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1.
Lacey  E. M.  King  J. W.  Quinn  J. G.  Mecray  E. L.  Appleby  P. G.  Hunt  A. S. 《Water, air, and soil pollution》2001,126(1-2):97-120
Surface samples and cores were collected in 1993 fromthe Burlington Harbor region of Lake Champlain. Sediment samples were analyzed for trace metals(cadmium, copper, lead, nickel, silver and zinc),simultaneously extracted metal/acid volatile sulfide(SEM-AVS), grain size, nutrients (carbon and nitrogen)and organic contaminants (polycyclic aromatichydrocarbons (PAHs) and polychlorinated biphenyls(PCBs)). The concentrations of cadmium, copper,silver and zinc from the partial sediment digestion ofthe surface samples correlated well with each other(r 2>0.60) indicating that either a commonprocess, or group of processes determined the sedimentconcentrations of these metals. In an analysis of thespatial distribution of the trace metals and PAHs,high surficial concentrations were present in thesouthern portion of the Harbor. The trace metal trendwas strengthened when the concentrations werenormalized by grain size. A sewage treatment plantoutfall discharge was present in the southeasternportion of the Harbor at the time of this study and isthe major source of trace metal and PAH contamination. Evaluation of sediment cores provides a proxy recordof historical trace metal and organic inputs. Thepeak accumulation rate for copper, cadmium, lead, andzinc was in the late 1960s and the peak silveraccumulation rate was later. The greatestaccumulation of trace metals occurred in the late1960s after discharges from the STP began. Subsequentdeclines in trace metal concentrations may beattributed to increased water and air regulations. The potential toxicity of trace metals and organiccontaminants was predicted by comparing contaminantconcentrations to benchmark concentrations andpotential trace metal bioavailability was predictedwith SEM-AVS results. Surface sample results indicate lead,silver, ΣPAHs and ΣPCBs are potentially toxicand/or bioavailable. These predictions were supportedby studies of biota in the Burlington Harborwatershed. There is a clear trend of decreasing PAHand trace metal contaminant concentrations withdistance from the STP outfall.  相似文献   

2.
Grain size is the most basic of classification criteria for sediments. The size distribution of a given sediment records the physical transport processes involved in its formation. By using precise grain size analysis and the model of Kranck et al. (1996a,b), it is possible to break down a sediment into the three major components from which it was formed: material deposited as flocs, material deposited as single grains from suspension, and material carried under higher energy conditions. With this method, both the amount of material deposited in a flocculated state and the maximum size, or floc limit, of the particles composing the floc can be determined. Changes in floc limit indicate changes in the aggregation dynamics of the system. As most trace metals and many other contaminants associate closely with the fine particle fraction of sediments, it is important to determine both the areal distribution and reworking history of the floc settled portion of a sediment. This paper discusses the application of the method to coastal inlets in Atlantic Canada and examines the relationship between proportion of floc-settled material and trace metal concentrations. Disaggregated inorganic grain size distributions are also used to illustrate changes in the aggregation dynamics in areas of intense aquaculture.  相似文献   

3.
The vertical distribution of Hg in sediment cores from a range of hard- and soft-water lakes in Wisconsin was evaluated in terms of potential sources of Hg during the nineteenth and twentieth centuries. For the Madison lakes, the trends in Hg distribution were related to variations in sewage inputs during the last 80 yr. It is unlikely that either inputs of sewage or erosional products are responsible for the observed accumulation of Hg in the most recent sediments from three lakes in northeastern Wisconsin. Background levels varied from 0.01 to 0.24 ppm of Hg (intact sediment basis) in precultural sediments from the Wisconsin lakes investigated. There was no consistent relationship between the concentration of Hg and other sediment components of potential importance in the retention of Hg.  相似文献   

4.
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   

5.
Sediment profiles from ten excessively limed lakes were used to study the occurrence of lime residues as a result of incomplete lime dissolution and the influence of treatment with very high lime doses on the sequestration of metals in lake sediments. The sediment profiles were subjected to multi-element analysis and compared to sediment profiles from previous studies of lakes limed with normal lime doses and untreated reference lakes. The high lime doses were found to result in large lime residues in the sediment, with lime concentrations of up to 70% of the dry sediment in the studied lakes. Excessive liming, like liming with normal doses, was found to cause increased sequestration in sediments of, e.g. Cd, Co, Ni and Zn, metals where the mobility is known to be highly pH dependent, compared to non-limed reference lakes. No effect of liming on the sequestration of Cu, Cr, Pb and V could be shown. The size of the lime dose did not seem to influence the metal sequestration in the sediment, since no difference between the excessively limed lakes and lakes limed with normal doses was found. On the contrary, the large lime residues were found to cause a dilution of the metal concentrations in the sediments, since lime products used for lake liming generally have lower metal concentrations compared to the sediments.  相似文献   

6.
An overlapped paleosol (albic Paleudalf) in North Huai region was studied by means of sand and clay mineralogy, elemental geochemistry, particle size distribution, observation of quartz sand surface structure under SEM, micromorphology, pollen analysis as well as soil dating. These albic soils are very extensive on uplands in this region and the profiles have developed on two individual formations rather than being differentiated by the homogenous eluvium of gneiss. It was also indicated that the soil evolution in this region proceeded from dessication and kaolinization during the middle Pleistocene to accumulation of bases and predominance of fragmental minerals in the early Holocene. The pedogenesis was further related to climate-landscape events in this region during the Quaternary. This study advocated that awareness of soil-landscape evolution was necessary in advance of pedogenesis research and a single soil-forming process could not account perfectly for soil formation with delicate evolution history.  相似文献   

7.
Purpose

Select South Dakota, USA water bodies, including both natural lakes and man-made impoundments, were sampled and analyzed to assess mercury (Hg) dynamics and historical patterns of total Hg deposition.

Materials and methods

Sediment cores were collected from seven South Dakota lakes. Mercury concentrations and flux profiles were determined using lead (210Pb) dating and sedimentation rates.

Results and discussion

Most upper lake sediments contained variable heavy metal concentrations, but became more consistent with depth and age. Five of the seven lakes exhibited Hg accumulation fluxes that peaked between 1920 and 1960, while the remaining two lakes exhibited recent (1995–2009) Hg flux spikes. Historical sediment accumulation rates and Hg flux profiles demonstrate similar peak and stabilized values. Mercury in the sampled South Dakota lakes appears to emanate from watershed transport due to erosion from agricultural land use common to the Northern Great Plains.

Conclusions

For sampled South Dakota lakes, watershed inputs are more significant sources of Hg than atmospheric deposition.

  相似文献   

8.
Peat cores collected from three sites in the Jura region of Switzerland, La Tourbière des Genevez, Etang de la Gruère and Praz Rodet, were analysed for the fallout radionuclides 210Pb, 137Cs, 134Cs and 241Am, and the minerogenic radionuclide 226Ra. Unsupported 210Pb inventories of the cores were all in the range 3900-4784 Bq m-2 and are consistent with their having largely retained the atmospheric flux (ca. 130 Bq m-2y-1). In contrast, comparisons with earlier (1986) cores from these sites suggest that there have been significant losses of fallout 137Cs. Samples from all three sites had low but significant levels of supported 210Pb (226Ra) activity, the origin of which is presumably wind blown soil dust. 210Pb dates calculated using the CRS model were independently validated by 241Am and pollen stratigraphy. The core from La Tourbière des Genevez had a fairly conventional 210Pb activity versus depth profile indicating more or less constant net accumulation during the past 100 years. At the other two sites however the 210Pb profiles contained significant deviations from simple exponential decline that may record episodes in the bog during which there were major variations in the net dry mass accumulation rate. These episodes are dated 1930-50 (Etang de la Gruère) and 1960-80 (Praz Rodet). Although the depths at which total 210Pb reaches equilibrium with the supporting 226Ra range widely, from ca.37 cm in Etang de la Gruére to ca.60 cm in Praz Rodet, mean net dry mass accumulation rates for the past 100 years are remarkably similar, the values for all three sites are in the range 0.023-0.027 g cm-2y-1.  相似文献   

9.
The presence and the extent of the plume of Hamilton Harbour water extending into Lake Ontario was determined in order to assess the importance of metal contaminant transport from Hamilton Harbour into Lake Ontario. Industrially derived Fe compounds, wustite and hematite, were used as plume tracking parameters. Wustite, particularly, proved to be a good tracer of the plume. Annual loadings of particulate heavy metals to Lake Ontario were calculated using the concentrations of heavy metals in suspended solids from the connecting Burlington Canal, Hamilton Harbour and western Lake Ontario. Annual loadings of heavy metals to lake Ontario are ～266 × 103 kg Fe, 9.33 × 103 kg Zn, 1356 kg Pb, 273 kg Cu, 8.7 kg Cd. The relative contribution of the total metal load from Hamilton Harbour to Lake Ontario is negligible when compared to the load from the Niagara River. Lake-harbour water exchange and the high Fe concentrations in benthic sediments of Hamilton Harbour increase P retention in the harbour sediments, thus are beneficial to water quality in Hamilton Harbour.  相似文献   

10.

Purpose

The Matylda catchment, in southern Poland, was polluted by the discharge of mine waters from a lead and zinc mine that inundated parts of a valley floor and caused the accumulation of metal-polluted sediments. After a partial reclamation of the mine site in the early 1980s, polluted sediments continue to accumulate on downstream floodplains and in fishponds. The aim of this study was to reconstruct the changes in metal dispersal during 100?years of mining and during the 40-year post-mining period and to propose a strategy for pollution mitigation in the area.

Materials and methods

Analyses of Cu, Cd, Pb, Zn, Mn, Ca, Mg and Fe concentrations, speciation of heavy metals and mineralogical analyses were undertaken on overbank sediment cores and in stream sediments. Concentrations of the same elements and macro-ions soluble in stream waters were also determined.

Results and discussion

Concentrations of Zn, Cd and Pb in the sediment profiles vary between 40,000 and 55,000, 300 and 600 and 30,000 and 50,000?mg?kg-1, respectively. Changes of metal concentrations and the stratigraphy of sediments from the floodplains, stream channels and fishponds suggest rapid changes of metal loads migrating downstream during both the mining and post-mining periods. Since the time of mine closure, fine-grained, mine-derived sediments (ca. 12?cm thick) have been the main source of pollution of post-mining sediments and surface waters. Closure of the mine was followed by a relatively short period of rapid redistribution of sediment-associated heavy metals in the stream channel. Since the 1980s, the floodplain and fishponds have received a constant supply of metals. It contrasts with the slow sediment accretion rate and a rapid decrease of metal concentrations in floodplain pools due to dilution by decomposed leaf litter. A fivefold increase of Cd content in waters over the 4.6?km reach of the Matylda stream indicates continuous leaching of this element from the contaminated valley floor.

Conclusions

Unsuccessful mine site rehabilitation is due to leaching of mine-originated sediments dispersed over the valley bottom. However, the rate of metal remobilization over the last 40?years is low because of the small thickness and widespread anoxic conditions that prevail within both recent and mine-originated sediments and the alkaline pH of stream water, which reduces metal mobility. Distribution of the contaminated layer over a large area of the valley bottom precludes cost-efficient catchment rehabilitation.  相似文献   

11.
Until 1990 the Bitterfeld region was heavily polluted by mining,an obsolete chemical industry and the uncontrolled deposition ofchemical wastes. The groundwater is extensivly contaminated inthe area of a disused chemical factory which once produced andapplied halogenated compounds on a large scale. At the researcharea in Bitterfeld, highly mobile chlorinated aliphatics andaromatics have been detected in both groundwater and sediments,especially in a lignite seam. The modern analytical method ofsolid-phase micro extraction (SPME) was successfully used toanalyse the pollution level of groundwater and sediments. Thelignite seam was found to have accumulated large quantities ofhalogenated hydrocarbons functioning as a giant adsorptionfilter, and hence recording past groundwater contamination.The vertical and lateral pollution profiles of sediments and thedistribution coefficients between lignite and groundwater atequilibrium conditions were determined for the key components.The consequences of the present situation for the progressivegroundwater quality of the quaternary aquifer are assessed in aforthcoming article.  相似文献   

12.
The concentrations and distribution of selected heavy metals in epipelic and benthic sediments of Cross River Estuary mangrove swamp were studied to determine the extent of anthropogenic inputs from industrial activities and to estimate the effects of seasonal variations on geochemical processes in this tropical estuarine ecosystem. The analysis shows that the mean concentrations (mg/kg, dw) of Cu, Cr, Fe, Ni, Pb, V and Zn vary from 24.1–32.4, 19.9–27.4, 666.7–943.5, 15.2–30.3, 8.8–24.7, 2.2–6.9 and 140.1–188.9, respectively. An important observation is that, in general, lowest metal concentrations are found during the dry season, compared to wet season. Pollution load index (PLI) and index of geoaccumulation (I geo) revealed overall low values but the enrichment factors (EFs) for Cr, Zn, and V were high, and this reflects the intensity of anthropogenic inputs related to industrial discharge into the estuary. The mean concentrations of Zn, Cu and to some extent Ni exceeded the Effects Range—Low (ERL) and Threshold Effect Level (TEL) values in majority of the samples studied, indicating that there may be some ecotoxicological risk to organisms living in these sediments. The inter-element relationship revealed the identical source of elements in the sediments of the studied area. The concentration of heavy metals reported in this work will be useful as baselines for comparison in future sediment quality studies.  相似文献   

13.

Purpose

The purpose of this study was to elucidate historical trends, spatial variations, and the sources of polycyclic aromatic hydrocarbons (PAHs) pollution in several Japanese lakes.

Materials and methods

The vertical distributions of PAHs in the core samples of sediments taken at several points in lakes Kasumigaura, Suwa, Kizaki, and Shinji were determined using a gas chromatograph equipped with a mass selective detector and combined with chronological information and the physical/elemental properties of the sediment.

Results and discussion

Seventeen related compounds (congeners) typically had concentration peaks at sediment depths corresponding to the 1960s to 1970s. In Lake Shinji and one bay of Lake Kasumigaura, there was a tendency for PAH concentrations to increase downstream; in contrast, another bay of Lake Kasumigaura showed the reverse trend. During big flood events, the fluxes of PAHs increased due to large inputs of particulate matter, although PAH concentrations were reduced. For the four study lakes and other similar lakes, PAH concentrations of surface sediments were approximately proportional to population densities in the respective watersheds, while the total input of PAHs to the lakes were correlated with their population and watershed area. The source apportionment analysis using isomer ratios for the congener profiles indicated that the principal sources of the PAHs in the lake sediments were gasoline and/or diesel engine exhausts and biomass burning.

Conclusions

The observed concentration peaks showed a deterioration of the chemical quality of atmospheric conditions around 1960?C1970 and a recent tendency for their amelioration. Between-lake differences suggest that the influence of human activity in the watersheds influences sediment PAH concentrations. The PAH sources were identified to be of pyrogenic origin.  相似文献   

14.
Metal loads to sediments of Lake Simcoe were partitioned into three components, which were attributable to natural background, accelerated erosion, and point + atmospheric sources. These loads were calculated over time using metal concentration profiles together with pre-settlement sedimentation rates based on sonar and time-variable sedimentation rates based on 210Po profiles in cores. Concentrations of metals significantly higher than pre-settlement concentrations were observed in all cores in the case of Pb, back to 80 yr BP on average, and in at least 75% of cores, back to 60 yr BP for Cd and Zn and 30 to 45 yr BP for Cu, Ni, and Cr. Total metal loads increased 3 × for Cu and Ni, 4 × for Zn and Cr, 11 × for Cd and nearly 20 × for Ph from pre-1800 to 0 to 10 yr BP. At present about 90% of the anthropogenic loads of Pb and Cd, and 60 to 70% of the anthropogenic Cu, Ni, Zn, and Cr, are from point + atmospheric sources, the balance being from increased erosion. The direct atmospheric input of Cd is relatively high, approximately 77% of point + atmospheric inputs, while inputs of Cr and Ni are low at 1% and 9%, and inputs of Cu, Zn, and Pb are intermediate at 20 to 40% of point + atmospheric inputs. Two significant findings on spatial distribution of metals were the large increases in metal loads to Cook Bay following the drainage of 33 km2 of marshes for agricultural use and the widespread dispersal of Cr from point source(s) in Kempenfelt Bay.  相似文献   

15.
The concentrations of organic matter, major elements and trace elements were determined at 15 core locations in Lake Superior and Huron. The chemical compositions of the cores are related to sediment particle size, Eh, pH, chronology and location. Concentrations of Si, Al, Ca, Mg, K, Na, and Ti, which represent the major mineral species in the sediments, are generally uniform in each core. Surface enrichments of Hg, Pb, Zn, Cu, Ni, Co, Cd, Cr, Be, V, As, Org-C, and N at many of the locations are attributed to anthropogenic inputs of these elements in recent years. Concentration profiles of Fe, Mn, P, and S are influenced by migration of these elements in the pore waters. High anthropogenic Cu loadings in Lake Superior were related to Cu mining activities in the lake basin, while high anthropogenic inputs of Ni to the Lake Huron sediments were related to Ni contamination from the Sudbury area. Sediment loading calculations show that the anthropogenic inputs of trace and nutrient elements are related to the sedimentation rate, that the inputs are dispersed over wide areas of the lakes and that inputs to Lake Superior have increased significantly since 1955. Evidence is presented that atmospheric inputs are an important source of contaminants.  相似文献   

16.
The aim of this work was to analyse factors which regulate sulphide mobility in the sediments of a dystrophic lagoon (Sacca di Goro, the southern lagoon of the Po river delta, Italy). In 1995-96, sediment oxygen demand and variations in organic matter content, redox potential, iron availability, inorganic sulphur concentrations and sulphate reduction rates were measured in sediment profiles at three stations (G, 4 and 17) representative of the main areas of the lagoon. Stations differed mainly in their salinity range and primary producer communities. High concentrations of reactive iron (110-275 µmol ml-1) and low sulphate reduction rates (0.8-16.1 mmol m-2 d-1) were measured in the sediment. Moreover, high concentrations of reactive ferric iron were detected in winter and spring at the stations closest to the freshwater inputs. Nevertheless, in summer, high concentrations of free sulphides were detected in the porewater, although most of the reactive ferrous iron was not sulphide-bound, indicating that not all of the reactive iron pool was available to buffer against sulphide release and thus measures of reactive iron pools may not be a good measure of the true buffering capacity of the sediment. Furthermore, a considerable production of sulphide may occur in the decaying Ulva biomass in the water column, where its concentration will be independent of the potential buffering capacity of iron in the sediment. Therefore when assessing the vulnerability of coastal lagoons to dystrophic events, both the size and availability of the reactive iron pool as well as the site of sulphide production must be taken into consideration.  相似文献   

17.
The concentrations of Co, Ni, Cu, Zn, Cd, Pb, As, Fe, Mn, and Al were determined in sediments and biota of Songkhla Lake, a shallow coastal lagoon located in southern Thailand. In June 2006, surface sediments were sampled in 44 stations in the three sections of the lake (inner-, middle-, and outer sections). Sediment cores were also sampled in 13 stations in three cross-sections of the lake. In surface sediments, trace and major elements, organic matter, sediment grain size analysis, and sulfides were determined, and in the sediment cores, redox profiles were made. Soil samples were also collected at garbage dumping sites in the vicinity of the lake. In addition, the metal accumulation in two catfish species (Arius maculatus and Osteogeneiosus militaris) and the crustacean (Apseudes sapensis) was also investigated. Trace element concentrations in sediments of Songkhla Lake show that, especially the Outer section of the lake, in particular the sediments at the mouths of the Phawong, U-Taphao, and Samrong Canals are significantly enriched with trace elements due to municipal, agricultural, and industrial discharges entering the lake through the canals. Aluminum-normalized enrichment factors throughout the lake vary from 0.4 to 1.7 for Ni, 0.3 to 3.3 for Cu, 0.2 to 7 for Zn, 0.1 to 14 for As, 1 to 24 for Cd, 0.7 to 6.8 for Pb, and 0.1 to 7.8 for Mn. Correlations between the elements and sediment characteristics show that Cu, Zn, Cd, and Pb are essentially associated with the sulfide fraction; that Ni and Co are predominantly bound to the clay minerals and iron oxy-hydroxides, and that As is principally bound to iron oxy-hydroxides. The accumulation of trace elements between muscle tissue and liver and eggs of A. maculatus and O. militaris is element-specific, but concentrations of trace elements in fish muscle tissue are well within the limits for human consumption.  相似文献   

18.
Historical profiles of trace element concentrations were reconstructed from two mangrove sediment cores collected within the Ba Lat Estuary (BLE), Red River, Vietnam. Chronologies of sediment cores were determined by the 210Pb method, which showed that each respective sediment core from the south and north entrances of BLE provided a record of sediment accumulation spanning approximately 100 and 60 years. The profiles of Pb, Zn, Cu, Cr, V, Co, Sb, and Sn concentrations markedly increased from the years of the 1920s–1950s, and leveled out from 1950s–1980s, and then gradually decreased from 1980s to present. The profiles of Cd and Ag concentrations increased from 1920s–1940s, and then decreased from 1940s to present. The profile of Mo concentrations progressively increased from 1920s–1980s, then decreased to present. The Mn concentrations failed to show a clear trend in both sediment cores. Results from contamination factors, Pearson’s correlation, and hierarchical cluster analysis suggest that the trace elements were likely attributed to discharge of untreated effluents from industry, domestic sewage, as well as non-point sources. Pollution Load Index (PLI) revealed levels higher than other mangrove sediment studies, and the long-term variations in PLI matched significant socioeconomic shifts and population growth in Vietnam. Geoaccumulation Index showed that mangrove sediments were moderately polluted by Pb and Ag, and from unpolluted to moderately polluted by Zn, Cu, and Sb. The concentrations of Pb, Zn, Cu, Cr, and Cd exceeded the threshold effect levels and effect range low concentrations of sediment quality guidelines, implying that the sediments may be occasionally associated with adverse biological effects to benthic organisms.  相似文献   

19.
The history of heavy metal pollution in southern Sydney was reconstructed from wetland sediments using chemical analysis. Seven wetlands along the Pacific coast were examined for present day concentrations of acid-extractable Cd, Cu, Fe, Pb and Zn. Additionally, four of these sites were cored in order to assess past levels of these metal contaminants, changes in organic content and magnetic susceptibility variations. The low nutrient status and closed catchments of the study sites suggested that the pollutants were predominantly derived from atmospheric sources. Surficial sediments were enriched with Cd, Cu, Fe, Pb and Zn levels 5.0, 16.4, 22.7, 8.2 and 22.5 times baseline levels, respectively. In some cases, the concentrations of trace metals were in excess of environmentally acceptable levels. The results show a strong spatial association between sources and levels of pollutants, and the increase in metals levels in sedimentary records corresponds well to documentary historical evidence.This study demonstrates the utility of coastal wetlands in the reconstruction of atmospheric pollution histories, and their particular vulnerability to contamination from airborne pollutants in urban areas.  相似文献   

20.
The concentrations of organic matter, major elements and trace elements were determined at 14 core locations in Lakes Ontario, Erie and Huron. The chemical composition of the cores was related to the sediment particle size, Eh, pH, chronology and location of sampling site. Concentrations of Si, Al, Fe, Mg, Ti, K and Na, which represent the major mineral species in the sediments, are generally uniform in each core. Surface enrichments of Hg, Pb, Zn, Cd, Cu, Be, V, Org-C, N and P are observed at most locations, with their concentrations, usually much greater above the Ambrosia horizon (≈ 120 yr BP), irrespective of the depth of the horizon. The enrichment of these elements is attributed to anthropogenic inputs in recent years. Concentration profiles for Mn and S are related to the migration of these elements in the pore waters. Anthropogenic loadings of the trace metals and nutrients parallel the population and degree of industrialization of each lake drainage basin. Natural loadings parallel the sedimentation rates. Although it is not possible to evaluate the contributions of the trace metals from various sources, evidence is presented that atmospheric inputs are important.  相似文献   

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