Maria E. Pereira

Mercury distribution in key tissues of fish (Liza aurata) inhabiting a contaminated estuary—implications for human and ecosystem health risk assessment

This study brings a new viewpoint based on multiple-tissue analyses to form the basis for a predictive mode of mercury accumulation dynamics in fish body under field conditions. Total mercury (T-Hg) was determined in key tissues of Liza aurata captured along an estuarine contamination gradient, displaying the following hierarchy: kidney > liver > muscle > brain > gills > blood. Brain was the tissue that better reflected the mercury contamination extent, closely followed by liver and muscle. Organic mercury (O-Hg) measured in muscle and liver represented more than 85% and less than 30% of the T-Hg, respectively. The lowest O-Hg percentage was found in the most contaminated area, for both muscle and liver. Mercury distribution and accumulation patterns showed dependence on the specific tissue. The high mercury levels found in organs involved in vital physiological processes point out the risk to autochthonous fish fauna. Human risk associated to the ingestion of fish living in the surveyed areas cannot be excluded.

Sources of potentially toxic elements and organic pollutants in an urban area subjected to an industrial impact

Urban and industrial development has caused a major impact on environmental soil quality. This work assesses the extent and severity of contamination in a small urban area subjected to an industrial impact and identifies the major anthropogenic inputs. Twenty-six soil samples were collected from agricultural and urban sites, and concentrations of potentially toxic elements (As, Cd, Cu, Cr, Fe, Mn, Ni, Pb and Zn), PAHs and PCBs, were determined. In spite of the low median concentrations observed, some sites represent a potential hazard for human health and ecosystems. Concentrations of contaminants were higher than those found in a nearby city, indicating that the study area is affected by the surrounding industry. The use of multivariate statistical analyses allowed for the identification of the main factors controlling the variability of potentially toxic elements and organic pollutants in the soils. The presence of Cr, Fe, Mn and Ni was associated with geogenic inputs, and Cu, Pb, Zn, As, PAHs and PCBs were associated with anthropogenic inputs. Industry and traffic were the most important anthropogenic sources. Soil characteristics were identified as important factors controlling the spatial variability of elements, both from recognised natural and anthropogenic origin. Differences between land uses were observed, which may be attributed to both management practices and proximity to sources.

Halimione portulacoides (L.) physiological/biochemical characterization for its adaptive responses to environmental mercury exposure

This study investigates largely unexplored physiological/biochemical strategies adopted by salt marsh macrophyte Halimione portulacoides (L.) Aellen for its adaptation/tolerance to environmental mercury (Hg)-exposure in a coastal lagoon prototype. To this end, a battery of damage (hydrogen peroxide, H2O2; thiobarbituric acid reactive substances, TBARS; electrolyte leakage, EL; reactive carbonyls; osmolyte, proline) and defense [ascorbate peroxidase, APX; catalase, CAT; glutathione peroxidase, GPX; glutathione sulfo-transferase, GST; glutathione reductase, GR; reduced and oxidized glutathione (GSH and GSSG, respectively), and GSH/GSSG ratio] biomarkers, and polypeptide patterns were assessed in H. portulacoides roots and leaves at reference (R) and the sites with highest (L1), moderate (L2) and the lowest (L3) Hg-contamination gradients. Corresponding to the Hg-burdens, roots and leaves exhibited a differential modulation of damage- and defense-endpoints and polypeptide-patterns. Roots exhibiting the highest Hg-burden (at L3) failed to maintain a coordination among enzymatic-defense endpoint responses which resulted into increased oxidation of reduced glutathione (GSH) pool, lowest GSH/GSSG (oxidized) ratio and partial H2O2-metabolism. In contrast, the highest Hg-burden exhibiting leaves (at L1) successfully maintained a coordination among enzymatic-defense endpoints responses which resulted into decreased GSH-oxidation, enhanced reduced GSH pool and GSH/GSSG ratio and lower extent of damage. Additionally, increased leaf-carotenoids content with increasing Hg-burden implies its protective function. H. portulacoides leaf-polypeptides did not respond as per its Hg-burden but the roots did. Overall, the physiological/biochemical characterization of below (roots)- and above (leaves)-ground organs (studied in terms of damage and defense endpoints, and polypeptides modulation) revealed the adaptive responses of H. portulacoides to environmental Hg at whole plant level which cumulatively helped this plant to sustain and execute its Hg-remediation potential.

Monomethylmercury behaviour in sediments collected from a mercury-contaminated lagoon

Surface sediments and sediment cores were collected in a mercury (Hg)-contaminated lagoon, namely Largo do Laranjo – Ria de Aveiro, Portugal and analysed in order to establish the monomethylmercury (MeHg) behaviour in this kind of environment. In surface sediments, this compound was only detected in one place (13.2 ng g−1 (dry weight)). In this site, it was determined one of the lowest redox potentials (22 mV), indicative of oxic/anoxic conditions, which favours Hg methylation by enhancing the sulphate-reducing bacteria activity. However, the MeHg percentage obtained was low, namely less than 0.1% of the total Hg. This is probably due to Hg deposition with organic matter and iron oxyhydroxides, decreasing Hg availability to methylation. At the deeper layers, MeHg was also determined, reaching 46.4 ng g−1 (dry weight) and representing less than 0.1% of the total Hg. The higher MeHg percentages were observed near the surface, where Hg seems to be faster methylated as a result of the lower sulphide concencentrations that render bioavailable the inorganic Hg. At depth the low MeHg percentages obtained are due to the formation of HgS and to the adsorption of Hg to iron monosulphides.

Gas chromatography - optical fiber detector for assessment of fatty acids in urban soils.

Fatty acids have been used as biomarkers of the microbial community composition of soils and they are usually separated and quantified by gas-chromatography coupled to a flame ionization detector (GC-FID). The aim of this study was to develop, validate and apply a methodology based on gas chromatography coupled to optical fiber detection (GC-OF) for screening five fatty acids used as indicators of fungal and bacterial communities in urban soils. The performance of the GC-OF methodology (optical fiber detector at 1,550 nm) was evaluated by comparison with the GC-FID methodology and it was found that they were comparable in terms of linear range, detection limit and analytical errors. Besides these similar analytical characteristics, the GC-OF is much cheaper than the GC-FID methodology. Different concentrations were determined for each fatty acid indicator which in turn varied significantly between the soil samples analyzed from Lisbon ornamental gardens. Additionally, the GC-OF showed a great potential as alternative for determination of eleven or more fatty acids in urban soils.

A fluorescence-based optical fiber analyzer for catecholamine determination

An optical fibre (OF) analyzer for measuring catecholamines (dopamine, norepinephrine and epinephrine) in biological samples with induced fluorescence was developed. The analytical set-up included a chromatographic column for catecholamine separation and a fluorescence-based OF detection (FOF-analyzer). The detection limit of the FOF-analyser was found to be less than 0.9 pg mL−1. The proposed methodology showed an adequate analytical performance for the determination of the catecholamines in actual samples of human urine. The analytical performance of the FOF-analyzer for catecholamine determination was investigated against the high performance liquid chromatography-electrochemical detection (HPLC-ED) method. The FOF-analyzer showed lower detection limits and larger linear ranges for determination of dopamine (DA), norepinephrine (NE) and epinephrine (E) in comparison with HPLC-ED and other methodologies such as HPLC-fluorescence. These advantages combined with the compact design, small-scale instrumentation, and effective cost of analysis make this system an interesting alternative to the existing methodologies for the determination of catecholamines in clinical samples.

Protection of growth and photosynthesis of Brassica juncea genotype with dual type sulfur transport system against sulfur deprivation by coordinate changes in the activities of sulfur metabolism enzymes and cysteine and glutathione production

Mustard (Brassica juncea L. Czern and Coss.) cvs. Pusa Jai Kisan (with low-affinity S transporter (LAT) system) and Pusa Bold (with dual, low- and high-affinity transporters (LAT + HAT) system) were supplied with 0 or 1 mM S in hydroponics culture, and the coordinate changes in growth traits (plant dry weight and leaf area), photosynthetic traits (photosynthetic rate, intercellular CO2, Fv/Fm, and chlorophyll content), activities of key enzymes of sulfur metabolism, such as ATP-sulfurylase (ATP-S), serine acetyltransferase (SAT), and glutathione reductase (GR), and the contents of cysteine (Cys) and glutathione (GSH) were studied in 30 days after sowing. The results showed that cv. Pusa Jai Kisan was more sensitive to S deprivation than cv. Pusa Bold. In cv. Pusa Jai Kisan, S deprivation resulted in a stronger decrease of plant growth and photosynthetic traits, Cys and GSH contents, and a notable decline in activity of ATP-S. S deprivation up-regulated GR activity to a greater extent in cv. Pusa Bold. In contrast, despite the activity of SAT, an enzyme involved in the final step of Cys biosynthesis, was increased in cv. Pusa Jai Kisan stronger than in cv. Pusa Bold under S-deprivation, it could not be translated into the increase in Cys and, thus, GSH contents and a consequent improvement in growth and photosynthesis. The study demonstrated that cv. Pusa Bold (with LAT + HAT) can be a promising cultivar for activation of Cys and/or GSH biosyntheses and increased plant tolerance to S-deprivation conditions.