转发：Vocus 小精灵 万米高空巡航 - Hunting for emissions thousands of feet up

转载自科罗拉多大学学报CU Boulder Today

Ten times in the past month, Alan Fried and his colleagues climbed into the back of a tiny, hot twin-engine aircraft, crouching down on their knees to check on several precious boxes of humming scientific instruments.

For Fried and his team members in CU Boulder’s Institute of Arctic and Alpine Research (INSTAAR), it was just another day in their sky-bound laboratory. 

Graduate student Phillip Stratton with the University Research Foundation at the University of Maryland Phillip Stratton explaining a typical flight pattern for the aircraft. Photo by Casey A. Cass/CU Boulder.

Left to right: Co-investigator with TOFWERK Abigail Koss, lead principal investigator (PI) with INSTAAR Alan Fried, and pilot for the University Research Foundation at University of Maryland Nizar Bechara. Photo by Casey A. Cass/CU Boulder.

Equipment and sensors inside the aircraft. Photo by Casey A. Cass/CU Boulder.

With 650 pounds of equipment in tow, pilot Nizar Bechara and one of the team’s researchers would next soar above Weld County to measure what is in the air. All told, this team spent about 29 hours in the sky in September and October gathering data about a wide variety of atmospheric emissions and chemicals.

“This has an application for air quality in the Front Range because we want to know: What''s going on with our air and what are the pollutants and their concentrations that are emitted in the Colorado Front Range? Where are these pollutants coming from? Who do they affect?” said Fried, project lead and head of INSTAAR’s Advanced Laser Technology for Atmospheric Research (ALTAiR) Laboratory.

Left to right: Senior Flight Engineer with the University Research Foundation at the University of Maryland Roger Pierson; Co-investigator with TOFWERK Abigail Koss (red jacket); graduate student with the University Research Foundation at the University of Maryland Phillip Stratton; pilot for the University Research Foundation at the University of Maryland Nizar Bechara; lead principal investigator (PI) with INSTAAR Alan Fried; and co-investigator with INSTAAR Petter Weibring. Photo by Casey A. Cass/CU Boulder.

Collected by some of the most sensitive and accurate scientific instruments available, these data contain a wealth of information that will be calibrated and analyzed over the next few months to help scientists and policymakers cut unnecessary emissions, reduce greenhouse gases and help local residents breathe better.

From tragedy to knowledge

The idea for the research project was sparked in 2017 when an uncapped natural gas well underneath a residential neighborhood in Firestone, Colorado, caused an explosion that killed two people and severely injured another.

Based on the resulting $18.25 million settlement, the Colorado Department of Public Health and the Environment (CDPHE), with oversight from the Colorado Oil and Gas Conservation Commission, proposed experiments to examine what types of gases are being emitted by hydraulic fracturing (“fracking”) sites, primarily in Weld county.

With longtime colleague Russell Dickerson, professor of atmospheric and oceanic science at the University of Maryland, Fried proposed a collaboration between researchers in ALTAiR at CU Boulder, the University Research Foundation (Greenbelt, Maryland), the University of Maryland, Colorado State University, the University of Arizona, the National Oceanic and Atmospheric Administration (NOAA), the Swiss commercial venture TOFWERK and CDPHE to take the state up on their call.

Using the University Research Foundation’s twin-engine Cessna aircraft, researchers coordinated and custom-built a series of specialized instruments to measure methane, ethane, nitrogen dioxide, carbon monoxide, carbon dioxide, ozone and a series of organic compounds at various altitudes.

What pollutants to look for

Researchers focused their quest on major leaks of chemicals like methane, the primary and extremely flammable component of natural gas.

Methane is also approximately 25 times better at trapping heat in the atmosphere than carbon dioxide, making it a potent greenhouse gas. It’s emitted primarily by fracking sites, large animal feeding operations (mainly comprising cows), wastewater ponds and landfills––all common in Weld County.

The researchers also looked for plumes where methane and ethane, an odorless and colorless gas, appeared together. Because fracking sites often emit both chemicals, while landfills and animal operations do not, ethane is an important marker for oil and gas activity, said Daniel Bon, mobile lab lead investigator at CDPHE.

While ethane is not a greenhouse gas, it reacts quickly with other chemicals in the atmosphere, which in turn can affect greenhouse gas concentrations.

“Ethane is a strange beast,” said Fried. “In its aforementioned role, ethane acts as an indirect greenhouse gas.”

Ethane also influences ozone formation as it breaks down in the atmosphere. And ground-level ozone, which forms in a chemical reaction between volatile organic compounds (VOCs), nitrogen oxides (NOx) and sunlight, doesn’t just make Denver look hazy, it’s not good for our health. Studies suggest that chronic exposure to ground-level ozone can lead to lower birth weights, asthma and higher rates of premature death.

If Fried’s team measured especially high levels of methane or ethane emissions in an area, Bon followed up on the ground in a van from CDPHE equipped to collect additional data.

The researchers are also comparing these new data on emissions with what scientists collected in 2014 in the same region during the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) led by the National Center for Atmospheric Research for CDPHE.

“Are they abating or are they increasing with time as fracking becomes more and more prevalent?” said Fried.