Hierarchical linear mixed models in multi-stage sampling soil studies

The issue of variances of different soil variables prevailing at different sampling scales is addressed. This topic is relevant for soil science, agronomy and landscape ecology. In multi-stage sampling there are randomness components in each stage of sampling which can be taken into account by introducing random effects in analysis through the use of hierarchical linear mixed models (HLMM). Due to the nested sampling scheme, there are several hierarchical sub-models. The selection of the best model can be carried out through likelihood ratio tests (LRTs) or Wald tests, which are asymptotically equivalent under standard conditions. However, when the comparison leads to a restricted hypothesis of variance components, standard conditions are not maintained, which leads to more elaborated versions of LRTs. These versions are not disseminated among environmental scientists. The present study shows the modeling of soil data from a sampling where sites, fields within sites, transects within fields, and sampling points within transects were selected in order to take samples from different vegetation types (open and shade). For soil data, several sub-models were compared using Wald tests, classic LRTs and adjusted LRTs where the distribution of the test statistic under the null hypothesis is the Chi-square mixture of Chi-square distributions. The inclusion of random effects via HLMM and suggested by the latest version of LRT allowed us to detect effects of vegetation type on soil properties that were not detected under a classical ANOVA.     

Remediation of acid mine drainage

Environmental Chemistry Letters - Acid mine drainage induced by the mining industry causes environmental and economic issues. Acid mine drainage contains mainly metals such as Fe, Al, Cu, Ca, Mg,...     

Catalytic upgrading of higher 1-alkenes from polyethylene thermal cracking by modified Wacker oxidation

The economic success of feedstock recycling procedures for plastic wastes is increasingly demanding the conversion of the starting residue into more valuable chemicals. Thermal cracking of polyethylenes leads to the preparation of equimolar mixtures of n-paraffins and 1-alkenes within the C₂–C₁₀₀ range. These 1-olefins can be catalytically upgraded by selective oxidation processes to more valuable products (e.g., ketones and fatty acids) with different uses such as polar waxes, cetane improvers, varnishes, and printer inks. The results obtained on oxidation in a modified Wacker system of a model 1-olefin (1-dodecene) as well as of a distillate cut (C₁₀–C₂₅) of the product from the thermal cracking of urban polyethylene waste are described.     

Design and Application of Nucleic Acid Standards for Quantitative Detection of Enteric Viruses by Real-Time PCR

Synthetic multiple-target RNA and DNA oligonucleotides were constructed for use as quantification standards for nucleic acid amplification assays for human norovirus genogroup I and II, hepatitis E virus, murine norovirus, human adenovirus, porcine adenovirus and bovine polyomavirus. This approach overcomes the problems related to the difficulty of obtaining practical quantities of viral RNA and DNA from these viruses. The quantification capacity of assays using the standards was excellent in each case (R ² > 0.998 and PCR efficiency > 0.89). The copy numbers of the standards were equivalent to the genome equivalents of representative viruses (murine norovirus and human adenovirus), ensuring an accurate determination of virus presence. The availability of these standards should facilitate the implementation of nucleic acid amplification-based methods for quantitative virus detection.     

Ranging patterns of bottlenose dolphins living in oceanic waters: implications for population structure

Very little is known about the ecology of common bottlenose dolphins (Tursiops truncatus) living in oceanic waters. This study investigated the ranging and residence patterns of bottlenose dolphins occurring in the Azores (Portugal), the most isolated archipelago in the North Atlantic. Data were collected during standardized boat-based surveys conducted over a 6-year period in an area of approximately 5,400 km² (main study area). To investigate the extent of movements of individual animals, non-systematic surveys were also conducted outside this area. Only 44 individuals out of 966 identified were frequently sighted within and between years. The remaining individuals were either temporary migrants from within or outside the archipelago, or transients. Resident dolphins showed strong geographic fidelity to the area. Long-distance movements (of almost 300 km), consistent with foraging or exploratory trips, were observed among non-resident dolphins. Home range size was estimated for 31 individuals sighted ≥10 times. Range areas of these dolphins varied in size and location, but considerable overlap was observed in the areas used, suggesting the absence of habitat partitioning between resident and non-resident dolphins. Estimates of home range size of bottlenose dolphins in the Azores were found to be considerably larger than those previously reported for this species. It is hypothesized that dolphins living in the Azores carry out extensive movements and have large home ranges in response to the lower density and patchy distribution of prey compared to other areas. The extensive ranging behaviour and the lack of territoriality provide an opportunity for interbreeding between dolphins associated with different islands, thus preventing genetic differentiation within the population of the Azores.     

Land cover along hiking trails in a nature tourism destination: the Azores as a case study

Environment, Development and Sustainability - Tourists have become increasingly interested in certain aspects of their destination, including landscape and biodiversity elements, thereby promoting...     

Integrated hydro- and wind power generation: a game changer towards environmental flow in the Sub-middle and Lower São Francisco River Basin?

Many renewable resources for the generation of electricity, such as hydropower and wind power, are dependent on climatic factors. Reservoirs have been created to overcome the stochastic nature of river flows and to make water supply more reliable. However, reservoirs are affecting the ecological status of river ecosystems, e.g., by modifying the flow regime, triggering discussions regarding the discharge of reservoirs. In Brazil’s northeast region, the installed capacity for wind power generation has increased substantially in recent years. Setting up a modeling system for simulating wind power and hydropower generation in this study, it is analyzed whether wind power generation, peaking in the dry season, can help to achieve a more environmentally oriented flow regime in the Sub-middle and Lower São Francisco River Basin. Simulated higher discharges from reservoirs during the rainy season and lower discharges during the dry season, representing a more natural flow regime, will reduce hydropower generation in the dry season. Under recent conditions, the resulting gap in electricity generation can only be partially covered by wind power. A large share needs to be generated by thermal power plants or be imported from other regions in Brazil. The planned future increase in installed wind power capacity can change this picture; the demand for electricity generated by thermal power plants and imported will decrease. Adopting an integrated approach for hydropower and wind power generation, the flow regime in the Sub-middle and Lower São Francisco River Basin can be modified to improve the ecological status of the river system.     

Sorption mechanism of enrofloxacin on humic acids extracted from Brazilian soils

Veterinary antimicrobials are emerging environmental contaminants of concern. In this study, the sorption of enrofloxacin (ENR) onto humic acids (HAs) extracted from three Brazilian soils was evaluated. HAs were characterized by elemental analysis and solid ¹³C nuclear magnetic resonance spectroscopy. The sorption of ENR onto HAs was at least 20-fold higher than onto the soils from which they were separated. Ionic and cation bridging are the primary interactions involved. The interactions driven by cation exchange are predominant on HAs, which appear to have abundant carboxylic groups and a relatively high proportion of H-bond donor moieties with carbohydrate-like structures. Interactions explained by cation bridging and/or surface complexation on HAs are facilitated by moieties containing conjugated ligands, significant content of oxygen-containing functional groups, such as phenolic-OH or lignin-like structures. HAs containing electron-donating phenolic moieties and carboxylic acid ligand groups exhibit a sorption mechanism that is primarily driven by strong metal binding, favoring the formation of ternary complexes between functional groups of the organic matter and drugs.     

Perceptions regarding the challenges and constraints faced by smallholder farmers of vanilla in Mexico

Mexico was the main vanilla producer worldwide many years ago. However, it currently provides just around 5 % of the global production. The issues that have led to the current stagnation of the vanilla production in Mexico have been addressed from various perspectives, but few studies have included the opinion of smallholder farmers. For this reason, the aim of this study was to conduct a participatory diagnostic to identify the challenges and constraints that affect the vanilla productive sector in Mexico from the smallholder farmers perspective. This study was conducted under the of Participatory Rural Appraisal (PRA) approach; consequently, we used PRA techniques for data collection. The qualitative data obtained were transcribed and analyzed using the Content Analysis Method (CAM) and Constant Comparative Method (CCM). The results showed that most of the challenges and limitations referred to by smallholder farmers result from the lack of training to improve production, processing, and marketing. Likewise, various restrictive aspects were identified in the production process that affect crop productivity, such as cultivation in small parcels, high incidence of diseases, premature abortion of fruits, and low tolerance of plants to stress. An aspect common to all processes is the need to promote organization and training schemes, since under the conditions described for the vanilla production chain in Mexico, relationships have been built in highly competitive communities and, in general, the targets seek have been mutually exclusive. For the above, we consider that achieving more profitable and sustainable production schemes require placing smallholder farmers at the base of an inclusive production system supported by fair trade, with organization, institutions, technology transfer, level of trust, and cooperation as core elements.     

Mesozooplankton assemblages and their relationship with environmental variables: a study case in a disturbed bay (Beagle Channel,Argentina)

This study focused on the seasonal and spatial analysis of the mesozooplankton community in a human-impacted subantarctic bay in Argentina and aimed to detect assemblages associated with environmental variability. Mesozooplankton samples and environmental data were obtained in the Ushuaia Bay (UB) seasonally, from August 2004 to June 2005, and spatially, from coastal (more polluted), middle (less influenced) and open sea water (free polluted) sampling stations. Remarkable seasonal changes on the mesozooplankton community were observed. Nitrogenated nutrients, chlorophyll a, salinity and temperature were the prevailing environmental conditions likely associated with the different mesozooplankton assemblages found in the bay. The copepods Eurytemora americana, Acartia tonsa, Podon leuckarti and Nematoda were particularly observed on the northwest coast of the bay, characterized by the highest level of urban pollution, eutrophicated by sewage and freshwater inputs from the Encerrada Bay which is connected to it. The stations situated in the northeast area, mostly influenced by freshwater input from rivers and glacier melting, showed low mesozooplankton abundances and an important contribution of adventitious plankton. The copepods Ctenocalanus citer, Clausocalanus brevipes and Drepanopus forcipatus were mostly observed at the stations located near the Beagle Channel, characterized by open sea and free polluted waters. Our findings suggest that the variations observed in the mesozooplankton assemblages in the UB seem to be modulated by environmental variables associated with the anthropogenic influence, clearly detected on the coast of the bay. Certain opportunistic species such as A. tonsa and E. americana could be postulated as potential bioindicators of water quality in subantarctic coastal ecosystems.