Carbon sequestration rates in Swedish forest soils : a comparison of three approaches

Selective papers of the workshop on "Development of models and forest soil surveys for monitoring of soil carbon", Koli, Finland, April 5-9 2006.

Wood consumption rates of forest species by subterranean termites (Isoptera) under field conditions

Termites are well -known for their capacity to damage and destroy wood and wood products of all kinds in the tropics and subtropics. A field test was undertaken to evaluate variations in wood consumption of Pinus sp. and three species of Eucalyptus by subterranean termites. The test consisted of wooden stakes of each species being initially submitted to water immersion for 0, 24, 48 and 72 h, and buried in the ground to natural infestation by subterranean termites for an exposure period of 30, 45 and 60 days. Three species of subterranean termites were identified: Heterotermes longiceps (Snyder), Coptotermes gestroi (Wasmann) (Isoptera: Rhinotermitidae), and Nasutitermes jaraguae (Holmgren) (Isoptera: Termitidae). This is the first record of occurrence of H. longiceps in the state of Rio de Janeiro. Although the wood-consumption rates were not correlated significantly with their wood densities, there was a tendency of the softwoods (E. robusta and Pinus sp.) to be more consumed by subterranean termites than the woods of intermediate hardness (E. pellita and E. urophylla). Among the eucalyptus, E. robusta showed to be more susceptible to attack by subterranean termites than E. pellita and E. urophylla

Swine effluent treatment using anaerobic digestion at different loading rates

The industrial swine production is characterized by generation of significant effluent amounts that require treatment. The most adopted practices by Brazilian swine farmers have been wastewater storage in lagoons and its subsequent use as a biofertilizer. Nutrient accumulation in soil and water creates the need for an effective management of these residues. The anaerobic digestion process is an important alternative and low-cost treatment for organic matter reduction. However, its efficiency is limited by the digester capacity of solid degradation, especially at low hydraulic retention times. Thus, the present study aimed to verify the behavior of an upflow anaerobic digester by increasing the organic loading rate. This was accomplished in three stages using, as a parameter, volatile solids at 0.5; 1.0 and 1.5 kgVS m-3 d-1, respectively. This digester model proved to be quite robust and effective in swine manure treatment, achieving high efficiency of volatile solid removal at all stages of the study (stage 1: 61.38%; stage 2: 55.18%; and stage 3: 43.18%). Biogas production was directly related to the increasing organic load, reaching 0.14, 0.85, and 0.86 Nm³ kgVS-1add., respectively, with no significant difference (p<0.05) of biogas methane concentration among the studied stages (73.7, 75.0, and 77.9%).

Different pathways in the larval development of the crab Ucides cordatus (Decapoda, Ocypodidae) and their relation with high mortality rates by the end of massive larvicultures

One of the most limiting factors affecting the larval rearing of Ucides cordatus in the laboratory is a period of high mortality, which usually occurs late in the course of the larviculture during the metamorphosis from the zoeal to the megalopal phase. The objective of the present research was to analyze the post-embryonic development of U. cordatus on an individual basis and, in particular, to search for patterns linking disturbances in the molting process to the high larval death rates observed in massive larvicultures. A total of 50 larvae were individually reared from hatching to metamorphosis into the megalopal phase under controlled conditions, fed a combination of microalgae and rotifers. The survivorship rate was 70% until zoea V. The 35 surviving zoea V larvae followed two different pathways. Eleven underwent metamorphosis directly to megalopa, eighteen molted to zoea VI and six died as zoea V. In the last molting event, only two zoea VI larvae reached the megalopal stage, while the remaining sixteen died. In further observation under microscope, 13 of the dead zoea VI showed characteristics of the pre-molt stage and pereiopods disproportionably large in relation to the carapace. The observed pattern resembles the Molt Death Syndrome (MDS) described for other decapod species, in which larvae die in the late pre-molt phase of the molting cycle. We suggest that U. cordatus larvae develop disturbances in the molting process similar to the MDS described for other species and that these disturbances are related to a more complex pathway involving the emergence of larval stage zoea VI.

Oxidation rates of carbon and nitrogen in char residues from solid fuels

Computational fluid dynamics (CFD) modeling is an important tool in designing new combustion systems. By using CFD modeling, entire combustion systems can be modeled and the emissions and the performance can be predicted. CFD modeling can also be used to develop new and better combustion systems from an economical and environmental point of view. In CFD modeling of solid fuel combustion, the combustible fuel is generally treated as single fuel particles. One of the limitations with the CFD modeling concerns the sub-models describing the combustion of single fuel particles. Available models in the scientific literature are in many cases not suitable as submodels for CFD modeling since they depend on a large number of input parameters and are computationally heavy. In this thesis CFD-applicable models are developed for the combustion of single fuel particles. The single particle models can be used to improve the combustion performance in various combustion devices or develop completely new technologies. The investigated fields are oxidation of carbon (C) and nitrogen (N) in char residues from solid fuels. Modeled char-C oxidation rates are compared to experimental oxidation rates for a large number of pulverized solid fuel chars under relevant combustion conditions. The experiments have been performed in an isothermal plug flow reactor operating at 1123-1673 K and 3-15 vol.% O2. In the single particle model, the char oxidation is based on apparent kinetics and depends on three fuel specific parameters: apparent pre-exponential factor, apparent activation energy, and apparent reaction order. The single particle model can be incorporated as a sub-model into a CFD code. The results show that the modeled char oxidation rates are in good agreement with experimental char oxidation rates up to around 70% of burnout. Moreover, the results show that the activation energy and the reaction order can be assumed to be constant for a large number of bituminous coal chars under conditions limited by the combined effects of chemical kinetics and pore diffusion. Based on this, a new model based on only one fuel specific parameter is developed (Paper III). The results also show that reaction orders of bituminous coal chars and anthracite chars differ under similar conditions (Paper I and Paper II); reaction orders of bituminous coal chars were found to be one, while reaction orders of anthracite chars were determined to be zero. This difference in reaction orders has not previously been observed in the literature and should be considered in future char oxidation models. One of the most frequently used comprehensive char oxidation models could not explain the difference in the reaction orders. In the thesis (Paper II), a modification to the model is suggested in order to explain the difference in reaction orders between anthracite chars and bituminous coal chars. Two single particle models are also developed for the NO formation and reduction during the oxidation of single biomass char particles. In the models the char-N is assumed to be oxidized to NO and the NO is partly reduced inside the particle. The first model (Paper IV) is based on the concentration gradients of NO inside and outside the particle and the second model is simplified to such an extent that it is based on apparent kinetics and can be incorporated as a sub-model into a CFD code (Paper V). Modeled NO release rates from both models were in good agreement with experimental measurements from a single particle reactor of quartz glass operating at 1173-1323 K and 3-19 vol.% O2. In the future, the models can be used to reduce NO emissions in new combustion systems.

Response of weed populations to tillage, reduced herbicide and fertilizer rates in wheat (Triticum aestivum) production

Field experiments were carried out in 1999 and 2000 to investigate the effects of conventional (CT) and no-tillage (NT) systems, interacting with three herbicide dose levels and three nitrogen (N) levels on weed growth and wheat production of two varieties. There was a higher grain yield for NT system compared with CT in one year. CT weed biomass was lower than from NT weed biomass, in both varieties. No differences on wheat biomass and grain yield were observed between full and reduced herbicide rates. N fertilizer increased wheat biomass and grain yield significantly. Only N medium level had an effect upon weed biomass with respect to non-fertilized plots, while the highest fertilization rate lowered weed biomass. Conventional tillage, reduced herbicide rates and nitrogen fertilization were effective ways of limiting weed production in wheat.

Rice seedling and plant development as affected by increasing rates of penoxsulam under controlled environments

Rice is a major staple in many countries. Weed control is one of the factors limiting higher rice yield. ALS (acetolactate synthase)-inhibiting herbicides are desirable weed control herbicides because of their high efficacy, low toxicity to mammalians, and low rates used. An important herbicide characteristic is high selectivity to the crop, since it facilitates fast crop establishment and greater crop advantage over the weeds. The objectives of this work were to study the effects of increasing rates of the ALS-inhibiting herbicide penoxsulam on seed integrity and germination, and seedling and plant development of rice cv. BRS Pelota under controlled laboratory and greenhouse conditions. The results showed that penoxsulam affected rice germination and seedling and plant growth at rates above 54 g a.i. ha-1, and that penoxsulam is safe for rice seedling development at the currently recommended rates.

Behavior of RR soybeans subjected to different formulations and rates of glyphosate in the reproductive period

Recent studies indicate that glyphosate applied in post-emergence in RR soybean can eventually cause phytotoxic effects. However, there are many questions that need to be clarified in the scientific and technical contexts, involving the issue of RR soybeans regarding the use of glyphosate. This study has assessed the impact of the application of different doses and formulations of glyphosate in the reproductive period of RR soybean (R1 stage). For that purpose, an experiment in the field was conducted in two harvests (2011/12 and 2012/13), in which a 2 x 5 factorial design was used (formulations versus doses) totaling 10 treatments. In these two experiments the variables related to agronomic performance were: phytotoxicity (7, 14, 21 and 28 days after application), plant height, number of pods per plant, yield and weight of 100 grains (end of soy cycle). The results obtained allowed characterizing phytotoxicity and damages to the height and yield in RR soybean, with increasing rates of glyphosate applied in the reproductive period.

MANAGEMENT OF MAIZE STOVER WITH UNDERDOSES RATES OF GLYPHOSATE APPLICATIONS IN NO-TILLAGE

ABSTRACTGlyphosate has significant effects on the growth and development of plants when in underdoses. This work was developed to verify the effect of the application of glyphosate in underdoses in lignin synthesis and consequently decomposition of maize stover. Two experiments were conducted; the first one in a greenhouse for underdoses adjustments and the second one in the production area. The experimental design of the first trial was completely randomized with four replications. The treatments consisted in the application of the underdoses: 0, 25, 50 and 100 g ha-1 of glyphosate. In the production area, the experimental design was a randomized block with four replications, in underdoses: 0, 12.5, 25 and 50 g ha-1. The results were submitted to analysis of variance and regression. The underdoses of 25 g a.e. ha-1in a greenhouse promoted 36% increase in productivity of stover, in addition to increasing the lignin content in 16%, with no change in the unwanted growth of maize plants. In the production area, the concentration of 12.5 g a.e. ha-1 of glyphosate reduced the lignin content and the other underdoses have not changed this feature in maize plants. None of the underdoses affected the height and biomass produced by the maize plants. The highest underdose tested promoted acceleration in the decomposition of maize stover.

Influence of body mass and environmental oxygen tension on the oxygen consumption rates of an enteropneust, Glossobalanus crozieri

The present study deals with a species of enteropneust, Glossobalanus crozieri, focusing on two aspects of its respiration: a) oxygen consumption and body mass, and b) the influence of environmental oxygen tension on the respiratory rate. Preliminarily, the body water content was shown to be 85% of the whole body weight. The regression coefficient of the oxygen consumption on the wet body mass (0.578) seems to agree with the view that in enteropneusts respiration is mainly cutaneous. The respiratory rate was significantly reduced at O2 tensions from 76 mmHg downwards, suggesting conformity rather than regulation

Eradication of Helicobacter pylori infection in patients with duodenal ulcer and non-ulcer dyspepsia and analysis of one-year reinfection rates

Helicobacter pylori (HP) infection is endemic worldwide. The proposed treatment is expensive and there are few reports regarding reinfection rates in Brazil. The aim of this study was to compare the eradication rates obtained with two therapeutic options and to evaluate reinfection one year after treatment. This was a prospective randomized trial with 55 patients. Thirty-nine patients had active duodenal ulcer (DU) and 16 non-ulcer dyspepsia (NUD), and all tested positive for HP. Diagnosis was based on at least two positive tests: ultrarapid urease test, histology and/or culture. Patients were randomized to two groups: group OMC treated with 40 mg omeprazole (once a day), 500 mg metronidazole and 250 mg clarithromycin (twice daily) for 7 days, or group NA treated with 300 mg nizatidine (once a day) and 1000 mg amoxicillin (twice daily) for 14 days. Those patients in whom HP was eradicated were followed up for one year to evaluate reinfection. Twenty-five patients were randomized for OMC and 30 for NA. HP eradication occurred in 20/25 patients (80%) treated with OMC and 13/30 (43%) treated with NA (P = 0.01). After reallocation because of initial treatment failure, the overall eradication rate was 44/51 patients (86%). After an average follow-up of one year, we evaluated 34 patients (23 with DU and 11 with NUD). Reinfection occurred in 3/34 patients (7.6%). We conclude that OMC is effective for HP eradication, and that NA should not be used. Reinfection occurs in 7.6% of the patients in the first year after eradication.