M. Statheropoulos

Principal component and canonical correlation analysis for examining air pollution and meteorological data

Five years data on CO, NO, NO2, O3, smoke and SO2 concentrations recorded at oneair-pollution monitoring station in the city of Athens were analysed using principal component analysis(PCA). Separate analyses were undertaken for summer and winter periods. PCA was also applied tometeorological data concerning relative humidity, temperature, sunshine duration, wind velocity and winddirection. It was found that the main principal components extracted from the air pollution data wererelated to gasoline combustion, oil combustion and ozone interactions. The most prominent principalcomponents from the meteorological data were related to dry conditions (summer period) and high-speedsothwestern winds (for both periods). Finally, canonical correlation analysis determined relationshipsbetween the two different data sets. The main relationship was between total pollution and high humidity incombination with the low-velocity wind.

Quantitative thermogravimetric-mass spectrometric analysis for monitoring the effects of fire retardants on cellulose pyrolysis

Abstract The effects of two fire retardant materials, (NH 4 ) 2 SO 4 and (NH 4 ) 2 HPO 4 , on cellulose pyrolysis studied using thermogravimetry-mass spectrometry (TG-MS) analysis. In order to determine quantitatively H 2 O and CO 2 during pure and fire retarded cellulose pyrolysis, the MS signal was calibrated using KHCO 3 decomposition. The MS signal calibration in relation to the flow stability through TG-MS interface was examined. The influence of the TG furnace temperature on MS signal, and the effects of heat and mass transfer phenomena were also discussed. Furthermore, the criteria for evaluating the effectiveness of the fire retardant compounds on cellulose pyrolysis were examined. Both fire retardant compounds resulted in the increase of the non-combustible pyrolysis products, such as H 2 O and CO 2 , and char. Low levels of levoglucosan were recorded. It appears that in the presence of the fire retardant compounds a relative increase of levoglucosenone in the evolved gases is observed. Finally, the effects of the fire retardants on the pyrolysis mechanism were discussed.

Combined chemical and optical methods for monitoring the early decay stages of surrogate human models.

As the body decays shortly after death, a variety of gases and volatile organic compounds (VOCs) constantly emanate. Ethical and practical reasons limit the use of human corpses in controlled, time-dependent, intervening experiments for monitoring the chemistry of body decay. Therefore the utilization of pig carcasses serves as a potential surrogate to human models. The aim of this work was to study buried body decay in conditions of entrapment in collapsed buildings. Six domestic pigs were used to study carcass decay. They were enclosed in plastic body bags after being partially buried with rubbles, resembling entrapment in collapsed buildings. Three experimental cycles were performed, employing two pig carcasses in each cycle; VOCs and inorganic gases were measured daily, along with daily visible and thermal images. VOCs were collected in standard sorbent tubes and subsequently analyzed using a Thermal Desorption/Gas Chromatograph/high sensitivity bench-top Time-of-Flight Mass Spectrometer (TD/GC/TOF-MS). A comprehensive, stage by stage, detailed information on the decay process is being presented based on the experimental macroscopic observations, justifying thus the use of pig carcasses as surrogate material. A variety of VOCs were identified including almost all chemical classes: sulfur, nitrogen, oxygen compounds (aldehydes, alcohols, ketones, acids and esters), hydrocarbons, fluorides and chlorides. Carcasses obtained from a pig farm resulted in more sulfur and nitrogen cadaveric volatiles. Carbon dioxide was by far the most abundant inorganic gas identified along with carbon monoxide, hydrogen sulfide and sulfur dioxide. Visual monitoring was based on video captured images allowing for macroscopic observations, while thermal camera monitoring which is mostly temperature dependent, resulted in highlighting the local micro-changes on the carcasses, as a result of the intense microbial activity. The combination of chemical and optical methods proved very useful and informative, uncovering hidden aspects of the early stages of decay and also guiding in the development of combined chemical and imaging methods for the detection of dead bodies.

Thermal degradation of Pinus halepensis pine-needles using various analytical methods

Abstract The analytical methods of DSC, TG, DI-MS, Py-GC-FID, Py-GC-MSD were used to study the thermal degradation of Pinus halepensis pine-needles. As was shown by DSC measurements endotherm peaks could be attributed to the desorption of high volatility compounds, moisture, softening and/or melting of the waxy constituents of pine-needles; as well as to the degradation of hemicellulose and cellulose. Exotherm peaks could be attributed to the pyrolysis of lignin and char recombination. These results were reconfirmed by DTG curve. In addition, the DI-MS measurements showed, through the presence of certain mass peaks, the existence of volatile degradation products which can be related to the degradation pathways observed by DSC and TG. Py-GC-FID proved that the evolution of organic degradation products commences at 200–250 °C and has its maximum evolution rate between 350 and 450 °C. Py-GC-MSD analysis of the flash pyrolysis products at 400 °C identified a number of organic compounds and CO 2 .

Chemometric methods for studying the effects of chemicals on cellulose pyrolysis by thermogravimetry–mass spectrometry

Abstract Chemometric methods were used for extracting information out of the mixture mass spectra recorded in a thermogravimetric–mass spectrometric (TG–MS) analysis. Principal Component Analysis (PCA) and Discriminant Rotation (DR) were applied for studying the effects of fire retardants on the gases evolved during thermal degradation of cellulose. The chemicals (NH 4 ) 2 SO 4 , (NH 4 ) 2 HPO 4 and a commercial retardant (Fire Trol) were used as fire retardants. PCA and DR resulted in four factors discriminating between untreated cellulose and cellulose treated with fire retardants. For the interpretation of the factors the rotated discriminant spectra were used. For estimating the effects of the fire retardants, the score plot in the first two discriminants space was used. It was shown that in all cases the retardation action was based on various factors such as: the increase of CO 2 evolution produced by dehydration of cellulose, the relative decrease of very flammable volatile products (carbonyl compounds, reduced furans and pyranone derivatives) and the increase of levoglucosenone produced by dehydration of levoglucosan. A differentiation between the effects of (NH 4 ) 2 SO 4 and the other two retardants was also observed and it concerned mainly the production of phenol derivatives and acetic acid.

The effect of salt and oxide-hydroxide additives on the pyrolysis of cellulose and Pinus halepensis pine needles

Abstract Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) were used to study the effects of various salts and oxide-hydroxide additives on the pyrolysis of cellulose and Pinus halepensis pine needles. (NH4) 2 HPO 4 , NaH 2 PO 4 , (NH 4 ) 2 SO 4 , NaHCO 3 , KHCO 3 , (COONa) 2 , Ca(OH) 2 and Na 2 O.CaO were used as additives at concentrations of 4% w/w and 10% w/w. DSC and TGA showed that the addition of (NH 4 ) 2 HPO 4 , NaH 2 PO 4 and (NH 4 ) 2 SO 4 on cellulose causes a significant shift to lower pyrolysis temperatures, i.e. 50°C to 80°C, as well as a significant increase in char residues. The effect of NaHCO 3 , KHCO 3 , and (COONa) 2 on the pyrolysis of cellulose was also found to be significant in terms of the DSC profile, while the increase in char residues was moderate. In contrast the effect of Ca(OH) 2 and Na 2 O·CaO on the pyrolysis of cellulose was found to be minor, under the above-mentioned criteria. The above chemicals, tested as fire retardants, have shown minor effects on the pyrolysis of Pinus halepensis pine needles. Some changes, however, were noticed in the solid pyrolysis residues, particularly when (NH 4 ) 2 HPO 4 and (NH 4 ) 2 SO 4 were used.

Application of ion mobility spectrometry for the detection of human urine

The aim of the present study was to evaluate the suitability of ion mobility spectrometry (IMS) for the detection of human urine as an indication of human presence during urban search and rescue operations in collapsed buildings. To this end, IMS with a radioactive ionization source and a multicapillary column was used to detect volatile organic compounds (VOCs) emitted from human urine. A study involving a group of 30 healthy volunteers resulted in the selection of seven volatile species, namely acetone, propanal, 3-methyl-2-butanone, 2-methylpropanal, 4-heptanone, 2-heptanone and octanal, which were detected in all samples. Additionally, a preliminary study on the permeation of urine volatiles through the materials surrounding the voids of collapsed buildings was performed. In this study, quartz sand was used as a representative imitating material. Four compounds, namely 3-methyl-2-butanone, octanal, acetone and 2-heptanone, were found to permeate through the sand layers during all experiments. Moreover, their permeation times were the shortest. Although IMS can be considered as a potential technique suitable for the detection, localization and monitoring of VOCs evolved from human urine, further investigation is necessary prior to selecting field chemical methods for the early location of trapped victims.

Thermal analysis of Pinus halepensis pine-needles and their main components in the presence of (NH4)2HPO4 and (NH4)2SO4

DSC and TG were used to study the effects of fire retardants on the pyrolysis of Pinus halepensis pine-needles and their components (cellulose, lignin and extractives). (NH4)2HPO4 and (NH4)2SO4 were used as fire retardants at the 10% w/w concentration level. The TG results showed that the mass loss profile of pine-needles resembles those of lignin and extractives. The DSC curves showed that in the presence of fire retardants there is a shift to lower pyrolysis temperatures for cellulose. In addition, there is an increase in the pyrolysis residue for both cellulose and pine-needles. Minor or negligible effects were observed for lignin and extractives in the presence of the retardants.

Temporal profiling of human urine VOCs and its potential role under the ruins of collapsed buildings

Context: The scent profile of human urine was investigated as potential source of chemical markers of human presence in collapsed buildings after natural or man-made disasters. Objective: The main goals of this study were to build a library of potential biomarkers of human urine to be used for the detection of entrapped victims and to further examine their evolution profile in time. Materials and methods: Headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to detect and identify the volatile organic compounds (VOCs) spontaneously released from urine of 20 healthy volunteers. Additionally, the evolution of human urine headspace during four days storage at room temperature was investigated. Results: 33 omnipresent species with incidence higher than 80% were selected as potential urine markers. The most represented chemical classes were ketones with 10 representatives, aldehydes (7 species) and sulfur compounds (7 species). The monitoring of the evolution of the urine scent demonstrated an increase in the emission of 26 omnipresent urinary volatiles (rise from 36% to 526%). The highest increase was noted for dimethyldisulfide and dimethyltrisulfide (fivefold increase) and 3-methyl-2-butanone, 4-methyl-2-pentanone and 3-hexanone (fourfold rise). Only three compounds exhibited decreasing trend; dimethylsulfone, octanal and propanal. Conclusion: The ubiquitous urine VOCs identified within this study create a library of potential markers of human urine to be verified in further field studies, involving portable and sensitive instruments, directly applied in the field.

The trapped human experiment

This experiment observed the evolution of metabolite plumes from a human trapped in a simulation of a collapsed building. Ten participants took it in turns over five days to lie in a simulation of a collapsed building and eight of them completed the 6 h protocol while their breath, sweat and skin metabolites were passed through a simulation of a collapsed glass-clad reinforced-concrete building. Safety, welfare and environmental parameters were monitored continuously, and active adsorbent sampling for thermal desorption GC-MS, on-line and embedded CO, CO(2) and O(2) monitoring, aspirating ion mobility spectrometry with integrated semiconductor gas sensors, direct injection GC-ion mobility spectrometry, active sampling thermal desorption GC-differential mobility spectrometry and a prototype remote early detection system for survivor location were used to monitor the evolution of the metabolite plumes that were generated. Oxygen levels within the void simulator were allowed to fall no lower than 19.1% (v). Concurrent levels of carbon dioxide built up to an average level of 1.6% (v) in the breathing zone of the participants. Temperature, humidity, carbon dioxide levels and the physiological measurements were consistent with a reproducible methodology that enabled the metabolite plumes to be sampled and characterized from the different parts of the experiment. Welfare and safety data were satisfactory with pulse rates, blood pressures and oxygenation, all within levels consistent with healthy adults. Up to 12 in-test welfare assessments per participant and a six-week follow-up Stanford Acute Stress Response Questionnaire indicated that the researchers and participants did not experience any adverse effects from their involvement in the study. Preliminary observations confirmed that CO(2), NH(3) and acetone were effective markers for trapped humans, although interactions with water absorbed in building debris needed further study. An unexpected observation from the NH(3) channel was the suppression of NH(3) during those periods when the participants slept, and this will be the subject of further study, as will be the detailed analysis of the casualty detection data obtained from the seven instruments used.