ABSTRACT
This chapter covers the basics involved with the circulation of matter through the ecosystem—the biogeochemical cycles. Within the biogeochemical cycles, all of the essential elements circulate from the environment to organisms and back to the environment. The chapter deals with units and measurement commonly used in the science of environmental pollution. Pollution scientists and technicians are primarily concerned with the interaction of energy and materials in the ecosystem. Probably the simplest way to express materials balance, one of the most important and fundamental scientific principles, is to point out that everything has to go somewhere; moreover, material inputs to every process must balance with the outputs. A basic knowledge of units of measurement and how to use them is essential for students of pollution science. Pollution science students and practitioners should be familiar with both the US Customary System (USCS), or English system, and the International System of Units (SI).
