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1.
The organic horizon (the mor layer) of podzolized boreal forest soils has accumulated atmospheric fallout of mercury and lead over centuries, resulting in current concentrations close to levels where negative effects on soil biota are thought to occur. To what extent the pollution history is preserved in the stratigraphy of this horizon is not well known. In this study we asses whether the chronology of a large historic pulse of atmospheric pollution emitted from the Rönnskär smelter in northern Sweden, particularly between 1950 and 1980, is preserved within the stratigraphy of the mor layer, which is typically 5-cm thick. Vertical sub-sampling (?5 mm) of five mor profiles sampled along a 100-km pollution gradient away from the smelter are analyzed for mercury and lead concentrations, spheroidal carbonaceous particles from fossil fuel combustion (SCPs) and stable lead isotopes (206Pb/207Pb and 208Pb/207Pb). Their vertical distribution is compared with the temporal variations in atmospheric inputs reconstructed for the last ∼100 years from analyses of an ombrotrophic peat core and a varved lake sediment core sampled within a distance of 50 km of the smelter. The mor profiles situated ?12 km from the smelter record the pollution history of the smelter. There is a 20 to 40-times enrichment of Hg, Pb and SCP at the transition in the O-horizon from the F- to H-layer compared to the basal part and a distinct peak in the 206Pb/207Pb ratio (∼1.22) in the F-layer. The mor profiles situated outside the historical contamination range of the smelter (80 and 100 km away) record no obvious influence from the Rönnskär smelter, instead their vertical 206Pb/207Pb profiles follow the general regional pollution history in northern Sweden. We conclude that the mor layer preserves a record of atmospheric Hg, Pb and SCP inputs and due to low leaching rates this organic horizon serves as a semi-archive of atmospheric Hg and Pb pollution. We stress the need of including this property in the existing ‘black-box’ models predicting the fate of Hg and Pb within contaminated boreal forest soils.  相似文献   

2.
A sediment core collected from coastal zone near the Qiao Island in the Pearl River Estuary was analyzed for total metal concentrations, chemical partitioning, and physico-chemical properties. Three vertical distribution patterns of the heavy metals in the sediment core were identified, respectively. The dominant binding phases for Cu, Pb, Cr, and Zn were the residual and Fe/Mn oxides fractions. Cd in all sediments was mainly associated with exchangeable fraction. Influences of total organic carbon content and cation exchange capacity on the total concentrations and fractions of almost all the metals were not evident, whereas sand content might play an important role in the distributions of residual phases of Cr, Cu, Pb, and Zn. In addition, sediment pH had also an important influence on the Fe/Mn oxides, organic/sulfide and residual fractions of Cr, Cu, and Zn. Contamination assessment on the heavy metals in the sediment core adopting Index of Geoaccumulation showed that Cr, V, Be, Se, Sn, and Tl were unpolluted, while Cu, Ni, Pb, Zn, Cd, and Co were polluted in different degrees throughout the core. It was remarkable that the various pollution levels of the metals from moderate (for Cu, Pb, and Zn) to strong (for Cd) were observed in the top 45 cm of the profiles. The relative decrease of the residual fraction in the upper 45 cm of the core is striking, especially for Zn and Cu, and, also for Pb, and Cr. The change in fraction distribution in the upper 45 cm, which is very much contrasting to the one at larger depths, confirms that the residual fraction is related to the natural origin of these metals, whereas in the upper part, the non-residual fractions (mainly the Fe/Mn oxides fraction) are increased due to pollution in the last decade. The possible sources for Cu, Pb, Zn, and Cd contaminations were attributed to the increasing municipal and industrial wastewater discharges, agricultural runoff, atmospheric inputs, and runoff from upstream mining or smelting activities, which may be associated with an accelerating growth of economy in the Pearl River Delta region in the past decade.  相似文献   

3.
We measured the vertical distributions of Mo, Fe, Mn, sulfide, sulfate, organic carbon, major ions, and pH in sediment porewater from one perennially oxic and three seasonally anoxic lacustrine basins in Eastern Canada, as well as those of Mo, acid volatile sulfide, Fe, Mn, Al, organic C, 210Pb and 137Cs in sediment cores from the same sites. The only input of anthropogenic Mo to these lakes comes from atmospheric deposition.The relatively monotonous distribution of Mo in the porewater of three seasonally anoxic basins suggests that Mo is not redistributed in the sedimentary column during periods of anoxia. In contrast, porewater Mo profiles obtained at three sampling dates in a perennially oxic basin display sharp Mo peaks below the sediment-water interface, indicating redistribution subsequent to deposition. Modeling of these latter porewater Mo profiles with a diagenetic reaction-transport equation coupled to comparisons among the various porewater and solid phase profiles reveal that Mo is released at 1-2 cm depth as a consequence of the reductive dissolution of Fe oxyhydroxides and scavenged both at the vicinity of the sediment-water interface, by re-adsorption onto authigenic Fe oxyhydroxides, and deeper in the sediments where dissolved sulfide concentrations are higher. The estimated rate constant for the adsorption of Mo onto Fe oxyhydroxides is 36 ± 45 cm3 mol−1 s−1.Diagenetic modeling indicates that authigenic Mo in sediments of the perennially oxic basin represents about one-third of the total solid phase Mo in the first cm below the sediment-water interface and only one tenth below this horizon. If we assume that no authigenic Mo is accumulated in the seasonally anoxic lake sediments we conclude that the sediment Mo concentrations, which are up to 3-16 times higher than the average lithogenic composition, depending on the lake, are mainly due to atmospheric deposition of anthropogenic Mo and not to the formation of authigenic Mo phases. Reconstructed historical records of the atmospheric Mo deposition indicate maximum values in the 1970s and 1980s and significant decreases since then. Emissions to the atmosphere associated with the smelting of non-ferrous ores and coal combustion appear to be the most important sources of anthropogenic Mo.  相似文献   

4.
Many small estuaries are influenced by flow restrictions resulting from transportation rights-of-way and other causes. The biogeochemical functioning and history of such systems can be evaluated through study of their sediments. Ten long and six short cores were collected from the length of Jordan Cove, Connecticut, a Long Island Sound subestuary, and analyzed for stratigraphy, radionuclides (14C, 210Pb, 226Ra, 137Cs, and 60Co), and metals (Ag, Cd, Cu, Pb, Zn, Fe, and Al). For at least 3,800 yr, rising sea level has gradually inundated Jordan Cove, filling it with mud similar to that currently being deposited there. Long-term sediment accumulation in the cove averaged close to 0.1 cm yr−1 over the last three millennia. Recent sediment accumulation rates decrease inland from 0.84 cm yr−1 to 0.40 cm yr−1, and are slightly faster than relative sea-level rise at this site (0.3 cm yr−1). Similarity of depth distributions of trace metals was used to confirm relative sediment accumulation rates. 60Co and Ag are derived from sources outside the cove and its watershed, presumably the Millstone nuclear power plant and regional contaminated sediments, respectively. The combined data suggest that Long Island Sound is an important source of sediment to the cove; a minor part of total sediment is supplied from the local watershed. Trace metal levels are strongly correlated with Fe but not with either organic matter or Al. Sediment quality has declined in the cove over the past 60 yr, but only slightly. Cu, Pb, and Zn data correlate strongly with Fe but not with either organic matter or aluminum. Ratios of Ag to Fe and to trace metals suggest that Ag in the cove is derived almost entirely from Long Island Sound. This result supports the notion that Fenormalized Ag can serve as a better tracer of some kinds of contamination than more common and abundant metals, like Cu, Pb, and Zn. *** DIRECT SUPPORT *** A01BY085 00008  相似文献   

5.
The study area is situated in a large agricultural field which produces tobacco, maize, and other yearly cultivated vegetables in Tekkeköy, Samsun (NE-Turkey). In addition, a significant part of this area to the north along the Black Sea coast is occupied by several industrial plants such as a copper smelting plant (KB?), a fertilizer plant (Tügsa?) and industrial park facilities (IPF). In order to reveal their environmental impacts, heavy metal analyses were conducted on soil, plant leaves and water samples collected within an area of approximately 30 km2 around these plants. Soil samples within an area of 10 km2 around these facilities are found to be highly polluted with Cu, Zn, Pb, Fe and Mn. Pollution occurs at surface and sharply dies out at 20 cm downwards in soil profile. Since the region is polluted mostly with base metals, the copper smelting factory appears to be the main source of pollution as it processes the massive sulfidic ores of the Black Sea area. Plants show Cu, Pb, Zn and Fe pollution around KB? and Tügsa? and Cu and Pb around IPF. Pollutants observed in tobacco (Nicotiana tobacum) are Cu, Pb, Zn, Fe and S; in maize (Zea mays) Cu, Zn and Fe; and in cabbage (Brassica oleracea) Cu, Pb, Fe and S. The analyses of water samples collected from the study area reveal that Pb and, to a lesser degree, Cu and Fe pollution stem from KB?; Cu, Fe and Mn pollution from Tügsa?; Pb and minor amounts of Fe and Mn pollution from IPF. Factor analyses from analyzed metals and anionic complexes in water show three distinct groups: (a) an association of heavy metals with Na, K and Mg referring to pollution and acid leaching of soil, (b) an association of NH4, Fe, SO4, Cl and Br indicating agricultural pollution and sea-water invasion in land near the shore line, and (c) HCO3 behaving in a different manner in heavy metal precipitation.  相似文献   

6.
The distribution of metals with depth in sediment cores sampled from industrialized estuaries can reveal long-term trends in loadings to the waterbody. Salt marsh cores were sampled from five locations from the head to the mouth of Narragansett Bay and from one location from a marsh inside a lagoon on the coast of Block Island Sound with the intent of reconstructing historical loadings of Pb, Cu, and Zn to this estuary. Concentrations of Fe and Mn were measured as indicators of redox conditions of the sediment column. Chronologies were developed using accretion rates determined previsly from210Pb analyses of the same cores. Excess metal inventories and enrichment over pre-industrial concentrations were greater in upper bay cores reflecting the location of sources at the head of the estuary. The bay cores were similar with respect to the distributions of Cu, Pb, and Zn. Concentrations of all metals began to increase over background levels at depths corredponding approximately to the year 1900. Most of the cores showed peak concentrations of Cu and Pb in the early 1950s and 1970s. Distributions of Zn were more variable among cores, showing peaks in the early 1920s in some cores and in the 1950s and 1970s in others. In general, the observed distributions in the bay cores are consistent with estimated long-term trends in loadings from atmospheric and sewage sources. The metal distributions in the lagoon core appear to reflect atmospheric loadings. However, there are features in some cores that are not explainable using the estimated trends in source inputs. There also is not a 1∶1 correspondence between changes in sediment metal concentrations and changes in loadings. It is likely that this method of reconstruction would benefit from a more detailed characterization of sources, but comparison of sediment and historical records do show that attempts to reduce loadings to the bay have been successful.  相似文献   

7.
A record of the impacts of major hurricanes on sediment stratigraphy and composition in subtropical ecosystems has been preserved in the lower Everglades and Florida Bay. These impacts were observed in discontinuous layers of sediment that were identified from high-resolution, vertical profiles of excess 210Pb and 137Cs. Discontinuities were found at different geographic locations and at two to three different depths in the sediment column; however, the layers were each deposited within time periods that corresponded with the passing of category 3–5 hurricanes during 1960, 1948 and 1935. A simple mass balance model for excess 210Pb was used to show net changes of ±20–100% in excess 210Pb inventory that resulted from sediment disturbances of <1 to >22 cm. Abrupt shifts in sediment composition were often observed in hurricane-impacted layers. Ratios of organic (C/P) were four- to fivefold higher than normal in post-hurricane layers of sediment at open bay sites. These layers are phosphorus poor and seem to reflect preferential decomposition of organic P relative to organic C in association with hurricanes. The net effect is for major hurricanes to redistribute sediment, organic matter and nutrients.This revised version was published online in July 2003.  相似文献   

8.
The technique of diffusive gradients in thin films (DGT) was applied to obtain high-resolution vertical profiles of trace metals in sediment porewater of a eutrophic lake, Lake Chaohu. All sampling sediments were under anaerobic conditions with Eh values below 0, the redox potential profile in M4 was relatively stable, and higher Eh values in M4 than that in M1 were observed due to hydrodynamic effects. Fe, Mn and As exhibited closely corresponding profiles due to the co-release of Fe and Mn oxides and the reduction of As. Higher Fe and Mn concentrations and lower As concentrations were observed in M1 of the western half-lake than those in M4 of the eastern half-lake due to different sources and metal contamination levels in the two regions. Cu and Zn showed increasing concentrations similar to Mn and Fe at 1–2 cm depth of sediments, while DGT measured Co, Ni, Cd and Pb concentrations decreased down to 3–4 cm in the profiles. Co, Ni, Cu, Zn, Cd and Pb showed insignificant regional concentration variances in the western and eastern half-lakes. According to the R(C DGT/C centrifugation) values, the rank order of metal labilities decrease as follows: Fe (>1) > Cu, Pb, Zn (>0.9) > Co, Ni, Cd (>0.3) > Mn, As (>0.1).  相似文献   

9.
The geochemical partitioning of ten elements in stratified Holocene sediments from Loch Dee, southwest Scotland, has been established by use of a five-stage sequential extraction procedure. Samples from below 15 cm sediment depth show minimal evidence of modification by anthropogenic contamination or active diagenesis and hold Fe, Mg, Cu, Cd, Co, Pb, and Ni primarily in detrital silicates or organic complexes, while Mn, Ca, and Zn reside largely in adsorbed and reducible oxide phases. In the uppermost ca 15 cm of sediment, enhanced total concentrations of Zn, Cu, and Pb reflect increased atmospheric deposition during the postindustrial period. Of these metals, only Pb displays any notable adjustment of partitioning in the enriched zone, showing disproportionate accumulation in labile oxides and organic-Pb phases. The lack of Pb and Zn carbonates in the contaminated horizon may reflect inherent thermodynamic instability under the acid surface and pore-water conditions of Loch Dee. Increments to total Mn and Co in the surficial ca 5 cm of sediment are attributable to the accumulation of secondary oxides and adsorbed species, consistent with precipitation from the interstitial pore-waters across a sedimentary redox front. The presence of metals such as Zn and Cd in soluble or acid-volatile phases in the interfacial sediment has implications for the future management of the Loch Dee basin, with leaching into the overlying waters likely, given the continuation of current trends of lake acidification.  相似文献   

10.
The results of investigations (SEM/EDS and AAS) of a peat deposit, spanning 13,000 years of peat accumulation, are shown. The peat deposit is located in a region of shallow occurrence of Zn–Pb ores, near Tarnowskie Góry town, within the Cracow–Silesia district (southern Poland). Exploitation of lead, silver and iron during the medieval times (Twelfth and thirteenth century) was confirmed by historical documents whereas there are no unambiguous data showing that there was metal mining during the Romanian or earlier times in the region. The peat deposit is located within the influence of atmospheric Pb and Zn emission from a nearby Zn–Pb smelter. Two vertical peat profiles were investigated (120 and 140 cm depth of profile) showing variable concentrations of Zn up to 713 mg kg?1, Pb up to 317 mg kg?1, Cd up to 13 mg kg?1 and Tl up to 31 mg kg?1. The highest concentrations were recorded for the uppermost peat layers. SEM and EDS investigations revealed the occurrence of metalbearing, submicroscopic mineral components: Fe, Mn, Ti and Zn oxides and Zn and Pb carbonates. The top layer of the deposit contained Zn, Pb and Cd sulphides. The occurrence of aggregates of Au–Ag, Cu–Zn and Au–Ag–Cu alloys can be possibly related to pre-historical mining and smelting or be explained by geochemical transformations. The preservation of carbonates and oxides in the peat is discussed, indicating a generally neutral to alkaline peat water chemistry and maintenance of an oxidized environment in the fen.  相似文献   

11.
长江中游网湖沉积物重金属元素变化特征分析   总被引：12，自引：8，他引：4       下载免费PDF全文
在放射性核素137Cs和210Pb精确计年的基础上,建立了长江中游网湖近代沉积物年代序列。通过对沉积物中金属元素含量和粒度的测定,结合相关的文献资料,分析了100多年来网湖沉积物中重金属元素的垂直分布特征、物源变化,以及自然因素和人类活动对其的影响,最后采用地累积指数法和潜在生态危害指数法进行了重金属污染评价。研究结果表明：  20世纪50年代以前,人类活动对重金属元素沉积影响不大,重金属元素含量低于或接近参考的背景值,主要表现为自然沉积。其中1920～1950年间,流域高频率的洪灾使网湖沉积物中粘土物质减少,战乱和血吸虫病造成阳新县工农业生产衰退,人口急剧下降,受此影响沉积物中重金属含量出现了一段低谷。50年代以后,随着人口的增长、经济的速猛发展,尤其是矿产开发和大规模的水利工程建设,流域水土流失加重,大量陆源物质进入湖泊,使Cu,Ti,Mn,Zn,Co,Fe和Pb含量增加。重金属污染评价结果表明：  100多年来网湖总体上污染较轻,主要污染元素为Pb;   Cu和Zn在60年代后出现轻度污染;   Mn在沉积物表层出现轻度污染。目前,网湖RI=40.83,生态风险较小,但作为水生生物的养殖基地,中国重要的湿地保护区,其重金属污染问题应引起有关方面的关注,以防患于未然。  相似文献   

12.
Contents and δ34S values of several S compounds, enumerations of S-reducing bacteria (SRB) and Fe-reducing bacteria (IRB), and Fe, Pb and In concentrations were determined for 210Pb-dated sediment cores from two lakes in Quebec, Canada. Both lakes are located approximately 70 km downwind of the Horne smelter and refinery in Rouyn-Noranda. Increases in Fe, Pb and In concentrations and a decrease in the δ34S values of total S in both lake sediment cores coincide with the start-up of the smelter in 1927. The shift towards more negative δ34S values was primarily caused by an increase in the extent of S isotope fractionation during bacterial (dissimilatory) SO4 reduction due to SO4 loading of the lakes after smelting began. Consequently, an enhanced accumulation of 32S-enriched reduced inorganic S compounds is evident in the sediments. δ34S values of organic S in the sediments decreased only slightly due to the smelter emissions between 1930 and 1980. Hence, due to the sulfide depositing mechanisms, S isotope ratios constitute a useful tracer recording the onset of S pollution in sediments of the two previously SO4-limited lakes investigated. In contrast, total S concentrations alone are not reliable indicators for anthropogenic S loading in lake sediment records.  相似文献   

13.
A detailed geochemical and microbiological study of a ∼2 m sediment core from the inactive Alvin mounds within the TAG hydrothermal field was conducted to examine, for the first time, the role of prokaryotes in subsurface weathering of hydrothermal sediments. Results show that there has been substantial post-depositional remobilisation of metal species and diagenetic overprinting of the original high-temperature hydrothermal minerals, and aspects have involved prokaryotic processes. Prokaryotic enumeration demonstrates the presence of a population smaller than the average for deep sea sediments, probably due to the low organic carbon content, but not inhibited by (and hence adapted to) the metal rich environment. There was a small but significant increase in population size associated with the active redox boundary in an upper metal sulphide layer (50-70 cm) around which active metal remobilisation was concentrated (Cu, Au, Cd, Ag, U, Zn and Zn). Hence, subsurface prokaryotes were potentially obtaining energy from metal metabolism in this near surface zone. Close association of numbers of culturable Mn and Fe reducing prokaryotes with subsurface Fe2+ and Mn2+ pore water profiles suggested active prokaryotic metal reduction at depth in core CD102/43 (to ∼175 cm). In addition, a prokaryotic mechanism, which is associated with bacterial sulphate reduction, is invoked to explain the U enrichment on pyrite surfaces and Zn and Pb remobilisation in the upper sediment. Although prokaryotic populations are present throughout this metalliferous sediment, thermodynamic calculations indicated that the inferred low pH of pore waters and the suboxic/anoxic conditions limits the potential energy available from Fe(II) oxidation, which may restrict prokaryotic chemolithotrophic biomass. This suggests that intense prokaryotic Fe oxidation and weathering of seafloor massive sulphide deposits may be restricted to the upper portion of the deposit that is influenced by near neutral pH and oxic seawater unless there is significant subsurface fluid flow.  相似文献   

14.
 Long sediment cores (>1 m) were collected from eight Precambrian Shield lakes in southern Ontario, Canada and analyzed for mercury (Hg), loss-on-ignition (LOI), and a suite of 36 other elements. Results indicated at least 100-fold variation in sediment Hg concentrations between lakes in close proximity (from 450 ppb), comparable to the variation reported for lakes across the whole of Canada. Strong areal correlations between Hg concentrations and LOI (r 2 =0.77), between Hg and other trace element concentrations (Pb, Zn, Cd, Sb, As, Br), and similarities in the vertical concentration profiles of Hg and LOI, all point to the importance of organic matter in the release, transport and redistribution of metals in watershed systems. The spatial pattern of Hg concentrations in deep, precolonial sediments (>20 cm) was found to mirror the pattern of Hg concentrations in modern surface sediments, an observation that was confirmed in a follow-up survey (r 2 =0.85;n=25 lakes), indicating that natural processes govern the unequal distribution of Hg among these lakes. Between-lake differences in surface sediment Hg concentrations normalized to organic carbon (Hg/C) were also reflected by Hg concentrations in smallmouth bass normalized to 35 cm length (R 2 =0.63;n=15 lakes). The latter relationship suggests that smallmouth bass and lake sediment indicators provide mutually supportive information regarding Hg loading to the lacustrine environment from geological sources in the watershed system. Received: 31 October 1996 · Accepted: 27 May 1997  相似文献   

15.
Multiple sediment cores were collected in June 1994 in the turbidity maximum zone of the Hudson River estuary off Manhattan, New York. Results from X-radiography of the sediments and measurements of natural radionuclides (234Th,7Be, and210Pb) and trace metals (Ag, Cd, Cu, Pb, and Zn) show significant spatial variability of sediment composition and structure and patchy distributions of radionuclides activities and trace metal concentrations in this small area (0.6 km × 0.5 km). Radionuclide and trace metal analyses confirm prior work (Olsen et al. 1978; Olsen et al. 1981; Hirschberg et al. 1996) that show the western margin area of the river acts as a repository of these chemical constituents at least for the short-term period (0.5–1 yr), and the mid-channel area is not a depositional area for sediments and associated chemical constituents.7Be profiles reveal short-term sediment deposition rates ranging from 6 cm yr?1 to 26 cm yr?1 in the western margin area. Significant spatial variations in excess234Th and7Be inventories (up to a factor of 10 and 5 for234Th and7Be, respectively) are found in the western margin depositional area, although the inventories are balanced, on average, with in situ production in water column and atmospheric supply. The spatial variation of surficial excess210Pb and trace metal concentrations in depositional areas of the western margin are ≤10% for Ag, Cu, Pb, and Zn and 29% for Cd. However, the variations in the transition zone range from 28% to 93%. This variability is likely related to variations in tidal current velocity, bottom shear stress, and river channel morphology.  相似文献   

16.
The spatial distributions of contaminant metals (Hg, Pb, Zn, Cd, Cu) and a metalloid (As) in vegetable plots and paddy fields located near a large scale Pb/Zn smelter in Hunan province, China, were investigated. Soil located 4 km from the smelter was severely contaminated, with maximum concentrations of Hg, Pb, Zn, Cd, Cu and As as high as 2.89, 1200, 3350, 41.1, 157 and 93 mg kg−1, respectively. Concentrations of soil metal and As decreased with distance in the dominant wind direction. Single-factor assessment indicated pollution levels of Hg, Pb, Zn and Cd were most severe, while pollution levels for Cu and As were less severe. Results from a potential ecological risk assessment indicated high risk associated with the soil within a 4 km radius, with the contribution for each contaminant calculated as follows: Cd (70.0%), Hg (19.4%), Pb (4.8%), As (3.0%), Cu (1.7%) and Zn (1.1%). The forest soil in the nearby city park was also affected by the atmospheric depositions from smelting activities. Soil profiles demonstrated the pollutants were mostly accumulated in the upper 20 cm layer. Contamination of the topsoil with Hg, Pb, Zn, Cd, Cu and As indicated remediation should be considered.  相似文献   

17.
The 150-year historical changes in concentrations of pollution elements (Pb, Cu and Zn) in sediment profiles from two riparian freshwater wetlands along the Wusuli River (boundary river between China and Russia) were studied, and the ecological risk of heavy metals and their effects on four riparian wetlands during the urban development from Khanka Lake to Black Bear Island along the Wusuli River were assessed. Results showed that there are sharp increases of the enrichment factor and the ratio of anthropogenic/total of heavy metals in the sediment profiles during the 2000s, which showed that intensive human activities during city development had greatly affected heavy metals distribution since the 1960s. According to the principal component analysis, sediment textures, redox regimes, and organic matter contents accounted for 45.7, 23.6 and 16.5 % of the total variance of element concentrations, respectively. This study also showed that ecological risk of heavy metals was increased along the Wusuli River and closely related to the water quality of the rivers as their hydrological regimes likely affect wetlands.  相似文献   

18.
A study of the water and sediment chemistry of the Nainital, Bhimtal, Naukuchiyatal and Sattal Lakes of Kumaun, has shown that the water of these lakes are alkaline and that electrical conductivity, total dissolved solid and bicarbonate HCO 3 − are much higher in Nainital than in the other three lakes. The weathering of limestone lithology and anthropogenic pollution, the latter due to the very high density of population in the Nainital valley, are the primary sources of enhanced parameters. The low pH of Nainital Lake water is due to low photosynthesis and enhanced respiration, increasing CO2 in the water and the consequent enhancement of Ca2+ and HCO 3 − . The dissolved oxygen in Nainital Lake is less compared to other lakes, indicating anoxic conditions developing at the mud–water interface at depth. The PO 4 3− content in Nainital is higher (124 μg/l), showing an increasing trend over time leading to eutrophic conditions. The trace metals (Cu, Co, Zn, Ni, Mn, and Sr) are present in greater amounts in the water of Nainital Lake than in the other three lakes, though Fe and Cr are high in Bhimtal and Fe in Naukuchiyatal. The higher abundance is derived from the leaching of Fe–Mg from metavolcanic and metabasic rocks. Most of the heavy metals (Cr, Ni, Cu, Mn, Fe, Sr, and Zn) significantly enrich the suspended sediments of the lakes compared to the bed sediments which due to their adsorption on finer particles and owing to multiple hydroxide coating and organic content, except for Fe, which is enriched in the bed sediments. The high rate of sedimentation, 11.5 mm/year in Nainital, compared to Bhimtal with 4.70 mm/year, Naukuchiyatal with 3.72 mm/year, and Sattal with 2.99 mm/year, has resulted in shorter residence time, poor sorting of grains, and lesser adsorption of heavy metals, leading consequently, their depletion in the bed sediments of Nainital Lake.  相似文献   

19.
In most mining areas, significant concentrations of metals such as Pb, Cu, Cr, Zn, Cd, Fe, Mn, Co, Ni, Hg, Ar, halogenated organic compounds and radionuclides are found. Of those, Cr is one of the well-known heavy metals that forms toxic species. It is necessary to study the mobilization and accumulation of Cr at the sediment water interface in an electric field at varying different positions and conditions of the electrode arrangement. The tests were carried out with a natural sediment containing heavy metals from the river Weisse Elster (Germany). The electrokinetic experiments have been performed in columns filled with sediment using electrodes made of conductive polymers (polyethylene with carbon black) at a maximum current density of 0.5 mA/cm2. The experimental results suggest that the mobilization and accumulation of Cr highly depends on chemical factors for e.g., pH value, redox potential, respectively redox status and the content of Fe, A1 and organic matter in the soil or sediment. The sorption of Cr (III, VI) is very high in the pH range > 4.5. As expected, a high mobilization of Cr (III, VI) was seen in the case of the experiments with the anode at the sediment, because the pH value was lower than mentioned above. On the opposite, the best conditions for the Cr (III, VI) immobilization is high pH values (cathode at the sediment).  相似文献   

20.
Sediments from San Antonio Bay, the northwest Gulf of Mexico, and the Mississippi River Delta were acid leached and analyzed for Fe, Mn, Pb, Zn, Cd, Cu and Ni by atomic absorption spectrophotometry. In order to account for differences in sediment clay, carbonate, and organic matter content, metal concentrations were normalized to Fe. Significant linear correlations of metals to Fe were obtained for unpolluted sediments and deviations from these “natural” statistical populations were found for areas thought to have metal input caused by man. San Antonio Bay sediments show little evidence of metal pollution despite 70 years of shell dredging in the bay. However, the San Antonio-Guadalupe River system, the bay's prime sediment source, has 10% to 50% higher than natural levels of Pb, Cd and Cu. Sediments from a 1500 km2 area of the Mississippi River Delta have Pb and Cd concentrations 10% to 100% higher than expected levels. The vertical distribution of Pb and Cd in these sediments suggests that inputs have occurred during the past 30 to 40 years. We find no indication of metal pollution in other areas of the Delta or along the continental shelf of the northwest Gulf of Mexico.  相似文献   

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