Dos relatos, un análisis y un excurso sobre las identidades y la relación con la ciudad entre los “moradores de la calle” en Temuco, Chile

El autor describe dos casos de personas que viven en la calle en la ciudad de Temuco, en el centro sur de Chile. A partir de una perspectiva etnográfica indaga en algunos de sus modos de acción e interacción en la ciudad, mostrando la lógica de sus actos y la forma en que éstos hacen parte de complejos y fragmentados procesos de configuración identitaria. Asimismo, el autor desarrolla un análisis que estimula el extrañamiento y cuestiona algunos supuestos y conceptos socialmente dados por garantizados respecto de la relación entre los “moradores de la calle” y la ciudad. En este marco, defi ende la tesis según la cual la sobrevivencia es un proceso totalizador que trasciende la esfera biológica para articular un estilo de vida en la que el yo y la ciudad son objetos resignifi cados en función de una serie de experiencias límite a través de las cuales podemos aprender más de nuestro propio mundo

An in situ intercomparison exercise on passive samplers for the monitoring of metals, polycyclic aromatic hydrocarbons and pesticides in surface water

An intercomparison exercise on passive samplers (PSs) was organized in summer 2010 for the measurement of selected metals, polycyclic aromatic hydrocarbons (PAHs) and pesticides in surface waters. Various PSs were used and compared at 2 rivers sites and one marine lagoon. A total of 24 laboratories participated. We present selected significant outputs from this exercise, including discussion on quality assurance and quality control for PSs, the interlaboratory variability of field blanks, time weighted average water concentrations and its uncertainties, the representativity of DGT samples, the ability of PSs to lower limits of detection, PAH fingerprints in various PSs compared with spot samples, and the relevance of the permeability reference compounds (PRC) approach for POCIS with pesticides. These in situ intercomparison exercises should enable to progress on the harmonization of practices for the use of passive sampling, especially for priority chemical monitoring and regulatory programs in compliance with the Water Framework Directive (WFD) and Marine Strategy Framework Directive (MSFD)

Estimation in situ de la variabilité temporelle associée à la concentration obtenue avec les stratégies d'échantillonnage actif et passif

International audienceIn the context of the water framework directive, in order to evaluate the aquatic environment quality for organic and mineral micropollutants, Water Agencies proceed to regular monitoring by collecting spot water sampling. There are some questions about the spatial and temporal representativeness of this “active” sampling technique carried out 6 to 12 times a year. As highlighted by Ort et al. (2010), the uncertainty associated to the sampling step increases when the discrete water sampling frequency decreases. Furthermore, the total uncertainty of spot sampling generally take into account only the contribution of the analytical step, and not the contribution of the sampling step. Thereby, this approach is often insufficient for a reliable contamination level assessment, particularly in the case of fleeting events (floods, punctual discharges…). Alternatively, passive sampling techniques consist to the immersion of a device in the aquatic environment over a period (from several days to a few weeks), providing time-weighted average pollutants concentrations. In this case, the measurements obtained with this device take into account the uncertainty associated with the preparation and analysis step, and the sampling step unlike the classical approach (Allan et al. 2006). Thus, the aim of this work is to determine and compare, in situ, the temporal uncertainty between active and passive sampling techniques. Three different kinds of POCIS (HLB, MAX and MIP) were exposed in triplicate during 6 periods of 14 days spread over 2016 in the Jalle de Blanquefort river (Gironde, France). In parallel, two different types of “active” sampling were carried out: weekly grab and high frequency composite samplings. These different techniques were used to detect and quantify a panel of 38 neutral pesticides (POCIS-HLB), 19 anionic pesticides (POCIS-MAX), glyphosate and AMPA (POCIS-MIP). In a first time, this study showed an important temporal variability for grab water sample collected during each 14-d period. Furthermore, the comparison between the data acquired with the three different techniques highlighted the contribution of passive sampling for improving quantification rates. In a second time, an estimation of the temporal variability related to the sampling step was carried out by the normalization of spot water sampling and POCIS data by a reference value (composite samples). The total variability associated to the spot and passive samplings were in the same range, and mainly explained by the uncertainty due to the sampling step. For example, the sampling step uncertainty, for annual concentration estimate of imidacloprid, were 48% and 45%, for POCIS-HLB and weekly spot sampling, respectively. For POCIS, this uncertainty could be attributed to a typical range of factor 2 of the sampling rates, depending on environmental conditions, like the flow velocity (Harman et al. 2012, Morin et al. 2012). For spot water sampling this variability could be rather explained by both temporal heterogeneity and transport/conservation steps before analysis. Allan, I. J., et al. (2006). "Strategic monitoring for the European water framework directive." TrAC Trends in Analytical Chemistry 25(7): 704-715. Harman, C., et al. (2012). "Calibration and use of the polar organic chemical integrative sampler—a critical review." Environmental Toxicology and Chemistry 31(12): 2724-2738. Morin, N., et al. (2012). "Chemical calibration, performance, validation and applications of the polar organic chemical integrative sampler (POCIS) in aquatic environments." TrAC Trends in Analytical Chemistry 36: 144-175. Ort, C., et al. (2010). "Sampling for PPCPs in wastewater systems: Comparison of different sampling modes and optimization strategies." Environmental Science and Technology 44(16): 6289-6296

Wastewater suspended solids study by optical methods

International audienceThe aim of the paper is to compare two optical methods (UV spectrophotometry and laser granulometry) for a better knowledge of the behaviour of wastewater suspended solids. The first one, based on UV spectrophotometry, is used for the estimation of solids concentration and nature in water and wastewater with the help of an advanced exploitation method of UV spectra. But the interpretation of UV spectra, in presence of a very wide size distribution of solids is not always easy, because of the different phenomena responsible of light diffusion. The second method, more classical, allows to characterise the size distribution of particles

Study of UV–vis responses of mineral suspensions in water

International audienceThe aim of this work is to study UV–vis responses of mineral particles and colloids in order to obtain a better understanding of “physical” absorption phenomena. The study of mineral-suspended solids and colloids allows to point out the influence of the size on UV–vis spectra. A typology of UV responses of particles according to their size and a model spectrum of mineral colloids are proposed

Etalonnage des échantillonneurs passifs du type POCIS pour les pesticides polaires : essai d'intercomparaison et recommandations pour l'harmonisation des données d'étalonnage en laboratoire

La perspective d’application des échantillonneurs passifs dans le cadre de la DCE nécessite au préalable l’établissement de données d’étalonnage fiables. Or, concernant des dispositifs tels que les Polar Organic Chemical Integrative Samplers (POCIS), a priori adaptés pour l’échantillonnage des pesticides organiques polaires, ces données sont encore peu renseignées et/ou très hétérogènes ou alors déterminées via des systèmes expérimentaux en laboratoire certes contrôlées mais aussi très variables. D’après l’étude de la littérature à ce sujet, à défaut de disposer de valeurs de référence, il ressort un besoin d’harmonisation des constantes cinétiques (ou encore des taux d’échantillonnage) et de recommandations quant à la manière de les acquérir. Ainsi, il a été mené un essai d’intercomparaison portant sur l’étalonnage d’une liste commune d’herbicides polaires (acétochlore, alachlore, atrazine, diuron et linuron) au sein de trois laboratoires experts dans le domaine de l’échantillonnage passif et membre du consortium Aquaref. Le second objectif de ce travail a visé l’étude de l’influence des conditions expérimentales et des systèmes utilisés pour l'étalonnage, à savoir le système employé, le niveau de dopage des eaux en pesticides, l’agitation du milieu ou encore la température, ce qui a permis d’appréhender la robustesse des données associée à la phase d’étalonnage en laboratoire. Les données d’échantillonnage obtenues dans les différents laboratoires impliqués étant comparables pour les molécules « communes » aux différents essais, l’agrégation des données des différents laboratoire a été réalisée pour fournir l’intégralité des données de taux d’échantillonnage acquises à ce jour