Properties of Chemicals That Influence Their Fate in the Gross Environment

1 PROPERTIES OF CHEMICALS THAT INFLUENCE THEIR FATE IN THE GROSS ENVIRONMENT 

Much of the earth s surface is water, and an important aspect of the volatilization of pollutants is their movement from water to air. The movement of solutes between water and air is governed by Henry s law, which states that at equilibrium, the concentration of a chemical in the vapor state bears a constant relationship to the concentration in aqueous solution. 

This equation can be simplified to give H = P/S, where H is now Henry s law constant, which has dimensions of atm mVmole. Values for H may be calculated or measured (Mackay et al. 1979), and are now widely used infugacity modeling (see Section 3.2). 

Another factor that can influence the environmental distribution of a chemical is the presence of charged groups. Some pollutants, such as the sodium or potassium salts of phenoxyalkanoic herbicides, dinitrophenols, and tetra- or penta-chlo-rophenol, exist as anions in solution. Others, such as the bipyridyl herbicides diquat and paraquat, are present as cations. In either case, the ions may become bound to organic macromolecules or minerals of soils or sediments that bear the opposite 

Organic Pollutants An Ecotoxicological Perspective, Second Edition 

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