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代写留学生作业The water resource on the earth is limited. Though 70% of the earth’s surface is covered by water, only 0.77% of it can be used. In addition, because of the serious pollution and lack of sewage treatment systems, the developing countries suffer the stressed and critical water problems. In these countries, 90% of the spent water was poured directly and about 3 billion people in the world have no chance to obtain the clean water(GLOBAL ISSUES P170,) .Krantz and Kifferstein (1998) pointed out that agricultural, industrial and urban wastewaters are the major causes of water pollution in developing countries. They also classified these three causes to two types: point and non-point pollution. Point pollution sources emitters the waste into water directly, but non-point sources do not. According to the difference between these two sources, the agricultural pollution can be ranked as the non-point pollution and the rest are point pollution sources.This essay will explain these main factors of water pollution in less developed world.

Agricultural pollution is well- documented in less developed countries. In these under-developing countries, where agriculture is still dominant, the agricultural pollution is more seriously than the G7 or other developed countries. (G. D. Agrawal, 1999)As the development of science, chemical fertilizers are widely used in the farmland to make the crops and vegetables grow quickly. However, the runoff of fertilizers becomes one of the main sources of pollution. (GLOBAL ISSUES, P97) The concentration of the nutrient phosphorus and nitrogen is often very low in nature. It is the limiting factor for the aquatic plants. (Richard T Wright,2008)When the fertilizer (rich in N, P) runs into the water body, it can over-stimulate the growth of algae and other plants under the water. After these organisms die, they will consume the O2. It leads to the death of fish and other animals in the water. This kind of water space is called “dead zone”.Overspend of pesticides such as DDT also results in fearful problems. Kris Min (2008) comments that most of the pesticides people used contain rank poison. These harmful substances will influence humans’ health and even make them die.There are two examples for the agricultural pollution. The first event happened in Wuxi, China. Because of the excessive use of fertilizers, the blue-green algae grew too quickly and make the water too bad to drink and wash. The people in WUXI city had no access to the clear water in five days. The other one is Bangladesh. People there discharge their sewage which contains fertilizer directly into rivers and affect population in the downstream. (Hettige, Huq, Sheolipargal, Wheeler, 1996)

Industrial pollution is the other main factor. The industrialization in the developing countries contributes to acute water pollution. (GI p156)In Tianjin，a city of China， there are 5,000 separate industrial units. Most of these factories are chemical, metallurgical, textiles and electronics. They discharge the waste water into the water system without treated. It has the very Negative influence on the biosphere and humans’ health.( Kris Min,2008)In fact, because of the low level of technology, the industry in the most developing countries is very inefficiency. In addition, the sewage treatment system there are lagging and the waste is discharged into the surf本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。