tailieunhanh - Environmental Pollution Control Microbiology - Chapter 7

Đất là một phương tiện thú vị cho các vi sinh vật phát triển. Nó chứa khác nhau chất dinh dưỡng mà vi khuẩn cần thiết cho quá trình trao đổi chất của họ. Thật không may, các chất dinh dưỡng không phải luôn luôn có sẵn. Đất không phải là một vật liệu đồng nhất, mà là một không đồng nhất vật liệu. Đất bao gồm các hạt đất đá, các hạt đất sét, và hạt phù sa trong các kết hợp khác nhau và với số lượng nước khác nhau. chất rắn hạt hình thành các lớp hoặc các khối với các khoảng. | Chapter 7 SOIL MICROBES Soil is an interesting medium for growing microorganisms. It contains various nutrients that the microbes need for their metabolism. Unfortunately the nutrients are not always readily available. Soil is not a homogeneous material but rather is a heterogeneous material. Soil consists of ground rock particles clay particles and silt particles in various combinations and with varying amounts of water. The solid particles form layers or clumps with open void spaces between the different soil particles. Microorganisms cannot penetrate the solid soil particles. They can live on the surface of the particles provided there are adequate nutrients and water for their growth. Organic matter discharged from living organisms on the soil surface provides the major nutrients for the microorganisms in the soil. The upper layer of soil provides the best environment for growing microorganisms. Bacteria fungi actinomycetes algae protozoa and nematodes can be found in organic rich soil. The soil environment determines the specific microbes that can grow and their numbers. The seasons of the year produce the most important environmental variables with both temperature and moisture changes. SOIL CHARACTERISTICS Engineering courses dealing with soils are concerned more with the physical characteristics of soils than with their chemical characteristics. Both the physical and the chemical characteristics of soil are important in developing a proper understanding of soil microbiology. Natural forces such as wind rain freezing thawing and pressure help form soil. Rocks are slowly broken into small particles 50 p to 1 mm known as sand. As the particles decrease in size to between 2 p and Copyright 2004 by Marcel Dekker Inc. All Rights Reserved. 50 p they are called silt. Particles less than 2 p in size are known as clay. All of these particles are essentially quartz SiO2 with various chemical contaminants. The primary chemical contaminants include iron aluminum calcium