Methyl Chloride and Methyl Bromide Production and Consumption in Coastal Antarctic Tundra Soils Subject to Sea Animal Activities

Abstract

Methyl chloride (CH 3 Cl) and methyl bromide (CH 3 Br) are the predominant carriers of natural chlorine and bromine from the troposphere to the stratosphere, which can catalyze the destruction of stratospheric ozone. Here, penguin colony soils (PCS) and the adjacent tundra soils (i.e., penguin-lacking colony soils, PLS), seal colony soils (SCS), tundra marsh soils (TMS), and normal upland tundra soils (UTS) in coastal Antarctica were collected and incubated for the first time to confirm that these soils were CH 3 Cl and CH 3 Br sources or sinks. Overall, tundra soil acted as a net sink for CH 3 Cl and CH 3 Br with potential flux ranges from −18.1 to −2.8 pmol g −1 d −1 and −1.32 to −0.24 pmol g −1 d −1 , respectively. The deposition of penguin guano or seal excrement into tundra soils facilitated the simultaneous production of CH 3 Cl and CH 3 Br and resulted in a smaller sink in PCS, SCS, and PLS. Laboratory-based thermal treatments and anaerobic incubation experiments suggested that the consumption of CH 3 Cl and CH 3 Br was predominantly mediated by microbes while the production was abiotic and O 2 independent. Temperature gradient incubations revealed that increasing soil temperature promoted the consumption of CH 3 Cl and CH 3 Br in UTS, suggesting that the regional sink may increase with Antarctic warming, depending on changes in soil moisture and abiotic production rates.

Application of copper(II)-based chemicals induces CH3Br and CH3Cl emissions from soil and seawater

“…1 ). After being autoclaved, they switched to CH 3 Br and CH 3 Cl sources at 0.45 ng kg −1 hr −1 and 6.9 ng kg −1 hr −1 , respectively, supporting the conventional idea that soils act as a bi-directional interface of CH 3 Br and CH 3 Cl with simultaneous enzymatic degradation and abiotic production 5 , 12 , 18 . The deactivation of methyl halide-consuming microorganisms following heat treatment 19 in autoclaved soil results in the unidirectional interface of CH 3 Cl and CH 3 Br emissions, possibly catalyzed by endogenous Fe(III) in the soil 12 .…”

“…Flux calculation. CH 3 Br and CH 3 Cl fluxes from the samples were calculated based on the hourly averaged change of headspace concentration multiplied by moles of headspace air 5 , and normalized to the dry mass of the soil (ng kg −1 hr −1 ) or the volume of the seawater (ng L −1 hr −1 ); or were reported as the total mass of CH 3 Br and CH 3 Cl produced in pure chemical experiments (ng). Positive fluxes represented production of CH 3 Br and CH 3 Cl while negative fluxes represented consumption of CH 3 Br and CH 3 Cl from the headspace air.…”

“…The present atmospheric CH 3 Br and CH 3 Cl originate from predominantly natural sources. These natural sources tend to be amplified under anthropogenic-induced influences, such as biomass burning 3 , global warming 4 , 5 , sea level rise 6 , 7 , agricultural cultivation 8 , land use change 9 , etc., posing persistent and growing challenges for the recovery of stratospheric ozone 10 , 11 .…”

Non-destructive chemical sensing within bulk soil using 1000 biosensors per gram of matrix

“…Furthermore, over this short time scale, the living soil accumulated significantly more CH3Br than the autoclaved soils. Other studies have observed that sterilization treatments significantly alter net CH3X flux from soils, affirming that biological processes dominate CH3X fluxes in situ 29,[38][39][40] .…”

“…Under extreme dry conditions, microbial metabolic activity is expected to be attenuated, thereby decreasing indicator gas production rates, while water saturated conditions are expected to hamper gas diffusion from soil pores to the headspace 51 . Natural CH3X fluxes in soils are also known to vary with temperature 40, 52 , hydration 47, 53 , organic matter content 29, 49 , halide concentration 17 , redox properties 39, 53 and microbiome 29, 40 . Additional studies are needed to understand how these processes affect total indicator gas accumulation in the headspace of different matrices.…”