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PRESERVING AND PROTECTING MONUMENTS AND HISTORICAL SITES

The west face of the Parthenon, Athens, Greece

Photo 1. The west face of the Parthenon, Athens, Greece

By Michael Reddy

U.S. GEOLOGICAL SURVEY


The International Association of Engineering Geology recently sponsored a symposium on protecting and preserving historical sites and monuments. Entitled "Engineering Geology as Related to the Study, Preservation, and Protection of Ancient Works, Monuments, and Historical Sites," the symposium was held in Athens, Greece, September 19-23, 1988. Organized by the Greek National Group of this international association, in collaboration with the Greek Ministry of Culture, the symposium was cosponsored by UNESCO, the Commission of the European Communities, and the International Council on Monuments and Sites.

Areas of study reported on at the symposium included: soil and rock mechanics, foundation engineering, structural geology, geomorphology, geophysics, seismology, weathering, erosion and decay, and preservation techniques. A number of national and international organizations are concerned about an apparently accelerating rate of deterioration of cultural treasures in many parts of the world, resulting from man-made and natural causes. Some of these causes are related directly to rapid urbanization.

Opening ceremonies were held at the Odeon of Herod Atticus, the ancient theater at the base of the Acropolis, shown in Photo 1. The ceremonies were followed by a tour of the Acropolis led by the curator, Mrs. E. Touloupa, and her staff. During the tour, Mrs. Touloupa led attendees through the areas of the Parthenon that are undergoing rehabilitation and reconstruction.

Scaffolding visible at the left and center in Photo I is being used in the restoration. Of interest to the symposium participants were the methods used to reproduce, on site, missing sections of structural stone for the Parthenon. Pentelic marble (from Mount Pentelicus, or Pendelikon, about 15 miles northeast of Athens), is the primary building material of the Acropolis monuments; this marble is used in the restoration to make patches in, or copies of, the stones. The physical and mechanical properties of the pentelic marble quarried today are almost identical to those of the durable marble of the original construction.

Damage from pollution

Several papers presented at the symposium chronicled the damage to the Parthenon during the past 2500 years. After surveying natural and man-made damage, including explosions and partial demolition, researchers are suggesting that the monuments may be undergoing continuous damage due to environmental pollution. There is evidence that air pollution has caused substantial harm to monuments on the Acropolis. Air pollution damage to the interior surfaces of two column capitals is shown in Photo 2.

Parthenon column capital

Photo 2. Parthenon column capitals. Black crusts due to air pollution are present on the inward-facing surfaces of the columns and the column capitals

Although this air pollution damage may manifest itself in several ways, it typically occurs as a black crust or coating on carbonate stone surfaces. Several areas of the Parthenon have such black surface crusts. The black crust that has formed at the top of a column and on a capital, and its characteristic distribution, is clearly visible in Photo 3.

Black crust on a Parthenon column capital

Photo 3. Black crust on a Parthenon column capital in an area of ongoing restorations and reconstruction

These damaged areas seem to receive little rain or rain runoff and seem to be formed by sulfur dioxide uptake, in the presence of moisture, on the stone surface. Subsequent conversion of the sulfur dioxide to sulfuric acid results in the formation of a layer of gypsum on the marble surface. An ongoing debate concerns the most effective method of retarding and remedying this type of air pollution damage. Informal discussions with symposium participants indicated that acid precipitation also occurs in Athens, and this may aggravate the air pollution damage.

A plenary session focused on the Acropolis and the research about the foundation rock and the preservation of monuments located on it. Mrs. Touloupa presented a paper entitled, "The Monuments of the Acropolis and the Efforts for Their Safeguarding" during this session. In her paper, she said, "At the present time there is no effective way of dealing with damage to marble due to atmospheric pollution."

However, after participating in the symposium, I am confident that with the international cooperation and intense scientific effort being devoted to monument preservation, significant progress will be made. That progress will be made most rapidly through the study and understanding of the fundamental processes involved in the damage.

The proceedings of the symposium have been published in a three-volume set, The Engineering Geology of Ancient Works, Monuments and Historical Sites-Preservation and Protection (P. G. Marinos and G. C. Koukis, editors; A. A. Balkema, publisher, Rotterdam, The Netherlands). A fourth post-symposium volume that contains general reports will be available soon. The symposium chairman, Professor Paul G. Marinos of the Civil Engineering Department at National Technical University of Athens, stated that the symposium was attended by more than 500 scientists, engineers, and professionals.

M.M. Reddy, Hydrologist, USGS, Denver, CO

Michael M. Reddy is a hydrologist with the U.S. Geological Survey in Denver, CO. He received his B. S. degree in 1966 and his Ph.D. in 1970, both in chemistry, from the State University of New York at Buffalo. He worked as an instructor at SUNY Buffalo for several years, then as a research scientist at the New York State Department of Health before beginning work at the USGS in 1980.

The above paper was published in Environmental Science and Technology, March 1989, v. 23, pp. 264-265 by the American Chemical Society.