利用HYDRUS-2D软件模拟污染事故后三氮污染物的迁移转化规律

Simulation and prediction of leakage incident on migration and transformation of three nitrogens based on HYDRUS-2D software

以某污水处理池泄露污染水环境为例,利用HYDRUS-2D软件构建土壤水分运动和溶质运移模型,模拟三氮在该场地非饱和带垂向以及向下游地表水体的迁移转化过程,为定量预测识别该污水泄漏场地对下伏含水层和下游河流的影响提供技术参考。结果表明:(1)三氮在非饱和带垂向100cm以内明显富集,但富集规律各异;(2)氨氮和亚硝态氮在整个模拟期内并未迁移至潜水面,对下游河流的影响微乎其微,最终污染下伏含水层和下游河流的是硝态氮;(3)硝态氮在污水泄漏事件发生后的第1 095天以0.024 0mg/cm3(即24mg/L)到达下伏潜水面,超过《地下水质量标准》(GB/T 14848—93)中Ⅲ类限值(20mg/L);(4)硝态氮在污水泄漏事件发生后的第938天以0.468 5mg/cm3(即468.5mg/L)的峰值到达下游河流,超过《地表水环境质量标准》(GB 3838—2002)中规定的Ⅴ类限值(2.0mg/L)。

A sewage treatment tank leakage of water pollution was taken as an example to construct the soil water migration and solute transport model by using HYDRUS-2D software. The migration process of the three nitro- gens in the unsaturated zone and the downstream surface water were simulated, providing the technical reference of quantitative prediction to identify the impact of the wastewater spill site on the underlying groundwater and down- stream rivers. The results show that： （1） three nitrogens were enriching within 100 cm of the unsaturated zone,but the enrichment regulations were different. （2） Ammonia nitrogen and nitrite nitrogen did not migrate to the diving surface during the whole simulation period and their impacts on the downstream river were negligible. The final con- tamination entering the lower aquifer and downstream river was the nitrate. （3） Nitrate nitrogen reached the lower diving surface at a stable peak concentration of 0.024 0 mg/cm3 （24 mg/L） on the 1 095th day after the occurrence of the sewage spill,exceeding the ]]I limit of nitrate nitrogen （20 mg/L） in the ＂Groundwater quality standard＂ （GB/T 14848-93）. （4） Nitrate nitrogen reached the downstream river at a peak concentration of 0.468 5 mg/cm3 （468.5 mg/L） on the 938th day after the occurrence of the sewage spill and simultaneously the total nitrogen content exceeds the total nitrogen V limit （2.0 mg/L） stipulated in the ＂Surface water environmental quality standard＂ （GB 3838- 2002）.