Evaluation of Equilibrium Passive Sampling Polymers for Monitoring Munition Constituents in Aquatic Systems.
Citation:
Rakowska, M., R. Burgess, AND L. Fernandez. Evaluation of Equilibrium Passive Sampling Polymers for Monitoring Munition Constituents in Aquatic Systems. Tenth International Conference on Remediation and Management of Contaminated Sediments, New Orleans, Louisiana, February 11 - 14, 2019.
Impact/Purpose:
During the period from the end of the First World War to the early 1970s, a great deal of munitions were disposed of in the marine environment. In addition, until recently, selected coastal areas were used as practice bombing ranges. Consequently, over time, a wide array of military explosive chemicals have been released from the munitions corroding in the aquatic environment. It is critical to measure these explosive chemicals and determine their ability to cause harm to the environment. In this study, a series of techniques applied with other types of environmental pollutants (e.g., PCBs) were evaluated for use in sampling these explosive chemicals. The presentation provides information on the effectiveness of the techniques for sampling explosive chemicals. Understanding how much explosive chemical is released from the munitions in aquatic systems will better inform environmental managers and allow for good decision-making.
Description:
Objectives. A wide array of military munition constituents are present in water bodies surrounding historically deposited unexploded ordnance. A common approach for monitoring explosive constituents involves the collection of large quantities of discrete water samples combined with solid phase extraction to insure sufficient sensitivity and detection. More recently, polar organic chemical integrative samplers (POCIS) have been tested for in situ assessments of munition constituents at underwater sites. However, POCIS requires extensive calibration prior to exposure in the field (i.e., determination of sampling rates). Simple and sensitive monitoring efforts are therefore necessary to better understand the bioavailability and potential long-term bioaccumulation and toxicity of military munition constituents in different aquatic environments. The objectives of this study were (1) to test the nonpolar polymers polydimethylsiloxane (PDMS), low density polyethylene (LDPE) and polyoxymethylene (POM), and a relatively polar ethylene vinyl acetate (EVA) as equilibrium passive samplers for measuring the Cfree of munition constituents, and (2) investigate and compare the use of POCIS sorbents including Oasis HLB, Ambersorb and Isolute Env+ in an equilibrium sampling approach. Approach/Activities. All polymer materials were successfully loaded in methanol followed by solvent evaporation with the munition constituents 1-nitroguanidine, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2-amino-4,6-dinitrotoluene and tetryl serving as performance reference compounds (PRCs). Loaded polymers were exposed in batch water systems spiked with the munition constituents 4-amino-2,6-dinitrotoluene, pentaerythritol tetranitrate (PETN) and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX). The release and uptake of explosive compounds was monitored in polymer and water phases over time using HPLC-MS. Results/Lessons Learned. Preliminary results suggest that the stronger affinity of PETN to PDMS may be explained by its higher octanol-water partition coefficient (log KOW = 3.7) as compared to other munition constituents in the water phase, and thus favored hydrophobic interactions with the polymer. On the contrary, dissipation of preloaded RDX (log KOW = 0.9) was much faster compared to 1-nitroguanidine (log KOW = -0.89), and likely not governed by compound hydrophobicity. The presentation provides information both on the uptake and release of explosive compounds to a variety of polymeric materials and discusses their potential for application in equilibrium passive sampling.