MODELLING AQUATIC ECOSYSTEMS
- ETH Zurich, Spring Semester 2017
1
Exercise 3b: General solution for stoichiometric calculations
Goals:
• Understand the concepts of stoichiometric calculations introduced in section 4.3.
• Be able to do (arbitrarily complex) stoichiometric calculations based on the general
solution of stoichiometric equations (section 4.3.3) using the R package stoichcalc
(chapter 14).
• Learn to be attentive to error messages and to correct the code accordingly (execute
the code piece by piece and proceed only if everything was correct).
Task 1: Simple stoichiometric calculation using the stoichcalc-package
Calculate numerically the stoichiometry of the model described in section 4.3.2.1 (Table
4.5) using the stoichcalc-package.
Use the following parameter values:
αN = 0.06, αP = 0.01.
Task 2: Complex stoichiometric calculation using the stoichcalc-package
Calculate numerically the stoichiometry of the model described in section 4.3.2.2 (Tables
4.6 and 4.7) using the stoichcalc-package.
Use the following parameter values:
αO,ALG = 0.50,PαH,ALG = 0.07, αN,ALG = 0.06, αP,ALG = 0.005,
αC,ALG = 1 − x∈{O,H,N,P} αx,ALG ,
αO,ZOO = 0.50,PαH,ZOO = 0.07, αN,ZOO = 0.06, αP,ZOO = 0.01,
αC,ZOO = 1 − x∈{O,H,N,P} αx,ZOO ,
αO,POM = 0.40,PαH,POM = 0.07, αN,POM = 0.04, αP,POM = 0.007,
αC,POM = 1 − x∈{O,H,N,P} αx,POM ,
YZOO = 0.2, fe = 0.4,
αN,ALG αP,ALG
αN,ZOO αP,ZOO
YALG,death = min 1, αN,POM
, αP,POM , YZOO,death = min 1, αN,POM
, αP,POM .
Find and correct the implementation error in the provided script.
Questions
• Is it important to know the number of independent processes possible for a given set
of substances of known composition?
• How can the number of required additional constraints be derived easily?
Under which circumstances would this simple approach fail?
• Where to get the required additional constraints from?