Phytoscreening for perchlorate: rapid analysis of tree sap

Abstract

Perchlorate presents an environmental health risk due to its widespread use, high solubility in water, and ability to interfere with thyroid function in humans. Delineating plumes of mobile contaminants, such as perchlorate, is difficult and time consuming, particularly in remote or forested areas. Phytoscreening, the analysis of contaminants in tree tissues for plume delineation, has been previously applied to shallow chlorinated solvent groundwater plumes and provides a promising alternative to traditional delineation techniques. To test the potential of phytoscreening for perchlorate, a sensitive freeze centrifugation sampling method coupled with ultra-fast ion exchange chromatography tandem mass spectrometry (UFIC-MS/MS) detection was developed. An initial hydroponic greenhouse test using willow cuttings demonstrated concentrations of perchlorate in tree sap were proportional to the perchlorate exposure concentration. Eighty-six tree cores obtained in the field contained measureable amounts of perchlorate, and the distribution of perchlorate in trees reflected the distribution of perchlorate in the groundwater. Perchlorate concentrations in the tree cores were loosely correlated with the groundwater as demonstrated by cross-covariograms and linear regression. Correlations between tree and groundwater perchlorate concentrations were similar in magnitude to tree and groundwater trichloroethylene (TCE) concentrations, implying a similar level of performance between perchlorate and TCE phytoscreening at this site. Phytoscreening of perchlorate was sufficiently accurate to be used as a screening tool to delineate perchlorate contaminated groundwater.