Chronic exposure of Lactuca sativa to a mine-contaminated soil from La Planta-Marayes (Argentina): II. Toxicity and bioaccumulation of Zn, Cu and Pb.

CALABRÓ MARIA ROSA; ROQUEIRO GONZALO; TAPIA, RAÚL.; CRESPO DIANA; BARGIELA, MARTHA; YOUNG BRIAN

Sao Pablo

Congreso; Congreso SETAC-L; 2017

Mine residues-associated metals may alter the survival and growth of organisms. The aim of thisstudy was to evaluate the chronic toxicity and bioaccumulation of Zn, Cu and Pb in lettuce (Lactucasativa) exposed to contaminated soil with residues from an abandoned gold mine in La Planta-Marayes. Two samples were taken from the first 20 cm of soil in La Planta town: A contaminatedsoil with mine residues (Site 1) and one located to 2 km which was used as reference (Site 2). Acompletely random experimental design consisted of 8 treatments: mixtures of soil from Site 1 and2 (dw/dw) in the range of 0.1 to 7.5% (n=6), and 2 control groups (an artificial soil recommendedby an OECD guideline, and soil sample from Site 2). Sixteen replicates for each treatment wereused. Experimental unit consisted of 1 kg of soil and a 3-week-old seedling into a flowerpot.Exposure was conducted in a greenhouse for 28 days. The hotplate aqua regia method was used toextract the pseudo total metal fraction from soil samples. Endpoints were: number of plants withcompletely necrotic aerial biomass, number of green leaves, plant?s height and width, chlorophyllcontent, stem diameter, leaf area and fresh aerial biomass. NOEC, LOEC and IC 50 or EC 50 wereestimated. After the exposure period, a microwave acid assisted extraction from aerial and rootbiomass was performed. Metal concentrations were measured with an atomic absorptionspectrophotometer. Bioaccumulation and Translocation Factors (BAF and TF) were determined.Metal concentrations in aerial biomass were compared with permissible levels established by theEuropean Union and FAO/WHO. Comparison between the control groups indicated the usefulnessof Site 2 as a reference soil for toxicity studies. Time- and concentration-dependent toxicity effectswere observed. Plant?s width and height, fresh aerial biomass, leaf area and number of green leaveswere the most sensitive endpoints (LOEC=0.1%). High concentrations of Zn (301.16 ± 14.56;1453.33 ± 381.60 μg g -1 ) were quantified in plant tissue. BAF and TF showed that metals wereaccumulated predominantly in root. A negative correlation was observed between metalconcentrations in plant tissue and toxicity endpoints. Concentrations of Zn, Cu, and Pb in aerialbiomass exceeded the permissible levels in all treatments. These results indicated a high toxicityand metal bioaccumulation in lettuce, and a potential risk to the human consumption even in thereference soil.