Method

SimpleBox4nano is based on the SimpleBox model and simulates the specific environmental behaviours of nanomaterials. The main adaptation consists of adding three particulate chemical species to the dissolved species already included in SimpleBox. The three particulate chemical species consist of: i) the emitted nanomaterial, ii) smaller heteroagglomerates (<450 nm) consisting of nanomaterial and natural colloids or aerosols, and iii) bigger heteroagglomerates (>450 nm) consisting of nanomaterials and other particulates found in air, water and soil

Just like SimpleBox, it is a first-principles model, in the sense that it derives mass flow rates taking into account both physical and chemical substance properties and characteristics of the environment modelled. It takes user-specified release rates of the chemical into the environment as input, and produces exposure concentrations in the different compartments of the environment as output. This type of model is known as a ‘Mackay model’, after its inventor, Donald Mackay.

Model code

SimpleBox is operated as Microsoft Excel spreadsheet for calculating steady state concentrations. Supported by numerical computations in R a dynamic analysis can be performed and time specific concentrations calculated. Documentation on the SimpleBox4nano model concept is described in various publications[1,2,3].

Framework

SimpleBox has served as 'regional distribution module' in the European Union System for the Evaluation of Substances (EUSES). The tool for conventional substances is currently used as part of the CHESAR tool, hosted by the European Chemicals Agency [4] to demonstrate possibilities for 'safe use' of chemicals, which is required for registration of chemical substances under REACH. SimpleBox and SimpleBox4nano also serves as fate module in Life Cycle Impact Assessment models [5,6].

Designed originally as a research tool, SimpleBox has proven most useful in dedicated environmental fate studies, focused at understanding and predicting environmental fate from fundamental physical and chemical substance properties. An proof of concept SimpleBox4nano R package was developed for research purposes.

Availability

The SimpleBox4nano spreadsheet model, the supporting R-tools and its documentation files are freely available. It is available for download from https://github.com/rivm-syso/SimpleBox/tree/xl4nano_version 
For more information: simplebox@rivm.nl.