param_defaults: Default parameters

In lemna: Lemna Ecotox Effect Model

Default parameters

Description

Returns the default Lemna model parameters as reported by Klein et al. (2022).

Usage

param_defaults(values)

param_new(values)

Arguments

values

optional named numeric vector, values will override any defaults

Details

Model parameters

Growth model

• k_photo_fixed, Model switch for unlimited growth conditions (TRUE/FALSE)

• k_photo_max, Maximum photosynthesis rate (d-1)

• k_loss, Reference loss rate (d-1)

• BM_min, Threshold density for setting dBM/dt to zero (g dw m-2)

Temperature response of photosynthesis

• T_opt, Optimum growth temperature (deg C)

• T_min, Minimum growth temperature (deg C)

• T_max, Maximum growth temperature (deg C)

Temperature response of biomass loss rate

• Q10, Temperature coefficient (-)

• T_ref, Reference temperature for response=1 (°C)

Irradiance reponse of photosynthesis

• alpha, Slope of irradiance response (m2 d kJ-1)

• beta, Intercept of irradiance response (-)

Nutrient response of photosynthesis

• N_50, Half-saturation constant of Nitrogen (mg N L-1)

• P_50, Half-saturation constant of Phosphorus (mg P L-1)

Density dependence of photosynthesis

• BM_L, Carrying capacity (g dw m-2)

Concentration response (Toxicodynamics)

• EC50_int, Internal concentration resulting in 50% effect (mass per volume)

• E_max, Maximum inhibition (-)

• b, Slope parameter (-)

Internal concentration (Toxicokinetics)

• P, Permeability (cm d-1)

• r_A_DW, Area per dry-weight ratio (cm2 g-1)

• r_FW_DW, Fresh weight per dry weight ratio (-)

• r_FW_V, Fresh weight density (g cm-3)

• r_DW_FN Dry weight per frond ratio (g dw)

• K_pw, Partitioning coefficient plant:water (-)

• k_met, Metabolisation rate (d-1)

Model changes

• lemna version 1.0.2 The default value of parameter beta is set to 0.25. This reflects the changes made to the (upcoming) SETAC working group report version 1.2.

Value

named list

Functions

• param_new(): A parameter set without default values

References

Klein J., Cedergreen N., Heine S., Kehrein N., Reichenberger S., Rendal C., Schmitt W., Hommen U., 2022: Refined description of the Lemna TKTD growth model based on Schmitt et al. (2013) – equation system and default parameters, implementation in R. Report of the working group Lemna of the SETAC Europe Interest Group Effect Modeling. Version 1.1, uploaded on 09 May 2022. https://www.setac.org/group/effect-modeling.html

Examples

# Returns default model parameters, some parameters are not defined (NA)
param_defaults()

# Overwrite one of the default parameters
param_defaults(list(k_photo_max = 0.42))

# Provide values for substance specific TKTD parameters
param_defaults(list(
  EC50_int = 23, # 50% effect level (mass per volume)
  b = 1,         # slope parameter (-)
  P = 0.42       # permeability (cm d-1)
))

# Returns a list of required model parameters with all values set to NA
param_new()

lemna documentation built on April 3, 2025, 5:50 p.m.