Project #: 22-157 | Year 1 of 1
Reagan Turley, Hillary Tarvin
Nevada National Security Site (NNSS)
The ability to detect and characterize explosives testing and possible nuclear proliferation efforts using biochemical methods is a primary concern for Global Security. By testing residual chemicals in the soil and plants near a testing site, bioindicators can be developed to inform verification teams as to the type of development activity that may be occurring there. Using mass spectrometry methods, including gas chromatography mass spectrometry (GCMS), and inductively coupled plasma mass spectrometry (ICP-MS), biochemical patterns of life will be developed at explosive testing sites across the Nevada National Security Site (NNSS).
While several commercial off the shelf (COTS) products exist for testing of the presence of explosive components and residues, they tend to yield false positives on samples where naturally occurring nitrates may be present, such as soil, and will often fail to register degraded compounds such as those that will be present after exposure to weathering and other environmental factors. In addition, most COTS test kits rely on direct contact with explosive residues, which may be impossible to achieve if the material has already been taken up into the biota present at the testing site. It may be necessary to extract the explosive residue and its degradation products from the soil or plant life surrounding a suspected explosive testing or activity site. In these cases, the concentration of such materials may fall below the nanogram level sensitivity of many testing kits and a different form of analysis may be required. GCMS is an analytical technique that combines the separation properties of gas-liquid chromatography with the detection feature of mass spectrometry to identify different substances within a test sample (Chauhan, Goyal, and Chauhan 2014). It is a commonly used tool for monitoring and tracking organic pollutants in the environment, and achievement of sub part per trillion limits of detection is not impossible given the right experimental conditions.
In 2014, the NNSS acquired an Agilent 7890 GC and a 5977 MS; however, the project for which the instrumentation was originally acquired was discontinued and the GCMS became unused. To align with the goal of this project in developing a novel approach for determining a biochemical pattern of life at explosive testing sites at the NNSS, samples of chemical residues were analyzed with the GCMS to increase our understanding of how plants and soil preserve the chemical signature of explosives testing activities. The collection, digestion, and analysis of soil and plant samples yield a unique view of what events have taken place at such a site in the past based upon how quickly local plants uptake residues from recent testing, and how weather in the local environment impacts uptake.
The first phase of this project was focused on re-establishing the operational capabilities of the NNSS GCMS laboratory from a facility, instrument, and personnel standpoint. Numerous aspects of the Materials Testing Laboratory had to be re-certified, the GCMS had to be repaired and reconfigured, and new personnel had to be trained to operate the instrument.
After the facility was returned to a useable state for laboratory purposes, project personnel attended training from Agilent, the instrument manufacturer. For the purposes of this project and to better serve the future biochemical analysis needs of the NNSS, the GCMS was reconfigured for electron impact ionization to be able to handle the sampling of both gases and liquids. Once the GCMS passed a tune, several standards were analyzed and compared against a National Institute of Standard and Technology library to verify operation.
During the second phase of this project, two NNSS explosive sites were selected for soil sampling: the Aerial DAS [Distributed Acoustic Sensing] Infrasound Test (ADIT) pad, which played host to two detonations of C-4, each consisting of several hundred pounds of explosive material in 2021; and the Explosive Ordinance Disposal Unit (EODU) which was used for the destruction of 13 different explosive articles in 2021. Laboratory procedures were then developed to extract potential compounds of interest from the soil samples. These extraction procedures were based off Environmental Protection Agency (EPA) Method 8330, which covers the extraction and analysis of nitroaromatic, nitroamine, and nitrate esther compounds by high performance liquid chromatography.
A method for GCMS analysis was then developed utilizing EPA Method 8095, which covers the analysis of explosives by gas chromatography. The method was used to analyze the extractants of the samples from the ADIT and EODU sites. While none of these compounds match any of the known decomposition or degradation products examined, the presence of nitrogen, nitrite, and cycloalkane functional groups is of potential interest since southern Nevada soil has little naturally occurring nitrogen. However, further experimentation is required to clean up the sample compositions, improve the GCMS methodology, and refine the spectral features acquired during analysis to identify the compounds more positively.
Over the course of this project, organic chemical analysis capability through GCMS was returned to the NNSS. Through the efforts of the project team, an underutilized asset and laboratory space were restored to operational capability and three new personnel were trained on GCMS troubleshooting, repair, operation, and data analysis. Work was then undertaken to develop a novel approach for determining a biochemical pattern of life at explosive testing sites at the NNSS through the understanding of how plants and soil preserve the chemical signature of explosives testing activities. Sampling, extraction, and analysis methodologies were created and executed, and initial results yielded some interesting features for further investigation regarding the potential persistence of explosive compounds and decomposition products within the soils of the NNSS.
The NNSS is now able to perform biochemical analysis on a sampled item quickly and easily without needing to send the sample off site to another lab, which would result in additional cost and schedule delays. Initial work was also conducted into understanding the biochemical fingerprints that may be left behind in an environment by explosives testing associated with nuclear weapons research. The GCMS is now operational and ready for use by other projects that seek organic chemical analysis of samples generated by or collected on the NNSS. Initial efforts were made to understand how plants near chemical explosions uptake residues from soil, allowing them to preserve a biochemical pattern of life that could be studied for detection and understanding of clandestine activities resulting in nuclear proliferation risks.
Chauhan, A., M. K. Goyal, P. Chauhan. 2014. “GC-MS Technique and its Analytical Applications in Science and Technology.” J Anal Bioanal Tech. 5: 222. https://doi.org/10.4172/2155-9872.1000222.
This work was done by Mission Support and Test Services, LLC, under Contract No. DE-NA0003624 with the U.S. Department of Energy. DOE/NV/03624–1647.