Presented at Battelle 2022 by Rock J. Vitale, CEAC, Technical Director of Chemistry/Principal
ABSTRACT
Environmental investigations typically involve the collection and analysis of samples for well-known constituents from established analyte lists. Routinely there are situations where there are multiple historical facility operators who used (and released) similar materials over the time period of their operation. With regard to the assignment of remedial cost allocations to the previous, current, or even adjacent property operators, and the identification and differentiation of sources can be quite challenging.
During an investigation of an industrial facility located adjacent to a river system, land-based and sediment residuals from manufacturing processes dating back to the 1930s were characterized for polychlorinated biphenyls (PCBs). During historical operation of the facility (1919 to 1977), two sequential operators used significant quantities of Aroclors (used to coat high-temperature copper wire), which were delivered to the site by Monsanto Company of Anniston, Alabama. Part of the current investigation identified a need to properly identify the origins of the PCBs. A fundamental tenant of environmental forensics is to carefully review historical site information because if investigators do not actively look for a source differentiator, they will likely miss it.
Review of historical records was conducted in an attempt to identify any differentiating compounds, not routinely examined in samples, that were used in the formulation, which could assist in the source allocation between the two operators. New and variable custom, Aroclor formulations that defined that era of operation contained additional chlorinated compounds and are not included on any of today’s routine analyte lists.
This work involved the method development and definitive identification of those differentiating compounds, polychlorinated terphenyls (PCTs) and polychlorinated naphthalenes (PCNs).
SITE BACKGROUND
The Site was used for the manufacture of electrical cable during World War II. For a number of years, efforts to characterize the on-site soil and river sediment residuals were limited to a generic assessment of PCB Aroclors. For purposes of remediation, this generic assessment created a cost-allocation challenge as there were two separate operators of the facility over its long history.
Examination of historical records suggested variable Aroclor mixtures were being used by the two different site operators – before and during World War II. The differences in formulations provided a potential approach to forensically differentiate the contaminant sources. Critical evaluation of the historical gas chromatography/electron capture detector (GC/ECD) data for PCBs appeared to confirm that the discrete chromatographic patterns, previously thought to be the “weathering” effect of PCBs, were suggestive of the presence of PCTs and PCNs, albeit not definitive. Based on the need to differentiate the sources of PCBs, novel definitive methods to evaluate soils and sediments for PCTs and PCNs were developed.
ANALYTICAL SYNOPSIS OF PCB AROCLORs
Extensive characterization of the on-site soils and river-based sediments was based on PCB Aroclor (as Aroclors) by GC/ECD. Aroclor mixtures are commercial formulations of individual PCB congeners (e.g., Aroclor 1248 has 48% of the biphenyl ring chlorinated). Aroclor identifications are assigned by “pattern” matching to Aroclor standards on a GC/ECD.
SITE SAMPLES REVEALED ATYPICAL PATTERNS
Two distinctly different sample types were identified that were profoundly unique in chromatographic composition. All samples were initially characterized by a routine PCB method (SW-846 Method 8082), and most were reported to contain PCB Aroclors. An example sample (“D-03”) was a good match to Aroclor 1260; however, utilizing Aroclor 1260 as the sole basis for the contaminant identification did not address chromatographic variations, which were originally thought to be “weathered” PCBs. Another example (“C-03”) appeared to contain higher halogenated, multi-component constituents versus Aroclor 1260.
INITIAL DATA ASSESSMENT
Routine SW-846 Method 8082 PCB analyses data did not represent all sample component information – particularly, later-eluting constituents. The investigative team suspected that components eluting after decachlorobiphenyl (current Method 8082 surrogate compound) were a more highly halogenated species. The extended analytical run-times provided a broader scope of the actual sample characterization. Historical site use research and literature searches revealed some possible clues.
The Monsanto Chemical Company manufactured and sold mixtures of various chlorinated aromatics under the trade name “Aroclor” during the mid to late 1900s. Depending on the specific application, the Aroclor formulations also included PCTs and, under some applications, even PCNs. Aroclors were used extensively in surface coatings, adhesives and the plastics industry because of the low cost and the desirable properties, such as adhesion, flame retardancy, chemical resistance and chemical resistance.
THE ANALYTICAL CHALLENGE
A better understanding of Aroclor formulations for manufacturing products used for different purposes seemed to be in order as, in some cases, GC/ECD analysis resulted in the “inaccurate” reporting of other Aroclors that may be present.
OTHER CHLORINATED SPECIES
Historical site research and consistent chromatographic patterns, delineated at very specific site locations, suggested the presence of PCTs and PCNs, which could be used as a discriminator for source origins. A GC/MS method was needed to identify PCTs and PCNs in samples because GC/ECD analysis could not be considered definitive.
GC/MS CHARACTERIZATION
GC/MS analysis was introduced to provide definitive information on the sample composition, elution ranges, relative chlorination percentages, and positive identification (and differentiation) of PCBs, PCTs, and, subsequently, PCNs. The analytical method included full-scan sample acquisition for identification purposes and selective ion monitoring (SIM) acquisition for the desired sensitivity and selectivity. An example standard chromatogram of PCN congeners is shown below.
For the analysis of PCTs, commercially available PCT Aroclor mixtures are currently available. Look how easily PCT Aroclor 5432 (red) in a sample could have been misidentified as “weathered” PCB 1260 (blue) if this analysis was done by GC/ECD. Extracted ion profile information shown below demonstrates typical compositions of the types of samples containing PCBs and PCTs.
Analysis of specific site samples against an Aroclor 5460 standard revealed this was the primary PCT constituent in site samples, in addition to the closely matching PCB patterns of Aroclor 1262 and 1268. This enhanced characterization successfully identified the areas of the Site that contained material specific to a site operator, which was invaluable during remedial cost allocation.
CONCLUSIONS AND LESSONS LEARNED
- An in-depth review of site (and adjacent site) history (including the parties that operated the site over time) is critical for proper source identification and to establish a timeframe during which site-related contaminants were released.
- It is important to recognize the possibility of the presence of additional sample constituents that are not on current regulatory analytical lists.
- It is important to critically evaluate and recognize atypical chromatographic patterns sometimes, it is not just PCB weathering.
- When there are questions of source contribution and cost allocation, it is appropriate to apply alternative analytical techniques.
