Nathan Phillips steps out onto the roof of Boston's Prudential Tower and looks down at the city 50 stories below. Up here, the rush of the wind has replaced the cacophony of car horns, screeching brakes and conversations filling the streets. And the rarefied air carries none of the odours that wrinkle an urban nose. The roof is “essentially a different atmospheric environment from the rest of the city”, says Phillips, an ecologist at Boston University in Massachusetts.
That rarefied air is what brings Phillips to the top of the tower. He has set up four book-sized collectors, one at each corner of the roof, to capture air blowing across the city. Black tubing carries the air samples to a tank inside the building, where a computer analyses their levels of carbon dioxide, carbon monoxide, methane and water vapour.
Like most cities, Boston brews up a blend of gases that covers the urban area like a dome. The top of the Prudential Tower is inside or outside this metropolitan atmosphere, depending on the weather. From his rooftop eyrie, Phillips looks towards three other sampling sites around the city and another some 70 miles west, in the green hills outside the pollution zone.
Phillips and his colleagues are using data from these sites to model how carbon dioxide and other gases move through the city, and how the mix differs from the air in rural areas. The work is part of an interdisciplinary project to study Boston's 'metabolism' — how elements are exchanged between natural and human systems. Phillips and his team are now focusing on atmospheric carbon — particularly carbon dioxide and methane. Next, they plan to look at carbon in the city's soils and water, and to track the flow of water, nitrogen and pollutants. “The goal is to understand the function of a major city,” Phillips says. READ MORE >>