Collaborative Research: Biogeochemical Influences on Geophysical Sigantures at Light Non-Aqueous Phase Liquids (LNAPL) Impacted Sites

Atekwana在土壤介质的物理、化学和生物特性之后，在土壤环境中引入污染物，如轻非水相液体(LNAPL)。最初，土壤性质的改变主要是物理上的，因为LNAPL占据了居住土壤的孔隙。随着时间的推移，LNAPL经历了由微生物介导的改变土壤性质的过程所驱动的变化。地球物理方法能够检测到土壤中新释放的LNAPL，因为它们的较高电阻率很容易与背景孔隙和地下水区分开来。然而，许多对老化的LNAPL泄漏的电阻率测量表明，这是一个下降，而不是预期的增加。因此，这项研究中要解决的关键假设是，在受影响的介质中，LNAPL的生物地球化学修饰伴随着地电信号的变化，从“新鲜泄漏”中的阻性变化到“老化”或生物降解泄漏中的导电。这项工作的推动是因为需要基本了解受LNAPL影响的土壤中相互关联的生物、化学、地质和水文过程的动力学，以及这些相互关系如何转化为地电响应的可测量变化。其目的是通过实验记录LNAPL微生物降解产生的重要土壤物理和化学参数，以及它们在控制土壤地电性质方面的作用。我们的实验使用了填充来自LNAPL影响现场的沙子的无菌实验室柱。一些柱子被LNAPL覆盖，并接种了来自现场的微生物。维护正控制列和负控制列。地电测量是使用植入柱子中的电极来获得的。这些实验旨在：通过监测微生物类型、种群和群落结构的变化以及潜在电子供体的存在的变化来验证微生物的LNAPL降解；以及记录土壤物理(颗粒)性质和孔隙流体地球化学的变化。综合地球物理、地球化学和微生物学将：(I)记录LNAPL的微生物降解和随后的影响介质的生物地球化学修改如何影响土壤地电响应；(Ii)支持建立量化这些生物地球化学过程所需的地电模型；以及(Iii)为将实验室地球物理降解模型扩展到受有机化学品污染的现场提供基础。

0087795Atekwana Introduction of pollutants in the soil environment such as Light Non-Aqueous Phase Liquids (LNAPLs) after the physical, chemical, and biological properties of the soil media. Initially, the alteration of the soil properties is primarily physical as the LNAPL occupies pores of the resident soils. With time, the LNAPL undergoes changes driven by microbial-mediated processes that alter soil properties. Geophysical methods are able to detect freshly released LNAPLs in soils because their higher electrical resistivity readily distinguishes from background pore and groundwater. Nevertheless, many resistivity measurements of aged LNAPL spills reveal a decrease and not the expected increase. Hence, the key hypothesis to be addressed in this study is that shifts in geoelectrical signatures from resistive in "fresh spills" to conductive in "aged" or biodegrading spills accompany biogeochemical modifications of LNAPL in the impacted media. The work is driven by the need to gain a basic understanding of the dynamics that interrelate biological, chemical, geological, and hydrological processes in LNAPL-impacted soils and how these interrelations translate into measurable changes in the geoelectrical response. The objective is to experimentally document important soil physical and chemical parameters that result from microbial degradation of LNAPL and their role in controlling the soil's geoelectrical properties.Our experiments use sterilized laboratory columns filled with sands from a field site impacted with LNAPL. Some of the columns are layered with LNAPL and inoculated with microbes from the field site. Positive and negative control columns are maintained. Geoelectrical measuremens are obtained using electrodes implanted in the columns. The experiments are designed to:Verify microbial LNAPL degradation by monitoring changes in microbial types, population and community structure, and changes in the presence of potential electron donors; andDocument changes in soil physical (grain) properties and in pore fluid geochemistry.Integrating geophysics, geochemistry, and microbiology will: (i) document how microbial degradation of LNAPLs and subsequent biogeochemical modifications of the impact media influence soil geoelectrical responses; (ii) support development of geoelectrical models necessary to quantify these biogeochemical processes; and (iii) provide a basis for extending laboratory geophysical degradation models to field sites contaminated with organic chemicals.