Expression of ion transport proteins and routine metabolism in juveniles of tropical gar (Atractosteus tropicus) exposed to ammonia.

Tropical gar (Atractosteus tropicus) thrives in aquatic habitats with high levels of total nitrogen (TAN) and unionized ammonia (NH3). However, the tolerance of TAN and NH3, the excretion mechanisms involved, and the effects of these chemicals on routine metabolism are still unknown. Therefore, our objectives were to assess the acute toxicity of TAN and NH3 in A. tropicus juveniles after a 96-h exposure (LC50-96 h) to NH4Cl and after chronic exposure to two concentrations (15% and 30% of LC50-96 h TAN) for 12 days, as well as to evaluate the transcriptional effects associated with Rhesus proteins (rhag, rhbg, rhcg) and ion transporters (NHE, NKA, NKCC, and CFTR) in gills and skin; and to determine the effects of TAN and NH3 on routine metabolism through oxygen consumption (µM g-1 h-1) and gill ventilation frequency (beats min-1). LC50-96 h values were 100.20 ± 11.21 mg/L for TAN and 3.756 ± 0.259 mg/L for NH3. The genes encoding Rhesus proteins and ion transporters in gills and skin showed a differential expression according to TAN concentrations and exposure time. Oxygen consumption on day 12 showed significant differences between treatments with 15% and 30% TAN. Gill ventilation frequency on day 12 was higher in fish exposed to 30% TAN. In conclusion, A. tropicus juveniles are highly tolerant to TAN, showing upregulation of the genes involved in TAN excretion through gills and skin, which affects routine oxygen consumption and energetic cost. These findings are relevant for understanding adaptations in the physiological response of a tropical ancestral air-breathing fish.

Carga contaminante de los residuos sólidos municipales en la cabecera departamental de Jalapa, Guatemala / Pollution load of municipal solid waste in the City of Jalapa, Guatemala

Se expone la carga contaminante de los residuos sólidos municipales, en la cabecera departamental de Jalapa, Guatemala. Cada residuo, sin importar su origen o forma, tiene una composición química específica, la cual indicará su grado de contaminación o carga contaminante. El estudio se enfocó en el análisis de los residuos sólidos de tipo domiciliar, institucional, comercial, mercados y barrido y limpieza de calles por un periodo de cinco días. La muestra se analizó mediante la determinación de las fracciones de composición de los residuos, clasificándolos en: papel, cartón, plástico, pet, restos de comida, duroport, textiles, hule, vidrio, papel higiénico, pañales y madera. Para el cálculo de la carga contaminante se multiplicó los porcentajes que aporta el carbono, hidrógeno, oxígeno, nitrógeno y azufre a cada fracción de los residuos por el peso total de cada componente para luego dividirlo por el peso atómico. Para minimizar la carga contaminante de los residuos sólidos, la recolección debe darse con una frecuencia mínima de dos veces por semana, para evitar proceso de descomposición, pudiendo generar vectores y enfermedades en los sitios temporales de disposición que afecten a la población. El volumen de los desechos generados por el barrido de calles presenta la mayor carga contaminante, dando como resultado porcentajes altos en los componentes de carbono, hidrogeno, oxígeno y nitrógeno, sin embargo, la misma puede reducirse implementando prácticas de valorización como el compostaje. Uno de los grandes problemas es el aporte de nitrógeno que en cantidades excesivas puede causar contaminación al suelo y a cuerpos de agua superficial.

The pollution load of municipal solid waste in the departmental capital of Jalapa is discussed. Each waste, regardless of their origin or form, has a specific chemical composition, which shall indicate the degree of pollution or pollution load. The study focused on the analysis of solid waste type household, institutional, comercial and street sweeping for a period of five days. The sample was analyzed by determining the fractions of waste composition, classifying them into paper, cardboard, plastic, pet, food scraps, styrofoam, textiles, rubber, glass, toilet paper, diapers and wood. To calculate the pollution load percentages provided by the carbon, hydrogen, oxygen, nitrogen and sulfur to each fraction multiplied by the total weight of each component and then divided by the atomic weight. To minimize the pollution load of solid waste, collection must occur with a frequency of twice a week, in order to avoid decomposition process, potentially leading to disease vectors and temporary disposal sites affecting the population. The volume of waste generated by street sweeping has the highest pollution load, resulting in high percentages of the carbon, hydrogen, oxygen and nitrogen components, but this can be reduced by implementing recovery practices such as composting. One of the big problems is the contribution of nitrogen that in excessive amounts can cause contamination to the soil and bodies of superficial water.

Ecotoxicological effects of pig manure on Folsomia candida in subtropical Brazilian soils.

The effects of pig manure, from diets incorporating veterinary pharmaceuticals, on survival and reproduction of Folsomia candida were evaluated. Manures derived from the following diets: corn and soymeal (CS); 85% CS diet+15% wheat meal (TR); CS diet+100ppm doxycycline+50ppm colistin+2500ppm Zn oxide (CSa); TR diet+100ppm doxycycline+50ppm colistin+2500ppm Zn oxide (TRa). Manures were tested in two subtropical soils representative of southern (Oxisol and Entisol). Despite the antibiotics no significant differences were found between the four manures within each soil. However, strong differences were found on the toxicity between soils. In Oxisol, LC50 values were around 100m(3)ha(-1), and EC50 values around 80m(3)ha(-1). In Entisol these were much lower, with LC50 values oscillating around 20m(3)ha(-1) and EC50 values between 10-15m(3)ha(-1). The observed toxicity on both soils was attributed to excess of nitrogen, Cu and Zn in the highest doses. The strong difference between soils could be explained by soil properties, namely CEC, organic matter, and clay contents that were lower in Entisol, indicating a poor ability to retain contaminants increasing their availability in soil. Results suggest that the application of these residues should be regulated not only using a volume-based criterion, but should incorporate data on soil properties, complemented by an ecotoxicological assessment.

Behavior of Typha angustifolia L. in a free water surface constructed wetlands for the treatment of swine wastewater.

The objective of this study was to evaluate the behavior of Typha angustifolia L. in nitrogen retention in a Free Water Surface Constructed Wetland (FWS) for the swine wastewater treatment over a three-year operating period. Results show that the behavior of Typha angustifolia L. in a FWS for treatment of swine wastewater is affected by nitrogen concentration, seasonal variation and plant establishment in the system. Indeed, the application of Nitrogen Loading Rates (NLR) between 7.1-14.3 kg TN/ha·d removes 40% of Total Nitrogen (TN), where the maximum removal (20-40%) takes place in the spring-summer seasons. However, concentrations higher than 120.3 mg NH4 (+)-N/L significantly decrease (P = 0.004) diametrical growth by 55%. However, it was possible to estimate that NLR >14.3 kg TN/ha·d increased biomass production and plant uptake in Typha angustifolia L. during the period analyzed. Additionally, aboveground biomass values were between 1.509.6-2.874.0 g/m(2) and nitrogen uptake 27.4-40.8 g/m(2), where this last value represents 29% of the TN applied during the study. Finally, the TN accumulation in sediments represents less than 2% of the TN incorporated during this period. These results show that an increase of 50% of the TN in sediments increases plant abundance in 73%, which is related to the mineralization processes favored in the system during the last year of operation.

Diversity of shrub tree layer, leaf litter decomposition and N release in a Brazilian Cerrado under N, P and N plus P additions.

This study investigated changes in diversity of shrub-tree layer, leaf decomposition rates, nutrient release and soil NO fluxes of a Brazilian savanna (cerrado sensu stricto) under N, P and N plus P additions. Simultaneous addition of N and P affected density, dominance, richness and diversity patterns more significantly than addition of N or P separately. Leaf litter decomposition rates increased in P and NP plots but did not differ in N plots in comparison to control plots. N addition increased N mass loss, while the combined addition of N and P resulted in an immobilization of N in leaf litter. Soil NO emissions were also higher when N was applied without P. The results indicate that if the availability of P is not increased proportionally to the availability of N, the losses of N are intensified.

The impact of ammonia nitrogen concentration and zeolite addition on the specific methanogenic activity of granular and flocculent anaerobic sludges.

This work presents the effect of ammonia nitrogen concentration and zeolite addition on the specific methanogenic activity (SMA) of different anaerobic sludges with various physical structures (granular and flocculent), operating in batch conditions. Piggery, malting production and urban sludges derived from full-scale anaerobic reactors were tested in the experiment as the source of inoculum in batch digesters. It was found that piggery sludge was the most affected by the increase of ammonia nitrogen concentration while malting producing and municipal sludges were less affected. In general, the addition of zeolite at doses in the range of 0.01-0.1 g/g VSS reduced the inhibitory effect of N-NH(4)(+) for piggery sludge (P.S.). For this sludge, the propionic:acetic ratio increased when the concentration of N-NH(4)(+) increased, indicating that methanogenesis was affected. Finally, a study of the microbial population involved in this study for P.S. by using 16S rRNA based molecular techniques revealed a presence of microorganisms following the order: Methanococcaceae > Methanosarcina > Methanosaeta.

Effects of initial climatic conditions on growth and accumulation of fluoride and nitrogen in leaves of two tropical tree species exposed to industrial air pollution.

Saplings of Tibouchina pulchra and Psidium guajava, cultivated under standardized soil conditions, were placed in two sites at Cubatão (state of São Paulo, southeast Brazil) to study the effects of air pollution on growth, biomass allocation and foliar nitrogen and fluoride concentrations. Thirty-six potted plants were maintained over two periods of one year (Jul/00 to Jun/01; Dec/00 to Nov/01) at each of two experimental sites with distinct levels of air pollution: Pilões River Valley (PV) with vegetation virtually unaffected by air pollution; and Mogi River Valley (MV) severely affected by pollutants released mainly by chemical, fertilizer, iron and steel industries. For both species, saplings growing at MV showed alterations of growth and biomass allocation, as well as increased leaf concentrations of nitrogen and fluoride. Comparing both experimental periods, the one starting in winter (the driest season in Southeastern Brazil) seemed to affect the saplings more severely, the differences of the measured parameters between MV and PV being higher than in the second period. Multivariate analysis revealed two groups of data: one representing the MV and the other the PV saplings. For both species, saplings growing at MV showed differences in chemical composition, growth and biomass allocation, compared with the PV saplings. The results suggested that seasonal conditions of the first months of sapling exposure (summer or winter) modulate the intensity of responses to pollution stress.