tailieunhanh - Mercury Hazards to Living Organisms - Chapter 13 (end)

Thủy ngân đã được sử dụng bởi con người ít nhất 2300 năm, gần đây nhất như là một loại thuốc diệt nấm trong nông nghiệp, trong sản xuất của clo và natri hydroxide, như một đại lý kiểm soát chất nhờn trong ngành công nghiệp giấy và bột giấy, sản xuất nhựa và các thiết bị điện, và trong các hoạt động khai thác mỏ và luyện kim. Gánh nặng thủy ngân trong một số khoang môi trường được ước tính đã tăng lên đến 5 lần mức precultural, chủ yếu là kết quả của các hoạt động của. | Chapter 13 Concluding Remarks Mercury has been used by humans for at least 2300 years most recently as a fungicide in agriculture in the manufacture of chlorine and sodium hydroxide as a slime control agent in the pulp and paper industry in the production of plastics and electrical apparatus and in mining and smelting operations. Mercury burdens in some environmental compartments are estimated to have increased up to 5 times precultural levels primarily as a result of human activities. The construction of artificial reservoirs for example which release mercury from flooded soils has contributed to the observed elevation of mercury concentrations in fish tissues from these localities. Elevated levels of mercury in living organisms in mercury-contaminated areas may persist for as long as 100 years after the source of pollution has been discontinued. One major consequence of increased mercury use coupled with careless waste disposal practices has been a sharp increase in the number of epidemics of fatal mercury poisonings in humans wildlife and aquatic organisms. Most authorities agree on six points 1. Mercury and its compounds have no known biological function and the presence of the metal in the cells of living organisms is undesirable and potentially hazardous. 2. Forms of mercury with relatively low toxicity can be transformed into forms of very high toxicity such as methylmercury through biological and other processes. 3. Mercury can be bioconcentrated in organisms and biomagnified through food chains. 4. Mercury is a mutagen teratogen and carcinogen and causes embryocidal cytochemical and histopathological effects. 5. Some species of fish and wildlife contain high concentrations of mercury that are not attributable to human activities. 6. Anthropogenic use of mercury should be curtailed as the difference between tolerable natural background levels of mercury and harmful effects in the environment is exceptionally small. Most authorities also agree on another six