temporal and spatial variation of sulfur-gas-transfer between coastal marine sediments and the...

*Corresponding author. Present address: Institute of ForestBotany and Tree Physiology, Albert-Ludwigs-University, AmFlughafen 17, D - 79085 Freiburg i. Br., Germany. Fax: 0049 761203 8302; e-mail: [email protected]

Atmospheric Environment 33 (1999) 3487}3502

Temporal and spatial variation of sulfur-gas-transfer betweencoastal marine sediments and the atmosphere

JoK rg Bodenbender, Reiner Wassmann, Hans Papen, Heinz Rennenberg*

Fraunhofer-Institute for Atmospheric Environmental Research, Kreuzeckbahnstra}e 19, D-82467 Garmisch-Partenkirchen, Germany

Received 30 April 1998 rceived in revised form 29 September 1998; accepted 1 October 1998

Abstract

The spatial and temporal variability of sulfur gas #uxes (H2S, COS, CH

3SH, DMS, and CS

2) at the sediment}air

interface were studied in the intertidal Wadden Sea area of Sylt-R+m+ (Germany/Denmark) during eight measuringcampaigns between June 1991 and September 1994. Measurements were performed mainly at four sites in a shelteredintertidal bay of approximately 6 km2 (KoK nigshafen) and discontinuously in a wider range of the 400 km2 Sylt-R+m+tidal #at area. In situ #uxes of the S-gases were determined by a dynamic chamber technique focusing on dry sedimentperiods. Additional experiments were conducted in order to determine changes in S-gas concentrations in the sedimentbetween the surface and 70 cm depth.

In most cases H2S was the dominant S-gas emitted from the sediment to the atmosphere, contributing up to 70% of the

total S-emission at this interface. Mean H2S emission rates ranged between 0.07 and 9.95 lg Sm~2h~1. Both emission

rates and relative contribution of H2S were lowest from "ne sand and highest from muddy sites. Diurnal variation of H

2S

emission was evident in summer and fall with up to 10-fold higher rates during night than during the day. Distinctseasonal variation of H

2S-transfer between the sediment and the atmosphere was observed with higher emission rates in

the summer than in spring or fall. The emission of H2S to the atmosphere was smaller by a factor of 1600}26 000 than the

H2S produced from sulfate reduction. Apparently, the e$ciency by which H

2S produced in the sediment is retained and

reoxidized by biogeochemical sediment processes is extremely high. Carbonyl sul"de (COS) was emitted with relativelyconstant rates in space and time with mean #ux rates ranging between 0.24 and 2.0 lg Sm~2h~1. Carbon disul"deemission rates were comparable to those of COS and varied between 0.3 and 2.23 lgS m~2 h~1. DMS played a minorrole in the S-gas transfer from uncovered sediment areas contributing between 3.1 and 23% to total S-emission from thesediment to the atmosphere. ( 1999 Elsevier Science Ltd. All rights reserved.

Keywords: Sediment}atmosphere #uxes; S-gas emission; Deposition; H2S; COS; DMS; CS

2; CH

3SH; Wadden Sea;

Sulfur

1. Introduction

Sulfur plays an important role in atmospheric acid}base chemistry and in the formation and growth of aero-sol particles. It originates either from natural processes orfrom anthropogenic activity (Bates et al., 1992). Natural

1352-2310/99/$ - see front matter ( 1999 Elsevier Science Ltd. All rights reserved.PII: S 1 3 5 2 - 2 3 1 0 ( 9 8 ) 0 0 3 5 1 - 3

biogenic sources are thought to constitute a large frac-tion of the atmospheric sulfur burden (Aneja, 1990). Theinterest and research in natural sulfur gases has de-veloped rapidly during the last two decades. An impor-tant incentive in this development has been the need toevaluate the role of biogenic sulfur emissions into theatmosphere in relation to man-made emissions which arein the range of 93$15 Tg S per year (J+rgensen andOkholm-Hansen, 1985). Estimates of the total yearlycontribution from natural sources oscillate with an am-plitude of $25 Tg S around a value of about 65 TgS which re#ects the uncertainty of present measurements(Andreae and Jaeschke, 1992).

Because of di!erences in the atmospheric reaction vel-ocities, two groups of gaseous reduced sulfur compoundsare recognized. The more labile compounds, hydrogensul"de (H

2S), dimethyl sul"de ((CH

3)2S), methyl mercap-

tan (CH3SH) and carbon disul"de (CS

2) have tropo-

spheric residence times in the range of only a few days.With the exception of CS

2, which is partly oxidized to

COS, they are mainly oxidized by tropospheric OH toSO

2and sulfate, and return to the surface by dry and wet

deposition (Gries et al., 1994). On the other hand, car-bonyl sul"de (COS) is relatively inert in the troposphereand di!uses readily into the stratosphere where it under-goes photodissociation and photooxidation to SO

2, and

further oxidation to sulfate aerosol particles (Taubmanand Kasting, 1995). Stratospheric sulfate aerosols areimportant because of their e!ects on the radiationbudget. They may also provide surfaces for heterogen-eous reactions that could a!ect stratospheric ozone levels(Chin and Davis, 1995; Goss et al., 1995). Thus, theclimatic signi"cance of the natural atmospheric sulfurcycle is di$cult to assess without proper quanti"cation ofsulfur emissions from natural sources. Attempts to esti-mate natural sulfur emissions have been fraught withboth a paucity of data and high natural variability.

Marine tidal #ats are areas of extreme complexity andbiological activity. They serve as both sources and sinksof a wide variety of compounds and materials. In theseareas sulfur plays a major role in biological processes,because of the relatively high concentration of sulfate inmarine waters and sediments (Can"eld et al., 1993). Gas-eous sulfur compounds appear as intermediate productsof a diverse series of biological and chemical processes inthe natural sulfur cycle including a complex pattern ofrespiration and fermentation processes (Kelly and Smith,1990). Studies performed in coastal marine environmentsshowed particularly high sulfur emission rates suggestingthat these environments may contribute signi"cantly tothe local atmospheric sulfur budget (Aneja, 1990). Hydro-gen sul"de (H

2S) and dimethyl sul"de ((CH

3)2S) seem

quantitatively to be the most important sulfur gases incoastal marine environments (Steudler and Peterson,1984). Hydrogen sul"de is primarily produced by dis-similatory sulfate reduction which is the major min-

eralisation pathway in marine sediments (J+rgensen,1982), but the amount of sul"de turned over at thesediment surface by chemical or biological reactions isprobably vastly in excess of the amount escaping thesediment/atmosphere interface (Kelly and Smith, 1990).Main source of DMS in marine environments may be thecleavage of dimethylsulfoniopropionate (DMSP) pro-duced by di!erent kinds of algae and cyanobacteria.Dimethyl sul"de is the primary sulfur compound presentin open ocean waters and may account for 90% of theS-#ux from the oceans to the atmosphere (Aneja, 1990).Bacterial activity is thought to be the major biogenicsource of COS and CS

2which are formed as intermedi-

ates in various biogeochemical processes in marine sedi-ments (Ferek and Andreae, 1984). In the atmosphere CS

2is photochemically oxidized to carbonyl sul"de (Kellyand Baker, 1990). Both sulfur compounds are assumed tocontribute around 10% to the total natural sulfur #ux tothe atmosphere (Kelly and Smith, 1990). However, thebulk of data on S-gas-#uxes from marine coastal regionswas determined in salt marshes, whereas measurementsfrom tidal #ats are scare and data from the Wadden Seaare lacking completely.

The Wadden Sea bordering the coasts of the Nether-lands, Germany and Denmark is one of northern Euro-pe's most unique marine ecosystems. In recent years,increasing loads of nutrients, organic wastes and toxiccompounds have adversely a!ected the Wadden Sea.Some of the consequences are a general increase ofgrowth and coverage of macroalgae and an expansionof anoxic sediment surfaces. These changes may result inincreasing S-gas-emissions from sediments into the atmo-sphere. To gain information about the quantity and therange of S-gases emitted from Wadden sediments, sulfurgas #uxes between di!erent sediment types and the atmo-sphere were analysed. The measuring program was de-signed to determine the spatial and temporal variationsof the emission of the abundant sulfur gases H

2S, COS,

DMS, CS2

and CH3SH. Since the variation of trace gas

#uxes re#ects the dynamics of biological and physico-chemical processes, the results of the in situ measure-ments of S-gas #uxes constitute a tool to record tidal,diurnal, and seasonal cycles.

2. Materials and methods

2.1. Experimental sites and sampling period

Measurements were performed at sites located in theKoK nigshafen, a sheltered intertidal bay of approximately6 km2, in the northern part of the Island of Sylt (Ger-many), but also in a wider range of the Sylt-R+m+ tidal#at area (Fig. 1). Normal tides had an amplitude of 1.7 m,salinity varied between 29 and 33& during the time of

3488 J. Bodenbender et al. / Atmospheric Environment 33 (1999) 3487}3502

Fig. 1. The measuring sites in the KoK nigshafen and in the southern part of the Sylt-R+m+-tidal #at area: (FS) "ne sand, (CS) coarse sand(MS) muddy sand, (M) silty mud, (BTS) Buttersand, (RLS) Raulingsand, (MTS) Middlesand.

the study. Sediment types ranged from coarse sand over"ne sand (the most common type) and muddy sand tohigh-organic silty mud. Seagrasses (Zostera marina andZ. noltii) were present in parts of both muddy and sandyareas. Benthic microalgae were abundant and macro-algae (;lva sp. and Enteromorpha sp.) often covered thesediment surface throughout summer and fall, especiallyin the inner organic-rich part of the KoK nigshafen. The

benthic fauna was rich, both in terms of numbers andbiomas. A prominent feature in large areas of the bay wasthe presence of the lugworm Arenicola marina, well-known for its strong sediment reworking and ventilationcapability (Reise, 1985).

S-gas-#uxes between the sediment and the atmospherewere measured mainly at four sites in the northwesternand southern part of the KoK nigshafen (Fig. 1). In the

J. Bodenbender et al. / Atmospheric Environment 33 (1999) 3487}3502 3489

northwestern part measurements were carried out ata "ne sand, muddy sand and silty mud site, in the south-ern part at a coarse sand site. For characterization of thesites, water content (weight loss after 24 h at 1053C) andbulk organic matter content (weight loss on ignition ofdried samples after 6 h at 5203C) were determined in theupper 15 cm of the sediment:

(1) The "ne sand site (FS) was highly water-permeableand dominated by large specimens of A. marina. Itwas characterized by low and almost constant waterand organic matter content of about 20 and0.4}0.5%, respectively, at the depth examined.

(2) The muddy sand site (MS), the &&transition area'' be-tween sand and mud was characterized by a 3}6 cmthick muddy coverage and a more coarse sand tex-ture with increasing depth. Water and organic mattercontents were about 40 and 4.3%, respectively, in theupper part but declined rapidly below 2 cm depth, con-comitant with a gradual transition towards a sandysediment texture in subsurface layers. The muddysand site showed a patchy cover of seagrass (Zosterasp.), a high abundance of cockles (Cerastoderma sp.)and low abundance of A. marina.

(3) The silty mud site (M) had a muddier texture andwas located in the inner, organic rich part of theKoK nigshafen. Generally, the mud site showedthe highest water and organic matter content rangingfrom 40 to 50% and 2 to 5.7%, respectively,between 15 cm depth and the sediment surface.The sediment harbored very few A. marina and noseagrasses.

(4) The coarse sand site (CS) in the southern part of theKoK nigshafen showed a sparse and scattered occur-rence of A. marina and a patchy cover of Zostera sp..The water and organic matter contents were compa-rable to that of the "ne sand site in the northwesternpart of the KoK nigshafen.

The measuring sites outside of the KoK nigshafen werelocated in the southern part of the Sylt-R+m+-tidal #at atthe "ne sandy sediments of Buttersand (BTS), Raulin-gsand (RLS) and Middlesand (MTS) (Fig. 1). The struc-ture of theses sediments was comparable to that of the"ne sand site in the KoK nigshafen but with less share ofbigger corn size fractions. Seagrasses and macroalgaewere not present and the occurrence of A. marina waslower than in the KoK nigshafen.

In the present study measurements were performed onsectors without seagrass or green algae vegetation; theinfaunal abundance was not considered. Trace gas #uxeswere monitored during eight measuring campaigns be-tween June 1991 and May 1994. Within this period, 626#ux rates of each compound were determined. Concen-tration gradients of gaseous S-compounds in the sedi-ment were determined during September 1992, March

1993 and May 1994 at the "ne sand (FS), muddy sand(MS) and silty mud site (M).

2.5. Sampling of S-gases and S-gas analysis

Fluxes of gaseous sulfur compounds between sedimentand atmosphere were determined with a dynamic cham-ber made of glass and te#on (Fig. 2A). The chambercovered an area of 0.138 m2 and enclosed an air volumeof 26 l. It was placed in a frame on the tidal #at at lowtide. In order to avoid physical disturbance of the sedi-ment, which could lead to arti"cially high emission rates,the frame was placed on the sediment surface during theprevious low tide. A continuous #ow of ambient air wassucked through the chamber at a #ow rate that ex-changed the chamber volume twice per minute. A Te#on-covered fan was mounted inside the chamber to ensurerapid mixing of the air in order to eliminate vertical S-gasgradients inside the chamber. Since the high reactivity ofgaseous sulfur compounds demanded separation of thesampling and the analytical procedure, the gaseous sulfurcompounds were "rst collected by the concentrationtechnique developed by Haunold et al. (1989). Air sam-ples from inside the dynamic chamber and from ambientair were collected simultaneously by a dual port pumpwith rates of 200 mlmin~1 in U-shaped glass tubes im-mersed in a dewar containing liquid argon (!1863C)(Fig. 2A). This procedure ensured cryogenic trapping ofsulfur gases but excluded nitrogen and oxygen. Sincecryogenic concentration leads to a co-trapping of waterand oxidants, such as OH-radicals and ozone, whichwould reduce the e$ciency of the sampling system espe-cially with regard to H

2S and DMS, a naphion dryer for

the removal of water and a cotton scrubber for theremoval of oxidants were used in each sampling tube(Hofmann et al., 1992). The sampled air volume variedbetween 2 and 4 l. After collection, the frozen air sampleswere sealed by "ve-port Te#on valves and transported inliquid argon to the laboratory for subsequent analysis.

In the laboratory, the sampling loops were connectedto the N

2-carrier gas stream of the gas chromatograph

(Fig 2B). All tubing and valves used in the analyticalsystem were made of PFE-Te#on. For desorbtion of thedi!erent S-gas-species, one of the sample loops was im-mersed in a water bath. For focusing the released S-gasspecies were transferred with the N

2-carrier gas stream to

a second small W-shaped loop and trapped againcryogenically. After a second desorption step, sampleswere swapped with the N

2-carrier gas stream onto the

GC-column "lled with Carbopack BHT 100. The di!er-ent S-compounds were separated using a linear temper-ature program from !5 to 803C. The sulfur gases weredetected by an FPD (#ame-photometric detector); theanalog signals were stored and quanti"ed by an com-puter integration system. The mean retention times of thedi!erent S-compounds on the GC column were 0.55 min


Fig. 2. Dynamic chamber system used for the in-situ sampling of the gaseous reduced S- compounds (A) and analytical setup for S-gasanalysis in the laboratory (B).

for H2S, 1.20 min for COS, 2.35 min for CH

3SH,

4.20 min for DMS and 4.8 min for CS2. Identi"cation

and calibration of the di!erent S compounds wereachieved by the daily use of permeation tube standards.The permeation standards were thermostated in an ovenat 303C and kept under constant #ow of N

2. The sensitiv-

ity of the detecting system was 7.5]10~6 lg S per samplewhich corresponded to a #ux rate of 0.02 lg Sm~2 h~1.The recovery e$ciencies were determined by internalsulfur standards introduced to the sample air stream.Recoveries ranged from 86.7$7.8% (CH

3SH) up to

94.1$4.2% (COS). The trapping e$ciencies of thecryogenic traps varied between 76.6$8.2% (CH

3SH)

and 95.4$4.1% (COS). The #ux rates of the S-tracegases were calculated from the concentration di!erencebetween the ambient air and chamber air using

FX"

(cCX!c

AX)Q

MwXA

TEXRE

X(1)

with FX

being the #ux rate of the di!erent sulfur com-pounds (lg S m~2 h~1); c

CXthe S-gas concentration with-

in the chamber (lg S l~1); cAX

the S-gas concentration ofthe ambient air (lg S l~1); Q the gas stream through thechamber (l h~1); A the chamber area (0.138 m2); Mw

Xthe

molecular weight of the di!erent S-compounds (g mol~1);TE

Xthe trapping e$ciencies (%) and RE

Xthe recovery

e$ciencies (%).The concentrations of S-compounds in chamber and

ambient air were calculated by

c(CX)

!c(AX)

"

Qu(CX)

!Qu(AX)

SV0-

(2)

with QuCX

being the quantity of S-compounds in thechamber (lg); Qu

AXthe quantity of S-compounds in the

ambient air (lg); S70-

the sampling volume (l); cCX

theS-gas concentration within the chamber (lg S l~1) andcAX

the S-gas concentration of the ambient air (lg S l~1).

2.6. S-gas gradients in the sediment

Concentration gradients of gaseous S-compounds inthe sediment were determined using Plexiglas tubes. The


Fig. 3. Gas sampling system for the collection of gaseous S-compounds in the sediment.

tubes contained 18 di!usion chambers arranged in40 mm steps at a lengths of 800 mm (Fig. 3A). Eachdi!usion chamber had a diameter of 30 mm and a vol-ume of 21.2 cm~3. The Te#on-coated di!usion chamberswere covered by a thin Te#on membrane (25 lm) whichwas permeable to the sulfur gases investigated. The sea-ling between the individual di!usion chambers wasachieved by a silicon mat which was pressed by a Plexi-glas cover screwed on the tube body (Fig. 3B and C).Four drillings in the 10 mm thick Plexiglas cover ensuredunimpeded gas di!usion transfer between each chamberand the sediment. For #ushing the chambers and collect-ing sample air two drillings at the side of each chamberwere used. Sealing was achieved by septa pressed byanother Plexiglas cover that contained holes for syringeneedle connection (Fig. 3B and C).

Before sampling was started, the chambers were#ushed with nitrogen to avoid oxygen input into deepersediment layers. Then the tubes were knocked into thesediment and left for an incubation period of 36 h. Afterremoval from the sediment, the tubes were cleaned andtransferred to the laboratory for S-gas analysis. Thedi!usion chambers were connected consecutively withtwo siteport needles and Te#on tubes to the carrier gasstream of the gaschromatograph. Between outlet of thedi!usion chambers and the inlet of the GC-columna small W-shaped loop immersed in liquid argon wasinstalled to focus the released S-gas species. The desorp-

tion for sweeping the S-compounds with the N2-carrier

gas stream onto the GC-column was performed by im-mersing the W-loop in a warm water bath. SubsequentS-gas analysis and calibration of the GC were performedas described above. The whole analytical procedure forone complete tube lasted ca. 3 h.

3. Results

3.1. Hydrogen sulxde (H2S)

The transfer of H2S between sediment and the atmo-

sphere showed the highest spatial, seasonal and diurnalvariations of the sulfur compounds investigated. H

2S-

#uxes varied between deposition rates of 3.2 lg Sm~2

h~1 and emission rates of up to 19.3 lg S m~2 h~1. Inthe KoK nigshafen the highest H

2S emissions were found in

the silty mud (station M) followed by muddy sand (MS)and sandy sites (FS and CS) (Fig. 4). The 24 h meanemission rates at the sandy sites ranged from0.07$0.14 lg Sm~2 h~1 in early spring (March 1993;n"39) up to 2.15$0.53 lg Sm~2h~1 in August 1991(n"59), whereas between 3.02$0.53lg H

2S-S m~2h~1

(March 1993; n"39) and 9.95$5.26 lgH2S-S m~2h~1

(September 1992; n"35) were emitted from the silty mudto the atmosphere (Fig. 3). Mean emission rates at themuddy sand (MS) ranged from 0.61$0.27 lg Sm~2h~1

(March 1993; n"32)) to 5.22$1.04 lg Sm~2h~1

(July/August 1992; n"37) (Fig. 4). At the outer sandsmeasurements could only be achieved during the day inJuly and September 1992. The 45 H

2S #ux rates deter-

mined varied between !0.26 and 1.09 lg Sm~2 h~1;mean H

2S emissions ranged from 0.04$0.06 lg Sm~2

h~1 (Mittelsand, September) to 0.19$0.72 lg Sm~2h~1

(Buttersand; July). Compared to the mean H2S emissions

observed during the corresponding time periods at "nesand (FS) in the KoK nigshafen, the values determined atthe outer sands were 4}14 times lower (Fig. 7).

The measurements performed between May and Octo-ber substantiated the dominant role of H

2S in the ex-

change of sulfur at the sediment/atmosphere interface.Depending on time and site H

2S contributed between

33.2% ("ne sand site, May 1994, n"23) and 69.8% (siltymud, September 1992, n"35) to total S-emission (Fig 5).At low temperatures in early spring emission rates werelower compared to other seasons, but spatial di!erenceswere still apparent. In July}August 1992 mean H

2S-

emissions from silty mud (M) were about 3 times higherthan the H

2S #uxes in March 1993 (Fig. 4; Table 1). The

#uxes observed in May and September at this site were inbetween the #uxes measured in early spring and summer(Fig. 4). At the muddy sand (MS) and sandy site (FS)H

2S-transfer showed an even more distinct seasonal vari-

ation with 8.6 (MS) and 20.4 times (FS) higher mean


Fig. 4. Mean #ux rates of the four gaseous sulfur compounds H2S, COS, DMS and CS

2at the "ne sand (FS), coarse sand (CS), muddy

sand (MS) and silty mud (M) site in the KoK nigshafen. Arrows indicate the presentation of data in Table 1.

emissions in July/August 1992 than in March 1993 (Fig.4; Table 1). Similar observations were made at the sandysites between June 1991 and April 1992. At the "ne sandstation (FS) mean emission rates increased twice from1.22$0.45 lg Sm~2 h~1 in June (n"64) to 2.15$0.53 lg Sm~2 h~1 in August 1991 (n"59). From thecoarse sand (CS) mean H

2S #uxes of 1.18$

0.32 lg Sm~2 h~1 were determined in October 1991(n"73) that were ca. 11-fold higher than the mean emis-sions in April 1992 (n"30) at this site.

Compared to the transfer rates of the other S-com-pounds investigated H

2S #uxes at the "ne (FS) and

coarse sand (CS) site in March and April were of minorsigni"cance making up as little as 3% of total S-emission,whereas at the muddy sand (MS) and silty mud (M) theshare of H

2S to total S-emission was ca. 67%, and, thus,

in the same range as in the warmer periods of the year(Fig. 5; Table 1).

During the measuring campaigns conducted betweenMay and October a diurnal pattern of H

2S emission was

generally observed at the sites investigated with signi"-cantly (p(0.01) higher emissions at night than duringday (Fig. 5). The mean nocturnal H

2S-emissions ex-

ceeded the mean emission rates measured during the day

from 1.6- (muddy sand, August 1991) up to 3.2-fold ("nesand, September 1992) (Fig. 5; Table 1). Fig. 6 shows anexample for the rate and the pattern of S-gas transfermeasured at the silty mud station (M) in the Northwestpart of the KoK nigshafen. The H

2S-#uxes determined dur-

ing consecutive ebb tides in July/August 1992 (Fig. 6,black symbols) and September 1992 (Fig. 6, open sym-bols) showed night H

2S #uxes of up to 19.1lg Sm~2 h~1,

whereas minimum #uxes of only 0.34 lg Sm~2 h~1 inJuly/August or even H

2S-deposition in September was

observed at maximum light intensity during the day. Inlate winter and early spring either no, or an inversediurnal pattern with higher rates during the day than atnight was determined at the sites (Fig. 5).

3.2. Carbonyl sulxde (COS)

Mean emission rates of COS were relatively constantwith regard to both sites and seasons, ranging from0.24$0.13 lg Sm~2 h~1 (coarse sand, October 1991) to2.0$0.66 lg Sm~2 h~1 (silty mud, August 1992) (Fig. 4).COS #uxes from the muddy site were generally higherthan from the "ne and muddy sand. In July}August 1992this di!erence was signi"cant and amounted to a factor


Fig. 5. Mean daily and nocturnal #ux rates of the four gaseous sulfur compounds H2S, COS, DMS and CS

2at the "ne sand (FS), coarse

sand (CS), muddy sand (MS) and silty mud (M) site in the KoK nigshafen. Arrows indicate the presentation of data in Table 1.

of ca. 2 (Fig. 4). Between the sandy and muddy sand sitesuniform spatial variations were not found, but because oflower levels of emission of other S-species, the contribu-tion of COS to total S-emission was about 2-fold higherfrom sand than from mud and muddy sand (Table 1; Fig.5). At the outer sands, COS emission was in the samerange as at the "ne sand site (FS) in KoK nigshafen mea-sured at the same time period. Because of low ratesof H

2S emission, COS was the dominant gaseous sul-

fur compound emitted at the outer sands with meanemission rates ranging from 0.56$0.44 lg Sm~2h~1

(Buttersand; July 1992) to 1.74$0.85 lg Sm~2h~1

(Mittelsand; September 1992) (Fig. 7) and a contributionof COS to total S-emission between 43.7 and 88%(Fig. 7).

A signi"cant seasonal variations was only observed atthe muddy site (M) with highest COS emission rates inJuly/August 1992 and lowest rates in September 1992and March 1993 (Table 1; Fig. 4). At the sandy andmuddy sand stations regular seasonal pattern werenot found, but due to the low emission of H

2S in March

and April COS was the predominant sulfur species

emitted during this time of the year at this sites. At allsites investigated the share of COS to total S emissionwas by ca. a factor of 2 higher in spring then in summer(Table 1).

The release of COS from the sediment followed at allseasons and sites a diurnal pattern with higher rates ofemission during day and lower rates during night (Fig. 5,Table 1). Signi"cant variation of the COS #uxes betweenday and night were found in June and August 1991 at the"ne sand site (FS), in April 1992 at the coarse sand (CS) aswell as in March 1993 at all sites investigated.

3.3. Dimethyl sulxde (DMS)

Fluxes of DMS between uncovered sediment areasand the atmosphere were mostly very low contributing2.6}23% (May 1994) to total S-gas emission. Averageemission rates ranged from 0.12$0.06 lg Sm~2h~1

(silty mud; March 1993) to 2.32$0.76 lg Sm~2h~1

(silty mud, May 1994) (Fig. 4). Spatial di!erences of theDMS transfer between the sites were only detected inAugust 1991 and May 1994. In August the mean DMS


Table 1Mean #ux rates of gaseous S-compounds. Measurements were performed in July}August, 1992 and March, 1993 at three sites in theKoK nigshafen. Day, night and total (day and night), minimum (min) and maximum (max) emission rates and their relative contribution tothe total S-emission are shown

Site (month) n S-gas-#uxes (lg S m~2 h~1)$SE

H2S COS DMS CS

2Total

Fine sand (July}August 1992)Day 30 0.89$0.87 1.03$0.3 0.37$0.24 0.45$0.17 2.75$0.96Night 20 2.51$0.48 0.83$0.19 0.50$0.29 0.35$0.08 4.19$0.59Day#night! 50 1.43$0.59 0.94$0.21 0.43$0.29 0.41$0.15 3.22$0.73Min/Max (7) !0.43/4.32 0.05/2.5 !0.34/1.40 !0.08/1.23Contribution (%) 44.6 29.4 13.3 12.7

Fine sand (March 1993)Day 22 0.07$0.20 1.36$0.60 0.12$0.12 0.86$0.46 2.41$0.79Night 17 0.06$0.17 0.72$0.55 0.12$0.13 0.59$0.49 1.48$0.76Day#night! 39 0.07$0.14 1.04$0.42 0.12$0.09 0.73$0.34 1.95$0.56Min/Max (5) !0.38/0.43 0.22/1.80 !0.21/0.45 0.13/1.52Contribution (%) 3.3 53.2 6.1 37.4

Muddy sand (July}August 1992)Day 22 2.90$1.26 1.18$0.54 0.40$0.24 1.28$0.40 5.76$1.36Night 15 9.44$1.42 0.83$0.25 0.32$0.24 0.99$0.32 11.6$1.43Day#night! 37 5.22$0.94 1.04$0.34 0.37$0.17 1.18$0.27 7.80$1.04Min/Max (5) !0.18/12.1 !0.14/2.63 !0.23/1.26 0.15/2.37Contribution (%) 66.8 13.3 4.8 15.1

Muddy sand (March 1993)Day 20 0.88$0.49 1.12$0.89 0.19$0.08 0.85$0.32 3.05$1.07Night 12 0.34$0.23 0.45$0.40 0.15$0.13 0.45$0.21 1.37$0.52Day#night! 32 0.61$0.27 0.79$0.49 0.17$0.08 0.65$0.19 2.21$0.60Min/Max (4) !0.10/1.91 !0.37/2.40 !0.06/0.40 0.04/1.66Contribution (%) 27.6 35.5 7.4 29.4

Silty mud (July}August 1992)Day 20 6.88$1.72 2.15$1.09 0.34$0.42 2.27$0.57 11.6$2.03Night 15 14.3$2.22 1.68$0.76 0.53$0.73 2.20$0.42 18.7$2.39Day#night! 35 9.36$1.40 2.0$0.66 0.44$0.42 2.23$0.35 14.0$1.70Min/Max (5) 1.63/19.1 !0.77/5.5 !0.68/1.92 1.03/4.57Contribution (%) 66.7 14.2 3.1 15.9

Silty mud (March 1993)Day 24 3.48$0.84 1.83$0.79 0.14$0.10 0.73$0.29 6.20$1.19Night 12 2.55$0.40 0.79$0.36 0.11$0.05 0.47$0.29 3.92$0.61Day#night! 36 3.02$0.53 1.31$0.49 0.12$0.06 0.60$0.21 5.05$0.75Min/Max (5) 2.09/4.86 0.08/2.45 !0.06/0.41 0.08/1.18Contribution (%) 59.6 25.9 2.6 11.9

n: number of measurements.! Calculated on the basis of the length of day and night.

emission was signi"cantly higher at "ne sand (FS) com-pared to the emission from muddy sand (MS) whereasin May the mean DMS #uxes from the muddy site (M)were about a factor of 2 higher than at the "ne sand site(Fig. 4). About 2}4 times more DMS was emitted fromthe sites investigated to the atmosphere in July/August1992 compared to March 1993 (Table 1). In 1991/1992a similar tendency was observed at the sandy sites with

higher DMS emissions in the summer (June and August)than in autumn (October) and early spring (April) (Fig.4). Except in August 1991 signi"cant diurnal patterns ofDMS #ux rates were not found (Fig. 5). DMS was theonly gaseous sulfur compound investigated which fre-quently showed a dependency on the tidal pattern withhigher emission rates at the beginning of the ebb tide andlower values at the end.


Fig. 6. Total S-gas emission at the "ne sand (FS), coarse sand (CS), muddy sand (MS) and silty mud (M) site in the KoK nigshafen. Arrowsindicate the presentation of data in Table 1.

3.4. Carbon disulxde (CS2)

Mean emissions of CS2

were in the range of the COS#uxes and ranged from 0.3$0.16 lg Sm~2 h~1 (Octo-ber 1991) to 2.23$0.35 lg Sm~2h~1 (July/August 1992).In summer 1992 the transfer of CS

2showed, similar to

H2S #uxes, a pronounced spatial variation with ca. 2 and

5 times higher #ux rates from the muddy site (M) thanfrom the muddy sand (MS) and "ne sand site (FS),respectively (Table 1). A signi"cant di!erence betweenCS

2#uxes from mud and sand was also observed in May

1994. During the other times investigated spatial di!er-ences in CS

2#uxes were not observed (Fig. 4).

Pronounced seasonal variations of CS2#uxes were

only found between July/August 1992 and March 1993.The emissions from silty mud (M) and muddy sand (MS)determined during summer were ca. twice and four timeshigher than the comparable mean emission rates inspring. By contrast, mean summer CS

2#uxes at the "ne

sand site (FS) were ca. half the CS2#uxes measured in

March 1993. With few exceptions CS2

emissions showeda diurnal pattern, similar to COS emissions with higher#uxes during the day than at night. Signi"cant di!erences

between night and day #uxes of CS2

were noticed atMarch 1993 in the muddy sand (MS) and silty mud (M)and in May 1994 at the "ne sand (FS) and silty mud (M).

3.5. Total emission of gaseous sulfur compounds andinterannual variation

Total sulfur emission showed a clear dependence onsite and season. Lowest emission rates were found insand, highest in silty mud; #uxes of gaseous sulfur com-pounds were lower between October and April thanbetween May and September (Fig. 8). The mean S-gas-emission varied season- and site-speci"c between 1.55$0.19 lg Sm~2 h~1 (CS, April 1992) and 14.0$0.8lgS m~2 h~1 (M, July/August 1992). Despite the highspatial and seasonal variations, the interannual varianceof #ux rates determined at the same sites during the sameseason was relatively low. For example, in August 1991and July/August 1992 approximately equal mean H

2S

emission rates were determined and only small variationsin the #uxes of the other sulfur compounds investigatedwere found at the muddy sand site. The interannual


Fig. 7. Mean #ux rates of H2S, COS, DMS and CS

2at the outer sands: BTS*Buttersand, RLS*Raulingsand, MTS*Middlesand,

Fs(KH)*"ne sand (KoK nigshafen).

di!erence amounted only to 26%. Exactly the same in-terannual di!erence of total sulfur gas emission wasfound at the "ne sand site in the summers 1991/1992 asresult of rather uniform mean emissions of COS, CS

2and

DMS and small variations of the H2S #uxes.

Temporal and spatial di!erences of H2S #ux rates were

the main modulating factor responsible for the observedvariations of total sulfur emissions. Emissions of COSand CS

2were of similar signi"cance with a slightly

superior role of COS at the sandy sites and a slightlymore pronounced role of CS

2at silty mud during the

warmer period of the year (Fig. 8). With the exception ofMay 1994 where mean emissions of DMS contributed21% (silty mud) and 23% ("ne sand) to total S-gas-emission, this compound played a subordinate role in thetransfer of gaseous sulfur at the sediment/atmosphereinterface (Fig. 8).

3.6. Correlations between the emissions of diwerent Scompounds and between S-gas transfer and physicalparameters

With few exceptions signi"cant (a(0.05) positive re-lations between COS and CS

2emission were found.

Positive correlations were also observed between DMSand COS or CS

2transfer, respectively. When nocturnal

H2S emissions exceeded the #uxes during the day (May}

September) a distinct negative connection was foundbetween H

2S and COS #uxes, whereas during October,

March and April no or a positive correlation was ob-served.

Compared to the other S-compounds investigated theH

2S transfer showed the most distinct dependency on

physical parameters, such as global radiation and sedi-ment temperature (5 cm depth). In the warmer period of


Fig. 8. Fluxes of gaseous sulfur compounds observed at the silty mud site (M) during two measuring campaigns in July}August 1992(black symbols) and September 1992 (white symbols). Each symbol represents one set of measurements performed at consecutive ebbtides.

the year, H2S emission rates showed negative correlation

to radiation and sediment temperature. During Octoberand April no or opposite correlations were found. COSand CS

2emissions from the sediment were mostly posit-

ively correlated with radiation and sediment temper-ature, COS slightly stronger with radiation, CS

2slightly

stronger with sediment temperature. DMS did not showa uniform relationship to these physical parameters.Numerous measurements imposed a clear negativecorrelation between S-gas #uxes and ambient air con-

centrations. These negative correlations were signi"cantfor COS, H

2S and DMS, but not for CS

2.

3.7. Concentration gradients of gaseous S-compounds inthe sediment

The S-gas concentrations in the sediment were deter-mined during three measuring campaigns, in September1992, March 1993 and May 1994. In March 1993 invest-igations were performed at the silty mud (three replicates)


Fig. 9. Sediment concentrations of the gaseous sulfur compounds COS, DMS and CS2between the sediment surface and 70 cm depth at

the silty mud (black symbols) and the muddy sand site (white symbols). Each kind of symbol represents one measuring interval with thePlexiglas tubes.

and muddy sand site (two replicates) (Fig. 9). At bothstations the S-gas concentrations at the sediments surfacewere only slightly higher than ambient air concentrationsdetermined with the dynamic chamber method. SedimentS-gas concentrations increased strongly in the upper cen-timeters of the sediment. At the silty mud site COSshowed the most pronounced gradient from 2 ppbv atthe sediment surface to values between 44 and 71 ppbv in4 cm depth. The simultaneous increase of the DMS andCS

2concentration was less steep, but also clearly notice-

able. In the muddy sand COS concentrations increasedmore slowly with sediment depth whereas DMS and CS

2showed higher values than in the comparable sedimentlayers in the silty mud. COS concentrations were highestat both sites in the deeper sediment areas, up to 220 ppbvat the silty mud and up to 145 ppbv at the muddy sand.The "t of the COS gradient showed a #at course up to50 cm depth both at station M and MS and a morepronounced increase with increasing depth. The latterincrease was steeper at station MS as compared to sta-tion M.

Investigations performed in September 1992 and May1994 (data not shown) provideded comparable resultsboth in the absolute height of the values and in thepattern of concentrations with increasing sedimentdepth.

4. Discussion

4.1. Hydrogen sulxde

The mean H2S emission rates from Wadden Sea sedi-

ments observed in this study ranged between 0.07 and9.95 lg Sm~2 h~1. They are in the lower range whencompared to results obtained from other intertidal #atsand marshes (0.15}67.8 lg Sm~2h~1; Aneja, 1990), butsimilar to an estimate based on vertical atmosphericgradients in the present study area (4.6 lg Sm~2 h~1;Jaeschke et al., 1978) and to #ux chamber measurementsfrom a Danish estuary (0 to 8.52 lgS m~2 h~1; J+rgensenand Okholm-Hansen, 1985). A higher variation of H

2S

#uxes of 3.3 to 83.1 lg Sm~2 h~1 was observed in a tidalmud#at area at the Northwest coast of Florida (USA) byCooper et al. (1987).

The high H2S emission observed during night (Figs.

5 and 6) indicates a shift in the balance between produc-tion and consumption processes. The lack of benthicphotosynthesis during the night suggests that a reducedO

2-barrier facilitated H

2S transfer from the sediment to

atmosphere (J+rgensen and Okholm-Hansen, 1985). Sul-"de oxidation (ultimately to sulfate) generally accountsfor half or more of the oxygen consumption in marine


sediments (J+rgensen, 1982; Mackin and Swider, 1989).In the presence of an O

2/H

2S interface, sul"de oxidation

may proceed rapidly and directly via oxygen, notably bycolorless sulfur bacteria of the Beggiatoa type (Visscher etal., 1992). Most commonly, H

2S is removed by chemical

reactions in the underlying suboxic zone (or NO3}Mn}

Fe zone) which leads to precipitation e.g. as FeS andFeS

2(pyrite) (S+rensen and J+rgensen, 1987). It has been

assumed that bacterial-mediated and chemically aidedH

2S oxidation to SO2~

4involving manganic oxides, ferric

iron compounds and disproportionation of intermedi-ates in the sulfur cycle (thiosulfate and S

0) may occur in

anoxic sediments (Can"eld, 1993; Can"eld et al., 1993;J+rgensen et al., 1990; Thamdrup et al., 1994). J+rgensenet al. (1990) reported that 68}96% of the produced H

2S

was reoxidized in a variety of marine sediments. There-fore, reoxidation of H

2S contributes more to H

2S

removal than pyrite burial.A comparison of the H

2S emissions measured in this

study with concurrent sulfate reduction rates determinedby Jensen et al. (1994) at the same sites showed that about1600}26 000 times more H

2S was produced than emitted.

The low emission fraction shows the e$ciency by whichsediments retain the H

2S produced during sulfate red-

uction, and indicates a large H2S consumption by

biological and geochemical processes in the sediment.J+rgensen and Ockholm-Hansen (1985) found a compar-able emission fraction in a Danish estuary. It is stillnot completely understood which mechanisms are re-sponsible for the actual H

2S consumption in marine

sediments.In our study the higher emission rates and emission

fractions observed (1) in KoK nigshafen during summer ascompared to early spring, and (2) at muddy relative tosandy sites, may both be a consequence of higher sulfatereduction rates combined with a depletion of O

2and

metal oxides. The observed diurnal, seasonal and spatialdi!erences in H

2S emission may re#ect the availability of

degradable organic matter and the in#uence of light- andtemperature cycles. The spatial heterogenity of the sedi-ment may be a consequence of bioturbation by the richinfaunal community and scattered occurrence of micro-and macrophytobenthos.

4.2. Carbonyl sulxde

Carbonyl sul"de (COS) is formed by biogenic de-composition, by chemical photolysis of organic sulfurcompounds and by chemical oxidation of CS

2and DMS

(Ferek and Andreae, 1984; Andreae, 1992; Kelly et al.,1993). COS emissions determined at the various sites inthe KoK nigshafen and the outer sands were not especiallysite- or time-speci"c. This observation is consistent withother reports showing COS as a minor and rather con-stant S-gas source in marine areas (Harrison et al., 1992).The slight, albeit apparent, diurnal variation of COS

emission, with highest rates during the day might be dueto higher O

2availability and more oxidized conditions,

increasing the potential for oxidation of more reducedsulfur compounds to COS. The present rates rangingfrom 0.24 up to 2.0 lg Sm~2 h~1 are consistent withmean COS emissions of 0.23 to 1.05 lg Sm~2h~1 froma Danish estuary (J+rgensen and Okholm-Hansen, 1985)and emission rates observed in the Colne estuary (GreatBritain) with mean annual #uxes between 0.44 and1.25 lg Sm~2 h~1 (Harrison et al., 1992).

4.3. Carbon disulxde

The biogenic sources of carbon disul"de (CS2) are not

well understood, although biogeochemical and microbialproduction processes in anoxic sediments are thought tobe signi"cant (Andreae, 1985; Kim and Andreae, 1992;Kelly et al., 1993). In the KoK nigshafen both the emissionrates and the contribution of CS

2to the total S-gas

emission were slightly lower or similar to COS with theexception of the more reducing conditions in the muddysediments during summer, when CS

2emissions tended to

be higher. The mean CS2

emissions determined in theKoK nigshafen are clearly higher than the values of 0}0.36lgSm~2h~1 reported by J+rgensen and Okholm-Hansen(1985) for a Danish estuary, but are at the low end of ratesreported from salt marshes (0.19}14.2 lgS m~2 h~1)(Aneja, 1990). The high concentrations of COS and CS

2observed in deeper sediment layers (10}70 cm) comparedto the very low concentrations at the sediment surfacesuggests high consumption rates of both compoundsnear the sediment surface.

4.4. Dimethyl sulxde

The main source of dimethyl sul"de (DMS) is conside-red to be the enzymatic cleavage of DMSP (dimethylsul-fonium propionate) from phytoplankton and macroalgae(Karsten et al., 1990; Aneja and Overton, 1990). DMS isalso produced during metabolism of other methylatedsulfur compounds like S-methylcysteine, syringate,dimethylsulfoxide (DMSO), methylmercaptan (CH

3SH)

and dimethyldisul"de (DMDS) (Kiene, 1988, 1993; Fin-ster et al., 1990). Compared to published DMS-#uxesfrom salt-marshes (2.3}328 lgS m~2 h~1; Steudler andPeterson, 1984; Aneja, 1990) the present DMS #uxesbetween sediment and atmosphere are low. The presentdata contradict the assumption that DMS, together withH

2S, quantitatively dominates biogenic sulfur gas emis-

sion from coastal marine regions. Dacey et al. (1987)suggested that Spartina alterni-ora salt-marshes repres-ent considerable DMS sources because of the highDMSP-concentrations within the plants, whereas un-covered sediment areas show only small DMS-emissionsor were DMS-sinks. Kiene (1988) showed DMS-emissionfrom sediment cores only after inhibition of bacterial


DMS-consumption and concluded that biological DMS-consumption is the main sink for the DMS producedwithin the sediment. Visscher et al. (1992) calculated froma comparison of DMS-consumption and DMS-produc-tion rates of di!erent bacteria populations a completeremoval of the DMS produced within the sediment. TheDMS sediment concentration gradients determined inthis study with high concentrations in deeper areas anda strong decrease nearby the sediment surface supportthis conclusion.

In this study sediment}air #uxes of S-gases were deter-mined only at low-tide situations from uncovered sedi-ment areas. Therefore, further studies are required toexamine S-gas #uxes from green algae mats and acrossthe seawater}atmosphere interface.

Acknowledgements

We thank Dieter BuK chsenschuK tz, Silke MuK ller andElke SchluK ssel for their technical assistance during the"eld and laboratory work. The assistance of the sta!at List Wattenmeerstation is highly appreciated. Thestudy was supported by the Bundesminister fuK r Bildung,Wissenschaft, Forschung und Technologie (BMBF) inthe frame of the SWAP-project (Sylter WattenmeerAustausch-Prozesse).

References

Andreae, M.O., 1985. The emission of sulfur to the remoteatmosphere: background paper. In: Galloway, J.N. (Ed.), TheBiogeochemical Cycling of Sulfur and Nitrogen in theRemote Atmosphere. Reidel, Dordrecht, pp. 5}25.

Andreae, M.O., 1992. The global biogeochemical sulfur cycle* a review. In: Schimmel, D.S., Moore B. (Eds.), Trace Gasesand the Biosphere. UCAR-O$ce for Interdisziplinary EarthStudies, Boulder, CO, pp. 87}128.

Aneja, V.P., 1990. Natural sulfur emissions into the atmosphere.Journal of Air and Waste Management Association 40,469}476.

Aneja, V.P., Overton, J.H., 1990. The emission rate of dimethylsul"de at the atmospheric-oceanic interface. Chemical En-gineering Communication 98, 199}209.

Bates, T.S., Lamb, B.K., Guenter, A., Dignon, J., Stoiber, R.E.,1992. Sulfur emissions to the atmosphere from natural sour-ces. Journal of Atmospheric Chemistry 14, 315}337.

Bodenbender, J., Papen H., 1998. The role of gas #uxes at theinterfaces of sediment/atmosphere and water/atmosphere inthe Sylt-R+m+ Wadden Sea. In: Gaetje, C., Reise K. (Eds.),The Wadden Sea Ecosystem*Exchange, Transport andTransformation Processes. Springer, Berlin, pp. 303}340.

Can"eld, D.E., 1993. Organic matter oxidation in marine sedi-ments. In: Wollast, R., Mackenzie, F.T., Chou, L. (Eds.),Interactions of C, N, P and S Biogeochemical Cycles andGlobal Change, NATO ASI Series I 4. Reidel, Dordrecht, pp.333}363.

Can"eld, D.E., Thamdrup B., Hansen J.W., 1993. The anaerobicdegradation of organic matter in Danish coastal sediments:iron reduction, manganese reduction, and sulfate reduction.Geochimica et Cosmochimica Acta 57, 3867}3883.

Chin, M., Davis, D.D, 1995. A reanalysis of carbonyl sul"de asa source of stratospheric background sulphur aerosol. Jour-nal of Geophysical Research 100, 8993}9005.

Cooper, W.J., Cooper, D.J., Saltzman, E.S., de Mello, W.Z.,Savoie, D.L., Zika, R.G., Prospero, J.M., 1987. Emissions ofbiogenic sulphur compounds from several wetland soils inFlorida. Atmospheric Environment 21, 1491}1495.

Dacey, J.W.H., King, G.M., Wakeham, S.G., 1987. Factors con-trolling emission of dimethylsulphide from salt marshes.Nature 330, 643}645.

Ferek, R.J., Andreae, M.O., 1984. Photochemical production ofcarbonyl sulphide in marine surface waters. Nature 307,148}150.

Finster, K., King, G.M., Bak, F., 1990. Formation of methylmer-captan, dimethylsul"de from methoxylated aromatic com-pounds in anoxic marine and fresh water sediments. FEMSMicrobial Ecology 74, 295}302.

Goss, L.M., Frost, G.J., Donaldson, D.J., Vaida, V., 1995.Photooxidation of CS

2in the near-ultraviolet and its atmo-

spheric amplications. Geophysical Research Letters 22,2609}2612.

Gries, C., Nash, T.H., Kesselmeier, J., 1994. Exchange of reducedsulfur gases between lichens and the atmosphere. Biochemis-try 26, 25}39.

Harrison, R.M., Nedwell, D.B., Shabbeer, M.T., 1992. Factorsin#uencing the atmospheric #ux of reduced sulphurcompounds from North Sea inter-tidal areas. AtmosphericEnvironment 26A, 2381}2387.

Haunold, W., Ockelmann, G., Georgii, H.-W., 1989. NeuartigerGaschromatograph zur Messung von SO

2und reduzierten

Schwefelgasen in Reinluftgebieten. Staub*Reinhaltung derLuft 49, 191}196.

Hofmann, U., Hofmann, R., Kesselmeier, J., 1992. Cryogenictrapping of reduced sulfur compounds using a na"on drierand cotton wadding as an oxidant scavenger. AtmosphericEnvironment 26A, 2445}2449.

Jaeschke, W., Georgii, H.-W., Claude, H., Malewski, H., 1978.Contributions of H

2S to the atmospheric sulfur cycle. Pure

and Applied Geophysics 116, 465}475.Jensen, M.H., Jensen, K.M., Kristiansen, K.D., Kristensen, E.,

1994. Microbial ecology and biochemistry of sediments inKoK nigshafen. Insitute of Biology, Odense Universty, De-nmark. SWAP*Sylter Wattenmeer Austauschprozesse,Zwischenberichte, 1993.

J+rgensen, B.B., 1982. Mineralization of organic matter in the seabed*the role of sulphate reduction. Nature 296, 643}645.

J+rgensen, B.B., Bak F., 1991. Pathways and microbiology ofthiosulfate transformations and sulfate reduction in a marinesediment (Kategatt, Denmark). Applied EnvironmentalMicrobiology 57, 847}856.

J+rgensen, B.B., Bang, M., Blackburn, T.H., 1990. Anaerobicmineralization in marine sediments from the Baltic sea} North sea transition. Marine Ecology Progressive Series59, 39}54.

J+rgensen, B.B., Okholm-Hansen, B., 1985. Emissions ofbiogenic sulfur gases from a danish estuary. AtmosphericEnvironment 19, 1737}1749.


Karsten, U., Wiencke, C., Kirst, G.O., 1990. The {-dimethylsul-phoniopropionate (DMSP) content of macroalgae from Ant-arctica and southern Chile. Botanica Marina 33, 143}146.

Kelly, D.P., Baker, S.C., 1990. The organosulphur cycle: aerobicand anaerobic processes leading to turnover of C

1-sulphur

compounds. FEMS Microbiology Reviews 87, 241}246.Kelly, D.P., Malin, G., Wood, A.P., 1993. Microbial transforma-

tions and biogeochemical cycling of one-carbon substratescontaining sulphur, nitrogen or halogens. In: Murrell, J.C.,Kelly, D.P. (Eds.), Microbial Growth on C

1Compounds.

Intercept, Hampshire, pp. 47}63.Kelly, D.P., Smith, N.A., 1990. Organic sulfur compounds in the

environment: biogeochemistry, microbiology, and ecologicalaspects. Advances in Microbial Ecology 11, 345}385.

Kiene, R.P., 1988. Dimethyl sul"de metabolism in salt marshsediments. FEMS Microbial Ecology 53, 71}78.

Kiene, R.P., 1993. Microbial sources and sinks for methylatedsulfur compounds in the marine environment. In: Murrell,J.C., Kelly, D.P. (Eds.), Microbial Growth on C

1Com-

pounds. Intercept, Hampshire, pp. 15}33.Kiene, R.P., Capone, D.G., 1988. Microbial transformations of

methylasted sulfur compounds in anoxic salt marsh sedi-ments. Microbial Ecology 15, 275}291.

Kim, K.-H., Andreae, M.O., 1992. Carbon disul"de in the es-tuarine, coastal, and oceanic environment. Marine Chem-istry 40, 179}197.

Mackin, J.E., Swider, K.T., 1989. Organic matter decompositionpathways and oxygen consumption in coastal marine sedi-ments. Journal of Marine Research 47, 681}716.

Reise, K., 1985. Tidal Flat Ecology. Springer, Berlin.Skyring, G.W., 1987. Sulfate reduction in coastal ecosystems.

Geomicrobiology Journal 5, 355}374.S+rensen, J., J+rgensen, B.B., 1987. Early diagenesis in sediments

from Danish costal waters: Microbial activity and Mn}Fe}Sgeochemistry. Geochimica et Cosmochimica Acta 51,1583}1590.

Steudler, P.A., Peterson, B.J., 1984. Contribution of gaseoussulphur from salt marshes to the global sulphur cycle. Na-ture 311, 455}457.

Taubman, S.T., Kasting, J.F., 1995. Carbonyl sul"de: no remedyfor global warming. Geophysical Research Letters 2, 803}805.

Thamdrup, B., Fossing, H., J+rgensen, B.B., 1994. Manganese,iron, and sulfur cycling in a coastal marine sediment (AarhusBay, Denmark). Geochimica et Cosmochimica Acta 58, 1}15.

Visscher, P.T., Prins, P.A., van Gemerden, H., 1992. Sulfur cyclingin laminated marine ecosystems. In: Visscher, P.T. (Ed.),Microbial Sulfur Cycling in Laminated Marine Ecosystems.University of Groningen, The Netherlands, pp. 21}32.

Visscher, P.T., Quist, P., van Gemerden, H., 1991. Methylatedsulfur compounds in microbial mats: in situ concentrationsand metabolism by a colorless sulfur bacterium. AppliedEnvironmental Microbiology 57, 1758}1763.


temporal and spatial variation of sulfur-gas-transfer between coastal marine sediments and the...

Documents