906 resultados para Fresh water


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Contaminants of emerging concern (CECs) are continuously being released into the environment mainly because of their incomplete removal in the sewage treatment plants (STPs). The CECs selected for the study include antibiotics (macrolides, sulfonamides and ciprofloxacin), sucralose (an artificial sweetener) and dioctyl sulfosuccinate (DOSS, chemical dispersant used in the Deepwater Horizon oil spill). After being discharged into waterways from STPs, photo degradation is a key factor in dictating the environmental fate of antibiotics and sucralose. Photodegradation efficiency depends on many factors such as pH of the matrix, matrix composition, light source and structure of the molecule. These factors exert either synergistic or antagonistic effects in the environment and thus experiments with isolated factors may not yield the same results as the natural environmental processes. Hence in the current study photodegradation of 13 CECs (antibiotics, sucralose and dicotyl sulfosuccinate) were evaluated using natural water matrices with varying composition (deionized water, fresh water and salt water) as well as radiation of different wavelengths (254 nm, 350 nm and simulated solar radiation) in order to mimic natural processes. As expected the contribution of each factor on the overall rate of photodegradation is contaminant specific, for example under similar conditions, the rate in natural waters compared to pure water was enhanced for antibiotics (2-11 fold), significantly reduced for sucralose (no degradation seen in natural waters) and similar in both media for DOSS. In general, it was observed that the studied compounds degraded faster at 254 nm, while when using a simulated sunlight radiation the rate of photolysis of DOSS increased and the rates for antibiotics decreased in comparison to the 350 nm radiation. The photo stability of the studied CECs followed the order sucralose > DOSS > macrolides > sulfonamides > ciprofloxacin and a positive relationship was observed between photo stability and their ubiquitous presence in natural aquatic matrices. An online LC-MS/MS method was developed and validated for sucralose and further applied to reclaimed waters (n =56) and drinking waters (n = 43) from South Florida. Sucralose was detected in reclaimed waters with concentrations reaching up to 18 µg/L. High frequency of detection (> 80%) in drinking waters indicate contamination of ground waters in South Florida by anthropogenic activity.

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Originally, Carolinians grew rice on dry land, but early in the eighteenth century, cultivation spread to swampy fresh water areas. Until the 1850s, rice reigned supreme. But large-scale rice production was limited to the tidal marshes and inland swamp, while cotton became profitable statewide after the invention of the cotton gin. In its heyday, however, rice made a few hundred planters extremely wealthy. It also contributed to cross culturation and the making of Carolina as a rich cultural hybrid. In this essay, it is this aspect of rice cultivation that Professor Littlefield describes.

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"La seguridad ambiental es un concepto complejo que puede ser analizado desde varios enfoques. La conexión entre degradación ambiental, escasez de recursos, poco desarrollo económico e inestabilidad política puede generar rápidamente conflictos llamados ambientales, terrorismo ecológico y guerras verdes. Sin embargo, en la mayoría de las investigaciones sobre degradación ambiental y conflictos armados no se tienen en cuenta los factores desarrollo económico y régimen político, pues se considera que los problemas ambientales pueden, por sí solos, conducir a situaciones conflictivas nacionales, regionales e internacionales. En este contexto, los propósitos de este artículo son plantear las diferentes tendencias ideológicas de la seguridad ambiental, definir el contenido y las causas de los conflictos ambientales y proponer un marco analítico complementario que incluya las variables políticas y económicas como generadoras de conflictos ambientales y de conflictos armados de alta intensidad. Al final, se propone una agenda de investigación en materia de seguridad ambiental para Colombia."

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Introducción: La construcción de megaproyectos hídricos implica una reconfiguración territorial donde se ven afectadas las fuentes de agua dulce, la biodiversidad terrestre y acuática, y los asentamientos humanos que colindan con dichas construcciones. Objetivo: estimar la asociación entre las conductas proambientales con la solastalgia entre las personas que se encuentran ejerciendo un proceso de resistencia social contra la Central Hidrosogamoso en el departamento de Santander, Colombia. Metodología: se utilizó un diseño de estudio transversal en el que se entrevistaron integrantes y no integrantes de grupos ambientalistas de las zonas de influencia del proyecto. Se realizó un análisis descriptivo de las variables sociodemográficas de los dos grupos de comparación presentando frecuencias absolutas y relativas y diferencias significativas por medio de la prueba ji cuadrado, exacta de Fisher y U de Mann Whitney. Se utilizó un modelo de regresión lineal múltiple en el que la variable dependiente fue el puntaje de solastalgia y las variables independientes fueron las escalas de las conductas proambientales: altruismo, austeridad, equidad, conducta ecológica, deliberación, indignación y aprecio por lo natural, además, se ajustó por algunas variables sociodemográficas de interés. Resultados: los grupos comparados presentaron diferencias importantes en cuanto a la zona de procedencia, condiciones económicas y organización social. El incremento de 5 puntos en la escala del sentimiento de indignación incrementó 0.98 la escala de solastalgia (IC95%: 0.19; 1.78). Las personas sin pareja estable tuvieron 3.02 puntos menos de solastalgia comparadas con personas casadas o en unión libre (IC95%: -4.96; -1.44), mientras que aquellas con alto nivel educativo obtuvieron 2.02 puntos menos que las personas con primaria y bachillerato (IC95%: -3.99; -0.06). Un modelo alterno mostró que no pertenecer a un grupo ambientalista disminuye en 2.29 puntos la solastalgia, comparado con pertenecer a un grupo (IC95%: -4.31; -0.28),. Conclusión: posiblemente las motivaciones por las cuales los actores involucrados se resisten a las transformaciones territoriales ocasionadas por la construcción de las represas son más un reflejo de la condición socioeconómica que de la preocupación de los actores por el daño del medio ambiente y además, esta resistencia es un fenómeno que se limita a aquellos que están afectados directamente en el área de influencia del proyecto

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The study of groundwater dependent ecosystems opened the opportunity to involve specialists of different areas of knowledge in order to obtain answers for complex interrelations between groundwater and the associated ecosystems. The actual study, carried out in two coastal lagoons of the Portuguese SW coast, showed the high dependency of the marine life and vegetation of the lagoons and associated streams discharging in the lagoons on the fresh water supply of these two lagoons and the high contribution they receive from groundwater in the dry period, which corresponds to more than half of each hydrologic year. Every year, the lagoons are artificially opened to the ocean for a few days to a few weeks, which dramatically changes the inside salinity. The sensitivity of these ecological niches is demonstrated by the strong dependence that some species that are more sensitive to high salinity waters show in relation to the entrance of freshwater resultant from the discharge of the phreatic aquifer of Sines sedimentary Basin. The great biodiversity of these lagoons and its precarious balance is only possible to preserve if the aquifer continue to act as a regulatory factor of the lagoon’s salinity. The equilibrium can be changed in the event of overexploitation of the phreatic aquifer, which is not at risk in the near future. In a scenario of climate change the lagoons will benefit from a slow increase in groundwater contribution, due to the rise of sea level, which will be accompanied by a rise in groundwater levels in the aquifer near the sea.

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Stephen Setter, Melissa Setter, Michael Graham and Joe Vitelli recently published their paper 'Buoyancy and germination of pond apple (Annona glabra L.) propagules in fresh and salt water' in Proceedings of the 16th Australian Weeds Conference. Stephen also presented this paper at the conference. Pond apple is an aggressive woody weed which has invaded many wetlands, drainage lines and riparian systems across the Wet Tropics bioregion of Far North Queensland. Most fruit and seed produced by pond apple during the summer wet season fall directly into creeks, river banks, flood plains and swamps from where they are dispersed. They reported that pond apple seeds can float for up to 12 months in either fresh or salt water, with approximately 38% of these seeds germinating in a soil medium once removed from the experimental water tanks at South Johnstone. Their study suggested that the removal of reproductive trees from areas adjacent to creeks and rivers will have an immediate impact on potential spread of pond apple by limiting seed input into flowing water bodies.

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In the author’s opinion, extremely little is known of fresh and brackish water species, i.e. those supporting the traditional artisanal fisheries and most likely to include suitable candidates for aquaculture. The immediate purpose of this paper is to document the species which are encountered in artisanal fisheries, give available background information on them relevant to fisheries and aquaculture work, and to provide a means for their identification in the field by nonspecialists. Scope of Coverage the "Niger Delta" in the title reflects the geographical area of the author’s personal experience. For purposes of identification, the scope of the paper is West African for brackish species, and Nigerian for freshwater species