Percent water filled pore space for soil cores collected after freezing, northern Alaska, 2018

• Main Author: Lipson, David
• Format: Dataset
• Language: English
• Published: Arctic Data Center 2020
• Subjects: Arctic; Alaska
• Online Access: https://dx.doi.org/10.18739/a2pk0723g; https://arcticdata.io/catalog/view/doi:10.18739/A2PK0723G

The element, chlorine, is not normally studied in natural environments, except in areas that have been contaminated with toxic compounds like pesticides, industrial solvents or radioactive 36 Cl (chlorine). It is often assumed that chlorine enters non-contaminated ecosystems mostly in the form of chloride (the same negative ion in table salt), and that chloride does not interact with plants or soil microorganisms. However, there is growing evidence that chloride is taken up and transformed by plants and soil microorganisms into complex chlorine-containing organic compounds. In environments where oxygen is scarce, some bacteria can use these chlorinated organic compounds instead of oxygen in a form of anaerobic respiration called organohalide respiration. This is a relatively good way to make a living, and so when these bacteria are present in the soil along with a supply of chlorinated organic molecules, they can quickly use up energy sources that would otherwise be used by the microbes that produce methane. This means that an active biological chlorine cycle could reduce the amount of methane that is released into the atmosphere. Methane is a strong greenhouse gas, trapping about 30 times as much heat per molecule as carbon dioxide. The Arctic region has been warming faster than the rest of the planet, and large amounts of organic carbon are stored in Arctic soils. It is very important to understand how much soil carbon will be lost to the atmosphere in the form of carbon dioxide or methane, since these two gases will have different effects on the climate over the next century. This project measures rates of biological chlorine cycling in locations across the Arctic Coastal Plain of northern Alaska, and tests whether organohalide respiration significantly reduces methane production in these areas. This project could inform models of greenhouse gas emissions, improve understanding of the fate of chlorinated contaminants in Arctic soils, and further the basic science of biological chlorine cycling. The project will involve students at a minority-serving institution (San Diego State University) and a high school teacher, who will lead broader outreach and education efforts.