Sand, clay and rock have to be excavated for a variety of purposes, such as dredging, trenching, mining (including deep sea mining), drilling, tunnel boring and many other applications. Many excavations take place on dry land, but they are also frequently required in completely saturated conditions, and the methods necessary to accomplish them consequently vary widely. This book provides an oveā¦
We start by defining air pollution and examining the main sources of air pollution. We then classify air pollutants according to origin, chemical composition, state of matter, and area of impact; and examine the effects of air pollution, particularly the immediate health affects. We conclude by explaining Hong Kong's Air Pollution Index.