Abstract—Lac Pavin is a volcanic crater lake in the Massif Central (France), characterized by a p... more Abstract—Lac Pavin is a volcanic crater lake in the Massif Central (France), characterized by a permanent vertical density stratification resulting from a strong and persistent chemocline between about 60 and 70 m depth. The deep water below the chemocline forms the monimolimnion, in which most dissolved ions as well as helium, carbon dioxide, and methane are strongly enriched. The 3He/4He isotope ratio of the excess helium is (9.09 6 0.01) z 1026, or (6.57 6 0.01) Ra. These findings clearly indicate a flux of mantle-derived magmatic gases into the monimolimnion. In order to derive the fluxes of magmatic volatiles into Lac Pavin, it is essential to understand the hydrologic characteristics of the lake. Previously published two-box models have assumed groundwater input at the lake bottom, a short residence time in the monimolimnion, and biogenic origin of the CO2. We propose an alternative model with a flux of magmatic gases, but not of water, into the monimolimnion, and a weak diffu...
Three analytical diffusion models are used to describe the distribution of a nonconservative trac... more Three analytical diffusion models are used to describe the distribution of a nonconservative tracer in the hypolimnion of a lake: The one-dimensional vertical (1-DV) model, developed for tracers in the deep sea, leads to a significant overestimation of vertical diffusivity K, in lakes; the one-dimensional topographic vertical (1-DTV) model, applicable if horizontal mixing is fast com-pared to in situ decay, demonstrates that, except for the deepest layers, vertical tracer distributions are insensitive to K,; the one-dimensional topographic horizontal (l-DTH) model, in which hor-izontal mixing is incomplete and vertical diffusion is disregarded, is the appropriate model for the interpretation of vertical excess 222Rn profiles a few meters above the lake bottom. The radon flux F from the bottom is calculated from 226Ra in the sediments and corrected for depth variation of porosity and radium activity. In Baldeggersee (Switzerland), Fis 390 f 70 dpm.m-2.d-1. Radium activities in the se...
ABSTRACT Physical processes such as the intensity of vertical mixing, influence the annual primar... more ABSTRACT Physical processes such as the intensity of vertical mixing, influence the annual primary production (ΣP) which is chosen as trophic state index. Measured values of ΣP can be split into two components, a minimum productivity (ΣP0) calculated with a simple epilimnic one-box model, and an “internal productivity” (ΣP1) attributed to internal nutrient supply by vertical mixing. A statistical analysis for ΣP versus Lp, the annual P-input per unit lake surface, based on 62 lakes from North America and Europe, reveals a tendency for ΣP to increase with decreasing mean depth. For Lp>3 g P m-2yr-1, ΣP reaches a saturation value of about 400 gC m-2yr-1, while the influence of ΣP1 disappears due to light limitation. For an intermediate Lp, the large variation of ΣP among individual lakes with the same loading shows the importance of other factors such as morphometry, intensity of vertical mixing (reflecting exposure to wind), and the redox potential at the sediment-water interface. The later controls the redissolution of mineralized nutrients at the sediment surface.
Organic Micropollutants in the Aquatic Environment, 1988
Mathematical models for evaluating the dynamic behaviour of anthropogenic substances in aquatic s... more Mathematical models for evaluating the dynamic behaviour of anthropogenic substances in aquatic systems (MASAS) are being developed and implemented on a personal computer. The MASAS system will allow the user to construct models of increasing complexity for lakes, rivers, and groundwater aquifers, and to build up compound and system libraries. In this paper, the general concept of the MASAS system is described and a summary of the present status of implementation is given.
Organic Micropollutants in the Aquatic Environment, 1986
Modelling of the behaviour of micropollutants in the aquatic environment serves to generalize to ... more Modelling of the behaviour of micropollutants in the aquatic environment serves to generalize to other systems the knowledge gained from measurements in a specific situation, provided that certain rules are obeyed. In order to use a model as a tool for predicting concentrations in natural systems, calibration of the model is necessary. The model should be as simple as possible and only contain quantities which can be actually measured. The proper choice of model dimensionality, a key factor of model complexity, can be made by comparing reaction and mixing rates.
... Environmental Organic Chemistry, 2nd Edition. Rene P. Schwarzenbach, Philip M. Gschwend and D... more ... Environmental Organic Chemistry, 2nd Edition. Rene P. Schwarzenbach, Philip M. Gschwend and Dieter M. Imboden Copyright 0 2003 John Wiley &L Sons, Inc. Page 2. ... These findings were first quantified in a linear free energy relation-ship by Swain and Scott (1953): (13-3) ...
Abstract—Lac Pavin is a volcanic crater lake in the Massif Central (France), characterized by a p... more Abstract—Lac Pavin is a volcanic crater lake in the Massif Central (France), characterized by a permanent vertical density stratification resulting from a strong and persistent chemocline between about 60 and 70 m depth. The deep water below the chemocline forms the monimolimnion, in which most dissolved ions as well as helium, carbon dioxide, and methane are strongly enriched. The 3He/4He isotope ratio of the excess helium is (9.09 6 0.01) z 1026, or (6.57 6 0.01) Ra. These findings clearly indicate a flux of mantle-derived magmatic gases into the monimolimnion. In order to derive the fluxes of magmatic volatiles into Lac Pavin, it is essential to understand the hydrologic characteristics of the lake. Previously published two-box models have assumed groundwater input at the lake bottom, a short residence time in the monimolimnion, and biogenic origin of the CO2. We propose an alternative model with a flux of magmatic gases, but not of water, into the monimolimnion, and a weak diffu...
Three analytical diffusion models are used to describe the distribution of a nonconservative trac... more Three analytical diffusion models are used to describe the distribution of a nonconservative tracer in the hypolimnion of a lake: The one-dimensional vertical (1-DV) model, developed for tracers in the deep sea, leads to a significant overestimation of vertical diffusivity K, in lakes; the one-dimensional topographic vertical (1-DTV) model, applicable if horizontal mixing is fast com-pared to in situ decay, demonstrates that, except for the deepest layers, vertical tracer distributions are insensitive to K,; the one-dimensional topographic horizontal (l-DTH) model, in which hor-izontal mixing is incomplete and vertical diffusion is disregarded, is the appropriate model for the interpretation of vertical excess 222Rn profiles a few meters above the lake bottom. The radon flux F from the bottom is calculated from 226Ra in the sediments and corrected for depth variation of porosity and radium activity. In Baldeggersee (Switzerland), Fis 390 f 70 dpm.m-2.d-1. Radium activities in the se...
ABSTRACT Physical processes such as the intensity of vertical mixing, influence the annual primar... more ABSTRACT Physical processes such as the intensity of vertical mixing, influence the annual primary production (ΣP) which is chosen as trophic state index. Measured values of ΣP can be split into two components, a minimum productivity (ΣP0) calculated with a simple epilimnic one-box model, and an “internal productivity” (ΣP1) attributed to internal nutrient supply by vertical mixing. A statistical analysis for ΣP versus Lp, the annual P-input per unit lake surface, based on 62 lakes from North America and Europe, reveals a tendency for ΣP to increase with decreasing mean depth. For Lp>3 g P m-2yr-1, ΣP reaches a saturation value of about 400 gC m-2yr-1, while the influence of ΣP1 disappears due to light limitation. For an intermediate Lp, the large variation of ΣP among individual lakes with the same loading shows the importance of other factors such as morphometry, intensity of vertical mixing (reflecting exposure to wind), and the redox potential at the sediment-water interface. The later controls the redissolution of mineralized nutrients at the sediment surface.
Organic Micropollutants in the Aquatic Environment, 1988
Mathematical models for evaluating the dynamic behaviour of anthropogenic substances in aquatic s... more Mathematical models for evaluating the dynamic behaviour of anthropogenic substances in aquatic systems (MASAS) are being developed and implemented on a personal computer. The MASAS system will allow the user to construct models of increasing complexity for lakes, rivers, and groundwater aquifers, and to build up compound and system libraries. In this paper, the general concept of the MASAS system is described and a summary of the present status of implementation is given.
Organic Micropollutants in the Aquatic Environment, 1986
Modelling of the behaviour of micropollutants in the aquatic environment serves to generalize to ... more Modelling of the behaviour of micropollutants in the aquatic environment serves to generalize to other systems the knowledge gained from measurements in a specific situation, provided that certain rules are obeyed. In order to use a model as a tool for predicting concentrations in natural systems, calibration of the model is necessary. The model should be as simple as possible and only contain quantities which can be actually measured. The proper choice of model dimensionality, a key factor of model complexity, can be made by comparing reaction and mixing rates.
... Environmental Organic Chemistry, 2nd Edition. Rene P. Schwarzenbach, Philip M. Gschwend and D... more ... Environmental Organic Chemistry, 2nd Edition. Rene P. Schwarzenbach, Philip M. Gschwend and Dieter M. Imboden Copyright 0 2003 John Wiley &L Sons, Inc. Page 2. ... These findings were first quantified in a linear free energy relation-ship by Swain and Scott (1953): (13-3) ...
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