This study undertook laboratory incubation approach to examine abiotic
and biotic factors potentially influencing the bioweathering of Egyptian
dimension stones, namely Nubian sandstone and Theban limestone.
The dynamic and efficiency of metal release were assessed by means of
bioleaching experiments (quantification by inductively coupled plasma mass
spectrometry), whereas potential element donor phases were identified
by scanning electron microscopy (SEM-EDS). Overall, biotic weathering
plays more of an important role for initiation of limestone dissolution,
whereas its contribution to sandstone dissolution is more specific to host
minerals accommodating individual elements. Kaolinite and Fe-bearing
cement minerals (ilmenite and magnetite) in sandstones were found to
be particularly attractive to bacteria that enhanced Al and Fe leaching
by factors up to 7.0 and 5.7, respectively. Leaching of Al and Fe from
limestone was enhanced by a factor up to 13 in the presence of bacteria.
Siderophore concentration in biotic incubation reached 45.2-75.5 μmol L-1
and 90.6 μmol L-1 for sandstones and limestone, respectively. Regardless
of immersed solid, higher Ca and Mg leaching from calcite and dolomite
under chemical instead of biotic conditions was observed indicating either
preferential mineral colonization by bacteria or surface passivation by
biofilm. At the end of chemical incubation, up to 34.1% of Ca and up to
27.0% of Mg were leached from sandstones, whereas leaching observed for
limestone was up to 0.6% (Ca) and 16.3% (Mg). Limestone dissolution was
assessed at up to 1.2% (Si). This study has implications for understanding the
dissolution of dimension stone used as construction and building materials
and cultural heritage objects such as monuments and ornaments.