Schulmeister Marcia K, Healey John M, Butler James J, McCall G Wesley
Kansas Geological Survey, 1930 Constant Avenue, Campus West, University of Kansas, Lawrence, KS 66047, USA.
J Contam Hydrol. 2004 Apr;69(3-4):215-32. doi: 10.1016/j.jconhyd.2003.08.002.
Discrete-depth sampling of inorganic groundwater chemistry is essential for a variety of site characterization activities. Although the mobility and rapid sampling capabilities of direct-push techniques have led to their widespread use for evaluating the distribution of organic contaminants, complementary methods for the characterization of spatial variations in geochemical conditions have not been developed. In this study, a direct-push-based approach for high-resolution inorganic chemical profiling was developed at a site where sharp chemical contrasts and iron-reducing conditions had previously been observed. Existing multilevel samplers (MLSs) that span a fining-upward alluvial sequence were used for comparison with the direct-push profiling. Chemical profiles obtained with a conventional direct-push exposed-screen sampler differed from those obtained with an adjacent MLS because of sampler reactivity and mixing with water from previous sampling levels. The sampler was modified by replacing steel sampling components with stainless-steel and heat-treated parts, and adding an adapter that prevents mixing. Profiles obtained with the modified approach were in excellent agreement with those obtained from an adjacent MLS for all constituents and parameters monitored (Cl, NO(3), Fe, Mn, DO, ORP, specific conductance and pH). Interpretations of site redox conditions based on field-measured parameters were supported by laboratory analysis of dissolved Fe. The discrete-depth capability of this approach allows inorganic chemical variations to be described at a level of detail that has rarely been possible. When combined with the mobility afforded by direct-push rigs and on-site methods of chemical analysis, the new approach is well suited for a variety of interactive site-characterization endeavors.
对无机地下水化学进行离散深度采样对于各种场地特征描述活动至关重要。尽管直接推压技术的移动性和快速采样能力使其在评估有机污染物分布方面得到广泛应用，但尚未开发出用于描述地球化学条件空间变化的补充方法。在本研究中，在一个先前观察到明显化学对比和铁还原条件的场地，开发了一种基于直接推压的高分辨率无机化学剖面分析方法。使用跨越向上变细冲积层序的现有多级采样器（MLS）与直接推压剖面分析进行比较。由于采样器的反应性以及与先前采样层的水混合，使用传统直接推压暴露筛网采样器获得的化学剖面与相邻MLS获得的剖面不同。通过用不锈钢和热处理部件替换钢制采样部件，并添加防止混合的适配器对采样器进行了改进。对于所监测的所有成分和参数（Cl、NO(3)、Fe、Mn、DO、ORP、电导率和pH），使用改进方法获得的剖面与从相邻MLS获得的剖面非常吻合。基于现场测量参数对场地氧化还原条件的解释得到了溶解铁实验室分析的支持。这种方法的离散深度能力使得能够以很少达到的详细程度描述无机化学变化。当与直接推压钻机的移动性和现场化学分析方法相结合时，这种新方法非常适合各种交互式场地特征描述工作。
