Abstract
Density differences are the key parameter for stratification stability. We used data from the iron-meromictic Waldsee, Germany, a lignite mine pit lake, to quantify the contribution of single solutes to water density and analyzed the density gradient. Iron meromictic lakes maintain their density gradient through chemical reactions. Hence, quantifying the contributions of separate solutes is essential for understanding the entire process. Based on solute concentrations and literature values of partial molal volumes, substance specific density contributions were quantitatively evaluated. Then, by direct measurements of the density of IHSS Waskish peat fulvic acid, we quantified the density contribution of dissolved organic carbon (DOC). While several solutes contributed to the density throughout the water column, only those substances that occurred at higher concentrations in the anoxic monimolimnion than in the oxic mixolimnion were crucial to sustaining the density difference between the two layers. In Waldsee, the density difference between monimolimnion and mixolimnion was attributed to dissolved Fe2+ (0.23 g/L, resulting in a 45 % of the density difference due to solutes) and to the carbonate system (HCO3 −, about 0.16 g/L and CO2, 0.03 g/L) while Ca2+ and DOC delivered only a small contribution. In summer, total density differences were dominated by temperature differences; during winter, solutes sustained meromixis. Finally, we present a complete list of specific density fractions for basically all of the density-relevant substances in fresh waters.
Zusammenfassung
Dichteunterschiede sind der wichtigste Faktor für die Stabilität von Schichtungen in Seen. Wir verwendeten Daten des eisenmeromiktischen Waldsees, eines Braunkohletagebausees, um den Beitrag einzelner gelöster Stoffe zur Dichte des Wassers sowie deren Beitrag zum Dichtegradienten zu bestimmen. In eisenmeromiktischen Seen wird der Dichtegradient durch interne chemische Reaktionen aufrechterhalten. Deshalb ist es für das Verständnis des Gesamtprozesses unerlässlich, den Dichtebeitrag der einzelnen gelösten Stoffe zu quantifizieren. Basierend auf den gemessenen Konzentrationen der gelösten Stoffe sowie Literaturwerten von partiellen molalen Volumina wurden die substanzspezifischen Dichtebeiträge ermittelt. Des Weiteren wurde durch die direkte Messung der Dichte von Fulvinsäure (IHSS Waskish Torfmoor) der Dichtebeitrag von gelöstem organischen Kohlenstoff (DOC) bestimmt. Verschiedene gelöste Stoffe trugen zur Dichte in der gesamten Wassersäule bei. Nur jene Substanzen, die im anoxischen Monimolimnion höhere Konzentrationen als im oxischen Mixolimnion aufwiesen, waren entscheidend für die Aufrechterhaltung des Dichtegradienten zwischen den beiden Schichten. Im Waldsee war der Dichteunterschied zwischen Mixolimnion und Monimolimnion im Wesentlichen auf gelöstes Fe2+ (0,23 g/L, 45% Anteil an der Dichtedifferenz) und das Kohlenstoffsystem (HCO3-, rd. 0,16 g/L und CO2 rd. 0,03 g/L) zurückzuführen. Ca2+ und DOC tragen nur zu einem kleinen Teil zum Dichtegradienten bei. Während die Gesamtdichteunterschiede im Sommer hauptsächlich von Temperaturunterschieden beherrscht wurden, hielten im Winter die gelösten Stoffe die Meromixis aufrecht. Abschließend präsentieren wir eine vollständige Auflistung spezifischer Dichtebeitragskoeffizienten für fast alle dichterelevanten Stoffe in Süßwässern.
Resumen
Las diferencias de densidad son el parámetro clave en la estabilidad de la estratificación. Para cuantificar la contribución de solutos simples a la densidad del agua, hemos usado datos tomados en el lago de la mina de lignita, hierro-meromíctica, en Waldsee, Alemania, y analizado el gradiente de densidad. Los lagos hierro meromícticos mantienen sus gradientes de densidades a través de reacciones químicas. De ese modo, la cuantificación de las contribuciones de solutos separados, es esencial para la comprensión del proceso global. Basado en las concentraciones de soluto y en los valores de volúmenes molales parciales de bibliografía, se evaluaron cuantitativamente las contribuciones de sustancias específicas. Luego, por medidas directas de la densidad del ácido fúlvico de turba IHSS Waskish, se cuantificó la contribución a la densidad de carbón orgánico disuelto (DOC). Mientras muchos solutos contribuyeron a la densidad a través de toda la columna de agua, sólo aquellas sustancias que estaban en mayores concentraciones en la capa monimolimnion (anóxica) que en la capa mixolimnion (óxica), fueron cruciales para sostener la diferencia de densidad entre las dos capas. En Waldsee, la diferencia de densidad entre ambas capas (monimolimnion y mixolimnion) fue atribuida al Fe2+ disuelto (0,23 g/L, resultando en una diferencia de densidad del 45%) y al sistema carbonato (HCO3-, aproximadamente 0,16 g/L, y CO2, 0,03 g/L) mientras Ca2+ y DOC proporcionaron sólo una pequeña contribución. En verano, la diferencia de densidades fue dominada por las diferencias de temperatura; durante el invierno, los solutos mantuvieron meromixis. Finalmente, presentamos una lista completa de fracciones de densidad específica para prácticamente todas las sustancias relevantes para la densidad en aguas dulces.
抽象
密度差异是影响分层湖水分层稳定性的关键因素. 本文以德国瓦尔德塞 (Waldsee/Germany) 某褐煤煤矿积水湖为例, 评价了单类溶质对水密度的分层作用, 并分析了湖水密度梯度. 铁-分层湖 (iron-meromictic lake)通过化学反应维持它们的密度梯度. 因此, 量化不同溶质的密度作用对理解整个湖水密度分层过程非常重要. 基于溶质浓度及其偏摩尔体积的文献值实现溶质密度作用的定量评价. 通过直接测量IHSS沃斯基什(Waskish)泥炭中富里酸的密度, 定量计算溶解有机碳 (DOC) 的密度作用. 当湖水整体水柱密度由几种溶质构成时, 只有那些在缺氧滞水层比好氧混和层浓度大的物质才是形成密度分层的关键物质. 在瓦尔德塞, 滞水层和混合层之间的密度差异主要是由溶解性铁 (0.23g/L, 占密度差异的45%)和碳酸盐系统 (HCO3- 0.16 g/L和CO2 0.03 g/L)引起的, 而钙和溶解有机碳 (DOC) 对密度分层作用较小. 在夏季, 水体总密度分层受温度差异控制; 在冬季, 溶质为半混合状态. 最后, 文章列出了淡水中所有影响水体密度物质的单位密度级.
Similar content being viewed by others
References
Boehrer B, Schultze M (2008) Stratification of lakes. Rev Geophys 46:RG2005. doi:10.1029/2006RG000210
Boehrer B, Dietz S, von Rohden C, Kiwel U, Jöhnk KD, Naujoks S, Ilmberger J, Lessmann D (2009) Double-diffusive deep water circulation in an iron-meromictic lake. Geochem Geophys Geosyst 10(6):Q06006. doi:10.1029/2009GC002389
Boehrer B, Herzsprung P, Schultze M, Millero FJ (2010) Calculating density of water in geochemical lake stratification models. Limnol Oceanogr Methods 8:567–574. doi:10:4319/lom.2010.8.567
Böhrer B, Heidenreich H, Schimmele M, Schultze M (1998) Numerical prognosis for salinity profiles of future lakes in the open cast mine Merseburg-Ost. Int J Salt Lake Res 7(3):235–260. doi:10.1023/A:1009097319823
Brunskill GJ, Ludlam SD (1969) Fayetteville Green Lake, New York. I. Physical and chemical limnology. Limnol Oceanogr 14(6):817–829
Bührer H, Ambühl H (1975) Die Einleitung von gereinigtem Abwasser. Schweiz Z Hydrol 37(2):347–368. doi:10.1007/BF02503411
Chen CTA, Millero FJ (1986) Precise thermodynamic properties for natural waters covering only the limnological range. Limnol Oceanogr 31(3):657–662
Duedall IW, Dayal R, Wiley JD (1976) The partial molal volume of silicic acid in 0.725 m NaCl. Geochimica et Cosmochimica Acta 40:1185–1189 (from Wüest et al. 1996)
Eiffler SW, Schimel K, Millero FJ (1986) Salinity, chloride, and density relationships in ion eriche Onondaga lake, NY. Water Air Soil Pollut 27:169–180
Enns TP, Scholander F, Bradstreet ED (1965) Effect of hydrostatic pressure on gases dissolved in water. J Phys Chem 69:389–426
Gräfe H, Boehrer B, Hoppe H, Müller SC, Hauptmann P (2002) Ultrasonic in-situ measurements of density, adiabatic compressibility, and stability frequency. Limnol Oceanogr 47(4):1255–1260
Heidenreich H, Boehrer B, Kater R, Hennig G (1999) Gekoppelte Modellierung geohydraulischer und limnophysikalischer Vorgänge in Tagebaurestseen und ihrer Umgebung. Grundwasser 4(2):49–54
Hongve D (1980) Chemical stratification and stability of meromictic lakes in the upper Romerike district. Schweiz Z Hydrol 42(2):171–195
Hutchinson GE (1957) A treatise in limnology, vol 1. Wiley, New York City, NY
IHSS (2008) Elemental composition and stable isotopic ratios of IHSS samples. Proceedings of international humic substances society, http://ihss.gatech.edu/ihss2/elements.html. Accessed 6 Nov 2009
Jellison R, Melack JM (1993) Meromixis in hypersaline Mono Lake, California. 1 stratification and vertical mixing during the onset, persistence, and breakdown of meromixis. Limnol Oceanogr 38(5):1008–1019
Karakas G, Brookland I, Boehrer B (2003) Physical characteristics of mining lake 111. Aquat Sci 65(3):297–307
Lide DR (ed) (2008) CRC handbook of chemistry and physics, 89th edn. CRC Press, Boca Raton, FL
Millero FJ (1969) The partial molal volumes of ions in seawater. Limnol Ocanogr 14(3):376–385
Millero FJ (2001) The physical chemistry of natural waters. Wiley, New York City, NY
Parkhurst D, Appelo CAJ (1999) User’s guide to PhreeqC (Version 2)—a computer program for speciation, batch-reaction, on-dimensional transport, and inverse geochemical calculations. USGS Water-Resources Investigations Report 99–4259, Washington DC, USA
Seebach A, Dietz S, Lessmann D, Knoeller K (2008) Estimation of lake water-groundwater interactions in meromicitic mining lakes by modelling isotope signatures of lake water. Isot Environ Health Studies 44:99–110
von Rohden C, Ilmberger J (2001) Tracer experiment with sulfurhexafluoride to quantify the vertical transport in a meromictic pit lake. Aquat Sci 63(4):417–431
von Rohden C, Ilmberger J, Boehrer B (2009) Assessing groundwater coupling and vertical exchange in a meromictic mining lake with an SF6-tracer experiment. J Hydrol 372(1–4):102–108
Wetzel RG (2001) Limnology, 3rd edn. Saunders College Publ, Fort Worth, TX
Wüest A, Piepke G, Halfmann JD (1996) Combined effects of dissolved solids and temperature on the density stratification of Lake Malawi. In: Johnson TC, Odada EO (ed) The limnology, climatology and paleoclimatology of the East African Lakes, Gordon and Breach, Amsterdam, The Netherlands, pp 183–202
Acknowledgments
This study was financially supported by Deutsche Forschungsgemeinschaft (DFG).
Author information
Authors and Affiliations
Corresponding author
Appendix
Appendix
Experimental Determination of the Density Contribution of Waskish Peat Fulvic Acid to density
We dissolved 0.00980 g of IHSS Waskish peat fulvic acid (WPFA) in 0.02 L of pure water. According to IHSS (2008), carbon contributes 53.17 % of the mass, yielding a concentration of 0.261 g/L DOC in the solution. The density of the solution was measured using a PAAR DSA 5000 (Austria) densitometer. A u-shaped glass tube filled with the respective solution is set into vibration and its frequency is measured. The higher the mass inside the tube, the slower is the oscillation. Hence, as the volume is known or calibrated using pure water, the device performs a direct measurement of the density of the contained liquid.
The temperature of the limnologically most interesting temperature interval from 0 to 30 °C was scanned in steps of 1 °C (results see Fig. 6). The same measurement was performed with purified water. The temperatures between both measurements coincided within 0.001 °C. Hence we could calculate the density difference between both measurements, which is attributed to the dissolved Waskish peat fulvic acid (see also Fig. 6). A second order regression was performed to include the (small) temperature signature of the density contribution, which may be neglected for most purposes. The coefficient for various temperatures can be calculated according to:
The density contribution can be related to various references for concentrations. Concentrations of organic matter are either given in mass of organic matter per volume or mass concentration of DOC, i.e. the concentration of the carbon constituent, or finally as molar concentration of carbon. According to IHSS (2008), carbon contributes 53.17 % of the mass: hence we can supply the coefficients also referring to concentration of carbon (mass or molar concentration) (Table 3).
A second measurement at about half the concentration of IHSS Waskish peat fulvic acid (0.005 g/L, see also Fig. 6) yielded very similar results for the coefficients, only about 3 % higher and a very similar, small temperature effect, which is all clearly within the accuracy at which such solutions can be produced and coefficients be evaluated.
Rights and permissions
About this article
Cite this article
Dietz, S., Lessmann, D. & Boehrer, B. Contribution of Solutes to Density Stratification in a Meromictic Lake (Waldsee/Germany). Mine Water Environ 31, 129–137 (2012). https://doi.org/10.1007/s10230-012-0179-3
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10230-012-0179-3