Papers by Sergio Ribeiro Guevara
Marine Pollution Bulletin, 2022
The dynamics of contaminants, such as mercury (Hg), in marine trophic webs is a critical topic in... more The dynamics of contaminants, such as mercury (Hg), in marine trophic webs is a critical topic in the scientific community due to the high concentrations encountered in organisms. In this study we attempted to provide information on total Hg accumulation patterns and possible pathways of trophic transfers assessed in combination with δ13C and δ15N to understand how this contaminant permeates three sub-Antarctic food webs: the Beagle Channel (BC), the Atlantic coast of Tierra del Fuego (AC-TDF) and Burdwood Bank (BB). We found a sitespecific pattern of Hg transfer and biomagnification processes, while the oceanic BB showed major Hg transfer through the pelagic domain, coastal sectors (BC and AC-TDF) indicate a general biodilution process but with Hg concentrations incrementing with the benthivory grade. This represents a dissimilar Hg bioavailability for marine consumers that rely on different diet and forage in different habitats, and may become an issue of important conservation concern for these southern areas.
Journal of Soils and Sediments, 2022
Purpose The main objective of the study was to assess the environmental quality status of the sed... more Purpose The main objective of the study was to assess the environmental quality status of the sediments of eleven Patagonian lakes regarding the concentrations of five trace elements, evaluating the influence of volcanic activity and water and sediment parameters on element concentration and distribution. Materials and methods Surface sediment samples from 11 lakes were collected at different depths for granulometric analysis, organic matter (OM) contents, and determination of As, Br, Cr, Hg, Ni, and Zn concentrations. Physicochemical variables of the water column were also measured. The quality of the sediments and the potential ecological risks were assessed by comparing the concentrations of elements with local and global geochemical background values and with consensus-based sediment quality guidelines and through the calculation of environmental quality indices (enrichment factor and index of geo-accumulation). Results and discussion A higher proportion of sand with a lower %OM characterized the surface sediments in lakes close to the volcanic complex (PCCVC), while a higher proportion of silt-clay with a higher %OM was found in sediments from lakes furthest from the PCCVC, consistent with the expected gradient of volcanic ash size deposited in the lakes. The presence of volcanic ashes in sediments seems to dilute trace element concentrations of samples, having sediment samples from lakes near the PCCVC lower concentrations of Br, Cr, and Ni than the furthest lakes. Environmental quality indices indicated minimal to moderate enrichment/contamination in sediments from deep lakes near the PCCVC and significant to high enrichment/contamination in sediments from lakes far from the volcano and in the shallower lakes. The concentrations of As, Cr, and Ni in six of the 11 sampled lakes are at levels considered harmful for sediment-dwelling organisms according to north hemisphere guidelines. Conclusions Despite being in a protected area, the sediments of some Patagonian lakes have concentrations of potentially toxic elements at levels that may cause pollution and be of risk to the aquatic biota, with the volcanic ashes acting to dilute this effect.
Environmental Science and Pollution Research, 2023
This study analyzes the distribution of nine potentially toxic trace elements (arsenic, antimony,... more This study analyzes the distribution of nine potentially toxic trace elements (arsenic, antimony, bromine, cobalt, chromium, mercury, rubidium, selenium, and zinc) in sediments and plankton from two small mesotrophic lakes in a non-industrialized area impacted by the Caviahue-Copahue volcanic complex (CCVC). The two lakes have different plankton community structures and received different amounts of pyroclastic material after the last CCVC eruption. Trace element concentrations of surface sediments differed between lakes, according to the composition of the volcanic ashes deposited in the lakes. The size of organisms was the principal factor influencing the accumulation of most trace elements in plankton within each lake, being trace element concentrations generally higher in the microplankton than in the mesozooplankton. The planktonic biomass in the shallower lake was dominated by small algae and copepods, while mixotrophic ciliates and different-sized cladocerans dominated the deeper lake. These differences in the community structure and species composition influenced the trace element bioaccumulation, especially in microplankton, while habitat use and feeding strategies seem more relevant in mesozooplankton bioaccumulation. This work contributes to the scarce records of trace elements and their dynamics in plankton from freshwater ecosystems impacted by volcanic activity.
Environmental science and pollution research international, 2018
Zinc (Zn) bioaccumulation and trophic transfer were analyzed in the food web of Lake Nahuel Huapi... more Zinc (Zn) bioaccumulation and trophic transfer were analyzed in the food web of Lake Nahuel Huapi, a deep, unpolluted ultraoligotrophic system in North Patagonia. Benthic macroinvertebrates, plankton, and native and introduced fish were collected at three sites. The effect of pyroclastic inputs on Zn levels in lacustrine food webs was assessed by studying the impact of the eruption of Puyehue-Cordón Caulle volcanic complex (PCCVC) in 2011, by performing three sampling campaigns immediately before and after the PCCVC eruption, and after 2 years of recovery of the ecosystem. Zinc trophodynamics in L. Nahuel Huapi food web was assessed using nitrogen stable isotopes (δN). There was no significant increase of Zn concentrations ([Zn]) in L. Nahuel Huapi biota after the PCCVC eruption, despite the evidence of [Zn] increase in lake water that could be associated with volcanic ash leaching. The organisms studied exhibited [Zn] above the threshold level considered for dietary deficiency, reg...
Analytical Chemistry, 2022
Atmospheric mercury measurements carried out in the recent decades have been a subject of bias la... more Atmospheric mercury measurements carried out in the recent decades have been a subject of bias largely due to insufficient consideration of metrological traceability and associated measurement uncertainty, which are ultimately needed for the demonstration of comparability of the measurement results. This is particularly challenging for gaseous Hg II species, which are reactive and their ambient concentrations are very low, causing difficulties in proper sampling and calibration. Calibration for atmospheric Hg II exists, but barriers to reliable calibration are most evident at ambient Hg II concentration levels. We present a calibration of Hg II species based on nonthermal plasma oxidation of Hg 0 to Hg II. Hg 0 was produced by quantitative reduction of Hg II in aqueous solution by SnCl 2 and aeration. The generated Hg 0 in a stream of He and traces of reaction gas (O 2 , Cl 2 , or Br 2) was then oxidized to different Hg II species by nonthermal plasma. A highly sensitive 197 Hg radiotracer was used to evaluate the oxidation efficiency. Nonthermal plasma oxidation efficiencies with corresponding expanded standard uncertainty values were 100.5 ± 4.7% (k = 2) for 100 pg of HgO, 96.8 ± 7.3% (k = 2) for 250 pg of HgCl 2 , and 77.3 ± 9.4% (k = 2) for 250 pg of HgBr 2. The presence of HgO, HgCl 2 , and HgBr 2 was confirmed by temperature-programmed desorption quadrupole mass spectrometry (TPD-QMS). This work demonstrates the potential for nonthermal plasma oxidation to generate reliable and repeatable amounts of Hg II compounds for routine calibration of ambient air measurement instrumentation.
Chemosphere, Jan 8, 2018
Microbial assemblages are typical of deep ultraoligotrophic Andean Patagonian lakes and comprise ... more Microbial assemblages are typical of deep ultraoligotrophic Andean Patagonian lakes and comprise picoplankton and protists (phytoflagellates and mixotrophic ciliates), having a central role in the C cycle, primary production and in the incorporation of dissolved inorganic mercury (Hg) into lake food webs. In this study we evaluated the mechanisms of Hgincorporation in hetero- and autotrophic bacteria, in the autotrophic dinoflagellate (Gymnodinium paradoxum) and in two mixotrophic ciliates (Stentor araucanus and Ophrydium naumanni) dominating the planktonic microbial assemblage. The radioisotopeHg was used to trace the Hgincorporation in microbiota. Hg uptake was analyzed as a function of cell abundance (BCF: bioconcentration factor), cell surface (SCF: surface concentration factor) and cell volume (VCF: volume concentration factor). Overall, the results obtained showed that these organisms incorporate substantial amounts of dissolved Hgpassively (adsorption) and actively (bacteria ...
The Science of the total environment, Jan 8, 2017
Niche segregation between introduced and native fish in Lake Nahuel Huapi, a deep oligotrophic la... more Niche segregation between introduced and native fish in Lake Nahuel Huapi, a deep oligotrophic lake in Northwest Patagonia (Argentina), occurs through the consumption of different prey. Therefore, in this work we analyzed total mercury [THg] and methylmercury [MeHg] concentrations in top predator fish and in their main prey to test whether their feeding habits influence [Hg]. Results indicate that [THg] and [MeHg] varied by foraging habitat and they increased with greater percentage of benthic diet and decreased with pelagic diet in Lake Nahuel Huapi. This is consistent with the fact that the native creole perch, a mostly benthivorous feeder, which shares the highest trophic level of the food web with introduced salmonids, had higher [THg] and [MeHg] than the more pelagic feeder rainbow trout and bentho-pelagic feeder brown trout. This differential THg and MeHg bioaccumulation observed in native and introduced fish provides evidence to the hypothesis that there are two main Hg trans...
Environmental pollution (Barking, Essex : 1987), 2017
At the beginning of the 21st century, digital imaging technology replaced the traditional silver-... more At the beginning of the 21st century, digital imaging technology replaced the traditional silver-halide film photography which had implications in Ag contamination. Lake Nahuel Huapi is a popular Patagonia tourist destination impacted by municipal silver (Ag) contamination from photographic processing facilities since 1990's. Silver concentrations in a dated sediment core from the lake bottom showed a 10-fold increase above background levels in the second half of the 20th century, then a decrease. This trend corresponds well with published annual global photography industry demand for Ag, which clearly shows the evolution and replacement of the traditional silver-halide film photography by digital imaging technology. There were significant decreases in Ag concentrations in sediments, mussels and fish across the lake between 1998 and 2011. Lower trophic organisms had variable whole-body Ag concentrations, from 0.2-2.6 μg g(-1) dry weight (DW) in plankton to 0.02-3.1 μg g(-1) DW i...
Chemosphere, 2017
h i g h l i g h t s g r a p h i c a l a b s t r a c t Total Hg and Se did not biomagnify in Lake ... more h i g h l i g h t s g r a p h i c a l a b s t r a c t Total Hg and Se did not biomagnify in Lake Nahuel Huapi food web. Mercury bioaccumulation in top predator fish was habitat-dependent. Native and introduced fish had different Hg and Se bioaccumulation patterns. Se:Hg molar ratios were >1 in all organisms.
Marine Pollution Bulletin, 2016
The Commerson&amp... more The Commerson's dolphin is the most common endemic odontocete of subantarctic waters of Tierra del Fuego, Argentina incidentally caught in fishing nets. The species is classified as "Data Deficient" by the IUCN. Metallothioneins (MTs) are considered as suitable biomarkers for health and environmental monitoring. The aims of the study were to assess MT concentrations in the liver and kidney of bycaught specimens. Moreover, correlations with Zn, Se, Cd, Ag and Hg, and the molar ratios of MT:metals were estimated to evaluate if there is an indication of their respective protective role against metal toxicity in tissues. Hepatic and renal MT concentrations were similar, ranging from 11.6 to 29.1nmol·g(-1) WW, and Kidney/Liver ratios ranging from 0.73 to 1.93 corresponded to normal ranges. Results suggest that MTs are related to physiological ranges for the species. This information constitutes the first MT report on Commerson's dolphins and possibly considered as baseline for species' conservation.
The Science of the total environment, Jan 29, 2016
Mercury is released to the environment from natural and anthropogenic sources, and through atmosp... more Mercury is released to the environment from natural and anthropogenic sources, and through atmospheric transport is distributed globally. Lake Futalaufquen (42.8°S) is an oligotrophic lake located in Los Alerces National Park (Northern Patagonia), providing a remote and unpolluted study system. A lacustrine sedimentary sequence revealed 1600years of Hg deposition, identifying natural baselines and marked peaks not correlated with long-range atmospheric transport. Organic matter and catchment erosion were discarded as Hg drivers. Natural background, pre-1300CE Hg concentrations, ranged between 27 and 47ngg(-1) (accumulation rates from 8 to 15μgm(-2)y(-1)). From 1300CE on, the Hg background profile did not follow the generally increasing Hg pattern observed in both Southern and Northern Hemisphere since pre-industrial times. It was not until the last century that a 1.6-fold increase is observed in the Hg accumulation rate, considered among the lowest increments in southern South Ameri...
Chemosphere, 2016
h i g h l i g h t s g r a p h i c a l a b s t r a c t • We report volcanic origin As in the food ... more h i g h l i g h t s g r a p h i c a l a b s t r a c t • We report volcanic origin As in the food web of Lake Nahuel Huapi. • Highest As concentrations were found in phytoplankton and mollusks. • As biodiluted in piscivorous fish food chains and biomagnified in the benthivorous. • As increased after the PCCVC eruption in zooplankton and planktivorous fish. • Habitat alteration by ash deposition might impact As accumulation in benthic biota.
Journal of Radioanalytical and Nuclear Chemistry, 2000
We investigated the use of threshold reactions on magnesium, aluminum, silicon and phosphorus to ... more We investigated the use of threshold reactions on magnesium, aluminum, silicon and phosphorus to determine elemental concentrations and also to correct analytical interferences, using the parametric method. The reactor neutron spectrum averaged cross sections of the threshold reactions on these elements were referred to the (111±3) mb value for the 58Ni(n,p)58g+mCo reaction cross section. The results of the cross section
Radiochimica Acta, 2005
Nuclear reactor / Fission spectrum / Threshold reaction / Cross section / Resonance integral Summ... more Nuclear reactor / Fission spectrum / Threshold reaction / Cross section / Resonance integral Summary. Cross sections, averaged over a 235 U fission neutron spectrum, of some threshold reactions induced on zinc after short irradiations, have been measured. The studied reactions and the corresponding values are: 64 Zn(n, p) 64 Cu, (37.4 ± 1.4) mb; 64 Zn(n, 2n) 63 Zn, (23.4 ± 2.0) µb; 66 Zn(n, p) 66 Cu, (0.775 ± 0.079) mb; 68 Zn(n, p) 68m Cu, (5.32 ± 0.65) µb; and 68 Zn(n, α) 65 Ni, (52.1 ± 2.3) µb, all referred to the cross section of the 27 Al(n, p) 27 Mg standard reaction, (3.84 ± 0.18) mb. Working values for the resonance integrals of the reactions 70 Zn(n, γ ) 71 Zn and 70 Zn(n, γ ) 71m Zn, referred to the tabulated value for the resonance integral of the 68 Zn(n, γ ) 69m Zn reaction, (0.24 ± 0.03) b, were also obtained. The results were (0.1350 ± 0.0093) b and (0.157 ± 0.029) b, respectively.
Journal of Radioanalytical and Nuclear Chemistry, 2005
Summary Heavy metal profiles of short sediment cores sampled from lakes located in Nahuel Huapi ... more Summary Heavy metal profiles of short sediment cores sampled from lakes located in Nahuel Huapi National Park, Northern Patagonia, Argentina, were determined by INAA. Core dating was performed by measuring natural 210Pb and anthropogenic 137Cs, and by identification of tephra layers. No evidence was found for the input increase of the trace elements Sb, Ba, Cs, Zn, Co, Hf, Ni, Se,
Journal of Physics: Condensed Matter, 1999
We report magnetization and electron paramagnetic resonance (EPR) measurements on Co clusters emb... more We report magnetization and electron paramagnetic resonance (EPR) measurements on Co clusters embedded in Ag obtained by an inverse micellar technique. The cluster size (∼10 atoms), the saturation magnetization (M s ), and the anisotropy constant were obtained from magnetization measurements at low temperature. In the as-prepared sample we found that M s /M bulk s = 0.44±0.05. Reduction of the sample under a H 2 flux at 373 K leads to an enhancement of the ratio M s /M bulk s to 1.16 ± 0.19-consistent with Co-cluster-beam experiments-and to an anisotropy constant of K = (8.5 ± 6.5) × 10 7 erg cm -3 , much larger than the corresponding bulk value. The EPR clearly shows the effect of dynamic narrowing due to superparamagnetic relaxation. Modelling the EPR spectra, we obtained independently the anisotropy energy value and the volume dispersion.
Analytical and Bioanalytical Chemistry, 2007
Hg 2+ spike was obtained in seawater in a 25 h incubation experiment with mercury additions of 12... more Hg 2+ spike was obtained in seawater in a 25 h incubation experiment with mercury additions of 12 ng L −1 .
Environmental Science and Pollution Research, 2016
Vegetation associated with lacustrine systems in Northern Patagonia was studied for heavy metal a... more Vegetation associated with lacustrine systems in Northern Patagonia was studied for heavy metal and trace element contents, regarding their elemental contribution to these aquatic ecosystems. The research focused on native species and exotic vascular plant Salix spp. potential for absorbing heavy metals and trace elements. The native species studied were riparian Amomyrtus luma, Austrocedrus chilensis, Chusquea culeou, Desfontainia fulgens, Escallonia rubra, Gaultheria mucronata, Lomatia hirsuta, Luma apiculata, Maytenus boaria, Myrceugenia exsucca, Nothofagus antarctica, Nothofagus dombeyi, Schinus patagonicus, and Weinmannia trichosperma, and macrophytes Hydrocotyle chamaemorus, Isöetes chubutiana, Galium sp., Myriophyllum quitense, Nitella sp. (algae), Potamogeton linguatus, Ranunculus sp., and Schoenoplectus californicus. Fresh leaves were analyzed as well as leaves decomposing within the aquatic bodies, collected from lakes Futalaufquen and Rivadavia (Los Alerces National Park), and lakes Moreno and Nahuel Huapi (Nahuel Huapi National Park). The elements studied were heavy metals Ag, As, Cd, Hg, and U, major elements Ca, K, and Fe, and trace elements Ba, Br, Co, Cr, Cs, Hf, Na, Rb, Se, Sr, and Zn. Geochemical tracers La and Sm were also determined to evaluate contamination of the biological tissues by geological particulate (sediment, soil, dust) and to implement concentration corrections.
Chemosphere, 2018
The study was carried out to determine Hg and Se concentrations in false killer whales stranded o... more The study was carried out to determine Hg and Se concentrations in false killer whales stranded on the Estrecho de Magallanes, Chile, South America. Tissue samples of five mature specimens were analyzed (two females and three males). Mean Hg concentration in liver 1068 (234) μg gdry weight (DW) (standard deviation in parenthesis) was markedly higher than those in kidney 272 (152) μg gDW, lung 423 (325) μg gDW, spleen 725 (696) μg gDW, muscle 118 (94) μg gDW and testicle 18.0 (2.8) μg gDW. Mean Se concentration in liver, 398 (75) μg gDW, was higher than those in kidney 162 (69) μg gDW, lung 128 (84) μg gDW, spleen 268 (245) μg gDW, muscle 47 (38) μg gDW and testicle 25.4 (2.1) μg gDW. Positive correlations were found between Hg and Se molar concentrations in muscle, lung, spleen and kidney. Molar ratio of Se/Hg in liver, lung and muscle were <1, but those in kidney and testicle were markedly >1 suggesting a Se protection against Hg toxicity. In all the examined specimens Hg val...
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Papers by Sergio Ribeiro Guevara
and economic implications, becoming a global issue in the biosphere as a
consequence of the increasing anthropogenic impact in the last few decades. Because of their toxicity, persistence and bio-accumulative nature, heavy metals are hazardous to both terrestrial and aquatic biota, and thus to humans.
Heavy metal bioaccumulation in tissues and organs of high predator species is one of the most important processes currently taking place in the marine environment regarding pollution. Hazardous heavy metals transfer throughout food webs (trophic transference,
also called biotransference). They are transferred from the abiotic
environment compartments (water, sediments, and soil) to living organisms and are accumulated in the biota resulting in the contamination of food items for organisms in upper trophic levels.