 of the most important sources of metal accumulations in soils. Concentrations of Cr, Mn, Ni, Cu, Pb, Zn and Cd were determined in surface soils collected under different land uses, including urban (UR), industrial (IN-1 and IN-2), agricultural (AG), abandoned unused (AB), and natural (NA) sites to examine the influence of anthropogenic activities on metals in soils formed in a typical Mediterranean environment. The highest concentrations of Cr, Cd, and Pb observed in the NW industrial area (IN-2) were 63.7, 3.34 and 2330 mg metal kg−1 soil, for each metal, respectively. The SW industrial area (IN-1) contained the highest Zn content at 135 mg kg−1. However, soils with the highest concentrations of Ni and Cu were located in AG sites at 30.9 and 64.9 mg kg−1 soil, respectively. Sampling locations with the highest concentrations of Mn were identified in AB sites. Using the concentrations of metals at the NA sites as the baseline levels, soils collected from all other land uses in the study area exhibited significantly higher total contents of Zn, Mn, Cr and Ni. Metal enrichment was attributed to fertilizer and pesticide applications, industrial activities, and metal deposition from a high volume of vehicular traffic (for Pb and Cd). High concentrations of Mn in some samples were attributed to parent materials. The study demonstrated that anthropogenic activities associated with various land uses contribute to metal accumulation in soils and indicated a need to closely monitor land management practices to reduce human and ecological risks from environmental pollution.  相似文献   

13.
The concentrations of Cd, Cu, Mn, Ni, Pb, Fe and Zn were determined in superficial sediments extracted from nine zones of Budi Lagoon, located in the Araucanía Region (Chile). The concentrations of these metals were determined by flame atomic absorption spectroscopy and the method was validated using certified reference material (marine sediment). The concentration ranges found for the trace elements were: Pb < 0.5; Cd < 0.2–3.9; Cu 21.8–61.9; Ni 31.2–59.4; Zn 54.5–94.8 mgkg?1 (dry weight). The elements that registered the highest concentrations were Mn 285.4–989.8 mgkg?1 and Fe 4.8–10.6 %. The lagoon cluster analysis of the stations was divided into three groups (Temo station with high Cu and low Mn concentrations, Bolleco, Comué, Allipén and Deume 3 stations presented highest Cd concentration, and another group Botapulli, Río Budi, Deume 2 and Deume 1 stations presented low levels of Cd). The textural characteristics of the sediment were determined (gravel, sand and mud) and the results were correlated with the concentrations of the metals in the various study zones. The sediments of Budi Lagoon presented high levels of Fe and Mn, which are of natural origin and exceed the maximum values recorded by many authors. With respect to the recorded concentrations for Cd, Cu, Ni and Zn, are within the ranges published by other authors in similar works. The Pb element was not detected. The results were subjected to statistical analysis to evaluate the correlations between the content of the elements and obtain the site of sediment.  相似文献   

14.
The aim of the present study was to assess the levels of heavy metal contamination in soils and its effects on human health in the northern Telangana, India. Soil samples were collected randomly from 15 sampling stations located in the northern Telangana and analyzed for arsenic (As), chromium (Cr), copper (Cu), zinc (Zn), nickel (Ni), and lead (Pb). The index of geo-accumulation (Igeo), ecological risk index (ERI), hazard quotient (HQ), hazard index (HI), cancer risk (CR), and lifetime cancer risk (LCR) were used to estimate the heavy metal pollution and its consequence to human health. Results indicated that As, Zn, Cu, Pb, and Ni were within recommended limits, while Cr concentration (60 mg/kg) exceeded the maximum recommended limit in 93% of soil samples. The HI values of Cu, Ni, and Zn were all less than the recommended limit of HI?=?1, indicating that there were no non-carcinogenic risks from these elements for children and adults. LCR for As and Cr concentrations of the soils was found higher than the acceptable threshold value of 1.0E?04, indicating significant carcinogenic risk due to higher concentration of these metals in the soils of the study region. The chronic daily intake of the metals is of major concern as their cumulative effect could result in several health complications of children and adults in the region. Therefore, necessary precautions should be taken to eradicate the health risk in the study region.  相似文献   

15.
Coastal uses and other human activities have inevitably impinged on the Gulf environment; therefore, these regions require continuous monitoring. The investigated area covered the maximum fragments of Dubai coastal region in the Arabian Gulf. The determination of major oxides and trace metal concentrations in Dubai sediments revealed three heavily and moderately contaminated regions. One is in the far northeastern part at Al-Hamriya Sts 1–3 and contaminated by Fe, Cu, Pb, and Zn; the second is in the mid-northeastern part at Dry Docks and contaminated by Cu, Ni, Pb, and Zn; and finally, the third is in the near southwestern part at Dubal and contaminated by Fe, Mg, Cr, Ni, and Zn. Al-Hamriya St 3 represented the highest values of Cu, Pb, and Zn, whereas Dubal exhibited the maximum values of Fe, Mg, Ba, Cr, Mn, Ni, and V. The anthropogenic discharge and natural deposits are the main sources of contamination. In general, all trace and major elements showed the minimal levels at Jebel Ali Sanctuary (Sts 11, 12, 13) except for Sr and Ca, which showed their maximum values. The highest concentrations of Ca and Sr are mainly attributed to carbonate gravel sands and sands, which cover most stations. Each of V and Ni showed negative correlation with TPH, which may be indicated that the source of oil contamination in the region is not related to crude oil but mostly attributable to anthropogenic sources. The significant positive correlation, which was found between trace metals and TOC indicates that organic matter plays an important role in the accumulation of trace metals in case of Cu, Zn, and Pb.  相似文献   

16.
This paper reports on the aquatic chemistry of trace elements in terms of spatial and temporal distribution, but also pollution sources in the transboundary watershed of the Seversky Donets River (Ukraine/Russia). Bed sediments and filtered water were collected from the Udy and Lopan Rivers at sites from the river source in the Belgorod region (Russia) to rural and urban areas in the Kharkiv region (Ukraine) in May and August 2009. Priority trace elements (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn), an urban tracer (Ag) and additional metals (Co, Mo, V) and Th were measured in stream water and sediments. The low levels and variability of Th-normalized concentrations indicated the absence of geochemical anomalies in the upstream part of the rivers and suggested that these data represent a regional baseline for trace elements in bed sediments. In contrast, water and sediments within the city of Kharkiv were contaminated by Ag, Pb, Cd, Cu, Cr and Zn, which are mainly attributed to municipal wastewater inputs and urban run-off. Results of the environmental quality assessment showed that element concentrations in the sediments can be considered as potentially toxic to aquatic organisms in sites downstream of the wastewater discharges.  相似文献   

17.
This paper uses results from the National Oceanic and Atmospheric Administration’s National Status and Trends Program (NS&T) to place the environmental quality of Long Island Sound in a broader perspective. It compares levels of contaminants in blue mussels from ten Long Island Sound sites and in sediments from seven Long Island Sound sites with concentrations in the same media at 87 and 221 other sites, respectively, where comparable samples were obtained. In sediments, the levels of both trace metals and organic contaminants tend to be relatively high for Long Island Sound sites. This is especially true for five of the twelve metals (silver, cadmium, copper, lead, and zinc) and for five of six categories of organic contaminants (total chlordane, low molecular weight polycyclic aromatic hydrocarbons (PAHs), high molecular weight PAHs, total polychlorinated biphenyls, and total dichlorodiphenyltrichloroethanes). In mussels, the organic contaminant categories exhibit relatively high levels, but this is not true for most of the metals. In fact, four of the metals—arsenic, mercury, selenium, and zinc—show evidence of relatively low levels in mussels from Long Island Sound compared to other NS&T locations.  相似文献   

18.
Vertical profiles of trace metal (Cd, Pb, Zn, Cu, Ni) concentrations, organic matter content, carbonate content and granulometric composition were determined in two sediment cores from the submarine pit Dragon Ear (Middle Adriatic). Concentrations of the analyzed metals (Cd: 0.06–0.12 mg kg−1, Pb: 28.5–67.3 mg kg−1, Zn: 17.0-65.4 mg kg−1, Cu: 21.1–51.9 mg kg−1, Ni: 27.8–40.2 mg kg−1) were in usual range for Adriatic carbonate marine sediments. Nevertheless, concentrations of Cu, Zn, and especially Pb in the upper layer of sediments (top 12 cm) were higher than in bottom layer, while Cd and Ni concentration profiles were uniform. Regression analysis and principal component analysis were used to interpret distribution of trace metals, organic matter and carbonate content in sediment cores. Results of both analysis showed that concentrations of all trace metals in the core below the entrance to the pit were significantly positively correlated with organic matter and negatively correlated with carbonate, while in the core more distant from the entrance only Pb showed significant positive correlation with organic matter. Obtained results indicated that, except for lead which was enriched in surface sediment, in the time of sampling (before the building of the nautical marina) investigated area belonged to unpolluted areas.  相似文献   

19.
The concentrations of heavy metals (Cr, Co, Ni, Cu, Zn, Pb, Cd, As, Hg, and Fe) in sediments of the Yangtze River, China, were investigated to evaluate levels of contamination and their potential sources. The lowest heavy metal concentrations were found in the source regions of the river basin. Relatively high concentrations of metals, except Cr, were found in the Sichuan Basin, and the highest concentrations were in the Xiangjiang and Shun’anhe rivers. All concentrations, except Ni, were higher than global averages. Principal component analysis and hierarchical cluster analysis showed that Zn, Pb, As, Hg, and Cd were derived mainly from the exploitation of various multi-metal minerals, industrial wastewater, and domestic sewage. Cu, Co, and Fe were derived mainly from natural weathering (erosion). Cr and Ni were derived mainly from agricultural activities, municipal and industrial wastewater. Sediment pollution was assessed using the geoaccumulation index (I geo) and enrichment factor (EF). Among the ten heavy metals assessed, Cd and Pb had the highest I geo values, followed by Cu, As, Zn, and Hg. The I geo values of Fe, Cr, Co, and Ni were <0 in all sediments. EF provided similar information to I geo: no enrichment was found for Cr, Co, and Ni. Cu, Zn, As, and Hg were relatively enriched at some sites while Cd and Pb showed significant enrichment.  相似文献   

20.
《Applied Geochemistry》2005,20(6):1195-1208
The upper intertidal zone, and salt marshes in particular, have been shown by numerous authors to be effective medium to long-term storage areas for a range of contaminants discharged or transported into the estuarine environment. A detailed understanding of the specific controls on the trapping and storage of contaminants, however, is absent for many estuarine systems. This paper examines heavy metal distribution and accumulation in two contrasting Spartina sp.-dominated macrotidal salt marsh systems – a rapidly prograding, relatively young marsh system at the Vasiere Nord, near the mouth of the Seine estuary, France, and a more mature, less extensive marsh system in the Medway estuary, UK. The spatial distribution of the heavy metals Zn, Cu, Pb, Ni and Co is assessed and compared in both systems via detailed surface sampling and analysis, while the longer-term accumulation of these metals and its temporal variability is compared via analysis of dated sediment cores. Of the two sites studied, the more extensive marsh system at the Vasiere Nord in the Seine estuary shows a clear differentiation of heavy metals across the marsh and fronting mudflat, with highest metal concentrations found in surface sediments from the more elevated, interior marsh areas. At Horrid Hill in the Medway estuary, the spatial distribution of heavy metals in surface sediments is more irregular, and there is no clear relationship between heavy metal concentration and site elevation, with average concentrations similar in the marsh and fronting mudflats. Sediment core data indicate that the more recent near-surface sediments at Horrid Hill are clearly more contaminated than those at greater depth, with most heavy metal contamination confined to the upper 20 cm of the sediment column (with peak metal input in the late 1960s/early 1970s). In contrast, due to extremely rapid sediment accretion at the mouth of the Seine, heavy metal distribution with depth at the Vasiere Nord site is relatively erratic, with metal concentrations showing a general increase with depth. These sediments provide little information on temporal trends in heavy metal loading to the Seine estuary. Overall, heavy metal concentrations at both sites are within typical ranges reported for other industrialised estuaries in NW Europe.  相似文献   

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