For 17 VPs of potential concern in the Netherlands, we assessed sources and emission due to animal slurry applications to soil. Hence, we examined the use of VPs in four livestock sectors in the Netherlands for 2015–2018, and quantified animal excretion rates and dissipation during slurry storage. For almost all VPs, administrated quantities to the animals during the period 2015–2018 decreased. VP concentrations during a storage period of six months could decrease between 10 and 98% depending on the compound. Predicted concentrations of VPs in slurries after storage compared well with measured concentrations in the literature. Based on the storage model outcomes, we developed a residue indicator, that quantifies the potential for residues in applied slurry. This indicator agrees well with the most frequently detected VPs in the Dutch slurries, and is therefore useful to prioritize measures aiming at reducing VP emissions into the environment.

Publication details are available on https://doi.org/10.1016/j.scitotenv.2022.152938

The sub-project “Integration” deals with coupling contaminants of emerging concerns (CECs) emission sources from rural and urban areas into rivers. Rural area sources are considered diffuse sources mainly originated from manure dispersed on lands, while urban area sources are considered as point sources from waste water treatment plants (WWTPs). Figure 1 provides the full flowchart of CEC's in the SUSPECt project.

The goal is to provide spatial and temporal hazard information for risk assessment and management, predicting the concentration of CECs in rivers at Dutch country scale.

Figure 1 - the flowchart of CEC's flow in the SUSPECt project.

 To integrate the rural and urban routes, we selected the Landelijk Waterkwaliteitsmodel - LWKM 2.4 (WEnR/Deltares, 2019), a water quality model tool which relies on the national hydrological model Landelijk Hydrologisch Model – LHM 4.0 (Deltares, 2019). The main model output is the seasonal contaminant concentration due to diffuse and point sources.

We have selected the Eem River basin in the Velue een Vallei water board as a test area (Figure 2). However, the methodology will be applicable elsewhere in the Netherlands. An overview of the river network, WWTPs and monitoring and measurement points is depicted in figure 2. 

Figure 2 - The Eem Basin test area and the available information on water infrastructures and measurements.

 We run a test with fipronil as tracer compound. We took the hydrological year 2015, a urban constant source of fipronil along the year and a seasonally variable source of fipronil from rural areas. We assumed that Spring and Summer have double crop effluent concentration with respect to Winter and Fall. This is because manure and pesticides are mostly applied in spring and summer. Results per seasons are reported in figures 3, while figure 4 shows the mean tracer concentration for 2015. This exercise has been done in order to preliminary test the selected model methodology and show its capability with a tracer compound. The fipronil consumption input was arbitrary and the resulting concentrations depicted in figures 3 and 4 do not reflect a validated prediction.