内蒙古河套灌区浅层地下水化学特征和灌溉适宜性分析

Hydrochemical Characterization and Irrigation Suitability Analysis of Shallow Groundwater in Hetao Irrigation District, Inner Mongolia

随着黄河流域水资源供需矛盾加剧,我国特大型灌区——内蒙古河套灌区开始采用黄河水与地下水相结合的方式进行农业灌溉。本研究采集河套灌区内499组地下水样品和1组黄河水样品,在分析地下水和黄河水样品的水化学特征基础上,运用钠吸附比(SAR)、渗透指数(PI)、钠含量(SC)和残余碳酸钠(RSC)以及《农田灌溉水质标准(GB 5084—2021)》对地下水和黄河水的灌溉适宜性进行对比分析。结果表明,地下水与黄河水均为弱碱性水,Ca^(2+)和HCO_(3)^(-)为优势离子,Gibbs图显示地下水受到岩石风化淋溶和蒸发浓缩的双重影响,对灌溉适宜性影响较大的钠盐主要来自岩盐溶解。灌溉适宜性分析结果表明,从SAR、PI和RSC指标来看,地下水的灌溉适宜性较好,从SC指标来看,不适宜灌溉的地下水主要分布在灌区北部总排干和灌区南部黄河沿岸;根据农田灌溉水质标准分析,除总砷和氯化物两项指标外,其余指标适宜灌溉样品占比均高于90%,综合评价全区共231组地下水样品适宜灌溉。地下水与黄河水灌溉适宜性对比表明,黄河水的SAR和SC指标灌溉适宜性分析结果较好,地下水的PI和RSC指标灌溉适宜性分析结果较好,根据灌溉水质标准显示黄河水所有指标均适宜灌溉。本研究为日后内蒙古河套灌区合理选用灌溉水源提供数据支撑,为该区域地下水的治理与防控提供科学依据。

With the aggravation of conflict between supply and demand of water resources in the Yellow River basin, both Yellow River water and groundwater are used for agricultural irrigation in the Hetao region of Inner Mongolia(one of the large irrigation districts in China). In this paper, 499 groundwater samples and 1 Yellow River water sample were collected. Based on hydrogeochemical analysis of these samples, the irrigation suitabi-lity difference between groundwater and Yellow River water has been studied by SAR, PI, SC, RSC and Irrigation Water Quality Standard(GB 5084-2021). The results show that the environment of groundwater and Yellow River water are both weakly alkaline, and the major ions are Ca^(2+)and HCO_(3)^(-). The Gibbs diagram shows that the groundwater is affected by rock weathering/leaching and evaporation concentration, and the sodium salts(which have immense influence on irrigation suitability) come mainly from rock salt dissolution. According to the irrigation suitability analysis results about SAR, PI and RSC, the groundwater is suitable for irrigation. According to the SC evaluation result, the groundwater unsuitable for irrigation is mainly distributed in the main drainage channel in the northern irrigation area and along the Yellow River in the southern irrigation area. According to the irrigation water quality standard, except for the total arsenic and chloride, over 90% samples have other irrigation suitability indices. A total of 231 samples are suitable for irrigation. Comparing the irrigation suitability between groundwater and Yellow River water, we suggest that SAR and SC indices of the Yellow River water are better, while the PI and RSC indices of groundwater are better. The assessment result, using the irrigation water quality standard, shows that the Yellow River water is suitable for irrigation. This study gives data support for the irrigation water source selection, and provides a scientific basis for the future treatment and prevention of groundwater in the Hetao irrigation district in Inner Mongolia.