WP10 Remediation Techniques and Strategies
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() Selenium dynamics in wetland restoration in the Colorado River delta, Mexico.

Garcia-Hernandez, J.1, 1 Centro de Investigacion en Alimentacion y Desarrollo, A.C.-Guaymas Unit, Guaymas, Sonora, Mexico

ABSTRACT- Naturally occurring selenium is present along the Colorado River, increasing its concentrations downstream due to evapotranspiration in dams and backwaters. This element is a nutrient, but if critical levels are exceeded, it can cause teratogenesis and reproductive problems in wildlife. The Colorado River delta wetlands are located at the southern most end of the Colorado River and consequently are the most threatened due to high selenium concentrations. We have found elevated concentrations of selenium in sediment (0.9-3.5 /g), plants (0.10 /g), fish (0.5-18.3 /g) and birds (1.7-5.3 /g) collected in four different delta wetlands, these values put at risk birds and fish species of the delta. In order to minimize these effects it is important to identify the principal sources of selenium and reduce these levels through restoration and water management. The objective of this work is to evaluate the principal sources of selenium along the most important wetlands of the Colorado River delta, in order to make recommendations to managers for the best location, hydrology and water sources to reduce selenium concentrations. Results show that in order to lower selenium concentrations, restored or created wetlands need to have a mixture of river and agriculture drain water, dredging needs to be limited due to oxidation-reduction processes, and outflows are necessary. These measures can be accomplished in a number of sites in the delta wetlands and are being addressed by local managers and bi-national organizations.

Key words: restoration, selenium, wetlands

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