Biomonitoring of Cd, Cr, Hg and Pb in the Baluarte River basin associated to a mining area (NW Mexico)

Abstract

With the purpose of knowing seasonal variations of Cd, Cr, Hg and Pb in a river basin with past and present mining activities, elemental concentrations were measured in six fish species and four crustacean species in Baluarte River, from some of the mining sites to the mouth of the river in the Pacific Ocean between May 2005 and March 2006. In fish, highest levels of Cd (0.06μgg−1 dry weight) and Cr (0.01μgg−1) were detected during the dry season in Gobiesox fluviatilis and Agonostomus monticola, respectively; the highest levels of Hg (0.56μgg−1) were detected during the dry season in Guavina guavina and Mugil curema. In relation to Pb, the highest level (1.65μgg−1) was detected in A. monticola during the dry season. In crustaceans, highest levels of Cd (0.05μgg−1) occurred in Macrobrachium occidentale during both seasons; highest concentration of Cr (0.09μgg−1) was also detected in M. occidentale during the dry season. With respect to Hg, highest level (0.20μgg−1) was detected during the rainy season in Macrobrachium americanum; for Pb, the highest concentration (2.4μgg−1) corresponded to Macrobrachium digueti collected in the dry season. Considering average concentrations of trace metals in surficial sediments from all sites, Cd (p<0.025), Cr (p<0.10) and Hg (p<0.15) were significantly higher during the rainy season. Biota sediment accumulation factors above unity were detected mostly in the case of Hg in fish during both seasons. On the basis of the metal levels in fish and crustacean and the provisional tolerable weekly intake of studied elements, people can eat up to 13.99, 0.79 and 2.34kg of fish in relation to Cd, Hg and Pb, respectively; regarding crustaceans, maximum amounts were 11.33, 2.49 and 2.68kg of prawns relative to levels of Cd, Hg and Pb, respectively.