Subsurface imaging using a combination of magnetic, ERT, TEM, and CSRMT data at the Weidenpesch waste site in Cologne

填埋场的地球物理特性是场地补救的一个重要程序。如今，使用非破坏性和非侵入性地球物理技术探测废物体和成像污染羽流，已明显增加。在德国科隆/德国西北部的Weidenpesch废物场，在DFG项目TE 170/21-1的框架内测量了磁性、ERT、TEM和CSRMT数据。测量被推迟了几个月（c。由于COVID-19疫情期间的旅行限制以及改变位于俄罗斯的原计划中选择的调查垃圾填埋场的决定，该项目预计将持续9个月。这影响了在规定时间内实现计划目标。通过对磁、ERT和TEM数据的综合解释，我们成功地确定了Weidenpesch垃圾填埋场废物体的几何形状。此外，倾倒的磁性和非磁性材料明显区分。用于确定废物场水平边界的不同技术显示出很好的一致性。研究结果表明，与高电阻托管砾石砂层相反，倾倒的材料具有低电阻率值，使其更容易成像的废物体。利用ERT和TEM数据，在较深的深度处发现了一个有趣的、非常导电的层（小于5 Ω.m）。根据现有的钻孔和地质信息，该层被解释为湿棕色褐煤层。它在20-25米的深度被发现，它的底部没有被使用的技术发现。这一层的电阻率无法分辨。本次拟建项目（工期6个月）将重点采用比现有大的回线探测煤层基底，在填埋场内外规划8个50 m × 50 m甚至80 m × 80 m回线的TEM台站。此外，还将进行TEM数据的2D/3D建模，并将从大型回线站获得的TEM数据纳入建模研究。此外，还将利用ERT、磁力和CSRMT的约束条件。将应用有限元算法CustTEM和众所周知的有限差分算法SLDMem 3 t。最后，将所使用的不同地球物理技术的结果结合起来，将有助于改进废物体的成像，更准确地说，有助于追踪任何潜在的污染物羽流。因此，这一战略将是非常有用的风险评估和建立最终的模型的垃圾填埋场。

Geophysical characterization of landfills represents an important procedure in site remediation. Nowadays, the use of non-destructive and non-invasive geophysical techniques directed toward detecting the waste body and imaging contamination plumes, has been clearly increased. In the Weidenpesch waste site, northwest of Cologne/Germany, magnetic, ERT, TEM, and CSRMT data were measured in the frame of the DFG project TE 170/21-1. The measurements were delayed for several months (c. 9 months) because of the travel restrictions during the covid-19 epidemic and the decision of changing the investigated landfill chosen in the original plan located in Russia. This influenced the achievement of the planned goals within the allotted time. By the integrated interpretation of magnetic, ERT, and TEM data we were able to successfully determine the geometry of the waste body of the Weidenpesch landfill. Additionally, dumped magnetic and non-magnetic materials were obviously distinguished. The different techniques used for determining the waste site's horizontal boundaries showed a good degree of consistency. The findings demonstrate that, in contrast to the highly resistive hosting gravelly sand layer, the dumped materials have low resistivity values making it easier to image the waste body. An interesting, very conductive layer (less than 5 Ω.m) has been found at deep depths using ERT and TEM data. This layer was interpreted as a wet brown lignite layer based on the available borehole and geological information. It is detected at a depth up of 20-25 m and its base wasn’t detected by the used techniques. The resistivity of this layer could not be resolved. The current proposed project (duration 6 months) will focus on detecting the base of the coal layer using larger loops than the used ones; eight TEM stations with loops of 50m × 50m or even 80m × 80m inside and outside the landfill are planned. Moreover, 2D/3D modelling of TEM data will be carried, and the TEM data obtained from large-loop stations will be integrated in the modelling study. Furthermore, constraints from ERT, magnetic and CSRMT will be utilized. The finite element algorithm CustTEM and the well-known finite difference algorithm SLDMem3t will be applied. Finally, combining the findings from the different used geophysical techniques will aid in improving the imaging of the waste body and, more precisely, in tracing any potential contaminant plumes. Thus, this strategy will be quite useful in risk assessment and constructing the final model of the landfill.