HEAVY METALS AND ARSENIC CONTAMINATION IN LA BARRA DE SANTIAGO ESTUARY, EL SALVADOR

Geochemical analysis was carried out on samples of environmental phases (water, sediments, soils, and one macroinvertebrate specie) from La Barra de Santiago estuary (El Salvador, Central America). This estuary has been impacted by a high amount of ash transported to the area after the 2005 eruption of Santa Ana volcano, and intensified agriculture and application of agrochemicals. Macroinvertebrates populations have declined considerable. Sediments, soils and macroinvertebrates (curils) were digested to extract the heavy metals and arsenic and were analyzed using ICP-MS, nutrients and sulfate were also analyzed in sediments, soils and water. Low concentration of sulfate in the water and sediments suggest it is unlikely that sulfur contamination due to the eruption of Santa Ana volcano in 2005 could be causing the lack of macroinvertebrates in the region. Statistically significant relationships between Sr, Rb and Cl, and between Sr, Rb and SO4, suggest a chemical contribution from marine sources for these elements, while correlation between Fe, Cu, Cd, Zn, Cr, Ce, Co and Al indicates inland input into the ecosystem for these metals. Results from sediment quality assessments using several pollution indices such as geoaccumulation index (Igeo), mean-ERM quotient, concentration factor (CF), pollution load index (PLI), and contamination Factor (Cf) shows the presence of high Ni and Cr concentration in the ecosystem which could be responsible for the lack of macroinvertebrates in the estuary. Arsenic was high in the different environmental phases, particularly in the curils with concentration ranging from 224 to 287 ug/g. Cadmiun, Cu, Cr, Ni, Sr, Rb, and Pb were also high compared with values reported in the literature, with Cd ranging from 819 to 5290 ug/g. Contamination from natural sources (e.g. arsenic) and agrochemicals is probably responsible for the declining population of macroinvertebrates.