Overview
- Researchers from IIT Roorkee, IIT Kanpur, Ca’ Foscari University of Venice and the Archaeological Survey of India report bonded black crusts on red sandstone that threaten carvings and surface integrity.
- Lab tests show crusts composed mainly of gypsum, bassanite and weddellite with trace heavy metals including lead, zinc, chromium and copper linked to urban emissions and construction activity.
- Measured layers range from about 0.05 mm in sheltered areas to up to 0.5 mm on walls facing heavy traffic, with thicker deposits strongly adhered and prone to causing surface loss.
- CPCB data for 2021–2023 indicate PM2.5 levels over two‑and‑a‑half times national limits, PM10 over three times, and NO2 above standards, conditions the study ties to accelerated stone decay.
- Site observations include flaking sandstone, loss of carved detail, blistering of plastered walls and vaults, dampness and salt efflorescence, prompting recommendations for routine cleaning, stone protectives and tighter pollution controls.