title: Complexation between Hg(II) and biofilm extracellular polymeric substances: an application of fluorescence spectroscopy.
abstract: The three-dimensional excitation emission matrix (EEM) fluorescence spectroscopy was employed to investigate the interaction of extracellular polymeric substances (EPS) from natural biofilm with Hg(II). The EEM spectra demonstrated that EPS with molecular weight over 14 kDa had two protein-like fluorescence peaks. The fluorescence intensity at both peaks was strongly dependent on the solution pH in the absence and presence of Hg(II), with the maximal fluorescence intensity at neutral pH. Fluorescence of both protein-like peaks was significantly quenched by Hg(II). The values of conditional stability constants (log K(a)=3.28-4.48) derived from modified Stern-Volmer equation are approximate to those for humic substances and dissolved organic matter (DOM), indicating that fluorescent components in EPS have strong binding capacity for Hg(II). Our findings suggest that EPS from biofilm is a class of important organic ligands for complexation with Hg(II) and may significantly affect the chemical forms, mobility, bioavailability and ecotoxicity of heavy metals in the aquatic environment.
authors.affiliation: State Key Laboratory of Enviromental Geochemistry, Institute of Geochemistry Chinese Academy of Sciences, Guiyang, 550002, China.
authors.forename: Daoyong
authors.initials: D
authors.lastname: Zhang
authors.forename: Xiangliang
authors.initials: X
authors.lastname: Pan
authors.forename: Khan M G
authors.initials: KM
authors.lastname: Mostofa
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.forename: Guijin
authors.initials: G
authors.lastname: Mu
authors.forename: Fengchang
authors.initials: F
authors.lastname: Wu
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Song
authors.forename: Jianying
authors.initials: J
authors.lastname: Yang
authors.forename: Yanli
authors.initials: Y
authors.lastname: Liu
authors.forename: Qinglong
authors.initials: Q
authors.lastname: Fu
mesh_terms: D001419:Bacteria / Q000378:metabolism; D018441:Biofilms; D001682:Biological Availability; D004784:Environmental Monitoring / Q000379:methods; D056890:Eukaryota / Q000378:metabolism; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008628:Mercury / Q000737:chemistry*; D008670:Metals / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry; D009930:Organic Chemicals / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D014867:Water / Q000737:chemistry
chemical_list: D006812:Humic Substances; D008670:Metals; D019216:Metals, Heavy; D009930:Organic Chemicals; D011108:Polymers; D014867:Water; D008628:Mercury