基于现场检测的邢台百泉泉域岩溶水硝酸盐氮形成特征

为了揭示邢台百泉泉域岩溶地下水中硝酸盐影响因素及成因，采用便携式分光光度计建立了水中硝酸盐氮现场快速定量检测方法，通过水文地质结构和水化学分析，研究了百泉泉域岩溶地下水中硝酸盐氮的分布特征及其与常规水化学指标之间的关系。实验结果表明：硝酸盐氮在0.60～30.00 mg/L浓度范围内线性关系良好，方法检出限为0.2 mg/L，现场检测与实验室标准方法检测结果之间的相对标准偏差为0.23%～6.70%，差异性检验结果为t=0.984，表明两种检测方法测定结果一致。硝酸盐氮分布特征表明：防污性能较差的百泉泉域西北部岩溶裸露区和东部被第四系上更新统砂砾石含水层直接覆盖的部分岩溶水排泄区硝酸盐氮浓度较高；径流区硝酸盐氮浓度整体较低；采样点岩溶地下水中硝酸盐氮浓度均在地下水质量标准规定的I～III类水之间。研究区岩溶地下水水化学类型较为复杂，阳离子以Ca、Ca?Mg型为主，阴离子以HCO3、HCO3?SO4型为主，HCO3?Cl-Ca?Mg型和Cl?HCO3?SO4-Ca型地下水中硝酸盐氮含量较高，硝酸盐主要来源于城镇污水，受大气降水和农业活动影响较小。研究结果为建立地下水中硝酸盐氮现场检测标准方法及百泉泉域岩溶水资源的供水安全和生态保护提供了参考依据。

Formation Characteristics of Nitrate Nitrogen in Karst Groundwater of Baiquan Spring Catchment in Xingtai by Field Detection

In order to reveal the influencing factors and causes of nitrate in Karst Groundwater in Baiquan spring area of Xingtai, a portable spectrophotometer was used to establish a rapid on-site quantitative detection method for nitrate-nitrogen in water. Based on hydrogeological structure and hydrochemical analysis, the distribution characteristics of nitrate-nitrogen in Karst Groundwater in Baiquan spring area and its relationship with conventional hydrochemical indexes were studied. The experimental results show that the linear relationship of nitrate-nitrogen is good in the range of 0.60-30.00 mg/L, and the detection limit is 0.2 mg/L. The relative standard deviation between the results of field test and laboratory standard method is 0.23%-6.70%, and the difference test result is t=0.984, which indicates that the results of the two methods are identical. The concentration of nitrate-nitrogen in the runoff area is generally low, only in the karst exposed area in the northwest of Baiquan spring area and the karst water discharge area overlying Quaternary upper Pleistocene sand gravel aquifer in the east with poor pollution prevention, the concentration is high. Nitrate-nitrogen concentration in the study area is between Class I and Class III water specified in the quality standard of groundwater. The hydrochemical types of karst groundwater in the study area are complex, with Ca and Ca?Mg type is the main cation, HCO3 and HCO3?SO4 type is dominant anion. Nitrate-nitrogen content in groundwater of HCO3?Cl-Ca?Mg and Cl?HCO3?SO4-Ca type is relatively higher. The main source of nitrate is urban sewage, which is less affected by atmospheric precipitation and agricultural activities. The research results provide reference basis for establishing standard method of nitrate-nitrogen in groundwater on-site detection and water supply safety and ecological protection of karst water resources in Baiquan spring area.