Bioturbation in the NanoFASE model

In the NanoFASE water-soil-organism model, bioturbation is modelled by a 1D bioturbation model which splits the soil into a number of layers L, each with a depth dl (m) and concentration of nanomaterial [NM]l (mg/kg soil). On each time step, a certain depth of soil is instantaneously mixed between each adjacent layer. This depth is calculated from the soil turnover rate v (m/s), which we assume is directly proportional to the density of earthworms in the soil w [Rodriguez 2006]. For bioturbation between layers l and l+1,

v_{l:l}=\beta w_{l}

where β (m4/s) is a bioturbation fitting parameter. From this, we calculate a bioturbation rate (/s) as k(bioturb,l:l+1)=v(l:l+1)/dl. Thus, the nanomaterial concentration in a given layer at time t+1 is calculated as:

[NM]_{l,t+1}=[NM]_{l,t}+k_{bioturb,l:l+1,t}\delta t([NM]_{l+1,t}-[NM]_{l,t})+k_{bioturb,l-1:l,t}\delta t([NM]_{l-1,t}-[NM]_{l,t})

where δt  is the length of the model time step (s). Parameterisation of the model provided values for β of ~10-12  m4/s.

Used in 

 
 


             \LARGE v                                              \LARGE k_{bioturb}
soil turnover rate (m/s)                        bioturbation rate (/s)

        

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Read also
 

Visit the NanoFASE Library to read summaries of these reports:

NanoFASE Report D2.1 Specification for the NanoFASE model

NanoFASE Report D2.2 Spatial transport framework 

Baccaro, M., Harrison, S., den Berg, H., Sloot, L., Hermans, D., Cornelis, G., van Gestel, C. A., van den Brink, N. W. (2019) Bioturbation of Ag2S-NPs in soil columns by earthworms. Environmental Pollution 252, A, September. doi.org/10.1016/j.envpol.2019.05.106 

Rodriguez, M.D., 2006. The bioturbation transport of chemicals in surface soils, Department of Chemical Engineering, Louisiana State University and Agricultural and Mechanical College.

 

Contact

 

  

Sam Harrison

Centre for Ecology and Hydrology (CEH)