D2.6 - An improved SimpleBox model for improved environmental risk assessment and life cycle impact assessments

Project ID N°: 101036449 Call: H2020-LC-GD-2020-3 Topic: LC-GD-8-1-2020 - Innovative, systemic zero-pollution solutions to protect health, environment, and natural resources from persistent and mobile chemicals Preventing Recalcitrant Organic Mobile Industrial chemicalS for Circular Economy in the soil-sediment-water System Start date of the project: 1st November 2021 Duration: 42 months Main author: Joris Meesters Lead Beneficiary: RIVM Type of delivery: Demonstrator Dissemination Level: PU Filename and version: PROMISCES_D2-6_SimpleBox (version 2) Website: www.promisces.eu Due date: 30 April 2024 (M30) Date of revision: 07 September 2024 D2.6 - An improved SimpleBox model for improved environmental risk assessment and life cycle impact assessments D2.6 – An improved SimpleBox model 2 © European Union, 2024 No third-party textual or artistic material included on the publication without the copyright holder’s prior consent to further dissemination by other third parties. Reproduction is authorized provided the source is acknowledged Disclaimer The information and views set out in this report are those of the author(s) and do not necessarily reflect the official opinion of the European Union. Neither the European Union institutions and bodies nor any person acting on their behalf may be held responsible for the use which may be made of the information contained therein. D2.6 – An improved SimpleBox model 3 Document History This document has been through the following revisions: Authorisation Version date Author/Reviewer Description 0.1 March 14, 2024 Joris Meesters (RIVM)/ Stefan Jansen (Deltares) First draft for review 1.0 April 3, 2024 Joris Meesters (RIVM) Final Version for distribution 2.0 September 10, 2024 Joris Meesters Improved version after review EC History of changes: Executive summary, List of Tables and Figures and List of Abbreviations added Section 1.1, Ch. 3 added and Conclusion adapted to address reviewer comments Authorisation Name Status Date Review Stefan Jansen (Deltares) Project partner March 20, 2024 Validation Martine Bakker WP leader April 9, 2024 (version 1) September 13, 2024 (version 2) Approval Julie Lions Project Coordinator April 21, 2024 (version 1) September 13, 2024 (version 2) D2.6 – An improved SimpleBox model 4 Executive Summary Persistent, Mobile and Toxic (PMT) substances are of concern for organisms living in surface water bodies because of their indication of high (eco)toxicity in combination with high environmental persistence, due to poor removal from the water phase. Assessment of environmental persistence requires the use of multimedia chemical fate models such as SimpleBox, because these models are able to integrate the impact of substance properties, emission patterns and the dynamics of the environmental system over time. In the current deliverable report the environmental persistence is specified further into aquatic persistence, being the extent to which substances persist in surface water bodies. Just as for environmental persistence, the assessment of aquatic persistence needs the use of multimedia fate models to integrate the impact of the three factors mentioned above. To this end, the Aquatic Persistence Dashboard has been developed as an improvement of the SimpleBox model. At the end of the PROMISCES project the Simple Box version with the Dashboard will become publicly available at https://github.com/rivm-syso/SimpleBox. The Aquatic Persistence Dashboard enables the user to evaluate the time that a substance remains in the water phase and hence its tendency to flow downstream and eventually reach the ocean. SimpleBox simulates the degradation and transport as dynamic environmental fate processes occurring at regional, continental and global scale systems. By deriving aquatic persistence in this manner, these dynamic processes are integrated. The Aquatic Persistence Dashboard enables the user (exposure/risk assessor or policy maker) to screen the combined PMT properties of a substance as it directly indicates the timescale over which a chemical is anticipated to maintain in surface water bodies. The sensitivity analyses performed with the Aquatic Persistence Dashboard show that vapor pressure and air-water partitioning behavior of a substance can be of great impact on the aquatic persistence. However, these substance properties are currently not included as PM criterium. As such, it is possible that a volatile substance is defined as a PM substance as it fits the criteria, whereas in reality the substance resides in the atmosphere. The results of the sensitivity analyses thus shows the need to discuss whether vapor pressure or air-water partitioning coefficient should be considered a PM criterium as well. D2.6 – An improved SimpleBox model 5 Table of contents 1 Introduction ................................................................................................................................... 8 1.1 Introduction to this deliverable .............................................................................................. 8 1.2 Behaviour of PMT substances ................................................................................................. 8 1.3 SimpleBox .............................................................................................................................. 10 2 SB-AP Dashboard demonstration manual .................................................................................... 12 2.1 Opening version sheet .......................................................................................................... 12 2.2 Setting up the SB-AP Dashboard scenario and substance data in SimpleBox ...................... 12 2.3 Inserting values in the SB-AP Dashboard .............................................................................. 15 2.4 Iterated values for physicochemical parameters .................................................................. 16 2.5 Iterated values for aquatic persistence ................................................................................ 16 2.6 Run probabilistic sensitivity analysis ..................................................................................... 16 3 Using the SB-AP Dashboard in novel exposure assessments for better risk assessment ............. 18 3.1 Advancements in the SB-AP Dashboard ............................................................................... 18 3.1.1 Development of MS Excel macro ................................................................................... 18 3.1.2 Evaluation of acids and bases ........................................................................................ 18 3.1.3 Bioavailability of sorbed and dissolved chemical species ............................................. 18 3.2 Aquatic persistence as screening index for PM properties .................................................. 19 4 Conclusions .................................................................................................................................. 20 Annex I Simulation of aquatic persistence representing PM and vPvM criteria ................................. 22 D2.6 – An improved SimpleBox model 6 List of tables Table 1. Calculated aquatic persistences representing PM and vPvM criteria – pp 19 List of figures Figure 1. Difference between PM and not-PM substance in aquatic fate and concentrations – pp 9 Figure 2. Visualization of the SimpleBox model – pp 10 Figure 3. Screenshot of the opening sheet of SimpleBox version that included SB-AP Dashboard with 1: Description of the SimpleBox version, 2: added SB-AP added to the modifications log, 3: opening ‘version’ tab of the SB-AP Dashboard spreadsheet – pp 12 Figure 4. Rows 1 to 9 of SB’s Input tab – pp 13 Figure 5. SB user input cells in the input tab that need to remain blank – pp 14 Figure 6. A part of the SB-AP Dashboard – pp 15 Figure 7. The SB-AP-Probabilistic Sensitivity Analysis data tab – pp 16 Figure 8. The SB-AP PSA Graphs tab – pp 17 D2.6 – An improved SimpleBox model 7 List of Abbreviations Σe environment The sum of all emissions into the environment Σmenvironment The sum of all chemical mass present in the environment Σmwater The sum of all chemical mass present in water bodies 𝐴𝐴 Fate matrix ChemRowNr Chemical Row Number CS Case study 𝑒𝑒 Emission vector ECHA European Chemical Agency EUSES European Union System for the Evaluation of Substances foc Organic carbon content FRorig Fraction of original species Kaw Air-water partitioning coefficient Kaw arctic Air-water partitioning coefficient in the arctic system Kaw regional Air-water partitioning coefficient in the regional scale system Kaw tropic Air-water partitioning coefficient in the tropic scale system kdeg air Degradation rate constant in air k deg sed Degradation rate constant in sediments kdeg soil Degradation rate constant in soil kdeg water Degradation rate constant in water Koc Organic carbon-water partitioning coefficient Kow Octanol-water partitioning coefficient 𝑚𝑚 Environmental load M Mobility OECD Organisation for Economic Co-operation and Developmen P Persistence Paq Aquatic Persistence pHw Acidity of the water medium pKa Dissociation constant Pov Overall environmental persistence PM Persistent and Mobile PMT Persistent Mobile and Toxic PROMISCES Preventing Recalcitrant Organic Mobile Industrial chemicalS for Circular Economy in the soil-sediment-water System PSA Probabilistic Sensitivity Analysis REACH Registration, Evaluation, Authorisation and Restriction of Chemicals SB SimpleBox SB-AP Dashboard SimpleBox Aquatic Persistence Dashboard vPvM Very Persistent and very Mobile WP Work Package D2.6 – An improved SimpleBox model 8 1 Introduction 1.1 Introduction to this deliverable Substances that are well soluble, but hardly volatile, barely degradable and have a small tendency to sorb to organic carbon may stay in the aquatic environment as persistent and mobile (PM) substances. Consequently, aquatic organisms can be exposed to PM substances for a long time, which can lead to undesirable effects once ecotoxicological threshold concentrations are exceeded. In the context of the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) the persistence (P) and mobility (M) of a substance are currently evaluated using separate indexes based on the (bio)degradation half-life and the organic carbon-water partitioning coefficient (EC, 2022). Although the separate indexes are of great significance, the combined effect of P and M, determining the time that a substance remains bioavailable in water bodies, is a factor of importance as well. In the PROMISCES project, we have introduced the term aquatic persistence for this substance property. In the current evaluation system procedure of PMT substances under REACH, aquatic persistence is not explicitly assessed. This is an omission, since aquatic persistence is crucial for the exposure and risk of substances to aquatic organisms. In this deliverable we studied aquatic persistence of substances and implemented an equation for this property in the existing multimedia fate model SimpleBox (SB) (rivm.nl/simplebox, 2024). The SimpleBox model is prescribed for chemical safety assessment within REACH (ECHA, 2012) and EUSES. In the current task, the model has been improved by extending it with the SimpleBox Aquatic Persistence Dashboard (SB-AP Dashboard). This dashboard simulates the time a substance resides in a water body based on its substance properties (solubility, vapor pressure, octanol-water partitioning coefficient), (bio)degradation rate, emission patterns and characteristics of the water bodies such as depth, volume, suspended matter concentration and water flow rates. The SB-AP Dashboard enables its users, e.g. exposure/risk assessors or policy makers, to evaluate the combined impact of a substance’s P and M as well as the environmental fate processes that influence the time a substance remains bioavailable in water bodies (e.g. volatilization and advective transport via flowing water). The development of the SB-AP Dashboard proceeded parallel to a series of case studies in the PROMISCES project, in which the fate and transport of PMT substances is evaluated in different local environments. Examples are the interaction between groundwater and soil, river bank filtration, urban settings, and upstream catchments by using models such as Hydrus (Simunek et al., 2012) and Modflow (USGS, 2024). These fate and transport models include routines to simulate the evaporation of substances. However, the extent to which a substance is prone to volatilization is currently not included as a PMT criterion. Therefore, we developed the SB-AP Dashboard which evaluates the potential for volatilization. This is performed by expressing the aquatic persistence by including vapor pressure and solubility as input parameter and plotting air-water partitioning behavior against aquatic persistence. The aim of this exercise is to study the potential impact of volatilization as a fate process removing PMTs from water bodies. 1.2 Behaviour of PMT substances PM substances with low ecotoxicological thresholds are considered Persistent Mobile and Toxic (PMT). The higher ecotoxicological threshold concentrations of less toxic substances may be D2.6 – An improved SimpleBox model 9 exceeded nonetheless for very Persistent and very Mobile (vPvM) substances, because higher exposure concentrations can be reached over time. In that case, the fate processes that remove these substance from water, e.g. biodegradation, carbon sorption and evaporation, are slow. Figure 1. Difference between PM and not-PM substance in aquatic fate and concentrations The potential of a chemical for leading to an exposure burden that will continue into the future time or be displaced to remote regions can be screened and assessed with the so called overall environmental persistence (Webster et al., 1998; OECD, 2004). Overall environmental persistence (Pov in s) of chemical emissions is estimated as the sum of all chemical mass present in the environment (Σmenvironment in g) divided by the sum of all emissions into the environment (Σeenvironment in g.s-1). 𝑃𝑃 𝑜𝑜𝑜𝑜 =∑𝑚𝑚𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 ∑𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 (1) The considered (v)P(v)M substances mainly reside in aqueous media, whereas overall persistence also covers other environmental compartments such as the atmosphere and soil. Aquatic persistence (Paq) is therefore introduced in WP 2.4 as a component of the overall persistence in order to be able to focus on the potential exposure burden of aquatic organisms to (v)P(v)M substances that persist and displace in water bodies. Aquatic persistence (Paq in s) is expressed as the sum of all chemical mass present in water bodies (Σmwater in g) divided by the sum of the emissions to water (Σewater in g.s-1). 𝑃𝑃 𝑎𝑎𝑎𝑎 =∑𝑚𝑚𝑤𝑤𝑤𝑤𝑒𝑒𝑒𝑒𝑒𝑒 ∑𝑒𝑒𝑤𝑤𝑤𝑤𝑒𝑒𝑒𝑒𝑒𝑒 (2) Overall environmental persistence is not acknowledged as an intrinsic substance property, but as a combination of joint properties of chemical pollutants, their emission patterns, and the characteristics of the environment (OECD, 2004). Consequentially, overall persistence cannot be assessed directly from information about the chemical and/or from emission data only. Therefore, multimedia chemical fate models are used for such assessment (OECD, 2004). This also applies for the aquatic persistence of (v)P(v)M substance emissions, because their tendency to persist and displace in aquatic environments is difficult to characterize. It depends on a variety of substance properties such as vapour pressure, solubility, octanol-water partition coefficient, and degradation half-life as well as at what type of water body the emission takes place, e.g. slowly streaming lake waters or rapidly running river water. Therefore, a new tool to express and evaluate aquatic D2.6 – An improved SimpleBox model 16 2.4 Iterated values for physicochemical parameters The ‘physicochemical parameters’ table (cells B24:D28) displays parameter values for the temperature dependent air-water partitioning coefficients at regional (Kaw regional), tropic (Kaw tropic) and arctic scale (Kaw arctic) and the organic carbon-water coefficient (Koc) derived from the inserted octanol-water partitioning coefficient (Kow) as calculated by the SB model based on the selected chemical substance properties (cells H3: 12). 2.5 Iterated values for aquatic persistence The SB-AP Dashboard directly delivers the aquatic persistence calculated from the substance data and emission volumes as given in the ‘Selected’ values (cells H3:22). There are six different aquatic persistence values calculated, because both the total and dissolved chemical load is estimated for the water compartments at the regional, continental and global scale (cells B35:F42). The ‘aquatic persistence (sorbed + dissolved)’ table refers to the presence of chemical that is sorbed to organic carbon in suspended matter and the chemical dissolved in the water phase, whereas the ‘aquatic persistence (dissolved only)’ table refers to presence of chemical dissolved in the water phase only. Aquatic persistence is expressed in unit of time to express the extent to which (v)P(v)Ms reside in water compartment. The units of time given here are in seconds, days, months and years, because the predicted aquatic persistence for different substances may differ in orders of magnitude. 2.6 Run probabilistic sensitivity analysis Pressing the button ‘run probabilistic sensitivity analysis’ starts a Microsoft Excel Macro that draws 10,000 iterations. Per iteration the spreadsheet model (i) randomly selects a value between the minimum and maximum of the probabilistic uniform distribution range for each chemical substance property and emission volume indicated with the letter P and (ii) calculates values for the physicochemical properties and aquatic persistence of dissolved only and sorbed plus dissolved chemicals at the regional, continental and global scale. The selected input values, iterated parameter values and calculated aquatic persistence values are written down in the ‘SB-AP-PSA data’ tab (a part of which is shown Figure 7), which stands for SimpleBox –Aquatic Persistence – Probabilistic Sensitivity Analysis (SB-AP-PSA). Figure 7. A part of the SB-AP-Probabilistic Sensitivity Analysis data tab. D2.6 – An improved SimpleBox model 17 The ‘SB-AP-PSA data’ tab includes 10,000 rows of iterations for which the selected values for molecular weight, vapour pressure (Vap 25), solubility, octanol-water partitioning coefficient (Kow) the pKa and the degradation rate constant in air (kdegair), water(kdegwater), sediment (kdegsed) and soil (kdegsoil) are given as well as the calculated air-water and organic carbon -water partitioning coefficient (KOC) and the aquatic persistence of total and dissolved chemical in water compartments at the regional, continental and global scale. The simulation data in the ‘SB-AP-PSA data’ tab is the data source for the graphs in the ‘SB-AP Graphs’ tab (Figure 6). Figure 8. The SB-AP PSA Graphs tab The ‘SB-AP Graphs’ tab (Figure 8) displays six scatter plot graphs in which the aquatic persistence of ‘dissolved’ or ‘sorbed + dissolved’ chemicals are on the y-axes. The x-axes refer to inserted ranges for rate constants for degradation in water, calculated air-water partitioning coefficient (Kaw) or inserted octanol-water partitioning coefficients (Kow). D2.6 – An improved SimpleBox model 18 3 Using the SB-AP Dashboard in novel exposure assessments for better risk assessment The SB-AP Dashboard is a novel tool in the exposure assessment of PM(T) substances. This chapter explains how exposure assessors can use it for policy implications (Section 3.2). A number of advancements to the SB-AP Dashboard were made to make the tool fully operational for this purpose. These are described below. 3.1 Advancements in the SB-AP Dashboard Several advancements have been made to the SB-AP Dashboard since the first model runs of a prototype version have been presented, such as the development of a MS Excel macro and the possibility to evaluate acids and bases as well as the bioavailability of sorbed and dissolved chemical species. 3.1.1 Development of MS Excel macro The SB-AP Dashboard (available after the end of the project at https://github.com/rivmsyso/SimpleBox) has been optimized for MS Excel users as it no longer requires the licensed software add-in of @RISK (Lumivero, 2024). The @RISK software add-in has been replaced with a MS Excel Macro that runs probabilistic sensitivity analyses (Figure 6). Replacing the @RISK software add-in with the MS Excel macro has made the SB-AP Dashboard more user friendly as it is no longer required to install and get acquainted with @RISK. Instead, the user directly enters input values as described in section 2.3. Furthermore, the MS Excel macro directly delivers a datasheet (Figure 7) that comprises all simulated data. 3.1.2 Evaluation of acids and bases The earlier versions of the SB-AP Dahsboard only included the possibility of evaluating substances that occur in the environment in a neutral form, excluding the evaluation of acids and bases. For this reason, the SB-AP Dashboard has been extended with routines to simulate acidic and basic substances (Figure 4) and an input field to insert values the dissociation constant (pKa) as substance property (Figure 6). 3.1.3 Bioavailability of sorbed and dissolved chemical species Chemical substances in water bodies are considered bioavailable when they are actually dissolved in water and not sorbed to the organic carbon in suspended matter. Exposure estimation should thus account for the extent to which a chemical substance occurs as sorbed or dissolved species (ECHA REACH R.16). The earlier versions of the SB-AP Dashboard only delivered results for the sum of the dissolved and sorbed species. As such, the relatively large impact of Kow on bioavailability was neglected. The latest version of the SB-AP Dashboard delivers results for both dissolved and summed species, so that the user can include the impact of bioavailability in its exposure assessment exercise. The paragraph below describes how the dissolved and sorbed species are calculated in the model. The Koc of a substance refers to the ratio between the concentration sorbed to organic carbon and the concentration dissolved in water. SB calculates Koc s as the product of the substance’s Kow and the organic carbon content (foc) in the suspended matter ( Koc = foc ×Kow). As such, dissolved substances with high Kow are effectively sorbed by the organic carbon in suspended matter. The D2.6 – An improved SimpleBox model 19 impact of the Kow on the sum of dissolved and sorbed chemical species is relatively small compared to the impact on dissolved species only (Figure 6). The process of sorption to suspended particles directly reduces the presence of dissolved chemical species in the water columns. The sorbed species are only indirectly removed from the water column, because the suspended particles to which the chemical is sorbed settle to the sediments at the bottom. Hence, the impact of high Kow is relatively large for the aquatic persistence of the bioavailable dissolved chemical species only, but small for the summed species. Application of the SB-AP Dashboard in environmental risk assessment 3.2 Aquatic persistence as screening index for PM properties Aquatic persistence (Paq) is introduced in the current deliverable as a component of the overall persistence in order to focus on the potential exposure burden of aquatic organisms to (v)P(v)M substances that persist and displace in water bodies. The SB-AP Dashboard is a tool developed to express the aquatic persistence of chemical substances in water bodies. As such, it can be used in a similar manner as existing model tools developed for overall persistence and long range transport potential, but with a focus on the water compartments. Overall persistence tools have proven to be useful in chemical risk assessment in the identification and evaluation of persistent organic pollutants and the understanding of their environmental fate (Wegmann et al., 2009). Just as for overall environmental persistence, the assessment of aquatic persistence needs the use of multimedia fate models to integrate the impact of the substance properties, emission patterns and landscape characteristics. The SB-AP Dashboard enables environmental exposure assessors to evaluate the time that a substance remains in the water phase and hence its tendency to flow downstream and eventually reach the ocean. SB simulates the degradation and transport as dynamic environmental fate processes occurring at regional, continental and global scale systems. Such dynamics are integrated in the way aquatic persistence is derived. The SB-AP Dashboard is a tool to screen the PMT properties of a substance as it directly indicates the timescale over which a chemical is anticipated to maintain in surface water bodies. Such screening supports decision making as substances can be identified to be PM in case the calculated aquatic persistence for the substance of interest is higher than the aquatic persistence calculated for substances representing the current PM or vPvM criteria (Table 1). In Annex I it is documented how the PM and vPvM criteria are translated into input values for the SB-AP Dashboard. Table 1. Calculated aquatic persistences representing PM and vPvM criteria* Aquatic persistence of PM substance Aquatic persistence of vPvM substances Scale Dissolved species only Sorbed + dissolved species Dissolved species only Sorbed + dissolved species Regional > 131 days > 131 days >187 days > 187 days Continental > 137 days > 137 days >203 days > 203 days Global > 140 days > 140 days > 215 days > 215 days * See annex I for derivation of aquatic persistence of substances representing PM and vPvM criteria Moreover, the SB-AP Dashboard provides the user the opportunity to insert input values as ranges which can quantify uncertainty. The calculated Probabilistic Sensitivity Analysis graphs (Figure 8) and D2.6 – An improved SimpleBox model 20 data (Figure 7) resulting from such input ranges can then be used to evaluate the level of uncertainty in the aquatic persistence of a substance. 4 Conclusions This deliverable report presents the SimpleBox Aquatic Persistence Dashboard (SB-AP Dashboard) developed within the PROMISCES project as a tool to evaluate the aquatic persistence of chemical substance emissions to surface waters. The SB-AP Dashboard, at the end of the project available at https://github.com/rivm-syso/SimpleBox, provides model users (e.g. risk assessors and policy makers) with the opportunity to directly gain insight into the combined effect of P and M, being the time a substance resides in the water phase (i.e. aquatic persistence). An application of the Dashboard is the comparison of the aquatic persistence of a specific substance to that of substances with properties corresponding with PM and vPvM criteria, for different scales (regional, continental, global). The fate and transport models used in the PROMISCES case studies contain routines to simulate the volatilization of substances. Nevertheless this transport process removing substances from soil or water is not reflected in the current PM criteria. Thus, the impact of volatilization on the presence of PM in aqueous media demanded further investigation. The SB-AP Dashboard was applied in a dedicated fate modeling study to investigate the impact of air-water partitioning behavior (driven by volatilization and solution behavior of a substance) on aquatic persistence. The sensitivity analyses demonstrate an linearly increasing trend of aquatic persistence with decreasing air-water partitioning coefficients smaller than 100. Consequentially, volatile substances suitable to be considered PM because of their low KOC and slow (bio)degradation can nonetheless still effectively be removed from water via volatilization leading to low aquatic persistence. SimpleBox, as well as the fate and transport models used in the PROMISCES case studies, do contain model routines to account for volatilization. Hence, it is concluded that including volatilization in the evaluation of PM substances is a feasible effort. With the SB-AP Dashboard risk assessors and/or policy makers are able to include the volatilization of a suspected PM substance in prioritizing exercises for PM substances. D2.6 – An improved SimpleBox model 21 References [EC] European Commision. 2022. ANNEXES to the Commission Delegated Regulation amending Regulation (EC) No 1272/2008 as regards hazard classes and criteria for the classification, labelling and packaging of substances and mixtures. Brussels, 19.12.2022 C(2022) 9383 final [ECHA] European Chemicals Agency. 2012. Guidance on information requirements and chemical safety assessment Chapter R.16: Environmental Exposure Estimation. Version: 2.1 October 2012 Lumivero 2024. Probabilistic Risk Analysis in Excel. https://lumivero.com/products/at-risk/ Consulted online August 2024. [OECD] Organisation for Economic Co-operation and Development. 2004. Guidance document on the use of multimedia models for estimating overall environmental persistance and long-range transport. ENV/JM/MONO(2004)5 rivm.nl/simplebox 2024. SimpleBox Consulted online February 2024 Simunek J, van Genuchten M Th, Sejna M. 2012 HYDRUS: model use, calibration, and validation. Transactions of the American Society of Agricultural Engineers, 2012, 55, 1261-1274 DOI: 10.13031/2013.42239 Schoorl M, Hollander A, Van de Meent D. 2015. SimpleBox 4.0 A multimedia mass balance model for evaluating the fate of chemical substances. RIVM Report 2015-0161 [USGS] United States Geological Survey. 2024. MODFLOW and Related Programs. https://www.usgs.gov/mission-areas/water-resources/science/modflow-and-related-programs consulted online September 2024 Webster E, Mackay D, Wania F. 1998. Evaluating environmental persistence. Environmental Toxicology & Chemistry, 1998, 17, 2148-2158 Wegmann F, Cavin L, MacLeod M, Scheringer M, Hungerbühler K. 2009. The OECD software tool for screening chemicals for persistence and long-range transport potential. Environmental Modelling & Software , 2009, 24, 228–237 D2.6 – An improved SimpleBox model 22 Annex I Simulation of aquatic persistence representing PM and vPvM criteria Here it is explained how the SB-AP Dashboard can be used to screen and index the aquatic persistence of a substance emission, by comparing it to aquatic persistence values the SB-AP Dashboard yields when the PM or vPvM criteria (EC, 2022) are inserted as input values (Table 1). Currently, a substance is proposed to be persistent if it meets one of the following criteria (EC, 2022): i) the degradation half-life in marine water (at 9˚C) is higher than 60 days ii) the degradation half-life in fresh or estuarine water at (12 ˚C) is 40 days iii) the degradation half-life in marine sediment (at 9˚C) is higher than 180 days iv) the degradation half-life in fresh or estuarine water sediment (at 12˚C) is higher than 120 days v) the degradation half-life in soil (at 12 ˚C ) is higher than 120 days A substance is proposed to be very persistent (vP) if it meets one of the following criteria (EC, 2022) i) the degradation half-life in marine, fresh or estuarine water is higher than 60 days ii) the degradation half-life in marine, fresh or estuarine water sediment is higher than 180 days iii) the degradation half-life in soil is higher than 180 days. A substance shall be considered to fulfil the mobility criterion (M) when the log Koc is less than 3 (EC, 2022) and a substance shall be considered to fulfil the ‘very mobile’ criterion (vM) when the log Koc is less than 2. The half-life values ( t1/2 ) in persistence criteria are translated values for the input fields of the SB4.0 that refer to degradation rate constants in water, sediment and soil as: 𝑘𝑘𝑎𝑎𝑒𝑒𝑜𝑜 = −ln (1 2) 𝑡𝑡1/2 The Koc of a substance is included in SB as the product of the KOW and the organic carbon content of the natural solid matter (fOC) that is included in SB4.0 as parameter values characterising the environmental system with mass percentages of 2% for soil, 5% for sediments and 10% for the suspended particles in water compartments. 𝐾𝐾𝑂𝑂𝑂𝑂 =𝑓𝑓 𝑂𝑂𝑂𝑂 ×𝐾𝐾𝑂𝑂𝑂𝑂 Here, the KOC is calculated for the suspended particles in the water compartments, because aquatic persistency refers to the time a substances resides in surface water bodies. D2.6 – An improved SimpleBox model 23 Table A1.1 Inserted values in SB-AP Dashboard to derive aquatic persistence matching PM and vPM criteria SB-AP Dashboard input field Inserted value to derive PM index Inserted value to derive vPvM index Unit Molecular weight A 10,000 10,000 g/mol Vapor pressure A 10 7 10 7 Pa Solubility A 10 8 10 8 mg/l pKa 7 7 [-] KOW B 10 4 10 3 [-] k degwater 2 10 -7 1.34 10 -7 s -1 k degsed 6.7 10 -8 4.46 10 - 8 s -1 kdegsoil 6.7 10 -8 4.46 10 - 8 s -1 A: a maximum value is inserted as the substance property is not include as PM or vPvM criterium B: pKa is set to 7 to represent a default neutral substance C: calculated as KOW = KOC / fOC with fOC = 10% D: calculated as kdeg = -ln(1/2) / t1/2