Quantitative equilibrium calculations

Fundamentals
Problems
      Fraction of atrazine
           Help
           Answer
     Retardation factor
           Answer
     Raining out
           Answer
     Carpet
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           Answer
     Sorption kinetics
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           Answer
     Organic pollutants in water
           Answer
     Fish toxicity test
           Answer
     Ethylacetate
           Answer
     Tetrachlorobenzene
           Answer
     Hexachlorobenzene
           Answer
     Chlorobenzene
           Answer
     Toxicity test
           Answer
     Toxicity test - improving...
     3 phases problem
           Answer
     Sorption experiment
           Answer
     HCH
Excercises for an improved intuitive understanding
Questions for recapitulation
Good to know
Minesweeper-problems

Toxicity test

In a toxicity test for naphthalene, phenantrene and pyrene at 25°C the following, very different EC50-values have been measured (the EC50-value is the concentration in water at which the organisms show an effect when they are kept in this water for a defined time span). The tests had been conducted for each compound separately.

Naphthalene 1266 µg/L log Klipid/water = 3.30 (Lwater/Llipid)
Phenantrene 105 µg/L log Klipid/water = 4.46 (Lwater/Llipid)
Pyrene 22 µg/L log Klipid/water = 5.20 (Lwater/Llipid)


a) Estimate the respective equilibrium concentrations (in µmol/L) in the membrane-lipids of the organisms and comment on the result.


b) The EC50-values from above apply to pure water. Which amount of pyrene would have to be added (per liter) in order to achieve the same toxic effect if the water contained 1 mg/L DOC (e.g. humic acid): log KDOC/water = 4.18 (Lwater/kgDOC)? (Assume that the humic acid exhibits no direct influence on the tested organisms, and that the organisms do not significantly affect the dissolved concentration of pyrene by uptake or metabolism.)