ORIGINAL ARTICLE Environmental monitoring of magnetic iron phases of urban water reservoir lake sediments (Taiac ¸upeba Lake, metropolitan region of Sa ˜o Paulo, Brazil) by using Mo ¨ ssbauer spectroscopy D. R. Franco Æ T. S. Berquo ´ Æ R. A. L. Imbernon Æ C. S. M. Partiti Æ J. Enzweiler Received: 30 May 2006 / Accepted: 18 September 2006 / Published online: 11 October 2006 Ó Springer-Verlag 2006 Abstract In the present work, we investigate the iron oxides and oxyhydroxides behavior and evolu- tion, related to the geochemical behavior of some metals, which could be retained as solid phases in the sediments from an urban water reservoir lake, placed in Taiac ¸upeba, Great Sa ˜o Paulo, Brazil. These tasks were performed by the establishment of a procedur- ing setting for environmental monitoring analysis through Mo ¨ ssbauer spectroscopy measurements asso- ciated to hysteresis loops measurements and chemical analysis [X-ray fluorescence (XRF)]. We inferred the possibility of goethite occurrence in broad particle size distribution (5–50 nm), and related to ferrihy- drite, and small grain-size hematite (about 8 nm). The magnetometry results pointed to the paramagnetic/ superparamagnetic behavior of the magnetic phases present in the samples and also suggested the occur- rence of small grain-size magnetite. We also verified the presence of clay minerals related to Fe, as well as the occurrence of Fe 3+ and/or Fe 2+ in short-range structural order. Through a straight correlation among Mo ¨ ssbauer spectra data gained at T = 77 K and Al- metal, metal-Fe molar ratios, provided through XRF data, we found remarkable indications of interference on meta-stable phases evolution to its final products. Such results can be pointing for evidences about the possible isomorphic replacing and/or adsorption of Al and other metals in goethite and hematite. Keywords Sediments Á Water pollution Á Iron-bearing phases characterization Á Mo ¨ ssbauer spectroscopy Á Metropolitan region of Sa ˜o Paulo Introduction The problems concerning pollution in hydromorphic systems are related to the character of dynamic in ecosystems. Heavy metals are toxic to animals, hu- mans, and aquatic life and their toxicity, even in trace quantities have the tendency to be bioaccumulated in the food chain. In human beings when ingested and inhaled in excessive amounts, heavy metals can affect the liver, brain, and lungs, although each metal causes its own characteristic symptoms. For instance, a large range is often observed in concentrations of heavy (or D. R. Franco (&) Á T. S. Berquo ´ Á C. S. M. Partiti Laboratory of Magnetic Materials, Institute of Physics, University of Sa ˜ o Paulo—USP, C.P. 66318, 05389-970 Sa ˜o Paulo, SP, Brazil e-mail: drfranco@iag.usp.br R. A. L. Imbernon Laboratory of Hydrogeochemistry, Institute of Geosciences, University of Sa ˜o Paulo—USP, Rua do Lago 562, 05422-970 Sa ˜o Paulo, SP, Brazil J. Enzweiler Institute of Geosciences, State University of Campinas—UNICAMP, C.P. 6152, 13083-970 Campinas, SP, Brazil Present Address: D. R. Franco Department Geophysics, Institute of Astronomy, Geophysics and Atmospheric Sciences, University of Sa ˜o Paulo, R. do Mata ˜o 1226, 05508-900 Sa ˜o Paulo, SP, Brazil Present Address: T. S. Berquo ´ Institute for Rock Magnetism, Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN, USA Environ Geol (2007) 52:831–842 DOI 10.1007/s00254-006-0525-5 123