DOI: 10.15986/j.1006-7930.2019.01.018
强化雨水入渗是目前海绵城市建设的重要内容之一.本文通过现场实测和计算模拟探讨了西安城区雨水下渗特征,构建以湿陷性黄土层为约束条件的城市绿地渗水地层模型,采用HYDRUS软件模拟分析了西安城区下凹式绿地深度(入渗作用水头)与雨水下渗深度的关系,并分析了雨水在土壤下渗过程中污染物浓度在土壤中的迁移消减变化规律.结果显示,以地下5.0 m处存在湿陷性黄土为约束,25.0 cm入渗水头作用下对应的连续渗水时间为16.6 d,小于西安城区历史连续降雨极限天数(19 d),因此在西安城区进行雨水下渗措施建设必须考虑地质条件的约束; 以降雨径流在5.0 cm水头下渗为初始条件,雨水中典型污染物的变化表明,氨氮在土壤以及植物根系作用下基本去除,而CODCr、总磷和总氮在40～50 cm深度土壤中污染物仍然有很高残存.研究结果为湿陷性黄土地区城市雨水下渗系统和径流面源污染治理了提供依据.
Currently, strengthening rainwater infiltration is one of the important contents of sponge city construction. This paper investigated the infiltration characteristics of Xi'an through field measurement and computer simulation, established the corresponding relationship between green subsurface pit depth and rainwater infiltration depth, constructed a water-infiltrating stratum model of urban green space with the collapsible loess layer as the constraint condition, and analyzed the water head of infiltration in depressed greenland with infiltration depth by using HYDRUS software. The results revealed that the collapsible loess at the depth of 5.0 m underground was the constraint while the time corresponding to the continuous action of the 25.0 cm infiltration head was 16.6 days, which is shorter than the climate history of continues rainfall time(19 days)in Xi'an. Therefore, the construction of rainwater infiltratiosn in Xi'an must take into account the geological conditions of constraint. With the initial condition of the rainfall runoff head infiltration at 5.0 cm, changes in typical pollutants in rainwater showed that ammonia nitrogen in rainwater can be removed easily by soil adsorption and bio-degradation of plant root system. However, CODcr, TP and TN concentration remained high at the depth of 40～50 cm soil. The results provide evidence for construction of urban rainwater infiltration system and runoff non-point source pollution control in the collapsible loess area.
