In three limno-corrals of the MELIMEX project the transport paths of the trace metals Cu, Zn, Cd, Hg and Pb and the reaction of the systems on increased metal loads were investigated. The metal balances lead to the conclusion that the biomass is the main factor responsible for the regulation of trace metal concentration. The observed sequence of relative residence times of the trace metals can be described with a steady-state model. Additional metal load decreases the ability of the limnic system to lower the metal concentration. The production of phytoplankton and its assimilation capacity for metals are reduced leading to relatively higher metal concentrations in the lake.
List of symbols[BM] C c ~c DM [DMI er e, F [FHO HZ i J Kso LI, L2 M MC o [P] [PM] [PN] pP po Concentration of metal in biomass [mole/kg dry matter] Control corral Quantity of metal in the corral [mole] Quantity of metal taken up or released by the corral ]mole] Distribution coefficient [m3kg -I] Concentration of dissolved metal in the corral [M] Random error of the metal balance [mole] Systematic error of the metal balance [mole] Area of the corral bottom [m 2] Concentration of filterable Hg fraction [M] Hydrozincite Quantity of metal in the inflow [mole] Index of sampling interval Solubifity product Loaded corrals Index for metal Metal carbonate Quantity of metal in the outflow [mole] Concentration of biomass [kg dry matter m -3] Concentration of particulate metal [mole m -3] Concentration of particulate Kjeldahl nitrogen [mg m -3] Negative logarithm of the calculated solubility products Negative logarithm of the observed solubility products P. Baccini, J. Ruchti, O. Wanner, E. Grieder: Trace metal concentrations 203 Q Qs S [SN] ~r [TM] [Tij ,~t [VHg] WM Water flux to and from limno-corrals [m3d -l] Sedimentation flux [m 3d-I] Quantity of metal sedimented in the corral [mole] Sedimentation of Kjeldahl nitrogen [rag m -2d-I] Sedimentation rate [m d-q Concentration of total metal in the corral [M] Concentration of total metal in the inflow [M] Observation period [d] Concentration of volatile mercury fraction [M] Rate of adsoprtion of metal M at the corral wall [mole d -I]
The oxygen exchange constant, photosynthetic rate, and respiration rate for several Swiss rivers have been determined using only the continuous data record of a single oxygen electrode, the measured tcmpcrature, and an assumed ideal light intensity curve in conjunction with a simple model rate equation and a novel cross-correlation computational technique. The method can, in favorable circumstances, be extended to determine also total carbonate dynamics from continuous pH measurements.For the Aare at Bern in March 1974, the oxygen exchange constant was 0.38 h-l, the respiration rate was 0.6 mg liter-' h-l, and mean photosynthetic rate was 0.28 mg liter-l h-l. The exchange rate for dissolved (but not hydrated or ionized) COti was 0.91 times that for dissolved oxygen. and the ratio of 02 molecules released to COP molecules consumed during photosynthesis was about 1.2.
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