title: Redox-induced mobilization of copper, selenium, and zinc in deltaic soils originating from Mississippi (U.S.A.) and Nile (Egypt) River Deltas: A better understanding of biogeochemical processes for safe environmental management.
abstract: Studies about the mobilization of potentially toxic elements (PTEs) in deltaic soils can be challenging, provide critical information on assessing the potential risk and fate of these elements and for sustainable management of these soils. The impact of redox potential (EH), pH, iron (Fe), manganese (Mn), sulfate (SO42-), chloride (Cl-), aliphatic dissolved organic carbon (DOC), and aromatic dissolved organic carbon (DAC) on the mobilization of copper (Cu), selenium (Se), and zinc (Zn) was studied in two soils collected from the Nile and Mississippi Rivers deltaic plains focused on increasing our understanding of the fate of these toxic elements. Soils were exposed to a range of redox conditions stepwise from reducing to oxidizing soil conditions using an automated biogeochemical microcosm apparatus. Concentrations of DOC and Fe were high under reducing conditions as compared to oxidizing conditions in both soils. The proportion of DAC in relation to DOC in solution (aromaticity) was high in the Nile Delta soil (NDS) and low in the Mississippi Delta soil (MDS) under oxidizing conditions. Mobilization of Cu was low under reducing conditions in both soils which was likely caused by sulfide precipitation and as a result of reduction of Cu2+to Cu1+. Mobilization of Se was high under low EHin both soils. Release of Se was positively correlated with DOC, Fe, Mn, and SO42-in the NDS, and with Fe in the MDS. Mobilization of Zn showed negative correlations with EHand pH in the NDS while these correlations were non-significant in the MDS. The release dynamics of dissolved Zn could be governed mainly by the chemistry of Fe and Mn in the NDS and by the chemistry of Mn in the MDS. Our findings suggest that a release of Se and Zn occurs under anaerobic conditions, while aerobic conditions favor the release of Cu in both soils. In conclusion, the release of Cu, Se, and Zn under different reducing and oxidizing conditions in deltaic wetland soils should be taken into account due to increased mobilization and the potential environmental risks associated with food security in utilizing these soils for flooded agricultural and fisheries systems.
authors.affiliation: University of Kafrelsheikh, Faculty of Agriculture, Department of Soil and Water Sciences, 33 516 Kafr El-Sheikh, Egypt; University of Wuppertal, Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany. Electronic address: smshaheen@agr.kfs.edu.eg.
authors.forename: Sabry M
authors.initials: SM
authors.lastname: Shaheen
authors.affiliation: University of Wuppertal, Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; University of Bielefeld, Department I: Planning and Controlling, Universitätsstraße 25, 33615 Bielefeld, Germany. Electronic address: t_frohne@yahoo.de.
authors.forename: Tina
authors.initials: T
authors.lastname: Frohne
authors.affiliation: Louisiana State University, Department of Oceanography and Coastal Sciences, College of the Coast and Environment, 3239 Energy, Coast and Environment Building, Wetland & Aquatic Biogeochemistry Laboratory, Baton Rouge, LA 70803, USA. Electronic address: jrwhite@lsu.edu.
authors.forename: John R
authors.initials: JR
authors.lastname: White
authors.affiliation: Louisiana State University, Department of Oceanography and Coastal Sciences, College of the Coast and Environment, 3239 Energy, Coast and Environment Building, Wetland & Aquatic Biogeochemistry Laboratory, Baton Rouge, LA 70803, USA. Electronic address: rdelaun@lsu.edu.
authors.forename: Ron D
authors.initials: RD
authors.lastname: DeLaune
authors.affiliation: University of Wuppertal, Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany. Electronic address: rinklebe@uni-wuppertal.de.
authors.forename: Jörg
authors.initials: J
authors.lastname: Rinklebe
mesh_terms: D003300:Copper / Q000032:analysis* / Q000737:chemistry; D004534:Egypt; D007501:Iron / Q000032:analysis / Q000737:chemistry; D008345:Manganese / Q000032:analysis / Q000737:chemistry; D008922:Mississippi; D010084:Oxidation-Reduction; D045483:Rivers; D012643:Selenium / Q000032:analysis* / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*; D053833:Wetlands; D015032:Zinc / Q000032:analysis* / Q000737:chemistry
chemical_list: D012987:Soil; D012989:Soil Pollutants; D008345:Manganese; D003300:Copper; D007501:Iron; D012643:Selenium; D015032:Zinc
keywords: Floodplain soils; Potentially toxic elements; Redox chemistry; Specific UV absorbance (SUVA); Wax Lake Delta