Marco Casati , Grazia Rovelli, Luca D’Angelo, Maria Grazia Perrone, Giorgia Sangiorgi, Ezio Bolzacchini, Luca Ferrero

  • Department of Earth and Environmental Sciences (DISAT), University of Milano – Bicocca, Piazza della Scienza 1, 20126 Milano, Italy

Received: November 18, 2014
Revised: January 16, 2015
Accepted: January 26, 2015
Download Citation: ||  

  • Download: PDF

Cite this article:
Casati, M., Rovelli, G., D’Angelo, L., Perrone, M.G., Sangiorgi, G., Bolzacchini, E. and Ferrero, L. (2015). Experimental Measurements of Particulate Matter Deliquescence and Crystallization Relative Humidity: Application in Heritage Climatology. Aerosol Air Qual. Res. 15: 399-409.


  • Aerosol’s deliquescence and crystallization measurements in the Po Valley.
  • First application in conservation science of aerosol DRH and CRH.
  • Evaluation of stone decay hazard combining climatic and pollution characteristics.
  • Chemical stress induced by wetness and mechanical stress induced by crystallization.



Climate and pollution can lead to materials weathering. In this study, an innovative method is employed to evaluate the hazard for heritage stone substrates induced by the synergic effect of particulate matter (PM) and climate. In this respect, two hazard indicators for stone materials were determined: the time of wetness and the number of dissolution and crystallization cycles. The two indicators were computed by coupling experimental measurements of the PM deliquescence and crystallization relative humidity with climatic data. For the first time, these indicators were estimated based on the PM hygroscopic properties, considering its whole hysteresis loop and its consequent hydration level.

The proposed method was applied to PM samples collected in the polluted Po Valley (Milan): the experimental measurements of both PM deliquescence and crystallization relative humidity were performed in an environmental-controlled chamber using an electrical conductivity method. The time of wetness and the number of dissolution and crystallization cycles were then calculated by coupling the PM deliquescence and crystallization relative humidity with climatic data of Milan over the last decade (2003–2013). Results point out that, depending on the seasons, different hazards were identified. In winter, high time of wetness (89 ± 11%) and low number of cycles (3 ± 3 cycles/month) were found. Conversely, summer was characterized by low time of wetness (20 ± 13%) and high number of cycles (11 ± 5 cycles/month). Interestingly, spring and fall resulted the most dangerous seasons for outdoor-exposed stones, since they presented both high time of wetness and number of cycles. Since the two indicators are calculated considering PM properties and climatic data, their values are site-specific, while the method used for their determination is of general application and it can be used for an efficient hazard assessment in a heritage climatology perspective.

Keywords: Time of wetness; Hygroscopicity; DRH; CRH; Particulate matter; Cultural heritage

Share this article with your colleagues 


Subscribe to our Newsletter 

Aerosol and Air Quality Research has published over 2,000 peer-reviewed articles. Enter your email address to receive latest updates and research articles to your inbox every second week.

77st percentile
Powered by
   SCImago Journal & Country Rank

2022 Impact Factor: 4.0
5-Year Impact Factor: 3.4

Call for Papers for the special issue on: "Carbonaceous Aerosols in the Atmosphere"

Aerosol and Air Quality Research partners with Publons

CLOCKSS system has permission to ingest, preserve, and serve this Archival Unit
CLOCKSS system has permission to ingest, preserve, and serve this Archival Unit

Aerosol and Air Quality Research (AAQR) is an independently-run non-profit journal that promotes submissions of high-quality research and strives to be one of the leading aerosol and air quality open-access journals in the world. We use cookies on this website to personalize content to improve your user experience and analyze our traffic. By using this site you agree to its use of cookies.