Vertical transport of heavy metals by settling particles in Lake Zurich (original) (raw)
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Aquatic Sciences, 2001
Time-and space-dependent variations in the composition of settling particles were investigated along a longitudinal transect in Lower Lake Zurich. The study was carried out during summer stratification using a two-dimensional array of sediment traps deployed in the hypolimnion. Samples of the sedimentary material were analysed for total C and total N, P, Ca, Si, Al, Fe, Mn, Mg, Na, K, and the trace elements Zr, Sr, Rb, Ti, Ba, S, Pb and Zn. The elements can be classified according to their preferences in associating with a specific carrier phase. The fluxes and composition of trapped particles were found to vary seasonally with fluctuations in the main components (organic matter, calcium carbonate, biogenic silica, manganese and iron oxides, silicates) and spatially due to the following in-lake processes: 1) increasing vertical particle transport of biomass and mineralic material in the shoreward direction, 2) lateral sediment transport, which caused sediment accumulation rates to increase with depth, leading to sediment focusing, 3) episodic and patchy events of CaCO 3 precipitation in the epilimnion followed by sedimentation and lateral dispersion, and 4) formation of a patchy nepheloid layer in the slightly denser bottom waters containing more fine-grained particles in suspension. Sediment focusing by lateral pathways caused by particle transport between the southern and the northern basin of Lower Lake Zurich gave rise to post-depositional in-lake redistribution of particle-bound contaminants.
Aquatic Sciences, 2013
Terrigenous (Sc, Fe, K, Mg, Al, Ti) and anthropogenic (Pb and Cu) element fluxes were measured in a new sediment core from Lake Biel (Switzerland) and in previously well-documented cores from two upstream lakes (Lake Brienz and Lake Thun). These three large perialpine lakes are connected by the Aare River, which is the main tributary to the High Rhine River. Major and trace element analysis of the sediment cores by inductively coupled plasma mass spectrometry (ICP-MS) shows that the site of Lake Brienz receives three times more terrigenous elements than the two other studied sites, given by the role of Lake Brienz as the first major sediment sink located in the foothills of the Alps. Overall, the terrigenous fluxes reconstructed at the three studied sites suggest that the construction of sediment-trapping reservoirs during the twentieth century noticeably decreased the riverine suspended sediment load at a regional scale. In fact, the extensive river damming that occurred in the upstream watershed catchment (between ca. 1930 and 1950 and up to 2,300 m a.s.l.) and that significantly modified seasonal suspended sediment loads and riverine water discharge patterns to downstream lakes noticeably diminished the long-range transport of (fine) terrigenous particles by the Aare River. Concerning the transport of anthropogenic pollutants, the lowest lead enrichment factors (EFs Pb) were measured in the upstream course of the Aare River at the site of Lake Brienz, whereas the metal pollution was highest in downstream Lake Biel, with the maximum values measured between 1940 and 1970 (EF Pb [ 3). The following recorded regional reduction in aquatic Pb pollution started about 15 years before the actual introduction of unleaded gasoline in 1985. Furthermore, the radiometric dating of the sediment core from Lake Biel identifies three events of hydrological transport of artificial radionuclides released by the nuclear reactor of Mühleberg located at more than 15 km upstream of Lake Biel for the time period 1970-2000.
Flow of heavy metals (Ni and Cu) in the catchment area of a subarctic lake
Contemporary Problems of Ecology, 2014
This paper considers methodological approaches to estimating the flow, balance, and accumula tion of heavy metals (HMs) in a lake under conditions of long term air pollution. Using the example of Chunozero Lake in the Lapland State Biospheric Reserve in Murmansk oblast, the accumulation of HMs in sediments is estimated for over a 70 year period of activity of a metallurgical mining enterprise (GMK Severonikel). The thickness of polluted sediments in a greater part of the lake water area averages 2 cm, and the average sedimentation rate for the last 20 years is 1 mm/year. Metals accumulated in lake sediments can indicate a danger of pollution in the future, particularly if processes of lake eutrophication develop. Due to the peculiar properties of substance flow to the Chunozero, the running type of water mass movement, and the elongated form of the lake, only about 3% of HMs that enter the catchment area accumulate in sediments, in contrast to Imandra Lake (which has the largest area), where the accumulation of HMs reaches 55% owing to the fact that they enter mainly in the composition of wastewater and the low velocities of water flow.
Release of metals from polluted sediments in a shallow lake: quantifying resuspension
Hydrobiologia, 1992
The contribution of erosion of bed sediment to the load of metals leaving Lake Ketelmeer, a shallow lake in the Netherlands fed by the IJ ssel branch of the River Rhine, is reported. Transport of suspended matter and associated trace metals was measured using both centrifuges and sediment traps at several locations in the lake. Mass balances of suspended matter and heavy metals were calculated using data from these field measurements. Metal/scandium-ratios were used to identify the source of the suspended matter in the lake. Since the bed sediment is more polluted than the suspended sediment entering the lake, higher metal/scandiumratios were found for bottom sediment in the lake compared with those for suspended matter entering the lake from the River IJssel. Using the metal/scadium-ratio in suspended matter from the lake, it was calculated that bottom sediments made up 43% of the suspended matter leaving the lake. This implies an erosion flux of bottom sediment of 16 g M-2 d-1. For cadmium, mercury, chromium and zinc, this erosion process accounts for more than 50% of the pollutant load leaving Lake Ketelmeer and entering Lake IJsselmeer .
Particulates and the environmental capacity for trace metals
Science of The Total Environment, 1994
The paper deals with the role of particulates in the transfer of trace metals from land to sea. In the mechanisms oriented research, small rivers and their estuaries fulfil a special role by enabling identification of single processes and single transport mechanisms of general relevance to global land-sea interaction. In big rivers the complexity and the overlapping influences often prevent identification of these. Laboratory experiments often defy natural conditions. Small rivers, originating from identifiable and often unique geological regions, with a limited number of anthropogenic activities loading their watersheds, offer a real-life model system for studies of physical and physicochemical processes. The result of field work in the Rata River (Croatian Adriatic) karstic estuary and corollary laboratory experiments have shown the sedimentation pattern with the prevalent accumulation of terrigenous material in the upper estuary. The results indicate that trace metals are either of prevalently natural origin (Cr, Ti, Cd) or anthropogenically superimposed (Cu, Pb, Zn). However, most of the heavy metals accumulate in the proximity of the river mouth due to adsorption to clay minerals. Only Zn concentrations in estuarine sediments indicate its higher mobility and further transport. The results of this investigation should help in understanding the ultimate environmental capacity of the estuary and the adjacent coastal region.
E3S Web of Conferences, 2013
Sequential leaches (sequential extractions) experiment of 62 elements were carried out for assessing the mobility of contaminated heavy metals and metalloids contaminated in natural sediments; river sediments of Oued El Harrach (Algeria) and lagoon sediments of Bizerte (Tunisia), North African Mediterranean coast. Applied extractants for the sequential leaches are: (A) distilled water for extracting water soluble components, (B) 1M sodium-acetate for extracting exchangeable cations by clay minerals and co-precipitations of carbonates, (C) 0.1M sodium-pyrophosphate for extracting the elements bound with organic matter, (D) 0.1M hydroxylamine for extracting the elements bound with amorphous Mn hydroxides, and (E) 0.25M hydroxylamine for extracting the elements bound with amorphous Fe hydroxides and more crystallized Mn hydroxides. According to the results of sequential leaches experiment, contaminated heavy metals, metalloids, and other potentially toxic element (PTEs) in the sediments are mostly presented as exchangeable cations by clay minerals, co-precipitations of carbonate compounds, binding complexes with organic matter, and/or amorphous manganese hydroxides. Mobility of contaminated heavy metal and metalloids is relatively larger in Algerian river sediment than in Tunisian lagoon sediments. However the mobility of the PTEs in the sediments can be easily changed if the depositional environment is altered by civil construction works.
Role of sediment composition in trace metal distribution in lake sediments
Applied Geochemistry, 2002
Sediment cores were collected from 20 lakes from the Muskoka region of Ontario, Canada, to study vertical changes in trace metal concentrations with depth and the distribution of metals amongst humic material, amorphous and crystalline Fe and Mn oxides, insoluble organics/sulphides, and silicates. Based on their total concentrations, trace elements displayed different degrees of affinity for the organic fraction (represented by organic C) and the mineral fraction (represented by Al). Certain elements (Hg, As, Sb, Pb, Cd, and Zn) displayed a positive correlation with organic C, a negative correlation with Al, and enrichment in surface sediments (with enrichment factors ranging from 2 to 24). Detailed speciation studies revealed that these elements were associated mainly with humic material and to a lesser extent with oxides in surface sediments. Other elements (Al, Cr, Co, Fe, and Mn) displayed a negative correlation with organic C, a positive correlation with Al, and no consistent enrichment in their total concentration at the surface. The speciation study revealed that metals of the latter group were mainly associated with the silicate fraction in both surface and deep sediments. This study shows that relative affinities for organic and mineral fractions play an important role in the distribution of trace metals during burial and diagenesis, and hence in the shape of their vertical profiles.