Toxicity of elutriates from soils contaminated with residues from an abandoned gold mine in Marayes (San Juan, Argentina) on Lettuce and Radish

. MILANI, PAMELA; ROQUEIRO, GONZALO; TAPIA, RAÚL.; MONETTA PABLO; CRESPO DIANA; BARGIELA, MARTHA; YOUNG, BRIAN JONATHAN

Buenos Aires

Congreso; Congreso SETAC; 2015

Inadequate processes of mine closure can contaminate the environment due to a lack of planning of waste disposal. Currently, adverse effects on human and wildlife health by exposure to mining residues have generated public and scientific concern. Accumulation of these residues without treatment on the soil may affect terrestrial plants used for human consumption. The aim of this study was to assess the toxicity of elutriates obtained from soils contaminated with residues from an abandoned gold mine on seeds of lettuce (Lactuca sativa) and radish (Raphanus sativus). The first 20 cm of soil from 6 sampling sites were taken in La Planta town (Marayes): 4 sites with 700 m of distance on the contamination plume (Sites 1, 2, 3, and 4) and 2 sites of reference (A: 2 km upstream; and B: 2 km downstream from Site 1). The elutriates (soil: deionized water in relation 1:4) were characterized by physicochemical determinations. Toxicity tests were carried out using seeds of lettuce and radish, according to a standard protocol. Experimental design consisted in 11 treatments by triplicate for each species: ten elutriate concentrations in a range of 0.01 to 100%, and a control group. Fifteen seeds and 4 mL of an elutriate concentration or control water were collocated on germination paper in a Petri dish and were incubated for 120 h at 22 ± 1°C in darkness. The evaluated endpoints were germination percentage and root and hypocotyl elongation. Then, IC50, NOEC, LOEC and two phytotoxicity indices were estimated: RGI (Relative Growth Index) and GI (Germination Index). Results showed that the endpoint sensitivity of all sampling sites and test species was: root elongation > hypocotyl elongation > germination percentage. Reference site A showed no toxicity on lettuce, whereas showed inhibition of the root elongation and germination percentage on radish (concentration of GI80 = 75.5% and RGI0.8 = 75.5%). However, reference site B showed toxicity on lettuce (concentration of GI80 = 23.1% and RGI0.8 = 23.7%). Site 1 on the contamination plume showed higher toxicity (IC50 = 0.26% on lettuce and IC50 = 2.67% on radish) than the other sites for all endpoints in both species. Toxicity endpoints correlated negatively with pH and positively with electrical conductivity and concentration of heavy metals. Our results could be useful for the future planning of the soil use for family farming in La Planta town.