首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 504 毫秒
1.
《Applied Geochemistry》1998,13(3):329-337
The Oder river drains a highly polluted industrial area and enters the Baltic Sea through a system of shallow lagoons. Surficial sediments in the discharge area of the Oder are highly enriched in heavy metals compared to their preindustrial background levels. Pore-water studies in short sediment cores reveal anoxic environments over the entire sediment column, except for a suboxic layer in the uppermost 5 to 20 mm of the sediment where Mn- and Fe-oxyhydroxides are reduced by organic matter. Heavy metals (such as Cu, Zn and Pb) are mobilized within the suboxic zones in the inner lagoon (represented by the Oder Lagoon) and in the open Baltic (represented by the Arkona Basin). The Achterwasser, located between the Oder Lagoon and the Arkona Basin, is directly affected by sea-level fluctuations in the Baltic. Pore-water studies indicate that, in contrast to the situation in the Oder Lagoon and Arkona Basin, surficial sediments of the Achterwasser represent a sink for heavy metals. This is associated with the high rate of Fe-sulphide formation occurring there, at least seasonally during salt-water inflow.  相似文献   

2.
《Applied Geochemistry》1998,13(3):349-358
Geochemical data from 4 cores taken in the Eastern Gotland Basin of the Central Baltic Sea (68 to 243 m water depth) show that depositional conditions for heavy metals in sediments were similar at all water depths prior to anthropogenic influxes. After the onset of industrialization, the deep anoxic parts of the basin expanded at irregular intervals and the <63 μm fractions of the sediments became characterized by high organic C and heavy-metal accumulation rates. The difference between the enrichment patterns in the basin and on the slope suggests that material enriched in organic matter (and associated trace elements) and in sulphides (and associated trace elements) is preferentially deposited in the basin. The composition of the sediments in the basin therefore reflects the effects of lateral transport of the sediment, which enriches organic C in the deepest part of the basin and of anoxia in the deep water of the basin, where metal sulphides are formed. Previous estimates of the timing of the onset of industrial pollution in the Central Baltic may have been in error because these new data suggest that this began in the Eastern Gotland Basin in about 1870.  相似文献   

3.
沿海表层沉积物中重金属的有效结合态   总被引：13，自引：0，他引：13       下载免费PDF全文
以浙江沿海表层沉积物为研究对象,系统地研究了重金属有效结合态与沉积环境、矿物组成和人为排放等环境因素之间的相互关系.结果表明:沿海表层沉积物中重金属的积累数量,呈现出潮汐河口沉积物>沿海沉积物>强潮汐河口沉积物的趋势,这反映了不同沉积类型对重金属富集作用的差异;重金属的有效结合态,总体上以铁锰氧化物结合态>碳酸盐结合态>硫化物及有机结合态>可交换态的顺序存在,但是不同的重金属或同种重金属在不同的采点,主要有效结合态的比例存在明显的差异,这不仅与重金属的地球化学性质、沉积环境和沉积物中的粘土矿物组成有关,更受到重金属污染物的人为排放量的影响.  相似文献   

4.
In this study, redox-dependent phosphorus (P) recycling and burial at 6 sites in the Baltic Sea is investigated using a combination of porewater and sediment analyses and sediment age dating (210Pb and 137Cs). We focus on sites in the Kattegat, Danish Straits and Baltic Proper where present-day bottom water redox conditions range from fully oxygenated and seasonally hypoxic to almost permanently anoxic and sulfidic. Strong surface enrichments of Fe-oxide bound P are observed at oxic and seasonally hypoxic sites but not in the anoxic basins. Reductive dissolution of Fe-oxides and release of the associated P supports higher sediment-water exchange of PO4 at hypoxic sites (up to ∼800 μmol P m−2 d−1) than in the anoxic basins. This confirms that Fe-bound P in surface sediments in the Baltic acts as a major internal source of P during seasonal hypoxia, as suggested previously from water column studies. Most burial of P takes place as organic P. We find no evidence for significant authigenic Ca-P formation or biogenic Ca-P burial. The lack of major inorganic P burial sinks makes the Baltic Sea very sensitive to the feedback loop between increased hypoxia, enhanced regeneration of P and increased primary productivity. Historical records of bottom water oxygen at two sites (Bornholm, Northern Gotland) show a decline over the past century and are accompanied by a rise in values for typical sediment proxies for anoxia (total sulfur, molybdenum and organic C/P ratios). While sediment reactive P concentrations in anoxic basins are equal to or higher than at oxic sites, burial rates of P at hypoxic and anoxic sites are up to 20 times lower because of lower sedimentation rates. Nevertheless, burial of reactive P in both hypoxic and anoxic areas is significant because of their large surface area and should be accounted for in budgets and models for the Baltic Sea.  相似文献   

5.
Salinity variations in restricted basins like the Baltic Sea can alter their vulnerability to hypoxia (i.e., bottom water oxygen concentrations <2 mg/l) and can affect the burial of phosphorus (P), a key nutrient for marine organisms. We combine porewater and solid-phase geochemistry, micro-analysis of sieved sediments (including XRD and synchrotron-based XAS), and foraminiferal δ18O and δ13C analyses to reconstruct the bottom water salinity, redox conditions, and P burial in the Ångermanälven estuary, Bothnian Sea. Our sediment records were retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. We demonstrate that bottom waters in the Ångermanälven estuary became anoxic upon the intrusion of seawater in the early Holocene, like in the central Bothnian Sea. The subsequent refreshening and reoxygenation, which was caused by gradual isostatic uplift, promoted P burial in the sediment in the form of Mn-rich vivianite. Vivianite authigenesis in the surface sediments of the more isolated part of the estuary ultimately ceased, likely due to continued refreshening and an associated decline in productivity and P supply to the sediment. The observed shifts in environmental conditions also created conditions for post-depositional formation of authigenic vivianite, and possibly apatite formation, at ～8 m composite depth. These salinity-related changes in redox conditions and P burial are highly relevant in light of current climate change. The results specifically highlight that increased freshwater input linked to global warming may enhance coastal P retention, thereby contributing to oligotrophication in both coastal and adjacent open waters.  相似文献   

6.
On their way from the Rhine estuary into the North Sea and Dutch Wadden Sea, Rhine sediments “lose” large portions of their original heavy metal concentrations. Until now these losses were explained by a mobilization process, solubilization — the decomposition products of organic matter form soluble organometallic complexes with the metals of the sediment. Our investigations of the sediments of the Elbe clearly indicate that a mixing process, whereby highly polluted Elbe sediments mix with relatively non-polluted North Sea sediments, rather than solubilization, is the cause of the dilution of heavy metals in the sediments of the Elbe estuary. Because of the similarity of the Elbe data with those from the Rhine River, we propose that a mixing process is also effective in the Rhine estuary and adjacent North Sea areas. The mechanism by which heavy metals are “diluted” is important to the marine ecosystem. In the mixing process proposed in this paper, the heavy metals fixed to the suspected material are trapped in bottom sediments of the marine environment, whereas solubilization would increase the concentration of heavy metals in the sea water and thus they would be more available for uptake by aquatic organisms.  相似文献   

7.
Recent sediment cores of the western Baltic Sea were analyzed for heavy metal and carbon isotope contents. The sedimentation rate was determined from radiocarbon dates to be 1.4 mm/yr. The ‘recent age’ of the sediment was about 850 yr. Within the upper 20 cm of sediment, certain heavy metals became increasingly enriched towards the surface; Cd, Pb, Zn and Cu increased 7-, 4-, 3- and 2-fold, respectively, whereas Fe, Mn, Ni and Co remained unchanged. Simultaneously, the radiocarbon content decreased by about 14 per cent. The enrichment in heavy metals as well as the decrease in the 14C-concentration during the last 130 ± 30yr parallels industrial growth as reflected in European fossil fuel consumption within that same period of time. The near-surface sediments are affected by residues released from fossil fuels at the rate of about 30 g/m2 yr for the past two decades. The residues have a pronounced effect on the heavy metal and carbon isotope composition of the most Recent sediments allowing estimates to be made for sedimentation, erosion and heavy metal pollution.  相似文献   

8.
Partitioning of heavy metals in surface Black Sea sediments   总被引：1，自引：0，他引：1  
Bulk heavy metal (Fe, Mn, Co, Cr, Ni, Cu, Zn and Pb) distributions and their chemical partitioning, together with TOC and carbonate data, were studied in oxic to anoxic surface sediments (0–2 cm) obtained at 18 stations throughout the Black Sea. TOC and carbonate contents, and available hydrographic data, indicate biogenic organic matter produced in shallower waters is transported and buried in the deeper waters of the Black Sea. Bulk metal concentrations measured in the sediments can be related to their geochemical cycles and the geology of the surrounding Black Sea region. Somewhat high Cr and Ni contents in the sediments are interpreted to reflect, in part, the weathering of basic-ultrabasic rocks on the Turkish mainland. Maximum carbonate-free levels of Mn (4347 ppm), Ni (355 ppm) and Co (64 ppm) obtained for sediment from the shallow-water station (102 m) probably result from redox cycling at the socalled ‘Mn pump zone’ where scavenging-precipitation processes of Mn prevail. Chemical partitioning of the heavy metals revealed that Cu, Cr and Fe seem to be significantly bound to the detrital phases whereas carbonate phases tend to hold considerable amounts of Mn and Pb. The sequential extraction procedures used in this study also show that the metals Fe, Co, Ni, Cu, Zn and Pb associated with the ‘oxidizable phases’ are in far greater concentrations than the occurrences of these metals with detrital and carbonate phases. These results are in good agreement with the recent studies on suspended matter and thermodynamic calculations which have revealed that organic compounds and sulfides are the major metal carriers in the anoxic Black Sea basin, whereas Fe-Mn oxyhydroxides can also be important phases of other metals, especially at oxic sites. This study shows that, if used with a suitable combination of the various sequential extraction techniques, metal partitioning can provide important information on the varying geological sources and modes of occurrence and distribution of heavy metals in sediments, as well as, on the physical and chemical conditions prevailing in an anoxic marine environment.  相似文献   

9.
Nearshore waters to a depth of 200 m constitute only 0.2% of the volume of the world's oceans, but they receive and process 25% of the oceans' input of organic carbon, between 6 and 7 × 1015 g C per year. Man's activities during the past century have significantly increased both the supply of nutrients from land to coastal waters and the total sediment load carried by rivers and deposited in nearshore waters. The combination of increased primary productivity, due to increased supply of nutrients, and increased burial of organic matter, due to increased sedimentation, could sequester a significant fraction of the carbon released into the atmosphere by man as organic carbon in recent shallow-water sediments.  相似文献   

10.
To assess heavy metals in mangrove swamps of Sehat and Tarut coastal areas along the Arabian Gulf, 18 sediment samples were collected for Al, V, Cr, Mn, Cu, Zn, Cd, Pb, Hg, Sr, As, Fe, Co, and Ni analysis. The results indicated that the distribution of some metals was largely controlled by anthropogenic inputs, while others were of terrigenous origin and most strongly associated with distribution of aluminum and total organic carbon in sediments. Mangrove sediments were extremely severe enriched with Sr (EF?=?67.59) and very severe enriched with V, Hg, Cd, Cu, As (EF?=?44.28, 37.45, 35.77, 25.97, and 11.53, respectively). Average values of Sr, V, Hg, Cd, Cu, Ni, As, and Cr were mostly higher than the ones recorded from the Mediterranean Sea, the Red Sea, the Gulf of Aqaba, the Caspian Sea, the Arabian and Oman gulfs, coast of Tanzania, sediment quality guidelines, and the background shale and the earth crust. Landfilling due to coastal infrastructure development around mangrove forests, oil spills and petrochemical and desalination effluents from Al-Jubail industrial city to the north were the anthropogenic activities that further enhanced heavy metals in the studied mangrove sediments.  相似文献   

11.
受热带季风气候和周边陆源输入的影响,低纬泰国湾海—陆相互作用强烈,是研究海洋沉积有机碳与陆源输入、海洋初级生产力等气候环境变化响应关系的理想区域.通过对泰国湾泥质区T43柱样中总有机碳(TOC)、总氮(TN)、稳定碳同位素(δ13C)以及粒度等指标的分析,基于210Pb建立的高分辨年代地层框架,重建了该区百年来有机碳的...  相似文献   

12.
Heavy metals were investigated in the sediments of the Ventspils Harbour located in north-west Latvia (eastern Baltic Sea). Sediment samples were analysed for major and trace metals by ICP-AES, supplemented by inorganic and organic carbon as well as grain-size distributions. Principal component analysis of the data resulted in two main parameter clusters associated with Ca- and Al-rich material and indicated differing behaviour of Pb, Cu, Zn, N and P. Normalization with respect to Ca and Al by least absolute values regression removed the spatial pattern of sediment metal content in the harbour. High residual concentrations at individual sites were associated with local contaminations, whereas the overall concentration pattern was governed by the transport of riverine fine material. Dilution with coarser, quartz-rich marine sediments led to a pronounced heavy metal concentration drop towards the harbour gates. High mixing was an important feature of sediment dynamics in the Ventspils Harbour, hampering contaminant source identification and sediment monitoring.  相似文献   

13.
Numerous studies of marine environments show that dissolved organic carbon (DOC) concentrations in sediments are typically tenfold higher than in the overlying water. Large concentration gradients near the sediment–water interface suggest that there may be a significant flux of organic carbon from sediments to the water column. Furthermore, accumulation of DOC in the porewater may influence the burial and preservation of organic matter by promoting geopolymerization and/or adsorption reactions. We measured DOC concentration profiles (for porewater collected by centrifugation and “sipping”) and benthic fluxes (with in situ and shipboard chambers) at two sites on the North Carolina continental slope to better understand the controls on porewater DOC concentrations and quantify sediment–water exchange rates. We also measured a suite of sediment properties (e.g., sediment accumulation and bioturbation rates, organic carbon content, and mineral surface area) that allow us to examine the relationship between porewater DOC concentrations and organic carbon preservation. Sediment depth-distributions of DOC from a downslope transect (300–1000 m water depth) follow a trend consistent with other porewater constituents (ΣCO2 and SO42−) and a tracer of modern, fine-grained sediment (fallout Pu), suggesting that DOC levels are regulated by organic matter remineralization. However, remineralization rates appear to be relatively uniform across the sediment transect. A simple diagenetic model illustrates that variations in DOC profiles at this site may be due to differences in the depth of the active remineralization zone, which in turn is largely controlled by the intensity of bioturbation. Comparison of porewater DOC concentrations, organic carbon burial efficiency, and organic matter sorption suggest that DOC levels are not a major factor in promoting organic matter preservation or loading on grain surfaces. The DOC benthic fluxes are difficult to detect, but suggest that only 2% of the dissolved organic carbon escapes remineralization in the sediments by transport across the sediment-water interface.  相似文献   

14.
《Chemical Geology》2002,182(2-4):377-394
Bulk heavy metal (Fe, Mn, Zn, Cu, Pb, Cd), Al, organic carbon and carbonate concentrations, grain sizes, and δC13 of the organic carbon distributions were studied in sediments collected throughout the East China Sea continental shelf and the Yangtze River Delta. The results demonstrated that terrigenous sediments from the Yangtze River is a dominating factor controlling the spatial variations of heavy metals and organic carbon concentrations on the East China Sea continental shelf. In addition, grain size and recent anthropogenic influences are also major factors modifying the spatial and vertical variations of heavy metals.Large spatial variations with a band type distribution of heavy metals, grain size, organic carbon and carbonate were observed. Higher concentrations of heavy metal and light δC13 of the organic carbon were found primarily in the Deltaic and inner shelf sediments. The band type distribution generally followed the coastline with little variations in the north–south direction. Away from the Delta and inner shelf (west–east direction), most heavy metal concentrations decreased rapidly with the exception of Cd where high concentrations of Cd were also found in the carbonate-rich shelf break sediments. Coarse-grained relict sediments and biogenic carbonate are two primary diluting agents for the fine-grained aluminosilicate sediments from the Yangtze River with high concentrations of heavy metals.Unusually high concentrations of Cu, Pb, and Cd showed both spatially and vertically that more pollution prevention measures are needed in the Yangtze River drainage basin in order to prevent further heavy metal pollution of the East China Sea inner continental shelf.  相似文献   

15.
Heavy metals (Cr, Cu, Zn, Cd, Pb, Hg, and As), grain-size, pH, Eh, and total organic material (TOM and TN) of 59 surficial sediments of mud area from the inner continental shelf of the East China Sea have been analyzed. The relations of the heavy metals to sediment composition, pH, reduction/oxidation conditions and total organic materials were evaluated with multivariate statistics analysis, and the hydrodynamic conditions such as coastal current and Taiwan warm current are the other important controlling factors to the distribution of heavy metals. Sediment enrichment factors and potential ecological hazard index ( E\textRI E_{\text{RI}} ) were used to assess the heavy metals accumulation; the results indicate that moderate contamination of most heavy metals is prevalent, and the contamination level in the estuary is rather high, which is mainly from anthropogenic source. Compared with other areas in China, the contaminant level of the study area is moderate.  相似文献   

16.
In comparison to similar low-sulfate coastal environments with anoxic-sulfidic sediments, the Achterwasser lagoon, which is part of the Oder estuary in the SW Baltic Sea, reveals unexpectedly high pyrite concentrations of up to 7.5 wt%. Pyrite occurs mainly as framboidal grains variable in size with diameters between 1 and 20 μm. Pyritization is not uniform down to the investigated sediment depth of 50 cm. The consumption of reactive-Fe is most efficient in the upper 20 cm of the sediment column, leading to degrees of pyritization (DOP) as high as 80 to 95%.Sediment accumulation in the Achterwasser takes place in high productivity waters. The content of organic carbon reaches values of up to 10 wt%, indicating that pyrite formation is not limited by the availability of organic matter. Although dissolved sulfate concentration is relatively low (<2 mmol/L) in the Achterwasser, the presence of H2S in the pore water suggests that sulfate is unlikely to limit pyrite authigenesis. The lack of free Fe(II) in the pore waters combined with the possibility of a very efficient transformation of Fe-monosulfides to pyrite near the sediment/water interface suggests that pyrite formation is rather controlled by (i) the availability of reactive-Fe, which limits the FeS formation, and by (ii) the availability of an oxidant, which limits the transformation of FeS into pyrite. The ultimate source for reactive-Fe is the river Oder, which provides a high portion of reactive-Fe (∼65% of the total-Fe) in the form of suspended particulate matter. The surficial sediments of the Achterwasser are reduced, but are subject to oxidation from the overlying water by resuspension. Oxidation of the sediments produces sulfur species with oxidation states intermediate between sulfide and sulfate (e.g., thiosulfate and polysulfides), which transform FeS to FeS2 at a significant rate. This process of FeS-recycling is suggested to be responsible for the formation of pyrite in high concentrations near the sediment surface, with DOP values between 80 and 95% even under low sulfate conditions.A postdepositional sulfidization takes place in the deeper part of the sediment column, at ∼22 cm depth, where the downward diffusion of H2S is balanced by the upward migration of Fe(II). The vertical fluctuation of the diffusion front intensifies the pyritization of sediments. We suggest that the processes described may occur preferentially in shallow water lagoons with average net-sedimentation rates close to zero. Such environments are prone to surficial sediment resuspension, initiating oxidation of Fe-sulfides near the sediment/water interface. Subsequent FeS2 formation as well as postdepositional sulfidization leads to a major pyrite spike at depth within the sediment profile.  相似文献   

17.
A novel temperature proxy, the tetraether index of lipids with 86 carbon atoms (TEX86), was applied to the suspended particulate organic matter (POM) and sediment core tops from eight sites in the southern North Sea in different seasons. The TEX86-derived temperatures in many samples did not correlate with mean annual sea surface temperature (SST), but were shifted toward winter SST, apparently because Crenarchaeota are more abundant and metabolically active during periods of low primary production. This indicates that TEX86-derived SST estimates do not necessarily reflect annual mean SST and may provide essential information about seasonal SST palaeoreconstruction. High TEX86-derived SSTs were measured in the water of the river Rhine and in the sediment core tops and seawater from several stations in the southern North Sea. These sites were all characterised by important input of organic matter from soil and peat, as revealed by the relatively high values obtained with the new terrestrial proxy, the branched and isoprenoid tetraether (BIT) index. These data demonstrate that to reconstruct palaeotemperatures it is essential to estimate both TEX86 and BIT indices to check that TEX86 temperatures are not biased as a result of large terrestrial input. Important seasonal variations in TEX86-derived SST were also evident for the surface sediments of several stations characterised by extremely low sedimentation rates, indicating temporary settlement of laterally transported organic matter with a warmer temperature signal. This implies that sediment core top correlations between TEX86 and mean annual SST should not be carried out in areas characterised by transient sediment deposition.  相似文献   

18.
北黄海沉积物中氮的地球化学特征及其早期成岩作用   总被引：15，自引：0，他引：15  
本文首次报道对北黄海沉积物中氮的形态及其早期成岩作用的研究成果。结果表明 ,北黄海沉积物中占主导地位的是细粒度组分 ,其结构和性质直接影响着沉积物中化学元素的形态、含量与分布 ,使自然粒度沉积物中各形态氮的垂向分布与细粒度组分中各形态氮的分布非常相近。在氮的早期成岩过程中 ,粒度也起着非常重要的作用 ,沉积物的粒度越细 ,沉积物中有机氮的分解速率越小 ,即细粒度沉积物中有机氮的分解矿化速率最小 ,易于富集有机氮。对于不同站位的沉积物来说 ,因其沉积速率的差异 ,致使沉积物中各形态氮的埋藏通量有很大差异 ,沉积速率越大 ,沉积物中各形态氮的埋藏通量越大 ,在沉积速率最大的 C4站位 ,各形态氮的埋藏通量最大。  相似文献   

19.
In this study the response of sedimentary phosphorus (P) burial to changes in primary productivity and bottom water oxygen concentrations during the Late Quaternary is investigated, using two sediment cores from the Arabian Sea, one recovered from the continental slope and the other from the deep basin. The average solid-phase P speciation in both cores is similar, authigenic and biogenic (fish debris) apatite make up the bulk of the P inventory (ca. 70%);whereas P adsorbed to iron oxides, organic P, and detrital apatite constitute minor fractions. Postdepositional redistribution has not significantly altered the downcore distribution of total solid-phase P. Phosphorus burial efficiencies are generally lower during periods of increased paleoproductivity. This is caused by (a) partial decoupling of the P export flux, consisting primarily of particulate organic P, and the P burial flux, consisting primarily of biogenic and authigenic apatite; and (b) the lack of increased rates of authigenic CFA formation during periods of higher P deposition. In addition, fluctuations in bottom water oxygen concentrations may have affected P burial in continental slope sediments. The results of this study indicate that higher primary productivity induces more efficient P cycling. On time scales exceeding the oceanic P residence time, this process may induce higher surface water productivity, thus creating a positive feedback loop. In the Arabian Sea, this feedback mechanism may have contributed to changes in sea surface productivity on sub-Milankovitch time scales because P, regenerated on the continental slopes of the Oman and Somalian coastal upwelling zones, is reintroduced into the photic zone relatively fast.  相似文献   

20.
为探讨渤海西部在多重环境因素变化下沉积物中重金属的环境地球化学行为,分析了渤海西部44个站位表层沉积物样品中8种重金属元素含量,研究了重金属元素的分布特征、环境影响因素及其生态风险。结果表明,渤海西部表层沉积物中As、Cu、Cd、Cr、Hg、Ni、Pb、Zn的平均含量分别为117 mg/kg、255 mg/kg、014 mg/kg、689 mg/kg、0037 mg/kg、303 mg/kg、223 mg/kg、757 mg/kg;Cu、Cr、Ni、Zn含量与有机碳含量、小于63 μm细粒沉积物呈显著正相关,其在表层沉积物中的分布明显受到有机质含量和沉积物粒径的控制,而As、Hg分布没有明显受到有机质含量的影响。富集系数显示,Cr、Ni、Pb和Zn为无富集,Cu、As为轻度富集,Cd和Hg为中度富集。与多种背景值和一致性沉积物质量基准相比较,渤海西部表层沉积物Pb、Cd的含量超出背景值,而Cu、Zn、Ni、Cr、As、Hg含量也存在一定的异常,但其含量水平引发有害生物效应的可能性不大,尽管重金属元素含量偏高,但生态风险较小。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号