АвтомобилиАстрономияБиологияГеографияДом и садДругие языкиДругоеИнформатикаИсторияКультураЛитератураЛогикаМатематикаМедицинаМеталлургияМеханикаОбразованиеОхрана трудаПедагогикаПолитикаПравоПсихологияРелигияРиторикаСоциологияСпортСтроительствоТехнологияТуризмФизикаФилософияФинансыХимияЧерчениеЭкологияЭкономикаЭлектроника


Читайте также:
  2. Pollution
  3. Pollution


Ever since man progressed from hunting to an agricultural society with the corresponding development of stable communities the phenomenon of water pollution has been his constant companion. The better agricultural method improved, the smaller percentage of the population produced all the food needed; so the larger communities and diverse secondary industries developed and grew into the present modern society.

Concurrent with this growth, however, there was the increasing percentage of waste materials and the problem of their disposal. While the total volume of waste from community was relatively small, the easiest method of disposal was to “throw it away”, usually into the nearest receptacle. Since man cannot exist without water, community development and city growth was centered in areas where the water supplies were adequate and continuous. Initially this meant development in river valleys, and thus the nearest receptacle for wastes was a river.

The term “pollution’ has been variously defined by many people, but if it may he described here as “the detrimental effects on a localized ecological structure by the addition of the waste products of a society”, then it is apparent that the first noticeable pollution problems should have involved the supply of drinking water.

It is in this particular area that the question of pollution takes on a new meaning. Is a body of water polluted when it is directly affected by man, or should it be classified as polluted when the ecological structure is first upset?

The hydrosphere is a dynamic system containing physiochemical and biological equilibria, and there is no doubt that a normally active waterway has a large capacity to assimilate wastes. However, in many areas this capacity is now so being reached or exceeded that many waterways are becoming increasingly contaminated. Before this contamination becomes readily noticeable such equilibria are changed and the ecological structure may be seriously affected.

Some examples of water systems, where the effects of pollution have become or are becoming increasingly apparent are the Caspian and Baltic seas; the Thames, Rhine, and Seine rivers; and the Baikal Lake in Russia. Fortunately, the dynamic hydrosystems have a remarkable capacity for regeneration and with careful planning even the most seriously polluted waterways may be brought back into full use. An example of river regeneration on a large scale is the successful attempt to restore the Thames estuary.


7. Complete the following sentences with the corresponding phrases:


1. The hydrosphere is a dynamic system containing... 2. Concurrent with the growth of urban population there was the increasing percentage of... 3. Since man cannot exist without water... 4. The nearest receptacle for wastes was … 5. A normally active waterway has… 6. The dynamic hydrosystems like rivers have a remarkable capacity for...


Дата добавления: 2015-09-13; просмотров: 23; Нарушение авторских прав

lektsii.com - Лекции.Ком - 2014-2022 год. (0.013 сек.) Все материалы представленные на сайте исключительно с целью ознакомления читателями и не преследуют коммерческих целей или нарушение авторских прав
Главная страница Случайная страница Контакты