Environmental impact of unleaded gasolines in the bay of Cádiz (Spain).

Given the strategic situation of the José León de Carranza bridge, which spans the Bay of Cádiz (in the SW of Spain) and carries very heavy motor traffic, together with knowledge of the currents and tidal flows in the zone, we have used a technique of radioactive dating of sediments to study the temporal evolution presented by contamination from lead in the sediment column. This has allowed us to observe the environmental impact, in terms of the concentration of Pb in the sea bed sediments, that has been produced in the zone by the introduction of unleaded gasolines as substitutes for traditional automobile fuels that employ organic forms of tetra methyl lead as an antidetonant agent in the fuel.

Assessment of urban and industrial contamination levels in the bay of Cádiz, SW Spain.

Measuring the amount of pollution is of particular importance in assessing the quality and general condition of an ecosystem. In this paper, some of the results obtained as a consequence of the specific agreement between the Environmental Agency (Consejería de Medio Ambiente, Junta de Andalucía) and the University of Cadiz to assess the environmental condition of the marine bottom and waters are showed. Physical and chemical analyses in water and sediments were undertaken at various sampling sites close to urban and industrial locations. Later on, these results were studied under statistical analysis to reveal any possible relationships between the parameters employed, and to identify any analogous behaviour between the sampling sites. Physical-chemical data revealed that sediments and waters analysed were moderately contaminated and, in addition, no great differences were found between in rising and ebbing tide conditions. Finally, considering only the pollution level, from the cluster analysis of sediments two major groups appear, one of which corresponded to those sites located in the outer bay, and the other to those situated in the inner bay. However, number 6 and 14 sampling sites cannot be associated to those groups due to be related to points with important local discharges.

Dating of marine sediments and time evolution of heavy metal concentrations in the Bay of Cádiz, Spain.

In this paper the time evolution of heavy metal concentration of Pb, Zn, Cd and Hg, in the sediments of the Bay of Cádiz (southwest of Spain) is studied during the past century, as a result of the industrial influence in the zone. The study has been performed using sedimentary profiles that have been extracted from the seabed. The measurement of 210Pb and 137Cs radionuclides has provided the dating of the sediment layers, up to a depth corresponding to the age of 115 years. The relative sedimentation rates obtained are around 0.2 cm/year. The 137Cs activity profile reflects the concentration of this radionuclide in the atmosphere and into aquatic systems during the second half of the twentieth century. This profile has been used to ratify the results provided by the 210Pb dating method.