tailieunhanh - Soil and Environmental Analysis: Physical Methods - Chapter 7

Chương này không phải là một hướng dẫn sử dụng phòng thí nghiệm. Nó là quan tâm nhiều hơn với các nguyên tắc cơ bản các khái niệm về kích thước, hạt, và phân phối, các mối quan hệ giữa chúng, và các phương pháp mà họ có thể được đo. Hiện nay có khoảng 400 kỹ thuật báo cáo để xác định kích thước hạt (Barth và Sun, 1985; Syvitski, 1991), mặc dù cơ thể lớn của các phép đo tích lũy được các nhà khoa học đất nói chung đã được thực hiện bằng cách sử dụng các. | 7 Particle Size Analysis Peter J. Loveland Cranfield University Silsoe Bedfordshire England W. Richard Whalley Silsoe Research Institute Silsoe Bedfordshire England I. INTRODUCTION This chapter is not a laboratory manual. It is more concerned with the principles underlying the concepts of particle size and distribution the relationships between them and the methods by which they may be measured. There are now some 400 reported techniques for the determination of particle size Barth and Sun 1985 Syvitski 1991 although the large body of measurements amassed by soil scientists has generally been made using simple methods and equipment principally sieving gravitational settling the pipet and the hydrometer. There is also a large body of experience in interpreting these data. However there is still a surprising lack of uniformity in these simple procedures and for that reason we consider them in some detail. The classification of soils in terms of particle size stems essentially from the work of Atterberg 1916 . He built on the work of Ritter von Rittinger 1867 in relation to rationalization of sieve apertures as a function of spherical particle volume and that of Oden 1915 who applied Stokes law to soil science for the first time. In 1927 the International Society of Soil Science adopted proposals to standardize the method for the mechanical analysis of soils by a combination of sieving and pipeting and equally important resolved to analyze at least for agricultural soils only the fraction passing a round-hole 2 mm sieve the so-called fine earth ISSS 1928 . There have been many revisions of the particle size classes promulgated in 1927 and it is now recognized that soil science can make little further headway in Copyright 2000 Marcel Dekker Inc. the interpretation of particle size distribution in the submicrometer range because the simple methods are incapable of further resolution. For that reason we have reviewed a number of less common or more recent instrumental .