Air Pollutant Intrusion into the Wieliczka Salt Mine
The Wieliczka Salt Mine, located in southern Poland near
the city of Krakow, has been
worked as a source of rock salt since the late 13th century.
The mine consists of over 200 km of underground passages, connecting
more than 2000 excavation chambers on 9 underground levels
extending down to 327m below the surface,
see diagram .
Over the centuries, miners have established a tradition of
carving sculptures out of the native rock salt.
As a result, the mine contains entire underground churches, altars,
bas-reliefs, and dozens of life-size or larger
statues. It also houses an
underground museum and has
a number of special purpose chambers such as a sanatorium for
people suffering from respiratory ailments.
The largest of the chapels,
the Chapel of the Blessed Kinga,
is located 101 meters below the surface, it is over 50
meters long, 15 meters wide, 12 meters high, with a
volume of 10,000 cubic meters.
As a testament to its historical and artistic importance,
the mine has been placed on UNESCO's
World Heritage List of sites
designated as having ``outstanding universal value to mankind.''
It receives up to a million visitors yearly, most of them
during the warmer summer months.
Today, many of the salt sculptures are slowly dissolving.
Water vapor present in the ventilation air in the mine is being
absorbed into
the rock salt at several locations in the mine,
causing erosion of the carved salt surfaces.
A joint team of Polish and
American scientists and engineers are conducting experiments in the
mine to document the environmental conditions there and
to seek solutions to the water vapor condensation problem.
One question faced by the study team is
whether or not there is any
significant soiling or chemical attack on the statuary that
might alter the hygroscopic character of the salt.
Rock salt develops a liquid film on its surface and begins to dissolve
when the relative humidity of the surrounding air reaches approximately
75%. This is known as the relative humidity of
deliquescence.
Airborne ionic substances (e.g., nitrates) having relative
humidities of deliquescence below that of rock salt could
deposit onto the sculptures to an extent that
the deliquescence point of the salt surface is lowered.
If this occurs, it would influence the
selection of a future dehumidification system for the mine.
The purpose of our current research is to examine
the transport of air pollutants from the outdoor atmosphere into
the mine, and the subsequent deposition of those pollutants onto
the surfaces in the mine, with an eye toward
determining whether or not the deliquescence point of the
salt would be significantly affected by the pollutant deposition processes.
Filter-based air sampling methods are used to determine the
concentration and chemical composition of airborne particles in
both fine and coarse
particle size ranges, as well as the
concentrations of selected reactive gases:
sulfur dioxide (SO2), nitrogen dioxide (NO2),
nitric acid (HNO3), and hydrochloric acid (HCl).
Deposition plates and scrapings taken from surfaces
in the mine also are used
for studying particulate plus gas-phase pollutant deposition to surfaces.
These measurements reveal the chemical and physical nature
of the pollutants present, the rate of pollutant
accumulation on surfaces, and whether or not there are significant
differences in pollutant concentration from one chamber
to another throughout the mine.
More information about Wieliczka:
Our scientific paper in
Environmental Science and Technology:
Air Pollutant Intrusion into the Wieliczka Salt Mine
My complete list of publications.
Lynn Salmon <>{
Last updated: August 3, 2021
