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(W/MF189) HEAVY METAL CONTAMINATION AND SOIL MICROBIOLOGICAL INDICATORS IN A RIPARIAN ECOSYSTEM AFFECTED BY THE AZNALCOLLAR MINE SPILL. Hinojosa, Belén1, Carreira, José1, García-Ruiz, Roberto1, 1 ABSTRACT- In April 1998, the residues pond of the Aznalcollar mine collapsed, and 2 Hm3 of piritic muds and 4 Hm3 of acid and heavy metal-enriched waters were released into the Agrio river affecting over 4.600 Ha of the Guadiamar basin (SW Spain). Restoration practices during the following years included the withdrawal of piritic muds and top-soils over most of the affected area, and subsequent liming of the remaning soils. A research programme was then setted up for the short-to-medium term monitoring of residual contamination and post-impact recovery, using a wide variety of chemical and biological indicators. Soil microbiota plays a central role in the biogeochemical cycling of major nutrients; and is also known to be very sensitive and short-term responsive to heavy-metal stress. Thus, microbial and enzimatic activities related to the C, N and P cycling were selected as key variables to assess the initial stage of recovery of the biological component of restored soils. In this study, we report on general (N- mineralization, nitrification, denitrification and respiration) and especific (phosphatase, deshidrogenase, B-glucosidase and arilsulfatase) biochemical properties of soils in a set of study plots representing comparable riparian ecosystems which were either i) unaffected by the piritic-mud flood (reference plot), ii) affected but subsequently cleaned (treated plot) or iii) affected and left with the mud on top of the soil (control plot). Taking results from the unaffected plot as reference values and those from the "mud-left" plot as control values, data are discussed in terms of the degree of early recovery achieved after restoration practices were carried out Key words: Heavy metals, Aznarcollar, Microbiological activities, soil |
