EFSA: sediments from 30 ditches, streams and ponds next to arable fields for the FOCUS scenarios — 20 cores each, layers 0–2, 2–5 and 5–10 cm, bulk density, porosity and organic matter instead of a single description with 5% organic carbon
On 9 November 2026 EFSA published the report of project EFSA/2024/OP/0005 on the properties of bed sediments in small edge-of-field waterbodies, which in the EU FOCUS scenarios are used to calculate the exposure of aquatic organisms to pesticides. Today the sediment of all scenarios has the same properties, including a relatively low organic carbon content of 5%, which according to the authors leads to an underestimation of the exposure in sediment.
- The FOCUS surface water scenarios comprise fifteen small edge-of-field waterbodies — ditches, streams and ponds — that represent the major EU agricultural areas. All of them have the same sediment description; the low organic carbon content (5%) underestimates the exposure in sediment and may therefore underestimate risks for sediment-dwelling organisms.
- The authors carried out a targeted literature search and a sampling campaign of freshwater sediments. The waterbodies were selected in the vicinity of the existing scenario locations.
- Sediment was sampled from 30 waterbodies: 20 cores from each, divided into the layers 0–2, 2–5 and 5–10 cm. Bulk density, porosity and organic matter content were determined.
- Of 22 selected publications, only one study — on four ditches in the Netherlands — was considered relevant. In the results of the campaign, the sediment properties showed no systematic difference by waterbody type or by regulatory zone.
- In 22 of the 30 waterbodies, stones hindered the interpretation of the measurements. The properties were determined assuming homogeneous sediment (without separating the stones), and the report gives a second way — excluding the stone part; the authors recommend comparing both and using the sediment penetration factor defined in the study when selecting a parameterisation.
- The results are intended to allow a more detailed description of the sediment in the scenarios and a more realistic (or more conservative) risk assessment for sediment-dwelling organisms in the registration of plant protection products. For a laboratory testing sediments, what matters is core sampling by layers, the determination of bulk density, porosity and organic matter, and how stones are handled; the report summary does not give the determination methods.