On the relationships between bioassays and dynamics in chemically stressed, aquatic population models

One purpose of this article is to synthesize some recent results on the dynamics of mathematical models of chemically stressed aquatic populations and communities; in particular, we (1) illustrate some of the difficulties that might arise from extrapolation of bioassay results to dynamic, chemically stressed population and community models; and (2) indicate different ways in which chemicals can affect the dynamics of population models. Bioassays, an important component of ecological impact and risk assessment, can be misleading if extrapolated to settings beyond experimental boundaries. Extrapolation of bioassays to the populations and community levels can not be direct because derived information is usually specific for a subset of individuals and obtained under experimental constraints on time and parameters. We present examples derived from a mathematical setting where consequences of bioassays, even when employed as the fundamental determinant of stress in the systeni, have no predictable relationship to the ultimate effect of the chemical on the system. The first illustration, at the population level, demonstrates that sublethal effects of a lipophilic chemical with a reversible mode of action on individuals attained at concentrations well below the LC50, indeed even below the EC50 for growth, can drive the population to extinction so that the chemically stressed population is much more severely damaged than predicted by hioassays. The second illustration at the community level indicates that results of bioassays can also indicate outcomes that (ire worse than actually occurs for the community. Finally, we compare the outcome of a spectral analysis of time series of a sequence of chemically stressed populations, demonstrating that complex effects of lipophilic chemicals on population dynamics are not readily identifiahle from spectral signatures

ELECTRO-OSMOTIC DEWATERING OF SEWAGE SLUDGE: PRELIMINARY RESULTS

About half of the organic pollution load treated by the activated sludge process is oxidised and converted into water and carbon dioxide, while the remaining is converted into biomass, called “excess biological sludge” or “waste sludge”. At present, this technique is the cheapest way to remove colloidal and soluble organic pollutants from sewage, but it produces a huge amount of liquid waste sludge, with a dry solid (DS) content of less than 2%, rich in organic substances, mostly biodegradable. Therefore, it needs further processes to reduce its volume, by reducing its water content, and to reduce its polluting potential, due to its high content of biodegradable organic matter. However, sludge produced by Wastewater Treatment Plants (WWTPs) usually has a poor dewaterability. Industrially, mechanical dewatering is the method employed to increase the dry solids (DS) of sewage sludge. The aim of dewatering is the decrease of transport and disposal costs, but the efficiency of the mechanical dehydration methods is low. Electro-osmosis could be a suitable technique to reduce water content of the final sludge by the application of an electric field. Studies about electro-dewatering reported that the DS could increase to values around 40-45%, with respect to 25-30% obtained by mechanical methods, such as centrifuge, filter press and belt press. Aim Here, we investigated the parameters affecting pressure-driven electro-dewatering, with a static and a dynamic device, starting from types of sludge mechanically pre-dehydrated. We focused on the optimization of operating conditions to achieve the best results in terms of solids percentage at the minimum energy consumption. Methods Experiments have been performed by means of a lab-scale device able to produce both a mechanical pressure and an electric field. The use of both these systems could be efficient to increase the amount of dry solids in the final sludge. This device, as illustrated in Figure 1, consists of: • Cylindrical glass vessel (h=176 mm, Ø=80 mm) • Cooling water-jacket • Compressed air system (1-4.5 bar) • Double effect cylinder (200 mm stroke) SMC-CP96 (piston) • DC power supply (30 V-5 A) • Anode: DSA Ti (MMO), fixed to the piston • Cathode: stainless steel mesh (AISI 304) • Cloth: PTT (polytrimethyleneterephthalate) Figure 1-Equipment schematic of electro-dewatering device. Main Results The applied voltage has been set at 10 V, 15 V and 20 V and pressures at 3 bar. The results confirmed values of final DS around 40%. Initial DS and sludge conductivity, together with the applied electric field, are the key factors of electro-osmosis tests. The rotating piston highlighted that a mixing of sludge during the potential application could slightly increase the sludge conductivity, but cakes must be kept under 1.5 cm of thickness in order to achieve a good dewatering. In conclusion, in this paper we assess the feasibility of the electro-osmosis dewatering. It is a promising technique to remove water from sewage sludge, since it is able to increase DS of 15% on average with respect industrial mechanical dewatering. Moreover, this work proved that the treatment of a high DS cake is more difficult than a non-dewatered sludge due to a lower conductivity during the process

Phosphorus recovery from a pilot-scale grate furnace: influencing factors beyond wet chemical leaching conditions

Phosphorus is a non-renewable resource going to exhaustion in the future. Sewage sludge ash is a promising secondary raw material due to its high phosphorus content. In this work, the distribution of 19 elements in bottom and cyclone ashes from pilot-scale grate furnace have been monitored to determine the suitability for the phosphorus acid extraction. Moreover, the influence of some parameters beyond wet chemical leaching conditions were investigated. Experimental results showed that bottom ash presented lower contamination in comparison to cyclone ash and low co-dissolution of heavy metals (especially Cr, Pb and Ni), while high phosphorus extraction efficiencies (76-86%) were achieved. High Al content in the bottom ash (9.4%) negatively affected the phosphorus extraction efficiency as well as loss on ignition, while the particle size reduction was necessary for ensuring a suitable contact surface. The typology of precipitating agents did not strongly affect the phosphorus precipitation, while pH was the key parameter. At pH 3.5-5, phosphorus precipitation efficiencies higher than 90% were achieved, with a mean phosphorus content in the recovered material equal to 16-17%, comparable to commercial fertilizers. Instead, the co-precipitation of Fe and Al had a detrimental effect on the recovered material, indicating the need for additional treatments

Análisis de la dinámica de una comunidad planctónica mediante un modelo matemático

Modelos matemáticos de variada complejidad han sido usados para explorar la estructura de la comunidad en los ecosistemas acuáticos, y no sólo como herramientas para explorar y revelar mecanismos, tanto intuitivos como contraintuitivos, y patrones (de comportamiento, sino también para orientar lineas de especulación teórica y sugerir direcciones para la investigación de carpo y de laboratorio. El ecosistema que nos interesa aquí es el sistema planctónico oceánico dominado por algas Phaeocystis spp. El modelo matemático incluye compartimentos de nutrientes, fitoplancton y zooplancton (consumidores y depredadores) y está estructurado en forma modular para analizar el impacto de distintos factores en la compleja dinámica del sistema. Los resultados de las simulaciones destacan la importancia de (1) la estructura de tamaños de la población colonial de Phaeocystis, (2) el impacto de la naturaleza de la respuesta funcional del microzooplacton a la abundancia de fitoplancton y (3) la temporalidad de la aparición de depredadores en la comunidad sobre la utilización de los nutrientes. Se explora también el efecto de la turbulencia en la ruptura de las colonias y de la incorporación de nutrientes por remineralización o descarga de ríos. Las simulaciones indican que el sistema depende fuertemente del balance de tasas de crecimiento y de remoción en las poblaciones de Phaeocystis y microzooplancton durante los días iniciales del florecimiento, con los nutrientes y los depredadores actuando como controles indirectos.Mathematical models of various degrees of complexity have been successfully used for the study of aquatic ecosystems, primarily for the exploration of community structure, not only as tools for revealing counterintuitive mechanisms and patterns, but also for orienting theoretical speculation and suggesting directions of field and lahoratory research. Here we are interested in the oceanic planktonic system dominated by the unicellular algae Phaeocystis spp. Our mathematical model includes nutrient phytoplankton and zooplankton (grazers and predators) compartments and is constructed for modular form in order to analyse the impact of different factors in the complex dynamics of the system. Simulation results show the importance of size structure in the colonial Phaeocystis population, as well as the impact the character of the functional response of microzooplankton to algal abundance and the timing of large grazers in the community have on nutrient consumption. The effects of colonial cleavage caused by shear and the inflow of nutrients caused by remineralization or discharge of rivers llave also been explored. The results of our simulations indicate that the system has a strong dependence on the balance hetween growth rates and removal rates in both Phaeocystis and microzooplankton populations, nutrients and predators playing the role of indirect controls

Giant Aneurysm of the Extracranial Carotid Artery: Case Report

AbstractWe report a case of giant extracranial carotid aneurysm treated by carotid aneurysmectomy. A 70-year-old female was referred with a palpable swelling on left lateral region of the neck, associated with dizziness and dysarthria. Spiral-CT scan showed a 5-cm aneurysm of the internal carotid artery (ICA), kinking of ICA and increased flow in the right vertebral artery. Angiography showed, a fusiform ICA aneurysm, with lengthening and tortuosity of intracranial vessels. An aneurysmectomy was performed with end-to-end repair of ICA. The patient was discharged on the 12 post-operative day. Twelve months after the operation, the patient showed a complete recovery from the neurological deficit and patency of ICA. We recommend surgical treatment in order to avoid rupture, thromboembolism and cerebrovascular insufficiency

Aplicación de un modelo de red neuronal para la clasificación de sistemas lacunares pampeanos

The pampean shallow lakes present different distributions in their trophic chains, the latter being cause and consequence of the state of the lacunar systems. In order to determine how each of the measured variables —climatic, edaphic, morphometric, physicochemical and biological— in contributes to the general state of the lake, an Artificial Neural Network (ANN) model is built. The ANN is capable of processing a large number of variables and returning a classification that will allow determining it’s the trophic state. The information from satellite images is one of the input variables. Hence, on a first stage, the construction of a ANN model is intended to obtain a weight for each one of the visible specter bands and near infrared bands from LANDSAT and to pick the most representative value that the image returns. This value will be used as input to the ANN that will be then trained to return a classification of the shallow lakes according to the three observed patterns in the relation between phytoplankton, zooplankton, fish and their link with to nutrient abundance and watershed management.Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Instituto de Limnología "Dr. Raul A. Ringuelet" (ILPLA

Study of Visitors to North Carolina Wineries

The wine and grape industry generates a significant economic impact in North Carolina’s rural communities. In 2009 the wine and grape industry generated 7,600 jobs and $1.2 billion in total annual economic impact in the state. Particularly noteworthy is the fact that NC’s wine tourism revenue grew 27$156 million in wine tourism revenue

World Climate Research Program Special Workshop on Climatic Effects of ozone depletion in the southern hemisphere: assessing the evidence and identifying gaps in the current knowledge

A World Climate Research Programme (WCRP) Special Workshop titled the “Climatic effects of ozone depletion in the Southern Hemisphere: Assessing the evidence and identifying gaps in the current knowledge” focused on the current understanding of Southern Hemisphere (SH) ozone depletion, in particular high-latitude ozone depletion, with regards to its impacts on hemispheric climate and its role relative to greenhouse gas (GHG)–induced climate changes. The 2010 United Nations Environment Programme (UNEP)/World Meteorological Organization (WMO) Scientific Assessment of Ozone Depletion, and research published since, provided the starting point for discussion. The workshop was supported by WCRP, the National Science Foundation (NSF; United States), the National Aeronautics and Space Administration (NASA; United States), Agencia Nacional de Promoción Científica y Técnica (Argentina), and the Pontificia Universidad Católica Argentina (Argentina).Fil: Canziani, Pablo Osvaldo. Pontificia Universidad Católica Argentina ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Oneill, Alan. National Centre For Earth Observations; Reino UnidoFil: Schofield, R.. University of Melbourne; AustraliaFil: Raphael, M.. University of California at Los Angeles; Estados UnidosFil: Marshall,G. J.. British Antarctic Survey; Reino UnidoFil: Redaelli, G.. Universita degli Studi dell'Aquila; Itali

Nova cultivar de amendoim para as condições do nordeste brasileiro.

A BRS 151 L-7 é uma nova cultivar de amendoim, de sementes de coloração vermelha, de forma oblonga, desenvolvida pela Embrapa-Centro Nacional de Pesquisa de Algodão (CNPA), e destinada ao consumo in natura e à indústria de alimentos. A cultivar é de porte ereto, resultante do cruzamento entre a cultivar produtiva IAC-Tupã (tipo Valência) e a cultivar Senegal 55-437 (tipo Spanish), de ciclo curto. Em ensaios regionais realizados em 27 municípios de quatro estados da Região Nordeste, a cultivar apresentou grande potencial para produtividade de sementes, ciclo vegetativo de 87 dias, tolerância ao estresse hídrico, e grande adaptação ao cultivo em clima semi-árido. Sua produtividade média de vagens em condições experimentais é de 1.850 kg ha-1 em cultivo de sequeiro, e 4.500 kg ha-1 em condições irrigadas, o que corresponde a uma elevação na ordem de 12% e 38%, respectivamente, com relação à produtividade da cultivar tradicional Tatu. No aspecto nutricional, a cultivar BRS 151 L-7 tem baixo teor de óleo (46%), e sua farinha desengordurada contém 55% de proteína; entre os aminoácidos essenciais, é limitante apenas no teor de lisina, em comparação com o padrão da FAO/85