AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
The Color of Aerosol Deposition and the Browning of the Taj Mahal
J. JAI DEVI, Michael Bergin, S.N. Tripathi, Tarun Gupta, Michael McKenzie, Martin Shafer, James Schauer, K.S. Rana, Georgia Institute of Technology
Abstract Number: 588 Working Group: Remote and Regional Atmospheric Aerosols
Abstract Over the past decades the Taj Mahal, one of the wonders of the world, has taken on a brown hue that is believed to be linked to air pollution. The Taj Mahal is located in Agra, has extremely high aerosol loadings for much of the year. We will present results from a recent field study that focused on the sources of aerosols in Agra, and the impact of aerosol deposition on the color of the marble surfaces of the Taj Mahal.
Ambient filter samples for PM$_(2.5) and TSP were collected at the Taj Mahal from Dec. 2011 to May 2012 for analyses of aerosol mass and chemical composition. In addition, small cuboids of pre-cleaned marbles were stuck on the Taj Mahal to study the particle deposition flux to the monument. After several months of exposure, they were analyzed for particle size and chemical composition. The chemically resolved particle size information was used in conjunction with Mie Theory and a radiative transfer model to determine the impact of deposited particles on the spectral reflectance of the marble substrates. The estimated spectral surface reflectance was translated to color using opponent process theory.
The mean annual concentrations of PM$_(2.5) and TSP near the Taj Mahal were extremely high at values of 200 and 400 μgm$^(-3), respectively. The deposition of particles on the marble deposition substrates showed a bimodal surface area distribution with modes around 1 and 5.0 micro-meter. Elemental analyses indicated that the surface coverage was dominated by dust particles, with a much smaller contribution from carbonaceous particles. Model estimates of color based on surface concentrations of dust and carbon quantitatively agree with the surface color change observed on the sample substrates as well as the Taj Mahal exposed marble surfaces. We will discuss the relative impact of deposited dust, black carbon, and brown carbon on the color of the Taj Mahal.