Environmental Forensics in Contaminated Site Management

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1 Environmental Forensics in Contaminated Site Management Helmut Dörr, Thomas Ertel, Michaela Blessing, Holger Hansel, Rüdiger Philipps, Maria Rebel, Thomas Schöndorf Summary Forensic investigation methods are shown to be an innovative tool in contaminated site characterization. It offers a valuable contribution to cost savings in brownfield investigation and remediation. The application of the individual methods needs no special technical skills or equipment. The interpretation of forensic data needs, however, a deep knowledge and experience with these methods and an interdisciplinary understanding of geological, hydrogeological, chemical and microbial as well as fate and transport processes. Analytical capacities and senior experts are rare but available in nearly all European countries. Introduction Environmental Forensics in contaminated site management is an innovative site investigation tool for the identification of the sources (spatial and temporal) of soil and groundwater pollutions. The results of forensic investigations can be used in the development of efficient remediation strategies including monitored or enhanced natural attenuation and to identify the polluter, who could be made responsible for the remediation costs. The main methods are the so-called fingerprinting, isotopic methods, the evaluation of multi-element distribution patterns as well as the investigation and interpretation of trace substances and environmental tracers. Although the individual methods are generally known - from other than brownfield investigation applications - the combined application and interpretation of forensic methods with the aim to identify the origin and age of soil and groundwater contamination is an innovative investigation technique in brownfield characterization. Forensic methods are particularly suitable for the age-dating and the origin determination of spills with mineral oil and aromatic hydrocarbons. In addition the source of a contamination can be investigated for selected heavy metal and CHC. Forensic methods are also well suited for the reconstruction of environmental damages with TPH, Aromatic Hydrocarbons (BTEX), PAHs and heavy metals. The microbial decomposition of organic pollutants can be quantified in cases of TPH, Aromatic Hydrocarbons (BTEX), PAH, VOC and MTBE. Figure 1 gives an overview of the applications. 1

2 Figure 1: Summary of the main applications for individual groups of pollutants Methods An essential basis for the application of forensic methods is the investigation and evaluation of underground transport and dilution, as well as microbiological or chemical transformation processes. GC-MS fingerprinting and carbon isotope analysis are the most important forensic methods for the major groups of pollutants in contaminated site management. Figure 2: Degradation scheme for typical petroleum products in the environment 2

3 Figure 2 shows the degradation scheme for typical mineral oil products as an interpretation tool for spectra from gas chromatography and mass spectrometry. Other methods are the determination of isotope ratios of pure substances and elements (Sr, Nd, Pb and U) for the differentiation of pollutant sources, to determine the region of their origin. Nitrogen, boron and chlorine isotopes can be used to distinguish natural and anthropogenic. Distribution patterns of different pollutants provide information about the origin and age of a soil and groundwater contamination. Besides established and proven direct soil and groundwater investigation new more innovative methods are adopted to get a fast delineation of contaminant spreading already on-site, e.g. by direct-push techniques. The analysis of tree cores allow under certain circumstances the age-dating by combination with dendrochronolgy. Transport and transformation processes of pollutants, as well as flow and residence times of groundwater can be identified with the help of natural and artificially tracers. The application of forensic methods is demonstrated with the following two case studies, which are described in detail in "Forensische Verfahren in der Altlastenbearbeitung", Heft 14, Schriftenreihe Altlastenforum Baden-Württemberg e.v. Case Studies In the case study "TPH soil contamination", it is investigated, if a soil contamination with TPH is caused by the operation of a gas station and whether the spill dates back before or after Two soil samples were taken at different locations and analyzed for TPH, GC-MS fingerprinting and lead-isotope ratios. By this small investigation program it could be identified, that the soil contamination is caused by the operation of a gas station, and that the spill occurred after 1972.The cost of the study was around The case study "VOC in groundwater" describes the differentiation of polluters using compound-specific isotope analysis ( 13 C of CHC). In addition, the microbial degradation capacity could be determined and quantified in view of the application of a MNA-concept. 3

4 Figure 3: Distinction between various source areas (polluters) and contaminant transport using 13 C levels of PCE (modified by Blessing et al., Delineation of multiple chlorinated ethene sources in an industrialized area - A forensic field study using compound specific isotope analysis, EST, 2009). Using these methods, the main source area (not shown in figure 3) and at least four different source areas could be identified. It was also shown that there is no microbial PCE- degradation but an aerobic decomposition of TCE and cis-dce. The cost of these studies was around (R & D project). Cost-benefit aspects The cost-benefit aspects of forensic methods are highly dependent on the individual case. In any case, the forensic methods should only be interpreted in the overall context of all available data and information. Forensic site characterization methods are of specific value for environmental authorities, as contribution to a multiple reasoning process, and in decision making in insurance claims or legal proceedings. The additional costs for the forensic site characterization in the seven described case studies with applications as shown in figure 1 ranged between and The benefit of these methods depends on the goals reached. If a polluter could be identified by the use of forensic methods there is a significant benefit for all parties except for the polluter. Especially if the contribution of different polluters can be identified and is accepted by the involved parties this method is of great value. Another benefit lies in the investigation and quantification of microbiological degradation processes. In this case, value generation results from the applicability of cost efficient remediation methods. If for example, microbial degradation can be 4

5 shown to be efficient in the reduction of a contaminant plume, the implementation of "Monitored Natural Attenuation" results in cost savings compared to standard remediation technologies, and thus in a very favorable cost-benefit ratio. 5