Submitted to Journal of Aerosol Science
Paper presented at the Meeting "History of Aerosol Science"
Vienna, Austria, August 31-September 2, 1999
Atmospheric Aerosol Science Before 1900
Rudolf B. Husar
Center for Air Pollution Impact and Trend Analysis
Washington University, St. Louis, MO
Abstract
Throughout the past two centuries, atmospheric aerosol science has accumulated a rich
history. Atmospheric aerosol science begun in the era of Enlightenment (1700-1800)
along with the emergence of naturalists, architects, engineers, geographers and many new
ideas, good and poor. In the 19th century, the focus was on the origin of atmospheric
aerosols, which included earthquakes, thunderstorm lightning, meteoric dust as well as to
the volcanoes, windblown dust and combustion processes. By the late 1800s there was a
consolidation of the theories of haze origin by eliminating earthquakes, thunderstorm and
lightning as major sources. The era was a transition form theory-driven to observationbased atmospheric aerosol science. Also, investigators have begun applying physical laws
that govern the behavior of atmospheric aerosols. Long-range transport of smoke, dust
and volcanic aerosols was well documented, particularly through detailed observations by
Prestel. The most insightful theories on secondary aerosol formation and other processes
were advanced by Rafinesque. Modern quantitative measurements of atmospheric aerosol
concentrations begun with the work of Aitken.
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Introduction
The issues faced by atmospheric scientists prior to the twentieth century are rather similar
to the issues of concern to the atmospheric aerosol scientists in the twenty first century:
Where do atmospheric aerosols come from? What are the physical, chemical, and optical
characteristics of atmospheric aerosols and their spatial-temporal pattern? However, the
answers given to these questions have varied significantly throughout the recent
centuries. The purpose of this paper is to illustrate how scientists in the 17th and 18th
centuries dealt with the above issues. In particular, we will examine what tools of thought
have they applied to arrive at their scientific theories and explanations.
The science of atmospheric aerosols has evolved in parallel with the general evolution of
natural sciences. The rapid growth in modern atmospheric aerosol science began in the
eighteenth century, in the era of Enlightenment. This period was marked by the
emergence of naturalists, architects, engineers, and geographers. Many questions were
raised and numerous new ideas were generated. The scientific approach in this era relied
heavily on presenting theories without particular effort to backup those theories with
appropriate observations. Consequently, many of the ideas on the sources, properties, and
behavior of atmospheric aerosols have not survived later scientific scrutiny.
The 19th century was the era of transition from theory-driven to observation-based
atmospheric aerosol science. In the early 1800s the focus of the atmospheric scientists
was on formulating theories on the origin of atmospheric aerosols. By the late 1800s
there was a consolidation of theories regarding the origin of atmospheric aerosols and the
theories were qualitatively reconciled with systematic observations.
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During the mid 1800s, aerosols were of interest more to the geologists than to
meteorologists. However, by the late 1800s scientists have recognized that the presence
of aerosols facilitates rain and snow formation, and that aerosols influence both visible
and thermal radiation. This was the beginning of modern atmospheric aerosol science and
it was concluded that the study of atmospheric composition should include gaseous
substances as well as atmospheric aerosols. The late 19th century was also the emergence
of atmospheric sciences as a discipline, separate from the more mature geological
sciences.
The science of atmospheric aerosols during the 20th century addressed all the topics of
previous centuries. However, during the 20th century, methods of investigation have
explicitly included the application of laws of physics and chemistry, such as conservation
of mass, energy, as well as the laws of chemical kinetics.
The resource materials for this historical review were collected by scanning the scientific
journals such as Monthly Weather Review, Meteorologische Zeitschrift, Philosophical
Magazine, and other journals, as well as meteorology textbooks from prior to 1900.
Doctoral dissertations (e.g. Kempf, 1914) on the theory of atmospheric aerosols were
particularly useful for finding and tracing the pre-1900 literature.
This is, of course, only an incomplete account of the history of atmospheric aerosol
science. A particularly sever limitation of this review is that it only considers western
literature from Europe and North America.
Theories on the Origin of Atmospheric Aerosols
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The most significant literature source for this historical review is a dissertation by
Nikolaus Kempf, 1914 "Development of Theories on Regional Haze (Hoehenrauch) up to
1870". Kempf defined regional haze as strong atmospheric haziness (truebung der Luft)
of relatively dry air with large spatial extent and longer duration. Kempf has grouped the
existing theories on the origin of atmospheric aerosols into six categories: vapor
emissions from the Earth (earthquakes); electricity and thunderstorms; cosmic ash;
volcanic ash; windblown dust; combustion processes. Below is a brief summary of these
theories.
Haze form Gaseous Emissions from the Earth. According to this theory, atmospheric
haze can be attributed to bursts of gaseous emissions during earthquakes. For example,
Immanuel Kant (1756) in Locarno, Italy has observed that "in two hours a hot reddish
haze has spread over the valley and turned into red rain, which beyond doubt, is linked to
earthquake activity". It is likely that Kant has observed the intrusion and descent of a
Sahara dust cloud into the Locarno valley.
Marcorelle (1784) has noted that springtime warming causes the emission of
fermentation products to the atmosphere. He further suggested that sunshine evaporated
the water leaving only solid particles that constitute the spring time ‘dry fog’.
Conceivably, this theory is consistent with the current category of biogenic emissions.
Haze from Electricity.
Atmospheric haze from electrical discharges during
thunderstorms was a significant theory prior to 1850. According to Verdeil, (1783) "haze
is composed of droplets filled with electrical fluid that is attracted upward by the
electricity in the upper atmosphere" (thus prevents it from settling). Hoyer (1819)
proposed that "lightning dissociates water into H and O and the oxygen combines with
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phosphorus to form phosphoric acid". He further argues that the smell of haze (ozone?)
clearly indicates its electrical origin. Schreiber (1846) also concludes that the peculiar
smell of the haze is due to the ozone produced by the electric discharges.
Evidently, the coincidence of ozone and electric discharge and ozone and haze has lead
the early researchers to the conclusion that lightning causes haze.
Haze from Meteoric Dust. Atmospheric haze from meteoric dust has also been
considered as a significant source of atmospheric aerosol. For example, Benjamin
Franklin (1784) has invoked meteoric dust as one of the possible theories to explain the
hazy and chilly year of 1783. "The year without a summer" was actually caused by a
major volcanic eruption.
It was known that meteoric dust burns up in the atmosphere and that the particles deposit
onto the land. Some early researchers argued that meteors contribute "not less than 1
inch/century of solid material for the globe". Clearly, such high accumulation rate is not
supported by geological evidence. In fact, the overall impact of meteorological dust on
the global budget of atmospheric aerosols is thought to be insignificant (Junge, 1963)
Haze from Volcanic Emissions. Since ancient times it was recognized (e.g. Seneca, ca.
60 AD) that volcanic gases and ash cause atmospheric turbidity. However, only in the
1700s was discovered that volcanic aerosols are spread over large part of the globe. In
fact, Benjamin Franklin has noted that the haze in 1783 may have been due to a volcanic
eruption.
Haze from Windblown Dust. Throughout history it was known that windblown dust
causes regional haze. In fact, atmospheric dust and the associated atmospheric turbidity
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has been a common meteorolgical phenomena that has acquired different names in
various parts of the world: Harmattan (W. Africa), Calina (Spain). Gobar ( E. Africa),
Haboob (Arabia), Kosa (Japan), Whangsa (Korea), Huangsha (China).
Haze due to Combustion Processes. Some atmospheric turbidity is caused by the solid
and liquid combustion products. In particular, smoke from forest and grassland fires has
been a known source of atmospheric haze over many parts of the world. The particular
role of anthropogenic fuel combustion during early industrialization is reviewed by
Brimblecombe and Bowler, 1992.
By 1900, the first three theories pertaining earthquakes, electricity and cosmic dust were
eliminated and the decisive role of windblown dust, combustion smoke and volcanic
eruptions was well established.
Long Range Transport of Atmospheric Aerosols
A scientific debate about the local versus long range transport of atmospheric aerosols
has continued throughout the past two centuries. According to Kempf, 1914, Sir Francis
Bacon (ca 1600) has reported the first international long range transport incident: the
Gasgogners in southern France have complained to the King of England that smoke from
the springtime burning of seaweed in Sussex, England has spoiled the wine flowers and
ruined their wine crop.
In an extensive study, Wargentin (1767) and Gadolin (1767) have reported that forest
fires in Russia and Finland cause regional haze in Europe. They have also pointed out
that given the location of the fires, as well as the appearance of smoke at different
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locations, the path of the smoke could be geographically mapped. Evidently, Wargentin
(1767) and Gadolin (1767)) may have conducted the first systematic airmass trajectory
study.
The occurrence of regional haze in 19th century Northern Europe has a particularly
revealing history. Since the late 1700s Northern Europe was frequently under thick layers
of haze. The regional haze has covered much of the flatland north of the Alps extending
from Paris to Warsaw. Throughout the century a scientific debate was in progress on the
causes of the thick haze, including the source regions and the transport. Again, drawing
upon the review by Kempf, 1914, the cause of the regional haze was identified as
agricultural peat burning that begun in the late 1700s and peaked in 1850s. Throughout
northern Germany and Holland swamps were drained and the remaining dry peat deposits
were burned to liberate new farmland from the wetlands. The result was thick smoke
from peat fires that was lingering over the region, causing highly objectionable thick
haze. Extensive studies were conducted on the sources, transport and removal of the
smoke particles. Some of the studies have included the effects of smoke on human
health. Due to public pressure and diminishing wetlands, the burning practice stopped by
the 1870s. Thus the regional haze problem in Northern Europe simply disappeared.
The spatial and temporal pattern and the long-range transport of smoke was studied in
detail by Prestel, 1861. He collected visibility observations at dozen of sites and mapped
the advance of smoke plumes from their origin in northwestern Germany and Holland
toward the east and south (Figure 1). His data and the associated analysis clearly
documented that smoke was transported well in excess of 1,000 km from the source.
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The long-range transport of atmospheric dust has also been recognized for centuries.
Dust transport of the Sahara and Gobi deserts are well documented throughout the
reported history.
For example, sailors traveling through the tropical Atlantic have
frequently reported dust depositing on their ships thousand of kilometers from the
African continent. Similarly, early geologists have recognized that loess deposits in many
parts of the world are due to atmospheric dust transported over long distances.
Studying the dispersion of volcanic aerosols has an interesting history. Seneca, ca 60 AD,
has recognized that volcanic gases cause local atmospheric turbidity.
However,
according to Kempf, 1914 only in the 1700s was recognized that volcanic aerosols are
transported over long distances.
In 1883 red sunsets were observed throughout the world. Lacking a plausible explanation
for the ubiquitous atmospheric phenomenon, the British Royal Society has issued a
scientific competition to explain this unusual global phenomenon. The scientific price
was won by Kiessling (1888), who provided extensive and compelling evidence that the
red sunsets were due to the stratospheric aerosol of the Krakatoa volcano which erupted
in 1883. The Kiessling (1888) study was also a major contribution to dynamic
meteorology, since it revealed for the first time the existence of a general global
circulation of the atmosphere. Furthermore, the Krakatoa volcanic aerosol along with
Kiessling's explanations have demonstrated early on that atmospheric aerosols are unique
visualizers of atmospheric transport processes.
Formation and Removal Processes
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In the 17th century, many scientists have invoked rather mysterious processes for the
formation of atmospheric aerosols, including electrical discharge, earthquakes, and
meteorites. Most of the scientific explanations on the formation and removal of
atmospheric aerosols were consolidated during the 19th century. It is fascinating that
among myriad variety of theories, some remarkably clear and complete explanations
were also available already 200 years ago. For the contemporary scientists, the key
problem was of sorting out the good theories from the bad ones.
The most remarkable sets of explanations on the formation and behavior of atmospheric
aerosols were provided in several articles by Rafinesque, 1819, based on his vast
experience in earth and biological sciences. Recently, Rafinesque’s contribution to
science were described in an article by the Smithsonian Magazine, 1995. He summarized
his understanding in an essay "Thoughts on Atmospheric Dust". Rafinesque states that
"Dust exists even on the tops of the highest mountains". Thus, he recognized that aerosol
particles are mixed throughout the lower layer of the atmosphere. "It settles slowly in
clear weather but is quickly washed down by rain and snow". Clearly, he understood the
roles of dry and wet removal processes. "Some dust is from the pulverization of road and
field surfaces." This is a clear reference to the fact that some of the atmospheric aerosols
arise from re-suspension. The most insightful contribution of Rafinesque pertains to
secondary aerosol formation: "A portion (of the dust) is formed chemically in the
atmosphere by combination of gases and elementary particles dissolved in the air"
A published dialog of Rafinesque (1820) with an anonymous reader further clarifies his
position. According to an anonymous reader: "All dust comes from the action of the
wind, even the dust at sea, carried 1500 miles over the Atlantic". Rafinesque's response:
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"I do not deny that the winds raise terrestrial dust and often carry it to distance; but I
assert ...with Virey, Patrin, Deluc, and other philosophers, that there must be another
independent formation of dust in the besides the scanty terrestrial supply wafted by the
winds". "We know that sulfur, muriate of ammonia, etc. can be formed by sublimation of
gases". "That smoke soot, volcanic productions, meteorites, earths, and even stones or
metals may be spontaneously combined by a casual meeting of gaseous emanations." "It
is not, therefore, difficult to conceive how dusty particles may be formed in the great
chemical laboratory of our atmosphere."
It is quite revealing the manner in which Rafinesque has concluded that secondary
aerosol formation must be a significant mechanism for the formation of atmospheric
haze. He simply observed the rays of sun and deduced: "the sun rays are not an optical
reflection from the atmosphere since it is brighter and not so azure. It must be dust. The
phenomenon can be seen even after long and heavy rains that precipitated all the
terrestrial dust to the ground. Whence the dust must be continually formed in the
atmosphere."
Experimental verification of Rafinesque’s theories on secondary aerosol formation
occurred only eighty years later. In a long and careful series of studies, John Aitken
(1884, 1885, 1888, and 1891) has observed that on cloudy days the nuclei count remained
low. The number increased with sunshine, in proportion to the sunshine. Aitken noted
that “sunshine may produce some change in the (photochemically active) constituents of
the atmosphere which gives rise to nuclei formation in saturated air”. He also observed
that the high nuclei days were not hazy which suggested to him that the nuclei were of
“molecular dimensions”.
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Evidently, John Aitken was also the first to use the concept of chemical mass budget to
support his reasoning. He states that densely inhabited areas ‘lose their purity’, in other
words they accumulate particulate matter. “Purifying areas of the world are those regions
that lose more impurity than they gain”. Without knowing of Rafinesque’s theories,
Aitken states that “the deposition of vapor on these particles seems to be the method
adopted by nature for cleansing them away. Hence cloudy and rainy regions (of the
world) are the most purifying.” It is ironic, that at the dawn of the 21st century we still do
not have a clear understanding of which are the cleansing regions of the world.
John Aitken has also developed an elegant and still valid method of analyzing the
relationship between the particle concentration and visibility. He proposed that visibility
should be defined as the limit at which objects are visible; observations on rainy days
should be discarded and the data were to be classified according to humidity. From his
long-term observations Aitken found that the amount of haze was proportional to the
number of particles and that the product of nuclei concentration x visual range was a
constant. This corresponds to the modern observations that the horizontal aerosol
extinction coefficient is generally proportional to fine particle mass concentration. Finally
Aitken found that the aerosol extinction in moist air is twice the value in dry air.
Other researchers have concluded that the beautiful sky colors produced by volcanic
aerosol from Krakatoa and Pelee must have been produced by droplets of condensation. It
would require a long mechanical grinding to make a such a uniformly fine impalpable
powder.
The scientific methods for establishing the causes and origins of the atmospheric aerosol
were clearly stated by Egen (1835). He points out that evidence for the causality can be
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gained from: (1) direct observation, e.g. a visible smoke plume; (2) smell of the air,
which roughly corresponds to measuring the chemical composition of the aerosol; (3)
temporal variation; (4) decay with distance, i.e. the highest concentration is at the source;
(5) concentration change with wind direction, which corresponds to the current concept
of the pollution rose; (6) airmass trajectory analysis. Egen’s list of gathering evidence on
sources and source receptor relationship is virtually identical to the ones used in current
science.
To our knowledge, the first aerosol chemical mass balance was reported by M. Barac
(1901) in Fiume, (now Rijeka, Croatia). He analyzed the chemical composition of dust
particles during a Sahara dust event over the Adriatic Sea. The resulting chemical
composition pie chart is given in Figure 2. Using light microscopy, he also observed that
the dust is of bright reddish color. Under polarizing light, most particles were colorless,
irregular fragments of crystals together with skeletons of microorganisms and small
particles of soot. The dust fallout averaged between 260 and 1400 g/m2 in Fiume (a
questionable high deposition rate). According to Barac (1901) the Fiume dust belongs to
the same class as the Trade Wind dust which blows from Africa over the Atlantic.
In discussing the Barac data, the Editor of the Monthly Weather Review has added that
the "effect of this dust floating in the atmosphere was to produce a reddish haze and to
diminish the amount of insolation at the earth ’s surface thereby doubtless increasing the
temperature of the air in the upper strata". The heating effect of the absorbing dust
aerosol is still an active research area.
Discussion
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Comparing the scientific language before 1900 and after 1950 one can notice that the
words 'doubtless', 'beyond doubt', 'clearly' have virtually disappeared from the scientific
vocabulary. An interesting question is, why? The review of the historical literature also
reveals several apparently universal truths. Kempf (1914) for instance observes, that
“early researchers on regional haze paid little attention to the past theories - possibly due
to the fact that they were not as easily accessible as today”. The situation in year 2000
does not appear to be much different. In another timeless observation, Ward (1914) notes:
“So impossible is to keep our heads above the rising tide of the new meteorological
literature that we are neglecting, to our loss, the rich stores which lie buried in the books
of a generation ago.”
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References
Aitken, J. (1888) On the number of dust particles in the atmosphere. Trans. Royal Soc.
Edin. 35, 1-19.
Aitken, J. (1891) On the solid and liquid particles in clouds. Nature, Lond. 44, 279.
Aitken, J. (1894) Dust and meteorological phenomena. Nature, Lond. 49, 544 - 546.
Aitken, J. (1895) On the number of dust particles on the atmosphere of certain places in
Great Britain and on the continent, with remarks on the relation between the amount of
dust and meteorological phenomena. Trans. Royal Soc. Edin. 37, 621 - 693.
Bacon, F. ca (1600) in Kaestners Archiv f.d. ges. Naturlehre 1827, van Mons, Einige
Eigenheiten der verschidenen Nebel.
Barac, M. (1901). The red dust of March 1901. Mon. Wea. Rev. July 1901, 316-317.
Brimblecombe, P. and Bowler C. (1992) The History of Air-Pollution in York, England.
J. Air & Waste Manage. Assoc. 42, 1562-1566.
Deluc, cited in Rafinesque, C., (1819).
Editor. (1901) The red dust of March, 1901, Mo. Weather Rev. ??, 316-317.
Egen, P.N.C. (1835) Der Haarrauch, Essen.
Franklin, B. (1784) Meteorological Inaugurations and Conjectures, Mem. of the Lit. and
Philos. Soc. of Manchester, Vol. II, p 30.
Gadolin, J. (1767) Abhandlgn d. Kgl. Schwed. Akad. d. Wissenschaften, Abhandlungen
f. d. Monate April, Mai, Juni, 1767. Deutsche Uebersetzung von Kaestner 1770.
Bedenkungen von Sonnenrauch, II, pp 103-115.
Muncke, J.S. and Fr. Gehlers, (1833) Physikal. Woerterbuch, VII, N-Pn, pp. 34-53.
Leipzig.
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Hoyer, D. (1819) Mindener Sonntagsblatt, pp 187.
Junge, C. E. (1963) Air Chemistry and Radioactivity. Academic Press, New York.
Kant, I. (1756) Geschichte u. Naturbeschreibung der merkwuerdigsten Vorfaelle des
Erdbebens, welches and dem Ende des 1755. Jahres einen grossen teil der Erde
erschuettert hat. In J.K. Schriften zur Physikalischen Geographie (herausgegeben von
F.W. Schubert 1839), pp 234-235. Leipzig.
Kempf, N. (1914) Die Enwicklung der Theorien ueber den Hoehenrauch, Doctors
Dissertation vor der Kgl. Technischen Hochschule zu Muenchen, Verlag von F.C.W.
Vogel, Leipzig.
Kiessling, J. (1888) Untersuch. ueber Daemmerungs-Erscheing. zur Erklaerung d. nach
d. Krakatauausbruch beobact. Atmosphaer.optisch. Stoerung, Hamburg-Leipzig.
Marcorelle, (1784) Description d'un brouillard extraordinaire, qui a paru sur la fin du
mois Juin et au commencement de celui de Juillet. Journal de Physique (observations
sur), Janvier, Vol. 24, pp 18-23. Paris.
Patrin, cited in Rafinesque, C., 1819
Prestel, M. A. F. (1861) Meteorologische Untersuchungen betreffend die Verbreitung des
Moorrauchs in der Tagen vom 20. Bis 26. Mai 1860, die isobarometrischen Linien am
22. Mai und die Gewitter am 20. und 26. Mai 1860. Kleine Schrifte der
Naturforschenden Geselschaft in Emden, Emden Schnellpressen Druck von Th. Hahn
Wwe, Emden.
Rafinesque, C., (1819) Thoughts on atmospheric dust, American Journal of Science, Vol.
I No 4., June 1819.
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Rafinesque, C., (1920) Anonymous correspondent "X.Y.Z." of Boston reply to
Rafinesque, Silliman's American Journal, Vol. 2, No. 1, 134-135.
Smithsonian Magazine (1999) Constantine Samuel Rafinesque, Naturalist An "Odd Fish"
who swam against the tide, January issue.
Schreiber F. (1846) Versuch einer neuen Theorie der Hoehenrauchbildung. Dissertation,
Marburg.
Seneca, (ca 60 AD) 2. Buch "Naturbeobachtungen".
Virey, cited in Rafinesque, C., (1819).
Verdeil, (1783) Mem sur les brouillards electriques vus en Juin and Juillet 1783.
Memoires de la societe des sciences Phys. De Lausanne, Vol. I. pp. 110-114.
Ward, R.D.C. (1914) Lorin Blodget's "Climatology of the United States" An
Appreciation. Mon. Wea. Rev., January issue, pp. 23.
Wargentin, P. (1767) Abhandlgn d. Kgl. Schwed. Akad. d. Wissenschaften,
Abhandlungen f. d. Monate April, Mai, Juni, 1767.
Deutsche Uebersetzung von
Kaestner 1770. Anmerkungen ueber Sonnenrauch, pp 95-102.
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Figure 1. The spatial and temporal pattern and the long-range transport of smoke,
based on collected visibility observations at dozen of sites by Prestel, 1861.
Figure 2. Aerosol chemical mass balance of dust collected in Fiume by M. Barac
(1901).
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18
Chemical Mass
Sahara
Dust at Fiume, March 10-13
Balace
1901
M. Barac
(1242)
Si O2
Al2 O3
Ca O
Fe2 O3
C O2
Mn3 O4
Mg O
Organics
Traces
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