title: Stable isotopic composition of perchlorate and nitrate accumulated in plants: Hydroponic experiments and field data.
abstract: Natural perchlorate (ClO4-) in soil and groundwater exhibits a wide range in stable isotopic compositions (δ37Cl, δ18O, and Δ17O), indicating that ClO4-may be formed through more than one pathway and/or undergoes post-depositional isotopic alteration. Plants are known to accumulate ClO4-, but little is known about their ability to alter its isotopic composition. We examined the potential for plants to alter the isotopic composition of ClO4-in hydroponic and field experiments conducted with snap beans (Phaseolus vulgaris L.). In hydroponic studies, anion ratios indicated that ClO4-was transported from solutions into plants similarly to NO3-but preferentially to Cl-(4-fold). The ClO4-isotopic compositions of initial ClO4-reagents, final growth solutions, and aqueous extracts from plant tissues were essentially indistinguishable, indicating no significant isotope effects during ClO4-uptake or accumulation. The ClO4-isotopic composition of field-grown snap beans was also consistent with that of ClO4-in varying proportions from irrigation water and precipitation. NO3-uptake had little or no effect on NO3-isotopic compositions in hydroponic solutions. However, a large fractionation effect with an apparent ε (15N/18O) ratio of 1.05 was observed between NO3-in hydroponic solutions and leaf extracts, consistent with partial NO3-reduction during assimilation within plant tissue. We also explored the feasibility of evaluating sources of ClO4-in commercial produce, as illustrated by spinach, for which the ClO4-isotopic composition was similar to that of indigenous natural ClO4-. Our results indicate that some types of plants can accumulate and (presumably) release ClO4-to soil and groundwater without altering its isotopic characteristics. Concentrations and isotopic compositions of ClO4-and NO3-in plants may be useful for determining sources of fertilizers and sources of ClO4-in their growth environments and consequently in food supplies.
authors.affiliation: Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, TX 79409-1023, USA.
authors.forename: Nubia Luz
authors.initials: NL
authors.lastname: Estrada
authors.affiliation: National Research Program, U.S. Geological Survey, Reston, VA 20192, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Böhlke
authors.affiliation: Department of Geological Sciences, University of Delaware, Newark, DE 19716, USA.
authors.forename: Neil C
authors.initials: NC
authors.lastname: Sturchio
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Baohua
authors.initials: B
authors.lastname: Gu
authors.affiliation: U.S. Air Force, ASC/ENVR, Wright-Patterson AFB, OH 45433, USA.
authors.forename: Greg
authors.initials: G
authors.lastname: Harvey
authors.affiliation: U.S.D.A. - A.R.S., Plant Sciences Research Unit, North Carolina State University, Raleigh, NC 27607, USA.
authors.forename: Kent O
authors.initials: KO
authors.lastname: Burkey
authors.affiliation: Department of Botany and Plant Sciences, University of California, Riverside, Kearney Agricultural Center, Parlier, CA 93648, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Grantz
authors.affiliation: Plant Pathology & Plant-Microbe Biology Section, SIPS, Cornell University, Long Island Horticultural Research and Extension Center, Riverhead, NY 11901, USA.
authors.forename: Margaret T
authors.initials: MT
authors.lastname: McGrath
authors.affiliation: Department of Environmental Toxicology, The Institute of Environmental and Human Health (TIEHH), Lubbock, TX 79409-1163, USA.
authors.forename: Todd A
authors.initials: TA
authors.lastname: Anderson
authors.affiliation: Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, TX 79409-1023, USA.
authors.forename: Balaji
authors.initials: B
authors.lastname: Rao
authors.affiliation: Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, TX 79409-1023, USA.
authors.forename: Ritesh
authors.initials: R
authors.lastname: Sevanthi
authors.affiliation: CB&I Federal Services, Lawrenceville, NJ 08648, USA.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Hatzinger
authors.affiliation: Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, TX 79409-1023, USA. Electronic address: andrew.jackson@ttu.edu.
authors.forename: W Andrew
authors.initials: WA
authors.lastname: Jackson
mesh_terms: D004784:Environmental Monitoring; D018527:Hydroponics; D009566:Nitrates / Q000032:analysis*; D009587:Nitrogen Isotopes / Q000032:analysis; D010472:Perchlorates / Q000032:analysis*; D027805:Phaseolus / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D009566:Nitrates; D009587:Nitrogen Isotopes; D010472:Perchlorates; D014874:Water Pollutants, Chemical
keywords: Chlorine isotopes; Irrigation; Isotope fractionation in snap beans (Phaseolus vulgaris L.); Nitrogen isotopes; Oxygen isotopes; Plant uptake