A black crust is decaying Humayun's Tomb in Delhi. How the air is to blame, and what can be done
For Delhi's monuments, researchers recommend regular maintenance, protective coatings and then monitoring.
A new study has revealed that pollution is causing a black crust to form on the sandstone walls of Humayun's Tomb in Delhi, accelerating the monument's decay. Conducted jointly by IITs at Roorkee and Kanpur, the study found that the black crust is primarily made up of gypsum, a mineral formed when sulphur dioxide in polluted air reacts with calcium-rich dust and moisture.
This crust not only makes the tomb appear dirty but also weakens the sandstone, making it more vulnerable to weathering and long-term deterioration. The damage is not uniform, with the thickest crusts developing in rain-sheltered parts of the monument where pollutants accumulate over long periods. Researchers recommend periodic removal of the black crust using scientifically tested methods, continuous monitoring of pollution around the monument, and evaluation of protective coatings before their use.
Brief written by urgent.news from Hindustan Times's own syndicated text. Machine-written — may contain errors; check the original before relying on it.
