Naslov
Seasonal variations of reduced sulfur species in a stratified seawater lake (Rogoznica Lake, Croatia) ; evidence for organic carriers of reactive sulfur

Autori
Bura-Nakić, Elvira ; Helz, G.R. ; Ciglenečki-Jušić, Irena ; Ćosović, Božena

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
GEOCHIMICA ET COSMOCHIMICA ACTA, 73(13) / - , 2009, A175-A175

Skup
Goldschmidt conference

Mjesto i datum
Davos, Švicarska, 21.06.2009. - 26.06.2009

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
reduced sulfur species; Rogoznica Lake; organic carriers of reactive sulfur

Sažetak
By voltammetry, we measured total reduced sulfur species (RSS), as well as a non-volatile fraction (i.e. not gas-stripped at pH ~2) in a seasonally stratified, saline lake over a one year period. In the upper, oxic waters, total and non-volatile RSS are equal within uncertainty ; they display little vertical or seasonal variation from winter to late summer, implying no direct link to concurrent photosynthesis. Both fractions rise sharply when stratification breaks down in autumn. Based on decay rate, RSS during mixing events is attributed mainly to dissolved S8 from oxidation of sulfide and decomposition of inorganic polysulfides that formed below the pycnocline. At other times, limited variations of RSS exclude hydrophobic and volatile S8 as a major species. During stratification periods, oxic-water RSS (averaging 8.7 nM) appears to be associated with organic macromolecules, perhaps as adsorbed S8 or covalently bound RSn- or RSnR'. Below the pycnocline, total RSS is dominated by ≤ 5 mM S-II, present as H2S + HS- and as inorganic polysulfides (HxSnx-2) ; metal-bound S-II (chiefly thiomolybdates) must be ≤ 1% of total RSS. Less abundant non-volatile RSS is attributed to dissolved zero-valent sulfur (S0) in inorganic polysulfides. Assuming that organic S0 species are negligible in deep waters, the equilibrium distribution of all inorganic polysulfide ions is calculated ; S52- is found to predominate. We propose that the anoxic waters act as a zero-valent sulfur reactor, creating S0-containing, dissolved organic macromolecules that are dispersed through the lake by mixing events, explaining subsequent RSS in oxic waters. Voltammetrically determined RSS in oxic natural waters are often described as “sulfide” or “metal complexed sulfide”, implying an oxidation state of S-II ; we conclude that RSS in oxic Rogoznica Lake waters is mainly S0. Largely overlooked in previous studies, dissolved S8 is likely to be toxic and may have contributed to mass mortality in this lake during a mixing event in 1997.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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