Unconventional oil and gas development (UOG) generates high volumes of flowback and produced water, byproducts of hydraulic fracturing operations, that are often released or spilled on the soil surface. Soil contamination with these wastewaters, commonly referred to as brine, has the potential to inhibit vegetation growth indefinitely. Natural attenuation of brine is not expedient in arid and semi-arid regions where most United States UOG developments are located, including the Bakken region of North Dakota. In situ (at-site) and ex situ (off-site) soil treatment techniques are commonly employed to remediate brine-contaminated soils in the Bakken. However, little is known regarding each technique's efficacy despite differences in application, cost, and efficiency. We selected 10 sites previously remediated with chemical amendments (in situ) and 11 sites with topsoil excavation (ex situ) in the United States Forest Service Little Missouri National Grasslands. We paired each remediated site with a reference to examine the ability of each strategy to return brine-contaminated sites to conditions reflective of the current state of the surrounding semi-arid rangeland ecosystem. At each site, we quantified soil electrical conductivity (ECe) as an indicator of soil salinity and measured vegetation cover, biomass production, bare ground, and litter. The difference between paired reference and remediated sites was used for analysis. Brine contamination was still evident as soil ECe was similarly increased on chemical amendment and topsoil excavation remediated sites over paired references at all soil depths tested. Due to the nature of the topsoil excavation treatment, elevated ECe in the 0-15 cm depth suggested resalinization of the new topsoil. Remediation techniques also resulted in similar plant community composition marked by an increase in exotic forb biomass, largely due to the invasion of kochia (Bassia scoparia) which was absent from reference sites. However, remediation techniques differed substantially in vegetation establishment. We found 15% more bare ground on sites remediated with chemical amendment treatment than paired references and 55% more with topsoil excavation. Our results indicate that in situ strategies may be more suitable than ex situ strategies for brine-spill remediation in semi-arid rangelands like the Bakken in North Dakota as they cause less disturbance and likely require less post-remediation management to establish adequate vegetation cover to protect the soil from further erosion.

中文翻译：

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对半干旱牧场的修复后的盐水溢出地点的土壤处理技术进行评估。

非常规的油气开发（UOG）会产生大量的倒流和产出水，这是水力压裂作业的副产品，通常会释放或溢出到土壤表面。这些废水（通常称为盐水）对土壤的污染具有无限期抑制植被生长的潜力。在大多数美国UOG开发所在的干旱和半干旱地区，包括北达科他州的巴肯地区，盐水的自然衰减是不方便的。原位（现场）和异位（非现场）土壤处理技术通常用于修复巴肯州被盐水污染的土壤。但是，尽管应用，成本和效率存在差异，但对每种技术的功效知之甚少。我们选择了10个以前用化学修正剂修复的站点（原位）和11个用表土开挖的站点（异地）在美国密苏里州小草原国家草原。我们将每个修复的地点与参考配对，以检查每种策略使受盐水污染的地点返回反映周围半干旱牧场生态系统当前状态的条件的能力。在每个站点，我们都将土壤电导率（ECe）量化为土壤盐分的指标，并测量了植被覆盖率，生物量产量，裸露地面和垃圾。配对参照位点和修复位点之间的差异用于分析。盐渍污染仍然很明显，因为在所有测试的土壤深度下，化学修饰和表土开挖修复位点的土壤ECe值均高于配对参考值。由于表土开挖处理的性质，深度在0-15厘米处的ECe升高表明新表土重新盐化。修复技术还导致了相似的植物群落组成，其特征是外来的前叉生物量增加，这主要是由于参考地点不存在的科奇亚（Bassia scoparia）入侵。但是，修复技术在植被建立方面有很大不同。我们发现，用化学改良剂处理的场地的空地比配对参考场地多15％，而表土开挖的场地多55％。