Spatial and diel variability in the emissions of some biogenic sulfur compounds from a Florida Spartinaalterniflora coastal zone

Aaorpkrr LPirommr Vol. 21. No. 1. pp. 9al-990. ooo4-6981/%7 Printed in Gre.al Bnuin. Q 1987 Pergamon Journals Ltd. SPATIAL AND DIEL VARIABILITY IN THE EMISSIONS OF SOME BIOGENIC SULFUR COMPOUNDS FROM A FLORIDA SPARTINA ALTERNIFLORA COASTAL ZONE WILLIAM Z. DE MELLO, DAVID J. CCK~PER t, WILLIAM J. COOPER *, ERIC S. SALRMAN, ROD G. ZIKA, DENNIS L. SAVOIE and JOSEPH M. PROSPERO Rosenstiel School of Marine and Atmospheric Science, Univcnity of Miami, Miami, FL 33149, U.S.A. and *Drinking Water Research Center, Florida International University, Miami, FL 33199. U.S.A. (Firsr receiued 27 May 1986 and injinolform I I August 1986) Abstract-Emission rates of the biogcnic reduced sulfur gases dimethyl sulfide, dimethyl disulfide, carbon disulfide and hydrogen sulfide were measured from several environments within a Florida Sparrino olfernijoro coastal zone. Spatial and diel variability was observed in the emission rates of all the sulfur gases. The speciation and magnitude ofsulfur emissions can be related to site elevation and the spatial variability of vegetation coverage. Dimethyl sulfide appears to be a metabolic byproduct of S. olrerniflora. Key word index: Dimethyl sulfide, hydrogen sulfide, dimethyl disulfide. carbon disulfide. biogenic sulfur emissions, Sparlina olferniflora. INTRODUCTION In recent yean, interest in the natural input of volatile sulfur gases to the atmosphere has increased because of their importance in balancing the global S cycle and their contri- bution to the acidity of rainfall. Emissions of biogcnic S compounds have been measured directly over continental and coastal areas (Steudler and Peterson. 1985; Jdrgensen and Okholm-Hansen. 1985; Cooper er cl., 1987; and references therein). Most of these measurements were conducted over salt marshes. in particular Sportino alternifora marshes, and areas of mudfiats. Dimethyl sulfide was usually found to be the predominant compound emitted from vegetated areas; from mudflats the major compound emitted was H,S. Other than this broad generalization. however, there is a lack of data concerning dicl or spatial variability in the reported emission rates. Seasonal changes in the emission rates of reduced S compounds from a New England S. olferniflora marsh were reported by Steudler and Peterson (1985). and extremely short term, tidally induced, changes in HxS emission rates from a Florida S. olrernifloro zone were reported by Cooper er al. (1987). This report extends our previous data set of the emission fluxes of dimethyl sulfide (DMS), HIS, carbon disulfide (CS,)and dimethyl disulfide (DMDS) to include the elfects of spatial variability and of temporal variability on a diel scale. STUDY SITE The present study wasconducted during May and October 1985 and January 1986 at the St. Marks National Wildlife Refuge, Florida (Fig. 1). Stands of the saltmarsh cordgrass S. olrernifloro ranged from 30 to SO cm tall and occupied a zone about IS m wide seaward of the extreme high tide mark. At this locale the substrate is a fine-grained quartz sand. Unvegetated areas within the cordgrass had a thin oxic top layer, about 0.5 cm thick. and an underlying dark layer t To whom correspondence should be addressed. Fig. 1. Sampling site location. St. Marks National Wildlife Refuge, Florida, U.S.A. charactcrimd by a strong odor of HIS. The thickness of the oxic layer within the cordgrass was variable but generally ranged between 5 and 1Ocm. Samples were taken at two different locations in the S. alrernfloro: a wet site flushed by at least one high tide each day; and a drier, more oxic, site close to the extreme high tide mark. Samples were also taken at an adjacent bare sand site within the wet S. ulrernifloro stand. SAMPLING AND ANALYTICAL METHODS The sampling and analytical techniques have been de- scribed in detail previously (Cooper cr cl/., 1987). Briefly, samples of S compounds emitted from the soil surface were taken using Teflon lined dynamic flow chambers. DMS. CS2 and DMDS were trapped on Teflon loops at - 183°C. and analyxcd gas chromatographically using a Chromosil 330 column (Supelco, Inc.. Rellefonte, PA) and a S specific Ilame