Chloroform (CHCl3) Emissions From Coastal Antarctic Tundra

In this study, the first in situ static-chamber measurements were conducted at coastal Antarctica tundra for CHCl3 fluxes, which showed that CHCl3 was naturally emitted from the Antarctic tundra at 35 +/- 27 nmol m(-2) d(-1), comparable to other reported important natural sources. Significantly, enhanced CHCl3 emission rates (66 +/- 20 nmol m(-2) d(-1)) were observed from ornithogenic soil on the island populated with penguins, which was rich in organic matter and halides coming from penguin excrements. It is estimated that Antarctic tundra emits up to 0.1 Gg CHCl3 per year, which is an important source for regional atmospheric CHCl3. Laboratory-based incubations suggested that organic carbon and chlorine inputs by penguins may stimulate O-2 dependent microbial-mediated CHCl3 emission from the Antarctic tundra, and all tundra soils showed the maximum CHCl3 emission at 4 degrees C. The strength of this CHCl3 source is also expected to change in response to Antarctic warming. Plain Language Summary Chloroform (CHCl3) is the second-largest natural carrier of atmospheric chlorine, which can catalyze stratospheric ozone depletion. Natural sources of CHCl3 are believed to predominate over anthropogenic sources, accounting for 50%-90% of global CHCl3 emissions. Among the natural sources, soils are the second-largest source, after the ocean. This study conducted the first in situ static-chamber measurements and lab-based incubations on CHCl3 emissions from Antarctic tundra, and found that it was an important regional source, emitting up to 0.1 Gg CHCl3 each year (<1% of natural terrestrial sources) into the atmosphere. Penguin activities deposited large amounts of excrement in colony tundra and enhanced organic matter and chlorine content in the soil, which promoted the production of CHCl3 mediated by microbial activities. Temperature-controlled incubations indicated that tundra soils showed the maximum CHCl3 emission at 4 degrees C, and temperature increase and freeze-thaw cycles might influence annual and seasonal CHCl3 emissions from Antarctic tundra. This study suggested that the strength of CHCl3 source will vary in response to changes in penguin population/colony size, and the extent of Antarctic warming.