**1. Introduction**

132 Multivariate Analysis in Management, Engineering and the Sciences

approach applied. Federal University of Minas Gerais

2008.

[12] Melo, P. G. (2012). Production and characterization of obtained from Macaúba (Acrocomia aculeata). Master degree thesis. Univesity of Federal of Uberlandia – Brazil. [13] Atadashi, I. M., Aroua, M. K., & Aziz, A. A. (2010). High quality biodiesel and its diesel engine application: A review. Renewable and Sustainable Energy Reviews, 14(7), 1999-

[14] Mingoti, S. A., (2007). Data analysis through methods of multivariete statistical

Ageing and deterioration of materials are key processes within the perpetual conversion of organic and inorganic matter. As far as natural cycles of organic substances are concerned a balance between syntheses, metabolic products, degradation and recycling can be expected. With respect to inorganic materials, weathering is the dominant natural process of ageing. It comprises transformation of chemical compounds and is caused by abiotic and biotic factors. The formation of new mineral phases closes the loop. Anthropogenic activities influence the well-balanced metabolism due to the increased consumption of resources and the inherent accelerated turnover rate. This development is paralleled by a relevant environmental impact caused by increasing concentrations of metabolic products. Especially greenhouse gases have become a crucial topic due to their global effect and the contribution to climate change. The fate of carbon, a key element in the global cycle, therefore attracts much attention [1-4]. Carbon sequestration and minimisation of gaseous emissions such as CO2 and methane are promoted to decelerate the turnover. Deterioration and degradation are not only paralleled in many cases by the release of harmful substances but also by the loss of valuable resources. Prevention of negative environmental effects and careful use of resources therefore require a responsible management of products, substances and elements. Several elements such as nitrogen, phosphorus and sulphur that are released as different compounds during degradation of organic matter are in the focus of interest [5]. The ambivalence being both nutrient and pollutant has led to several techniques of resource recovery [6].

Ageing of materials or products implies changes of the original state, but it does not necessarily only comprise deterioration or degradation. Ageing can also mean formation of new substances and stabilisation. In some cases this effect is desirable. Ageing of

© 2012 Smidt et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Smidt et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

incineration ash and slag leads to carbonation [7, 8]. With respect to organic matter humic substances are built up resulting in a stable organic fraction with low turnover rates. These natural processes that come along with material ageing were adopted for technical applications, e.g. humification in the course of composting.

Ageing and Deterioration of Materials in the Environment – Application of Multivariate Data Analysis 135

features can be extracted by multivariate data analysis. Spectroscopic methods are widely used due to many advantages, e.g. easy handling, robustness, complex information.

The thermal behaviour of any substance depends on chemical and physical properties. Complex materials contribute with all components to a specific thermal pattern. STA comprises thermogravimetry (TG) and differential scanning calorimetry (DSC). Additionally the released gaseous compounds are recorded in the coupled mass spectrometer. With TG the mass loss of the material is measured during combustion. DSC measurements result in a heat flow curve indicating exothermic and endothermic reactions of the material during combustion. The enthalpy can be calculated by integration of the area below the heat flow profile and a baseline. The variation of combustion parameters regarding temperature range, heating rate, isothermal heating and gas flow, oxidative or pyrolytic conditions leads to different information about the sample. In material sciences thermal analysis is widely used for quality control. In general, distinct temperatures are in the focus of interest, e.g. melting and crystallisation temperature. The application of thermal analysis has been extended during the last decade. TG- and DSC-profiles also lead to comprehensive information as spectra do. Both FT-IR spectroscopy and STA have proven to be adequate tools for the characterisation and quality assessment of complex materials such as waste and soils [14-20]. The extensive use of these methods in this field is also a merit of multivariate data analysis. Based on this approach much information can be extracted from

Multivariate data analysis is an indispensable tool for data evaluation in practice.

a huge data pool generated by FT-IR spectroscopy and STA.

**2.1. FT-IR spectroscopy and simultaneous thermal analysis** 

FT-IR spectra of landfill samples were recorded by a Bruker Alpha® (Bruker, Germany) instrument in the mid infrared area (4000 cm-1 to 400 cm-1) in the attenuated total reflection mode (ATR). For the milled lignocellulosic materials the ATR-FT-IR spectra were collected by a Bruker Vertex® with a Pike MIRacle™ ATR device in the wavenumber range from 4000 cm-1 to 600 cm-1, at 4 cm-1 resolution averaging 32 scans. The milled sample was homogenised and directly applied on the ATR reflection module with a diamond crystal providing a measuring area of approximately 4 mm² and a pressure applicator. Twenty four scans per spectrum were collected at a resolution of 4 cm-1 and corrected against ambient air as background. The average of four spectra (maximum deviation of the four spectra from the average spectrum < 5%) was vector normalised prior to multivariate data analysis.

Spectra treatment and data evaluation were carried out using the OPUS software.

Thermal analyses were carried out with a STA 409 CD Skimmer instrument (Netzsch GmbH) in an Al2O3 pan with the following combustion parameters: temperature range 30 – 950 °C, heating rate 10 °C·min-1, gas flow 150 ml·min-1 (80% He and 20% O2), sample amount 16.00 mg. The pyrolysis of wood powder was carried out at different temperatures (200, 300, 350, and 600 °C) under oxygen-free conditions (100% He) with a heating rate of 10 °C·min-1 and isothermal treatment for 20 min. After oxidative combustion of the pyrolysed wood

**2. Methods** 

On the one hand natural processes serve as a model for anthropogenic activities with regard to the closed loop of material recycling, especially in the field of organic substances [9]. On the other hand every endeavour is made to prevent or retard the natural ageing, deterioration and degradation process of materials and to maintain a constant quality of products by adequate measures. There are several options to achieve this objective: modification of biogenic materials, treatment of the surface and application of chemical substances against microbial deterioration and ageing by abiotic factors. Although abiotic factors play a relevant role for ageing and deterioration of organic materials, biological processes dominate. Inorganic materials are primarily affected by chemical and physical attacks, but some specialised microbial communities are capable of promoting the ageing process of inorganic components. The environmental milieu plays a crucial role as it determines both biological and chemical reactions. Historical and archaeological finds owe their preservation to conditions that prevented or delayed deterioration.

This study reports on natural ageing and degradation processes of organic matter and ageing of inorganic materials over weeks, years, decades and centuries. The questions to be answered focus on two main aspects: the environmental impact by ageing and deterioration of organic and inorganic matter and the proof of resistance of organic materials against biological degradation which is a main concern in material sciences to maintain the quality of products [10-12]. Ageing and deterioration can be described by many parameters. They focus on chemical and physical changes of the material by which the process is paralleled. In some cases, especially for product control, a single parameter might be sufficient to verify the ageing of materials [13]. For an overall characterisation of the state of deterioration those analytical methods are advantageous that provide a "fingerprint" of the material. FT-IR spectroscopy and STA were applied to reveal material characteristics and their changes over time under different environmental conditions.

FT-IR spectroscopy is based on the interaction of infrared radiation with matter. Infrared radiation provides the energy for molecule vibrations that become visible as absorption bands. The plot of wavenumbers (energy) within a defined range vs. band intensities results in the spectrum. Infrared spectra describe materials by the unique pattern and provide information on material chemistry. Band intensities depend on the concentration of the compound and the molar decadic absorption coefficient that is reflected in the spectrum and on individual properties of the functional group. Most molecules are infrared active and represented by diverse bands due to different types of molecule vibrations. They are characterised by a typical energy level and are therefore found at defined wavenumbers. The molecule skeleton and other functional groups influence the band position and can cause a band shift. Whereas pure substances show distinct bands that can be attributed to functional groups, complex materials feature broad and overlapping bands that are often not assignable. However, the material shows a "fingerprint". The information of underlying features can be extracted by multivariate data analysis. Spectroscopic methods are widely used due to many advantages, e.g. easy handling, robustness, complex information. Multivariate data analysis is an indispensable tool for data evaluation in practice.

The thermal behaviour of any substance depends on chemical and physical properties. Complex materials contribute with all components to a specific thermal pattern. STA comprises thermogravimetry (TG) and differential scanning calorimetry (DSC). Additionally the released gaseous compounds are recorded in the coupled mass spectrometer. With TG the mass loss of the material is measured during combustion. DSC measurements result in a heat flow curve indicating exothermic and endothermic reactions of the material during combustion. The enthalpy can be calculated by integration of the area below the heat flow profile and a baseline. The variation of combustion parameters regarding temperature range, heating rate, isothermal heating and gas flow, oxidative or pyrolytic conditions leads to different information about the sample. In material sciences thermal analysis is widely used for quality control. In general, distinct temperatures are in the focus of interest, e.g. melting and crystallisation temperature. The application of thermal analysis has been extended during the last decade. TG- and DSC-profiles also lead to comprehensive information as spectra do. Both FT-IR spectroscopy and STA have proven to be adequate tools for the characterisation and quality assessment of complex materials such as waste and soils [14-20]. The extensive use of these methods in this field is also a merit of multivariate data analysis. Based on this approach much information can be extracted from a huge data pool generated by FT-IR spectroscopy and STA.
