Comparing conventional and phytoscreening methods to detect subsurface chemical contaminants: A test case of volatile organic compounds in an urban setting

Abstract

The nationwide prevalence of brownfields, with often unknown types and quantities of subsurface chemical contaminants, highlights the need for rapid, cost-effective, and noninvasive methods to reduce routes of exposure. In post-industrial cities such as Detroit, Michigan, anthropogenic volatile organic compounds (VOCs), known to negatively impact human health, are typically detected at brownfields through conventional methods, e.g. screening soil, and groundwater. Recently, the method of phytoscreening–the chemical analysis of plant tissues to provide evidence for belowground contamination–has become a viable alternative to conventional methods. However, few studies have been designed to directly compare conventional and plant-based methods of detecting VOCs. To fill this knowledge gap, we sampled and compared the concentration of six VOCs including BTEX, PCE, and TCE detected in conventional media (soil, soil vapor, groundwater, sewer vapor) and different plant tissue (tree core, leaf, root, shoot) at two brownfields sites in Detroit: an abandoned gas station with a leaking underground storage tank, and a former dry cleaning facility. Our results suggest that the concentrations of VOCs detected in plants are similar to or in some cases greater than conventional methods and can differ across the growing season. For example, leaves and roots detected, on average, a higher concentration of VOCs compared to shoots and tree cores, however, TCE and PCE were generally in higher concentrations in soil and soil vapor. Moreover, the frequency at which conventional versus phytoscreening methods failed to detect VOCs was similar at one site and higher at another, suggesting that phytoscreening may yield fewer non-detects at known sites of contamination. While additional work is needed to understand the relationship between concentrations of VOCs detected in soil versus co-located plant samples, our results suggest that phytoscreening may be a viable and reliable method to detect belowground chemical contaminants while reducing screening times and cost, and increasing access to private property.