![]() However, CCl4 emissions have not been characterized in many ecosystems including tropical forests, which cycle more carbon and water than any other biome on Earth (5).Īs a result of its high volatility, current methods for ambient CCl4 quantitation involve flask sample collections followed by cryogenic focusing and subsequent analysis by GC–MS (2). The authors concluded that biogenic surface emissions to the atmosphere may make only a minor source contribution on the global scale. A recent study found that live and decaying plants, mosses, and microbes from a mid-latitude spruce forest can emit CCl4 (2). For example, plant enclosure studies in shrub land and coastal ecosystems in southern California (3), as well as creosote bush in the Sonoran Desert of Arizona (4), showed net emissions of CCl4. However, the global atmospheric CCl4 budget suggests a missing CCl4 source (2), and there is some evidence supporting a potentially important biogenic CCl4 source. It is currently assumed that anthropogenic industrial processes are the sole source of CCl4 to the atmosphere. The primary CCl4 sink is stratospheric photochemical destruction while the oceans and soils are considered minor CCl4 sinks (but these remain poorly characterized). Global CCl4 Atmospheric Budget: Satellite observations from space demonstrate that the greatest global CCl4 atmospheric mixing ratios (100–130 parts per trillion ) are found in the troposphere (<10 km altitude) over the mid-latitude industrialized regions and above the equatorial tropics (1). However, in the stratosphere, CCl4 photochemical reactions contribute to stratospheric ozone depletion and therefore CCl4 was marked as a compound to phase out of industrial processes by the 1987 Montreal Protocol (1). With an estimated lifetime of 34 years, CCl4 is considered chemically inert in the troposphere. 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.Ĭlimate Impacts of Atmospheric CCl4: In the troposphere, carbon tetrachloride (CCl4) is a greenhouse gas with a global warming potential 1400 times greater than CO2. 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. However, some evidence suggests that biogenic sources may also contribute. Global atmospheric models treat anthropogenic industrial processes as the sole source of atmospheric CCl4. ![]() Angela Jardine 1, David Barden 2, and Kolby Jardine 3, 1Climate and Environment Department, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil, 2Markes International, Gwaun Elai Medi-Science Campus, Llantrisant, Wales, UK, 3Earth and Environmental Sciences Area, Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.Ĭarbon tetrachloride (CCl4) is a potent greenhouse gas in the troposphere, while in the stratosphere it contributes to ozone destruction.
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