A laboratory study on the MSW mechanical behavior in triaxial apparatus

Shear strength characterization of MSW materials is a mandatory task when performing analyses related to landfill design and landfill geometry improvements. Despite the considerable amount of research focusing on MSW mechanical behavior there remain certain aspects which are not completely understood and deserve attention in particular the case of the undrained behavior of MSW. This paper presents the results of a comprehensive laboratory testing program using a large-scale triaxial apparatus at the Federal University of Bahia, Salvador, Brazil. The effect of factors such as confining pressure, unit weight, fiber content, rate of loading and over-consolidation on the MSW mechanical response were investigated. Tested samples presented typical MSW shear/strain curves (concave upward) in all the tests, despite the pore water pressure reaching levels almost equal to the confining pressure. The obtained results show that increasing confining stress, unit weight, loading rate, fiber content and over-consolidation lead to an increase in the MSW shear strength. The importance of the fibrous components in the waste behavior is highlighted and graphs showing the variation of the MSW shear strength with fiber content in different drainage conditions are shown. The authors believe these results could be of interest to many companies, especially considering the new trend of plastic material recycling (prior landfilling) for energy recovery purposes.     

Fumaric acid production using renewable resources from biodiesel and cane sugar production processes

The microbial production of fumaric acid by Rhizopus arrhizus NRRL 2582 has been evaluated using soybean cake from biodiesel production processes and very high polarity (VHP) sugar from sugarcane mills. Soybean cake was converted into a nutrient-rich hydrolysate via a two-stage bioprocess involving crude enzyme production via solid state fermentations (SSF) of either Aspergillus oryzae or R. arrhizus cultivated on soybean cake followed by enzymatic hydrolysis of soybean cake. The soybean cake hydrolysate produced using crude enzymes derived via SSF of R. arrhizus was supplemented with VHP sugar and evaluated using different initial free amino nitrogen (FAN) concentrations (100, 200, and 400 mg/L) in fed-batch cultures for fumaric acid production. The highest fumaric acid concentration (27.3 g/L) and yield (0.7 g/g of total consumed sugars) were achieved when the initial FAN concentration was 200 mg/L. The combination of VHP sugar with soybean cake hydrolysate derived from crude enzymes produced by SSF of A. oryzae at 200 mg/L initial FAN concentration led to the production of 40 g/L fumaric acid with a yield of 0.86 g/g of total consumed sugars. The utilization of sugarcane molasses led to low fumaric acid production by R. arrhizus, probably due to the presence of various minerals and phenolic compounds. The promising results achieved through the valorization of VHP sugar and soybean cake suggest that a focused study on molasses pretreatment could lead to enhanced fumaric acid production.     

Identifying opportunities for long-lasting habitat conservation and restoration in Hawaii’s shifting climate

Conservation efforts in isolated archipelagos such as Hawaii often focus on habitat-based conservation and restoration efforts that benefit multiple species. Unfortunately, identifying locations where such efforts are safer from climatic shifts is still challenging. We aimed to provide a method to approximate these potential habitat shifts for similar data- and research-limited contexts. We modeled the relationship between climate and the potential distribution of native biomes across the Hawaiian archipelago to provide a first approximation of potential native biome shifts under end-of-century projected climate. Our correlative model circumvents the lack of data necessary for the parameterization of mechanistic vegetation models in isolated and data-poor islands. We identified locations consistently expected to remain the same in terms of the native biome compatibility by the end of the century with a robust evaluation of sources of uncertainty in our projections. Our results show that, despite large differences in climate projections considered, 35% of the areas considered are consistently projected to maintain their current compatibility to native biomes. By integrating our native biome compatibility projections with maps of current actual cover, we identified areas ideal for long-term habitat conservation and restoration. Our modeling approach can be used with relatively simple data; offers multiple forms of projection confidence estimates, model calibration, and variable selection routines; and is compatible with ensemble projections. This method is not only applicable to potential native cover, as done in this study, but to any set of vegetation classes that are related to environmental predictors available for modeling.     

Integrated farming systems for improving soil carbon balance in the southern Amazon of Brazil

Regional Environmental Change - Integrated farming systems (IS) are one of the main strategies of the Brazilian government to reduce or compensate for carbon emissions from agriculture with...     

Carbon-optimised land management strategies for southern Amazonia

Regional Environmental Change -     

Evaluation of genotoxic effects of benzene and its derivatives in workers of gas stations

The search for reliable biomarkers of human exposure to benzene and its derivatives is still subject of research. Many of the proposed biomarkers have limitations ranging from the low sensitivity to the wide variability of results. Thus, the aim of our study was to assess the frequencies of chromosomal abnormalities (CA) and sister chromatid exchanges (SCE) in workers of gas stations, with (cases, n?=?19) and without (local controls, n?=?6) risk of exposure to benzene and its derivatives, comparing them with the results from the general population (external controls, n?=?38). The blood dosages of benzene, toluene, and xylenes were measured in all participants. Blood solvent levels were compared with the findings obtained in cytogenetic evaluation and a research protocol which included data of the workplace, lifestyle, and health of the individuals. We did not detect the presence of benzene and its derivatives and did not find chromosomal damage that may be associated with the gas station activity in cases. Moreover, although we found an association of increased SCE and the working time in the local controls, the values found for SCE are within normal limits. Thus, our evaluation of SCE and CA reflected the levels of benzene and its derivatives observed in the blood. We believe, therefore, that SCE and CA may actually constitute possible tests for the evaluation of these exposures. However, we believe that further studies, including individuals at risk, are important to confirm this assertion.     

Distribution of polycyclic aromatic hydrocarbons in marine sediments and their potential toxic effects

The presence of polycyclic aromatic hydrocarbons (PAHs) in samples of marine sediments from Paranagua Bay on the southern coast of Brazil was investigated. Paranagua Bay is the location of a major port, one of the busiest in Brazil. The region has a great potential for tourism and port-related industries and activities. Due to its characteristics as a venue for tourism, two major campaigns were planned: one 3 months before the summer (between December and February) and a second after the vacation season. Total concentration of PAHs in sediments ranged from 26.33 to 406.76 ng/g (in both campaigns). The highest values were found in sediments with higher organic carbon content. We found no substantial differences between the two campaigns, and the values are quite similar. Ternary diagrams show that points P5 and P6 were considered polluted, while others were classified as non-polluted. Molecular ratios indicate that the main sources of PAHs are petrogenic and the burning of fossil fuels. Sediment toxicity was assessed by the presence of PAHs in terms of benzo(a)pyrene (BaP) concentration. The toxicity of PAHs mixtures can be characterized more accurately by developing and establishing toxic equivalency factors (TEFs) for PAHs. Considering TEFs, the BaP_eq concentrations vary between 0.264 and 5.922 ng/g (considering both campaigns). Thus, two points are above the maximum level recommended (3 ng/g) by the Netherlands sediment quality guidelines. In fact, sites P5 and P6 apparently are exposed to a greater number of pollution sources, thus reflecting the higher concentration of PAHs compounds in sediments.     

Role of carbonyls and aromatics in the formation of tropospheric ozone in Rio de Janeiro,Brazil

The ozone in Rio de Janeiro has been in violation of national air quality standards. Among all of the monitoring stations, the Bangu neighbourhood has the most violations of the national standard of 160 μg m^?3 for the years 2012 and 2013. This study evaluated the reactivity of the carbonyls and aromatics in the tropospheric ozone formation processes. The samples were collected between July and October of 2013. Carbonyls were sampled using SiO₂ cartridges coated with C₁₈ and impregnated with 2,4-dinitrophenylhydrazine and were analysed by HPLC. Activated carbon cartridges and GC/MS were used to measure the concentration of monoaromatic hydrocarbons. An air quality monitoring station provided the concentrations of the criteria pollutants and the meteorological parameters. Cluster analysis and a Pearson correlation matrix were used to determine the formation of groups and the correlation of the variables. The evaluation of the volatile organic compounds (VOC) reaction with OH radicals and the MIR scale was used to extrapolate the reactivity of VOCs to the ozone formation. The average concentrations obtained were 19.7 and 51.9 μg m^?3 for formaldehyde and acetaldehyde, respectively. The mean concentrations obtained for aromatics were 1.5, 6.7, 1.5, 2.6 and 1.6 μg m^?3 for benzene, toluene, ethyl benzene, m+p-xylene and o-xylene, respectively. The cluster analysis indicated the presence of three similar groups, with one formed by gaseous criteria pollutants, another formed by the meteorological parameters, ozone and fine particles, and the last group formed by the aromatics. For the two reactivity scales evaluated, acetaldehyde and toluene were the main ozone precursors.     

Forest environmental investments and implications for climate change mitigation

Forest environmental conditions are affected by climate change, but investments in forest environmental quality can be used as part of the climate change mitigation strategy. A key question involving the potential use of forests to store more carbon as part of climate change mitigation is the impact of forest investments on the timing and quantity of forest volumes that affect carbon storage. Using an economic optimization model, we project levels of U.S. forest volumes as indicators of carbon storage for a wide range of private forest investment scenarios. Results show that economic opportunities exist to further intensify timber management on some hectares and reduce the average timber rotation length such that the national volume of standing timber stocks could be reduced relative to projections reflecting historical trends. The national amount of timber volume is projected to increase over the next 50 yr, but then is projected to decline if private owners follow an economic optimization path, such as with more forest type conversions and shorter timber rotations. With perfect foresight, future forest investments can affect current timber harvest levels, with intertemporal linkages based on adjustments through markets. Forest investments that boost regenerated timber yields per hectare would act to enhance ecosystem services (e.g., forest carbon storage) if they are related to the rate of growth and extent of growing stock inventory.