If you jumped straight into part 3, you can cheat by downloading this file.
We can now estimate the lead concentration in the diet of the soldiers (dying on the beaches of the river Glein). This diet we can plug into a model for a human being.
You will learn:
The human intake model aggregates sources of contamination for a human being (concentrations in air, dust and soil, food items etc.) and calculates the net exposure to an individual through ingestion and inhalation.
A small box should now have appeared on the line, which can be moved around to make the line bend and shift.
To remove a waypoint:
Studies from a archaeologists have revealed that another potential exposure route for the soldiers might have been their heavy chips eating habit. As potato had not yet been introduced in Britain, we must assume that the chips were imported. We have no way (or interest) in modelling the lead concentration in chips but we would be careless to exclude this potential pathway.
The human intake model should have given you new options in the drop down list next to the Add button. It contains all kinds of food types which can be modelled by MERLIN-Expo (leaf, fruit, grain etc.). For food types that should not be modelled, you should use External food.
The human intake model asks for several concentrations. Some of these can be calculated by other MERLIN-Expo models.
We will assume that the lead concentration in chips stays the same during the entire simulation time.
Concentration in external food
Material: Lead, External food: Chips
|Time||Value (mg kgfw-1)|
The parameters screen allows us to describe the diet of a soldier through the parameter Ingestion rate for different types of food. All types of invertebrates and fish appear here, the ones that aren't consumed by humans we can ignore by putting zeroes. The soldiers also sometimes drink river water. Did you notice the arrow from River to Human intake in the graph? You can specify how much unfiltered river water the soldiers drink with the parameter Ingestion rate for different types of liquids. We will resist the temptation to enter ingestion rates for when soldiers bite the dust.
Ingestion rate for foods
|Food||Value (kg.fw d-1)|
Ingestion rate for liquids
|Food||Value (L d-1)|
For each model a few outputs have been selected for you. If you are interested in seeing results of intermediate calculations or your inputs, you must specify them.
As you can see, there is quite a lot inside each of the model boxes. Just to make sure that everything is set up ok we want to see exactly what goes into the human intake model and what leaves it.
|Concentration in external foods|
|Concentration in fish|
|Concentration in foods|
|Concentration in invertebrates|
|Concentration in liquids|
|Concentration in river water|
|Fraction of total quantity ingested from foods|
|Fraction of total quantity ingested from liquids|
|Quantity ingested from foods|
|Quantity ingested from liquids|
If you want numbers from a simulation, tables are much better than plots. Go to the tables screen.
The tables screen is very similar to the charts screen. After a normal simulation, two types of tables are available.
In order to make life a little easier, turn off automatic table creation:
Next display the dependencies for each output
The total quantity (of lead) ingested, as well as the different quantities (of lead) ingested from different foods can be found in the outputs of Human intake. There is also an output for the fraction for the contribution from each food type to the total ingested quantity (Fraction of total quantity ingested from food).
Which of the food type(s) would you tell the soldiers to avoid?
Return to the model screen. As you continue to add boxes, there will be a time when the game "don't cross the line" will drive you mad. This is when you might consider using the interaction matrix instead of the graph.
In short, the interaction matrix is like a graph but where the boxes are all on the diagonal. The “arrows” are put in the off-diagonal cells in a clock-wise order, so that a connection from box A to box B is put on the same row as A and in the same column as B.
You switch to the interaction matrix by clicking the Matrix button. Note that you can jump back and forth between these, an update in the graph will reflect in the matrix and vice versa.
We have everything set up for adding our soldier. If we wanted to study several soldiers (footmen, spearmen, knights etc.) we can do so using the population model but to keep things simple we will study just one individual.
The man model offer a long list of parameters, most of which you should not touch. An important parameter is Age at the beginning of the simulation. The age is used to calculate a lot of things about the body; the body weight, the breathing frequency, the cardiac output etc.
Enter the following value:
Age at the beginning of the simulation
If you want to compare your model with ours, download this.