Exchange Flow in a Shallow Lake Embayment

Pálmarsson, Sveinn Ó.; Schladow, S. Geoffrey

doi:10.1890/06-1618.1

Cited by 9 publications

(21 citation statements)

References 15 publications

(17 reference statements)

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“…The horizontal density fl ow found in this work was within the rates of convective currents caused by differential heating and cooling as estimated in past studies; 1 cm/s between open water and stands of Typha [13], 1.5-2.8 cm/s between open water and reed beds [11,12], 3-5 cm/s between the wetland and lake [5], and 2-3.5 cm/s [3] and 0.4-11 cm/s [4] between shallower and deeper water. It should be emphasized that the estimation of the exchange fl ow in this study was based on Monin-Obukhov similarity theory which breaks down as wind speeds decrease to nearly wind-less free convection [44,45] and this could have an effect on the night-time heat fl ux calculations.…”

Section: Temperature Structure and Water Exchangesupporting

confidence: 88%

“…Convective circulation induced by density gradients resulting from horizontal depth variation has been demonstrated to be an important exchange mechanism of phosphorus [1,2] and mercury [3] between the littoral and pelagic zones, nutrients between side embayment and the main basin of reservoir [4], and pollutants between a fringing wetland and lake [5]. A temperature gradient develops when shallow littoral areas and deeper pelagic zones receive the same incoming solar radiation but distribute it differently over their respective volumes [1,4,6,7].…”

Section: Introductionmentioning

confidence: 99%

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Physical circulation and spatial exchange dynamics in a shallow floodplain wetland

et al. 2012

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This paper examines the spatial patterns of water exchange based on water temperature variation between littoral and pelagic zones and compares the patterns in a series of shallow lakes at different water levels. Exchange patterns were assessed by developing isotherms along the transects and estimating the surface energy budget using the vertical temperature profi le and time-series measurements. Our results indicate the presence of density-driven fl ow induced by the differential temperature gradient between littoral areas, which are dominated by either fl oating-leaved or submerged vegetation, and the open pelagic region. Persistent stratifi cation was noted in the narrower lakes, which was thought to be due to the presence of dense submerged vegetation that attenuate wind-driven turbulence. In addition, variation of thermal stratifi cation and mixing dynamics between these lakes at different water levels has corresponding effects on the biological and chemical regimes. The circulation contributes to increased transport of the phosphate that could favour submerged species and subsequently induce shifts of macrophyte community composition. The results of this study have implications for the rehabilitation and management of lake ecosystems.

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Section: Temperature Structure and Water Exchangesupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Physical circulation and spatial exchange dynamics in a shallow floodplain wetland

et al. 2012

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“…Winds play an important role in the movement of contaminants within Clear Lake (Pa´lmarsson andSchladow 2008, Rueda et al 2008). Although episodic storms may produce winds from any direction, wind in the Clear Lake basin blows predominantly from the west-northwest toward the Sacramento Valley (Fig.…”

Section: The Historical Landscapementioning

confidence: 99%

“…The exchange of water and Hg-contaminated particles between the main body of water in each basin and the littoral regions is augmented by a different set of processes. Here, differential heating and cooling between the shallow and deep regions leads to the formation of offshore surface currents and onshore bottom return flows during the day and the reverse at night (Pa´lmarsson andSchladow 2008, Rueda et al 2008). This process provides a mechanism whereby suspended material from the pelagic zone can be transported directly to the shore.…”

Section: Total Mercury and Methylmercury Transport Throughout Clear Lakementioning

confidence: 99%

The Legacy of Mercury Cycling From Mining Sources in an Aquatic Ecosystem: From Ore to Organism

Suchanek

Richerson

Zierenberg

et al. 2008

Ecological Applications

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Clear Lake is the site of an abandoned mercury (Hg) mine (active intermittently from 1873 to 1957), now a U.S. Environmental Protection Agency Superfund Site. Mining activities, including bulldozing waste rock and tailings into the lake, resulted in approximately 100 Mg of Hg entering the lake's ecosystem. This series of papers represents the culmination of approximately 15 years of Hg-related studies on this ecosystem, following Hg from the ore body to the highest trophic levels. A series of physical, chemical, biological, and limnological studies elucidate how ongoing Hg loading to the lake is influenced by acid mine drainage and how wind-driven currents and baroclinic circulation patterns redistribute Hg throughout the lake. Methylmercury (MeHg) production in this system is controlled by both sulfate-reducing bacteria as well as newly identified iron-reducing bacteria. Sediment cores (dated with dichlorodiphenyldichlorethane [DDD], 210pb, and 14C) to approximately 250 cm depth (representing up to approximately 3000 years before present) elucidate a record of total Hg (TotHg) loading to the lake from natural sources and mining and demonstrate how MeHg remains stable at depth within the sediment column for decades to millenia. Core data also identify other stresses that have influenced the Clear Lake Basin especially over the past 150 years. Although Clear Lake is one of the most Hg-contaminated lakes in the world, biota do not exhibit MeHg concentrations as high as would be predicted based on the gross level of Hg loading. We compare Clear Lake's TotHg and MeHg concentrations with other sites worldwide and suggest several hypotheses to explain why this discrepancy exists. Based on our data, together with state and federal water and sediment quality criteria, we predict potential resulting environmental and human health effects and provide data that can assist remediation efforts.

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“…Mining of cinnabar (HgS) from the Sulphur Bank Mercury Mine (a U.S. Environmental Protection Agency [U.S. EPA] Superfund Site since 1990) along the shoreline of the lake, from 1873 to 1957 (Table 1), plus subsequent erosion and acid mine drainage have resulted in the deposition of an estimated 100 Mg of Hg into the Clear Lake aquatic ecosystem. Most of this Hg was deposited in the proximity of the abandoned mine (Chamberlin et al 1990) but moved throughout the lake by sediment transport processes (Pa´lmarsson andSchladow 2008, Rueda et al 2008). Commercial Hg extraction was accomplished initially by surface scrapes and shaft mining from ca.…”

Section: Introductionmentioning

confidence: 99%

Vertical Stability of Mercury in Historic and Prehistoric Sediments From Clear Lake, California

Suchanek

Richerson

Zierenberg

et al. 2008

Ecological Applications

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Abstract. Clear Lake, California, USA, is the site of the Sulphur Bank Mercury Mine, now a U.S. Environmental Protection Agency Superfund Site. Intermittent mining from 1873 to 1957 resulted in ;100 Mg of mercury (Hg) being deposited into the lake's ecosystem. Sediment cores to ;2.5 m depth (dated using 210 Pb and 14 C) represent ;3000 years of sedimentation. Clear Lake sediments have experienced Hg deposition from anthropogenic sources (mining) during historic times (to the mid-1900s) and geologic sources during prehistoric times (prior to the mid-1800s). This provides a unique opportunity to evaluate hypotheses relating to (1) the influence of the mine on Hg loading to the lake and (2) the potential upward mobilization of Hg by diagenetic processes proposed by some as an alternative explanation for increased Hg concentrations at the surface of the sediment column believed to be caused by increased global atmospheric deposition.Although Hg mining began in 1873, no significant evidence of anthropogenic Hg loading was detected in cores prior to open-pit mining ca. 1927, which also involved bulldozing mine waste rock and tailings into the lake. Exponential increases in total Hg (TotHg) and methylmercury (MeHg) were observed above the 1927 horizon, where estimated sedimentation rates were 2.2-20.4 mm/yr and peaks of both forms of Hg maintained vertical stability within the sediment column. Below the 1927 horizon, a slow increase in both TotHg and MeHg with depth was observed from ;1000 to 3000 years before present, where sedimentation rates ranged from ;0.6 to 2.0 mm/yr and elevated Hg profiles appear stable. Vertical stability of Hg in the shallow and deep sediment column suggests that both TotHg and MeHg do not undergo diagenetic upward mobilization within the sediment column under rapid or slow sedimentation rates. Because (1) these data were collected at a site with known anthropogenic and geologic sources and (2) regions of elevated Hg concentrations from both sources remain stable within the sediment column under very different sedimentation regimes, these results also support the hypothesis that elevated Hg at the surface of cores in other worldwide locations likely represents global atmospheric deposition rather than upward diagenetic mobilization.

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Exchange Flow in a Shallow Lake Embayment

Cited by 9 publications

References 15 publications

Physical circulation and spatial exchange dynamics in a shallow floodplain wetland

Physical circulation and spatial exchange dynamics in a shallow floodplain wetland

The Legacy of Mercury Cycling From Mining Sources in an Aquatic Ecosystem: From Ore to Organism

Vertical Stability of Mercury in Historic and Prehistoric Sediments From Clear Lake, California

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