Lead fallout fingerprint of the Notre-Dame de Paris fire uncovered

Future studies of environmental samples of soil, air and river sediments can use the geochemical fingerprint to determine lead deposited from the fire. A large part of the Notre-Dame de Paris (NDdP) cathedral roof and spire was constructed of lead, and it was estimated that 150 kg of lead was spread during the fire by one study, with another estimating 1 tonne of lead to have fallen within 1 km of the cathedral. The results of this study will enable a more accurate calculation of the environmental spread of lead from the fire across Paris, and the amount deposited within the environment.

To discriminate the potential environmental impact of the fire from other lead pollution sources in the urban environment, it is necessary to define the fire dust’s geochemical signature. However, no dust samples from the fire plume of the NDdP cathedral fire were collected at the time. The researchers sought to determine the geochemical fingerprint of lead pollution in the NDdP fire dust, by developing an innovative sampling and dust analysis approach after the event.

The methodological approach, and results of this research, offer new ways to study lead in landmarks, for both historical purposes and environmental impact evaluation purposes, as historical buildings are potential sources of lead pollution in urban settings.

The researchers collected dust samples from wood, metal, glass and fabric surfaces on both the ground and first floor of the NDdP, from June 2019 to February 2020 – when access was possible, after the fire on the 15^th April 2019. The 23 samples (dust, dust and fibre, crust, and painting) taken from inside the NDdP were analysed for their elemental composition, and for the presence of four lead (elemental symbol, Pb) isotopes: 204, 206, 207 and 208.

Steps were taken to calculate which of the dust sample sources were most representative of the fire emission dust, starting with binocular observations of samples, after which elemental analysis data was investigated to note any substrate contamination from surfaces. From these steps, researchers found the most representative samples of the fire dust were those collected from wooden surfaces within the cathedral, which had very consistent elemental content.

To further refine the samples used to determine the fire dust signature the researchers then examined the impact of location of the wooden substrates, versus the Pb isotopic ratios within the samples. The researchers noted that dust samples from wooden surfaces on the first floor were most representative of the fire dust. The elemental signature of the NDdP fire was identified from the dust fraction of the nine samples collected on wood furniture on the first floor of the cathedral, the Pb concentration range of these being 70.9 to 281.6 g kg^-1 (median: 181 g kg⁻¹).

The researchers found the geochemical fingerprint of the fire dust from wooden surfaces of NDdP to be very different from the major urban lead source in Paris. The NDdP fire lead isotope ratio signature was found to contain the following lead isotope ratio median values: 206Pb/207Pb ratio: 1.16738, 208Pb/206Pb ratio: 2.09875, 206Pb/204Pb ratio: 18.252and 208Pb/204/Pb ratio: 38.307.

Metallic lead samples were taken from joints in the structures of nearby Chartres Cathedral and Sainte Chapelle Paris, of similar construction age to NDdP to determine the extent of the medieval Pb isotopic signature. In the future, this NDdP lead fingerprint will enable determination of the contribution of the fire to Paris’ lead pollution, and of the real extent of the area affected by the lead-containing dust plume.

Finally, the study also showed that the geographical origin of the medieval lead used to construct the spire and roof of the NDdP is the Cartagena mining district, Murcia, Spain.

Source:

Briard, J., Ayrault, S., Roy-Barman, M., Bordier, L., L'Héritier, M., Azéma, A., Syvilay, D. and Baron, S. (2023). Determining the geochemical fingerprint of the lead fallout from the Notre-dame de Paris fire: Lessons for a better discrimination of chemical signatures. Science of The Total Environment, 864: 160676.

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“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.

Notes on content:

The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.