A quantitative water, air, sediment interaction (QWASI) fugacity model for describing the fate of chemicals in rivers

Abstract A model is formulated and illustrated which describes the fate of a chemical in a river. The transport and transformation processes included are advective flow (in solution and in association with suspended particles), reaction in sediment and water, sediment desposition, resuspension and burial, and air-water exchange processes of volatilization, absorption, and wet and dry deposition with particulate matter. The equations are formulated in terms of fugacities with common transport and transformation parameters. An analytical solution is obtained describing the concentration of a chemical in water and sediment as a function of flow distance or flow time. It is shown that an equivalent solution can be obtained by sectioning. An example is also given in which the unsteady state “recovery” of a contaminated river is described. Computer programs are appended.