Effects of dissolved organic carbon on potentially toxic element desorption in stormwater bioretention systems

• Published in: The Science of the total environment 2024-02, Vol.912, p.168651-168651, Article 168651
• Main Authors: Al-Amin, Abdullah, Ryan, Robert J., McKenzie, Erica R.
• Format: Article
• Language: English
• Subjects: DOC; Metal; Partitioning; Runoff; Sediments; Tessier extraction
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.168651

Stormwater runoff contains dissolved organic carbon (DOC) and potentially toxic elements (PTEs). Interactions between DOC and PTEs can impact PTE speciation and mobility, but are not fully understood. Soil samples were collected from a vegetated bioretention bed to investigate the effects of DOC (0, 15, and 50 mg-C/L) on the desorption of 10 PTEs captured by the soil media: Mn, Fe, Co, Cu, Zn, As, Cd, Sn, Sb, and Pb. In the absence of DOC, the desorbed PTE concentration from bioretention media into the aqueous phase ranking was as follows: Fe > Mn ∼ Zn > Cu > Pb > Sb > As > Co > Sn ∼ Cd. Increased DOC concentrations resulted in a reduction of the soil-water distribution coefficient (Kd) values. The greatest shift in Kd was observed for Cu and lowest for Sb. The PTE sorption capacities were lower for surficial soil samples (lower Kd) compared to the deep soil samples. Overall, the desorbed PTE (average midchannel 55.7 μg/g) fraction accounted for  Cu ∼ Zn > Fe > Co > Cd > Mn.•Cd was strongly bound to soil compared to other PTEs and was less DOC-sensitive.•Desorbed/exchangeable fractions were small compared to total extracted PTEs.•DOC increased the exchangeable PTE fraction but decreased other PTE-soil fractions.