The race is on!

DRI’s air quality experts try a new twist on their research: museum preservation to save China’s national treasure

Dr. Watson and Dr. Chow assemble a pollution sampler in a pit of the museum. (All photos in this story by Dr. Junji Cao)

The year was 1974. Two Chinese peasant farmers wandered into an area of Xi’an, the capital of China’s Shaanxi Province, and proceeded to dig a well to irrigate their fields. Instead of hitting an aquifer, the farmers struck something even more precious: they stumbled upon the tomb of Qin Shi Huang, the first emperor of China. The discovery is touted as the largest and most important archaeological find in the history of China.

Go backward in time now to 221 B.C. At only 13 years old, Emperor Qin ascended to the throne and immediately commissioned his people to begin building his tomb. Over the next 38 years, while the emperor was building the first centralized feudal dynasty in China, including the Great Wall of China, more than 1 million people, or 10 percent of the local population, constructed the emperor’s tomb.

Ground penetrating radar has revealed that approximately 7,000 life-sized terra-cotta warriors, horses, chariots and even weapons exist in the mausoleum. Each soldier has a unique facial expression and dress, indicating his position in rank and duty, and all the soldiers were buried in a battle-ready position. Emperor Qin believed that if he buried himself with the warriors and horses, he would be protected in the afterlife.

Ground penetrating radar allowed archaeologists to locate and preserve 1,000 warriors and horses. Six thousand more figures are thought to still remain under ground.

Upon their discovery, the Chinese immediately began unearthing the figures in three pits. A warehouse-type structure was built around the tomb, and archaeologists have meticulously uncovered 1,000 warriors and horses to date, restoring them as best they can to their former grandeur. The Emperor Qin’s Terra-cotta Warriors and Horses Museum has been open to visitors for more than 25 years and has developed into the largest on-site museum in China with 1.5 million visitors annually.

Mold degrades the features of a terra-cotta warrior.

Today. . . the excitement of the find has turned to concern, as the exposed figures have started to decay visibly. Due to a combination of general air pollution in China, raised temperatures and humidity in the mausoleum and pollution from tourists visiting the museum, the terra-cotta warriors are being affected, showing signs of suffering from mold.

Enter DRI’s world-renowned air quality experts, Dr. Judith Chow and Dr. John Watson. No strangers to China’s air quality issues, the challenges presented by the terra-cotta army make this project unique. In the spring 2004 edition of DRI News, an article on collaborations with China discussed a memorandum of understanding, or MOU, that DRI signed with Dr. Guo Zhengtang, president of the Chinese Academy of Science’s Institute of Earth Environment. This was one of three MOUs DRI signed with China, showing DRI’s commitment to work with China to address the deteriorating air quality conditions plaguing the country.

DRI President Dr. Stephen Wells signs an agreement with members of the Chinese Academy of Science’s Institute of Earth and Environment, Hong Kong Polytechnic Institute and Emperor Qin’s Terra-cotta Warriors and Horses Museum.

On March 3, 2005, DRI President Dr. Stephen Wells, Nevada System of Higher Education Regent Jill Derby, Watson and Chow attended a signing ceremony at Emperor Qin’s Terra-cotta Warriors and Horses Museum, launching a two-year study to get to the bottom of the museum’s air quality problems. Chow and Watson, who were made adjunct professors of the Chinese Academy of Science’s Institute of Earth and Environment, will work alongside the institute’s researchers and researchers from the Hong Kong Polytechnic University to determine what type of constituents are in the air and how to best preserve the quality of the museum artifacts.

“When you stand among the figures, their size and stature are astounding,” Watson said. “And while it’s sad to see the degradation of the statues, it’s also encouraging to see how China is really making a concerted effort to circumvent the problem. They realize the value of their history and the importance of preserving it.”

It’s all in the technique. . .

Dr. Junji Cao, PI for the project; Dr. Kochy Fung, advisor to the project representing Atmoslytic Inc.; Dr. Judith Chow, DRI; Dr. Frank Lee, Hong Kong Polytechnic Institute; and Dr. John Watson, DRI.

Characterization of the air in the museum will happen in two ways: actively and passively. Active characterization involves pulling air through filters. Passive characterization uses a silicon wafer called a subtrate to absorb gases from the ambient air.

“These collectors will be placed all over the museum, in discreet places around the figures,” Chow said. “Each cartridge is chemically treated so different gases can be acquired.”

In addition to working in Pits 1 and 3 of the museum, sampling also will take place outside the building to obtain background levels of constituents in the air. Comparisons will be made to see what types of gases are occurring inside versus outside. Monitoring and characterization also will take place on a smaller scale in what is known as “chamber studies.” Pieces of artifacts will be placed in individual chambers where scientists can simulate the humidity in the museum, or place specific gases found in the museum onto the pieces to watch their reaction to them. This method will help rule out certain contaminants as problematic and narrow down the sources of the degradation.

Currently, researchers are busy setting up equipment, staging it and preparing for sampling to begin. In the fall, the museum will undergo one year of characterization, followed by compilation and reporting of results.

–Heather Emmons

Feng “Kurt” Wu, a student from the Chinese Academy of Science’s Institute of Earth and Environment works in DRI’s resuspension lab. Student collaboration is key If a student really wants hands-on, cutting-edge experience in air quality work, the easiest way to accomplish the goal is to follow around Dr. John Watson and Dr. Judy Chow. For approximately 10 years, the two top-notch researchers have been involved in several exchanges where Chinese scientists work with them in China or come to DRI. The terra-cotta warrior project is no exception. Feng “Kurt” Wu, a student from the Chinese Academy of Science’s Institute of Earth and Environment, is finishing his dissertation which involves understanding the deposition process of dust particles from yesterday, during the Quaternary Period, to today. His study explores the composition of the yellow sand typically found in China, which is the same type of sandy deposits in which the terra-cotta soldiers sit. He will spend six months in DRI’s labs in Reno, learning what is needed to assemble an adequate air sampling lab, and then he will duplicate it in China.