The initial atmospheric behavior of radon decay products

The chemical and physical properties of²¹⁸Po immediately following its formation from²²²Rn decay are important in determining its behavior in indoor atmospheres and play a major part in determining its potential health effects. In 88% of the decays, a singly charged, positive ion of²¹⁸Po is obtained at the end of its recoil path. These ions can interact with water vapor or other volatile organic compounds (VOCs) that may exist in indoor air. The ions can be neutralized by 3 different mechanisms, small-ion recombination, electron transfer, and electron scavenging. In typical indoor air, the ion will be rapidly neutralized by transfer of electrons from lower ionization potential gases such as NO₂. The neutral molecule can then become incorporated in ultrafine particles formed by the radiolytic processes in the recoil path. These particles will typically be formed by the presence of the air ions produced by the passage of the emitted -particle through ion-induced nucleation. In addition these energetic ions can react with water molecules to produce hydroxyl radicals. Thus, the decay of the radon nucleus produces a variety of effects and can result in changes in the size of the radioactive species that includes the radon progeny.     

Analysis of building stone decay by computer assisted IR spectroscopy

The development of an automatic identification system for infrared spectra of inorganic sulphates and the first results are briefly described.     

Monitoring of atmospheric pollutants by passive sampling for the protection of historic buildings and monuments

When considering the various possibilities to assess the effects of SO2 and NO2 on historic buildings and monuments, a distinction can be made according to the completeness of the scope of the assessment itself. A first approach can be limited to gathering data as they become available through the official bodies established under air quality legislation. This approach is based on a single point measurement where a "general purpose" monitoring station is located, often quite far from the monument to protect and often without investigating local and temporal variations. A more comprehensive assessment should include a generalisation that covers the territory. This can be made on the basis of the knowledge of the spatial distribution of concentrations and the knowledge of the causes of air pollution. Passive samplers allow the measurement of air quality in numerous sites and to assess the pollutant spatial distribution over a large area with a high resolution. As an application of the method, the spatial distribution of SO2 and NO2 in the city of Siracusa, Sicily, Italy, has been studied to identify areas of high deposition fluxes in relation to the protection of buildings and monuments of the historic centre.     

Evaluation of polymers for conservation treatments of outdoor exposed stone monuments. Part I: Photo-oxidative weathering

The commercial acrylic polymers, Paraloid B72 and Paraloid B67, and a silicon-based product, Dri-Film 104, commonly used as water repellents/consolidants in the restoration of stone artefacts, have been tested to evaluate their performances when submitted to ageing, simulating the outdoor conditions of treated stone. After full characterization, the three polymers were applied as thin films on slides, as thick film on petri dishes and on marble by brush or by imbibition and the resulting samples were submitted to photo-oxidative weathering (λ = 340 nm). The weathering evolution was checked by ultrasonic and colorimetric measurements and by FT-IR, NMR and SEC determinations. Removability tests were also performed. All the polymers underwent irreversible modifications with reduction of their conservative properties, colour change and, above all, impossibility of their complete removal.     

Loss of resistance to decay of scots pine heartwood in a biologically active environment

The heartwood ofPinus sylvestris (Scots pine or Baltic redwood) is known to contain natural chemicals (extractives) that confer a measure of resistance to decay by cellulolytic and lignolytic wood-destroying fungi. It is also known that the heartwood nearest the pith (juvenile heartwood) is frequently less resistant than the mature heartwood and can become rapidly decayed under appropriately damp conditions. Window joinery in the UK is manufactured substantially fromP. sylvestris and the extent of natural resistance to decay of the heartwood, and of any changes that may occur with time in service, is therefore of great practical and economic relevance. Investigations have been carried out at PRL in which small blocks (20 × 5 × 5 mm) have been excised from the relevant zones of new, joinery-grade timber and from timber previously in service as window joinery for periods of up to 10 yr. After sterilization, the blocks were exposed to attack byConiophora puteana (FPRL No HE) for a period of 4 wk and the weight loss of the blocks was assessed. Results with new timber confirmed that the mature heartwood is significantly more durable than the juvenile heartwood, which in turn is significantly more durable than the sapwood (0.1% probability level in each case). With timber from service, different results were obtained. From regions protected by paint and remote from the effects of water penetration via the joint, the mature heartwood was still more durable than juvenile heartwood, but the difference was less significant (5% probability level). However in the region of the joints, which are subject to wetting and the microbial colonization that accompanies it, the mature heartwood had become significantly less durable than the mature heartwood from the protected region. Furthermore, it was no longer more durable than the juvenile wood associated with it. The precise mechanism of the change in durability of the mature wood is still not known. Leaching of water-soluble extractives is thought unlikely since the main extractives present inP. sylvestris (pinosylvins) are not markedly water-soluble and in any case, although water enters the timber components in the liquid phase, subsequent loss occurs in the vapor phase and not by mass flow. It seems more likely that the effect is a result of the activity of the mixed microflora of bacteria, yeasts, molds, and blue-stain fungi that have already been shown to be the early colonizers of pine joinery in service. Possibly the microbial activity serves to detoxify the inhibitory extractives or to render the heartwood more susceptible to cellulolytic and lignolytic systems by some nutritional or microstructural means.     

Investigation by solid-phase microextraction and gas chromatography/mass spectrometry of secondary metabolites in lichens deposited on stone monuments

Lichens are ubiquitous organisms formed by symbiotic associations of fungal hyphas and algae that also grow under often extreme environmental conditions. They produce secondary metabolites, the so-called lichen substances, whose structural characterization can give an important contribution to lichen taxonomy. Lichens are also widely employed as biomonitors of atmospheric pollution; being epiphyte organisms they tend, in fact, to accumulate exogenous compounds. Moreover, it could be questioned if the environmental stress alters their secondary metabolites production. Therefore, a new strategy for the analysis of the organic substances absorbed or metabolized by lichens has been developed. This method exploits the dry solid-phase microextraction (SPME) headspace technique coupled with gas chromatography/mass spectrometry (GC/MS). Lichens coating the stone surfaces of monuments, located in small towns between high mountains and far away from urban environments, have been investigated. In the field of cultural heritage, this study can contribute to the knowledge of the state of conservation of outdoor exposed historical monuments.     

New strategies for the synthesis of partially fluorinated acrylic polymers as possible materials for the protection of stone monuments

The conservation of the cultural heritage requires the development of new materials having specific characteristics that encompass particular attention to durability and efficacy. We approached this problem by synthesizing polyacrylic esters containing variable amounts of fluorine in the α-position of the main chain. These products were obtained from the copolymerisation of ammonium 2-fluoroacrylate and acrylic acid. The polyacrylic acids were esterified using different procedures. The polyester characteristics vary in relation to the polymerisation procedures and degree of esterification. The best esterification results, were obtained using a reaction catalyzed by BF₃ or TMSCl. These materials show good properties and are of potential interest for their use as protective agents for stone conservation.     

Evaluation of polymers for conservation treatments of outdoor exposed stone monuments. Part II: Photo-oxidative and salt-induced weathering of acrylic-silicone mixtures

The behaviour of the acrylic-silicone mixture commonly known as Bologna Cocktail, composed of commercial acrylic polymer Paraloid B72 and the silicon-based product, Dri Film 104, extensively employed as stone preservative for monuments in the last thirty years, has been tested on specimens appropriately prepared and submitted to ageing simulating reliable outdoor environment. After chemical characterization, the acrylic-silicone mixture was applied as thin film on slides, as thick film on Petri dishes and on marble by brush or by absorption; the resulting samples were artificially aged by light and saline solution. The chemical modifications were evaluated by FT-IR, NMR and SEC determinations, while preservative properties were tested by removability tests, ultrasonic and colorimetric measurements. The mixture consists of two immiscible phases and the two components have distinctive chemical behaviours, leading - after ageing - to irreversible molecular modifications and loss of conservative properties. The deterioration processes identified through laboratory simulation have been also verified on treated marble surfaces of two Venetian case studies.     

Lichen biodeterioration of ecclesiastical monuments in northern Spain

Seven highly-coloured lichen species belonging to the genera Caloplaca, Candelariella, Aspicilia and Xanthoria from ecclesiastical buildings in northern Spain have been analysed non-destructively by FT-Raman spectroscopy. The vibrational band assignments in the spectra of the specimens, which were still attached to their limestone or sandstone substrata, were accomplished with the assistance of the chemical compositions obtained from wet chemical extraction methods. beta-Carotene was found in all specimens as the major pigment, and the characteristic spectral signatures of calcium oxalate monohydrate (whewellite) and dihydrate (weddelite) could be identified; chemical signatures were found for these materials even in lichen thalli growing the non-calcareous substrata, indicating, probably, that the calcium was provided here from wind-or-rain-borne sources. The Raman spectral biomarkers found in the lichens broadly agreed with the chemical extraction profiles as expected, but the present study indicates that some form of non-destructive taxonomic identification based on Raman spectroscopy was possible.     

Configurations of the free radicals in irradiated polypropylene and the relation of their decay reactions to the molecular motion

Free radicals produced in irradiated polypropylene were studied by the electron spin resonance method. Two temperature regions in which the free radicals decay rapidly were found at around 170°K. and 260°K. The first temperature region corresponds to the γ-dispersion of polypropylene and the second to the β-dispersion. Steric configurations of the free radicals were investigated, and it was concluded that the free radicals trapped in polymer, conformation of which is appreciably twisted from the stable 3₁-helical structure, decay with small-scale motion of the matrix polymer. The decay of free radicals trapped in polymer of less twisted conformation is associated with the large-scale motion of the matrix polymer. Activation energies of decay were found to be 11 kcal./mole at the lower temperature and 48 kcal./mole at the higher temperature. Time constants of the decay reactions were compared with those for molecular motion of the matrix, with results reflecting the relations of the decay of the polymer radicals to molecular motion in the matrix.     

Rate constant for the reaction of nh2 with ozone in relation to atmospheric processes

The absolute rate constant of the reaction between NH₂ and ozone has been measured using a flash photolysis-laser resonance technique and found to be k₄ = 6.3 (=1.0) × 10^?14 cm³ molecule^? s^?1 at room temperature. The Arrhenius expression, determined from measurements in the temperature range 298–380 K is k₄ = 4.2 × 10^?12 exp(?2.5 = 0.5/RT) (E in kcal mole ^?1. The possibility of formation or elimination of nitrogen oxides from the reactions of NH₂ in the atmosphere is examined.     

The importance of the environment on the relative phosphorescence decay times of the xylenes at 77°K

Lifetime measurements on the xylenes in a large selection of crystalline and glassy hydrocarbon and alcoholic media indicate that environmental effects can mask any smaller intrinsic differences among them.     

The decay of 85gZr

The decay of ⁸⁵Zr, produced by the ⁸⁹Y(p, 5n)⁸⁵Zr reaction, has been studied. An ion exchange column was utilized to isolate the Zr activity. Ge(Li) detectors were used for γ-ray singles and γ-γ coincidence measurements. The half-life was determined to be 7.9 ± 0.1 min. A decay scheme for ^85gZr has been proposed, accounting for 98.7% of the total assigned γ-ray intensity.     

The decay of104mAg

The decay of 33 min 2⁺ isomeric state of¹⁰⁴Ag has been studied.¹⁰⁴Ag has been produced following the¹⁰³Rh(, 3n) and¹⁰⁷Ag(, 3n) reactions using 29 and 55 MeV -particles, respectively. The present results indicate that^104mAg decays mainly by EC/⁺ decay. The IT branch for this decay was found to be <0.07% as against the reported value of 33±5%.     

The decay of188Re

The -ray spectra of¹⁸⁸Re decay have been studied by using two Ge/Li/ spectrometers and a three parameters /E-E-T/ List coincidence system. The energies and relative intensities of 52 -rays and cascade relations of 14 -rays are determined. Ten new -rays: 155 /633–478/, 984, 1096, 1463, 1332, 1530, 1574, 1810, 1867, and 1937 keV have been identified. The 155 /633–478/ transition is confirmed and its relative intensity is estimated by means of coincidence experiment. 24 levels of¹⁸⁸Re are assigned. Among those, 6 levels are first put into the decay scheme of¹⁸⁸Re. In addition to 1443 keV and 1937 keV levels, 1685, 1729 and 1965 keV levels are also observed in the decay of¹⁸⁸Ir and other reaction studies. The 1948 level is recently suggested in the¹⁹⁰Os/p, t/¹⁸⁸Os reaction. The 486 keV and 811 keV -transitions are also put into the level scheme of¹⁸⁸Re. The ^– decay branching ratio is deduced.     

The decay of153Gd

The sum peak method has been applied to calculate electron capture probability changes to 97 keV and 103 keV levels in the decay of¹⁵³Gd in different environments, e.g., HClO₄ and HNO₃. The relative and absolute intensities of KX-rays and -rays have been measured using a HPGe detector. In addition to these, electron capture intensities and electron capture decay energies (Q _Ec) have also been calculated.     

Organic content evaluation of corrosion patinas in outdoor bronze monuments

Summary As opposed to inorganic composition, the characterization of organic content in patinas of bronze monuments has been neglected. Analytical pyrolysis coupled with gaschromatographyάss-spectrometry (Py/GC-MS) has been shown to be a valid and rapid technique to identify organic materials in corrosion patina of bronze monuments. In this paper six renaissance Italian outdoor bronze monuments were analyzed in order to determine organic composition of the patina. Results show the presence of both environmental organic compounds and chemicals coming from protective treatment.     

Aldehydes in the atmospheric environment: evaluation of human exposure in the north-west area of Milan

Human exposure to aldehydes has been evaluated in five urban locations and one rural-industrial location in the north-west area of Milan in winter 1999 and in summer 1998–99. Ambient air samples collected on dinitrophenylhydrazine (DNPH)-coated diffusive cartridges were analysed for aldehydes as their DNPH-derivatives. Aldehydes have been identified and their concentration measured via HPLC-UV and LC-APCI-MS negative ion mode methods. During the winter the range of total concentration of aldehydes was 16.7–30.7 μg/m³ at the urban locations and 11.7 μg/m³ at the rural-industrial location. Formaldehyde accounted for 50% of the total amount of carbonyl compounds in all locations; the percentage of acetaldehyde was more variable: 23–38% of the total carbonyls. The contribution of outdoor environment to the average human daily intake of formaldehyde in this area (urban and rural-industrial) is mostly 1–2% of the total human exposure.