通过增强自然衰减修复砷污染地下水：批量和柱研究。
Remediation of groundwater contaminated with arsenic through enhanced natural attenuation: Batch and column studies.
机构信息
Department of Civil and Environmental Engineering, University of California, Los Angeles 5732 Boelter Hall, Box 951593, Los Angeles, CA 90095, USA.
Department of Civil and Environmental Engineering, University of California, Los Angeles 5732 Boelter Hall, Box 951593, Los Angeles, CA 90095, USA.
出版信息
Water Res. 2017 Oct 1;122:545-556. doi: 10.1016/j.watres.2017.06.029. Epub 2017 Jun 12.
Batch and column laboratory experiments were conducted on natural sediment and groundwater samples from a contaminated site in Maine, USA with the aim of lowering the dissolved arsenate [As(V)] concentrations through chemical enhancement of natural attenuation capacity. In batch factorial experiments, two levels of treatment for three parameters (pH, Ca, and Fe) were studied at different levels of phosphate to evaluate their impact on As(V) solubility. Results illustrated that lowering pH, adding Ca, and adding Fe significantly increased the sorption capacity of sediments. Overall, Fe amendment had the highest individual impact on As(V) levels. To provide further evidence for the positive impact of Ca on As(V) adsorption, isotherm experiments were conducted at three different levels of Ca concentrations. A consistent increase in adsorption capacity (26-37%) of sediments was observed with the addition of Ca. The observed favorable effect of Ca on As(V) adsorption is likely caused by an increase in the surface positive charges due to surface accumulation of Ca ions. Column experiments were conducted by flowing contaminated groundwater with elevated pH, As(V), and phosphate through both uncontaminated and contaminated sediments. Potential in-situ remediation scenarios were simulated by adding a chemical amendment feed to the columns injecting Fe(II) or Ca as well as simultaneous pH adjustment. Results showed a temporary and limited decrease in As(V) concentrations under the Ca treatment (39-41%) and higher levels of attenuation in Fe(II) treated columns (50-91%) but only after a certain number of pore volumes (18-20). This study illustrates the importance of considering geochemical parameters including pH, redox potential, presence of competing ions, and sediment chemical and physical characteristics when considering enhancing the natural attenuation capacity of sediments to mitigate As contamination in natural systems.
本研究在美国缅因州一个污染场地的天然沉积物和地下水中进行了批量和柱实验室实验，旨在通过增强天然衰减能力来降低溶解态砷酸盐（As(V)）浓度。在批量因子实验中，研究了三个参数（pH、Ca 和 Fe）的两个处理水平和不同磷酸盐水平对 As(V)溶解度的影响。结果表明，降低 pH、添加 Ca 和添加 Fe 可显著提高沉积物的吸附容量。总体而言，Fe 添加剂对 As(V)水平的个体影响最大。为了进一步证明 Ca 对 As(V)吸附的积极影响，在三个不同的 Ca 浓度水平下进行了等温实验。随着 Ca 的添加，沉积物的吸附容量（26-37%）呈一致增加。观察到 Ca 对 As(V)吸附的有利影响可能是由于表面 Ca 离子的积累导致表面正电荷增加所致。通过将具有升高 pH、As(V)和磷酸盐的受污染地下水流过未污染和污染沉积物，进行了柱实验。通过向柱中添加 Fe(II)或 Ca 以及同时进行 pH 调节，模拟了潜在的原位修复情景。结果表明，Ca 处理下（39-41%）As(V)浓度暂时且有限降低，Fe(II)处理柱中衰减程度更高（50-91%），但仅在一定数量的孔隙体积（18-20）后。这项研究说明了在考虑通过增强沉积物的天然衰减能力来减轻天然系统中砷污染时，考虑包括 pH、氧化还原电位、竞争离子的存在以及沉积物化学和物理特性等地球化学参数的重要性。
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