Measuring Carbon Tetrachloride Atmospheric Mixing Ratios in the Central Amazon Rainforest
Carbon tetrachloride (CCl4) is a potent greenhouse gas in the troposphere, while in the stratosphere it contributes to ozone destruction. Global atmospheric models treat anthropogenic industrial processes as the sole source of atmospheric CCl4. However, some evidence suggests that biogenic sources may also contribute. This article describes grab-sampling with analysis by thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS) to assess levels of CCl4 in a Central Amazonian rainforest. We find that ambient air mixing ratios within and above the forest, while agreeing with current equatorial estimates (120 ppt), show diurnal and canopy-height variations that suggest a biogenic source of CCl4, and therefore may be important for closing the gaps in the global atmospheric CCl4 budget.