Departamento de Química

Approximately 30 groundwater monitoring wells, under a fruit production field, in the Valley of the Neuquen Ž . River Northern Patagonic, Argentina , to which different pesticides have been applied, were sampled eleven times between October 1995 and March 1997. Azinphos methyl was the main pesticide applied and it was detected with the highest frequency in groundwater wells during the period of intensive pesticide application in the Southern Hemisphere. Dimethoate, methidathion, fosmet, cipermethrin, carbaryl, propoxur, carbofuran, benomyl and carbendazim were also detected with lower frequency. The characteristic of the area under study was alkaline soil, with an organic matter content below 2.5% and texture sandy clay loam. The half life of azinphos methyl in soils was 166.2 days in the sun light for horizon A and 194.15 in the dark for horizon B. Leaching of azinphos methyl through the different soil horizons was minimum. On the basis of our lysimeter laboratory data, in which most of the pesticide was adsorbed into the soil column and only small quantities leachate, we inferred that the impact of azinphos methyl on groundwater would be minimal. However, field data indicates that there is a persistence of azinphos methyl in groundwater during the application season. ᮊ

In order to detect spoilage yeast species in wines showing off-odors, different yeast isolation protocols were evaluated. Independently of the isolation method, only Saccharomyces cerevisiae and Pichia manshurica were detected. The spoilage capacity of P. manshurica regional isolates was evaluated in red wine and the production of volatile phenols was evidenced. To evaluate the possible source of contamination, yeasts from both grapes and cellar surfaces were obtained. Hanseniaspora uvarum and Zygoascus hellenicus were detected in both sound and damaged grapes from sunny areas. The most frequent species in cellar surfaces was Candida boidinii, Pichia membranifaciens and P. manshurica were detected in filters. The intra-specific genetic characterization of the P. manshurica isolates by mtDNA-RFLP demonstrated that the same strain was detected in both wine and filter. Most P. membranifaciens isolates produced 4-EP (maximum level of 1.895 mg/L) and particularly high levels of 4-EG (maximum level of 10.260 mg/L) were produced by P. manshurica isolates in synthetic wine-like medium. In this work the capacity of P. manshurica and P. membranifaciens species to produce volatile phenols was shown for the first time.

The organophosphorous compound azinphosmethyl (AzMe) is applied extensively in northern Patagonia (southern Argentina) to manage codling moths (Cydia pomonella). This area is irrigated by fast-flowing channels that provide a favorable habitat for many species, including amphipods (Hyalella curvispina) and a field-mixed population of black flies (Simulium bonaerense, Simulium wolffhuegeli, and Simulium nigristrigatum). In the present study, AzMe susceptibility and carboxylesterase (CarbE) activity from both insecticide-exposed and nonexposed field populations were studied. The median lethal dose determined in codling moths from an insecticide-treated orchard was significantly higher (3.48 g/insect) than that observed in those from an untreated orchard (0.69 g/insect). Similarly, the median lethal concentration (LC50) determined in black flies collected from the treated area (0.021 mg/L) was significantly higher than that recorded in those from the untreated site (0.011 mg/L). For amphipods, both a subpopulation susceptible to AzMe (LC50, 1.83 g/L) and a resistant one (LC50, 390 g/L) were found in the treated area. Both subpopulations were more resistant to AzMe than the population from the untreated site (LC50, 0.43 g/L). Significant differences (p Ͻ 0.001) in CarbE activities were observed between populations from pesticide-treated and untreated areas. Mean activities Ϯ standard deviation from treated and untreated sites were 0.21 Ϯ 0.16 and 0.016 Ϯ 0.008 mol/min/mg protein, respectively, for codling moths; 2.17 Ϯ 1.71 and 0.81 Ϯ 0.35 mol/min/mg protein, respectively, for black flies; and 0.27 Ϯ 0.10 and 0.14 Ϯ 0.07 mol/min/mg protein, respectively, for amphipods. The results suggest that enhanced CarbE activity is one of the mechanisms that provide AzMe resistance in H. curvispina, Simulium spp., and C. pomonella populations from the insecticidetreated areas.

The authors evaluated biomarker responses in caged larvae of the amphibian Rhinella arenarum in water channels during fruit production season and compared them with those elicited by a transient exposure to azinphos methyl (AzM) (0.02-2 mg/L; 4 h), the main pesticide applied in the Alto Valle region, Patagonia, Argentina, taking into account the maximum environmental concentration detected in superficial water (22.5 mg/L). The traditional biomarkers of organophosphate exposure, acetylcholinesterase (AChE) and carboxylesterase, were inhibited in tadpoles after one week of exposure in channels potentially receiving pesticide drift, whereas the antioxidant glutathione (GSH) and the detoxifying activity of GSH S-transferase (GST) were induced. In a two-week monitoring study, AChE activity was induced in larvae exposed at the agricultural site, and carboxylesterase showed an inhibition followed by return to control values, suggesting an exposure-recovery episode. Antioxidant glutathione levels were first depleted and then surpassed control levels, whereas GST activity was continuously induced. These responses were mimicked in the laboratory by 2 mg/L AzM-pulse exposure, which notably exceeds the expected environmental concentrations. The results draw attention to the complexity of responses after pesticide exposure, strongly depending on exposure time-concentration and recovery periods, among other possible factors, and support the necessity of the integrated use of biomarkers to assess exposure episodes in agricultural areas. Environ. Toxicol. Chem.

The objective of this study was to assess the effects of Magnacide H (Baker Petrolite, TX, USA) usage on the aquatic ecosystem at the Cooperativa de Riego y Fomento (CORFO)-Río Colorado irrigation channels, analyzing the effects on benthic invertebrates. At recommended treatment concentrations, Magnacide H kills most of the aquatic organisms; however, its presence in the channels is transient. Magnacide H caused a significant reduction in the number of taxa (58%), abundance (57%), and community diversity (67%) in the benthic assemblage with respect to untreated channels during the application period in the first year of the study. The herbicide reduced the abundance of the most abundant taxa: oligochaetes, chironomids, ostracods, and the snails Biomphalaria peregrina and Heleobia parchappii. In contrast, the herbicide only reduced invertebrate diversity during the application period at the second year of study. Two months after the applications had ceased, the benthic community in treated channels recovered their biotic attributes, reaching values similar to controls. Recovery could have occurred from upstream unimpaired reaches supplying migrating invertebrates that recolonized affected areas. Since recovery occurred within a reasonable period of time, we conclude that the impact of Magnacide H at CORFO-Río Colorado channels is acceptable from a regulatory point of view in the present practice protocol. Nevertheless, a strict control on the application conditions must be ensured to minimize the risk on the ecological receptors. We emphasize the recommendation that water release outside the channels is prevented until the product has dissipated.

Black flies, a non-target species of the insecticides used in fruit production, represent a severe medical and veterinary problem. Large increases in the level of resistance to the pyrethroids fenvalerate (more than 355-fold) and deltamethrin (162-fold) and a small increase in resistance to the organophosphate azinphos methyl (2-fold) were observed between 1996-2008 in black fly larvae under insecticide pressure. Eventually, no change or a slight variation in insecticide resistance was followed by a subsequent increase in resistance. The evolution of pesticide resistance in a field population is a complex and stepwise process that is influenced by several factors, the most significant of which is the insecticide selection pressure, such as the dose and frequency of application. The variation in insecticide susceptibility within a black fly population in the productive area may be related to changes in fruit-pest control. The frequency of individuals with esterase activities higher than the maximum value determined in the susceptible population increased consistently over the sampling period. However, the insecticide resistance was not attributed to glutathione S-transferase activity. In conclusion, esterase activity in black flies from the productive area is one mechanism underlying the high levels of resistance to pyrethroids, which have been recently used infrequently. These enzymes may be reselected by currently used pesticides and enhance the resistance to these insecticides.

Although non-innervated, the placenta contains both cholinesterases (ChEs), butyrylcholinesterase (BChE) and acetylcholinesterase (AChE). These enzymes are well-known for their multiple molecular forms. In a first approach, we used recognized specific inhibitors, substrate preferences and non-denaturating gel electrophoresis in order to characterize the ChE profile of term placenta from uncomplicated pregnancy. Results strongly suggest that the predominant cholinesterasic form present was tetrameric BChE. It is well established that both ChEs are targets of cholinesterase-inhibiting organophosphates (OP), one of the most important classes of chemicals actively applied to the environment. However, we have previously reported increased ChEs activity in placenta of rural residents exposed to OP. In the present work, we have studied: 1) whether this finding was reproducible and, 2) whether AChE or BChE up regulation is behind the increase of placental ChE activity. The population studied included forty healthy women who live in an agricultural area. Samples were collected during both the OP pulverization period (PP) and the recess period (RP). The placental ChEs activity increased in PP, evidencing reproducibility of previous results. The analysis of non-denaturating gels revealed that increased activity of total ChE activity in placenta from women exposed to OP may be attributable to tetrameric BChE up-regulation.

BACKGROUND: In this work, a comprehensive study of the respirometric and physical-chemical methods has been performed to evaluate the information provided by these two methodologies in order to assess the biodegradable organic matter fractions of wastewater. RESULTS: First, an analysis was performed of the influence of the initial substrate on biomass ratio (F 0 /X 0) in the assessment of readily biodegradable organic matter, S S , through respirometric experiments. In order to achieve an adequate assessment of the S S component, similar conditions (given by the initial F 0 /X 0 ratio) must be employed in experiments that are carried to determine S S and Y H (heterotrophic yield). Second, a comparative analysis of respirometric and physical-chemical methods was carried out. The respirometric analysis yielded a lower value of the S S component than the one using the physical-chemical method. Moreover, the respirometric analysis cannot measure the total content of slowly biodegradable organic matter, X S , since this method is only capable of determining the readily hydrolyzed biodegradable substrate. CONCLUSIONS: Considering the results, an adequate characterization method of the S S component has been proposed. This method provides readily and slowly hydrolyzable biodegradable organic matter fractions.

The aim of this study was to assess the effect of several operational variables on both biological and separation process performance in a submerged anaerobic membrane bioreactor pilot plant that treats urban wastewater. The pilot plant is equipped with two industrial hollow-fibre ultrafiltration membrane modules (PURON Ò Koch Membrane Systems, 30 m 2 of filtration surface each). It was operated under mesophilic conditions (at 33°C), 70 days of SRT, and variable HRT ranging from 20 to 6 h. The effects of the influent COD/SO 4-S ratio (ranging from 2 to 12) and the MLTS concentration (ranging from 6 to 22 g L À1) were also analysed. The main performance results were about 87% of COD removal, effluent VFA below 20 mg L À1 and biogas methane concentrations over 55% v/v. Methane yield was strongly affected by the influent COD/SO 4-S ratio. No irreversible fouling problems were detected, even for MLTS concentrations above 22 g L À1 .