Engineered sulfate injection has been introduced as an effective technology to enhance the remediation of soil and groundwater contaminated by petroleum hydrocarbons. While some studies indicate that sulfate injection is a promising method for the treatment of hydrocarbon-contaminated subsurface systems, its application in the brackish soil environments is unknown. In this study, we explored related geochemical indicators along with soil adsorption and dissolved phase concentrations to provide an improved understanding of the hydrocarbon-contaminated subsurface responses to the sulfate injection in brackish environments. A series of flow-through experiments representing in situ groundwater anaerobic bioremediation were conducted and two sulfate injection episodes were applied to examine the degradation of dissolved naphthalene under low salinity and brackish conditions. As opposed to the substantial body of previous studies that salinity restricts biodegradation, the results from this study showed that naphthalene anaerobic degradation was more stable once the salinity was as high as that at the sampling location in the coastal brackish environment. While increasing naphthalene concentration from 4 to 12 mg L⁻¹ did not limit biodegradation efficiency under brackish condition similar to the sampling location, it adversely restricted the developed reducing conditions and biodegradation process under low salinity conditions. This highlights the adaption of the microbial communities within the soil to the brackish environment at the sampling location suggesting that changing the salinity during engineered sulfate application can make the remediation process more susceptible against the environmental stresses and substrate toxicity. The results of this study provide insight into the engineered sulfate application as a remediation strategy for potential removal of dissolved naphthalene from the contaminated brackish groundwater.

中文翻译：

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顺序注入硫酸盐在（半）干旱沿海土壤中萘降解的增强作用：通过反应器实验

工程硫酸盐注入已被引入作为一种有效的技术，以增强对石油烃污染的土壤和地下水的修复。尽管一些研究表明，硫酸盐注入法是一种用于处理碳氢化合物污染的地下系统的有前途的方法，但其在微咸土壤环境中的应用尚不清楚。在这项研究中，我们探索了相关的地球化学指标，以及土壤的吸附和溶解相的浓度，以提供对含盐污染的地下环境在咸淡环境中对硫酸盐注入的响应的更好理解。进行了一系列代表原位地下水厌氧生物修复的流通实验，并进行了两次硫酸盐注入试验，以研究在低盐度和咸淡条件下溶解的萘的降解情况。与以前的大量研究表明盐度限制了生物降解相反，这项研究的结果表明，一旦盐度与沿海咸淡环境中采样点的盐度一样高，萘的厌氧降解将更加稳定。同时将萘浓度从4 mg L增加至12 mg L 这项研究的结果表明，一旦盐度与沿海微咸环境中采样点的盐度一样高，萘的厌氧降解将更加稳定。同时将萘浓度从4 mg L增加至12 mg L 这项研究的结果表明，一旦盐度与沿海微咸环境中采样点的盐度一样高，萘的厌氧降解将更加稳定。同时将萘浓度从4 mg L增加至12 mg L^-1没有在类似于采样位置的咸味条件下限制生物降解效率，反而限制了在低盐度条件下发达的还原条件和生物降解过程。这突显了采样点土壤中微生物群落对咸淡环境的适应性，表明在工程硫酸盐施用过程中改变盐度可以使修复过程更容易受到环境压力和底物毒性的影响。这项研究的结果提供了对工程硫酸盐应用的一种见识，该硫酸盐作为一种补救策略，可以从受污染的微咸地下水中潜在地去除溶解的萘。