<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0188-4999</journal-id>
<journal-title><![CDATA[Revista internacional de contaminación ambiental]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. Int. Contam. Ambient]]></abbrev-journal-title>
<issn>0188-4999</issn>
<publisher>
<publisher-name><![CDATA[Universidad Nacional Autónoma de México, Instituto de Ciencias de la Atmósfera y Cambio Climático]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0188-49992019000100165</article-id>
<article-id pub-id-type="doi">10.20937/rica.2019.35.01.12</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[ANÁLISIS DE SUPERVIVENCIA A LA DETECCIÓN Y CORRECCIÓN DE LA CONTAMINACIÓN EN SERIES CON VALORES POR DEBAJO DEL LÍMITE DE DETECCIÓN]]></article-title>
<article-title xml:lang="en"><![CDATA[SURVIVAL ANALYSIS TO THE DETECTION AND CORRECTION OF POLLUTION IN SERIES WITH VALUES BELOW DETECTION LIMIT]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Grima-Olmedo]]></surname>
<given-names><![CDATA[Carlos]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Grima-Olmedo]]></surname>
<given-names><![CDATA[Juan]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Luque-Espinar]]></surname>
<given-names><![CDATA[Juan Antonio]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Pardo-Iguzquiza]]></surname>
<given-names><![CDATA[Eulogio]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Ramírez-Gómez]]></surname>
<given-names><![CDATA[Álvaro]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad Politécnica de Madrid Escuela Técnica Superior de Ingenieros de Minas y Energía de Madrid Departamento de Ingeniería Geológica y Minera]]></institution>
<addr-line><![CDATA[Madrid ]]></addr-line>
<country>Spain</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Instituto Geológico y Minero de España Department of Research on Geological Resources ]]></institution>
<addr-line><![CDATA[Valencia ]]></addr-line>
<country>España</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,Instituto Geológico y Minero de España Department of Research on Geological Resources ]]></institution>
<addr-line><![CDATA[Granada ]]></addr-line>
<country>España</country>
</aff>
<aff id="Af4">
<institution><![CDATA[,Instituto Geológico y Minero de España Department of Research on Geological Resources ]]></institution>
<addr-line><![CDATA[Madrid ]]></addr-line>
<country>España</country>
</aff>
<aff id="Af5">
<institution><![CDATA[,Escuela Técnica Superior de Ingeniería y Diseño Industrial Departamento de Ingeniería Mecánica, Química y Diseño Industrial ]]></institution>
<addr-line><![CDATA[Madrid ]]></addr-line>
<country>España</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>00</month>
<year>2019</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>00</month>
<year>2019</year>
</pub-date>
<volume>35</volume>
<numero>1</numero>
<fpage>165</fpage>
<lpage>178</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0188-49992019000100165&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0188-49992019000100165&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0188-49992019000100165&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[RESUMEN El artículo 17 de la Directiva Marco del Agua insta a la Comisión y al Parlamento europeos a proteger el agua subterránea, y establece los criterios para determinar su estado químico y definir estándares de calidad ambiental. Si consideramos las características específicas de los contaminantes en agua subterránea, es preciso utilizar ensayos estadísticos adecuados. En el anexo IV de la Directiva de Aguas Subterráneas se establece que las medidas por debajo del límite de cuantificación (LC) deben sustituirse por la mitad del LC más alto, con la excepción de plaguicidas totales. Aunque es posible estimar valores medios en datos censurados con un único LC, su sustitución distorsiona los intervalos de confianza usados para verificar la tolerancia con umbrales. Las redes oficiales de monitoreo presentan escasos registros con valores por debajo del LC. Con objeto de establecer un marco metodológico para su evaluación, se han tomado valores de concentración de nitratos para realizar posteriormente una censura artificial. Se han seleccionado dos cuerpos de agua subterránea con diferentes características y frecuencias de monitoreo: la Plana de Sagunto, en la zona oriental de España, y un sector del Valle Central (Chile), situado en torno a los sistemas fluviales de los ríos Tinguirica y Antivero. Mediante la simulación de diferentes porcentajes de censura a los datos se han ensayado varios métodos. Se ha demostrado que las técnicas específicas de estimación de valores censurados, como Kaplan-Meier o regresión robusta ser las más eficientes para verificar el cumplimiento de los estándares ambientales.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[ABSTRACT Under article 17 of the Water Framework Directive the European Union was required to establish a framework to protect groundwater and set criteria for determining its chemical status and define environmental quality standards. Considering the specific characteristics of contaminants in groundwater, it is necessary to use adequate statistical tests. Annex IV of the Groundwater Directive establishes that all measurements below the limit of quantification (LOQ) must be replaced by half of the highest LOQ, with the exception of total pesticides. Although it is possible to estimate mean values in data censored with a single LOQ, its substitution distorts the confidence intervals used to verify tolerance with thresholds. The official monitoring networks lack series with values below the LOQ. In order to set up a methodological framework for its evaluation, nitrate concentration values have been taken in order to perform a subsequent artificial censorship. Two groundwater bodies with different monitoring characteristics and frequencies have been selected, Plana de Sagunto, in the eastern part of Spain, and a sector of the Central Valley (Chile), located around the systems of Tinguirica and Antivero rivers. Through the simulation of different percentages of censorship to data, several methods have been tested. Specific techniques for estimating censored values, such as Kaplan-Meier or robust regression have proven to be the most efficient to verify compliance with environmental standards.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[datos censurados]]></kwd>
<kwd lng="es"><![CDATA[directiva marco del agua]]></kwd>
<kwd lng="es"><![CDATA[Kaplan-Meier]]></kwd>
<kwd lng="es"><![CDATA[regresión robusta]]></kwd>
<kwd lng="en"><![CDATA[censored data]]></kwd>
<kwd lng="en"><![CDATA[water framework directive]]></kwd>
<kwd lng="en"><![CDATA[Kaplan-Meier]]></kwd>
<kwd lng="en"><![CDATA[robust regression]]></kwd>
</kwd-group>
</article-meta>
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