Metal Accumulation in American Sycamores in a Mining-Contaminated River in Southeastern Missouri
2022
Heiman, Jordan A. | Tran, Indigo T. | Behlke-Entwisle, Madeline | Pavlowsky, Robert T. | Kissoon, La Toya
The Big River, in the Old Lead Belt, southeast Missouri, experienced large-scale contamination of channel sediments and floodplain soils from over 200 years of lead mining pollution. Sediments of gravel bars downstream of mining in Big River are contaminated with Pb and Zn and have higher metal concentrations than upstream sites. Plants on these contaminated gravel bars are thus exposed to high metal concentrations and can accumulate metals. We measured multielement concentrations in leaves, branches, stems, and bark of American sycamores (Platanus occidentalis) from a contaminated and non-contaminated gravel bar in the Big River to determine the extent of metal accumulation in these trees. Element concentrations were 2–70 times higher in contaminated than non-contaminated tree parts. Contaminated sycamores were enriched with Cd, Co, Pb, and Tl in leaves; Cd, Na, Ni, Pb, Tl, and Zn in branches; Cd, Co, Pb, Tl, U, Zn, and Zr in stems; and Cd, Co, Ni, Pb, Tl, and Zn in bark (enrichment ratio >2). Contaminated bark accumulated higher concentrations of Ba, Cd, Co, Fe, Er, Ho, Li, Na, Ni, Pb, Tl, U, Zn, and Zr than other tree parts. Leaves had the highest P concentrations and the second highest concentrations of Ba, Fe, Li, Tl, U, Zn, and Zr after bark. Contaminated sycamores have the potential to disperse accumulated metals in the environment, particularly those in bark and leaves, as sycamores frequently shed these tree parts. After contaminated tree parts shed and become detritus, they can transfer accumulated metals from the sediment to food webs. The resulting detritus can change microbial and macroinvertebrate communities and subsequently inhibit decomposition in rivers.
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