Paola A. Babay

Kinetics and mechanisms of EDTA photocatalytic degradation with TiO2 under different experimental conditions

The photocatalytic degradationof EDTA over TiO2 has been analyzed to establish the influence of oxidants on the reaction rate, the nature of the intermediates and the kinetic regime. Degussa P-25 suspensions containing EDTA at initial pH 3 in different concentrations were irradiated under near UV light. A Langmuirian behavior was observed. O2 at saturation concentrations was found to be crucial for EDTA degradation. The rapid depletion of EDTA was not accompanied by a corresponding TOC decrease, indicating formation of refractory intermediates. An enhancement in TOC reduction could be achieved by keeping pH constant or by hydrogen peroxide addition. Addition of Fe(III) caused a remarkable increase on the initial rate of EDTA consumption and also on TOC decrease. Changes in both parameters clearly increased under the simultaneous addition of Fe(III) and H2O2, until limiting values.

Exposure to waterborne 4-tert-octylphenol induces vitellogenin synthesis and disrupts testis morphology in the South American freshwater fish Cichlasoma dimerus (Teleostei, Perciformes)

Exposure to environmental pollutants may disrupt endocrine functions and cause reproductive effects in human and wildlife populations. Various groups of chemicals have estrogen-like effects, including degradation products of alkylphenol polyethoxylates, such as 4-tert-octylphenol (OP). Laboratory studies have shown that exposure of male fish to xenoestrogens results in induction of circulating vitellogenin (Vtg), inhibition of testicular growth, testis abnormalities and formation of intersex gonads. In this study, the impact of the exposure to waterborne OP on reproductive aspects in the South American cichlid fish Cichlasoma dimerus was evaluated using qualitative changes in the levels of Vtg in plasma and surface mucus and histological alterations in the liver and gonads as endpoints. Adult males and females were exposed to OP via immersion during 60 days in aquaria under semi-static conditions, water changes being made every 84 h. Treatment groups were: control (ethanol 0.005%), OP 30, 150 and 300 microg/L. Using Western and Dot blot analysis, Vtg was detected in plasma and mucus of control and treated females and treated males, while no Vtg was observed in samples from control males. Morphological changes in the hepatocytes due to the accumulation of Vtg were observed in OP-exposed males. Impairment of testicular structure became apparent in males treated with the highest OP concentrations. The most salient pathological change was the alteration of lobular organization with increased testicular fibrosis and progressive disruption of spermatogenesis. No major changes were observed in ovarian architecture. Our results indicate that detection of Vtg in surface mucus may be a sensitive and non-invasive biomarker of the endocrine disrupting effects of environmental estrogens, resulting in a useful method for field monitoring.

Simplified determination of lipophilic metabolites of nonylphenol ethoxylates: method development and application in aqueous samples from Buenos Aires, Argentina

In the present work we have developed an analytical methodology for the determination of nonylphenol (NP) and nonylphenol mono- and di-ethoxylates (NP1EO and NP2EO) in water samples. The applicability of this methodology was proved by means of the analysis of environmentally relevant aqueous samples from Buenos Aires. This constitutes a starting point for a rigorous assessment of the incidence of NPnEO surfactants in Argentina, as only very few, qualitative or semi-quantitative data on the occurrence of these compounds in local systems were available up to this time. Enrichment of the analytes was carried out by solid-phase extraction on a C-18 sorbent, followed by elution with ethyl acetate. Normal-phase high performance liquid chromatography on an amino-silica column and fluorescence detection at excitation-emission wavelengths of 230-300 nm were employed for separation and quantification of the analytes. Confirmation of peak assignment in selected real samples was performed by off-line coupling HPLC with GC-MS analysis. A non-polar GC capillary column was used, and a characteristic peak pattern was obtained for the alkyl chain isomers of each ethoxylated homologue and NP. GC-MS analyses yielded in all cases purity levels higher than 80% for the HPLC collected fractions. The elevated concentrations found for the estrogenic metabolites of NPnEO are in accordance with an unrestricted use of this class of non-ionic surfactants in the country.

Effects of waterborne exposure to 17β-estradiol and 4-tert-octylphenol on early life stages of the South American cichlid fish Cichlasoma dimerus

Estrogenic chemicals are often detected in the aquatic environment and can negatively affect animal development and reproduction. In teleost fishes, the hormonal regulation during a critical period of larval development has a strong influence on gonadal sex differentiation; thus this process may be affected by the exposure to environmental estrogens. In this study, we first assessed the lethal acute toxicity of the natural estrogen 17β-estradiol (E2) and the weaker estrogen mimics 4-tert-octylphenol (OP) and 4-nonylphenol (NP) on larval stages of the South American cichlid fish Cichlasoma dimerus. In a further experiment, we analyzed the effects of chronic waterborne exposure to E2 and OP on gonad development and sex differentiation. Exposure to high concentrations of E2 had a pronounced feminizing effect directing sex differentiation towards ovarian development, while testis development was inhibited at a lower, environmentally relevant concentration. Among OP-exposed fish, 15-38.5% of the males exhibited testicular oocytes (TOs), a commonly reported biomarker of estrogenic exposure. However, since TOs were also recorded in control males and the proportion of males with TOs was not significantly higher in OP treatments, their occurrence could not be attributed to OP exposure. In addition, TOs did not seem to impair male gonad development and functionality since normal spermatogenesis was observed in testes of OP-treated fish. These results indicate that E2 occurring in the South American aquatic environment may affect male reproductive development and pose a risk for wild C. dimerus, especially under prolonged exposure, while the effects of weaker xenoestrogens such as OP would be negligible for gonad development in this species. As illustrated by this study, the natural occurrence of TOs indicates that conclusions concerning the causes of this phenomenon must be drawn with care.

Performance of different extraction media for the ultrasonic-assisted extraction of nonylphenol and nonylphenol mono- and diethoxylates from sediments

A systematic study was undertaken to optimise and compare the performance of different extraction media employing ultrasonic-assisted extraction (USE), for the recovery of nonylphenol (NP) and nonylphenol mono- and diethoxylates (NP1EO and NP2EO, respectively) from different spiked sediments (sand, clay and soil). Dichloromethane (DCM) and ethyl acetate (EtAc) were used alone or with methanol (MeOH). Normal phase high performance liquid chromatography with fluorescence detection (HPLC-FL) was used for separation and quantification. In a first stage, a screening Plackett-Burman experimental design was used as a multivariate strategy to evaluate the effects of three variables (solvent polarity, analytes concentrations and sonication time), at two levels each, on spiked clay. Solvent polarity was found to be the most influential factor, especially on the recovery of NP2EO. In a second stage, based on the screening results, USE time was set at 5 min to evaluate the performances of a 1 : 1 MeOH : DCM and a 1 : 1 MeOH : EtAc mixture on spiked sand, clay and soil. The 1 : 1 MeOH : EtAc mixture led to highly satisfactory recoveries for every analyte, statistically comparable to those yielded by a 1 : 1 MeOH : DCM mixture (NP > 85%, NP1EO and NP2EO > 90%). Due to similar interaction observed between each single sediment and the 1 : 1 MeOH : EtAc extractant, a composite substrate made of sand + soil + clay was spiked in a third stage. Extractant composition was then evaluated in order to find out the minimum volume of MeOH that could be used without loss of efficiency. It was found that 100% EtAc matched our aims (%R > 80 and the lowest use of DCM and MeOH). USE protocol was tested on real sediments. The compounds were quantified by HPLC-FL and the identities were confirmed by gas chromatography-mass spectrometry.

Effects of waterborne exposure to the antidepressant fluoxetine on swimming, shoaling and anxiety behaviours of the mosquitofish Gambusia holbrooki

Chemical pollution from pharmaceuticals is increasingly recognized as a major hazard to the aquatic biota. Among the wide variety of pharmaceuticals, fluoxetine (FLX) is one of the most widely prescribed antidepressants, and therefore, it is frequently identified in the aquatic environment. As FLX is designed to alter human behaviour and many physiological pathways are conserved across vertebrates, this drug may affect the behaviour of fish living in FLX-polluted environments. Here, we exposed groups of female mosquitofish Gambusia holbrooki to waterborne FLX for 14 days, under semi-static conditions with daily renewal of test solutions. Following exposure, we conducted a set of behavioural assays in individual fish, aimed at assessing the effects of FLX on their locomotor activity and behavioural responses. We found that FLX impaired swimming behaviour at high concentrations (25 μg/L and 50 μg/L) but not at low concentrations close to environmental levels (1 μg/L and 5 μg/L). When swimming activity was assessed 5 min after transfer of the focal fish to the testing tank, 50 μg/L FLX was the only concentration showing significant effects. However, when the same trials were performed 24 h later, 25 μg/L FLX turned out to be an effect concentration in addition to 50 μg/L. Interestingly, these concentrations would elicit fish plasma concentrations comprised within the range of human therapeutic doses. When subjected to a light/dark preference test, fish showed tendency to remain less time in the dark area at high FLX concentrations, thus suggesting an anti-anxiety response. Shoaling behaviour was not affected by FLX exposure. Our study contributes to the growing body of literature evaluating the effects of FLX on animal behaviour. Regarding the experimental design used in behavioural testing, our findings suggest that focal fish should be subjected to long habituation periods, namely of at least a few hours, in order to better assess the effects of drug exposure.