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Leiva G. M.A.,University of Chile | Leiva G. M.A.,Centro Nacional del Medio Ambiente | Morales S.,Centro Nacional del Medio Ambiente | Segura R.,University of Santiago de Chile
Water, Air, and Soil Pollution | Year: 2013

Two methods to measure mercury concentration in soil are compared, and their compliance with international standards is determined: cold vapour atomic absorption spectrometry and thermal decomposition, amalgamation and atomic absorption spectrophotometry. The detection limit, quantification limit and uncertainty of these two analytical methods were evaluated and compared. The results indicated that thermal decomposition, amalgamation and atomic absorption spectrophotometry had a lower quantification limit and uncertainty than cold vapour atomic absorption spectrometry (quantification limit, 0.27 vs. 0.63 mg kg-1; expanded uncertainty, 9.30 % vs. 10.8 %, respectively). Thermal decomposition, amalgamation and atomic absorption spectrophotometry allowed the determination of the base values for the concentration of mercury in soil recommended by international standards, achieving a lower detection limit than cold vapour atomic absorption spectrometry under the study conditions. In addition, thermal decomposition, amalgamation and atomic absorption spectrophotometry represent a more environmentally friendly alternative for mercury determination because this method uses fewer reagents and therefore generates less waste. © 2013 Springer Science+Business Media Dordrecht.

Munoz R.C.,University of Chile | Falvey M.J.,University of Chile | Araya M.,Centro Nacional del Medio Ambiente | Jacques-Coper M.,University of Bern
Journal of Applied Meteorology and Climatology | Year: 2013

The near-surface wind and temperature regime at three points in the Atacama Desert of northern Chile is described using two years of multilevel measurements from 80-m towers located in an altitude range between 2100 and 2700m MSL. The data reveal the frequent development of strong nocturnal drainage flows at all sites. Down-valley, nose-shaped wind speed profiles are observed, with maximum values occurring at heights between 20 and 60m AGL. The flow intensity shows considerable interdaily variability and a seasonal modulation of maximum speeds, which in the cold season can attain hourly average values of more than 20 ms-1. Turbulent mixing appears to be important over the full tower layer, affecting the curvature of the nighttime temperature profile and possibly explaining the observed increase of surface temperatures in the down-valley direction. Nocturnal valley winds and temperatures are weakly controlled by upper-air conditions observed at the nearest aerological station. Estimates of terms in the momentum budget for the development and quasi-stationary phases of the down-valley flows suggest that the pressure gradient force due to the near-surface cooling along the sloping valley axes plays an important role in these drainage flows. A scale for the jet nose height of equilibrium turbulent down-slope jets is proposed that is based on surface friction velocity and surface inversion intensity. At one of the sites, this scale explains about 70% of the caseto-case observed variance of jet nose heights. Further modeling and observations are needed, however, to define better the dynamics, extent, and turbulence structure of this flow system, which has significant windenergy, climatic, and environmental implications. © 2013 American Meteorological Society.

Abrutzky R.,National University of San Martin of Argentina | Ibarra S.,Centro Nacional del Medio Ambiente | Matus P.,University of Los Andes, Chile | Romero-Lankao P.,University of Colorado at Boulder | And 2 more authors.
International Journal of Environment and Health | Year: 2013

This work aims to deepen recent studies on the impact of air pollution on human health in Latin American cities. A time series study has been performed comparing the mortality attributable to atmospheric carbon monoxide (CO) and nitrogen oxides (NOx) in Santiago (Chile) and Buenos Aires (Argentina). Pollution, meteorological and mortality data have been integrated in a General Additive Model (GAM) to establish the correlation between pollutant concentration levels and daily death counts. The analysis includes other variables such as gender, age and causes of death for each city with the result that both cities show increased deaths that can be attributed to an increase in CO and NOx levels. The impact is higher for Santiago's populations, for all the studied groups. This may be related to previous exposure to high pollution levels or to the co presence of other pollutants not accounted for in this study. Copyright © 2013 Inderscience Enterprises Ltd.

Leiva G.M.A.,University of Chile | Araya M.C.,University of Chile | Alvarado A.M.,University of Chile | Seguel R.J.,University of Chile | Seguel R.J.,Centro Nacional del Medio Ambiente
Accreditation and Quality Assurance | Year: 2012

The present work presents a measurement uncertainty evaluation according to Guide to the Expression of Uncertainty in Measurement (GUM) of the concentration of the cations K + and Li + and anions NO 3 -2 and SO 4 -2 in fine airborne particulate matter, refers to particles less than 2.5 μm in diameter (PM 2.5), as measured by ion chromatography (US-EPA 300 method). The GUM method is not typically used to report uncertainty. In general, the analytical results only report the measurement's standard deviation under repetition as an uncertainty; thus, not all sources of uncertainty are considered. In this work, the major sources of uncertainty regarding the measurements were identified as contributions to linear least square regression lines, repeatability, precision, and trueness. The expanded uncertainty was approximately 20% for anions and cations. The largest contribution to uncertainty was found to be repeatability. © 2011 Springer-Verlag.

Seguel R.J.,Centro Nacional del Medio Ambiente | Morales S. R.G.E.,University of Chile | Leiva G. M.A.,University of Chile
Environmental Pollution | Year: 2012

The study examined weekday-weekend differences in ozone, NO x (NO and NO 2) and VOC concentrations in Santiago, Chile, from 1999 to 2007. The results provide evidence for the occurrence of an atmospheric phenomenon that produces higher ozone concentrations during weekends despite lower concentrations of ozone precursors. This phenomenon is known as the weekend effect (WE). The overall ozone decrease since the spring of 2004 was a consequence of the implementation of several urban pollution control measures. Although these measures caused a decline in the number of days that exceed the national standard from two-thirds to one-third of summer days, the WE, which became statistically significant beginning in September 2004, could not be eliminated. Furthermore, VOC/NO x ratios decreased during the same period (2004), especially in the most industrialized area of Santiago. Similarly, under these regimes, the VOC/NO x ratios were higher on Sundays than on weekdays and caused higher ozone concentrations on Sundays. © 2011 Elsevier Ltd. All rights reserved.

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