Performance Assessment of a 3D Hydrodynamic Model Using High Temporal Resolution Measurements in a Shallow Urban Lake

Urban lakes provide many ecosystem services, e.g., flood control, nature protection, coolness island, recreation. Hydrodynamic models will increasingly be used to enhance these benefits. We present the first validation of a three-dimensional (3D) hydrodynamic model on a small shallow lake with high resolution and high frequency measurements. Lake Créteil, France (area 0.4 km², mean depth 4.5 m, and catchment area 1 km²) is a former gravel pit and now part of a regional park. The model Delft3D-FLOW was calibrated on a one-month period, with continuous measurements of temperature at five depths at the center of the lake and at three depths at two other stations, and with current speed profiles at the centre of the lake. The model was then verified on 18 1-month periods with similar temperature measurements. The model reproduced very well the temperature dynamics, including the alternation between mixing and stratification periods and internal wave patterns. The mean absolute errors over the five depths at the central point remained below 0.55^°C in spring and summer, the most favorable seasons for phytoplankton growth. Horizontal temperature differences, which rose up to 3^°C at the beginning of stratification periods, were also well reproduced, as well as current speeds. These results are very promising for assessing nutrient and pollutant diffusion, settling and resuspension, as well as for understanding how phytoplankton blooms start in small shallow lakes.     

Sympatry in grapsoid crabs (genera <Emphasis Type="Italic">Planes</Emphasis> and <Emphasis Type="Italic">Plagusia</Emphasis>) from olive ridley sea turtles (<Emphasis Type="Italic">Lepidochelys olivacea</Emphasis>), with descriptions of crab diets and masticatory structures

Grapsoid crabs of the genera Planes and Plagusia are commonly referred to as “rafting crabs” due to their propensity to live on flotsam and pelagic marine animals. Planes minutus and Planes major (=Planes cyaneus) are epibionts of sea turtles. Occurrences of grapsoid crabs in the genera Planes and Plagusia were evaluated on a total of 27 olive ridley sea turtles, Lepidochelys olivacea, from the eastern tropic Pacific (1998–2001) and the Hawaiian Islands (2002) captured in July–December each year. This is the first report of Planes marinus and Plagusia squamosa on sea turtles, and of P. major, P. marinus, and P. squamosa in sympatry on a confined substrate. Stomach content analyses showed P. major and P. marinus consumed a variety of neuston and marine vegetation, with the former consuming considerably more animal material. Epibiotic P. squamosa consumed mostly plant material. The three Planes species had distinctive differences in gastric mill tooth morphology. The versatile mouthparts of P. marinus are described and resemble those of their congeners. Most female P. major and P. marinus collected were ovigerous and present in all survey months.     

Joining sheet panels to thin-walled tubular profiles by tube end forming

This paper is focused on novel utilizations of the fundamental modes of deformation of tube end forming for assembling sheet panels to thin-walled tubular profiles.The objective is to present an innovative and environmental friendly joining technology built upon the combination of compression beading with tube inversion that can successfully eliminate currently available technologies based on mechanical fixing with fasteners, welding and structural adhesive bonding. The technology works at room temperature, is capable of ensuring significant economic and time savings and offers potential for opening new markets for the assembly of lightweight frame structures.The presentation is supported by experimentation and numerical modelling based on independently determined mechanical properties of the materials with the purpose of characterizing and evaluating the process feasibility limits as a function of the major operative parameters.The feasibility of joining sheet panels to tubular profiles by means of the proposed technology is demonstrated by presenting industrial applications and by evaluating the performance of a safety auto part in an operation failure test.     

Sorption and desorption of diuron on Typic Argiudoll,Oxic Argiudoll and on their clay fractions: environmental aspects

Abstract

The sorption and desorption of diuron by soil samples from Horizons A and B (HA and HB) and by their different clay fractions were investigated, using two soil samples, classified as Typic Argiudoll and Oxic Argiudoll. The sorption and desorption curves were adjusted to the Freundlich model and evaluated by parameters K_f, K_d and K_oc. Based on the data of groundwater ubiquity score (GUS), leachability index (LIX) and hysteresis index (HI), the risk of groundwater pollution was evaluated. The K_d values obtained for soil samples were between 4.5?mL g^?1 (Oxic Argiudoll – HB) and 15.9?mL g^?1 (Typic Argiudoll – HA) and between 1.13 and 14.0?mL g^?1 for the different mineral fractions, whereas the K_oc values varied between 276 (Oxic Argiudoll – HB) and 462 (Typic Argiudoll – HA). According to the parameter GUS, only Oxic Argiudoll – HB presented leaching potential, and based on the LIX index this same soil presented the highest leaching potential. Some samples presented low LIX and GUS values, indicating no leaching potential, but none presented HI results indicative of hysteresis, suggesting weak bonds between diuron and the soil samples and, hence, the risk of groundwater pollution by diuron.     

Evaluation of Cyto- and Genotoxicity of Poly(lactide-co-glycolide) Nanoparticles

This work reports on an analysis of the cyto- and genotoxicity of poly(lactide-co-glycolide) polymer nanoparticles, in an attempt to evaluate their mutagenic effects. Fibroblast (3T3) and human lymphocyte cell cultures were exposed to solutions containing three different concentrations of nanoparticles (5.4, 54 and 540 μg/mL, polymer mass/volume of solution). The nanoparticles were characterized in terms of their hydrodynamic diameters, zeta potentials and polydispersity indices. The morphology of the particles was determined by atomic force microscopy. The PLGA nanospheres presented a size of 95 nm, a zeta potential of −20 mV and a spherical morphology. Cellular viability assays using fibroblast cells showed no significant alterations compared with the negative control. A cytogenetic analysis of human lymphocyte cells showed no significant changes in the mitotic index in relation to the control, indicating that in the concentration range tested, the particles used in the experimental models did not present cyto- or genotoxicity. For the tests conducted in this work we can conclude that biodegradable and biocompatible PLGA nanospheres are not toxic in the cell cultures tested (fibroblast and lymphocyte cells) and in the range of concentrations employed. The results provide new information concerning the toxic effects of particles produced using PLGA.     

Rice straw ash extract, an efficient solvent for regioselective hydrothiolation of alkynes

Environmental Chemistry Letters - Herein, we describe a simple and inexpensive protocol for the hydrothiolation of alkynes. In this context, water extract of rice straw ash (WERSA) has been proven...     

Identification of redundant air quality measurements through the use of principal component analysis

This study aims to show how principal component analysis (PCA) can be used to identify redundant measurements in air quality monitoring networks. The minimum number of air quality monitoring sites in Oporto Metropolitan Area (Oporto-MA) was evaluated using PCA and then compared to the one settled by the legislation. Nine sites, monitoring NO₂, O₃ and PM₁₀, were selected and the air pollutant concentrations were analysed from January 2003 to December 2005. PCA was applied to the data corresponding to the first two years that were divided into annual quarters to verify the persistence of the PCA results. The number of principal components (PCs) was selected by applying two criteria: Kaiser (PCs with eigenvalues greater than 1) and ODV₉₀ (PCs representing at least 90% of the original data variance). Each pollutant was analysed separately. The two criteria led to different results. Using Kaiser criterion for the eight analysed periods, two PCs were selected in: (i) five periods for O₃ and PM₁₀; and (ii) six periods for NO₂. These PCs had important contributions of the same groups of monitoring sites. The percentage of the original data variance contained in the selected PCs using this criterion was always below 90%. Thus, the results obtained using ODV₉₀ were considered with more confidence. Using this criterion, only five monitoring sites for NO₂, three for O₃ and seven for PM₁₀ were needed to characterize the region. The number of monitoring sites for NO₂ and O₃ was in agreement with what was established by the legislation. However, for PM₁₀, Oporto-MA needed two more monitoring sites. To validate PCA results, statistical models were determined to estimate air pollutant concentrations at removed monitoring sites using the concentrations measured at the remaining monitoring sites. These models were applied to a year's data. The good performance obtained by the models showed that the monitoring sites selected by the procedure presented in this study were enough to infer the air pollutant concentrations in the region defined by the initial monitoring sites. Additionally, the air pollutant analysers corresponding to the redundant measurements can be installed in non-monitored regions, allowing the enlargement of the air quality monitoring network.