Table 3.
Comparison of FOCUS approach and IDMM approach
| FOCUS approach | IDMM approach | |
|---|---|---|
| Models | FOCUS STEP 1.2 version 3.2 | IDMM model; version proposed in the context of the renewal approval of copper (EFSA, 2017) |
| Goal | Estimation of max. conc. in surface water and sediment | Long‐term accumulation in sediment |
| Item | Total concentration | Total concentration, dissolved concentration, free metal, complexed metal, labile metal, adsorbed labile metal, aged adsorbed metals |
| Entries routes to water bodies | Drift, run‐off/drainage/erosion |
Run‐off, drainage Drift not considered |
| Entries to soil | PPP application | Natural (geogenic) atmospheric deposition and anthropogenic atmospheric deposition, mineral fertiliser additions, PPP application |
| Loss of transition metals from soil compartment | Run‐off/drainage (transfers to surface water) |
Run‐off/drainage (transfers to surface water) Crops: copper removed from soil by uptake into harvestable parts of crops (annual time step) Leaching to soil deeper |
| Soil background concentration | Not considered | Estimated by model |
| Sediment background concentration | Manually implemented | Estimated by model |
| Modelling period | One year | Several years |
| Soil properties | – | FOCUS surface water (SW) scenarios, except for some parameters (pore water pH, dissolved organic carbon and major ion concentration, % organic matter content, water saturation) |
| Surface water definitions |
Static waterbodies water depth (cm): 30 Sediment depth(cm): 5 Effective sediment depth (cm): 1 Sediment OC (%): 5 Sediment bulk density (kg/L): 0.8 Surface water divided into two compartments: fractions ‘available’/‘unavailable’ for sorption |
Ditch and stream (pond not considered) FOCUS SW scenarios (scenarios D and R) Drainage‐based scenario: 2 soil layers (0–30 cm and 30 cm‐drain) Run‐off based scenario: 3 soil layers (0–5 cm, 5–30 cm, 30‐base of the soil profile); only the two‐first layers considered for run‐off FOCUS SW scenarios. Specific surface water characteristics were developed (pH, DOC, major cations) and AVS for sediment compartment |
| % run‐off/drainage | Default value (2–10%) | Annual fluxes of water considered from each soil layer to surface water or layer below |
| Drift value | Rautmann values (BBA) | – |
| DT50 in soil, surface water and sediment |
– Default value |
– Default value |
| Partitioning between water/sediment |
Based on Koc value 1/n not needed |
Speciation (WHAM model/Model VI) Based on Kd value Daily process |
| Partitioning between soil/pore water | – |
Speciation (WHAM model/Model VI) and ageing Daily process |
| Plant uptake factor | – | Once a year |
| Crop interception | 0% | – |
| Processes considered in soil compartment |
Degradation Daily process |
Degradation Speciation (WHAM model/Model VI) and ageing Soil erosion Daily process |
| Processes considered in sediment compartment |
Degradation Daily process |
Degradation Speciation (WHAM model/Model VI) Sediment erosion |
| Mitigation measures | – | Landscape and mitigation (2007) developed for organic compounds |