Rural sewage was one of the reasons that caused rural water environmental pollution, and was an important factor in lake eutrophication.
农村的生活污水，是造成农村水环境污染的原因之一，也是造成湖泊富营养化的重要因素。
2
Rather more factors such as economic, environment and hydrology should be taken into account to confirm sewage closure multiplication factor and can hardly be quantitative analyzed.
确定截流倍数要考虑的因素比较多，如经济、环境、水文等，很难进行准确定量分析。
3
The sewage irrigation still is the major influencing factor on soil trace element variation during the agriculture production.