2017 journal article

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

SCIENCE OF THE TOTAL ENVIRONMENT, 595, 556–566.

By: N. Estrada*, J. Bohlke*, N. Sturchio*, B. Gu*, G. Harvey*, K. Burkey n, D. Grantz*, M. McGrath* ...

co-author countries: United States of America 🇺🇸
author keywords: Oxygen isotopes; Chlorine isotopes; Nitrogen isotopes; Plant uptake; Isotope fractionation in snap beans; (Phaseolus vulgaris L.); Irrigation
MeSH headings : Environmental Monitoring; Hydroponics; Nitrates / analysis; Nitrogen Isotopes / analysis; Perchlorates / analysis; Phaseolus / metabolism; Water Pollutants, Chemical / analysis
Source: Web Of Science
Added: August 6, 2018

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.