Norbert Magyar

Classification into homogeneous groups using combined cluster and discriminant analysis

Abstract The classification of observations into groups is a general procedure in modern research. However, when searching for homogeneous groups the difficulty of deciding whether further division of a classification is necessary or not to obtain the desired homogeneous groups arises. The presented method, Combined cluster and discriminant analysis (CCDA), aims to facilitate this decision. CCDA consists of three main steps: (I) a basic grouping procedure; (II) a core cycle where the goodness of preconceived and random classifications is determined; and (III) an evaluation step where a decision has to be made regarding division into sub-groups. These steps of the proposed method were implemented in R in a package, under the name of ccda. To present the applicability of the method, a case study on the water quality samples of Neusiedler See is presented, in which CCDA classified the 33 original sampling locations into 17 homogeneous groups, which could provide a starting point for a later recalibration of the lakes monitoring network.

The Water Framework Directive: Can more information be extracted from groundwater data? A case study of Seewinkel, Burgenland, eastern Austria

Water protection is one of the most important goals in environmental protection. The Clean Water Act in the USA and the Water Framework Directive (WFD) in Europe are the legal frameworks to facilitate the achievement of this goal. The question is raised of whether more information can be extracted from WFD-related groundwater data. To answer it, a methodology has been developed that is easy to use and could be implemented into official practice. A case study is presented in which the groundwater data of a sodic area in Austria (Seewinkel) is assessed. Eighteen parameters in groundwater sampled from 23 wells (1991–2011) were analyzed. With basic statistics, trend-, cluster-, Wilks’ λ and spatial sampling density analysis, local phosphorus and boron phenomena were described, along with the determining role of sulphate, groundwater flow, and the oxygen gradient in the area. As a final step, the spatial sampling density was determined. Regarding the current set of parameters, all the sampling sites are necessary and only in the case of certain parameters (Ca2+, Mg2+, K+, NO3−, pH) could one sampling site be abandoned. The methodology applied brings a new perspective to exploring groundwater data collected according to the requirements of the WFD.ZusammenfassungGewässerschutz ist eines der wichtigsten Ziele im Umweltschutz. Der “Clean Water Act” in den USA und die Wasserrahmenrichtlinie (WRRL) in Europa sind die rechtlichen Rahmenbedingungen, um dieses Ziel zu erreichen. Dabei stellt sich die Frage, ob weitere verbesserte Informationen aus den derzeitigen Grundwasserqualitätsmessungen, die im Rahmen der WRRL erhoben werden, gewonnen werden können. Um diese Frage zu beantworten, wurde eine Methodik entwickelt, die einfach zu bedienen ist und leicht in die offizielle Auswertungspraxis umgesetzt werden könnte. In der vorgestellten Fallstudie wurden die Daten eines Grundwasserkörpers in Österreich (Seewinkel) mit der entwickelten Methode ausgewertet. Dazu wurden achtzehn Parameter aus 23 Grundwassergütemessstellen für die Jahre 1991–2011 analysiert. Dazu wurden grundlegende statistische Methoden wie Trend -, Cluster -, Wilks’ λ Analyse und die Auswertung der räumlichen Verteilung der Messdichte verwendet. Unter Berücksichtigung mit der bestimmenden Rolle von Sulfat, der Grundwasserfließrichtung und -zeit und dem Sauerstoffgradienten im Untersuchungsgebiet Seewinkel konnten lokale Phosphor und Bor Phänomene beschrieben werden. Im letzten Schritt wurde die räumliche Verteilung der Messdichte bestimmt. Die Datenanalysen zeigten, dass alle, bis auf eine Ausnahme, vorhandenen Messstellen und deren Parameter (Ca2+, Mg2+, K+, NO3−, pH-Wert) für Auswertungen verwendet werden konnten. Die angewandte Methodik bringt bei der Analyse der erhobenen Grundwasserqualitätsdaten, welche nach den Anforderungen der WRRL erhoben werden, eine neue Perspektive.RésuméLa protection de l’eau est l’un des objectifs les plus importants de la protection environnementale. Le Clean Water Act aux Etats Unis et la Directive-Cadre sur l’Eau (DCE) en Europe sont les cadres légaux pour favoriser l’atteinte de cet objectif. La question est posée de savoir si l’on peut tirer d’avantages d’informations des données sur l’eau souterraine relatives à la DCE. Pour répondre à celle-ci, on a développé une méthodologie simple, pouvant être mise en pratique de façon officielle. Le cas présenté considère les données sur l’eau souterraine d’un district sodique d’Autriche (Seewinkel). Dix huit paramètres de l’eau de 23 puits échantillonnés (1991–2011) ont été analysés. Avec les paramètres statistiques de base, tendance, classes, paramètre λ de Wilks et analyse de la densité spatiale d’échantillonnage, les phénomènes locaux liés au phosphore et au bore ont été décrits, ainsi que le rôle déterminant du sulfate, le flux d’écoulement souterrain et le gradient de l’oxygène dans la zone. En phase finale, la densité d’échantillonnage spatial a été déterminée. Etant donné le jeu de paramètres considérés, tous les sites échantillonnés sont nécessaires, les sites où certains paramètres (Ca2+, Mg2+, K+, NO3−, pH) ne pouvaient être mesurés étant abandonnés. La méthodologie appliquée ouvre une nouvelle perspective dans l’exploitation des données sur l’eau souterraine prélevées selon les dispositions de la Directive-Cadre sur l’Eau.ResumenLa protección del agua es uno de los objetivos más importantes en la protección ambiental. La Ley de Aguas Limpias en EEUU y la Directiva Marco del Agua (WFD) en Europa son los marcos legales para facilitar el logro de este objetivo. La cuestión se plantea si se puede extraer mayor información de los datos de agua subterránea relacionados con WDF. Para responder se desarrolla una una metodología que es fácil de usar y podría ser implementada dentro de la práctica oficial. Se presenta un caso de estudio en el cual se evaluaron los datos de agua subterránea de un área sódica en Austria (Seewinkel). Se analizaron dieciocho parámetros en el agua subterránea muestreada de 23 pozos (1991–2011). Con estadísticas básicas, tendencias, clusters, Wilks’ λ y análisis de densidad espacial de muestreo se describieron los fenómenos locales de fósforo y de boro fueron descriptos, conjuntamente con el rol determinante del sulfato, del flujo de agua subterránea, y del gradiente de oxígeno en el área. Como una etapa final, se determinó la densidad de muestreo espacial. En relación con el conjunto actual de parámetros, todos los sitios de muestreos son necesarios y solamente en el caso de ciertos parámetros (Ca2+, Mg2+, K+, NO3−, pH) podría un sitio de muestreo ser abandonado. La metodología aplicada otorga una nueva perspectiva para explorar los datos de agua subterránea recolectados de acuerdo a los requerimientos de la WFD.الملخصحماية المياه هي واحدة من اهم الاهداف في الحماية البيئية. قانون المياه النظيفة في الولايات المتحدة الامريكية والاطار التوجيهي للمياه(WFD) في اوروبا هما من الاطر القانونية لتسهيل تحقيق هذا الهدف . اثيرت مسألة ما اذا كان مزيد من المعلومات يمكن استخصلاصها من الاطار التوجيهي للمياه (WFD) – المتعلقة ببيانات المياه الجوفية. للاجابة على ذلك ، تم تطوير منهجية سهلة الاستخدام ويمكن تنفيذها في الممارسة الرسمية . قدمت دراسة الحالة التي يتم فيها تقييم بيانات المياه الجوفية من منطقة سوديك في النمسا .(Seewinkel) حللت ثمانية عشر معيارا في المياه الجوفية قد تم اخذ عيناتها من ٢٣ بئرا (١٩٩١-٢٠١١).مع احصائية بسيطة، الاتجاه ،الكتلة ، ويلكس λ ومكانية تحليل كثافة اخذ العينات . ظاهرة الفوسفور والبورون المحلية قد وصفت جنبا الى جنب مع دور تحديد الكبريتات ، تدفق المياه الجوفية، والتدرج الاوكسجين في المنطقة . كخطوة نهائية ، تم تحديد كثافة اخذ العينات المكانية . وفيما يتعلق المجموعة الحالية من المعاير ، جميع مواقع اخذ العينات ضرورية و فقط في حالة معايير معينة (Ca2+, Mg2+, K+, NO3-, pH) يمكن ان يتم التخلي عن موقع واحد.المنهجية المطبقة يجلب منظورا جديدا لاستكشاف بيانات المياه الجوفية التي تم جمعها وفق لمتطلبات الاطار التوجيهي للمياه (WFD) .摘要水保护是环境保护中最重要的目标之一。美国的清洁水法及欧洲水框架指令是促进完成这个目标的法律体系。是否能从水框架指令有关的地下水数据中提取更多信息的问题被提了出来。为回答这个问题,开发了便于使用、能够正式实施的方法。展示了一个研究实例,在这个实例中,评价了奥地利(Seewinkel)含钠区的地下水数据。分析了23口井(1991–2011年)中地下水样品的十八个参数。描述了基本统计数字以及趋势的、簇群的Wilks’ λ、空间采样密度分析、局部磷和硼现象,并确定了该区的硫酸盐的作用、地下水流和氧梯度。作为最后一步,确定了空间采样密度。关于目前参数(Ca2+, Mg2+, K+, NO3−, pH)的设置,所有的采样地点都很必要,只有在某些参数情况下,一个采样点可以放弃。所应用的方法给探索按照水框架指令要求收集到的地下水数据带来了新的前景。SamenvattingWater bescherming is een van de belangrijkste doelen in bescherming van het milieu. De Clean Water Act in de Verenigde Staten en de Water Framework Directive in Europa zijn de wettelijke kaders waarin deze doelen worden bereikt. De vraag is opgekomen of meer informatie verkregen kan worden van WFD gerelateerde grondwater data. Om deze vraag te beantwoorden is een methode ontwikkeld die makkelijk te gebruiken is en geimplementeerd kan worden door officiele instanties. Een case study wordt gepresenteerd waarin grondwater data van een alkali regio in Oostenrijk (Seewinkel) wordt beoordeeld. Achttien parameters in grondwater bemonsterd in 23 verschillende peilbuizen (1991–2011) zijn geanalyseerd. Met behulp van basis statistiek, trend-, cluster-, Wilks’ λ en ruimtelijke bemonster dichtheid analyses, werden lokale fosfor en boor fenomenen beschreven, net als de bepalende rol van sulfaat, grondwater stroming, en de zuurstof gradient in het onderzoeksgebied. Als laatste stap werd de ruimtelijke bemonster dichtheid bepaald. Met betrekking tot de huidige set aan parameters, waren alle bemonsteringsplekken noodzakelijk. Slechts bij sommige parameters (Ca2+, Mg2+, K+, NO3-, pH) kon één bemonsteringsplek worden opgegeven. De gebruikte methodologie geeft een nieuw perspectief aan het onderzoeken van grondwater data die verzameld zijn volgens de eisen van de WFD. KivonatA felszíni és felszín alatti vizeink jó állapotban való megőrzése a környezetvédelem egyik legfontosabb célja. Az Amerikai Egyesült Államokban a “Clean Water Act”, Európában pedig a Víz Keretirányelv biztosítja a jogi keretet ezen célok eléréséhez. Felmerül azonban a kérdés, hogy hordoznak-e számottevő többletinformációt a felszín alatti víz monitoring adatok a Víz Keretirányelv által előírt vizsgálatok eredményein túl. A kérdés megválaszolására egy olyan módszertant dolgoztunk ki, amely könnyen alkalmazható a környezetvédelmi hivatali gyakorlatban is. Esettanulmányként, egy ausztriai szikes terület (Seewinkel) 23 felszín alatti víz monitoring kútjának 18 paraméterének idősorait dolgoztuk fel az 1991–2011-es időintervallum vonatkozásában alap- és Wilks’ λ statisztikák, valamint trend-, klaszter-, és variogram analízis felhasználásával. Az eredmények alapján a terület bizonyos részein lokális foszfor, bór és szulfát anomália, illetve az egész területre vonatkozó oxigén gradiens figyelhető meg. Végezetül meghatároztuk a szükséges térbeli mintavételezési gyakoriságot. Az összes mért paramétert figyelembe véve minden mintavételi pontra szükség van a területen, csak néhány paraméter vonatkozásában (Ca2+, Mg2+, K+, NO3−, pH) lehetne egy mintavételi pontot megszüntetni. Az alkalmazott módszertan egy újszerű megk

Spatial Optimization of Monitoring Networkson the Examples of a River, a Lake-Wetland System and a Sub-Surface Water System

Monitoring systems in general have to meet numerous requirements, the most important of which are representativeness and cost efficiency. The aim of the study, therefore, was to present the spatial optimization of the monitoring networks of a river (the Danube), a wetland-lake system (Kis-Balaton & Lake Balaton), and a sub-surface water system in the watershed of Lake Neusiedl/Fertő over a period of approximately two decades using a novel method, Combined cluster and discriminant analysis (CCDA). In the case of the river the results show that the monitoring network yields redundant information on certain sections, so that of 12 sampling sites 3 can be discarded. It was not, however, enough to consider just the tributaries when it comes to optimization. In the case of the wetland (Kis-Balaton) one pair of sampling sites out of 12, while in the case of Lake Balaton 5 out of 10 can be abandoned. For the sub-surface water system, however, all the 50 sites contained exclusive information; hence, all of these were shown to be necessary. In addition, neighboring sampling sites were compared pairwise using CCDA and the corresponding results were visualized in diagrams or so called “difference maps” indicating the location of the biggest differences. This approach also indicates the researcher where to place new sampling sites should the possibility arise. The discussed methodology proved to be highly useful in the optimization of the monitoring networks of the presented water systems.

Optimisation of solid-state urea clathrate formation as a chemical separation method coupled to compound-specific stable carbon isotope analysis

ABSTRACT Solid-state urea clathrate formation (SSUCF) as a chemical separation method prior to stable carbon isotope fingerprinting of diesel fuel contaminations was studied. The stable carbon isotope ratios (δ13C) of n-alkanes in diesel fuel can be used to trace the origin of a contamination. The accurate measurement of the stable isotopic composition of individual compounds requires baseline separation from any other co-eluting compounds. For this purpose silica gel column chromatography (SGCC) and SSUCF were applied. Detailed optimisation of SSUCF was performed: different activators, clathrate formation temperatures, activator volumes, clathrate formation times and sample capacity were investigated. The main benefits of the developed method are reduced clathrate formation time and increased recoveries for lower molecular weight n-alkanes. The recoveries of the developed SSUCF method ranged between 63 and 100% for C10–C24 n-alkanes with relative standard deviation no more than 7%. The precision of the gas chromatography-isotope ratio mass spectrometry measurement was acceptable with a standard deviation of the δ13C values ranging between 0.08 and 0.15‰. The absence of isotopic fractionation was also investigated. The robustness of the method was tested within a model experiment. Nine different water samples including distilled water, tap water, river water, industrial wastewaters and groundwater samples were spiked with the same diesel fuel. The water samples were extracted with n-hexane and after purification with both SGCC and SSUCF n-alkanes were measured. The δ13C values of n-alkanes were found to be similar for all samples. The importance of sample purification prior to compound-specific isotope analysis (CSIA) was also demonstrated within this model experiment by analysing samples from different stages of the sample preparation. Our results show that the proposed method can remarkably improve the precision of compound-specific stable carbon isotope analysis of n-alkanes originating from diesel contamination of the aquatic environment.

Effects of the introduction of pre-treated wastewater in a shallow lake reed stand

Abstract Reed stands may be employed in the amelioration of water quality or even in the treatment of wastewater. In this study, the nutrient concentrations of (i) the above- and below-ground Common Reed (Phragmites australis) biomass, and (ii) surface and interstitial water were analyzed in a natural stand used in wastewater treatment. The reed stand was located in Hungarian part of Lake Fertő/Neusiedler See, by the shore near Fertőrákos Bay. The nitrate, phosphate and dissolved organic nitrogen concentrations of surface water were found to be higher on the inlet side of the reed stand compared to the outlet. The N and P concentrations in the above-ground biomass and P concentrations in the below-ground biomass increased after the introduction of pre-treated wastewater. The inter-annual differences in the characteristics of sediment interstitial water and in the nutrient content of reed tissues were assessed using statistical methods. The samples taken before and after the introduction of the pre-treated wastewater in the parcel formed different clusters. The results of the study provide further evidence that the nutrient retention capacity of natural stands of P. australis may be employed in the treatment of wastewater while protecting and preserving the valuable natural assets of the lake.

Migration of Tinuvin P and Irganox 3114 into milk and the corresponding authorised food simulant

Migration of Tinuvin P (UV stabiliser) and Irganox 3114 (antioxidant) from high-density polyethylene (HDPE) was studied. HDPE pieces were soaked in either milk (1.5% or 3.5% fat content) or 50% (v/v) ethanol–water mixture – the food simulant for milk as specified in Regulation No. 10/2011/EC. The obtained extracts were analysed by LC-MS/MS. For statistical assessment variography was used. It proved to be a useful tool for making a distinction between the early migration range and the equilibrium, despite the variance of the data. Regulation No. 10/2011/EC specifies 10 days of contact time for milk at 5°C. Our experiments with the food simulant with 24 dm2 kg−1 surface/mass ratio showed that both Tinuvin P and Irganox 3114 need less than 1 h to reach equilibrium. Furthermore, 10-day experiments with daily sampling showed that these additives are stable in milk, as well as in the food simulant. The effect of the concentration of the additives in HDPE was studied in the 0.01–5% (m/m) range. For both Tinuvin P and Irganox 3114 and all three extractants the migrated amount became independent of the concentration of the additive in the HDPE approximately at 1% (m/m). For Tinuvin P the food simulant gave a close estimate for the milk samples. However, using the food simulant for modelling the migration of Irganox 3114 into milk gave an overestimation with a factor of minimum 3.5. In the case of Tinuvin P special care must be taken, since the recommended amount in the HDPE can result in additive concentrations near or even over the specific migration limit (SML). However, Irganox 3114 cannot reach the SML either in milk or in the food simulant. Graphical Abstract

Combined cluster and discriminant analysis: An efficient chemometric approach in diesel fuel characterization

Combined cluster and discriminant analysis (CCDA) as a chemometric tool in compound specific isotope analysis of diesel fuels was studied. The stable carbon isotope ratios (δ13C) of n-alkanes in diesel fuel can be used to characterize or differentiate diesels originating from different sources. We investigated 25 diesel fuel samples representing 20 different brands. The samples were collected from 25 different service stations in 11 European countries over a 2 year period. The n-alkane fraction of diesel fuels was separated using solid-state urea clathrate formation combined with silica gel fractionation. The stable carbon isotope ratios of C10-C24 n-alkanes were measured with gas chromatography-isotope ratio mass spectrometry (GC-IRMS) using perdeuterated n-alkanes as internal standards. Beside the 25 samples one additional diesel fuel was prepared and measured three times to get totally homogenous samples in order to test the performance of our analytical and statistical routine. Stable isotope ratio data were evaluated with hierarchical cluster analysis (HCA), principal component analysis (PCA) and CCDA. CCDA combines two multivariate data analysis methods hierarchical cluster analysis with linear discriminant analysis (LDA). The main idea behind CCDA is to compare the goodness of preconceived (based on the sample origins) and random groupings. In CCDA all the samples were compared pairwise. The results for the parallel sample preparations showed that the analytical procedure does not have any significant effect on the δ13C values of n-alkanes. The three parallels proved to be totally homogenous with CCDA. HCA and PCA can be useful tools when the examining of the relationship among several samples is in question. However, these two techniques cannot be always decisive on the origin of similar samples. The initial hypothesis that all diesel fuel samples are considered chemically unique was verified by CCDA. The main advantage of CCDA is that it gives an objective index number about the level of similarity among the investigated samples. Thus the application of CCDA supplemented by the traditionally used multivariate methods greatly improves the efficiency of statistical analysis in the CSIA of diesel fuel samples.