Structural elucidation of phototransformation products of azimsulfuron in water

The photodegradation of the sulfonylurea herbicide azimsulfuron, N-[[(4,6-dimethoxypyrimidin-2-yl)amino]carbonyl]-1-methyl-4-(2-methyl-2H-tetrazole-5-yl)-1H-pyrazole-5-sulfonamide (AZS), was studied in water at different wavelengths and in the presence of photocatalysts. AZS was rapidly degraded by UV light, affording three photoproducts. The main product, accounting for about 70% of photodegraded herbicide, was identified as 6-amino-5-[(4,6-dimethoxypyrimidin-2-yl)methylamino]-1,5,6,8-tetrahydro-7-oxa-8lambda(6)-tia-1,2,5,6-tetraza-azulen-4-one (ADTA) by single-crystal X-ray diffraction. With simulated sunlight irradiation, the reaction was slower and 2-amino-4,6-dimethoxypyrimidine (DPA) and 1-methyl-4-(2-methyl-2H-tetrazole-5-yl)-1H-pyrazole-5-sulfonamide (MPS), arising from a photohydrolytic cleavage of the sulfonylurea bridge, were the only byproducts observed. The reactions followed first-order kinetics. The addition of dissolved organic matter (DOM) did not modify significantly the AZS photodegradation rate. The presence of Fe2O3 accelerated more than twice the reaction rate affording two major products, DPA and MPS, together with minor amounts of N-[[(5-hydroxy-4,6-dimethoxypyrimidin-2-yl)amino]carbonyl]-1-methyl-4-(2-methyl-2H-tetrazole-5-yl)-1H-pyrazole-5-sulfonamide (AZS-OH). The greatest degradation rate was detected in the presence of TiO2. Only the photohydroxylation product AZS-OH was observed, which was transformed rapidly into oxalic acid.     

Descriptive and spatial epidemiology of bovine cysticercosis in North-Eastern Spain (Catalonia)

From March 2005 to December 2007, 284 animals from 67 cattle farms (24 dairy and 43 beef) affected by bovine cysticercosis were detected in the region of Catalonia (North-Eastern Spain). Dairy farms were almost twice more likely to be affected than beef farms (OR = 1.79, 95% CI = 1.08–2.96, p < 0.05), and infected premises have a statistically significant (p < 0.05) larger number of animals when compared to uninfected farms in Catalonia.     

DNA barcoding for conservation and management of Amazonian commercial fish

DNA barcoding is used to assign a biological specimen to a species. DNA-based procedure has become the preferred forensic tool for criminal prosecution in cases involving the sale of incorrectly identified food. The aim of this work was to develop a DNA-based marker for allowing an accurate and reliable identification of Amazonian fish species of commercial interest. For this purpose, we extracted DNA from fish directly purchased in local markets and identified de visu by local experts. We PCR amplified the mitochondrial 12S rRNA and cytochrome oxidase I (COI) genes. Twenty-nine commercial species accounting for most commercial landings in the River Amazon markets were unambiguously identified based on their DNA for the first time. Phylogenetic trees reconstructed based on the sequences of the two mitochondrial genes clustered species in concordance with their taxonomic classification. We illustrated the utility of DNA barcoding demonstrating that the group of fish generically sold as “Acará” includes seven different species, which are being exploited together as a single species, thus estimation of exploitation rates was not possible until now. Application of genetic markers for species authentication in markets and control of commercial landings will contribute to recognition of the real fishing targets and to the conservation of fish resources in the Amazon basin.     

An Integration of Water Physicochemistry,Algal Bioassays,Phytoplankton, and Zooplankton for Ecotoxicological Assessment in a Highly Polluted Lowland River

Results of different approaches potentially useful for the evaluation of water ambient quality were analysed and compared in a small temperate lowland river with mixed diffuse and multiple-point source pollution. The Reconquista River (Buenos Aires Province, Argentina), one of the most polluted watercourses of Latin America, receives agrochemicals as well as domestic and industrial (mostly untreated) effluents. Physical and chemical water variables were determined; unispecies algal bioassays (with Chlorella pyrenoidosa and Scenedesmus acutus) were carried out in laboratory; and density and structure of phyto- and zooplankton were analysed at three sites in four dates (representing a range of likely conditions in the river). A general scheme of association among plankton, bioassays and physical/chemical variables was elaborated, that helped to infer possible control factors in this multi-stressed system. Some empirical methods, but mainly mathematical ones including multivariate techniques (as PCA, cluster analysis), were applied for evaluation of samples. A preliminary selection of indices and attributes as potential indicators of the water river quality was made, and then applied for assay a tentative integrative ordination of samples. The relative best water quality was recorded when-where dissolved oxygen concentration, algal diversity and planktonic crustacean density were higher. The worst water quality corresponded to the lack of cladocerans and lowest crustacean density, and higher: organic and industrial pollution, major nutrients (ammonium and orthophosphates), BOD, hardness, conductivity, algal biomass in bioassays, phytoplankton density (>10 000 ind. mL^-1), dominance of a single algal species (>90%), and rotifer proportion in zooplankton (>85%).     

Wet deposition of current use pesticides at a rural location on the Delmarva Peninsula: impact of rainfall patterns and agricultural activity

Event-based precipitation samples were collected during the main agricultural season (April-September) over 4 years (2000-2003) at one site in the Choptank River Watershed on the Delmarva Peninsula. The samples were analyzed for 19 agricultural pesticides to determine the contribution of wet deposition as a source of these compounds to the Chesapeake Bay and the factors affecting the temporal trends in deposition. Chlorothalonil was detected most frequently (92% samples) followed by metolachlor (66%) and endosulfans (49%). Although chlorothalonil is the single biggest contributor to pesticide flux (33-46%), pesticide wet deposition is dominated by herbicides (46-61%), with the greatest fluxes occurring during the time of herbicide application on corn and soybeans. The analysis suggests that the extent of wet deposition of herbicides depends on the timing of precipitation relative to herbicide application. The insecticide and fungicide flux was greater in years with above-average rainfall (2001 and 2003), suggesting that for these pesticides deposition flux is dependent on the total amount of rainfall in the agricultural season. The data indicate that the use of chlorpyrifos, an organophosphate insecticide which is on the Toxics of Concern list for the Bay, is on the increase. Total pesticide flux ranged from 90 microg/m2 (2001) to 180 microg/m2 (2000). Wet deposition can account for up to 10-20% of the annual loadings of pesticides to the Bay.     

Assessment of tillage erosion by mouldboard plough in Tuscany (Italy)

This study was designed to characterise the soil translocation effect induced by mouldboard ploughing with an implement traditionally used in the Tuscany region (Central Italy). We discuss the results of a set of field experiments performed to measure soil displacement along slopes of varying gradient in different directions and at several depths of tillage. Using the Soil Erosion by Tillage (SETi) model, soil translocation patterns for different tillage scenarios were analysed, with special attention paid to the effects of the direction and depth of tillage on the extent and spatial pattern of soil movement. The lateral slope gradient S_P and tillage depth D were found to be the dominant controlling factors for total soil displacement. The effect of the slope gradient in a direction parallel to tillage S_T was much less pronounced. These findings reveal the importance of the asymmetric nature of the soil movement produced by mouldboard ploughing and the predominant effect of the lateral displacement d_P on the actual trajectory of soil motion. Results demonstrate that spatial patterns of soil redistribution due to mouldboard ploughing are highly variable and depend on the particular characteristics of the implement used. This dependence is so strong that maximum downslope soil translocation can occur during both, contour tillage or up–down tillage. For this particular mouldboard plough, maximum downslope soil transport took place at a tillage direction ca. 70° and not when tillage was conducted along the steepest slope direction (0°). These findings highlight the potential of the combined approach applied. The physically based SETi model can be properly calibrated using a relatively limited dataset from field experiments. Once calibrating, the SETi model can then be used to generate synthetic tillage translocation relationships, which can predict the intensity and spatial pattern of soil translocation over a much wider range of tillage scenarios than the particular experimental conditions, in terms of topography complexity (slope gradients and morphology) and the direction and depth of tillage. These synthetic relationships are useful tools for evaluating strategies designed to reduce tillage erosion.     

The ecological basis of the indigenous Nahua agriculture in the sixteenth century

The study of agriculture in ancient societies is of vital importance for the understanding of their ecological basis. This article discusses data gathered from Alonso de Molina's dictionary, published in Mexico City in 1571. Molina's information on soil, rain, plants, technology, and human labor applied to agricultural activities gives a picture of the complexity of the several native agricultural systems practiced at that time. Since the Sixteenth Century, native agriculture was impacted by the introduction of new plants, animals, agricultural equipment, and techniques from the Old World. A combination of the two agricultural models conform a new Mexican model of agriculture along the Colonial times. The knowledge of Sixteenth Century agricultural systems is fundamental for the understanding of the history and the conformation of contemporary agro-ecosystems. Recent studies on ecology and social anthropology agree on the necessity to take into account historical data for the discussion of ecological sustainability.     

Silver-catalyzed C-C bond formation between methane and ethyl diazoacetate in supercritical CO₂

Even in the context of hydrocarbons' general resistance to selective functionalization, methane's volatility and strong bonds pose a particular challenge. We report here that silver complexes bearing perfluorinated indazolylborate ligands catalyze the reaction of methane (CH(4)) with ethyl diazoacetate (N(2)CHCO(2)Et) to yield ethyl propionate (CH(3)CH(2)CO(2)Et). The use of supercritical carbon dioxide (scCO(2)) as the solvent is key to the reaction's success. Although the catalyst is only sparingly soluble in CH(4)/CO(2) mixtures, optimized conditions presently result in a 19% yield of ethyl propionate (based on starting quantity of the diazoester) at 40°C over 14 hours.