Determination of chloromethane and dichloromethane in a tropical terrestrial mangrove forest in Brazil by measurements and modelling

Abstract

A B S T R A C TChloromethane (CH 3 Cl) and dichloromethane (CH 2 Cl 2 ) are known to have both natural and anthropogenic sources to the atmosphere. From recent studies it is known that tropical and sub tropical plants are primary sources of CH 3 Cl in the atmosphere. In order to quantify the biogenic emissions of CH 3 Cl and CH 2 Cl 2 from mangroves, field measurement were conducted in a tropical mangrove forest on the coast of Brazil. To the best of our knowledge these field measurements were the first of its kind conducted in the tropical mangrove ecosystem of Braganca. A mesoscale atmospheric model, MEsoscale TRAnsport and fluid (Stream) model (METRAS), was used to simulate passive tracers concentrations and to study the dependency of concentrations on type of emission function and meteorology. Model simulated concentrations were normalized using the observed field data. With the help of the mesoscale model results and the observed data the mangrove emissions were estimated at the local scale. By using this bottom-up approach the global emissions of CH 3 Cl and CH 2 Cl 2 from mangroves were quantified. The emission range obtained with different emission functions and different meteorology are 4-7 Gg yr −1 for CH 3 Cl and 1-2 Gg yr 2 for CH 2 Cl 2 . Based on the present study the mangroves contribute 0.3 percent of CH 2 Cl 2 and 0.2 percent of CH 3 Cl in the global emission budget. This study corroborates the study by Manley et al. (2007) which estimated that mangroves produce 0.3 percent of CH 3 Cl in the global emission budget. Although they contribute a small percentage in the global budget, their long lifetime enables them to contribute to the destruction of ozone in the stratosphere. From the detailed analyses of the model results it can be concluded that meteorology has a larger influence on the variability of concentrations than the temporal variability of the emission function.

Identification and widespread environmental distribution of a gene cassette implicated in anaerobic dichloromethane degradation

“…DCM predates the anthropocene (Trudinger et al, 2004), and the mechanisms underlying natural releases are far from fully characterized. Based on the available information, DCM is an energy source readily available to microorganisms (Cox et al, 2004; Gribble, 2010; Kolusu et al, 2018), and the anaerobic microbial consumption of DCM is likely a major attenuation factor, eliminating DCM in anoxic environments prior to atmospheric release, and thus a relevant process for reducing DCM emissions. Environmental change, including global warming, has high potential to alter the flux of DCM with unpredictable consequences for emissions and the integrity of the ozone layer.…”

“…Natural and deliberate forest fires have increased in frequency and size (Haines et al, 2020), a global trend that can be expected to lead to further formation and release of DCM. Wetlands emit up to 2 Gg DCM/year (Cox et al, 2004; Hu et al, 2017; Kolusu et al, 2018) (Supplementary Information), and volcanic activity contributes an estimated amount of 0.021 Gg DCM/year (Gribble, 2010). Halomethanes occur in crustal minerals, and DCM release from rocks from the near‐surface and the deep subsurface have been reported (Mulder et al, 2013; Svensen et al, 2009).…”

A Synthesis Inversion to Constrain Global Emissions of Two Very Short Lived Chlorocarbons: Dichloromethane, and Perchloroethylene

“…Annual global CH 2 Cl 2 emissions have been estimated at~1,000 Gg yr −1 in 2016, with a global mean surface mole fraction of 33-39 ppt observed from monitoring networks, a factor of~2 larger compared to the early part of the century (Engel et al, 2018). Biogenic CH 2 Cl 2 sources have also been hypothesized from the ocean (Jones & Carpenter, 2005;Ooki & Yokouchi, 2011) and from mangrove forests (Kolusu et al, 2018), though the magnitudes of these sources are poorly constrained and are expected to be small. A less abundant Cl-VSLS is perchloroethylene, C 2 Cl 4 , which is almost solely anthropogenic and historically has found use, for example, in dry-cleaning applications.…”

Ariel – a window to the origin of life on early earth?

“…Can be a biomarker in terrestrial planets around M type stars [337]. Most abundant chlorine compound in Earth's atmosphere, produced by bacteria and trees (mangroves) [338] Viability as biomarker around other types of stars has not been explored.…”