Lead binding to metal oxide and organic phases of natural aquatic biofilms

Abstract

The role of the composition of surface-coating materials in controlling trace metal adsorption in aquatic environments was investigated using natural biofilms that developed on glass slides in three New York State lakes and a water-supply well. Adsorption isotherms were obtained for Pb binding to each of the biofilms in solutions with defined Pb speciation at 25ЊC and pH 6.0, with Pb concentrations ranging from 0.2 to 2.0 M. Adsorption isotherms for Pb binding to laboratory-derived metal oxides and surrogate organic materials were determined under the same conditions. These isotherms, combined with characterization of natural biofilm composition, were used to estimate the relative contributions of the organic and metal oxide surface-coating constituents by assuming additivity of adsorption to discrete adsorbing phases. Cells of a diatom (Navicula peliculosa), a green alga (Chlorella vulgaris), the bacterium Leptothrix discophora, and extracellular polymer of the bacterium Burkholdaria cepacia were tested as laboratory analogs for the organic phase of the biofilms. Amorphous Fe oxyhydroxide, ␥Al 2 O 3 , and a laboratoryderived biogenic Mn oxyhydroxide were used as laboratory surrogates for biofilm minerals. The sum total of predicted Pb binding to the defined surrogates accounted for at least 90% of the total observed Pb binding in the three lake biofilms and 60% of that observed for the well biofilms. For the lake biofilms, Pb adsorption to Fe and Mn oxides was significantly greater than that estimated for organic materials. The use of biogenic Mn oxide as a model component resulted in an estimated Pb adsorption to Mn oxyhydroxides in the lake biofilms up to four times greater than that estimated for Fe oxyhydroxide. Estimated Pb binding by Al oxide was negligible for all four biofilms. These results suggest that Fe and biogenic Mn oxides exert the greatest influence on Pb adsorption in oxic freshwater environments at pH 6.0.The cycling of transition metals in aquatic environments is controlled by adsorptive scavenging, which in turn is controlled by the composition of the aqueous phase and the reactive organic and inorganic components at surfaces

Adsorption of Pb and Cd onto metal oxides and organic material in natural surface coatings as determined by selective extractions: new evidence for the importance of Mn and Fe oxides

“…(Ghiorse, 1984). The biological composition of Cayuga Lake bio®lms is described more extensively elsewhere (Nelson, 1997;Nelson et al, 1999b). Microscopic observation after staining with Prussian Blue and Leukoberbelin Blue revealed strong associations between Fe and Mn mineral deposits and organic materials.…”

“…Cayuga Lake in central New York State (U.S.A.) was chosen as the ®eld site for collection of bio®lms because of prior bio®lm characterization by the researchers at this site (Nelson, 1997;Nelson et al, 1999b). Bio®lms developed on glass microscope slides (5.1 Â 7.6 cm) held in polypropylene racks (Fluoroware, Chaska, MN, U.S.A.) that were submerged in the lake at a depth of approximately 30 cm for a period of 4 weeks.…”

“…A fresh abiotic Mn(IV) oxide was prepared by oxidation of Mn(II) with KMNO 4 and NaOH at 908C (Murray, 1974). Al oxide was obtained commercially as gAl 2 O 3 (Alfa Products, Danvers, MS, U.S.A.) (Nelson et al, 1999b). Pb adsorption to the laboratory oxides was determined by equilibrating suspensions of the oxides with Pb solutions prepared in MMS and maintained at pH 6.0 and 258C for 24 h. Pb adsorption was determined by measuring Pb concentrations (GFAAS) before and after centrifuging at 12,900 rpm for 30 min.…”

Kinetics of Mn(II) oxidation by Leptothrix discophora SS1

“…Particulate organic material and Fe/Mn oxides have oxidation (Larsen et al, 1999;Tebo et al, 1997), no compre been identified as prominent solid phases controlling transition hensive rate equation has been proposed for microbially medi metal adsorption (Vuceta and Morgan, 1978;Luoma and ated Mn(II) oxidation kinetics. Bryan, 1981;Tessier et al, 1996;Nelson et al, 1999a;Nelson et al, 1999b;Dong et al, 2000). While trace metal adsorption Recent investigations have suggested that copper-dependent enzymes play a role in Mn(II) oxidation in three different Mn-oxidizing bacteria: Pseudomonas putida GB-1, Bacillus SG-1, and Leptothrix discophora (van Waasbergen et al, 1996;Corstjens et al, 1997;Brouwers et al, 1999;Brouwers et al, 2000a).…”

FTIR Spectroscopic Study of Biogenic Mn-Oxide Formation byPseudomonas putidaGB-1

“…Manganese oxides (MnO x ) are produced biogenically by numerous species of bacteria, including Pseudomonas putida strain GB-1, a fresh-water, facultative-aerobic, gram-negative bacteria. The formation of MnO x can influence the environmental fate of other metals (e.g., Cu, Co, Cd, Zn, Ni, and Pb) through co-precipitation and adsorption reactions (Nelson et al 1999(Nelson et al , 2002Tani et al 2003Tani et al , 2004Tebo et al 2004). The physiological basis for bacterially-mediated Mn oxidation is not known, but it is thought that biogenic MnO x may serve to protect cells from Mn or other metal toxicity (e.g., heavy metals), UV irradiation, or other potential threats (Brouwers et al 2000).…”