Environment 2010: Situation and Perspectives for the European Union 6-10 May Porto, Portugal

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1 PAPER G 04 Environment 2010: Situation and Perspectives for the European Union ASSESSMENT OF THE RELEVANT PROPERTIES OF SMECTITIC CLAYS FROM AVEIRO AND COIMBRA REGIONS WITH REGARD TO THEIR POTENTIAL USE AS LINERS IN WASTE LANDFILLS Fernando Rocha & Celso Gomes Centro de Minerais Industriais e Argilas, Departamento de Geociências, Universidade de Aveiro, Aveiro, Portugal, cgomes@geo.ua.pt; frocha@geo.ua.pt KEYWORDS clay liners, waste landfills, smectitic clays ABSTRACT This paper deals with the comparative appraisal, in terms of mineral composition, chemical composition and other relevant properties required for clay liners, of representative samples from Taveiro/Coimbra clay deposits belonging to the Argilas de Taveiro formation (Upper Cretaceous/Lower Paleocene) and from the Bustos/Aveiro clay deposits belonging to the Argilas de Aveiro formation (Upper Cretaceous). Mineralogical composition, chemical composition and grain size distribution was assessed as well as specific surface area, cation exchange capacity, expandability and plasticity. In general terms, the studied clays can be considered as good materials to be used as impermeable liners in the waste land-fills. In terms of the comparative appraisal of the properties of the clays from the deposits referred to it was found, from the preliminary results obtained so far, that the clays showing better characteristics for that application are those from Bustos quarries. INTRODUCTION Clays are fundamental materials to be used as impermeable liners in the waste land-fills. Liners are broadly classified into four major groups: soil liners, geomembranes (also called flexible membrane liners), geosyntethic clay liners and vertical cutoff walls (Oweis & Khera, 1998). The purpose of all liners is to restrict fluid migration from the facility into the environment. Soil liners usually consist of natural inorganic smectite rich clays or clayey soils. The geological information plays a central role in the planning, utilization and preservation of geologic resources, supporting essential social functions, such as: preventing geological hazards as are the cases of ground water reservoirs contamination and soil erosion, supporting the confinement of polluting substances; and, naturally, the exploration and exploitation of geologic resources. In the Aveiro and Coimbra regions, in the centre of Portugal, heavy clays utilized for structural ceramics are quite common. Actually, among the most important geological resources of the studied area (figure 1) are the heavy clays, main source of raw materials for the several locally active ceramic plants. These clays contain smectite-illite-kaolinite assemblages (Rocha, 1993; Santos et al., 1996; Galhano et al., 1999) and are considered, from the hydrogeologic point of view, as presenting extremely low permeability. On the other hand, the soils developed on these clays show peculiar geotechnical properties, in particular in what concerns the properties required for their use as clay liners. This paper deals with the comparative appraisal, in terms of mineral composition, chemical composition and other relevant properties required for clay liners, of representative samples from Taveiro/Coimbra clay deposits belonging to the Argilas de Taveiro formation (Upper Cretaceous/Lower Paleocene) and from Bustos/Aveiro clay deposits belonging to the Argilas de Aveiro formation (Upper Cretaceous). Potential Use as Liners in Wastefills - page 1 of 6

2 Environment 2010: Situation and Perspectives for the European Union PAPER G 04 Figure 1 Location of sampling sites and geological setting. Potential Use as Liners in Wastefills - page 2 of 6

3 PAPER G 04 Environment 2010: Situation and Perspectives for the European Union MATERIALS AND METHODS Fifty four samples, representative of the lithological heterogeneities detected in each quarry, had been studied. Sampling was carried out in nine clay quarries, either with works or deactivated, referred to from North to South as follows (see Figure 1 for sampling sites location and geological setting): 1) Aveiro region: Aveiro 1 AV1 (urban area), Aveiro 2 AV2 (suburban area), Vagos VGS, Nariz NRZ and Bustos - BST; 2) Taveiro / Coimbra region: Ribeira de Frades - RF, Taveiro - TVR, Reveles - RVL and São Pedro - SP. For each sample mineralogical composition was estimated on total samples as well as on <63 µm (silt + clay) and <2 µm (clay) fractions, by X-ray diffraction. Qualitative and semi-quantitative mineralogical analyses did followed criteria recommended by Barahona (1974), Schultz (1964), Thorez (1976), Mellinger (1979) and Pevear and Mumpton (1989). Smectite structural order was assessed by the Biscaye cristallinity index (Biscaye, 1965). Clays chemical composition was assessed by X-ray fluorescence and flame-spectroscopy methods. Grain size distribution was assessed using wet sieving and a X-ray grain size analyser (Sedigraph, model 5100 of Micromeritics). Specific surface area was estimated by the methylene blue method, whereas cation exchange capacity was estimated by the ammonium acetate method. Expandability was measured according to the Portuguese LNEC E specification and the Atterberg Plastic and Liquid limits were determined in accordance with the Portuguese norm or standard NP , and the CasaGrande test. Univariate (Quality Control analysis) and multivariate (Principal Components analysis and Cluster analysis) data analysis of the textural, mineralogical, chemical and technological data had been carried out. The use of these statistical methods, as outlined by Imbrie and Van Andel (1964), Jöreskog et al. (1976), Davis (1986) and Reyment & Jöreskob (1993), permit a good characterization of the system data, reducing the complexity of the model and classifying the variables and samples into natural groups (Mezzadri & Saccani, 1989; Lopez-Aguayo & Gonzalez Lopez, 1995). RESULTS AND DISCUSSION In the Aveiro and Coimbra regions, the heavy clays utilized for structural ceramics present, in general, smectiteillite-kaolinite assemblages (Rocha, 1993; Santos et al., 1996; Galhano et al., 1999). In relative terms, quantitative variation of these clay minerals occurs locally. Clays from the Argilas de Aveiro formation Clays from the Argilas de Aveiro formation are characterized (Rocha, 1993) by a predominance of very simple mineral assemblages in regards with both clay minerals (essentially illite+smectite, with a subsidiary presence of kaolinite) and the associated non-clay minerals (essentially quartz+k-feldspar, as well as an episodic presence of dolomite). The results achieved from the mineralogical studies point out, in what concerns the clay minerals, to a gradual evolution from an illitic-smectitic-kaolinitic assemblage in the outcrops of the northern sectors of the Argilas de Aveiro to an illitic-smectitic assemblage in the central sectors and, finally, to a more smectitic one in the southern sectors, where we can also find some distinctive aspects of the geochemical data, characterized by higher contents of Al 2 O 3, Fe 2 O 3 and Ignition Loss and lower contents of SiO 2. The textural data show that samples collected in the Nariz area are richer in silt the fraction whereas samples collected in the Vagos and Bustos areas are richer in the clay fraction. Potential Use as Liners in Wastefills - page 3 of 6

4 Environment 2010: Situation and Perspectives for the European Union PAPER G 04 The highest values for expandability, plasticity, clay fraction content and smectite content are found in samples from the Bustos sector (Galhano et al., 1999). The smallest values of the same parameters are found in samples from the Aveiro-2 sector. Both sectors: Aveiro-1 (corresponding to the urban area of the town) and Aveiro-2 (corresponding to the suburban area) show some differences with regards to the estimated parameters, the samples from the urban area being more plastic and expansive. From the application of R-mode factor analysis to the mineralogical and technological data, some interesting considerations could be drawn: Factor 1 shows illite (Ill) in opposition of smectite (Sm), expandability (Exp) and specific surface area (SSA). Factor 2 shows plasticity index (IP), total phyllosilicates contents (Phil) and clay fraction content (CF) in opposition of Activity. Factor 1 indicates a clear dependence upon expandability and specific surface area of the dominant clay mineral. Smectite influences positively both parameters, whereas illite has a clear negative influence. Factor 2 indicates that plasticity will increase whenever clays become enriched in both clay fraction and phyllosilicates. The cluster analysis of the same data confirms the associations observed in the R-mode factor analysis: illite (Ill) and kaolinite (Kt) are linked with activity and well separated from the other analysed parameters; smectite (Sm) is linked with expandability (Exp) and specific surface area (SSA); the plasticity index (IP) is linked with total phyllosilicates content (Phil) and clay fraction content (CF); finally, there are two clusters of samples - one corresponding to the set BST (Bustos area) and the other gathering all the other sets of samples (but with a subcluster composed, essentially, by samples of the Aveiro urban area). These sample associations discriminate very clearly the Bustos sector and less clearly the Aveiro-1 sector. This sectorial discrimination looks very consistent with the lateral evolution of the mineral composition of the clay fraction. In the Bustos sector to a composition dominantly smectitic correspond high expandabilities and plasticities; illite content increases towards the Aveiro-1 sector, fact that is reflected in a slight decrease in expandability and plasticity; on the other hand, kaolinite increases towards the Aveiro-2 sector, situation that is reflected in a notorious decrease of both expandability and plasticity. Clays from the Argilas de Taveiro formation Clays from the "Argilas de Taveiro" formation present a mineral composition characterised by very simple mineral assemblages (Santos et al., 1996) in regards with both clay minerals (essentially illite+smectite, with a subsidiary presence of kaolinite) and the associated non-clay minerals (essentially quartz + K feldspar + Na-Ca feldspar, with episodic and discrete presence of dolomite, anhydrite and anatase). The results achieved from the mineralogical studies point out, in what concerns the clay minerals, to a gradual evolution from a smectite+illite+kaolinite composition in the outcrops of the northern sectors of the Argilas de Taveiro to a more illite+kaolinite richer one in the outcrops of the southern sectors, where we can also found a very strong decrease of the smectite cristallinity (Biscaye Index values). We can also find some distinctive aspects from the analysis of the geochemical ratios, the southern sectors (samples RVL and SP) being characterised by higher contents in Al 2 O 3 and Fe 2 O 3 and lower contents in MgO and CaO. The evolution of these textural parameters points out to an increase in clay fraction in the TVR and RVL samples. The behaviour of the technological parameters points out to a clear decrease in almost all these parameters in the SP samples, whereas the opposite occurs in the TVR and RVL samples. Potential Use as Liners in Wastefills - page 4 of 6

5 PAPER G 04 Environment 2010: Situation and Perspectives for the European Union The multivariate data analysis (Principal Components analysis) of the mineralogical and technological parameters allowed to withdraw the following considerations: Factor 1 shows smectite content, SSA, CEC and expandability in front of kaolinite content and density; Factor 2 explains quartz, Na-Ca feldspar and anhydrite contents in front of anatase content; Factor 3 shows illite content in front of K feldspar content. In general terms, we can consider a clear relationship between smectite content and the technological parameters. The cluster analysis confirms the associations observed in the Principal Components analysis: expandability, specific surface area - SSA and cation exchange capacity - CEC are linked with smectite content and well separated from illite and kaolinite contents as well as from density. On the other hand, in what concerns the relationships between the analysed samples, these could be associated into three clusters - one corresponding to the set SP (São Pedro quarry), other corresponding to the set RF (Ribeira de Frades quarry) and another one gathering all the other sets of samples (TVR Taveiro quarry and RVL Reveles quarry). CONCLUSIONS In comparative terms Aveiro clays have mineral and chemical compositions similar to those shown by Taveiro clays. However, differences could be detected on the clays found in various areas of both Aveiro/Vagos and Taveiro regions. Besides this lateral variations, vertical changes could be found also in the clay strata of the quarries. For instance, relatively to the clays from the Taveiro region, clays from Taveiro quarry show layers richer in phyllosilicates than the clays from Ribeira de Frades quarry, nevertheless these clays show some layers richer in smectite (50~60%). In regards to the clays from the Aveiro/Vagos region, clays from Bustos quarry are richer in smectite comparatively to the clays from Vagos and Nariz quarries, where illite is more abundant. In general terms, the studied clays can be considered as good materials to be used as impermeable liners in the waste land-fills. In terms of the comparative appraisal between the different studied clay quarries it was found, from the preliminary results obtained so far, that the clays showing better characteristics for that application are those from Bustos quarries, followed by those from Taveiro and Reveles quarries. REFERENCES Barahona, E. (1974) - Arcillas de ladrillería de la provincia de Granada: evaluación de algunos ensayos de materias primas. PhD Thesis, Granada Univ., Spain, 398pp. Biscaye, P.E. (1965) Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and adjacent seas and oceans. Geol. Soc. Amer. Bull., 76, pp Davis, J.C. (1986) - Statistics and Data Analysis in Geology. Wiley and Sons, New York. Galhano, A.C.; Rocha, F. & Gomes, C. (1999) - Geostatistical analysis of the influence of textural, mineralogical and geochemical parameters on the geotechnical behaviour of the Argilas de Aveiro Formation (Portugal). Clay Minerals, 34, pp Imbrie, J. & Van Andel, T.H. (1964) - Vector analysis of heavy-mineral data. Bull. Geol. Soc. Am. 75, Jöreskob, K.G.; Klovan, J.E. & Reyment, R.A. (1976) - Geological Factor Analysis. Elsevier, Amsterdam. Potential Use as Liners in Wastefills - page 5 of 6

6 Environment 2010: Situation and Perspectives for the European Union PAPER G 04 López-Aguayo, F. & Gonzalez Lopez, M. (1995) - Fibrous clays in the Almazan basin (Iberian range, Spain): Genetic pattern in a calcareous lacustrine environment. Clay Minerals 30, Mellinger, R. M. (1979) - Quantitative X-ray diffraction analysis of clay minerals. An evaluation. Saskatchewan Research Council, Canada, SRC Report G-79: Mezzadri, G. & Saccani, E. (1989) - Heavy mineral distribution in Late Quaternary sediments of the southern Aegean sea: implications for provenance and sediment dispersal in sedimentary basins at active margins. J. Sed. Petrol. 59, Oweis, I.S. & Khera, R.P. (1998) Geotechnology of waste management. PWS Publishing Company, Boston, 472 p. Pevear, D.R. & Mumpton, D.R. (1989) - Quantitative mineral analysis of clays. CMS Workshop Lectures, 1. The Clay minerals Society, Colorado (USA). Reyment, R.A. & Jöreskob, K.G. (1993) - Applied Factor Analysis in the Natural Sciences. Cambridge Univ. Press, Cambridge. Rocha, F. (1993) - Argilas aplicadas a estudos litoestratigráficos e paleoambientais na Bacia Sedimentar de Aveiro. PhD thesis, Univ. Aveiro, 399 pp. Santos, H.; Rocha, F. & Gomes, C. (1996) - Clays for waste disposal liners: comparative appraisal of the relevant properties of smectitic clays from Aveiro and Taveiro (Portugal). In: Advances in Clay Minerals (M. Ortega Huertas, A. Lopez Galindo & I. Palomo Delgado, eds.), Univ. Granada, pp Schultz, L.G. (1964) - Quantitative interpretation of mineralogical composition from X-ray and chemical data for the Pierre Shale. U.S. Geol. Surv. Prof. Paper, 391-C, pp Thorez, J. (1976) - Practical identification of clay minerals. Ed. G. Lelotte, Belgique. Potential Use as Liners in Wastefills - page 6 of 6