title: Zinc speciation in the suspended particulate matter of an urban river (Orge, France): influence of seasonality and urbanization gradient.
abstract: Among trace metal pollutants, zinc is the major one in the rivers from the Paris urban area, such as the Orge River, where Zn concentration in the suspended particulate matter (SPM) can reach 2000 mg/kg in the most urbanized areas. In order to better understand Zn cycling in such urban rivers, we have determined Zn speciation in SPM as a function of both the seasonal water flow variations and the urbanization gradient along the Orge River. Using TEM/SEM-EDX and linear combination fitting (LCF) of EXAFS data at the Zn K-edge, we show that Zn mainly occurs as tetrahedrally coordinated Zn(2+) sorbed to ferrihydrite (37-46%), calcite (0-37%), amorphous SiO2 (0-21%), and organic-P (0-30%) and as octahedrally coordinated Zn(2+) in the octahedral layer of phyllosilicates (18-25%). Moreover, the Zn speciation pattern depends on the river flow rate. At low water flow, Zn speciation changes along the urbanization gradient: geogenic forms of Zn inherited from soil erosion decrease relative to Zn bound to organic-phosphates and amorphous SiO2. At high water flow, Zn speciation is dominated by soil-borne forms of Zn regardless the degree of urbanization, indicating that erosion of Zn-bearing minerals dominates the Zn contribution to SPM under such conditions.
authors.affiliation: Geosciences Paris Sud (GEOPS), UMR 8148 UPS-CNRS, Campus universitaire d'Orsay Bâtiment 504 , Rue du belvédère, 91405 Orsay Cedex, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Le Pape
authors.forename: Cécile
authors.initials: C
authors.lastname: Quantin
authors.forename: Guillaume
authors.initials: G
authors.lastname: Morin
authors.forename: Delphine
authors.initials: D
authors.lastname: Jouvin
authors.forename: Isabelle
authors.initials: I
authors.lastname: Kieffer
authors.forename: Olivier
authors.initials: O
authors.lastname: Proux
authors.forename: Jaafar
authors.initials: J
authors.lastname: Ghanbaja
authors.forename: Sophie
authors.initials: S
authors.lastname: Ayrault
mesh_terms: D002947:Cities; D005602:France; D052638:Particulate Matter / Q000737:chemistry*; D045483:Rivers; D012621:Seasons; D013052:Spectrometry, X-Ray Emission; D014507:Urbanization; D014874:Water Pollutants, Chemical / Q000032:analysis; D015032:Zinc / Q000302:isolation & purification*
chemical_list: D052638:Particulate Matter; D014874:Water Pollutants, Chemical; D015032:Zinc