Advancements in sample preparation for performing trace analysis of inorganic analytes are coming from the dissemination of microwave-assisted procedures, but there is still room for improvements by looking for simple and easily applied procedures. Recently it was proposed a new approach called single reaction chamber with capability for digestions at high pressures and temperatures using simple vials and racks. This was a limitation of former cavity microwave ovens with closed vessels. It was demonstrated here that the use of single reaction chamber approach allows the implementation of efficient digestions using diluted solutions of nitric acid and also allows addressing a critical need of sample preparation for inorganic analysis by running mixed batches of samples. The feasibility of this procedure was demonstrated for organic samples and accuracy was proved by using certified reference materials of apple leaves, bovine liver and whole milk powder. Digestions performed of whole milk powder and bovine liver using 2.0 mol L(-1) nitric acid solution plus concentrated hydrogen peroxide at 240 °C led to residual carbon contents of 0.825 and 1.50% and residual acidities of 1.04 and 0.618 mol L(-1), respectively. These parameters are fully compatible with further measurements using ICP OES or ICP-MS. Al, Cu, Fe, Mn, Mo, Rb, Se, Sr, and Zn were accurately determined by ICP OES or ICP-MS depending on their concentrations in digests.

Stream metabolism is affected by both natural and human-induced processes. While metabolism has multiple implications for ecological processes, relatively little is known about how metabolic rates are influenced by land use in tropical streams. In this study, we assessed the metabolic characteristics and related environmental factors of six streams located in a transition area from Cerrado to Atlantic Forest (São Carlos/Brazil). Three streams were relatively preserved, while three were flowing through more agriculturally and/or urban impacted watersheds. Surface water samples were analyzed for biological and physico-chemical parameters as well as discharge and percentage of canopy cover. Metabolism was determined through the single-station method to estimate gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) with BAyesian Single-station Estimation (BASE). Nutrient concentrations tended to be higher in impacted versus preserved streams (e.g., average total phosphorus between 0.028-0.042 mg L-1 and 0.009-0.038 mg L-1, respectively). Average canopy cover varied between 58 and 77%, with no significant spatial or seasonal variation. All streams were net heterotrophic (ER exceeded GPP) in all sampling periods. GPP rates were always lower than 0.7 gO2 m-2 d-1 in all streams and ER varied from 0.6 to 42.1 gO2 m-2 d-1.  Linear Mixed-Effect models showed that depth, discharge, velocity and total phosphorus are the most important predictors for GPP. For ER, depth, velocity and canopy cover are significant potential predictors. Canopy cover was the main light limiting factor and influenced stream metabolism. Our findings reinforced the concepts that shifts in the shading effect provided by vegetation (e.g., through deforestation) or changes in discharge (e.g., through land use conversion or water abstractions) can impact freshwater metabolism. Our study suggests that human activities in low latitude areas can alter tropical streams’ water quality, ecosystem function, and the degree of riparian influence. Our data showed that tropical streams can be especially responsive to increases of organic matter inputs leading to high respiration rates and net heterotrophy, and this should be considered to support management and restoration efforts.

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The use of antibiotics in animal feed, commonly used as a strategy to achieve greater daily weight gains and recently as way to reduce methane emission, might result in the selection of resistant microorganisms and certain bacterial strains isolated from cattle are resistant to multiple antibiotics and could be human health hazards. To evaluate methane production in ruminant diet without roughage containing ionized amino acids as antibiotic alternative, twenty-four Nellore young bulls were allotted into two groups. The first group was fed with high-grain diet without roughage and without antibiotics diet, containing 82 mg/kg of ionized amino acids mixture (L-lysine and L-taurine HCl 99%, pH 9.74) manufactured by MJ Animal Nutrition. The second group was fed with high-grain diet containing Brachiaria brizantha hay (15% dry matter) and sodium monensin (120 mgּּ animal -1 ּּ day-1). It was not used a negative control group to avoid metabolic disturbances. The feedlot time was 100 days. The weight measurements were performed at the beginning of the trial period and monthly, always with water restriction and fasting for 18 hours, even before slaughter. A completely randomized design was used. Methane emission was measured using the sulfur hexafluoride technique and daily dry matter intake were measured in GrowSafe system. There was no detection of lameness or laminitis in any groups and there were no changes in feed conversion ratio (FCR). The total methane emission (-77.11%) and the methane emission per dry matter intake (DMI; -57.12 %), per average daily weight gain (ADG; -71.11%) and per kilogram of carcass (-70.07%) were different between treatments (P < 0.0001), resulting in decreased emission intensities for group fed without roughage with diet containing ionized amino acids. We conclude that fed without roughage with diet containing ionized amino acids was an effective strategy as an antibiotic alternative, mitigate GHG emissions and facilitate feedlot diets management. In field conditions, the roughage-lacking diets represent advantage, especially regarding its administration to a large amount of the animals just once a week or less, no need area, infra-structure and expertise to produce, preserve and feeding roughage.