The atmosphere The atmosphere is a thin blanket of gas that envelops the earth The gases that make up the atmosphere are held close to the earth by the pull of gravity With increasing distance from the earth's surface, the temperature, density, and composition of the atmosphere gradually change

Air quality and particles Epidemiological(流行病学) evidence associates atmospheric particles with diseases and mortality Particles penetrate the lungs, blocking and irritating aIr passages. Particles themselves could exert toxic effects. ( toxic substances present in the particles [polycyclic Aromatic Hydrocarbons are examples of toxic substances in aerosols.]

Objectives of Water Treatment The objectives for water treatment derive from two concerns Human health and welfare The health of aquatic ecosystems

Pests and pesticides Pest: ANY UNWANTED organism that directly or indirectly interfere human activity is called a pest. Pesticides, or biocides are substances that can kill organisms that we consider to be undesirable The most widely used types of pesticides Insecticides Herbicides

Library of Congress Cataloging-in-Publication Data Manahan, Stanley E Environmental chemistry Stanley E. Manahan.-7th ed p. cm. Includes bibliographical references and index

2.1水体污染 2.2水体中污染物的类别、来源和危害 2.3水处理方法

Acute(急性) and chronic(慢性) toxicity Acute toxicity refers to a rapid and serious response to a high but short-lived dose Acute poisons interfere with essential physiological processes, leading to a variety symptoms of distress, even death Chronic toxicity refers to a time-lagged response to a relatively low but prolonged exposure

Plant nutrients Plant growth requires various nutrients Major nutrient elements: C,N, P trace elements: S, Si, Cl, I, and metallic elements(Fe, Mn, Cu, etc) The minor elements because of the low demand can Water y be supplied at adequate rates in natural

2.1土壤胶体及其吸附性 2.2土壤的酸碱性 2.3土壤的氧化还原性

Toxic metals Some metals are essential for the normal development and well-being of humans and other creatures They include Na, K, ca, Mg, cu, Cr, and Zn Other metals are toxic even when present in an organism at very low concentrations Examples: Antimony, Arsenic, Barium