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As anyone who has had the misfortune of squashing one knows, stink bugs are a problem in the U.S. They've infiltrated our homes and devastated our crops — in short, they really stink. But is their stench having a larger impact? Could the accumulation of all that noxious gas pollute our air, impacting climate on a local or even global scale? A new paper by two Bucknell researchers and a summer research student indicates it does.
Published in the Journal of the Air and Waste Management Association, the paper by Professor Tim Raymond '97, chemical engineering; Chemistry Lab Director and Visiting Professor Dabrina Dutcher, chemical engineering; and Research Experiences for Undergraduates Sites program intern Dani Solomon proves that stink bugs emit volatile organic compounds (VOCs), chemicals most often associated with fossil fuel emissions. Raymond and Dutcher's research targets often overlooked biological VOC sources, like trees and now stink bugs.
VOCs are of interest to climate scientists and environmental regulators because they can react with ozone and sunlight to produce particles, which ultimately are responsible for forming clouds in the atmosphere. Raymond researches those reactions, and has previously studied particle formation from VOCs emitted by plants and even soil. While it may sound elementary, Raymond said a lack of data about particle formation from VOCs and the resulting cloud formation gives rise to the greatest uncertainty in global climate modeling. At the local level, Dutcher added, they could push cities above federal limits on smog emissions.
With a smog chamber — a Teflon bag connected to an ozone generator — the researchers proved that the bugs emit VOCs when agitated or when their internal scent glands are exposed (by crushing them with a rolled-up newspaper, for example). They also identified those VOCs and proved that they will react with ozone to form particles. Using gas chromatography-mass spectrometry, they measured the volume of each emission.
The million-dollar question, Raymond said, is how large a role do VOCs from stink bugs play in cloud formation and, thereby, global climate. The researchers can't answer that question without knowing how many stink bugs are giving off emissions, but the size of the stink bug population in America remains unknown. Localized studies suggest enormous numbers, however, indicating their impact could be significant.
Native to East Asia, brown marmorated stink bugs are thought to have migrated to the U.S. in shipping containers. The first domestic sighting was reported in 1996 near Allentown, Pa., and since then stink bug populations have exploded, infiltrating at least 33 states and decimating fruit and vegetable harvests. Their impact has been especially brutal in the South, where the warmer climate allows them to breed more frequently than in Asia. More than 26,000 stink bugs were collected in one Maryland home over six months, and as many as 20 have been found feeding on a single ear of corn. No insecticides that may legally be sprayed on food are effective in combatting them.
Raymond and Dutcher hope their work will inspire biologists to quantify stink bug populations, giving researchers a better sense of their impact on air quality. At the local level, Dutcher suspects the bugs could have an air quality impact, especially in areas where air quality approaches the Environmental Protection Agency's limits on air pollution, called maximum thresholds for particulate mass concentration. For that reason, the researchers chose to publish their paper in the Journal of the Air and Waste Management Association, a publication read by environmental regulators.
"Places like Atlanta and parts of Florida are constantly right up against the federal limit on particle mass, and they're going to get fined if they go over," Dutcher said. "They'll have to start putting all of these rules into effect, affecting all different industries, but is an invasive species problem really something they should be fined over? Is that really their fault? These bugs could push them over that limit."
The researchers said their paper was a true collaborative effort, with Solomon, a 2013 Colgate University graduate who majored in physics and creative writing, taking an active role. She wrote much of the final draft, and channeled her literary talents to contribute a key phrase, "glandular exposure."
"You can't write in a journal that you squashed the bug," Raymond said. "She came up with glandular exposure. Very clever on her part."
Solomon said composing the paper offered her more than an exercise in descriptive writing — it was also a huge confidence booster. "I thought you needed a Ph.D. or a master's to be the one to put pen to paper," she said. "But their expectation that I would do it forced me to rise to the challenge and figure out how to do it. It showed me that there's a lot out there I can do."
Raymond and Dutcher said they will move on to measuring VOC emissions from other biologic sources — but not because they can't take the smell. "I think it smells like cilantro, and I love cilantro," Raymond said. "So I don't mind it at all."