|
(W/FF245) Predictive assessment of environmental hazard associated with brine discharge on western coast of Portugal. Ré, Ana1, Rodrigues, Ana1, Quintino, Victor1, 1 ABSTRACT- The process of introduction of natural gas in Portugal includes the use of salt mine caverns as storage facilities. The washing of such caverns will produce a continuous brine discharge into the coastal area of Leirosa (Western Portugal), with salinity around 300psu. This study aimed to analyse the associated potential environmental effects. The benthic communities were surveyed twice during 1999, and a series of lethal and sub-lethal bioassays were conducted. The test species were selected as a result of their local abundance or economic interest. They include the polychaets Ophelia radiata and Sabellaria alveolata, the crustacean Eurydice pulchra, the bivalve Mytilus galloprovincialis and the sea urchin Paracentrotus lividus. The crustacean Corophium multisetosum, although absent from the discharge area, was used as a test reference species. A preliminary series of assays, using brine with 36psu (diluted in distilled water) against seawater, presented drastic lethal and sub-lethal effects for all species (100%, or close, mortality, abnormal development or absence of fertilization). Another set of assays, comparing a range of concentrations obtained by mixing seawater with brine and with an artificial salt mixture, gave different results. In the lethal endpoint, both solutions presented EC50 values close to 58psu, for the majority of the test species. In the sub-lethal effects, EC50 values ranged from 38 to 40psu, in the brine solution, and from 43 to 49psu, in the artificial seawater. The dispersion model indicates that these ranges in salinity concentration will never occur (except close to the discharge area). The ecotoxicological data indicates that the biological response is not related just to an increase in salinity, but most probable, to different ionic mixtures in the brine solution, when compared to the seawater. However, given the poverty of the benthic community and the expected dilution of the brine effluent, a low impact is expected. Key words: brine discharge, lethal and sub-lethal toxicity, western Portugal |
