Effects of soils contaminated with residues of an abandoned gold mine in Marayes (San Juan, Argentina) on Lactuca sativa and Eisenia fétida

CALABRÓ, MARÍA ROSAR; ROQUEIRO, GONZALO; RAÚL TAPIA; MONETTA PABLO; CRESPO DIANA; BARGIELA, MARTHA; YOUNG, BRIAN JONATHAN

Buenos Aires

Congreso; Congreso SETAC; 2015

Mining activities may generate environmental impact due to unplanned disposal of residues.Contaminated soils can affect the survival and growth of terrestrial organisms. The aim of thisstudy was to evaluate the effects of contaminated soils with residues of an abandoned gold mineon lettuce (L. sativa) and earthworms (E. fetida). Three sampling sites were taken from the first 20cm soil in La Planta town (Marayes): A contaminated soil with mining residues (Site 1) and twosoils used as reference, which were located 2 Km upstream (Site 2) and 2 Km downstream (Site 3)respect to Site 1. Soils were characterized through physicochemical determinations includingmetals. Toxicity tests were conducted for each organism and control group (Sites 2 and 3). Theexperimental design consisted of 8 treatments in the range of 5 to 100% and a control group forearthworm (3 replicates) and lettuce (10 replicates). Treatments were made from mixture of Site 1and control groups (dw/dw). Petri dishes containing 25 g of soil and 10 seeds of lettuce were keptin darkness and 22±1°C for 120 h. Plastic vessel with 400 g and 8 adult earthworms were placedunder indirect light (16L:8D) and 24±2°C for 14 days. The endpoints were: number of germinatedseeds, length of root and hypocotyl and number of living earthworm. IC 50 /LC 50 , NOEC, LOEC, RGIand GI were estimated. Site 1 was characterized by an acid pH (2.3) and high conductivity (41mS/cm). Metals (As, Zn, Bi, Mn, Pb, Cu, Fe and Co) were more concentrated in Site 1 related toSites 2 and 3. The IC 50 sensitivity in toxicity test with Site 2 were: root elongation (14.95%) >hypocotyl elongation (15.54%) > seed germination (26.27%); whereas in toxicity test with Site 3were: seed germination (4.04%) > hypocotyl elongation (22.11%) > root elongation (16.62%). TheGI 50% concentration in Site 2 (10.41%) was higher than in Site 3 (2.94%), which was affected by theseed germination. Regarding earthworms, LC 50 in Site 2 (10.00%) was higher than in Site 3 (3.53%).Lethal effects were observed on earthworms and seeds (necrotic seeds) from 15% and 40%respectively. Site 3 showed higher toxicity than Site 2, although no significant statisticaldifferences were found. Physicochemical parameters of the contaminated soil indicate a highbioavailability of metals due to the low pH and high salinity. Changes in the values of theseparameters could be associated to the intensity of effects observed on survival and growth of thestudied organisms.