《第四章土壤环境》-精选·课件.ppt

主讲：沈卫国 第一节 土壤的组成与结构 Soil Horizon Texture Structure Soil Horizon 4 courses (Horizons) A 腐殖质层（淋溶层）—Organic layer and top soil B 沉淀层—Subsoil C 母质层—Parent material 风化层、母岩——mantlerock A Horizon Common names - Organic layer and top soil Traits Contains most plant roots Heavily leached from heavy rainfall Contains high organic matter Dark in color B Horizon Common name - Subsoil Traits Zone of acclimation ( Nutrients, silts and clays accumulate in this zone) Little to No organic matter Red and yellow in color C Horizon Common name - Parent material Traits Below the root zone Outside the Biological zone (Point were no plant or animals can grow or live) Texture Definition: Percentage of sand, silt and clay particles Size of particles.(largest to smallest) Sand Silt Clay Texture Why is texture Important? Water absorption rates Soil water storage capacity Ease of tillage Amount of aeration Soil Fertility Texture Determining Soil Texture By Feel Sand Coarse gritty feel Silt Medium-silty, floury feel Clay Fine-sticky when wet Structure Definition - the physical arrangement of soil particles Structure affects the movement of water, air and root penetration Structure Types of structures Columns Blocky Granular Plate-like Structure Columns Water penetration-good Drainage-good Aeration-good Structure Blocky Water Penetration(透水性)-good Drainage(排水性)-moderate Aeration（充气性）-moderate Structure Granular Water Penetration-good Drainage-best Aeration-best Structure Plate-like Water Penetration-moderate Drainage-moderate Aeration-moderate 2 . 土壤污染及其特点 2.1 关于土壤污染的概念 迄今还没有统一的提法。 美国肯珀（Kemper W.D.）认为，当加入土壤中的物质数量大到足以妨碍土壤的正常功能时，就认为土壤被污染了。任何降低作物或土壤水分的数量或质量的物质被称为污染物。按照它的含意，土壤次生盐渍化、沙化、酸化、侵蚀等都应属于土壤污染范围。 日本馆稔等人认为，土壤污染是由于化学物质的侵入而损害了土壤的健全机能。虽然他提出的概念较简练，但所指的“化学物质”含意广泛，既可理解为有毒有害的化学物质，也可理解为所有的化学物质，但不一定都造成污染。 关于土壤污染的概念 具体地说，污染物质系指与人为活动有关的各种对人体和生物有害的物质，包括化学农药、重金属、放射性元素、病原菌等。 土壤污染则是指这些污染物质进入土壤，并在土壤中不断累积，引起土壤的组成、结构和功能的变化，从而影响植物的正常生长和发育，以致在植物体内积累，使作物产量和质量下降，最终影响人体健康。 2.2 土壤中污染物的来源 土壤污染的发生是与土壤的特