Differences among Three Plant Species in Citric Acid Induced Phytoextraction of Metals from Stormwater in a Field-Based Experiment

Citric acid is a low cost, biodegradable organic acid proven to increase uptake of metals from contaminated soils in a variety of plant species. This stormwater bioretention field experiment investigated the extent of citric acid enhanced phytoextraction among three plant species in systems of low-level, continual application contamination. Results indicated that citric acid significantly increased metal concentrations in soil pore water for the planted treatments, but did not increase metal uptake into the plant tissue. However, notable differences among species were found. Carex microptera accumulated more aluminum, chromium, copper, and iron in the above ground tissue than Helilanthus maximiliani and Typha latifolia. Results also showed that citric acid does not promote leaching of solubilized metals into the groundwater. This information will aid in the design of optimal systems to effectively slow soil metal accumulation, optimize metal recovery, and lengthen the operating life of stormwater BR systems.