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Stable isotopic composition of perchlorate and nitrate accumulated in plants: Hydroponic experiments and field data

April 19, 2017

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 ClO4and NO3 in plants may be useful for determining sources of fertilizers and sources of ClO4 in their growth environments and consequently in food supplies.

Publication Year 2017
Title Stable isotopic composition of perchlorate and nitrate accumulated in plants: Hydroponic experiments and field data
DOI 10.1016/j.scitotenv.2017.03.223
Authors Nubia Luz Estrada, John K. Böhlke, Neil C. Sturchio, Baohua Gu, Greg Harvey, Kent O. Burkey, David A. Grantz, Margaret T. McGrath, Todd A. Anderson, Balaji Rao, Ritesh Sevanthi, Paul B. Hatzinger, W. Andrew Jackson
Publication Type Article
Publication Subtype Journal Article
Series Title Science of the Total Environment
Index ID 70187013
Record Source USGS Publications Warehouse
USGS Organization National Research Program - Eastern Branch