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In the coming century the weathering of buildings caused by the changing climate may be more detrimental to historic fabric than air pollution. nation of better known meteorological parameters to produce output in terms of freeze-thaw cycles, wind-driven rain, humidity cycles and salts, gas and parti-cle concentration, pH of precipitation, and the water-table level. 1 After defining the climate parameters most likely to affect building materials, data available in the climate-model scenarios for the next 100 years was transformed to be useful for a discussion of future weather-ing of stone and porous masonry. This paper examines the importance of some of these predicted changes. Changes in Corrosive Air Pollutants In past centuries buildings have been blackened by coal smoke. The poet Horace was especially annoyed by black-ening of religious buildings in ancient Rome, and this problem was typical of the coal-burning cities of fin de siècle Europe, as well. 2 This issue not only led to a century of scientific concern and a range of interventions; it also influenced the nature of modern architecture. Victo-rian architects were forced to abandon the use of complex mouldings in soft, light-colored stone and look to produce buildings with simpler lines and darker colors, constructed in materials more resistant to industrial pollution. 3 The sulfur dioxide in coal smoke was responsible for an even larger amount of damage than mere cosmetic blackening. Again this problem had long been recog-nized: more than 300 years ago Sir Christopher Wren observed that coal smoke caused thick gypsum crusts to grow on buildings. By the end of the nineteenth century the dominant impact of air pollution on stone was the sulfa-tion of building surfaces through the deposition of sulfur dioxide and its oxidation to sulfuric acid. Additionally, in rain-washed areas of facades, the 13
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Damage to Buildings from Future Climate and
Pollution
PETER BRIMBLECOMBE and CARLOTA M. GROSSI
In the coming century the weathering
of buildings caused by the changing
climate may be more detrimental to
historic fabric than air pollution.
nation of better known meteorological
parameters to produce output in terms
of freeze-thaw cycles, wind-driven rain,
humidity cycles and salts, gas and parti-
cle concentration, pH of precipitation,
and the water-table level.
1
After defining
the climate parameters most likely to
affect building materials, data available
in the climate-model scenarios for the
next 100 years was transformed to be
useful for a discussion of futureweather-
ing of stone and porous masonry. This
paper examines the importance of some
of these predicted changes.
Changes in Corrosive Air Pollutants
In past centuries buildings have been
blackened by coal smoke. The poet
Horace was especially annoyed by black-
ening of religious buildings in ancient
Rome, and this problem was typical of
the coal-burning cities of fin de siècle
Europe, as well.
2
This issue not only led
to a century of scientific concern and a
range of interventions; it also influenced
the natureof modern architecture. Victo-
rian architects were forced to abandon
the use of complex mouldings in soft,
light-colored stone and look to produce
buildings with simpler lines and darker
colors, constructed in materials more
resistant to industrial pollution.
3
The sulfur dioxide in coal smoke was
responsible for an even larger amount of
damage than mere cosmetic blackening.
Again this problem had long been recog-
nized: more than 300 years ago Sir
Christopher Wren observed that coal
smoke caused thick gypsum crusts to
grow on buildings. By the end of the
nineteenth centurythe dominant impact
of air pollution on stone was the sulfa-
tion of building surfaces through the
deposition of sulfur dioxide and its
oxidation to sulfuric acid. Additionally,
in rain-washed areas of facades, the
13
Introduction
Global climate is likely to change mark-
edly this century. Greenhouse gases are
more difficult to reduce than many of the
primary trace-pollutant emissions. Re-
ductions in primary emissions have
brought about substantial declines in
urban air-pollutant concentrations since
the 1960s and 1970s in many cities of
Europe and North America. Some of the
improvements have come about through
adeclining use of coal as a source of
energy in cities. However, a reduction in
traditional air pollutants, such as sulfur
dioxide and smoke, have often been
balanced by increases in the photochemi-
cal oxidants in smog, such as ozone,
nitrogen oxides, and, more recently, fine
particles. Much of the change in the
natureof air pollution was the result of
the extensive use of the automobile,
which released volatile organic com-
pounds into the air, primarily in urban
areas. More recently the popularity of
diesel engines has increased the emissions
of fine particles in cities. Deposition of
fine particles rich in carbon blackens
buildings.
Improvements in air-pollution con-
centrations in urban air make the impact
of climate change on heritage buildings
potentially more significant. Recently
models of European climate have been
used to determine the specificfactors
necessary for predicting future scenarios
of climate impact on historical and
archaeological environments. This pro-
cess involved identifying the climate
parameters most critical for architectural
surfaces and structures and showing how
they could be derived from traditional
meteorological parameters, such as
temperature, relative humidity, solar
radiation, or precipitation. The climate
parameters relevant for cultural heritage
often involve a rearrangement or combi-
14APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 38:2-3, 2007
erosion of carbonate stones was espe-
cially pronounced. This damage was due
mainly to the loss of soluble gypsum that
had formed on the surface as it dissolved
in rainwater and the direct loss of car-
bonate by dissolution of the stone in
polluted rainwater.
4
At the present time,
when deposition of sulfur dioxide onto
building surfaces is lower, this second
mechanism of erosion has become in-
creasingly important.
The cleaner air found in cities of the
second half of the twentieth century
reduced the formation of black gypsum
crusts on buildings. Although therewas
acontinuing public debate over the role
of acid rain in causing damage, in reality
the corrosion rates of metals and build-
ing stones in such cities as London de-
clined through the last half of the cen-
tury.These improving conditions led to a
civic desire for clean buildings; however,
people were suddenly confronted by
architecture that was very bright and
unfamiliar. The cleaned buildings may
have looked closer to the architect’s
original intent, but this change was not
free of criticism from those who feared
that historyhad been scraped away.
5
Somehow our most loved and valuable
buildings had lost their patina.
Despite the overall improvements in
air quality, diesel-derived particulate
matter was increasing in concentration,
especially in heavily trafficked areas.
Diesel vehicles produce particulate mate-
rial that is finer and blacker than that
from coal smoke in the past. Diesel emis-
sions are also richer in some organic ma-
terials and adhere as fine deposits on
urban surfaces. This pollutant began to
blacken building fabric at the end of the
twentieth century. As coal-smoke had
declined, buildings wereoften cleaned,
and the public was sensitized to new
deposits of diesel soot.
6
Such changes
observed in Europe arealso found else-
where, although the timescales for their
appearance differ.
Over the next centurythereis likely
to be a continued reduction in sulfur
emissions, and nitrogen oxide emissions
may also decrease, and there should be
overall improvements in the amount acid
deposition from the atmosphere. With
the exception of ozone, pollutant con-
centrations are highest in urban areas,
which also have the highest concentra-
tion of important buildings. It may be
that the overall declining trends achieved
through the regulation of pollutants will
not always be reflected at all localities,
particularly those close to industry or
roadsides. Improvements in ozone levels
will be harder to win on a global level,
and tropospheric ozone concentrations
could remain high across wide areas of
the heavily populated continents.
7
Ozone
and oxidants in the atmosphere damage
polymers and organic materials used in
modern construction but may also en-
hance the production of acids from the
declining concentrations of sulfur and
nitrogen oxides, contributing to the
blackening and erosion of historic
buildings.
Aesthetic Change
Sulfur deposition on buildings has
caused the formation of gypsum crusts,
but as sulfur concentrations decline, the
natureof the deposits will change. The
crusts on buildings may become thinner
and richer in diesel-derived carbon and
organic materials. In particular,the
elemental carbon (EC) in the particles,
which is responsible for the dark color
of current deposits, has raised the impor-
tance of aesthetic considerations. Biolog-
ical activity, perhaps supported by an
ongoing increase in organic pollution
from deposited diesel emissions, also
contributes significantly to stone
blackening.
8
The importance of the contemporary
blackening processes in the way architec-
tural heritage has been perceived has led
to research in the public response to
soiled urban fabric. Surveys were under-
taken at nine historic European buildings
to explorevisitors’ reactions to black-
ened surfaces. These sites were chosen to
reflect different types of surroundings
and varying levels of blackening.
9
More
than 900 respondents were also asked to
choose the value of lightness, based on a
gray scale, that best represented the cur-
rent shade of the building. A range of
approaches were used to estimate thresh-
olds for acceptable levels of blackening.
10
The conclusions from the study also
offer the potential for setting guidelines
for allowable concentrations of EC in the
atmosphereto keep those levels down
such that buildings are perceived as
aesthetically acceptable. When EC con-
Fig. 1. Aesthetic threshold of acceptability of blackening of buildings in terms of perceived lightness
or reflectivity (Lp) established from viewers’ comparisons with a gray scale and from their opinions as
to whether the building was dirty. Values for individual buildings are shown as dots. When soot load-
ing of the ambient air (expressed as elemental carbon, or EC) is 10 µg m
-3
,buildings aredark (low
reflectivity) and are typically viewed as unacceptable. However, at lower EC concentrations, such as 2
to 3 µg m
-3
,building surfaces are more acceptable. Typical EC concentrations in various areas are
indicated by the lines at the top of the figure. All images by the authors.
DAMAGE TO BUILDINGS FROM FUTURE CLIMATE AND POLLUTION 15
Understandably, this is of concern,
especially when one of the buildings is
called the White Tower.
18
Climate Change
Ifair pollutants decline in the future,
climate effects may become more impor-
tant. In a period of rapid climate change,
it is important to gain a sense of how
climate effects will shift in the future. In
Europe projects such as Noah’s Ark have
been keen to develop guidelines to help
building management adapt to changing
climate (http://noahsark.isac.cnr.it/).
Anumber of specific examples illustrate
the process, with particular emphasis
on temperature, frost, and salt damage
related to relative humidity. In some
instances damage may be linked to both
climate change and pollution. For exam-
ple, building surfaces in future warmer
winters may be wet longer, such that
corrosive pollutants deposit more
readily.
19
Temperature. It is common knowledge
that temperature is predicted to rise over
the next century. This increase of some
few degrees will be critical to many
aspects of our lives and the health of
ecosystems and agriculture. However, a
change of a few degrees in the tempera-
ture of monumental heritage is much less
important. The materials from which
great buildings areconstructed are
hardly susceptible to a few degrees of
temperaturechange. It is important,
however, to look at temperature in a
more subtle way.
One important aspect that may affect
buildings is the way in which seasonal
changes impact large structures. If the
annual temperature range were to in-
crease markedly, this difference could
impose greater stress on buildings. Figure
4shows that although the temperature
of the hottest and coldest months is like-
ly to increase in central England through
the twenty-first century, the annual range
(i.e., difference between the maximum
and minimum monthly temperatures) is
unlikely to change much. However,
sudden thermal shocks could still be
important.
Frost. As discussed above, temperatureis
likely to increase by a few degrees, but
this difference is not dramatic in terms of
the damage likely to be imposed on ma-
Concern over blackening patterns
could become more important in the
future since soot concentrations in urban
areas are likely to decrease. Rain, espe-
cially heavier rain likely in future Euro-
pean summers, will clean historic build-
ings, but the patterns created by rain and
wind could be unpleasing.
14
In addition to blackening, color varia-
tions in buildings may change in the
future. This situation could arise as a
result of changing biological growth in
different climates or in the presence of
different pollutants. There are also chem-
ical and physical changes that can cause
color change. Previous work has shown
that the yellowing process on limestone
can occur at a different rate to blacken-
ing in polluted conditions.
15
Yellowing
may arise from different processes, in-
cluding sulfation and the deposition or
oxidation of organic materials or iron.
16
In the near future, urban atmospheres
dominated by organic pollutants may
cause moreyellowing of historic build-
ings than blackening. Diesel soot has
many organic compounds that can
oxidize to brownish-colored humic-like
materials.
17
Such changes would natu-
rally be of relevance in the management
of buildings. Already at the Tower of
London, thereis evidence of increasingly
warm tones of the building surfaces.
centration reaches 10 µg˙m
-3
,the sites
fail to attain satisfactory lightness, re-
gardless of the threshold criterion (Fig.
1). Where EC is 2 µg˙m
-3
,the situations
are much better, with most of the thresh-
old criteria being satisfied. Therefore,
an acceptable level for the exposure of
buildings in urban areas probably lies in
the range 2 to 3 µg˙m
-3
.
Although the blackening, can be a
nuisance, it can also be seen in terms of a
patina and thus as aesthetically benefi-
cial.
11
Light and moderate darkening
around architectural details may be con-
sidered to improve visual appearance
through increasing contrast and enhanc-
ing shadowing effects. However, heavy
soiling that leads to uniform blackening
reduces the visual information or archi-
tectural details and eventually leads to
adverse public reaction.
12
Discoloration is not always present as
ahomogeneous layer that simply covers
an entire facade, so there has been an
interest in the patterns of soiling (Fig. 2).
These patterns have long been regarded
as offensive. In 1606 Ben Jonson sav-
agely attacked Volpone, describing him
as “an old smoked wall, on which the
rain ran down in streaks!” Despite nega-
tive views of blackening patterns, there is
little research on public perception. Re-
cently the acceptability of various black-
ening patters were studied in desktop
exercises, with a methodology similar to
those used in studies of the psychology
of art(Fig. 3).
13
Arange of computer-
simulated soiling patterns was inserted
into images of a simple architectural
element (a pedimented window), and
people wereasked to choose or rank the
patternthey thought to be moreaccept-
able. The results showed a preference for
uniformpatterns and those that create
shadowing effects. Images showing less
soiling were preferred, while vertical
features and lumpiness werenot as ac-
ceptable. Patterns with noninteger fractal
dimension that obscured architectural
forms also proved less acceptable. The
results gave an insight into spatial fea-
tures that may influence the acceptability
of blackening on real buildings. The re-
sults also suggested it might be necessary
to consider both the level and the distri-
bution of soiling when trying to manage
the appearance of public buildings.
Fig. 2. Palacio del Marqués de Sta. Cruz, in
Oviedo, Spain, a historical building with disturb-
ing patterns of coloration. These markings arise
from rain streaking of black deposits and biologi-
cal staining that disfigure the architecture.
freezing.
25
In these regions increasing
temperatures that melt the upper layers
of permafrost or morefrequent freeze-
thaw cycles can disrupt the structureof
soils and damage archaeological and
paleoecological remains.
26
16APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 38:2-3, 2007
terials. However,the effect of this change
can be amplified in a number of ways.
One of the most striking is where phase
changes occur, such as water freezing or
salt solutions crystallizing. The number
of times such phase transitions occur is
verysensitive to such parameters as
temperature.
The potential increased frequency of
phase transitions, such as freezing, is
important because frost damage is a
frequent physical cause of decay of
building stones.
20
The damage arises
from the increase in volume of water in
the stone when water freezes. Inside
stone pores or fissures this volume in-
crease causes internal tensions and hy-
draulic pressure. The intensity,rate, and
duration of freezing, the cyclic action,
and interstitial moisture determine the
severity of the effect.
21
Asimple ap-
proach to representing the potential for
frost damage is to consider the number
of freeze-thaw cycles annually. The num-
ber of cycles can been determined by
examining the daily temperature data
and counting the times that temperature
crosses 0˚C (32˚F) between one day and
the next. This frequency can then be
expressed as yearly number of cycles.
The long-term change in the fre-
quency of freeze-thaw cycles can be
examined over the last 300 years by
looking at the English temperature rec-
ords that have survived for much of this
period. This data makes it possible, for
instance, to estimate the number of
freeze-thaw cycles in the past and indi-
cate a substantial reduction.
22
In the late-
eighteenth and nineteenth centuries it
appears thereweremorefreeze-thaw
cycles in central England. Thus, frost
weathering would have been a more
significant source of stone damage in a
past whereacidic air pollution was at
low concentrations, especially away
from major cities. The largest number
of cycles is typically experienced by
climates that hover close to zero degrees.
It is likely that northern climates were so
cold in past centuries that they experi-
enced fewer freeze-thaw cycles. However,
in moresoutherly latitudes the implica-
tion is that in past centuries freeze-thaw
events were probably more frequent.
The predicted temperatures from out-
put of the Hadley Model (HADCM3a2)
have been used to look at the changes
likely to occur during the present century
under the a2 scenario, which is a view of
future society that typically predicts large
climate changes.
23
Under this scenario
there is a significant reduction in freezing
across much of Europe and thus a lower
potential for shattering of stone by frost
(Figs. 5 and 6).
24
However, some areas,
such as in the far north or at high alti-
tudes, arelikely to experience an increase
in the number of freeze-thaw cycles,
often augmented by moredays above
Fig. 3. Typical idealized soiling patterns used in the authors’ study, showing
asomewhat-preferred pattern on the left that shadows the architecture
and a less preferred pattern with strong rain streaking on the right.
Fig. 4. The historical trend (solid lines) in the highest and lowest monthly
temperatures from the
Central England Temperature Record
and predic-
tions (broken lines) from modelled HadCM3a2 output. The historical annual
range of monthly temperatures is shown as filled squares and the pre-
dicted values as open squares.
Fig. 5. Pan-European maps of average yearly
number of freezing events in 30-years periods.
The top image is the baseline period from 1961
to 1990, and the bottom image far future, 2070
to 2099, generated using HadCM3a2 output.
DAMAGE TO BUILDINGS FROM FUTURE CLIMATE AND POLLUTION 17
Relative humidity and salt weathering.
Salt weathering is a further important
source of damage to buildings. It causes
physical damage, revealed as a loss of
material from the stone, or predomi-
nantly aesthetic effects, which arevisible
as an efflorescence. Relative humidity is
an important factor on whether brines in
porous materials crystallize. Cycles of
relative humidity cause crystallization
and dissolution, which exert stress on the
materials in which the salt is present.
The transition between the crystalline
and solution state occurs at a precise
relative humidity. So, as with freezing,
the crystallization of salts offers an
amplifying mechanism that allows a
small change in climate to have a signifi-
cant impact on historic fabric. Drier
climates in European summers predicted
for late this centurymay cause a two-
fold to four-fold increase in the phase
change of unhydrated salts (e.g., NaCl,
which has no water of crystallization),
thus enhancing this form of salt weather-
ing to building stones.
The potential for future changes in
halite weathering can be estimated by
considering the number times the relative
humidity in two consecutives days
crosses the critical 75.3 percent value.
Daily data from the Hadley Model
(HADCM3a2) suggests a very substan-
tial increase is likely in the number of
crystallization-dissolution cycles for
sodium chloride in the pores of building
stone (Fig. 7). However, nonhydrated
salts cause more aesthetic change than
physical damage. When a change in
hydration state is involved, the process
may exert higher pore pressures and
more potential damage to the stone.
Initial calculations for transitions be-
tween mirabilite (Na
2
SO
4
˙10H
2
O) and
thenardite (Na
2
SO
4
)suggest that this will
occur more frequently in Europe in the
future.
During this century in Europe a sub-
stantial increase in salt weathering is
expected for much of an area of the
continent stretching from Britain, France,
and northern Spain through to central
Europe. This prediction is especially
relevant in these regions given the domi-
nance of highly detailed gothic buildings
with carvings of soft porous stone. Such
architectureis vulnerable to salt damage.
It is difcult to control changes in ambi-
ent humidity, but interventions can aim
at reducing salts by washing or poultic-
ing the surface of the building or creating
barriers that prevent salts getting to
building stones.
Conclusions
The futureis, of course, always uncer-
tain. Despite this, predictions — even
when only qualitative — help narrow the
range of possibilities. Predictions of
futurechange allow long-termheritage
management to be planned morestrate-
gically. In particular, such predictions can
shift the focus to changes, such as salt
damage, that are most likely to be criti-
cal or to regions, high latitudes, or alti-
tudes, whereprocesses such as freeze-
thaw weathering will be more intense.
In the future, concentrations of acidic
air pollutants arelikely to decrease in
many parts of the world as regulation
becomes increasingly stringent. For
example, specific actions related to
heritage can be seen in Seville, Spain,
where the flow of diesel buses has been
reduced on roads close to the cathedral
to prevent damage from exhaust materi-
als. Improved air quality focuses atten-
tion on other damaging factors. Among
environmental factors, changing climate
is likely to be of increasing importance.
In temperate regions a warmer climate
should mean fewer freezing events, so
the frequency of frost damage will prob-
ably decrease over the next hundred
years. However, at higher latitudes or
high altitudes therewill be an increase in
the number of freeze-thaw events, which
will be potentially harmful for structures
and archaeological remains in these
circumpolar regions. Salts in stone repre-
sent a further mechanism for damaging
porous materials. In Europe the future
climate is likely to be less humid in the
summer months, so there will be more
frequent transition across critical values
of relative humidity. This change will
lead to more crystallization-dissolution
cycles each year, thereby increasing the
potential for salt weathering of porous
stone.
Fig. 6. Historical record of the number of freezing events as the number of
freeze-thaw cycles in central England.
Fig. 7. Annual number of phase transitions for sodium chloride (crystalliza-
tion-dissolution transition, 75.3%) predicted from the HadCM3a2 output for
central England (closed squares) and the Czech Republic in the region of
Prague (open diamonds).
18APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 38:2-3, 2007
Cleaner urban environments, greater
leisure time, and increased tourism have
sensitized visitors to the state of build-
ings. Although the physical condition
and the state of repair is important, the
public is increasingly influenced by
aesthetics and presentation. Diesel soot
and changing water flow over buildings
cause aesthetic change, as well as dam-
age, so management increasingly has to
consider these more subjective aspects of
protecting heritage. The future will likely
demand that buildings be maintained
more regularly to mitigate increased
future threats. Europe is developing
guidelines to assist in coping with an
uncertain future.
PETER BRIMBLECOMBE is a professor of
atmospheric sciences at the University of East
Anglia, in Norwich, England. He has a particu-
lar interest in the effects of air pollution and
climate on cultural heritage.
DR. CARLOTA M. GROSSI is a senior research
associate at the University of East Anglia
and specialist in building-stone decay and
conservation.
Acknowledgements
This paper forms part of an EU-funded project
called Noah’s Ark: Global Climate Change
Impact on Built Heritage and Cultural Land-
scapes (http://noahsark.isac.cnr.it/). We are also
very grateful to the other teams of the Noah’s
Ark consortium for their continuing assistance.
Notes
1. Peter Brimblecombe, Carlota M. Grossi, and
I. Harris, “Climate Change Critical to Cultural
Heritage,” in Heritage, Weathering and Conser-
vation,ed. Rafael Fort, Monica Álvarez de
Buergo, Miguel Gómez-Heras, and Carmen
Vázquez-Calvo, 387–393 (Taylor and Francis:
London, 2006).
2. Peter Brimblecombe, “Air Pollution and
Architecture, Past, Present and Future,” Journal
of Architectural Conservation 6, no. 2 (2000):
30–46.
3. C. Bowler and Peter Brimblecombe, “Environ-
mental Pressures on the Design of Manchester’s
John Rylands Library,” Journal of Design
History 13 (2000): 175–191.
4. R. A. Livingstone, “Graphical Methods for
Examining the Effects of Acid Rain and Sulfur
Dioxide of Carbonate Stones,” in Seventh
International Congress on Deterioration and
Conservation of Stone, Lisbon,ed. J. Delgado
Rodrigues, F. Henriques and F. Telmo Jeremias,
375–386 (1992). R. U. Cooke and G. B. Gibbs,
Crumbling Heritage: Studies of Stone Weather-
ing in Polluted Atmospheres (Swindon: National
Power Plc, 1993).
5. C. Andrew, “Towards an Aesthetic Theory
of Building Soiling,” in Stone Cleaning and the
Nature, Soiling and Decay Mechanisms of Stone,
ed. Robin G. M. Webster, 63–81 (London:
Donhead, 1992). Carlota M. Grossi and Peter
Brimblecombe, “Aesthetics and Perception of
Soiling,” in Air Pollution and Cultural Heritage,
ed. C. Saiz-Jimenez, 199–208 (Rotterdam:
Balkema, 2004).
6. P. T. Newby, T. A. Mansfield, and R. S.
Hamilton, “Sources and Economic Implications
of Building Soiling in Urban Areas,” Science of
the Total Environment 100 (1991): 347–65.
7. M. Prather et al., “Fresh Air in the 21st
Century?” Geophysical Research Letters 30, no.
2(2003): 72–81.
8. H. A. Viles and A. A. Gorbushina, “Soiling
and Microbial Colonisation on Urban Roadside
Limestone: A Three Year Study in Oxford
(England),” Building and Environment 38
(2003): 1217–1224.
9. Peter Brimblecombe and Carlota M. Grossi,
“Aesthetic Thresholds and Blackening of Stone
Buildings,” Science of the Total Environment
349, no. 1-3 (2005): 175–189.
10. Ibid.
11. M. Matteini. Le patine. Genesi, significato,
conservazione.(Kermesquederni: Istituto per la
Conservazione e Valorizzazione dei Beni Cultur-
ali del CNR – Nardini, 2005).
12. Andrew,63–81.
13. Carlota M. Grossi and Peter Brimblecombe,
“Aesthetics of Simulated Soiling Patterns on
Architecture,” Environmental Science and
Technology 38, no. 14 (2004): 3971–3976.
R. W. Pickford, Psychology and Visual Aesthet-
ics (London: Hutchinson Educational, 1972).
14. C. Davidson et al., “Soiling Patterns on a
Tall Limestone Building: Changes over 60
Years,” Environmental Science and Technology
34, no. 4 (2000): 560–565.
15. Carlota M. Grossi et al., “Color Changes in
Architectural Limestones from Pollution and
Cleaning,” Color Research and Application
(forthcoming).
16. Carlota M. Grossi et al., “Colour Changes
and Reactivity to SO
2
of Some Cladding Stones
at the Gran Teatre del Liceu (Barcelona,
Spain),” in Ninth International Congress on
Deterioration and Conservation of Stone,ed. V.
Fassina, 323–328 (Amsterdam: Elsevier, 2000).
S. Simon and R. Snethlage, “Marble Weathering
in Europe, Results of the Eurocare-Euromarble
Exposure Programme 1992-1994,” in Eighth
International Congress on Deterioration and
Conservation of Stone,Berlin, ed. J. Riederer,
159–166 (1996).
17. Grossi et al., “Sulfate and Carbon Com-
pounds,” 441–446.
18. Ibid.
19. Peter Brimblecombe, Carlota M. Grossi, and
I. Harris, “Future Trends in Surface Wetness and
Relative Humidity and Potential Impact on Ma-
terials,” Pollution Atmospherique (forthcoming).
20. D. B. Honeycombe, “Weathering and Decay
of Masonry,” in Conservation of Building and
Decorative Stones,ed. J. Ashurst and F. G.
Dimes, 153–178 (Oxford: Butterworth-Heine-
mann, 1990).
21. K. Hall, “Evidence for Freeze-thaw Events
and Their Implications for Rock Weathering in
Northern Canada,” Earth Surface Processes and
Landforms 29, no. 11 (2004): 43–57.
22. Peter Brimblecombe and D. Camuffo, “Long
Term Damage to the Built Environment,” in The
Effects of Air Pollution on the Built Environ-
ment,vol. 2, Air Pollution Reviews,ed. Peter
Brimblecombe, 1–30 (London: Imperial College
Press, 2003).
23. T.C. Johns et al., “Anthropogenic Climate
Change for 1860 to 2100 Simulated with the
HadCM3 Model under Updated Emissions
Scenarios,” Climate Dynamics 20, no. 6 (2003):
583–612.
24. Carlota M. Grossi, Peter Brimblecombe, and
I. Harris, “Predicting Long TermFreeze-thaw
Risks on Europe Built Heritage and Archaeologi-
cal Sites in a Changing Climate,” Science of the
Total Environment 377 (2007): 273-281. Peter
Brimblecombe, “The NOAH's ARK Project: The
Impact of FutureClimate Change on Cultural
Heritage,” The Eggs.Newsletter and Informa-
tion Service of the E.G.U.,no. 12, available at
http://www.the-eggs.org/articles.php?id=70.
25. H. A. Viles, “Implications of FutureClimate
Change for Stone Deterioration,” in Natural
Stone, Weathering Phenomena, Conservation
Strategies and Case Studies,ed. S. Siegesmund,
T. Weiss, and A. Volbrecht, 407–418 (London:
Geological Society Special Publications, 2002).
Brimblecombe, Grossi, and Harris, “Climate
Change Critical to Cultural Heritage,” 387-397.
26. J. L. Davis et al., “Ground Penetrating
Radar Surveys to Locate 1918 Spanish Flu
Victims in Permafrost,” Journal of Forensic
Sciences 45 (2000): 68–76.
... Natural atmospheric factors and air pollutants act in combination, causing damage to historic buildings, monuments, and sculptures. This phenomenon is shared, especially in urban areas [29][30][31]. The surface degradation of the stone monuments and buildings can occur everywhere or only in certain areas that are more exposed and more reactive. ...
... Considering its minimal porosity, marble is less prone to deterioration than limestone [9,31,48,56]. Bugini et al., evaluating the crust formation rate at the surface of two sculptural groups made from Carrara marble, reported that the amount of gypsum formed per unit surface was 5-13 mg/cm 2 , and the rate of gypsum formation in the black crust was about 0.2 mg/cm 2 per year [56]. ...
... The analysis of the black crusts formed on the built patrimony provides essential information on the microstructural characteristics and their chemical and mineralogical composition. It also includes information on the degree of degradation of the carbonate stone material, and the data obtained can be used to establish appropriate procedures for cleaning and restoring artifacts [5,30,31,45,60,61]. The analyses have shown that black crusts may contain traces of iron oxides, heavy metals, and elements of the stone substrate, like quartz. ...
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This paper aims to present a comprehensive review of the literature on the definition and 16 development of the concepts of heritage and sustainability. The harmful effects of various pollutants 17 on the materials widely used in the construction of monuments / buildings, which are part of the 18 national and international cultural heritage, are also highlighted. In addition, the paper draws at-19 tention to modern techniques for investigating the composition and diagnosis of alteration of build-20 ings materials with the focus on stone, limestone, and mortars/concrete. The present research also 21 emphasizes that in the case of heritage buildings, different skills are needed not only related to 22 heritage conservation and rehabilitation, but also skills related to heritage planning processes, and 23 to sustainable constructions. For exemplification, the manuscript proposes specific conservation 24 principles, based on the case of Brașov city, located in the heart of Romania and being par excellence 25 a medieval town, with representative buildings for that period. 26
... Since the industrial revolution, a significant increase in the deterioration of the buildings has been observed (Auras et al., 2013). The presence and atmospheric transport of pollutants, such as the Oxides of Nitrogen and Sulphur, Carbon Monoxide, Particulate Matter, Aerosols and Ozone, damages the built environments by abrasion, deposition and removal, direct/indirect chemical attack and corrosion, resulting in discoloration, material loss, structure falling and soiling (Peter Brimblecombe & Grossi, 2007;Watt et al., 2009). ...
... Atmospherically transported SO x , NO x , and particulate matter originating from these sources are harmful for the aesthetics and the structural integrity of the cultural heritage (Farooq & Maknoon, 2020). Climate change driven fluctuations in humidity, temperature and precipitations, combined with the air pollution greatly affects these structures (Peter Brimblecombe & Grossi, 2007). Increased localized events of acid rain, pH imbalance of soil, and water logging has historically resulted in the degradation of marble and clay structures in Mohenjodaro and Harappa (Gulzar et al., 2014). ...
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Climatic conditions have a strong relationship with human civilization since its beginning on planet Earth. The Anthropocene has transformed the world from nature-based ecosystem to energy dependent socio-ecological system of modern civilization where per capita carbon footprint has increased many folds. The human influence for the current state of global-scale anthropogenic imprint of climate change on historic heritages is context dependent. In the context, this qualitative research paper aimed to examine in depth the topic of priority interest i.e. the state of knowledge and conceptual understanding about the nexus and relationship of climate, energy, development and historic heritages in the Anthropocene by employing cause and effect modeling technique. Based on content analysis of the global state of the knowledge and three modeled scenarios including two case studies, this paper built very good arguments about the amplifying and triggering effects of GHG flux towards climatic extreme events and its cascading effects, having a complex nexus with historic heritage sites. The issues of climate vulnerability, adaptation, resilience and mitigation explored and clarified well. It deciphers the need to devise sustainable and climate compatible solutions of ‘triple-win’ strategies’ for the protection and preservation of historic heritage sites worldwide, which is a challenge of 21st century. The general cause and effect model can be used for the purpose of future climate response strategies for different historic heritage sites, by developing case specific scenarios. Key words: Anthropocene, Historic Heritage, Energy, GHG Flux, Cause and Effect Modeling, Climate compatible development
... The degradation of Heritage is influenced by many anthropic and environmental factors. The geotechnics of the land [ 2 ]; environmental factors [3][4][5][6][7][8][9][10][11] and emergency events such as earthquakes [12][13][14] and floods [15][16][17][18] are threats that generate complex degradation processes and hinder the conservation of buildings [ 6 , 8 , 12 , 13 , 16 , 18-22 ]. ...
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Heritage preservation poses numerous difficulties, especially in emergency situations or during budget cuts. In these contexts, having tools that facilitate efficient and rapid management of hazards-vulnerabilities is a priority for the preventive conservation and triage of cultural assets. This paper presents the first (to the authors' knowledge) free and public availability Artificial Intelligence platform designed for conservation strategies in cultural heritage. Art-Risk 3.0 is a platform designed as a fuzzy-logic inference system that combines information from geographical information system maps with expert assessments, in order to identify the contextual threat level and the degree of vulnerability that heritage buildings present. Thanks to the possibilities that the geographic information system offers, 12 Spanish churches (11th - 16th centuries) were analyzed. The artificial intelligence platform developed makes it possible to analyze the index of hazard, vulnerability and functionality, classify buildings according to the risk in order to do a sustainable use of budgets through the rational management of preventive conservation. The data stored in the system allows identify the danger due to geotechnics, precipitation, torrential downpour, thermal oscillation, frost, earthquake and flooding. Through the use of fuzzy logic, the tool interrelates environmental conditions with 14 other variables related to structural risks and the vulnerability of buildings, which are evaluated through bibliographic search and review of photographic images. The geographic information system has identified torrential rains and thermal oscillations as the environmental threats that mostly impact heritage buildings in Spain. The results obtained highlight the Church of Santiago de Jesús as the most vulnerable building due to a lack of preventive conservation programs. These results, consistent with the inclusion of this monument on the list of heritage at risk defined by Hispania Nostra, corroborate the functionality of the model.
... The reduction of acidic pollutants in urban areas during the late 20th century made climate a more important factor in the weathering of buildings. Small variations in climate can be amplified and lead to damage within porous materials, especially where there are changes in phase, as in salt and frost weathering (Brimblecombe and Grossi, 2007). ...
... A 3D printed model are really important to protect the Cultural Heritage, in fact they are continuously damaged by human (eg. Pollution [8] and human activity load [9]) and natural (earthquake sun, rain, wind) factors. Furthermore, as already mentioned, given the large number of small Italian villages is scattered throughout the territory, which means that visitors cannot experience close contact with each of them. ...
Article
Italy is rich in cultural heritage villages and places of interest. This work illustrates the methodology utilized by the Geomatics Laboratory (DICEAM of the Mediterranean University of Reggio Calabria) to create a archaeological structures’ 3D model. 3D modeling is based on the utilization of imaging techniques, such as computer vision and digital photogrammetry. The outcomes obtained determine the value of the technique used in the field of cultural heritage to create a digital models and to replicate them through 3d printing. Furthermore, in the renewed interest in the context of the studies of ancient villages, the implementation of open GIS represents a new method to amplify the number of visitors to the villages despite concerns about returns on investments. In fact, the use of 3D acquisition and modeling tools to enhance the Cultural Heritage represents one of the study’s areas in quickly development in the near future.
... The mechanism of damage is that when salts crystallize, the change in volume can exert mechanical stress on the materials (i.e., subflorescence) or compromise the readability of artifacts if salts crystallize on surfaces (i.e., efflorescence) (Brimblecombe, 2013;Sabbioni et al., 2010;Sabbioni et al., 2008;Viles, 2002). Brimblecombe and Grossi (2007), Sabbioni et al. (2010), and Camuffo (2019) predicted an increase in soluble salt crystallization events for almost all of Europe, but especially Central Europe, because of the projected decrease in relative humidity during the summer. The impact of weathering due to changes in the number of salt crystallization cycles, under climate change, was also specifically studied at heritage sites in France (Menéndez, 2018), The Netherlands (Nijland et al., 2009), and Panama (Ciantelli et al., 2018), where areas were identified where changes in salt crystallization cycles would subject materials to greater stress. ...
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Climate change, as revealed by gradual changes in temperature, precipitation, atmospheric moisture, and wind intensity, as well as sea level rise and changes in the occurrence of extreme events, is already affecting cultural heritage sites. Accordingly, there is a rapidly increasing body of research reporting on the impacts of climatic stressors on cultural heritage and on the assessment of climate change impacts on cultural heritage assets. This review synthesizes the international literature on climate change impacts on tangible cultural heritage by developing hazard‐impact diagrams focusing on the impacts of gradual changes in climate on: (1) the cultural heritage exposed to the outside environment, (2) the interiors of historical buildings and their collections, and (3) a third diagram associated with climate change and the impacts due to sudden changes in the natural physical environment (e.g., storm surges, floods and landslides, wildfire) in addition to sea level rise, permafrost thawing, desertification and changes in the properties of the oceans. These diagrams, which depict the relationships between various stressors and their impacts on cultural heritage, will allow other researchers, stakeholders, and potentially decision makers to determine the potential impacts of climate change on a specific cultural heritage asset without a separate examination of the literature. This review thus provides the current state‐of‐the‐art on the impacts of climate change on the tangible, built heritage, that is, monuments, archeological sites, historical buildings, as well as their interiors and the collections they hold, highlights the limitations of previous research, and provides recommendations for further studies. This article is categorized under: Assessing Impacts of Climate Change > Evaluating Future Impacts of Climate Change
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El yeso (CaSO4·2H2O) es un mineral formado en ambiente evaporíticos por precipitación química, que es la fase más estable en las condiciones de la superficie terrestre del sistema CaSO4-H2O, formado también por anhidrita (CaSO4) y basanita (CaSO4·½ H2O). Este mineral ha sido utilizado desde las primeras civilizaciones como revestimiento de paredes, soporte para frescos, moldeador para estucos decorativos, revoco y morteros. Un claro ejemplo de esto es la arquitectura islámica y mudéjar, en la que se usa el yeso ampliamente como elemento ornamental en decoraciones talladas o grabadas. Siguiendo los fundamentos de la Carta de Venecia de 1964, es crucial buscar diferentes tratamientos eficaces para conservar, preservar y restaurar estos materiales a base de yeso como parte del patrimonio arquitectónico. En la actualidad, el uso de la nanotecnología ha generado avances para el mantenimiento del patrimonio proporcionando materiales más compatibles y eficientes para la conservación. El presente Trabajo Fin de Master tiene por objetivo evaluar la eficacia de consolidantes a base de nanopartículas (nanocales y nanopartículas de sílice amorfa) y compararlos con tratamientos más tradicionales (silicato de etilo) para la preservación de yeserías frente a los agentes medioambientales. Los resultados de los análisis de caracterización composicional, mineralógica y físico-mecánica, así como los ensayos de alteración indican que los tratamientos de nanopartículas son más adecuados que el silicato de etilo para la conservación de yeserías. En particular, el tratamiento a base de nanopartículas de sílice amorfa parece óptimo para este propósito.
Chapter
An effective protection and management of the world cultural heritages is a constant challenge to conservators because of destruction and damage from natural and anthropogenic causes. Fresh sandstone surfaces of buildings are quickly covered by a layer of colonizing microorganisms, including phototrophs, lithotrophs and heterotrophs to alter the local conditions of the sandstone under the favorable tropical climate conditions. Among these different functional groups of microorganisms, lichens are known as the pioneering rock-decomposing microorganisms, and both sulfur-oxidizing bacteria and fungi participate in decomposition of sandstone and initiation of salt attack of the sandstone afterward, resulting in defoliation and cracking. Other microorganisms including ammonia-oxidizing bacteria and archaea are recently detected on sandstone monuments providing new biochemical mechanisms involved in destruction of cultural heritage and buildings. In addition, fungi colonize on surfaces of the preformed biofilms of the cultural heritage and buildings by playing a new role in removal of the pre-formed biofilms. The biochemical function of the responsible microorganisms is most significant in assessment of the damage caused by the implicated colonizers on surface of cultural heritage, and they provide basic information for effective protection strategies and good management.
Chapter
Cultural heritage objects composed of inorganic materials, such as metals and stones, support microbial life. Many factors affect the growth of microorganisms: moisture, pH, light, temperature, nutrients. Their colonization relates closely to the nature of the substrata as well as to the characteristic of the surrounding environment. This chapter contains an overview of the complex relationships among microbial growth, materials, and the environment. It emphasizes issues on bioreceptivity of stones and the factors influencing biological colonization, focusing on the biological alteration of inorganic heritage objects and on the agents of biodeterioration. It outlines the effect of biofilms and lichens in terms of degradation of substrata and includes a discussion on an important topic, the bioprotection of stones by biofilms and lichens. In summary, this chapter aims to discuss these issues and review the recent literature on (i) biofilms and lichens colonizing inorganic materials, (ii) the limiting factors of this colonization, (iii) the deteriorative aspects, and (iv) the protective effects of the colonization.
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This chapter will focus on the role of microorganisms in the removal of nitrates and sulfates on artistic stoneworks. The main groups of microbes and their metabolisms involved in bioremoval methods for the preservation and protection of cultural artifacts are reported. The aim is to offer a comprehensive view on the role and potentiality of virtuous microorganisms in the biocleaning and bioremoval of black crusts and salts altering CH stoneworks. We highlight the importance of the use of the selected microorganisms and the adoption of adequate carriers for the anaerobic metabolism of nitrate and sulfate reducers to be applied on the altered stone surfaces. The following characteristics of the delivery system are of great importance: the ability to guarantee water content for microbes, the absence of toxicity for the environment, no negative effects to the stone surfaces, easy to prepare, to apply, and to remove from different stone surfaces at the end of the treatment. We report an overview of the last 30 years on the biocleaning processes including diagnostic studies of the alterations, the assessment of associated risks, the effectiveness and efficacy of the proposed method, and the evaluation in terms of economic and environmental sustainability.
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CONTENT Preface Ch. 1 Long Term Damage to the Built Environment / P. Brimblecombe, D. Camuffo ____ p.1 Ch. 2 Background Controls on Urban Stone Decay: Lessons from Natural Rock Weathering / B. J. Smith ____ p.31 Ch. 3 Mechanisms of Air Pollution Damage to Stone / C. Sabbioni ____ p.63 Ch. 4 Mechanisms of Air Pollution Damage to Brick, Concrete and Mortar / T. Yates ____ p.107 Ch. 5 Salts and Crusts / M. Steiger ____ p.133 Ch. 6 Organic Pollutants in the Built Environment and Their Effect on the Microorganisms / C. Saiz-Jimenez ____ p.183 Ch. 7 Air Pollution Damage to Metals / J. Tidblad, V. Kucera ____ p.227 Ch. 8 The Effect of Air Pollution on Glass / J. Leissner ____ p.249 Ch. 9 The Effects of Ozone on Materials - Experimental Evaluation of the Susceptibility of Polymeric Materials to Ozone / D. S. Lee, P. M. Lewis, J. N. Cape, I. D. Leith, S. E. Espenhahn ____ p.267 Ch. 10 The Soiling of Buildings by Air Pollution / J. Watt, R. Hamilton ____ p.289 Ch. 11 Changes in Soiling Patterns Over Time on the Cathedral of Learning / W. Tang, C. I. Davidson, S. Finger, V. Etyemezian, M. F. Striegel, S. I. Sherwood ____ p.335 Ch. 12 Exposure of Buildings to Pollutants in Urban Areas: A Review of the Contributions from Different Sources / D. J. Hall, A. M. Spanton, V. Kukadia, S. Walker ____ p.351 Ch. 13 The Whole Building and Patterns of Degradation / R. Inkpen ____ p.393 Index ____ p.423
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Although modellers have established the type of climate expected in Europe over the coming century, they have not been concerned with the combination of meteorological variables most important to building damage. We have identified the climatic parameters most likely to be critical for architectural surfaces and structures. They have been loosely grouped as: (1) Temperature derived parameters – range, freeze thaw, thermal shock (2) Water derived parameters – precipitation, humidity cycles, time of wetness (3) Wind derived parameters – wind, wind driven rain, sand and salt. We also looked at pollution derived parameters such as SO2, NO2, elemental carbon and pH, but neglect these in this analysis which focuses on a European situation with much reduced air pollution forecast for the future. As expected a future Europe will experience less frost damage to porous stone, although higher temperatures can enhance fungal growth on wood. Drier summers seem likely to increase structural problems from desiccated soils and salt weathering of porous stone. Our work hint at likely heritage management strategies for the future. KeywordsBuilding-Climate Change-Damage-Heritage
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In this study we examine the anthropogenically forced climate response over the historical period, 1860 to present, and projected response to 2100, using updated emissions scenarios and an improved coupled model (HadCM3) that does not use flux adjustments. We concentrate on four new Special Report on Emission Scenarios (SRES) namely (A1FI, A2, B2, B1) prepared for the Intergovernmental Panel on Climate Change Third Assessment Report, considered more self-consistent in their socio-economic and emissions structure, and therefore more policy relevant, than older scenarios like IS92a. We include an interactive model representation of the anthropogenic sulfur cycle and both direct and indirect forcings from sulfate aerosols, but omit the second indirect forcing effect through cloud lifetimes. The modelled first indirect forcing effect through cloud droplet size is near the centre of the IPCC uncertainty range. We also model variations in tropospheric and stratospheric ozone. Greenhouse gas-forced climate change response in B2 resembles patterns in IS92a but is smaller. Sulfate aerosol and ozone forcing substantially modulates the response, cooling the land, particularly northern mid-latitudes, and altering the monsoon structure. By 2100, global mean warming in SRES scenarios ranges from 2.6 to 5.3 K above 1900 and precipitation rises by 1%/K through the twenty first century (1.4%/K omitting aerosol changes). Large-scale patterns of response broadly resemble those in an earlier model (HadCM2), but with important regional differences, particularly in the tropics. Some divergence in future response occurs across scenarios for the regions considered, but marked drying in the mid-USA and southern Europe and significantly wetter conditions for South Asia, in June-July-August, are robust and significant.
Article
Air pollution damages materials, but it has changed dramatically over the lifetime of our built heritage. There has been a decline in the primary corrosive pollutants over recent decades, but we have also seen changes in the sensitivity of materials to air pollutants. Climate has become somewhat warmer and less stormy in Britain since the Little Ice Age, so climate-driven weathering may have decreased. Architects have been obliged to recognize these external factors in their designs, but also the fact that social issues often control the costs of maintaining a rich heritage.
Article
Climate change over the next 100 years is likely to have a range of direct and indirect impacts on many natural and physical environments, including the built environment. Important influences on the built environment will include alterations in temperature, precipitation, extreme climatic events, soil conditions, groundwater and sea level. Some processes of building stone decay will be accelerated or worsened by climate change, whilst others will be retarded. The impacts on individual processes can be conceptualized, but it is difficult to assess or quantify the overall risk posed by climate change given currently available data. Linking global-scale changes to the response of individual walls or buildings remains a challenge. Overall changes in decay rates could also be related to climatic change. As an example downscaled climate predictions, knowledge of stock at risk and long-term decay rates can be used to assess the future of building stone decay in the UK. Using the UK Climatic Impacts Programme's (UKCIP98) regional climate change projections an increasing NW-SE climatic gradient is predicted, which should enhance chemical weathering of silicate building materials in the NW and increase crystallization damage of limestones in the SE.
Article
The enormous growth of the Victorian city and its parallel pollution problems confronted architects with great problems. Environmental pressures included denial of light, overcrowding, awkward sites, noise, accessibility and visibility of buildings, and air pollution. Corrosive pollutants were especially damaging to the minutely detailed Gothic architecture popular in Victorian Britain. Dense smoke made cities dark, coated the windows and penetrated inside damaging their contents. Basil Champneys, in designing Manchester's John Rylands Library, responded to these problems in an imaginative way that reflected the best of late nineteenth-century solutions. His thoughtful design made the most of available light and the crowded site. He used durable materials and colours that could resist the polluted air, while adopting electric light and air filtration inside. Valuable books and manuscripts were protected with carefully designed cases. Although not everyone was happy with the building, it has remained as an example of a determined attempt to cope with a very aggressive urban environment. Champneys confronted the conflict between design and the urban environment to produce a durable but pleasing library that proved suitable for users and provided secure accommodation for its contents.
Article
Soiling of limestone caused by air pollution has been studied at the Cathedral of Learning on the University of Pittsburgh campus. The Cathedral was constructed in the 1930s during a period of heavy pollution in Pittsburgh, PA. Archival photographs show that the building became soiled while it was still under construction. Reductions in air pollutant concentrations began in the late 1940s and 1950s and have continued to the present day. Concurrent with decreasing pollution, soiled areas of the stone have been slowly washed by rain, leaving a white, eroded surface. The patterns of white areas in archival photographs of the building are consistent with computer modeling of rain impingement showing greater wash off rates at higher elevations and on the corners of the building. Winds during the rainstorms are predominantly from the quadrant SW to NW at this location, and wind speeds as well as rain intensities are greater when winds are from this quadrant as compared with other quadrants; the sides of the building facing these directions are much less soiled than the opposing sides. Overall, these results suggest that rain washing of soiled areas on buildings occurs over a period of decades, in contrast to the process of soiling that occurs much more rapidly.
Article
This article investigates the impact of sulfur dioxide attack, deposition of dark particles in urban environments and laser cleaning with Nd:YAG 1064 nm on color change in a range of ornamental limestones. We have used the CIELAB and CIELCH systems to compare the relative importance of the variation of each coordinate for the color change. Sulfur dioxide and dark particle deposition seems to increase the chroma, most particularly in the yellow component. Particle deposition also leads to an obvious darkening of stone surfaces. Laser irradiation at 1064 nm affects the red component of limestone, particularly if they already possess a reddish color. In general, the more intense the original color of the stone the greater are the chromatic changes, but the direction change of the color-parameter affected by a particular process remains the same. It has always been apparent in an atmosphere heavily polluted with soot that the main changes to light-colored stones are the exponential decrease in the parameter L* (darkening–blackening). This has important aesthetic and social implications. However, in the near future it may be that in cleaner atmospheres, perhaps more dominated by organic pollutants, a yellowing process may be of greater concern. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 320–331, 2007
Article
Discussions regarding weathering in cold environments generally centre on mechanical processes and on the freeze–thaw mechanism in particular. Despite the almost ubiquitous assumption of freeze–thaw weathering, unequivocal proof of interstitial rock water actually freezing and thawing is singularly lacking. Equally, many studies have used the crossing of 0 °C, or values close to that, as the basis for determining the number of ‘freeze–thaw events’. In order to assess the weathering regime at a site in northern Canada, temperatures were collected at the surface, 1 cm and 3 cm depth for sets of paving bricks, with exposures both vertical and at 45°, orientated to the four cardinal directions. Temperature data were collected at 1 min intervals for 1 year. These data provide unequivocal proof for the occurrence of the freezing and thawing of water on and within the rock (freeze–thaw events). The freeze event is evidenced by the exotherm associated with the release of latent heat as the water actually freezes. This is thought to be the first record of such events from a field situation. More significantly, it was found that the temperature at which freezing occurred varied significantly through the year and that on occasion the 1 cm depth froze prior to the rock surface. The change in freeze temperature is thought to be due to the chemical weathering of the material (coupled with on-going salt inputs via the melting of snowfall), which, it is shown, could occur throughout the winter despite air temperatures down to −30 °C. This finding regarding chemical weathering is also considered to be highly significant. A number of thermal stress events were also recorded, suggesting that rock weathering in cold regions is a synergistic combination of various chemical and mechanical weathering mechanisms. Copyright © 2003 John Wiley & Sons, Ltd.