By Jeffrey Levin

The deterioration of an historic site—be it an outdoor Siqueiros mural in downtown Los Angeles or the Great Sphinx of the Giza Plateau—is often the result of environmental factors. Government agencies, site managers, conservators, archaeologists, and others responsible for the condition of a site require as much knowledge as possible about the site's environmental conditions. Yet rarely is extensive statistical data available.

To gather a broad spectrum of quantifiable data on environmental conditions affecting cultural property, the GCI has, since 1990, installed microenvironmental monitoring stations at several significant sites around the world. Monitoring stations have been established at Buddhist temple sites at the Mogao and Yungang Grottoes in the People's Republic of China, the pre-Hispanic site of Tiwanaku in Bolivia, and the Great Sphinx and the tomb of Nefertari in Egypt.

Monitoring devices also have been placed at Fort Selden State Monument in New Mexico and at Pueblo Park in Los Angeles, site of a work by Mexican muralist David Siqueiros.

The autonomous, solar-powered environmental monitoring stations represent a substantial advancement over the hand-held monitoring devices used by conservators in the past. They are designed to provide conservators with the precise and comprehensive information needed to manage sites appropriately and to develop realistic conservation strategies for the future.

The GCI stations have a number of different electronic monitoring sensors designed for long-term data collection. The monitoring stations combine traditional devices for measuring climatic conditions (i.e., temperature, rainfall, humidity, and wind conditions) with other technology originally developed for use in agriculture and industry, such as photoelectric, wetness, carbon dioxide, and infrared sensors. When applied to cultural property, the enhanced technology supplies more complete data essential in determining ways to improve a site's conservation. For example, photoelectric sensors help document the number of visitors to a site, while carbon dioxide sensors, in an enclosed site, calculate the visitors' effect on the interior atmosphere. Wetness sensors determine the presence of condensation on the stone of a monument, while infrared sensors measure the temperature of an object without touching the object itself.

Besides supplying information on a variety of environmental conditions, the monitoring stations deliver a greater depth of data than previously available. Unlike hand-held monitors, which require human operation, stations automatically operate twenty-four hours a day and average their sensor readings at set intervals. This is particularly important for sites where frequent data sampling is needed to study the environmental impact of visitors.

The stations are self-contained and require minimal maintenance. Data from all sites is presently collected by the GCI, either directly or at established collection times, for processing and analysis. At all locations, local staff are being trained to use this technology.

To obtain a broader understanding of the effects of a range of environmental factors on cultural property, the GCI plans to install a number of stations in tropical environments. Other site conditions to be monitored in the future will include the movement of air and dust particles in interior spaces. Already in the works is the GCI's first environmental monitoring project in an historic urban setting. In November 1991, monitoring equipment will be established in the city center of Quito, a World Heritage Site with a high density of historic monuments.

The environmental monitoring projects are supervised by Dr. Shin Maekawa, Head, Environmental Science, Scientific Program, the GCI.