山地城市合流污水特细砂来源

对三峡库区山地城市合流制污水特细砂、管道沉积物、本地土壤等进行矿物成分分析表明，污水中特细砂矿物成分以石英、方解石，长石类为主，并含有少量云母、赤铁矿和石膏等矿物；认为特细砂主要来自周边砂壤质地土壤、风化岩石和地表沉积物；山地城市合流制管网（污水常规收集方式），山涧、边沟和冲沟（污水特殊收集方式）是细砂迁移的途径；生活污水和雨水是细砂迁移的载体；中亚热带湿润季风气候，加速成土母质主要是侏罗系紫色砂质岩、泥岩和石灰岩风化，而山地、丘陵地貌特征和充沛的雨量强化合流雨污水冲刷作用，导致水土流失加剧。因此，对于山地城市合流污水特细砂的治理，需要从合流制管网建设完善、水土流失防治、生活小区统一规划和污水处理厂除砂系统优化等多个方面进行控制。

Sources of ultra-fine grit in combined sewer of moutainous urban

In mountainous urban of Three Gorges Reservoir Area, mineral composition analysis of ultra-fine grit in combined sewer system, pipeline sediments and local soil showed that the ultra-fine grit was mainly com- posed of quartz, calcite and feldspars, also containing a small amount of mica, hematite, gypsum and other min- erals. The ultra-fine grit mainly came from surrounding sandy soil, weathered rock and surface sediments. The combined sewer system, streams, ditches and gullies were fine grits＇ migration approach. Sewage and rainwater was the carrier of fine grit migration. In humid subtropical monsoon climate, it had speeded up the Jurassic pur- ple arenaceous rock, shale and limestone weathering. The mountains, hilly geomorphic features and abundant rainfall led to soil erosion aggravated and sewage scouring effect enhanced. So, much work should be done for ul- tra-fine grit in combined sewer system of mountainous urban, such as improving sewer pipe net, preventing soil erosion, unified planning of the living quarters and optimization of grit removal system in wastewater treatment plants, et al.