Windermere Humic Aqueous Model (WHAM) including WHAM Freshwater Toxicity (WHAM-FTOX) version and Parsimonious Speciation of Metals in soils (POSSMs)
The WHAM family of models predict the forms of metals present in soil and water. They simulate chemical reactions that occur when metals enter soil and water systems; particularly how metals bind to humic substances, the most dominant form of non-living organic matter in terrestrial and aquatic environments. The models are used for environmental risk assessment: (1) to understand the behaviour of metals in soil and water, and what controls their solubility; and (2) to predict how metal chemistry influences their toxicity to living organisms in soil and water.
WHAM is a mechanistic chemistry process model. Given the chemical composition of a water or soil, WHAM predicts the amounts of each chemical species of metals present. Metal speciation controls fate in the environment, for example the distribution of a metal between solids and porewater in a soil or sediment. Hence WHAM includes a solution speciation model as well as sub-models for ion binding to: humic and fulvic acids; clay; oxides of iron, aluminium, manganese and silicon.
The WHAM-FTOX version predicts the toxic effects of mixtures of metals and acidity in freshwaters.
POSSMs computes a simplified distribution of metal forms in soil using a minimal input dataset, making it useful for application where the relatively large data requirements of WHAM cannot be met (eg large scale soil surveys).
WHAM is also used as the chemical component in other models that predict how water chemistry affects the toxicity of metals to aquatic organisms, such as the freely available Biotic Ligand Model (BLM): such models are widely used for research and metal risk assessment.
WHAM was originally developed in 1994 by Ed Tipping from earlier, simpler models. Subsequent upgrades improved the predictive capability of the model and expanded the number of metals to which it can be applied (currently more than 40): WHAM-Model V (1994); WHAM-Model VI (2002); WHAM-Model VII (2011).
The WHAM family of models were developed by UKCEH.
WHAM is available to use via a licence purchase (see weblink). Income from licence sales contributes to ongoing development and support of the software.
POSSMs is available at no cost as an Excel add-in.
Development of WHAM was funded by: UKRI-NERC National Capability and research grants; International Copper Association (ICA); International Council on Mining and Minerals (ICMM); International Lead Zinc Research Organization (ILZRO); Nickel Producers Environmental Research Association (NiPERA); Cobalt Development Institute (CDI); Rio Tinto Minerals; International Chromium Development Association (ICDA); International Molybdenum Association (IMOA); European Aluminium Association (EAA).
POSSMs development was funded by UKRI-NERC National Capability: UK-SCAPE programme (SPEED project).
WHAM is used by UKCEH and researchers at more than 100 labs around the world for metal risk assessment (including UK Health and Safety Executive REACH: registration, evaluation, authorisation and restriction of chemicals).