Eduard Szöcs

Data in Environmental Science and Eco(toxico-)logy

# Quantitative Ecotoxicology, Page 108, Example 3.7, Accumulation

This is example 3.7 on page 108 of Quantitative Ecotoxicology - reproduced with R. This example is about accumulation in mosquitofish (Gambusia holbrooki).

Get the data from here and read it into R:

This is pretty much like the previous examples:

We fit a nonlinear model to our data . The model is given in equation 3.42 of the book:

We can specify the model as follows:

This equals to equation 3.42:

• $HG = C_t$
• $KU = k_u$
• $KE = k_e$
• $0.24 = C_1$
• $DAY = t$

Unlike in the book I did not specify bounds here (see the previous posts how to do this).

This results in:

So the parameter estimates are:

• $k_e = 0.589 \pm 0.106$
• $k_u = 1866.7 \pm 241.784$

The BCF is given as $BCF = \frac{k_u}{k_e} = 3171.4$

From this we can predict the fish concentration as $C_{fish}=BCF \cdot C_1=761.14$

Finally we plot the data and our model:

Once again we reproduced the results as in the book using R :) The differences for BCF and $C_{fish}$ are due to rounding errors.

Code and data are available on my github-repo under file name ‘p108’.

Written on February 24, 2013