Malodorous volatile organic sulfur compounds: Sources, sinks and significance in inland waters

Abstract

Volatile Organic Sulfur Compounds (VOSCs) are instrumental in global S-cycling and greenhouse gas production. VOSCs occur across a diversity of inland waters, and with widespread eutrophication and climate change, are increasingly linked with malodours in organic-rich waterbodies and drinking-water supplies. Compared with marine systems, the role of VOSCs in biogeochemical processes is far less well characterized for inland waters, and often involves different physicochemical and biological processes. This review provides an updated synthesis of VOSCs in inland waters, focusing on compounds known to cause malodours. We examine the major limnological and biochemical processes involved in the formation and degradation of alkylthiols, dialkylsulfides, dialkylpolysulfides, and other organosulfur compounds under different oxygen, salinity and mixing regimes, and key phototropic and heterotrophic microbial producers and degraders (bacteria, cyanobacteria, and algae) in these environs. The data show VOSC levels which vary significantly, sometimes far exceeding human odor thresholds, generated by a diversity of biota, biochemical pathways, enzymes and precursors. We also draw attention to major issues in sampling and analytical artifacts which bias and preclude comparisons among studies, and highlight significant knowledge gaps that need addressing with careful, appropriate methods to provide a more robust understanding of the potential effects of continued global development.

Volatile Metabolites Emission by In Vivo Microalgae—An Overlooked Opportunity?

“…The VOSCs have important implications in the arena of global sulfur cycle [ 54 ] and climate [ 55 ], since algae are estimated to produce approximately 50% of the biogenic sulfur that is emitted into the atmosphere annually [ 56 ]. Additionally, alkane thiols such as methanethiol and isopropylthiol are intensely malodorous compounds that are known to be emitted by cyanobacteria.…”

“…Additionally, alkane thiols such as methanethiol and isopropylthiol are intensely malodorous compounds that are known to be emitted by cyanobacteria. In fact, cyanobacterial mats are important sources of methanethiol and Microcystis aeruginosa (freshwater cyanobacteria) has been identified as a major emitter of isopropylthiol [ 55 ]. This microalga is a common toxic algal bloom-forming microorganism capable of causing considerable ecological and economic damage [ 57 ].…”

“…This is supported by DMSP lyase in Emiliania huxleyi and invoking the possibility of using enzyme activity levels for the quantification of biogeochemical contributions of the microalgae and relating them to global DMS production [ 62 ]. Other sulfur compounds of potential climate impact include dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), isopropylthiol, diisopropyl disulfide, and diisopropyl trisulfide [ 55 ] ( Figure 4 ).…”

Online, real‐time, and direct use of SIFT‐MS to measure garlic breath deodorization: a review

“…The distinct characteristics of sulphur chemistry directly affect the production and metabolism of volatile organosulphur compounds . Sulphur has a tendency to self‐react and form potent and odorous organosulphur compounds.…”

“…They can be reversibly oxidized in water to form disulphides. Dialkylsulphides, on the other hand, are analogous to dialkyl ethers but can be oxidized to form sulphoxides and sulphones, which are organosulphur compounds with low volatility and mild odour . l ‐Cysteine sulphoxides and γ‐glutamyl‐ l ‐cysteine peptides are two classes of organosulphur compounds found in garlic bulbs.…”