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Multimedia Environmental Models - Chapter 2

Một số khái niệm cơ bản 2,1 GIỚI THIỆU Phần lớn của niềm đam mê khoa học với môi trường nằm trong phức tạp đáng kinh ngạc của nó. Nó bao gồm một số lượng lớn các giai đoạn như không khí, đất và nước, thay đổi tính chất và thành phần từ nơi này đến nơi (không gian) và với thời gian (thời gian). Nó là rất khó khăn để lắp ráp một mô tả chi tiết về điều kiện (nhiệt độ, áp suất, và thành phần) của ngay cả một hệ thống môi trường nhỏ hoặc thu nhỏ bao gồm,. | McKay Donald. Some Basic Concepts Multimedia Environmental Models Edited by Donald McKay Boca Raton CRC Press LLC 2001 CHAPTER 2 Some Basic Concepts 2.1 INTRODUCTION Much of the scientific fascination with the environment lies in its incredible complexity. It consists of a large number of phases such as air soil and water which vary in properties and composition from place to place spatially and with time temporally . It is very difficult to assemble a complete detailed description of the condition temperature pressure and composition of even a small environmental system or microcosm consisting for example of a pond with sediment below and air above. It is thus necessary to make numerous simplifying assumptions or statements about the condition of the environment. For example we may assume that a phase is homogeneous or it may be in equilibrium with another phase or it may be unchanging with time. The art of successful environmental modeling lies in the selection of the best or least-worst set of assumptions that yields a model that is not so complex as to be excessively difficult to understand yet is sufficiently detailed to be useful and faithful to reality. The excessively simple model may be misleading. The excessively detailed model is unlikely to be useful trusted or even understandable. The aim is to suppress the less necessary detail in favor of the important processes that control chemical fate. In this chapter several concepts are introduced that are used when we seek to compile quantitative descriptions of chemical behavior in the environment. But first it is essential to define the system of units and dimensions that forms the foundation of all calculations. 2.2 UNITS The introduction of the SI or Système International d Unites or International System of Units in 1960 has greatly simplified scientific calculations and communication. With few exceptions we adopt the SI system. The system is particularly convenient because it is coherent in that the basic