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Multimedia Environmental Models - Chapter 6

McKay, Donald. "Advection and Reactions" Multimedia Environmental Models Edited by Donald McKay Boca Raton: CRC Press LLC,2001 CHAPTER 6 Advection and Reactions 6.1 INTRODUCTION In Level I calculations, it is assumed that the chemical is conserved; i.e., it is neither destroyed by reactions nor conveyed out of the evaluative environment by flows in phases such as air and water. These assumptions can be quite misleading when determining of the impact of a given discharge or emission of chemical. First, if a chemical, such as glucose, is reactive and survives for only 10 hours as a result of its susceptibility to rapid biodegradation, it must pose. | McKay Donald. Advection and Reactions Multimedia Environmental Models Edited by Donald McKay Boca Raton CRC Press LLC 2001 CHAPTER 6 Advection and Reactions 6.1 INTRODUCTION In Level I calculations it is assumed that the chemical is conserved i.e. it is neither destroyed by reactions nor conveyed out of the evaluative environment by flows in phases such as air and water. These assumptions can be quite misleading when determining of the impact of a given discharge or emission of chemical. First if a chemical such as glucose is reactive and survives for only 10 hours as a result of its susceptibility to rapid biodegradation it must pose less of a threat than PCBs which may survive for over 10 years. But the Level I calculation treats them identically. Second some chemical may leave the area of discharge rapidly as a result of evaporation into air to be removed by advection in winds. The contamination problem is solved locally but only by shifting it to another location. It is important to know if this will occur. Indeed recently considerable attention is being paid to substances that are susceptible to long-range transport. Third it is possible that in a given region local contamination is largely a result of inflow of chemical from upwind or upstream regions. Local efforts to reduce contamination by controlling local sources may therefore be frustrated because most of the chemical is inadvertently imported. This problem is at the heart of the Canada-U.S. and Scan-dinavia-Germany-U.K. squabbles over acid precipitation. It is also a concern in relatively pristine areas such as the Arctic and Antarctic where residents have little or no control over the contamination of their environments. In this chapter we address these issues and devise methods of calculating the effect of advective inflow and outflow and degrading reactions on local chemical fate and subsequent exposures. It must be emphasized that once a chemical is degraded this does not necessarily solve the .