Metal distribution and binding in balneological peats and their aqueous extracts.
Binding of metals in typical bath peat samples ("Grosses Gifhomer Moor", Sassenburg/North Germany) and their aqueous extracts was characterized by means of a multi-method approach. For that purpose a sequential extraction procedure based on peat-filled chromatography columns was developed. Water-soluble metal and DOM (dissolved organic matter) fractions were subdivided by use of a stepwise increased pH gradient (pH 3.8-5), finally by the chelator EDTA and 0.1 mol L(-1) hydrochloric acid. Metal fractions very strongly bound to peat were assessed by an aqua regia extraction. Metal determinations required were performed by atomic spectrometry methods (AAS, ICP-OES, and TXRF). The metal and DOM concentrations in the peat extracts varied significantly, depending on the natural variety of the peat matter under study (e.g., Al: 25-674, Cd: 0.05-0.2, Cu: 5-15.4, Fe: 77-1785, Mn: 21-505, Ni: 2-33, Pb: < 1, Zn: 9-715 (microg L(-1)); Na: 8-45, K: 1.3-14.9, Ca: 2-51, Mg: 1.1-7.9 (mg L(-1)); 26-73 mg L(-1) DOC). An increase of the pH increased the DOC (dissolved organic carbon) of the peat extracts, but hardly the concentration of heavy metals. The latter could only be re-mobilized by EDTA and dilute hydrochloric acid. Additional investigations of the peat extracts using tangential-flow ultrafiltration revealed that the heavy metals extracted at pH < 4 were predominantly dissociated. At higher pH (pH > 4.5) they were preferentially bound to macromolecular DOM. Moreover, using multistage ultrafiltration the size distribution of the DOM and their metal species was assessed.
Burba
P
P
Institut für Spektrochemie und Angewandte Spektroskopie, Dortmund, Germany. burba@isas-dortmund.de
Beer
A M
AM
Lukanov
J
J
D000465:Algorithms; D002614:Chelating Agents; D004492:Edetic Acid; D008670:Metals / Q000032:analysis*; D008970:Molecular Weight; D012987:Soil / Q000032:analysis*; D013052:Spectrometry, X-Ray Emission; D013053:Spectrophotometry
D002614:Chelating Agents; D008670:Metals; D012987:Soil; D004492:Edetic Acid