Hopp Luisa, Peiffer Stefan, Durner Wolfgang
Department of Hydrology, University of Bayreuth, 95440 Bayreuth, Germany.
J Contam Hydrol. 2006 May 30;85(3-4):159-78. doi: 10.1016/j.jconhyd.2006.01.005. Epub 2006 Mar 10.
Contamination of industrial sites by wood preservatives such as chromated copper arsenate (CCA) may pose a serious threat to groundwater quality. The objective of this study was to characterise the spatial variability of As and Cr concentrations in the solid phase and in the soil water at a former wood impregnation plant and to reveal the fundamental transport processes. The soil was sampled down to a depth of 2m. The soil water was extracted in situ from the vadose zone over a period of 10 months at depths of 1 and 1.5m, using large horizontally installed suction tubes. Groundwater was sampled from a depth of 4.5m. Results showed that arsenic and chromium had accumulated in the upper region of the profile and exhibited a high spatial variability (As: 21-621 mg kg(-1); Cr: 74-2872 mg kg(-1)). Concentrations in the soil water were high (mean As 167 microg L(-1); Cr: 62 microg L(-1)) and also showed a distinct spatial variability, covering concentration ranges up to three orders of magnitude. The variability was caused by the severe water-repellency of the surface soil, induced by the concurrent application of creosote wood preservatives, which leads to strong preferential flow as evident from a dye experiment. In contrast to soil water concentrations, only low As concentrations (<12 microg L(-1)) were detected in the groundwater. High Cr concentrations in the groundwater (approx. 300 microg L(-1)), however, illustrated the pronounced mobility of chromium. Our study shows that at sites with a heterogeneous flow system in the vadose zone a disparity between flux-averaged and volume-averaged concentrations may occur, and sampling of soil water might not be adequate for assessing groundwater concentrations. In these cases long-term monitoring of the groundwater appears to be the best strategy for a groundwater risk assessment.
诸如铬酸铜砷酸盐（CCA）等木材防腐剂对工业场地的污染可能会对地下水质量构成严重威胁。本研究的目的是表征某废旧木材浸渍厂固相和土壤水中砷和铬浓度的空间变异性，并揭示基本的迁移过程。土壤采样深度达2米。使用水平安装的大型抽吸管，在10个月的时间里，从渗流区1米和1.5米深度原位提取土壤水。从4.5米深度采集地下水样本。结果表明，砷和铬在剖面的上部区域积累，呈现出高空间变异性（砷：21 - 621毫克/千克；铬：74 - 2872毫克/千克）。土壤水中的浓度很高（平均砷167微克/升；铬：62微克/升），也表现出明显的空间变异性，浓度范围跨越三个数量级。这种变异性是由同时使用杂酚油木材防腐剂导致的表层土壤严重拒水性引起的，从染料实验可以明显看出这导致了强烈的优先流。与土壤水浓度相反，地下水中仅检测到低浓度的砷（<12微克/升）。然而，地下水中高浓度的铬（约300微克/升）表明铬具有显著的迁移性。我们的研究表明，在渗流区具有非均质流动系统的场地，通量平均浓度和体积平均浓度之间可能会出现差异，并且采集土壤水样本可能不足以评估地下水浓度。在这些情况下，对地下水进行长期监测似乎是地下水风险评估的最佳策略。
