Infrared spectroscopy refines chronological assessment, depositional environment and pyrolysis conditions of archeological charcoals

Based on infrared spectral characteristics, six archeological sample sets of charcoals from German (5) and Brazilian (1) sites, covering the time span from the nineteenth century CE to 3950 BCE, were compared to a chronological (present to the fifteenth century BCE) series of Austrian charcoals. A typical chronological trend of several bands (stretch vibrations: O–C–O of carboxylates at 1,585–1,565 and 1,385–1,375 cm⁻¹, C–O carboxylic acids at 1,260–1,250 cm⁻¹) that indicate oxidation and subsequently increasing hydrophilicity (O–H stretch vibration at about 3,400 cm⁻¹) was also contained in the archive samples. Three sample sets fit in the typical band development according to their age. For three sample sets this conformity was not observed. Despite the age of two sample sets (3950–2820 BCE), most charcoals were assigned to the Modern Period. Apart from the high degree of carbonization, anaerobic depositional conditions over a longer period of time seem to contribute to the surprising conservation. Non-removable mineral components in charcoals, as observed in a third sample set, strongly influence infrared band intensities and positions of organic compounds. The role of inorganic components in terms of charcoal aging, and the information we can obtain from spectral characteristics in an archeological context, are discussed.

Investigations of biological processes in Austrian MBT plants

Mechanical biological treatment (MBT) of municipal solid waste (MSW) has become an important technology in waste management during the last decade. The paper compiles investigations of mechanical biological processes in Austrian MBT plants. Samples from all plants representing different stages of degradation were included in this study. The range of the relevant parameters characterizing the materials and their behavior, e.g. total organic carbon, total nitrogen, respiration activity and gas generation sum, was determined. The evolution of total carbon and nitrogen containing compounds was compared and related to process operation. The respiration activity decreases in most of the plants by about 90% of the initial values whereas the ammonium release is still ongoing at the end of the biological treatment. If the biogenic waste fraction is not separated, it favors humification in MBT materials that is not observed to such extent in MSW. The amount of organic carbon is about 15% dry matter at the end of the biological treatment.

Determination of MBT-waste reactivity - An infrared spectroscopic and multivariate statistical approach to identify and avoid failures of biological tests

The Austrian Landfill Ordinance provides limit values regarding the reactivity for the disposal of mechanically biologically treated (MBT) waste before landfilling. The potential reactivity determined by biological tests according to the Austrian Standards (OENORM S 2027 1-2) can be underestimated if the microbial community is affected by environmental conditions. New analytical tools have been developed as an alternative to error-prone and time-consuming biological tests. Fourier Transform Infrared (FT-IR) spectroscopy in association with Partial Least Squares Regression (PLS-R) was used to predict the reactivity parameters respiration activity (RA(4)) and gas generation sum (GS(21)) as well as to detect errors resulting from inhibiting effects on biological tests. For this purpose 250 MBT-waste samples from different Austrian MBT-plants were investigated using FT-IR spectroscopy in the mid (MIR) and near infrared (NIR) area and biological tests. Spectroscopic results were compared with those from biological tests. Arising problems caused by interferences of RA(4) and GS(21) are discussed. It is shown that FT-IR spectroscopy predicts RA(4) and GS(21) reliably to assess stability of MBT-waste materials and to detect errors.

Reproducibility of Fourier transform infrared spectra of compost, municipal solid waste, and landfill material

The reproducibility of infrared spectra from different waste materials such as compost, mechanically-biologically treated (MBT) municipal solid waste, and landfill materials was investigated. Reproducibility tests focused mainly on infrared spectra and parameter prediction from the spectrum developed for composts and MBT-waste, as well as band height ratio measurement for landfill materials in terms of practical applications. Compared to compost and landfill material, the reproducibility of infrared spectra from MBT-waste was considerably lower. Accordingly, sample preparation was modified and maximum mean deviation was minimized from 8.3% to 4.2%. The number of required spectra replicates was determined in consideration of practical aspects such as parameter prediction for composts and MBT-waste and the measurement of band height ratios (2925/1630 cm(-1)) of landfill materials. For composts two-fold measurements and for MBT-waste and landfill materials three-fold measurements were considered appropriate.

Investigation of 15-year-old municipal solid waste deposit profiles by means of FTIR spectroscopy and thermal analysis

Five profiles of a 15-year-old bank containing over three weeks composted municipal solid waste were characterized by means of different parameters habitually applied in waste management (loss on ignition, total organic carbon, total nitrogen, NH(4)-N, pH), and in addition by humic acid determination, FTIR spectroscopy and thermal analysis. Stabilization processes are revealed by humic acid contents. Over the 15 year period organic matter had developed in various ways. Highest humic acid contents were found at 0.5 m below the surface. Below 1.0-1.5 m anaerobic conditions dominated causing a strong decline of humic acid concentrations. Despite similar contents of organic matter at 0.5 m and at 3.0 m organic matter quality differed. These differences were verified by infrared spectroscopic investigations and thermal analyses (differential scanning calorimetry DSC). The spectral pattern of 15-year-old profile samples (municipal solid waste including the biogenic fraction) was compared to current municipal solid waste and abandoned landfill materials. Current municipal solid waste samples comprised different degradation stages from fresh materials to stabilized waste, suitable for landfilling according to Austrian standards. Municipal solid waste originating from abandoned landfills closed in the seventies represented stable material. Principal component analysis was performed to detect similarities and differences. It is evident that the profile samples constitute a particular group in between municipal solid waste and abandoned landfill material. Some differences can be attributed to the divergent composition of municipal solid waste in the eighties when the organic fraction was not separated. Otherwise, landfill materials from the seventies with the same composition regarding the organic fraction were deposited together with construction waste. Heat flow curves (DSC profiles) of municipal solid waste, representing different decomposition stages, illustrate the development of enthalpies and reveal the status of the profile samples. It is evident that mechanical-biological pretreatment leads to a faster stabilization of waste organic matter.