Trace metal dynamics in a seasonally anoxic lake

Morfett, K.; Davison, William; Hamilton−Taylor, John

doi:10.1007/bf02587769

Cited by 42 publications

(13 citation statements)

References 19 publications

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“…The behavior of dissolved Cu in summer is not as well defined as that of Zn by its isopleth diagram (Fig. 6), but a previous plot against time of the dissolved Cu concentration at the sedimentwater interface showed minimal concentrations of Cu (< 5 nmol liter-l) between August and overturn, supporting its removal by sulfide precipitation (Morfett et al 1988).…”

Section: Dissolved Zn and Cu Distributions-dissolvedmentioning

confidence: 82%

“…6) indicates that the source was associated with newly deposited particles. Morfett et al ( 1988) concluded that degradation of newly deposited planktonic algae was the most likely source material for the late spring-early summer maxima, but the timing of events around ice cover (Fig. 3) suggests two separate sources: Fe and Mn oxides for Cu and organic matter, probably plank.tonic algae, for Zn.…”

Section: Dissolved Zn and Cu Distributions-dissolvedmentioning

confidence: 99%

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The biogeochemical cycling of Zn, Cu, Fe, Mn, and dissolved organic C in a seasonally anoxic lake

Hamilton−Taylor

Davison

Morfett

1996

Limnology & Oceanography

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Detailed time-depth distributions of dissolved Zn, Cu, Fe, Mn, and dissolved organic C (DOC), together with pH, were obtained for the water column and near-surface sediment pore waters of a seasonally anoxic lake (Esthwaite Water, U.K.) over a 1 -yr period. Dissolved Fe and Mn followed well-known patterns linked to redox recycling. The variation in DOC resulted mostly from its coupling with Fe, DOC being coprecipitated with Fe oxide and released into solution on the reductive remobilization of' the oxide. This process produced a > 7-fold seasonal variation in DOC concentrations in the pore waters, with a maximum of -7 mg liter-l. Dissolved Zn and Cu exhibited coherent and similar distribution patterns unrelated in any simple way to the distributions of dissolved Fe and Mn, pH, and DOC. The most ubiquitous feature of the distribution of dissolved Zn, and to a lesser degree that of dissolved Cu, was a concentration maximum at the sedimentwater interface, which disappeared completely only when anoxia was maximal in mid-and late summer. The interfacial maxima were attributed to rapid release from freshly deposited particles allied to sulfide precipitation in the sediments. The timing of events, associated with an increase in interfacial dissolved Cu and Zn concentrations before and during a period of ice cover, indicated that the Cu was derived from Fe and possibly Mn oxides and Zn from planktonic algae. The cumulative downward diffusive fluxes of Zn and Cu from the interfacial maxima were unimportant (-1% of total) compared to total metal sedimentation rates. Chemical equilibrium calculations indicated that Zn-and Cu-sulfide complexes dominated in the pore waters under reducing conditions, with humic binding being insignificant, and that precipitation as pure sulfides or coprecipitation with FeS were likely major removal processes for Zn and Cu under anoxic conditions.It is apparent from the limited available information that trace metal distributions in lakes are complex and generally do not show the model (e.g. biologically recycled and scavenged) vertical profiles seen in the oceans (see Murray 1987;Hamilton-Taylor and Davison 1995). This complexity has been attributed to various environmental factors, including the highly dynamic nature of lakes where inputs, mixing, and removal processes can vary significantly on a variety of time scales, the greater availability of competing scavenging phases, the varied chemical composition of lake waters, and the compressed depth scales. Insight into biogeochemical processes has been afforded by considering detailed temporal changes in trace metal distributions in the water columns of lakes (e.g. Baccini and Joller 198 1;Balistrieri et al. 1992). We found no comparable temporal data for the highly active site of the sediment-water interface. This paper provides detailed time-depth distributions of dissolved Zn, Cu, Fe, and Mn, together with DOC and pH, in the water column and near-surface pore waters of a circumneutral, productive, seasonally anoxic lake. Acknowledg...

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Section: Dissolved Zn and Cu Distributions-dissolvedmentioning

confidence: 82%

Section: Dissolved Zn and Cu Distributions-dissolvedmentioning

confidence: 99%

The biogeochemical cycling of Zn, Cu, Fe, Mn, and dissolved organic C in a seasonally anoxic lake

Hamilton−Taylor

Davison

Morfett

1996

Limnology & Oceanography

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“…Sulfide is known to occur in anoxic environments where the rate of oxygen removal is close to or Ž in anoxic lakes Davison and Heaney, 1978;Morfett et al, 1988;Balistrieri et al, 1992Balistrieri et al, , 1994Achterberg . Ž et al, 1997 , and anoxic marine waters Emerson and Jacobs, 1982;Kremling, 1983;Jacobs et al, .…”

Section: Introductionmentioning

confidence: 99%

Metal–sulfide complexation in seawater

1999

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The conditional stability constants of metal-sulfide complexes were determined in pH 8 seawater at various salinities, by Ž . flow-analysis with detection by cathodic stripping voltammetry FA-CSV . Two methods were used. The first method was titration of the sulfide by metal with detection of the free sulfide by FA-CSV. The titrant metals were Ag q , Cd 2q , Co 2q , 2q 2q 2q 2q 3q 3q Ž . Fe , Mn , Pb , Zn , Cr and Al . This method was suitable for comparatively weak complexes log K -; 8 . The Ž . second method took advantage of ligand competition between sulfide and 8-hydroxyquinoline oxine for free metal ions. The ability of the oxine to form electroactive complexes with Cu 2q , Cd 2q , Pb 2q , Zn 2q , Co 2q and Ni 2q , was used to detect the concentration of the metal-oxine complexes in equilibrium with sulfide. More stable complexes could be detected by this method. The two independent methods could be compared for some metals showing good agreement. The stability of the sulfide complexes with copper was found to be much greater than previously determined, in line with theoretical q Ž . prediction. The high stability, greater than that for Ag , suggests that copper may be complexed by sulfide as copper I Ž .2q 2q rather than copper II . Complex stability with Co and Cd is also greater than found before, but the difference is smaller. The stability constants were used to calculate the speciation of sulfide at realistic sulfide and metal concentrations similar to those present in the open ocean. At a sulfide concentration of 0.5 nM and a copper concentration of 1 nM in Ž . Ž Ž . q . seawater, the major form of sulfide is copper II monobisulfide Cu HS representing 99% of the total sulfide. In the Ž . presence of natural organic complexing ligands a smaller percentage 28% of sulfide was bound to copper, the remainder occurring as bisulfide, whereas copper was then 71% complexed by organic matter. The new data and the calculations confirm the potential importance of sulfide as a complexing ligand in seawater, more important than major anions and competing effectively with natural organic ligands. q

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“…Within-lake cycling, which can lead to short-lived heavy metal enrichment of the surface sediment (e.g. Morfett et al 1988;Boyle et al 1998;Boyle 2001a), is a particularly severe problem at sites with low sediment accumulation rates. If the sedimentation rate is so low that the pollution signal is confined to the top 1 -2 sampling intervals, then recycling contributions cannot be distinguished from pollution in the absence of isotope data.…”

Section: Grey With Stonesmentioning

confidence: 99%

Recent Environmental Change and Human Impact on Svalbard: The Lake-Sediment Geochemical Record

Boyle

Appleby

Birks

2004

Journal of Paleolimnology

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As part of a broader investigation into recent environmental change on Svalbard, the inorganic geochemical record of six lake-sediment cores was analysed. The major temporal trends in sediment elemental composition are driven by variations in two contrasting sediment components, both derived from catchment soils: (1) mineral matter, and (2) soil organic matter (SOM), enriched in Fe and Mn oxides and heavy metals.Two environmental impacts are recorded in most or all of the lake sediment sequences. An up-core increase in organic matter can be partly attributed to diagenetic effects, but also requires an enhanced supply of SOM relative to mineral matter. In addition, the central and southern sites all show a ca. 1970 event characterised by an enhanced mineral matter accumulation rate. This requires either an enhanced allochthonous supply or an enhanced mobilisation of littoral sediments. In either case a regional-scale driving force, such as a shift in climate, is required.At five of the lakes the sediment heavy metal concentration profiles can be explained entirely by natural factors. However, at Tenndammen (U), situated close to the Svalbard's largest settlement at Longyearbyen, possible anthropogenic Pb enrichment is found.Comparison of observed and expected heavy metal profiles (based on Greenland ice-core data) shows that the lakes are generally too insensitive to have recorded a long-transported heavy metal pollution signal.

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Trace metal dynamics in a seasonally anoxic lake

Cited by 42 publications

References 19 publications

The biogeochemical cycling of Zn, Cu, Fe, Mn, and dissolved organic C in a seasonally anoxic lake

The biogeochemical cycling of Zn, Cu, Fe, Mn, and dissolved organic C in a seasonally anoxic lake

Metal–sulfide complexation in seawater

Recent Environmental Change and Human Impact on Svalbard: The Lake-Sediment Geochemical Record

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