Assessment of environmental contaminants exposure in Argentinean Patagonian scavenger birds using nonlethal samples

Abstract

Objectives The general objective of this thesis is to study metal contamination in northern Patagonia, Argentina, evaluating natural and human emission sources and evidencing possible threats to wildlife and humans. Objective 1. (Chapter I) To compile the knowledge on the use of wildlife species as biomonitor/bioindicator of environmental contamination in Latin America. Objective 2. (Chapter II) To assess the influence of anthropogenic activities on mercury exposure in scavengers' birds from Patagonia (Argentina). Objective 3. (Chapter III) To evaluate temporal trends and the volcanic activity on metal exposure in Andean condor. Objective 4. (Chapter IV) To evaluate the potential usefulness of Cathartidae of Northern Patagonia as a surrogate species for Andean condor (Vultur gryphus) and as a biomonitor regarding Hg exposure. Objective 5. (Chapter V). To evaluate temporal and spatial trends of Hg, Cd, Pb, Cu and Zn levels in the Limay River basin in anthropized and natural environments. Methodology Using scavenger bird feathers as a biomonitoring unit, we studied metal contamination in northern Patagonia, Argentina. Fresh-molted primary flight feathers (P1-P10) collected from the roosting areas were used in this research. After the processes of washing, drying, and homogenization of the samples, we have carried out the analyses. In all samples we measure the Hg levels. For the analysis of total Hg, we used 0.05 g d.w. of each feather (vane and shaft), in a nickel boats and analysed, by a Milestone DMA-8 Direct Hg Analyzer by atomic absorption spectrophotometry, with a detection limit of 0.0001 ppm, following USEPA Method 7473 (sediments, soils, and sludges). For the analysis of Si, Cr, Cu, Zn, As, Se, Cd, and Pb planned in the objective 3, the feather samples were placed in LDPE (low-density propylene) flasks with the addition of an acid mixture (nitric/perchloric/sulfuric, 8:4:1) for the organic matter disintegration (1 ml of acid mixture/100 mg of each feather). We transferred 1 ml of each predigested extract to a quartz tube, in order to dry the sample completely with a progressive heat treatment. When the tubes were cooled, we added purified water, transferring all of it to the measuring vessel, completing the final volume of 10 ml with 1% nitric acid. After digestion, the detection and quantification were performed using inductively coupled plasma optic emission spectrometry (Agilent Technologies ICP-MS. Model 7900). For the analysis of Pb, Cd, Zn, Cu planned in the chapter V feather samples were digested to be analysed by anodic stripping voltammetry (ASV). Complete digestion was ensured by using high temperature digestion with a mixture of acids following the method described by Garcia-Fernandez et al. (1995). Results In the literature review we found wide areas of Latin America lacking in ecotoxicological studies and also identified the main metals studied and the areas where these studies are concentrated. In chapters II, III, IV and V we have studied, in many cases for the first time, the levels of contamination by several metals present in the North of the Argentine Patagonia, evaluating the anthropic and natural sources. The data seems to indicate an increase in Hg levels, probably related to volcanic activity and the presence of hydroelectric dams in our study area. Conclusions Most of the results presented in this work represent first results on the different studied topics. Considering the scarcity of studies at Latin American level, its importance is to provide reference data for future research. We recommend the development of a work protocol common to all Latin American countries, so that the sharing of information between different work groups is more effective. The species studied seem to represent good options as biomonitors, contextualizing their use to specific needs. It is necessary to study more the species of our study, which given its wide distribution could allow the realization of comparable studies from different countries The temporal trends and the tendencies that seem to exist between certain species studied should be investigated more in depth, to verify their reliability and thus consent to a productive use of the surrogate species of the Andean and California condors. The Hg levels detected in the Bariloche area in the samples of black vulture (2011-2017), turkey vulture and southern crested caracara (2011) seem to represent the basal levels for the area. The real impact of Hg levels on public health and natural ecosystems in our area of study should be carefully studied. The results of our work have shown a worrying increase in levels, exceeding safety limits in some cases. Preliminary data obtained by studying chimango caracara samples seem to indicate that the species could represent a good biomonitor for ecotoxicological studies in very precise urban areas.