Influence of rainfall on the discharge, nutrient concentrations and loads of a stream of the "Pampa Ondulada" (Buenos Aires, Argentina)

The basin area of the Durazno Stream covers approx. 360 km2 of a plain with a gentle slope, mainly devoted to cattle farming and agriculture. This study examines the variability of chemical composition of surface water of the stream in relation to stream discharge, estimated from a hydrological deterministic model from rainfall data. Fifteen samplings were carried out, four in high flow condition and the rest in baseline flow. In each sampling, the main physico-chemical variables were determined. Since discharge data from this stream were not available, it was estimated in situ through an instantaneous unitary hydrograph model. Both estimations of stream discharge were similar. The main forms of dissolved inorganic nitrogen were ammonium and nitrate. The four significant components of PCA that explained 84.4 % of total variance were: mineral component, particulate matter content, ammonium and dissolved phosphorus levels, and nitrates' level. The decreased concentrations of major ions and conductivity during high flow condition suggest solutes' dilution by the massive inflow of water originated by rainfalls. The highest concentrations and loads of suspended solids (SS) (86 mg/l and 22638 kg/day) and particulate organic carbon (POC) (3.1 mg/l and 832 kg/day) were observed in the sample obtained during the rising limb of the hydrograph following a drought period, suggesting that basin erosive processes are more important during the first hours of the storm. Three of the samplings that were carried out in high flow conditions showed low mineral and nutrient content that revealed better water quality. In contrast, the sampling with the greatest total runoff (14.1 mm) showed high concentrations of ammonium (1205 μg/l) and dissolved phosphorus (561 μg/l), suggesting that a long stagnant period on soils with low permeability, could favor reduction processes of nitrate to ammonium and mobilization of dissolved phosphorus to overlying water. The nutrients' loads increased in high flow conditions most likely due to runoff from the riverbank soils. The rise of nutrients, SS, POC and total organic carbon (TOC), loads in the same or in higher proportion than the stream discharge, alerts on the risk of contamination of surface water in an agricultural basin.La cuenca del Arroyo Durazno abarca aproximadamente 360 km2 de una llanura con suave pendiente, dedicada principalmente a ganadería y agricultura. Este estudio examina la variabilidad en la composición química del agua superficial del arroyo en relación con el caudal estimado a través de un modelo hidrológico determinístico a partir de los datos de lluvia. Se realizaron quince muestreos: cuatro en condiciones de alto caudal, los restantes en caudal base. En cada muestreo se determinaron las principales variables fisico-químicas. Dado que no existen datos publicados de caudal de este arroyo, se lo estimó in situ, y a partir del modelo de hidrograma unitario. Ambas estimaciones resultaron similares. Las principales formas de nitrógeno inorgánico disuelto fueron amonio y nitrato. Los primeros 4 factores extraídos del PCA que explicaron 84.4 % de la varianza total fueron: componente mineral, contenido de material particulado, niveles de amonio y fósforo disuelto y nivel de nitratos. El decrecimiento de iones mayoritarios y conductividad durante las condiciones de alto caudal sugiere su dilución por la entrada masiva de agua por lluvias. Las mayores concentraciones y cargas de sólidos suspendidos (SS) (86 mg/l y 22638 kg/día) y carbono orgánico particulado (COP) (3.1 mg/l y 832 kg/día) se hallaron en el muestreo realizado durante la rama ascendente del hidrograma posterior a un período de sequía, sugiriendo que los procesos erosivos de la cuenca son más importantes en las primeras horas de la tormenta. Tres de los muestreos realizados en condiciones de alto caudal presentaron bajo contenido mineral y de nutrientes, indicando mejor calidad de agua. En cambio en el muestreo de mayor lámina de escorrentía acumulada (14.1 mm) las concentraciones de amonio (1205μg/l) y fósforo disuelto (561μg/l) fueron elevadas, sugiriendo que un prolongado periodo de estancamiento en un suelo de baja permeabilidad favorecería los procesos de reducción de nitratos a amonio y la movilización de fósforo disuelto al agua de inundación. Las cargas de nutrientes aumentaron en condiciones de alto caudal probablemente debido al aporte por escorrentía de suelos ribereños. El ascenso en las cargas de nutrientes, SS, COP y carbono orgánico total en igual o mayor magnitud que el caudal alerta sobre el riesgo de contaminación de las aguas superficiales en una cuenca agrícola

Interacción entre <i>Salvinia minima</i> y <i>Lemna gibba</i>: efecto sobre el crecimiento en distintos medios de cultivo

Nutrient uptake and competitive ability of the aquatic species Lemna gibba and Salvinia minima were evaluated. The experiment was carried out in a greenhouse and plants were grown as mono-plant cultures and mixed-plant cultures. Three different media were used: tap water and the chemically defined media Lemna and Hutner 1/10. Duration of the experiment was 7 days. Initial and final dry weights and DIN and SRP concentrations were determined. Relative growth rates (RGR) and nutrient uptake rates were calculated. L. gibba´s RGR values increased significantly in Hutner 1/10 medium when types of cultures were analyzed separately. RGR values decreased in Lemna and Hutner 1/10 media in mixed-plant cultures. S. minima did not show significant differences in its RGR values. In mono-plant cultures N and P uptake rates in Lemna medium were significantly larger for L. gibba. In Hutner 1/10 medium P uptake rate was greater for S. minima and N uptake rate was larger for L. gibba. The presence of S. minima negatively affected L. gibba´s growth.Instituto de Limnología "Raúl A. Ringuelet

Interacción entre <i>Salvinia minima</i> y <i>Lemna gibba</i>: efecto sobre el crecimiento en distintos medios de cultivo

Nutrient uptake and competitive ability of the aquatic species Lemna gibba and Salvinia minima were evaluated. The experiment was carried out in a greenhouse and plants were grown as mono-plant cultures and mixed-plant cultures. Three different media were used: tap water and the chemically defined media Lemna and Hutner 1/10. Duration of the experiment was 7 days. Initial and final dry weights and DIN and SRP concentrations were determined. Relative growth rates (RGR) and nutrient uptake rates were calculated. L. gibba´s RGR values increased significantly in Hutner 1/10 medium when types of cultures were analyzed separately. RGR values decreased in Lemna and Hutner 1/10 media in mixed-plant cultures. S. minima did not show significant differences in its RGR values. In mono-plant cultures N and P uptake rates in Lemna medium were significantly larger for L. gibba. In Hutner 1/10 medium P uptake rate was greater for S. minima and N uptake rate was larger for L. gibba. The presence of S. minima negatively affected L. gibba´s growth.Instituto de Limnología "Raúl A. Ringuelet

Remark on charge conjugation in the non relativistic limit

We study the non relativistic limit of the charge conjugation operation $\cal C$ in the context of the Dirac equation coupled to an electromagnetic field. The limit is well defined and, as in the relativistic case, $\cal C$, $\cal P$ (parity) and $\cal T$ (time reversal) are the generators of a matrix group isomorphic to a semidirect sum of the dihedral group of eight elements and $\Z_2$. The existence of the limit is supported by an argument based in quantum field theory. Also, and most important, the limit exists in the context of galilean relativity. Finally, if one complexifies the Lorentz group and therefore the galilean spacetime $x_\mu$, then the explicit form of the matrix for $\cal C$ allows to interpret it, in this context, as the complex conjugation of the spatial coordinates: $\vec{x} \to \vec{x}^*$. This result is natural in a fiber bundle description.Comment: 8 page

Evaluation of inflammatory cytokine secretion by human alveolar macrophages.

The alveolar macrophage (AM) secretes interleukin 1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-8 (IL-8), all of them inflammatory cytokines involved in the pathogenesis of many lung diseases. The aim of the present work was to evaluate the basal and stimulated secretion of these cytokines by human AMs. Human AMs were collected by bronchoalveolar lavage (BAL) from four healthy controls and 13 patients with diffuse interstitial lung disease (five cases of sarcoidosis, three of hypersensitivity pneumonitis and five of idiopathic pulmonary fibrosis). AMs were cultured in the presence or absence of different concentrations of lipopolysaccharide (LPS), phorbolmyristate and gamma-interferon. IL-1beta, TNF-alpha, IL-6 and IL-8 levels were measured in BAL fluid and culture supernatant using specific enzyme-linked immunosorbent assays. The substance found to stimulate the secretion of inflammatory cytokines to the greatest extent was LPS at a concentration of 10 microg/ml. Regarding the secretion of IL-1beta, four observations were of interest: basal secretion was very low; LPS exerted a potent stimulatory effect; considerable within-group variability was observed; and there were no significant differences in the comparisons among groups. With respect to TNF-alpha secretion, the results were similar. The only striking finding was the higher basal secretion of this cytokine with respect to that of IL-1beta. Regarding the secretion of IL-6, the same pattern followed by TNF-alpha was found. However, it should be stressed that the increase induced by LPS was smaller than in the two previous cytokines. Regarding the secretion of IL-8, three findings were patent: the strong basal secretion of this cytokine; the moderate increase induced by LPS; and the existence of significant differences among the different groups with respect to the stimulated secretion of this cytokine, which reached maximum values in patients with idiopathic pulmonary fibrosis. Finally, it should be noted that the pattern of cytokines observed in the BAL fluid was similar to that found in cultured AM supernatants. The pattern of inflammatory cytokine secretion by AMs differs from that of other cells of the mononuclear phagocyte system (MPS). In this sense. AMs secrete low amounts of IL-1, moderate amounts of TNF-alpha and IL-6, and high quantities of IL-8. Adherence is an important stimulus in the secretion of these molecules and LPS elicits an increased secretion inverse to the basal secretion. There is considerable individual variability in the secretion of inflammatory cytokines by the AMs of patients with interstitial lung disease and the AMs of these patients are primed in vivo for the secretion of these cytokines. The results of our study, carried out in vitro, can be extrapolated to the in vivo setting

Oxidative Stress Accumulates in Adipose Tissue during Aging and Inhibits Adipogenesis

Aging constitutes a major independent risk factor for the development of type 2 diabetes and is accompanied by insulin resistance and adipose tissue dysfunction. One of the most important factors implicitly linked to aging and age-related chronic diseases is the accumulation of oxidative stress. However, the effect of increased oxidative stress on adipose tissue biology remains elusive. In this study, we demonstrate that aging in mice results in a loss of fat mass and the accumulation of oxidative stress in adipose tissue. In vitro, increased oxidative stress through glutathione depletion inhibits preadipocyte differentiation. This inhibition of adipogenesis is at least in part the result of reduced cell proliferation and an inhibition of G1→S-phase transition during the initial mitotic clonal expansion of the adipocyte differentiation process. While phosphorylation of the retinoblastoma protein (Rb) by cyclin/cdk complexes remains unaffected, oxidative stress decreases the expression of S-phase genes downstream of Rb. This silencing of S phase gene expression by increased oxidative stress is mediated through a transcriptional mechanism involving the inhibition of E2F recruitment and transactivation of its target promoters. Collectively, these data demonstrate a previously unrecognized role of oxidative stress in the regulation of adipogenesis which may contribute to age-associated adipose tissue dysfunction

Evaluación de la capacidad de auto-depuración de un arroyo urbano y el uso de macrófitas nativas como estrategia de restauración

Environmental degradation is one of the most serious problems in the metropolitan area of Buenos Aires, especially water pollution. The main aim of this work was to study mechanisms of self-purifying of a segment of San Francisco stream (located in Almirante Brown district), evaluating it in situ capacity of self-purifying downstream of a tubing and, in addition, by static bioassays in a greenhouse with native macrophytes. A stream section of 1500m was sampled twice during autumn 2013. The stream was generally hypoxic throughout the section (DO<2 mg/l), presenting low velocity (0.084 ± 0.008 m/s), moderate organic load (COD=72 ± 3 mg/l), high dissolved inorganic nitrogen (9.2 ± 0.9 mg/l) mostly as ammonium, and high levels of coliforms (7600 ± 700 cfu/ml). There was no increase in the dissolved oxigen and no decrese in the nutrients and COD along the section, suggesting that the self-purifying process for this parameters, along this section and this time of this year was negligible. Almost complete removal of ammonium (90-95%) and nitrites was observed in the bioassays. Based on our results, the present condition of the stream may be modified by increasing water oxygenation and macrophytes biomass, among others strategies. It is planned to incorporate the analysis of seasonal effects and complementary bioassays with macrophytes minimizing the algal growth.Facultad de Ciencias Naturales y Muse

Evaluación de la capacidad de auto-depuración de un arroyo urbano y el uso de macrófitas nativas como estrategia de restauración

Environmental degradation is one of the most serious problems in the metropolitan area of Buenos Aires, especially water pollution. The main aim of this work was to study mechanisms of self-purifying of a segment of San Francisco stream (located in Almirante Brown district), evaluating it in situ capacity of self-purifying downstream of a tubing and, in addition, by static bioassays in a greenhouse with native macrophytes. A stream section of 1500m was sampled twice during autumn 2013. The stream was generally hypoxic throughout the section (DO<2 mg/l), presenting low velocity (0.084 ± 0.008 m/s), moderate organic load (COD=72 ± 3 mg/l), high dissolved inorganic nitrogen (9.2 ± 0.9 mg/l) mostly as ammonium, and high levels of coliforms (7600 ± 700 cfu/ml). There was no increase in the dissolved oxigen and no decrese in the nutrients and COD along the section, suggesting that the self-purifying process for this parameters, along this section and this time of this year was negligible. Almost complete removal of ammonium (90-95%) and nitrites was observed in the bioassays. Based on our results, the present condition of the stream may be modified by increasing water oxygenation and macrophytes biomass, among others strategies. It is planned to incorporate the analysis of seasonal effects and complementary bioassays with macrophytes minimizing the algal growth.Facultad de Ciencias Naturales y Muse