AN ILL WIND

During a February press conference, Thomas Cahill shows the media the monitor, top, and collector strip, middle, his team used to evaluate air samples in Manhattan after the collapse of the World Trade Center towers. Photo: Debbie Aldridge/UC Davis Mediaworks

“No one has ever reported a situation like the one we see in the World Trade Center samples,” said Thomas Cahill, an international authority on airborne particles. “The air from Ground Zero was laden with extremely high amounts of very small particles, probably associated with high temperatures in the underground debris pile. Normally, in New York City and in most of the world, situations like this just don’t exist.”

Cahill heads the UC Davis DELTA Group (for Detection and Evaluation of Long-range Transport of Aerosols), a collaborative association of aerosol scientists at several universities and national laboratories. The DELTA Group has made detailed studies of aerosols from the 1991 Gulf War oil fires, volcanic eruptions, global dust storms and most recently Asia.

The Manhattan air samples were collected at the request of a U.S. Department of Energy scientist from Oct. 2 through mid-December, by a DELTA Group air monitor placed on a rooftop one mile north-northeast of the trade center complex.

The DELTA team analyzed the samples to determine not only their chemical makeup but also the size of the particles. The group found that very fine particles, .24 micrometers to .09 micrometers in diameter, were a large fraction of the total mass in the samples. Very fine particles can travel deep into human lungs. They may have no immediate apparent health effects in moderate concentrations, but they typically are removed from the lungs through the bloodstream and heart, increasing the possibility of health impacts.

The very fine particles contained high levels of sulfur and sulfur-based compounds, which in early analyses appear to have been dominated by sulfuric acid. The very fine particles also contained high levels of very fine silicon, potentially from the thousands of tons of glass in the debris.

Many different metals were also found in the samples of very fine particles—some at the highest levels ever recorded in air in the United States. Present in relatively high concentrations were iron, titanium (associated with powdered concrete), vanadium and nickel (often associated with fuel-oil combustion), copper and zinc. Mercury and lead were seen occasionally in fine particles but at low concentrations.

Virtually all the air samples from the trade center site also carried high concentrations of coarse particles—those about 12 micrometers to 5 micrometers in diameter. Coarse particles are typically filtered by the nose or coughed out of the throat and upper lungs. They can irritate the mucous membranes, causing coughs and nosebleeds. In some individuals, they can cause allergic reactions or breathing problems.

“These particles simply should not be there,” Cahill said. “It had rained, sometimes heavily. That rain should have settled these coarse particles.” The finding suggests that coarse particles were being continually generated from the hot debris pile.

In February, when the results were announced, the team was continuing to analyze the metal content of the coarse particles.

For more information, visit the DELTA Web site at delta.ucdavis.edu.

NAMESAKES: RYERSON HALL

Knowles Ryerson

Knowles Ryerson, an expert in subtropical horticulture, spent the early years of his career studying plants in Haiti, Palestine and even, via a 600-mile canoe trip, the northern reaches of Canada. Then for several years he served with the U.S.D.A., heading the worldwide search for new plants to introduce in the United States. So when he came to head the young Davis campus in 1937, he was excited about the prospect of using the landscaping around the many new buildings to demonstrate the wide range of plants that could be grown in this climate. “People were moving into these former bare barley fields by the thousands and developing communities,” recalled Ryerson in his oral history. “They had a right to expect some guidelines from the university as to what could be gown in the valley.” But the university’s architect, Billy Hayes, had other ideas. Nothing but a poplar tree at each corner and a privet hedge around the base of the buildings would he allow. A battle ensued. Words and memos flew until their boss, Claude Hutchison, finally insisted that the two make peace and compromise. Hayes got his privet hedge. Ryerson got flowering plants and shrubs and trees more exotic than poplars—even palms around the new gymnasium. Thereafter, Ryerson would salute those palms whenever he went past, and even when Coach Crip Toomey later complained, “You won your fight, but your darn palm leaves drop in my swimming pool,” he replied: “Crip, anytime there’s a leaf there, you call me up; I’ll come over on the double and take it out. It will be a pleasure because it was worth it.”

SUPER ANTS

Those tiny black ants that infest your yard and your kitchen have laid claim to a far bigger piece of real estate. Studies by researchers from the Davis and San Diego campuses show that, from Ukiah to beyond the Mexican border, California is one huge supercolony of Argentine ants. DNA comparisons have shown that, though the ants have spread widely since they first arrived in the country in the New Orleans area, they have yet to become genetically diverse. “Colonies are so closely related they even exchange workers,” says collaborator Andy Suarez, a former UC Davis entomology postdoctoral fellow now at UC Berkeley. And that has given them an advantage. Back home in Argentina, competition between rival colonies keeps their numbers in check, but most of the California imports recognize each other as family, said Neil Tsutsui, a postdoctoral fellow in the Center for Population Biology at UC Davis who conducted the study along with Suarez and UC San Diego researchers David Holway and Ted Case. Because competition is directed outward instead of inward and because Argentine ants have the advantage of multiple queens in each colony, they have displaced native ants and become one of California’s leading household and agricultural pests.