Experimental release of elements from rock varnish by industrial compounds indicate increased risk to petroglyphs

Petroglyphs on Murujuga in northwest Western Australia depict 50,000+ years of the culture and spiritual beliefs of humankind. They are sacred for the indigenous people. These priceless and irreplaceable petroglyphs are threatened by acidic gas and nitrogenous pollutants from natural gas and chemical facilities. Preservation of the rock surface ferromanganese layer is crucial for survival of the petroglyphs. Rock surface pH has fallen from neutral pre-industrialisation to 4.4–5.2 adjacent to industry. We separated surface material from Murujuga rocks, ground it finely, and subjected the powders to increasing concentrations of inorganic compounds emitted by industry and to organic acids from organisms stimulated by pollutants. Statistical analyses revealed the release of elements crucial for maintaining the integrity of the ferromanganese layer commenced at pH values well above rock surface measurements. Preservation of the globally unique petroglyphs on Murujuga requires urgent introduction of available technologies to reduce industrial emissions to zero.