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45-411: The design of the dam was conducted by Malcolm Dunstan & Associates engineering and construction company. The construction of the dam started on October 25, 2007 and its first generator was operational on November 19, 2011. The roller-compacted concrete arch-gravity dam has a maximum height of 99.2 metres (325 ft) and length of 600 metres (2,000 ft). The upstream vertical face arch radius

90-513: A characteristic foul odor of rotten eggs . Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777. Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide . When it is inhaled or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this,

135-443: A dam or floodgate is a stub . You can help Misplaced Pages by expanding it . Roller-compacted concrete Roller-compacted concrete ( RCC ) or rolled concrete ( rollcrete ) is a special blend of concrete that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of fly ash for portland cement . The partial substitution of fly ash for Portland Cement

180-666: A downstream slope that resembles a concrete staircase. Once a layer is placed, it can immediately support the earth-moving equipment to place the next layer. After RCC is deposited on the lift surface, small dozers typically spread it in one-foot-thick (about 30 cm) layers. The first RCC dam built in the United States was the Willow Creek Dam on Willow Creek, a tributary in Oregon of the Columbia River . It

225-472: A few weeks. Long-term, low-level exposure may result in fatigue , loss of appetite, headaches , irritability, poor memory, and dizziness . Chronic exposure to low level H 2 S (around 2 ppm ) has been implicated in increased miscarriage and reproductive health issues among Russian and Finnish wood pulp workers, but the reports have not (as of 1995) been replicated. Short-term, high-level exposure can induce immediate collapse, with loss of breathing and

270-587: A further cost of US$ 2 million, which initially reduced the leakage by nearly 75%; over the years, seepage has since decreased to less than 10% of its initial flow. Concern over the dam's long-term safety has continued however, although only indirectly related to its RCC construction. Within a few years of construction, problems were noted with stratification of the reservoir water, caused by upstream pollution and anoxic decomposition, which produced hydrogen sulfide gas. Concerns were expressed that this could in turn give rise to sulfuric acid , and thus accelerate damage to

315-857: A high probability of death. If death does not occur, high exposure to hydrogen sulfide can lead to cortical pseudolaminar necrosis , degeneration of the basal ganglia and cerebral edema . Although respiratory paralysis may be immediate, it can also be delayed up to 72 hours. Inhalation of H 2 S resulted in about 7 workplace deaths per year in the U.S. (2011–2017 data), second only to carbon monoxide (17 deaths per year) for workplace chemical inhalation deaths. Treatment involves immediate inhalation of amyl nitrite , injections of sodium nitrite , or administration of 4-dimethylaminophenol in combination with inhalation of pure oxygen, administration of bronchodilators to overcome eventual bronchospasm , and in some cases hyperbaric oxygen therapy (HBOT). HBOT has clinical and anecdotal support. Hydrogen sulfide

360-472: A metallic conductor of electricity. When cooled below a critical temperature this high-pressure phase exhibits superconductivity . The critical temperature increases with pressure, ranging from 23 K at 100 GPa to 150 K at 200 GPa. If hydrogen sulfide is pressurized at higher temperatures, then cooled, the critical temperature reaches 203 K (−70 °C), the highest accepted superconducting critical temperature as of 2015. By substituting

405-400: A result of the action of sulfate-reducing bacteria . Hydrogen sulfide is produced by the human body in small quantities through bacterial breakdown in the intestinal tract of proteins containing sulfur; it therefore contributes to the characteristic odor of flatulence. It is also produced in the mouth ( halitosis ). A portion of global H 2 S emissions are due to human activity. By far

450-510: A small part of sulfur with phosphorus and using even higher pressures, it has been predicted that it may be possible to raise the critical temperature to above 0 °C (273 K) and achieve room-temperature superconductivity . Hydrogen sulfide decomposes without a presence of a catalyst under atmospheric pressure around 1200 °C into hydrogen and sulfur. Hydrogen sulfide reacts with metal ions to form metal sulfides, which are insoluble, often dark colored solids. Lead(II) acetate paper

495-464: A waste product. Water heaters can aid the conversion of sulfate in water to hydrogen sulfide gas. This is due to providing a warm environment sustainable for sulfur bacteria and maintaining the reaction which interacts between sulfate in the water and the water heater anode, which is usually made from magnesium metal. H 2 S in the body acts as a gaseous signaling molecule with implications for health and in diseases. Hydrogen sulfide

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540-485: Is stinkdamp . Hydrogen sulfide is a highly toxic and flammable gas ( flammable range : 4.3–46%). It can poison several systems in the body, although the nervous system is most affected. The toxicity of H 2 S is comparable with that of carbon monoxide . It binds with iron in the mitochondrial cytochrome enzymes , thus preventing cellular respiration . Its toxic properties were described in detail in 1843 by Justus von Liebig . Even before hydrogen sulfide

585-459: Is 525 metres (1,722 ft). The induced joints are spaced at 20 metres (66 ft) intervals, with inducers installed in every second layer after compaction. The downstream face slope varies form 0.5:1 (H:V) in the center and 0.7:1 (H:V) on the flanks. The RCC mix strength requirements were determined by a target direct tensile strength of 1.2 megapascals (170 psi). The composition of the high-paste RCC mix included: This article about

630-433: Is also known to increase the levels of glutathione, which acts to reduce or disrupt ROS levels in cells. The field of H 2 S biology has advanced from environmental toxicology to investigate the roles of endogenously produced H 2 S in physiological conditions and in various pathophysiological states. H 2 S has been implicated in cancer and Down syndrome and vascular disease. It inhibits Complex IV of

675-506: Is also produced by heating sulfur with solid organic compounds and by reducing sulfurated organic compounds with hydrogen. It can also be produced by mixing ammonium thiocyanate to concentrated sulphuric acid and adding water to it. Hydrogen sulfide can be generated in cells via enzymatic or non-enzymatic pathways. Three enzymes catalyze formation of H 2 S : cystathionine γ-lyase (CSE), cystathionine β-synthetase (CBS), and 3-mercaptopyruvate sulfurtransferase (3-MST). CBS and CSE are

720-408: Is an important aspect of RCC dam construction because the heat generated by fly ash hydration is significantly less than the heat generated by portland cement hydration. This in turn reduces the thermal loads on the concrete and reduces the potential for thermal cracking to occur. RCC is a mix of cement/fly ash, water, sand, aggregate and common additives, but contains much less water. The produced mix

765-570: Is drier and essentially has no slump . RCC is placed in a manner similar to road paving ; the material is delivered by dump trucks or conveyors , spread by small bulldozers or specially modified asphalt pavers , and then compacted by vibratory rollers . In dam construction, roller-compacted concrete began its initial development with the construction of the Alpe Gera Dam near Sondrio in North Italy between 1961 and 1964. Concrete

810-423: Is generally criticised among collectors. Hydrogen sulfide is most commonly obtained by its separation from sour gas , which is natural gas with a high content of H 2 S . It can also be produced by treating hydrogen with molten elemental sulfur at about 450 °C. Hydrocarbons can serve as a source of hydrogen in this process. The very favorable thermodynamics for the hydrogenation of sulfur implies that

855-420: Is harmless. Hence, low levels of hydrogen sulfide may be tolerated indefinitely. Exposure to lower concentrations can result in eye irritation, a sore throat and cough , nausea, shortness of breath, and fluid in the lungs . These effects are believed to be due to hydrogen sulfide combining with alkali present in moist surface tissues to form sodium sulfide , a caustic . These symptoms usually subside in

900-409: Is involved in vasodilation in animals, as well as in increasing seed germination and stress responses in plants. Hydrogen sulfide signaling is moderated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). H 2 S has been shown to interact with NO resulting in several different cellular effects, as well as the formation of another signal called nitrosothiol. Hydrogen sulfide

945-535: Is produced when the silver on the surface of the coin reacts with atmospheric hydrogen sulfide. Coins that have been subject to toning by hydrogen sulfide and other sulfur-containing compounds may have the toning add to the numismatic value of a coin based on aesthetics, as the toning may produce thin-film interference , resulting in the coin taking on an attractive coloration. Coins can also be intentionally treated with hydrogen sulfide to induce toning, though artificial toning can be distinguished from natural toning, and

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990-499: Is slightly denser than air. A mixture of H 2 S and air can be explosive. In general, hydrogen sulfide acts as a reducing agent , as indicated by its ability to reduce sulfur dioxide in the Claus process . Hydrogen sulfide burns in oxygen with a blue flame to form sulfur dioxide ( SO 2 ) and water : If an excess of oxygen is present, sulfur trioxide ( SO 3 ) is formed, which quickly hydrates to sulfuric acid : It

1035-459: Is slightly soluble in water and acts as a weak acid ( p K a  = 6.9 in 0.01–0.1 mol/litre solutions at 18 °C), giving the hydrosulfide ion HS . Hydrogen sulfide and its solutions are colorless. When exposed to air, it slowly oxidizes to form elemental sulfur, which is not soluble in water. The sulfide anion S is not formed in aqueous solution. At pressures above 90 GPa ( gigapascal ), hydrogen sulfide becomes

1080-529: Is typically removed by amine gas treating technologies. In such processes, the hydrogen sulfide is first converted to an ammonium salt, whereas the natural gas is unaffected. The bisulfide anion is subsequently regenerated by heating of the amine sulfide solution. Hydrogen sulfide generated in this process is typically converted to elemental sulfur using the Claus Process . The underground mine gas term for foul-smelling hydrogen sulfide-rich gas mixtures

1125-405: Is used to detect hydrogen sulfide because it readily converts to lead(II) sulfide , which is black. Treating metal sulfides with strong acid or electrolysis often liberates hydrogen sulfide. Hydrogen sulfide is also responsible for tarnishing on various metals including copper and silver ; the chemical responsible for black toning found on silver coins is silver sulfide ( Ag 2 S ), which

1170-645: The Bakken formation crude, possibly due to oil field practices, and presented challenges such as "health and environmental risks, corrosion of wellbore, added expense with regard to materials handling and pipeline equipment, and additional refinement requirements". Besides living near gas and oil drilling operations, ordinary citizens can be exposed to hydrogen sulfide by being near waste water treatment facilities, landfills and farms with manure storage. Exposure occurs through breathing contaminated air or drinking contaminated water. In municipal waste landfill sites ,

1215-488: The human body produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule . Hydrogen sulfide is often produced from the microbial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers; this process is commonly known as anaerobic digestion , which is done by sulfate-reducing microorganisms . It also occurs in volcanic gases , natural gas deposits, and sometimes in well-drawn water. Hydrogen sulfide

1260-514: The Kraft process), tanneries and sewerage . H 2 S arises from virtually anywhere where elemental sulfur comes in contact with organic material, especially at high temperatures. Depending on environmental conditions, it is responsible for deterioration of material through the action of some sulfur oxidizing microorganisms. It is called biogenic sulfide corrosion . In 2011 it was reported that increased concentrations of H 2 S were observed in

1305-540: The burial of organic material rapidly leads to the production of anaerobic digestion within the waste mass and, with the humid atmosphere and relatively high temperature that accompanies biodegradation , biogas is produced as soon as the air within the waste mass has been reduced. If there is a source of sulfate bearing material, such as plasterboard or natural gypsum (calcium sulfate dihydrate), under anaerobic conditions sulfate reducing bacteria converts this to hydrogen sulfide. These bacteria cannot survive in air but

1350-584: The concrete. The controversy itself, as well as its handling, continued for some years. In 2004 an aeration plant was installed to address the root cause in the reservoir, as had been suggested 18 years earlier. In the quarter century following the construction of the Willow Creek Dam, considerable research and experimentation yielded many improvements in concrete mix designs, dam designs and construction methods for roller-compacted concrete dams. By 2008, about 350 RCC dams existed worldwide. As of 2018,

1395-590: The corresponding metal sulfides. Oxidic ores are sometimes treated with hydrogen sulfide to give the corresponding metal sulfides which are more readily purified by flotation . Metal parts are sometimes passivated with hydrogen sulfide. Catalysts used in hydrodesulfurization are routinely activated with hydrogen sulfide. Hydrogen sulfide was a reagent in the qualitative inorganic analysis of metal ions. In these analyses, heavy metal (and nonmetal ) ions (e.g., Pb(II), Cu(II), Hg(II), As(III)) are precipitated from solution upon exposure to H 2 S . The components of

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1440-519: The cysteine catabolic pathway. Dietary amino acids, such as methionine and cysteine serve as the primary substrates for the transulfuration pathways and in the production of hydrogen sulfide. Hydrogen sulfide can also be derived from proteins such as ferredoxins and Rieske proteins . Sulfate-reducing (resp. sulfur-reducing ) bacteria generate usable energy under low-oxygen conditions by using sulfates (resp. elemental sulfur) to oxidize organic compounds or hydrogen; this produces hydrogen sulfide as

1485-462: The dehydrogenation (or cracking ) of hydrogen sulfide would require very high temperatures. A standard lab preparation is to treat ferrous sulfide with a strong acid in a Kipp generator : For use in qualitative inorganic analysis , thioacetamide is used to generate H 2 S : Many metal and nonmetal sulfides, e.g. aluminium sulfide , phosphorus pentasulfide , silicon disulfide liberate hydrogen sulfide upon exposure to water: This gas

1530-639: The highest dam of this type was the Gilgel Gibe III Dam in Ethiopia, at 250 m (820 ft), with the Pakistani Diamer-Bhasha Dam under construction at 272 m (892 ft). Hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula H 2 S . It is a colorless chalcogen-hydride gas , and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having

1575-409: The largest industrial source of H 2 S is petroleum refineries : The hydrodesulfurization process liberates sulfur from petroleum by the action of hydrogen. The resulting H 2 S is converted to elemental sulfur by partial combustion via the Claus process , which is a major source of elemental sulfur. Other anthropogenic sources of hydrogen sulfide include coke ovens, paper mills (using

1620-420: The main proponents of H 2 S biogenesis, which follows the trans-sulfuration pathway. These enzymes have been identified in a breadth of biological cells and tissues, and their activity is induced by a number of disease states. These enzymes are characterized by the transfer of a sulfur atom from methionine to serine to form a cysteine molecule. 3-MST also contributes to hydrogen sulfide production by way of

1665-579: The mitochondrial electron transport chain, which effectively reduces ATP generation and biochemical activity within cells. Hydrogen sulfide is mainly consumed as a precursor to elemental sulfur. This conversion, called the Claus process , involves partial oxidation to sulfur dioxide. The latter reacts with hydrogen sulfide to give elemental sulfur. The conversion is catalyzed by alumina. Many fundamental organosulfur compounds are produced using hydrogen sulfide. These include methanethiol , ethanethiol , and thioglycolic acid . Hydrosulfides can be used in

1710-474: The moist, warm, anaerobic conditions of buried waste that contains a high source of carbon – in inert landfills, paper and glue used in the fabrication of products such as plasterboard can provide a rich source of carbon – is an excellent environment for the formation of hydrogen sulfide. In industrial anaerobic digestion processes, such as waste water treatment or the digestion of organic waste from agriculture , hydrogen sulfide can be formed from

1755-480: The production of thiophenol . Upon combining with alkali metal bases, hydrogen sulfide converts to alkali hydrosulfides such as sodium hydrosulfide and sodium sulfide : Sodium sulfides are used in the paper making industry. Specifically, salts of SH break bonds between lignin and cellulose components of pulp in the Kraft process . As indicated above, many metal ions react with hydrogen sulfide to give

1800-435: The reduction of sulfate and the degradation of amino acids and proteins within organic compounds. Sulfates are relatively non-inhibitory to methane forming bacteria but can be reduced to H 2 S by sulfate reducing bacteria , of which there are several genera. A number of processes have been designed to remove hydrogen sulfide from drinking water . Hydrogen sulfide is commonly found in raw natural gas and biogas. It

1845-729: The resulting solid are then identified by their reactivity. Hydrogen sulfide is used to separate deuterium oxide, or heavy water , from normal water via the Girdler sulfide process . A suspended animation-like state has been induced in rodents with the use of hydrogen sulfide, resulting in hypothermia with a concomitant reduction in metabolic rate. Oxygen demand was also reduced, thereby protecting against hypoxia . In addition, hydrogen sulfide has been shown to reduce inflammation in various situations. Volcanoes and some hot springs (as well as cold springs ) emit some H 2 S . Hydrogen sulfide can be present naturally in well water, often as

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1890-638: The sense of smell, creating temporary anosmia , so victims may be unaware of its presence until it is too late. Safe handling procedures are provided by its safety data sheet (SDS) . Since hydrogen sulfide occurs naturally in the body, the environment, and the gut, enzymes exist to metabolize it. At some threshold level, believed to average around 300–350 ppm, the oxidative enzymes become overwhelmed. Many personal safety gas detectors, such as those used by utility, sewage and petrochemical workers, are set to alarm at as low as 5 to 10 ppm and to go into high alarm at 15 ppm. Metabolism causes oxidation to sulfate, which

1935-468: Was constructed by the US Army Corps of Engineers between November 1981 and February 1983. Construction proceeded well, within a fast schedule and under budget (estimated US$ 50 million, actual US$ 35 million). On initial filling though, it was found that the leakage between the compacted layers within the dam body was unusually high. This condition was treated by traditional remedial grouting at

1980-462: Was discovered, Italian physician Bernardino Ramazzini hypothesized in his 1713 book De Morbis Artificum Diatriba that occupational diseases of sewer-workers and blackening of coins in their clothes may be caused by an unknown invisible volatile acid (moreover, in late 18th century toxic gas emanation from Paris sewers became a problem for the citizens and authorities). Although very pungent at first (it smells like rotten eggs ), it quickly deadens

2025-840: Was laid in a similar form and method but not rolled. RCC had been touted in engineering journals during the 1970s as a revolutionary material suitable for, among other things, dam construction. Initially and generally, RCC was used for backfill, sub-base and concrete pavement construction, but increasingly it has been used to build concrete gravity dams because the low cement content and use of fly ash cause less heat to be generated while curing than do conventional mass concrete placements. Roller-compacted concrete has many time and cost benefits over conventional mass concrete dams; these include higher rates of concrete placement, lower material costs and lower costs associated with post-cooling and formwork . For dam applications, RCC sections are built lift-by-lift in successive horizontal layers resulting in

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