Estimating the Self-depuration Capacity of a Reach of the Luján River

A 3-km reach of the Luján River was studied by establishing 6 sampling stations, which were from 300 to 500 m apart. The first station was the control reading for river nutrients and particulate material. The second station measured the continuous effluent from a wastewater treatment plant flow of the city of Luján and was, therefore, considered a continuous addition point of nutrients. The other 4 stations were used to evaluate whether the river captured phosphorus as phosphate, nitrogen as ammonium, nitrite or nitrates, and the suspended particulate material, both organic and inorganic. These data were used to calculate material uptake (U), uptake velocity (Vf), and net distance Snet under two different hydrological situations, during low and high flow, during the same season of the same year. Results indicate that phosphate ions as well as organic matter are retained for less than 2 km in both high and low flow situations. In the case of ammonium, the results appear similar to those of phosphate ions but it may be transformed into nitrates and transported in the latter form for greater distances. It is concluded that this river, in the reach under study, has a variable retention speed according to its flow but the retention capacity is no less than 900 m and as much as 2000 m. Therefore, a 2 km distance must be considered as the minimum distance before another effluent of nutrients or organic matter is added.Fil: Piccinini, Mauricio. Provincia de Buenos Aires. Municipalidad de Lujan; ArgentinaFil: Sánchez Caro, Anibal. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Gultermiriam, M.L.. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Giorgi, Adonis David Nazareno. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Efecto del ganado sobre la estructura de la vegetación en las riberas de un arroyo pampeano

El ganado es una de las principales perturbaciones para las zonas ribereñas de los arroyos en la provincia de Buenos Aires. Nuestro objetivo es comparar las características de la vegetación y el suelo de dos tramos casi contiguos del arroyo Nutrias, un afluente del río Reconquista. Un sector se cerró al ganado durante dos años, y el otro (500 m aguas abajo) ha mantenido el ganado durante todo el período. Para cada margen del arroyo, se muestrearon seis transectas de 10 m para la cobertura de especies y se tomaron tres muestras de suelo para la determinación de materia orgánica, fósforo, pH, conductividad y densidad aparente. La altura del dosel de la vegetación, la cubierta y la abundancia de macrófitos anfibios fueron mayores en el sector cerrado; en cambio, el número de especies fue mayor en el abierto al ganado. Eleocharis bonariensis (19%), Paspalum distichum (17%) y Cynodon dactylon (15%) fueron dominantes dentro del cierre, mientras que el pasto exótico C. dactylon dominó (63%) en el pastoreo. Con respecto a las variables del suelo, un PCA distingue los dos sectores en el primer componente (35% de la varianza total), y los dos márgenes del cerrado están separados a lo largo del segundo eje (25%). Esta separación de los sectores y los márgenes es consistente con el análisis de ordenación (NMDS) realizado entre las especies. En este estudio de caso, los cambios observados en la estructura de la comunidad después de dos años de cierre pueden mejorar la capacidad de la zona ribereña para regular los intercambios entre la tierra y el curso de agua.Livestock is a main perturbation for the riparian zones of streams in the Buenos Aires province. Our goal is to compare the vegetation’s and soil’s characteristics of two almost contiguous reaches of the Nutrias stream, an affluent to the Reconquista river. One reach has been closed to cattlefor 2 years, and the other -500m downstream- has kept livestock along the whole period. For each stream margin, six 10m transects were sampled for species cover and 3 soil samples were drawn for organic matter, phosphorus, pH, conductivity and apparent density determination. The vegetation’s canopy hight, cover, and the amphibious macrophytes’ abundance were higher in the closed reach; instead, species number was higher in the reach opened to cattle. Eleocharis bonariensis (19%), Paspalum distichum (17%) y Cynodon dactylon (15%) were dominant within the closure, while the exotic grass C. dactylon dominated (63%) in the grazed reach. Regarding the soil variables, a PCA distinguishes the two reaches in the first component (35% of the total variance), and the two margins of the closed reach are separated along the 2nd axis (25%). This separation of the reaches and the margins is consistent with the ordination analysis (NMDS) performed among the species. In this case study, the observed changes in the community structure after two years of closure may enhance the riparian zone’s capability to regulate the exchanges between land and watercourse

La calidad del agua del Río Luján (Buenos Aires) y el potencial aporte del biofilm para su evaluación

Luján River rises in the north-eastern part of Buenos Aires Province and flows through a lowland region where it joins the River Plate Estuary. The river’s upper basin comprises a rural area which is mainly used for extensive agriculture and livestock with industrial areas of minor influence. As moving downstream, densely populated urban regions develop and industrial activity increases. Samples were collected seasonally from August 2004 to August 2005 in 12 sampling sites located along the river basin, from its headwater tributaries (Los Leones y El Durazno streams) to the crossing of the national route 9, located in the river’s lower basin. In two out of the four sampling occassions, biofilm samples were taken with the aim of assesing to what extent the biofilm community fitted the degradation level indicated by the measured physical-chemical variables of the river water (particularly BOD; N; P and DO concentrations). The samples were taken with a 3 cm2 brush and piston from submerged surfaces of natural (“tosca”) or artificial substrates (piers; walls). Bacillariophyta generally dominates the biofilm, but there seems to be a relationship between the industrial and urban sewage discharges, the water quality and the relative abundance of the different biofilm groups. In the river reaches where a heavy load of effluents is discharged, an increment of Cyanophyceae is observed. In the reaches of intermediate degradation, associations of cyanophytes and euglenoids appear. Over the course of the river, the algae abundance diminishes along with the water quality degradation, but there are also reaches of recovery due to the river’s own processing capacity where no urban nor industrial wastewaters are discharged.El río Luján nace en la zona NE de la provincia de Buenos Aires y fluye a través de una región de tierras bajas donde se une con el estuario del Río de la Plata. La cuenca superior del río comprende un área rural que se utiliza principalmente para la agricultura extensiva y el ganado con áreas industriales de poca influencia. A medida que avanzamos río abajo, se desarrollan regiones urbanas densamente pobladas y aumenta la actividad industrial. Las muestras se colectaron estacionalmente desde agosto de 2004 hasta agosto de 2005 en 12 sitios de muestreo ubicados a lo largo de la cuenca, desde sus afluentes de agua de cabecera (los arroyos Los Leones y El Durazno) hasta el cruce de la ruta nacional 9, ubicada en la cuenca baja del río. En dos de las cuatro ocasiones de muestreo, se tomaron muestras de biofilm con el objetivo de evaluar en qué medida la comunidad de biofilm se ajustó al nivel de degradación indicado por las variables físico-químicas medidas del agua del río (en particular las concentraciones de DBO; N; P y DO). ). Las muestras se tomaron con un cepillo de 3 cm2 y un émbolo de superficies sumergidas de sustratos naturales ("tosca") o artificiales (pilares, paredes). Bacillariophyta generalmente domina el biofilm, pero parece haber una relación entre las descargas de aguas residuales industriales y urbanas, la calidad del agua y la abundancia relativa de los diferentes grupos de biofilm. En el río, donde se descarga una gran cantidad de efluentes, se observa un incremento de Cyanophyceae. En los alcances de la degradación intermedia, aparecen asociaciones de cianofitos y euglenoides. En el curso del río, la abundancia de algas disminuye junto con la degradación de la calidad del agua, pero también hay zonas de recuperación debido a la propia capacidad de procesamiento del río, donde no se descargan aguas residuales urbanas ni industriales

Descomposición de macrófitas en el arroyo Las Flores (Buenos Aires)

The macrophytes contribute significantly to the autochthonous primary production of the streams of the Buenos Aires province. Their biomass is partly exported, mainly during floods, and partly incorporated to the detritus pathway of the water bodies. The aim of this study is to determine the losses in weight and nitrogen along the process of decomposition of Lemna gibba and Ceratophyllum demersum, two of the dominant species in the Las Flores stream. A total of 40 bags with 4 g (fresh weight) of L. gibba and 10 g of C. demersum were set in two sites of the stream. Periodically, 4 samples of each species were redrawn, and the dry weight and total nitrogen concentration were determined. Lemna gibba lost 50% of its weight in 4 days, from then on and until the end of the incubation period (50 days) the weight kept approximately constant, fitted to a Hill’s function with a maximum rate of 0.158 day-1. The weight of C. demersum was almost stable until day 44, and at the end of the following 42 days it was observed that it had lost 62% of its initial weight, with a constant rate of k = 0.0203 day-1. In L. gibba essay, nitrogen concentration lowered from 3.4% to 2.4% in the first 48 hours, thus representing a 52% loss of the total nitrogen content of the plant. For C. demersum, nitrogen concentration decayed from 4.1% until 3.2%; by the end of the sampling, the total nitrogen content had reduced to 33.5% of the initial value. The results indicate that, given the quickness of the decomposition and nutrient release, an important part of the production can be incorporated to the material cycles of the stream before the plants are washed downstream during floods.The macrophytes contribute significantly to the autochthonous primary production of the streams of the Buenos Aires province. Their biomass is partly exported, mainly during floods, and partly incorporated to the detritus pathway of the water bodies. The aim of this study is to determine the losses in weight and nitrogen along the process of decomposition of Lemna gibba and Ceratophyllum demersum, two of the dominant species in the Las Flores stream. A total of 40 bags with 4 g (fresh weight) of L. gibba and 10 g of C. demersum were set in two sites of the stream. Periodically, 4 samples of each species were redrawn, and the dry weight and total nitrogen concentration were determined. Lemna gibba lost 50% of its weight in 4 days, from then on and until the end of the incubation period (50 days) the weight kept approximately constant, fitted to a Hill’s function with a maximum rate of 0.158 day-1. The weight of C. demersum was almost stable until day 44, and at the end of the following 42 days it was observed that it had lost 62% of its initial weight, with a constant rate of k = 0.0203 day-1. In L. gibba essay, nitrogen concentration lowered from 3.4% to 2.4% in the first 48 hours, thus representing a 52% loss of the total nitrogen content of the plant. For C. demersum, nitrogen concentration decayed from 4.1% until 3.2%; by the end of the sampling, the total nitrogen content had reduced to 33.5% of the initial value. The results indicate that, given the quickness of the decomposition and nutrient release, an important part of the production can be incorporated to the material cycles of the stream before the plants are washed downstream during floods

The DUNE Far Detector Vertical Drift Technology, Technical Design Report

International audienceDUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

The DUNE Far Detector Vertical Drift Technology, Technical Design Report

International audienceDUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

The DUNE Far Detector Vertical Drift Technology, Technical Design Report

International audienceDUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

The DUNE Far Detector Vertical Drift Technology, Technical Design Report

DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

The DUNE Far Detector Vertical Drift Technology, Technical Design Report

International audienceDUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

The DUNE Far Detector Vertical Drift Technology, Technical Design Report

International audienceDUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals