QUALITY OF SEDIMENTS ASSOCIATED WITH ANTHROPICAL ACTIVITIES IN SUBTROPICAL SEMI-ARID COASTAL LAGOONS OF THE CENTRAL COAST OF THE GULF OF CALIFORNIA

The quality of the superficial sediments of the coastal lagoons of Lobos and Tobari, both in the central-east zone of the Gulf of California, Mexico, and receptors of sewage effluents from the Yaqui Valley, was evaluated. The comparison was carried using the coastal lagoon of el Soldado, as a reference site, on account of being a natural protected area, which does not receive anthropogenic unloads. The levels of nickel, zinc, copper, cadmium, manganese, lead and iron were determined. The enrichment factor (EF), the metallic pollution index (MPI) and the index of geoaccumulation (I-geo) were calculated. Besides the guidelines of sediment quality (SQV) were used to assess the concentrations of metals that can cause a potential risk to the marine biota health. Lagoon Lobos obtained significantly higher levels of zinc (70.1 mu g/g) and copper (16.3 mu g/g), Tobari had the highest mean of manganese (747 mu g/g). El Soldado had the lowest mean of iron (1.05 %) and the lowest value of MPI. In Lobos and Tobari, manganese was the only metal with an EF, which indicates anthropogenic influence, and it also had an I-geo index of moderate. The sites most affected in both lagoons were the nearest to the agricultural zones. The SQV suggests that there must be a track of nickel levels > 51.6 mu g/g (registered once in Lobos) and of manganese levels > 260 mu g/g (Lobos and Tobari). Concentrations over those levels can cause adverse effects on the marine environment such as the deterioration of the natural conditions that support the reproduction, breeding, and protection of the species that live there.