Pesticide transport models commonly assume first-order pesticide degradation kinetics for describing reactive transport in soil. This assumption was assessed in mini-column studies with associated batch degradation tests. Soil mini-columns were irrigated with atrazine in two intermittent steps of about 30 days separated by 161 days application of artificial rain water. Atrazine concentration in the effluent peaked to that of the influent concentration after initial break-through but sharply decreased while influx was sustained, suggesting a degradation lag phase. The same pattern was displayed in the second step but peak height and percentage of atrazine recovered in the effluent were lower. A Monod model with biomass decay was successfully calibrated to this data. The model was successfully evaluated against batch degradation data and mini-column experiments at lower flow rate. The study suggested that first-order degradation models may underestimate risk of pesticide leaching if the pesticide degradation potential needs amplification during degradation.

In this work the risk posed to seawater organisms, predators and humans is assessed, as a consequence of exposure to 12 organic micro-pollutants, namely metronidazole, trimethoprim, erythromycin, simazine, flumequine, carbaryl, atrazine, diuron, terbutryn, irgarol, diphenyl sulphone (DPS) and 2-thiocyanomethylthiobenzothiazole (TCMTB). The risk assessment study is based on a 1-year monitoring study at a Spanish marine fish farm, involving passive sampling techniques. The results showed that the risk threshold for irgarol concerning seawater organisms is exceeded. On the other hand, the risk to predators and especially humans through consumption of fish is very low, due to the low bioconcentration potential of the substances assessed.

The submersed macrophytes Elodea canadensis, Myriophyllum spicatum and Potamogeton lucens were constantly exposed over a five-week period to environmentally relevant concentrations of atrazine, isoproturon, diuron, and their mixture in outdoor mesocosms. Effects were evaluated investigating photosynthetic efficiency (PE) of the three macrophytes and growth of M. spicatum and E. canadensis. Adverse effects on PE were observed on days 2 and 5 after application. M. spicatum was found to be the more sensitive macrophyte. E. canadensis and P. lucens were less sensitive to atrazine, diuron and the mixture and insensitive to isoproturon. PE of M. spicatum was similarly affected by the single herbicides and the mixture demonstrating concentration addition. Growth of E. canadensis and M. spicatum was not reduced indicating that herbicide exposure did not impair plant development. Although PE measurements turned out to be a sensitive method to monitor PSII herbicides, plant growth remains the more relevant ecological endpoint in risk assessment. Short-term effects on photosynthesis did not result in growth reduction of submerse macrophytes exposed to PSII inhibitors.

Considering the importance of the oral route for human exposure to atrazine, we have investigated the possible effect of this herbicide on the human intestinal cells and the integrity of the epithelial barrier, using Caco-2 cells as the intestinal model in vitro. We evaluated possibile cytotoxic and genotoxic effects of atrazine in concentrations ranging from 1 to 250 μM on the Caco-2 cells at different stages of growth after short- and long-term exposure. Results from the tetrazolium blue (MTT) test and the Trypan blue exclusion assay showed that atrazine cytotoxicity was dose- and time-dependent. Obtained data indicated that atrazine at high concentrations (50 and 250 μM) was able to induce effects on Caco-2 proliferation and viability. Moreover, it was found that the long-term exposure to atrazine at the non-cytotoxic dose caused inhibition of the intestinal cell maturation and decreased the transepithelial electrical resistance, the indicator of the epithelial barrier integrity. Studies on the atrazine genotoxicity determined using the single cell microelectrophoresis assay indicated that atrazine did not induce DNA damages in the Caco-2 cells at concentrations of up to 50 μM, whereas enhancement in the DNA damage was observed at 250 μM. Altogether, our results indicate that atrazine at expected human oral exposure concentrations is not able to induce effects on the Caco-2 cell proliferation and viability, but may suppress the intestinal cell differentiation and reduce the cell monolayer integrity. We suggest that chronic exposure on low levels of atrazine may lead to alteration in the expression of the morphological and functional features of the Caco-2 cells related to the transport and barrier function of small intestinal enterocytes. In consequence, this may lead to alterations in the intestinal absorption process.

Background, aim, and scope In response to concerns about chemical substances that can alter the function of endocrine systems and may result in adverse effects on human and ecosystem health, a number of in vitro tests have been developed to identify and assess the endocrine disrupting potential of chemicals and environmental samples. One endpoint that is frequently used in in vitro models for the assessment of chemical effects on the endocrine system is the alteration of aromatase activity (AA). Aromatase is the enzyme responsible for converting androgens to estrogens. Some commonly used aromatase assays, including the human microsomal assay that is a mandatory test in US-EPA's endocrine disruptor screening program (EDSP), detect only direct effects of chemicals on aromatase activity and not indirect effects, including changes in gene expression or transcription factors. This can be a problem for chemical screening initiatives such as the EDSP because chemicals can affect aromatase both indirectly and directly. Here we compare direct, indirect, and combined measurements of AA using the H295R cell line after exposure to seven model chemicals. Furthermore, we compare the predictability of the different types of AA measurements for 17β-estradiol (E2) and testosterone (T) production in vitro. Materials and methods H295R cells were exposed to forskolin, atrazine, letrozole, prochloraz, ketoconazole, aminoglutethimide, and prometon for 48 h. Direct, indirect, and combined effects on aromatase activity were measured using a tritiated water-release assay. Direct effects on aromatase activity were assessed by exposing cells only during the conduct of the tritium-release assay. Indirect effects were measured after exposing cells for 48 h to test chemicals, and then measuring AA without further chemical addition. Combined AA was measured by exposing cells prior and during the conduction of the tritium-release assay. Estradiol and testosterone were measured by ELISA. Results and discussion Exposure to the aromatase inhibitors letrozole, prochloraz, ketoconazole, and aminoglutethimide resulted in greater indirect aromatase activity after a 48-h exposure due to presumed compensatory mechanisms involved in aromatase activity regulation. Forskolin and atrazine caused similar changes in hormone production and enzyme profiles, and both chemicals resulted in a dose-dependent increase in E2, T, and indirect AA. Neither of these two chemicals directly affected AA. For most of the chemicals, direct and combined AA and E2 were good predictors of the mechanism of action of the chemical, with regard to AA. Indirect aromatase activity was a less precise predictor of effects at the hormone level because of presumed feedback loops that made it difficult to predict the chemicals' true effects, mostly seen with the aromatase inhibitors. Further, it was found that direct and indirect AA measurements were not reliable predictors of effects on E2 for general inducers and inhibitors, respectively. Conclusions Differential modulation of AA and hormone production was observed in H295R cells after exposure to seven model chemicals, illustrating the importance of measuring multiple endpoints when describing mechanisms of action in vitro. Recommendations and perspectives For future work with the H295R, it is recommended that a combination of direct and indirect aromatase measurements is used because it was best in predicting the effects of a chemical on E2 production and its mechanism of action. Further, it was shown that direct AA measurements, which are a common way to measure AA, must be used with caution in vitro.

Background, aim, and scope Freshwater reservoirs can be impacted by several hazardous substances through inputs from agricultural activity, sewage discharges, and groundwater leaching and runoff. The water quality assessment is very important for implementation of the monitoring and remediation programs to minimize the risk promoted by hazardous substances in aquatic ecosystems. Evaluation of the degree of contamination of aquatic environments must not take in account only its chemical characterization but it must be complemented with biological assays, which determine potential toxic effects and allows an integrated evaluation of its effects in populations and aquatic ecosystem communities. The application of this type of strategy has clear advantages allowing a general evaluation of the effects from all the water components, including those due to unknown substances and synergic, antagonistic, or additive effects. There are only a few studies that reported ecotoxicological acute end points, for the assessment of surface water quality, and the relationship among toxicity results and the anthropogenic pollution sources and the seasonal period. The aim of this study was to assess the ecotoxicological characterization of the surface water from Alqueva reservoir (South of Portugal) and to evaluate the influence of anthropogenic sources of pollution and their seasonal variation in its toxicity. The construction of Alqueva reservoir was recently finished (2002) and, to our knowledge, an ecotoxicological assessment of its surface water has not been performed. Because of that, no information is available on the possible impact of pollutants on the biota. The surface water toxicity was assessed using acute and chronic bioassays. The results are to be used for developing a monitoring program, including biological methods. Materials and methods Water samples were collected during 2006-2007, at each of the nine sampling sites selected in Alqueva reservoir. These sampling points allow an assessment at the upstream (Sra. Ajuda, Alcarrache, Álamos-Captação), at the middle (Alqueva-Montante, Alqueva-Mourão, Lucefecit), and at the downstream of the water line (Alqueva-Jusante; Ardila-confluência; Moinho das Barcas). The campaigns occurred in February, March, May, July, September, and November of 2006 and February, March, and May of 2007. The rainy season comprised November, February, and March, and the dry season included May, July, and September. A total of 81 samples were collected during the study period. The physical-chemical parameters were analyzed following standard and recommended methods of analysis (APHA et al. 1998). The pesticide analyses were performed using gas chromatography according to DIN EN ISO 6468 (1996). Surface water ecotoxicity was evaluated using the following bioassays: Vibrio fischeri luminescence inhibition, Thamnocephalus platyurus mortality, and Daphnia magna immobilization and reproduction assay. The Spearman rank correlation coefficients were used to evaluate the associations between the water sample physicochemical properties (from each sampling station in each season) and the acute and chronic toxicological effects, with a level of significance p < 0.05. Results In the acute toxicity study, the species that was found to be the most sensitive was T. platyurus. T. platyurus detected a higher number of toxic water samples during the dry season. Concerning the luminescent inhibition of V. fischeri, the results showed that this organism detected a great number of toxic water samples in rainy seasons. The water samples, which promoted higher toxic effects towards this species, were from the north and from the middle of the reservoir. The correlation analysis showed that V. fischeri luminescent inhibition (%) was positively correlated with total phosphorus, chlorpyrifos, iron, and arsenic. T. platyurus mortality (%) was positively correlated with the water pH, 5-day biochemical oxygen demand (BOD₅), chlorides, atrazine, simazine, terbuthylazine, and endosulfan sulfate contents. Although the surface waters did not promote acute toxicity to the crustacean D. magna, in the chronic exposure, a significant decrease in the number of juveniles per female was observed, mainly at the dry period. The number of juveniles per female, in the reproduction test of D. magna, was negatively correlated with pH, temperature, BOD₅, chloride, atrazine, simazine, terbuthylazine, and endosulfan sulfate. The water toxicity of the Alqueva water might be due principally to the intensive agriculture activities surrounding the reservoir and to the municipal wastewater discharges. Discussion The physicochemical parameters and the pesticide concentrations indicated that the water quality was worse in the north part of the reservoir system. These results are characteristic of the majority of reservoirs, once the construction of the dam promoted, by itself, the impounding of water flow and the increase of compound residence time. The toxicity tests corroborate with the chemical characterization. Acute toxicity of Alqueva water may be a result of the effect promoted by chlorpyrifos, endosulfan sulfate, phosphorus, and iron. Chronic toxicity may be a result of the effect of herbicides, arsenic, organic matter, endosulfan sulfate in mixture. Hence, the water toxicity of the Alqueva might be due principally to the intensive agriculture activities surrounding the reservoir and to the municipal wastewater discharges. Conclusions This study has shown that a large number of samples from different sites of the Alqueva reservoir contained potentially toxic contaminants. The sites with impaired water quality were those located at the north of the reservoir and in the surrounding areas of intensive agricultural activity. The results demonstrated that the use of a screening of acute and chronic toxicity tests with organisms from different trophic levels and with distinct sensibilities allowed the detections of several patterns of toxicity from spatial and temporal variability promoted by natural or anthropogenic sources. The chronic responses showed, especially in the dry season, that some of the species belonging to this aquatic ecosystem might be at risk. Recommendations and perspectives The V. fischeri and T. platyurus are two species that should be used in the acute bioassays for the ecotoxicological monitoring programs of this reservoir. It is recommended that other species, such as a productive organism (algae), be included in the next study, once the water reservoir had high levels of herbicides. Ecotoxicological assessment of surface water must integrate initial screening based on acute tests followed always by chronic bioassays. The results implicitly suggest that the implementation of processes of remediation by reducing pollutant input into the reservoir and by the implementation of water treatment processes is important and necessary.