Patrick Ausset

Embryonic sulphated black crusts on carbonate rocks in atmospheric simulation chamber and in the field: role of carbonaceous fly-ash

Experimental conditions characteristic of the urban pollution in many European cities over the last decades were reproduced in a simulation chamber in which samples of limestone were exposed for a period of 12 months, both naked or sprinkled with carbonaceous fly-ash. In agreement with the findings reported in the literature the fly-ash emitted by heavy fuel combustion are highly reactive, undergoing chemical and morphological transformations which give rise to crystals growth, especially gypsum. The development of gypsum crystals was observed overall in close proximity of fly-ash anchoring them to the limestone surface. Samples of the same limestone exposed in the field in a polluted environment for the same period of time led to similar results. The preliminary mechanisms leading to the genesis of sulphated black crusts in polluted environments were thus highlighted. Because of their roughness the embryonic black crusts increase the development of the crust by trapping new particles. This trapping is also facilitated by the wetness of the stone surface leading to the development of hydrated mineral (gypsum) in the water meniscus between fly-ash and stone surface.

Experimental study of limestone and sandstone sulphation in polluted realistic conditions : The Lausanne Atmospheric Simulation Chamber (LASC)

Abstract The Lausanne Atmospheric Simulation Chamber (LASC) has been constructed with the aim of studying the SO2 effects on different materials. It allows the carrying out of numerous measurements on large stone samples simultaneously and on line. The behaviour of two carbonatic stone types (limestone and sandstone), either naked or covered with fly ash or soot particles, exposed at the following conditions, SO2 = 125 ppb (340 μg m−3), NO2 = 50 ppb (98 μg m−3), relative humidity = 79%, temperature = 13°C, has been studied. This experiment has been carried out over a 1 yr period. It has been observed that SO2 deposition velocity decreases with time and in different ways for each of the two stone types, naked or covered with fly ash or soot particles. During the first four months, the deposition velocity is higher on naked stones; later on, it is higher on the stone samples covered with fly ash. Throughout the experiment the SO2 deposition velocity on stone samples covered with soot particles is lower than on naked samples and those covered by fly ash. Finally, the values of SO2 deposition velocity are confirmed by the chemical analysis of sulphur in the samples. Sulphur is present from the stone surface down to about 0.8 mm depth.

Recording of pre-industrial atmospheric environment by ancient crusts on stone monuments

The interaction between today’s polluted urban atmosphere and materials leads to the formation of sulphated black crusts containing industrial fly-ash. While many historical documents report the existence of polluted air in towns prior to the modern industrial era, such descriptions have not so far been substantiated by any scientific analysis of samples of older interactions. A new approach is proposed, based on the study of crusts found in Arles and Bologna, which formed in the periods 1180–1636, and 1530–1887, respectively. They are grey, mostly calcitic, and contain wood debris and micrometric siliceous or alumino-silicated spherules. The same tracers were also encountered in the smoke from experimental wood fires. This approach confirms the presence of air polluted by wood combustion in the towns of Southern France and Northern Italy during the Medieval up to pre-industrial age. Such information, near to the source, completes the evidence provided in written documents, as well as the data obtainable, farther from the sources, using core samples of glaciers, lakes and marine sediments.

Experimental rapid alteration of basaltic glass: Implications for the origins of atmospheric particulates

Glassy microspherules collected from the plume of Etna volcano show a surprising compositional variability with SiO 2 from 48 to 90 wt%, despite a very homogeneous basaltic source magma (SiO 2 = 48%). This same variability is also observed in individual microspherules from their inner to outer parts. The most plausible hypothesis concerning these compositional variabilities is the interaction of the microspherules with the volcanic gases inside the crater prior to their atmospheric dispersal. In order to study this compositional variability we experimentally exposed basaltic glass to volcanic gases at Etna. The resulting glass composition documents a fundamental alteration mechanism, involving an apparent leaching process that can rapidly form nearly pure silica. Because microspherules erupted directly into the air from lava fountains remain unaltered, the duration of microspherules within a gas plume can explain the chemical variability of glass alteration. A major implication for the origin of glassy atmospheric particulates is that chemical compositions cannot be used as a reliable indicator of their source (e.g., meteoric, volcanic, anthropogenic).

Evidence of pre-industrial air pollution from the Heads of the Kings of Juda statues from Notre Dame Cathedral in Paris.

Pollution originating from wood combustion characterised the urban atmospheres of the past and led to the formation of thin grey crusts on the surface of the stone of monuments. The grey crusts discovered on the Heads of the Kings of Juda statues, which adorned the facade of Notre Dame in Paris from the 13th century until 1792, constitute a material record of the effects of this ancient air pollution. The height at which the statues stood suggests that the effect was not the result of a point phenomenon, but was caused by a generalised pollution of the Paris atmosphere at the time.

Early mechanisms of development of sulphated black crusts on carbonate stone

Publisher Summary Carbonaceous fly-ash, particularly those emitted by heavy fuel oil combustion, has a strong physicochemical reactivity. They contain many sulfured chemical species, in particular sulfates along with metals such as vanadium, iron, and nickel. This chapter describes the role of carbonaceous fly-ash in the nucleation of gypsum crystals and in the development of incipient sulfated black crust on carbonate surface. This study is conducted by comparing simulation chamber data with those obtained in the field. Embryonic black crust forming over 12 months through interaction between carbonaceous fly-ash and samples of Jaumont limestone in the controlled atmosphere of a simulation chamber are compared with those forming in the field on the same carbonate stone, over the same time period in a real polluted atmosphere. The Jaumont limestone samples were placed inside the LASC, either naked or sprinkled with fly-ash. Similarly, Jaumont field samples were collected and examined with ASEM. The chapter discusses the results from both samples and compares them to draw conclusions. On the basis of simulation chamber and field data obtained over 12 months, the study of the morphology, mineralogy, and chemical composition of the deposits and associated neocrystallizations indicates that they represent the first stage of black crust development. The fly-ash appears to play a crucial role in the formation of black crusts because they facilitate the precipitation of gypsum, which constitutes the predominant mineral in the black crusts.

Modelling of the calcareous stone sulphation in polluted atmosphere after exposure in the field

Abstract Parisian Lutetian and Val-de-Loire Turonian Richemont limestone tablets were exposed, sheltered and unsheltered from rain, for up to 3 years in Paris and Tours, respectively. Sulphur concentrations below the stone surfaces were measured from powders obtained by milling the stone in successive steps of 0.1 mm. In tablets exposed to rain, measured sulphur concentration remains equal to the stone background concentration, implying that the sulphur deposited between rain events is leached by the next event. In contrast, in tablets sheltered from rain, the sulphur concentration in the first layer below the stone surface increases non-linearly with time. Sulphation does not, however, penetrate more than 0.2 mm. A sigmoidal Hill curve provides a good fit with changes in measured sulphur concentration over time within the first layer of each sheltered stone. This model reveals a cumulative phenomenon of sulphation, characterized by a saturation level that obstructs deeper penetration of sulphur within the stone. The model shows the same type of time evolution of sulphation for both stones, but with different coefficients; these coefficients are related to the atmospheric environment of exposure and to the different intrinsic properties of each stone.

Characterization of manufactured TiO2 nanoparticles

Technological advances in nanomaterials have allowed the development of new applications in industry, increasing the probability of finding airborne manufactured and engineered nano-objects in the workplace, as well as in ambient air. Scientific studies on health and environmental risks have indicated that airborne nano-objects in ambient air have potential adverse effects on the health of exposed workers and the general population. For regulatory purposes, ambient measurements of particulate matter are based on the determination of mass concentrations for PM10 and PM2.5, as regulated in the European Directive 2008/50/EC. However, this legislation is not suitable for airborne manufactured and engineered nano-objects. Parameters characterising ultrafine particles, such as particle number concentration and size distribution, are under consideration for future health-based legislation, to monitor workplaces and to control industrial processes. Currently, there are no existing regulations covering manufactured airborne nano-objects. There is therefore a clear, unaddressed need to focus on the toxicology and exposure assessment of nano-objects such as titanium dioxide (TiO2), which are manufactured and engineered in large quantities in industry. To perform reliable toxicology studies it is necessary to determine the relevant characteristics of nano-objects, such as morphology, surface area, agglomeration, chemical composition, particle size and concentration, by applying traceable methods. Manufacturing of nanomaterials, and their use in industrial applications, also require traceable characterisation of the nanomaterials, particularly for quality control of the process. The present study arises from the OECD WPMN sponsorship programme, supported by the French Agency for Environmental and Occupational Health Safety (ANSES), in order to develop analytical methods for the characterization of TiO2 nanoparticles in size and count size distribution, based on different techniques to characterize five different manufactured TiO2 nanoparticles. In this study, different measurement techniques have been implemented: Transmission Electron Microscopy (TEM), Scanning Mobility Particle Sizer (SMPS) and Aerodynamic Particle Sizer (APS). The TEM results lead to a relatively good agreement between data from the manufacturer and our characterizations of primary particle size. With regard to the dustiness, the results show a strong presence of agglomerates / aggregates of primary particles and a significant presence of emitted airborne nanoparticles with a diameter below 100 nm (composed of isolated primary particles and small aggregates / agglomerates formed from a few primary particles): the number proportion of these particles varies from 0 to 44 % in the measurement range 14-360 nm depending on the types of powders and corrections of measurements.

Past air pollution recordings on stone monuments: The Heads of the Kings of Juda Statues from Notre-Dame Cathedral (Paris)

Publisher Summary Pollution linked to the combustion of wood is characteristic of the atmosphere of the cities in the past. It led to the development of thin grey crusts on the surface of the stones of monuments. The grey crusts were discovered on the Heads of Kings of Juda Statues, present on the western facade of Notre-Dame in Paris from the 13 th Century to 1792. These thin grey crusts are the material witnesses of the effects of the ancient air pollution, prevalent during the French revolution and the period immediately before it. This chapter focuses on the research conducted on the character and evolution of urban air pollution in the past; and the comparison of results with those derived from studies on the modern industrial black crusts. Several analytical techniques were used to highlight the main physicochemical and mineralogical characteristics of the grey crusts: colorimetric technique, X-ray diffraction, and photon microscopy. Many of the characteristics of the ancient grey crusts of the Heads of Kings of Juda directly contrast with those of the modern day black crusts: color, texture, thickness, and chemicomineralogical nature of the crusts and of the prismatic or spherical particles embedded in the matrix. Diffractometric analysis of the modem black crusts highlights the presence of the same minerals as those found in the ancient crusts of the Heads, but in different proportions greater amounts of gypsum than calcite, followed by quartz and weddellite. A further major difference between the ancient grey crusts and the modern black crusts lies in the kind of particles contained in the gypsum-calcite cement. While the grey crusts only contain the residues of incomplete wood combustion, the modern crusts embed microspheres, which turn out to be fly-ash released into the atmosphere by the combustion of coal or heavy fuel.