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(W/MF200) Arsenic mobilization in soils and sediments collected in Guadiamar River. Perez-Sirvent, Carmen1, Martinez-Sanchez, Maria-Jose1, Vidal, Josefa1, Navarro, Cortes1, Solano, Antonia1, 1 ABSTRACT- The present work reports information about the levels of As present in a number of soil and sediment samples collected in a zone located between Guadiamar River and the Donana Park border. These data were used to assess the risk of As mobilization in the ecosystem. To this purpose, 50 soil and sediment samples were collected at nine sampling stations placed along a transect normal to the river, being the samples obtained at a sampling station placed in an impolluted area used as a reference. The samples were collected at two different depths (0-5 cm and 5-20 cm) from the floodplain, the shore and the bottom of the river. The sampling was done just after the zone was submitted to a cleaning process (mechanical removing of the first 50 cm soil). In addition to general analytical determinations (pH, organic matter content, conductivity, granulometry, etc...) all the samples were submitted to selective extraction stages (water, HNO3, DTPA, Mhera- Jackson), the level of arsenic being determined in each fraction and in the raw samples by atomic absorption spectrometry. X-ray diffractometry was used to study the complex mineralogical composition and the degree of alteration of the samples after each extraction stage. The arsenic contents were in the 10-200 mg/Kg range. The data showed a relationship between the mineralogical composition of the soil and As mobilization. Thus, it was clearly proved that the higher the carbonate content in the sample the lower the As mobilization. Key words: arsenic, mobilization, AAS, X-ray diffractometry |
