TY - JOUR
T1 - Tracing the cycling and fate of the munition, Hexahydro-1,3,5-trinitro-1,3,5-triazine in a simulated sandy coastal marine habitat with a stable isotopic tracer, 15N-[RDX]
AU - Ariyarathna, Thivanka
AU - Ballentine, Mark
AU - Vlahos, Penny
AU - Smith, Richard W.
AU - Cooper, Christopher
AU - Böhlke, J. K.
AU - Fallis, Stephen
AU - Groshens, Thomas J.
AU - Tobias, Craig
N1 - Funding Information:
This work was funded by Department of Defense-SERDP under Project ID ER-2122 . We would like to thank D. Cady and V. Rollinson from University of Connecticut, and Janet Hannon (USGS) for analytical support. Paul Hatzinger and three anonymous reviewers provided many helpful comments on the manuscript. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Publisher Copyright:
© 2018
PY - 2019/1/10
Y1 - 2019/1/10
N2 - Coastal marine habitats become contaminated with the munitions constituent, Hexahydro-1,3,5-trinitro-1,3,5-trazine (RDX), via military training, weapon testing and leakage of unexploded ordnance. This study used 15N labeled RDX in simulated aquarium-scale coastal marine habitat containing seawater, sediment, and biota to track removal pathways from surface water including sorption onto particulates, degradation to nitroso-triazines and mineralization to dissolved inorganic nitrogen (DIN). The two aquaria received continuous RDX inputs to maintain a steady state concentration (0.4 mg L−1) over 21 days. Time series RDX and nitroso-triazine concentrations in dissolved (surface and porewater) and sorbed phases (sediment and suspended particulates) were analyzed. Distributions of DIN species (ammonium, nitrate + nitrite and dissolved N2) in sediments and overlying water were also measured along with geochemical variables in the aquaria. Partitioning of RDX and RDX-derived breakdown products onto surface sediment represented 13% of the total added 15N as RDX (15N-[RDX]) equivalents after 21 days. Measured nitroso-triazines in the aquaria accounted for 6–13% of total added 15N-[RDX]. 15N-labeled DIN was found both in the oxic surface water and hypoxic porewaters, showing that RDX mineralization accounted for 34% of the 15N-[RDX] added to the aquaria over 21 days. Labeled ammonium (15NH4 +, found in sediment and overlying water) and nitrate + nitrite (15NOX, found in overlying water only) together represented 10% of the total added 15N-[RDX]. The production of 15N labeled N2 (15N2), accounted for the largest individual sink during the transformation of the total added 15N-[RDX] (25%). Hypoxic sediment was the most favorable zone for production of N2, most of which diffused through porous sediments into the water column and escaped to the atmosphere.
AB - Coastal marine habitats become contaminated with the munitions constituent, Hexahydro-1,3,5-trinitro-1,3,5-trazine (RDX), via military training, weapon testing and leakage of unexploded ordnance. This study used 15N labeled RDX in simulated aquarium-scale coastal marine habitat containing seawater, sediment, and biota to track removal pathways from surface water including sorption onto particulates, degradation to nitroso-triazines and mineralization to dissolved inorganic nitrogen (DIN). The two aquaria received continuous RDX inputs to maintain a steady state concentration (0.4 mg L−1) over 21 days. Time series RDX and nitroso-triazine concentrations in dissolved (surface and porewater) and sorbed phases (sediment and suspended particulates) were analyzed. Distributions of DIN species (ammonium, nitrate + nitrite and dissolved N2) in sediments and overlying water were also measured along with geochemical variables in the aquaria. Partitioning of RDX and RDX-derived breakdown products onto surface sediment represented 13% of the total added 15N as RDX (15N-[RDX]) equivalents after 21 days. Measured nitroso-triazines in the aquaria accounted for 6–13% of total added 15N-[RDX]. 15N-labeled DIN was found both in the oxic surface water and hypoxic porewaters, showing that RDX mineralization accounted for 34% of the 15N-[RDX] added to the aquaria over 21 days. Labeled ammonium (15NH4 +, found in sediment and overlying water) and nitrate + nitrite (15NOX, found in overlying water only) together represented 10% of the total added 15N-[RDX]. The production of 15N labeled N2 (15N2), accounted for the largest individual sink during the transformation of the total added 15N-[RDX] (25%). Hypoxic sediment was the most favorable zone for production of N2, most of which diffused through porous sediments into the water column and escaped to the atmosphere.
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U2 - 10.1016/j.scitotenv.2018.07.404
DO - 10.1016/j.scitotenv.2018.07.404
M3 - Article
C2 - 30086489
AN - SCOPUS:85050927363
SN - 0048-9697
VL - 647
SP - 369
EP - 378
JO - Science of the Total Environment
JF - Science of the Total Environment
ER -