Sensitivity distribution profiles using organisms exposed to contaminated soil from an abandoned gold mine in La Planta-Marayes (Argentina)

YOUNG, BRIAN JONATHAN; CALABRÓ MARIA ROSA; LEMA YANINA; MILANI, PAMELA; ROQUEIRO GONZALO; GASULLA JAVIER; TAPIA, RAÚL.; MONETTA PABLO; BARGIELA, MARTHA; CRESPO DIANA

Sao Pablo

Congreso; Congreso SETAC-L; 2017

Adverse effects on human and wildlife health by exposure to mining residues havegenerated public and scientific concern. The lack of a Closure Plan in abandoned minescauses environmental pollution due to changes in the landscape and the persistence ofmetals. La Planta (Marayes, Argentina) was a small mining town until the gold minewas abandoned five decades ago. The aim of this study was to assess the toxicity ofsurface water and soil contaminated with residues from an abandoned gold mine onaquatic and terrestrial organisms. Nine sampling sites were composed by 3 samples ofwater and 6 of soil (0-20 cm). Water samples were taken on the riverbed of a tributaryof the Bermejo River (La Planta, 3 km upstream and 3 km downstream). Four soilsamples were taken in the contamination plume every 700 m from the site with miningresidues (CP1, 2, 3 and 4), and two samples in reference sites (2 km upstream and 2 kmdownstream from CP1). Surface water, soil and elutriates were characterized by routinephysicochemical determinations and metals (ICP-MS). Terrestrial organisms used wereEisenia andrei, Lactuca sativa and Raphanus sativus, and aquatic organisms wereDesmodesmus spinosus, Daphnia magna and Cnesterodon decemmaculatus. Acute andchronic toxicity tests were carried out under controlled conditions according to OECDand USEPA guidelines. Experimental design consisted of 6-10 treatments by triplicate,with sample concentrations ranging from 0.0001 to 100%, depending on eachconcentration-response curve, and a control group. Toxicity endpoints were reported asNOEC, LOEC and LC 50 , EC 50 or IC 50 . Then toxic units (TU) were calculated. Regardingall endpoints, no toxicity was observed in the water samples (pH: 8.2; EC: 6.3 mS/cm)nor in soil and elutriates of the reference sites (pH: 8.4; EC: 558 S/cm). Sensitivitydistribution profile showed that 43% of the endpoints in CP1 (pH: 2.3; EC: 41.3mS/cm) have values of EC 50 less than 1%. Reproduction inhibition of D. magna was themost sensitive endpoint (IC 50 -21d = 0.003%). TU showed positive correlations with ECand concentration of As, Bi, Cu, Zn and Pb, whereas showed negative correlations withpH. This study allowed the determination of the toxicity in soil samples and theidentification of physicochemical parameters that could cause the toxicity. However,surface water quality was no affected at this sampling time. These data will allowconducting an ecological risk assessment and proposals of remediation.