In the EFDC toxin model does POC bound mean toxins bound to organic matter only, or does it also include toxins bound to sediments?
Your question is not crystal clear.
The toxics model has been significantly improved from EE7.1. So, it is important to first figure out which version of EFDC model you are using to run the toxics model. Prior to EE7.1, it was not possible to specify individual sorption models for each toxic that was being simulated. However, from EE7.1 users can specify different Sorption models for each toxic. POC and DOC are environmental variables but depending upon which Sorption model is used, partition coefficients used in the model would vary.
For example, in EE7.1/ EE7.2 versions you can see that there are four different methods to specify the partition coefficients. They are:
a. Simple Kd
b. DOC and POC : So, when you check the option “DOC and POC” user needs to specify the POC and DOC for water column and sediment bed. In “DOC and POC” option, toxics are sorbed only to the user input POC and DOC not “foc * TSS”.
c. POC only, for * TSS Dependent: In this option, POC is calculated using the formula “foc * TSS concentration”. POC is calculated and DOC is not used.
d. DOC & foc * TSS (POC): In this option, DOC is specified and POC is computed using formula “foc * TSS concentration”.
where foc = fraction of organic carbon
So, overall I would say that you need to figure out which version of EEDC_DSI you are using and which Sorption model you are using to specify the partition coefficients because different options requires different types of inputs. POC may refer to inorganic sediments as well as organic matter.