Dimethyl sulfide in the Amazon rain forest - eScholarship

PUBLICATIONS Global Biogeochemical Cycles RESEARCH ARTICLE 10.1002/2014GB004969 Special Section: Trends and Determinants of the Amazon Rainforests in a Changing World, A Carbon Cycle Perspective Key Points: • Vertical atmospheric gradients of DMS characterized in the central Amazon • Enclosure and atmospheric studies indicate both soil and vegetation sources • Results suggest important climate impact(s) via aerosol and cloud processes Supporting Information: • Text S1 and Figures S1–S6 Correspondence to: K. Jardine, kjjardine@lbl.gov Citation: Jardine, K., et al. (2015), Dimethyl sulfide in the Amazon rain forest, Global Biogeochem. Cycles, 29, 19–32, doi:10.1002/2014GB004969. Received 15 AUG 2014 Accepted 4 DEC 2014 Accepted article online 8 DEC 2014 Published online 8 JAN 2015 Dimethyl sulfide in the Amazon rain forest K. Jardine 1 , A. M. Yanez-Serrano 2 , J. Williams 3 , N. Kunert 4 , A. Jardine 2 , T. Taylor 5 , L. Abrell 6 , P. Artaxo 7 , A. Guenther 8 , C. N. Hewitt 9 , E. House 9 , A. P. Florentino 2 , A. Manzi 2 , N. Higuchi 2 , J. Kesselmeier 3 , T. Behrendt 3 , P. R. Veres 3 , B. Derstroff 3 , J. D. Fuentes 10 , S. T. Martin 11 , and M. O. Andreae 3 Climate Science Department, Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA, National Institute for Amazon Research, Manaus, Brazil, 3 Atmospheric Chemistry and Biogeochemistry Departments, Max Planck Institute for Chemistry, Mainz, Germany, 4 Max Plank Institute for Biogeochemistry, Jena, Germany, 5 Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, USA, 6 Departments of Chemistry and Biochemistry and Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona, USA, 7 Institute of Physics, University of Sao Paulo, Sao Paulo, Brazil, 8 Pacific Northwest National Laboratory, Richland, Washington, USA, 9 Lancaster Environment Centre, University of Lancaster, Lancaster, UK, 10 Department of Meteorology, College of Earth and Mineral Sciences, Pennsylvania State University, University Park, Pennsylvania, USA, 11 School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA Abstract Surface-to-atmosphere emissions of dimethyl sulfide (DMS) may impact global climate through the formation of gaseous sulfuric acid, which can yield secondary sulfate aerosols and contribute to new particle formation. While oceans are generally considered the dominant sources of DMS, a shortage of ecosystem observations prevents an accurate analysis of terrestrial DMS sources. Using mass spectrometry, we quantified ambient DMS mixing ratios within and above a primary rainforest ecosystem in the central Amazon Basin in real-time (2010–2011) and at high vertical resolution (2013–2014). Elevated but highly variable DMS mixing ratios were observed within the canopy, showing clear evidence of a net ecosystem source to the atmosphere during both day and night in both the dry and wet seasons. Periods of high DMS mixing ratios lasting up to 8 h (up to 160 parts per trillion (ppt)) often occurred within the canopy and near the surface during many evenings and nights. Daytime gradients showed mixing ratios (up to 80 ppt) peaking near the top of the canopy as well as near the ground following a rain event. The spatial and temporal distribution of DMS suggests that ambient levels and their potential climatic impacts are dominated by local soil and plant emissions. A soil source was confirmed by measurements of DMS emission fluxes from Amazon soils as a function of temperature and soil moisture. Furthermore, light- and temperature-dependent DMS emissions were measured from seven tropical tree species. Our study has important implications for understanding terrestrial DMS sources and their role in coupled land-atmosphere climate feedbacks. 1. Introduction This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distri- bution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. JARDINE ET AL. Volatile-reduced sulfur compounds are continuously exchanged between the atmosphere and the biosphere, with natural gas phase emission estimates of 65 ± 25 teragrams of sulfur per year (Tg S a 1 ) and anthropogenic emissions of 93 ± 15 Tg S a 1 [Andreae and Jaeschke, 1992]. Reduced sulfur species influence processes such as air pollution and acid rain via the production of sulfuric acid [Kanda and Tsuruta, 1995; Staubes et al., 1989; Zhigang et al., 2010], which is also considered the most important chemical component in new aerosol particle formation (NPF) [Kulmala et al., 2004; Sipila et al., 2010]. Through the formation of secondary sulfate aerosols, which can act as potent cloud condensation nuclei (CCN), dimethyl sulfide (DMS, CH 3 SCH 3 ) emissions from marine phytoplankton were hypothesized to have a significant impact on global climate [Lovelock et al., 1972], giving rise to the hypothesis (Charlson, Lovelock, Andreae, and Warren (CLAW) hypothesis) of a strong biological control over climate through a feedback loop that operates between ocean ecosystems and the atmosphere [Charlson et al., 1987]. While other marine sources of CCN, such as organics and sea-salt aerosols, are potentially more important [Quinn and Bates, 2011], model simulations suggest that DMS emissions are nonetheless a significant driver of oceanic cloud formation, its properties, and precipitation patterns [Thomas et al., 2010]. Over the remote continents, e.g., Amazonia and central Siberia, secondary organic matter dominates the chemical composition of aerosols in the optically and cloud microphysically active size range [Chi et al., 2013; Poschl et al., 2010]. However, the mechanisms leading to NPF in these regions are still unclear, and even relatively small amounts of gaseous sulfuric acid formed from the oxidation of DMS might be important through their role in facilitating NPF. ©2014. The Authors.