Using thermal units for estimating critical period of weed competition in off-season maize crop

Brazilian off-season maize production is characterized by low yield due to several factors, such as climate variability and inadequate management practices, specifically weed management. Thus, the goal of this study was to determinate the critical period of weed competition in off-season maize (Zea mays L.) crop using thermal units or growing degree days (GDD) approach to characterize crop growth and development. The study was carried out in experimental area of the University of S?o Paulo, Brazil, with weed control (C), as well as seven coexistence periods, 2, 4, 6, 8, and 12 leaves, flowering, and all crop cycle; fourteen treatments were done. Climate data were obtained from a weather station located close to the experimental area. To determine the critical period for weed control (CPWC) logistic models were fitted to yield data obtained in both W and C, as a function of GDD. For an arbitrary maximum yield loss fixed in 2.5%, the CPWC was found between 301 and 484 GDD (7-8 leaves). Also, when the arbitrary loss yield was fixed in 5 and 10%, the period before interference (PBI) was higher than the critical weed-free period (CWFP), suggesting that the weeds control can be done with only one application, between 144 and 410 GDD and 131 and 444 GDD (3-8 leaves), respectively. The GDD approach to characterize crop growth and development was successfully used to determine the critical period of weeds control in maize sown off-season. Further works will be necessary to better characterize the interaction and complexity of maize sown off-season with weeds. However, these results are encouraging because the possibility of the results to be extrapolated and because the potential of the method on providing important results to researchers, specifically crop modelers.     

Air quality management in Portugal: example of needs and available tools

The Framework Directive (FWD) and the proposed Daughter Directives are the newest legislative instruments concerning a new political strategy and air quality management approach for Europe. Additionally, the member countries of the United Nations Economic Commission for Europe have included the concepts of critical load and level for planning air pollution abatement strategies and as a base of international agreements concerning limitation of the emissions of air pollutants. These concepts imply an accurate knowledge about pollutants deposition fluxes. The paper describes the main needs and the tools available to define a strategy of air quality management in Portugal. Two study cases are presented: (1) extensive monitoring plan to assess the impact of an urban incinerator plant; and (2) contribution to a methodology to estimate critical levels for a coastal region in Portugal. These different approaches allowed illustrating the complexity of the implementation of an air pollution management strategy.     

Learning from Tabasco’s floods by applying MORT

Natural disasters are increasing alarmingly worldwide in recent years. They have killed millions of people, and adversely affected the life of at least one billion people. Given this, natural disasters present a great challenge to society today concerning how they are to be mitigated so as to produce an acceptable risk is a question which has come to the fore in dramatic ways recently. In 2007, the state of Tabasco, Mexico, was flooded and it is believed that al least one million people were left homeless. The paper addresses the following question: what can be learnt from flood disasters? The paper presents some preliminary results of the analysis of the Tabasco’s flooding by applying the Management Oversight Risk Tree (MORT). The MORT technique may be regarded as a structured checklist in the form of a complex ‘fault-tree’ model that is intended to ensure that all aspects of an organization’s management are looked into when assessing the possible causes of an incident. One of the key conclusions of the present analysis is that the approach to decision making in relation ‘flood management’ at the time of the disaster has not been based explicitly on ‘flood risk assessment’. It is hoped that by conducting such analysis lessons can be learnt so that the impact of natural disasters such as the Tabasco’s flooding can be mitigated in the future.     

Assessment of geochemical modeling applications and research hot spots—a year in review

Environmental Geochemistry and Health - Geochemical modeling has been employed in several fields of science and engineering in recent years. This review seeks to provide an overview of case studies...     

An empirical parametrization of internal seiche amplitude including secondary effects

Environmental Fluid Mechanics - An internal wave is a propagating disturbance within a stable density-stratified fluid. The internal seiche amplitude is often estimated through theories that...     

Does temporal and spatial segregation explain the complex population structure of humpback whales on the coast of West Africa?

Humpback whales (Megaptera novaeangliae) in the Southeastern Atlantic Ocean (International Whaling Commission ‘Breeding Stock B’—BSB) are distributed from the Gulf of Guinea to Western South Africa. Genetic data suggest that this stock may be sub-structured, but it remains unknown if this is due to reproductive segregation. This paper evaluates the spatial and temporal population structure of BSB humpback whales using a combination of maternally and bi-parentally inherited markers. The genetic differentiation that we identify in this study could be due to a combination of (1) spatial and/or temporal segregation on breeding grounds in the greater Gulf of Guinea, (2) the possibility of maternally inherited site fidelity to specific feeding grounds and (3) the use of two generalized but exclusive migratory routes (coastal and offshore) between feeding and breeding areas. Further, photo-identification and genetic sampling efforts in other areas of the Sub-Saharan Western Africa winter range and targeted deployment of satellite tags would help to clarify some of the apparent complexity in the population structure of animals biopsied in this region.     

Uranium mining in Portugal: a review of the environmental legacies of the largest mines and environmental and human health impacts

The history of uranium mining in Portugal during almost one century has followed international demand peaks of both radium and uranium, which in turn were driven by medical, military, and civil applications. Nowadays, following price drop in the 1980s, mining activities decreased and ceased in 2001. The current challenge is to deal with environmental legacies left by old uranium mines, mainly located in Viseu and Guarda districts. In 2001, based on several radiological surveys carried out, the Portuguese government assumed the remediation costs of abandoned mine areas for environmental safety and public health protection. Detailed environmental and public health risk assessments were performed under the scope of studies both requested by the government and by funded research projects. It was found that the existing risks, due to radiological and chemical exposures to metals and radionuclide’s, were particularly high at the old milling facilities and mines where in situ and heap leaching of low-grade ore occurred. The different studies, involving both humans and non-human species from different trophic levels, demonstrated the existence of effects at different levels of biological organization (molecular, cellular, tissues, individuals, and populations) and on ecosystem services. To mitigate the risks, the environmental rehabilitation works at the Urgeiriça mine complex are almost complete, while at Cunha Baixa mine, they are presently in progress. These works and environmental improvements achieved and expected are described herein.     

Solvent-free biodiesel epoxidation

Biodiesel emerged again recently as an alternative for fossil fuels. Besides energy, biodiesel can be used as raw material to synthesize high value products such as epoxides. Indeed, epoxides are versatile intermediates in organic synthesis for numerous reactions due to the high reactivity of the oxirane ring. Actually common epoxidation by peracids in organic solvent can last several hours according to the double bonds number. The solvent confers selectivity to the reaction, preventing di-hydroxylation. Alternatively solvent-free reactions can be done in shorter times, but hydroxylation is less controlled. Here, we set up the synthesis of epoxides from methyl and ethyl esters of waste cooking oil, without solvent or metal catalyst. We tested molar ratio of hydrogen peroxide and formic acid, double bond number, reaction time, and temperature. Results show that the highest epoxide yields and selectivity, with high conversion of the double bonds, were obtained for temperature reactions between 50 and 65 °C, reaction times from 2 to 3 h, and molar ratio of 20/2/1. For those conditions, the double bonds conversion is equal or near 100 %, with epoxide yield and selectivity between 85 and 93 %. Organic solvent suppression, besides being environmentally friendly, also saves reaction time and subsequent purification steps.     

Levels of plasma B-esterases and glutathione-S-transferase activities in three South American toad species

We determined the normal levels of butyrylcholinesterase (BChE), carboxylesterase (CbE), and glutathione S-transferases (GST) activities in three South American toad species in order to establish reference values for field pesticide monitoring purposes. Interspecies variations in B-esterase and GST activities were examined according to body mass. In addition, comparative inhibition of BChE and CbE activities using malaoxon, and chemical reactivation of malaoxon-inhibited BChE activity using pyridine-2-aldoxime methochloride (2-PAM) were investigated. Bufo fernandezae had average activity values for BChE: 17.31 mmol min^?1 ml^?1; CbE: 621.49 nmol min^?1 ml^?1 and GST: 1.94 mmol min^?1 ml^?1 while B. arenarum enzymatic average activities were BChE: 9.51 mmol min^?1 ml^?1; CbE: 270.07 nmol min^?1 ml^?1, and GST: 1.59 mmol min^?1 ml^?1; finally Bufo schneideri had enzymatic mean values of BChE: 2.08 mmol min^?1 ml^?1; CbE: 301.95 nmol min^?1 ml^?1, and GST: 1.60 mmol min^?1 ml^?1. Moreover, we found an allometric relationship between plasma BChE and CbE activities and body size for the three toad species. We suggest that B. fernandezae would be the species with a higher tolerance capacity to organophosphorous insecticides compared to the other toad species, while B. schneideri may be the most vulnerable toad species to field pesticide exposure, although some other factors (e.g., brain AChE sensitivity or pesticide metabolism by phosphotriesterases) should be also taken into account. The malaoxon-inhibited BChE activity of the three toad species was reactivated in the presence of 2-PAM, and it is recommended as a specific and sensitive methodology in the assessment of field exposure to OP insecticides together to compare BChE activity levels between OP-exposed and nonexposed individuals.