Multimedia fugacity model

Multimedia fugacity model is a model that summarises the processes controlling the chemical behaviour in the complex assembly of environmental media through quantitative accounting of chemicals input and output by developing and applying of mathematical statements or “models” of chemical fate.^[1]

Some chemicals have the potential to migrate from the medium to medium, reaching unexpectedly high concentrations. To study and predicate the behaviour of chemicals in the different environmental compartments the Multimedia Fugacity Model concept has been introduced.^[2][1]

The models are formulated using the concept of fugacity, which was introduced by G.N. Lewis in 1901 as a criterion of equilibrium and convenient method of calculating multimedia equilibrium partitioning. The fugacity of chemicals is a quantity describing mathematically the rates at which chemicals diffuse, or are transported between phases. The transfer rate is proportional to the fugacity difference that exists between the source and destination phases. For building the model the important strategy is to set up a mass balance equation for a number of phases in question where from fugacities, concentrations, fluxes and amounts are deduced. The important values are the proportionality constant, called fugacity capacity expressed as Z-values (SI Unit: mol/m3 Pa) for a variety of media, and transport parameters expressed as D-values (SI unit: mol/Pa h) for processes such as advection, reaction and intermedia transport. The Z-values are calculated using equilibrium partitioning coefficients of the chemicals, Henry's law constant and other related physical-chemical properties.^[1][3]

Application of Models

There are four levels of Multimedia Fugacity Models applied for prediction of fate and transport of organic chemicals in the multicompartmental environment.^[1][4][5] Depending on the number of phases and complexity of processes different level models are applied. Many of the models apply to steady-state conditions and can be reformulated to describe time-varying conditions by using differential equations. The concept has been used to assess the relative propensity for chemicals to transform from temperate zones and “condense out” at the polar regions. The multicompartmental approach has been applied to the “quantitative water air sediment interaction" or "QWASI" model designed to assist in understanding chemical fate in lakes.^[6] Another application found in POPCYCLING-BALTIC model, which is describing fate of persistent organic pollutants in Baltic region.^[7]

References

1. ^ ^{a b c d} Mackay, Donald (2001). Multimedia Environmental Models. Lewis Publishers. ISBN 1-566-70542-8. http://books.google.com/books?id=f37zywrLJf0C&printsec=frontcover&dq=Multimedia+Environmental+Models&hl=en&src=bmrr&ei=P8TnTdihLcnFgAfN75j2Cg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCoQ6AEwAA#v=onepage&q&f=false. Retrieved 2 June, 2011. 
2. ^ Mackay, D; Wania, Frank (1999). The evolution of mass balance models of persistent organic pollutant fate in the environment. Environmental Pollution. 100. pp. 223–240. 
3. ^ Mackay, Donald; Shiu, Wan Ying Shiu; Ma, Kuo Ching (2000). Physical-Chemical Properties and Environmental Fate and Degradation Handbook. Boca Raton, FL: CRC Press. ISBN 1-566-70255-0. http://books.google.com/books?id=22zhOfXJ444C&dq=Physical-Chemical+Properties+and+Environmental+Fate+and+Degradation+Handbook&source=gbs_navlinks_s. Retrieved 2 June, 2011. 
4. ^ Mackay, Donald; Paterson, S (1991). . Evaluating the multimedia fate of organic chemicals. A level III fugacity model. Environmental Science and Technology. pp. 25; 427–436. 
5. ^ Mackay, Donald; Shiu, Wan Ying Shiu; Paterson, S. (1992). Generic Models for evaluating the regional fate of chemicals. Chemosphere. 24. pp. 695–717. 
6. ^ "The Canadian Centre for Environmental Modelling and Chemistry. QWASI Model of Chemical Fate in Lakes". http://www.trentu.ca/academic/aminss/envmodel/models/Qwasi.html. Retrieved 2 June 2011. 
7. ^ "The Canadian Centre for Environmental Modelling and Chemistry. Wania Models". http://www.trentu.ca/academic/aminss/envmodel/models/Wania.html. Retrieved 2 June 2011. 

Further reading

Frank Wania and Donald Mackay (1993). Modelling the global distribution of toxaphene: A discussion of feasibility and desirability. Chemosphere, Vol.27