The production and emission of hydrogen sulfide and methane by anaerobic microoganisms in sewer systems is a well-documented problem. The effectiveness of nitrite in controlling sulfide and methane production was tested in a laboratory scale sewer reactor. Nitrite was continuously dosed in the reactor for 25 days at concentrations of 20-140 mg N/L. No sulfide and methane accumulation was observed in the reactor in the presence of nitrite. A significant reduction was observed in the sulfate reduction and methane production capabilities of the biofilm. Nitrite also stimulated biological sulfide oxidation within the biofilm. The nitrite uptake rate of the reactor increased over the nitrite dosing period and nitrous oxide production was observed within the biofilm. When nitrite addition was stopped, sulfate reduction and methane production gradually resumed, and reached pre-nitrite addition levels after 2.5 months. The slow recovery suggests that nitrite can be applied intermittently for sulfide and methane control, which represents a key advantage over similar chemicals such as nitrate and oxygen. The study demonstrates nitrite addition as a promising and effective strategy for the management of sulfide and methane in sewers. Further investigation and optimization are still required before application in the field. © 2008 Elsevier Ltd. All rights reserved.

A new amperometric microsensor for detection of dissolved H2S in aquatic environments was developed. The design of the microsensor is based on the same principle as the dark-type oxygen microsensor. The sensor is equipped with a glass-coated platinum working electrode and a platinum guard electrode positioned in an outer glass casing (tip diameter 20-100 μm). Both working electrode and guard electrode were polarized at a fixed value in the range from +85 to + 150 mV with respect to a counter electrode. The outer casing is sealed with a thin silicone membrane and filled with a buffered electrolyte solution containing ferricyanide (K3[Fe(CN)6]) as redox mediator. Hydrogen sulfide penetrates the silicone membrane and is oxidized by K3[Fe(CN)6], resulting in the formation of elemental sulfur and ferrocyanide (K4-[Fe(CN)6]). The latter is electrochemically reoxidized at the exposed end of the platinum working electrode, thereby creating a current that is directly proportional to the dissolved H2S concentration at the sensor tip. The sensor was characterized and calibrated in a flow-through cell combined with a coulometric sulfide generator. Difficult studies including the determination of H2S with high spatial and temporal resolution seem to be possible. © 1996 American Chemical Society.

Hydrogen sulfide (H2S) is a physiological gasotransmitter known to possess a regulatory role in several tissues, including bone. The exogenous administration by injection of solutions of H2S-releasing compounds (e.g., GYY4137) has been previously investigated as a novel therapeutic approach for the treatment of bone diseases. Here, GYY4137 was embedded into fibroin sponges, previously shown to be suitable as scaffolds for bone, thanks to their biocompatibility, scalable porous structure, and biodegradability rate. Fibroin porous scaffolds were produced by solvent casting and the particulate leaching method, and GYY4137 was successively incorporated by using dimethyl sulfoxide (DMSO) as vehicle. The process used to produce GYY4137-loaded scaffolds allowed the incorporation of different controlled amounts of GYY4137 into fibroin matrices. The loading process preserved the properties of the system components in the final products, as assessed by SEM, FT-IR, NMR, and different thermal analyses techniques. Release of H2S from GYY4137 incorporated into the scaffolds was monitored upon incubation in saline solution at physiological pH: H2S-release kinetic was found to be dependent on the amount of GYY4137. To ensure biocompatibility, mouse fibroblasts and human primary bone marrow stromal cells were seeded onto scaffolds, and short-term viability assays were performed. Results showed that the GYY4137-loaded scaffold did not induce cytotoxicity in any of the cell type tested. Our findings demonstrate that embedding an H2S-releasing donor in silk fibroin scaffold is a suitable strategy to achieve a long-lasting release of H2S that preserves cell viability and allows local delivery at sites of tissue injury.

Oxygen depletion events and anoxia are a key threat to shallow marine coastal seas worldwide. The mortalities they trigger, however, are difficult to document in full. We developed an underwater device to experimentally induce hypoxia and anoxia on the seafloor. The EAGU (Experimental Anoxia Generating Unit) combines a time-lapse camera and flashes with an array of sensors and a datalogger. The unit was successfully deployed in 24 m depth in the Northern Adriatic Sea for 3 to 5 d and yielded detailed information on the behavior and sequence of mortality of macrobenthic organisms - both epi- and infauna - under decreasing oxygen and increasing H2S concentrations. This unit, designed as a chamber with an instrument lid, also can be deployed in an open configuration to document low dissolved oxygen (DO) events. The equipment can provide data for a catalog of behavioral patterns, define indicator species, help reconstruct past mortalities, and better gauge the stability and status of benthic communities.