Wastewater is often co-contaminated with chromium, chelating agents, and chloride. Influences of Cr3+ speciation on Cr phytoremediation by Ipomonea aquatica were investigated. MINEQL+ was employed to estimate Cr speciation. Statistic regression was used to investigate the relationships between Cr speciation and accumulation. I. aquatica accumulated high Cr concentration (13,217 mg kg−1) in the root at Cr3+ of 10 mg l−1 and EDTA of 10−4 M after 14 d growth. Pearson correlation analysis indicates that root Cr concentration significantly correlated with Cr–EDTA speciation (r = 0.67, p < 0.05) and Cr–Cl speciation (r = 0.91, p < 0.01). Shoot Cr concentration also significantly correlated with Cr–Cl speciation (r = 0.97, p < 0.01). An increase in Cl− concentration to 1.72 × 10−4 M enhanced root Cr concentration; however, the accumulation of root Cr was inhibited at high Cl− concentration (5.76 × 10−5 M). Microscopic image showed that a high portion of Cr3+ accumulated on the root surface.
