title: Exploiting biogeochemical and spectroscopic techniques to assess the geochemical distribution and release dynamics of chromium and lead in a contaminated floodplain soil.
abstract: Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) combined with a seven steps sequential extraction technique were used to assess the geochemical distribution of chromium (Cr) and lead (Pb) in a contaminated floodplain soil. Total contents of Cr and Pb were 490.3 and 402.1 mg kg(-1), respectively. The residual fraction was 59.5 and 56.3% of total Cr and Pb. The crystalline iron (Fe) oxide was the dominant non-residual fraction of Cr (35.9% of total Cr). Considerable amounts of Pb were found in the organic fraction (35.4%). Using (13)C nuclear magnetic resonance spectroscopy, the soil organic matter was identified as 48.9% aromatic carbon, which indicated that a certain portion of Pb and Cr might be associated with aromatic compounds. The SEM-EDX images demonstrate a concomitant occurrence of Pb, manganese (Mn), Fe, and aluminum (Al) as well as a coexistence of Cr and Fe. The release dynamics of dissolved Cr and Pb as affected by redox potential (EH), pH, Fe, Mn, dissolved organic carbon, and sulfate was quantified using an automated biogeochemical microcosm apparatus. Soil pH decreased under oxic conditions. The release of Cr, Pb, Fe, and Mn increased under acidic oxic (pH = 3.7, EH = 521 mV) conditions due to the associated decrease of pH (7.1-3.7). The mobilization of Cr and Pb was affected by the Fe and Mn. In conclusion, our multi-technique approach identified the geochemical distribution of Cr and Pb and verified major factors that explain mobilization of Cr and Pb in floodplain soils.
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
authors.affiliation: University of Wuppertal, Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; University of Kafrelsheikh, Faculty of Agriculture, Department of Soil and Water Sciences, 33516 Kafr El-Sheikh, Egypt.
authors.forename: Sabry M
authors.initials: SM
authors.lastname: Shaheen
authors.affiliation: University of Wuppertal, Environmental Safety, Rainer-Gruenter-Strasse, 42119 Wuppertal, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Schröter
authors.affiliation: Department of Soil Chemistry and Pedology, Institute of Soil Science and Land Evaluation University of Hohenheim, Emil-Wolff-Str. 27, 70599 Stuttgart, Germany.
authors.forename: Thilo
authors.initials: T
authors.lastname: Rennert
mesh_terms: D002857:Chromium / Q000032:analysis*; D055868:Floods; D005858:Germany; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000032:analysis; D007700:Kinetics; D007854:Lead / Q000032:analysis*; D008855:Microscopy, Electron, Scanning; D045483:Rivers / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis*; D013052:Spectrometry, X-Ray Emission; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D002857:Chromium; D007854:Lead; D007501:Iron
keywords: Mobilization; Nuclear magnetic resonance spectroscopy (NMR); Scanning electron microscope coupled with energy dispersive X-ray analysis (SEM–EDX); Toxic metals; Wetlands