USE OF GEOCHEMICAL SEDIMENT DATA TO DETERMINE THE SOURCE OF CONTAMINANTS IN A RIVER IN NORTHERN MEXICO

Sediment geochemistry data (540 sampling points) acquired for a 1º x 2º quadrangle in northern Mexico were analyzed to identify the potential sources of major contaminants afflicting the Rio Conchos. These data are part of Geochemical Landscapes, a tri-national project (USA, Mexico, Canada) that has as its long-term goal completing a soil geochemical survey of North America. For our study area, the sediment samples were collected in 1999 and released in 2001 by the Servicio Geologico Mexicano. The data contains geochemical analyzes of sediments as well as data on geology, mining, and urban areas. Spatial distribution of Ca, Na, Mg, Sr were instrumental in pinpointing the sources of river salinity, a contaminant of concern due to expected concentration of salts that result from natural arid conditions, and degraded by human activities of urbanization, removal of native vegetation, and irrigation. The latter was identified as the major source of river salinity. Another contaminant of concern in this river basin is arsenic, a toxic element associated to some mineral deposits present in the area. Sediment distribution showed mine tailings as one important source of As in the basin and sewage as a second important source of As to the river. Geochemical data sets are filling a needed gap in information of remote, arid areas that lack water quality monitoring. The spatial distribution of the sources also helps in identifying the best practice methods for treatment/prevention/containment of contaminants that would mitigate pollution of this river.