(BQ) Part 2 book "An introduction to environmental chemistry and pollution" has contents: Environmental cycling of pollutants, environmental monitoring strategies, ecological and health effects of chemical pollution, managing environmental quality. | CHAPTER 6 Environmental Cycling of Pollutants ROY M. HARRISON 1 INTRODUCTION: BIOGEOCHEMICAL CYCLING The earlier chapters of this book have followed the traditional subdivision of the environment into compartments (. atmosphere, oceans, etc.). Whilst these sub-divisions accord with human perceptions and have certain scientific logic, they encourage the idea that each compartment is an entirely separate entity and that no exchanges occur between them. This, of course, is far from the truth. Important exchanges of mass and energy occur at the boundaries of the compartments and many processes of great scientific interest and environmental importance occur at these interfaces. A physical example is that of transfer of heat between the ocean surfaces and the atmosphere, which has a major impact upon climate and a great influence upon the general circulation of the atmosphere. A chemically based example is the oceanic release of dimethyl sulfide to the atmosphere, which may, through its decomposition products, act as a climate regulator (see Chapter 4). Pollutants emitted into one environmental compartment will, unless carefully controlled, enter others. Figure 1 illustrates the processes affecting a pollutant discharged into the As mixing processes dilute it, it may undergo chemical and physical transformations before depositing in rain or snow (wet deposition) or as dry gas or particles (dry deposition). The deposition processes cause pollution of land, freshwater, or the seas, according to where they occur. Similarly, pollutants discharged into a river will, unless degraded, enter the seas. Solid wastes are often disposed into a landfill. Nowadays these are carefully designed to avoid leaching by rain and dissemination of pollutants into groundwaters, which might subsequently be used for potable supply. In the past, however, instances have come to light where 1 W. H. Schroeder and D. A. Lane, Environ. Sci. TechnoL, 1988, 22, .
