Nature 10/09/19 Wikipedia”the Smell of rotten eggs”: how the Black sea got its “signature scent”
Scientists studying the Black sea, agree that the ecological state of this reservoir can be defined as adverse. Biggest concern of researchers is a huge amount of hydrogen sulfide, is concentrated in the area located below the level of 150-200 m.
hydrogen Sulfide
for the First time on deposits of hydrogen sulfide in the Black sea spoke Russian geologist Nikolai Andrusov, organized in 1890 an expedition to explore this body of water. This chemical compound is a colorless flammable toxic gas with a characteristic odor of rotten eggs, produced by the rotting of proteins and the absence of oxygen.
According to the latest estimates of experts, the total amount of hydrogen sulphide dissolved in the black sea waters, more than 3 billion tons and accounts for 90% of their volume, this means that the entire biosphere of the sea is concentrated in only 10% of its surface layer.
This is not the limit, because, according to the estimates of oceanographer Anatoly Ryabinin, over the past decade repeatedly experienced periods of increasing levels of hydrogen sulfide up to a threatening level 75.
Killing all life hydrogen sulfide is not only in the Black sea, but here its volume is so great that, according to the Kerch oceanographer Vladislav Shlyakhova, 100-150 m deeper life almost completely absent.
According to the Director of Marine hydrophysical Institute of the RAS, Sergey Konovalov, in the deep layers of the Black sea slowly, but surely, there is increase in the level of hydrogen sulfide, which, gradually rising, approaching the surface of the water.
the Layers of the Black sea
This environmental situation due to the unusual structure of the Black sea — in a relatively small area, it has quite a lot of depth, divided into several layers, the water of which is almost not mixed.
Scanty surface layer of the waters (100 m depth), which is called cold boundary is saturated with oxygen and nutrients to the almost fresh water of river origin. The next 100 m is inherent in lowering the level of oxygen and increasing the concentration of the salt, and below 200 m there is a complete absence of oxygen and the presence of heavy salt water, entering the Black sea through the Bosporus and the recently discovered underwater river.
Stratification, or stratification of the Black sea in the density, temperature, and salinity poses an obstacle for vertical water exchange and rapid ingress of oxygen into the interior of the reservoir. Some scientists assure that surface water reaches the black sea bottom for hundreds of years, and therefore below the level of 200 m the sea is a lifeless reservoir of hydrogen sulphide, the greatest concentration of which occurs at a depth of 2 km and 9.6 mg/l of water.
Where does the oxygen?
Most oxygen gets into the surface layer of the Black sea from the air, and some fraction formed in the photic zone (the illuminated water column) during photosynthesis of plankton algae.
the Whole caught in the water the oxygen goes to ensure viability of the black sea life, including dolphins, a variety of planktonic crustaceans, fish, jellyfish, crabs that do not live deeper than 100 m.
Where is the hydrogen sulfide?
According to the geological theory is that accumulation of hydrogen sulfide in the Black sea contributes to a slight underwater volcanic activity, which fall into the water gases from tectonic fractures in the earth’s crust.
However, most scientists, including American Lee Camp, believe that the hydrogen sulfide in the Black sea is formed due to the activity of bacteria saprotrophs, which, belonging to a number of anaerobic organisms that inhabit the deep layers and the bottom of the reservoir.
Participating in the decomposition of dead organic matter, that is as catalysts of the process gnietion, they are formed from the sulphates contained in sea soil, a substance which, uniting with sea water converted into hydrogen sulfide.
human factors
a Significant contribution to the destruction of clean water of the Black sea make the people that their violent activities have a negative impact on the ecological state of the waters.
the dredging and construction of breakwaters, oil pipelines, mining, destroying the fragile ecosystem of this reservoir is suffering from a surplus discharge into its waters of pollutants.
Untreated domestic and industrial sewage, as well as the rushing in of the sea the flow of agricultural fertilizers, reduce water clarity and increase nutrient content in the environment.
the Muddy surface reduces throughput, and therefore, the surface layer of water feels insufficient intake necessary for photosynthesis solar energy. For this reason, in 2003 the Black sea completely lost a unique field of Zernov, consisting of accumulations of red algae Phyllophora grown on an area of 11 km2.
Belgian researchers from the University of liège see the cause of the deterioration of water quality and reducing the depth of oxygen penetration into the Black sea in the release of huge amounts of nitrogen compounds and phosphorus.
Saturated with fertilizer water environment promotes active growth of phytoplankton weed and spreading thickets of primitive filamentous algae, organic remains contain a huge number to settle to the bottom, where it is taken for generating the hydrogen sulfide bacteria.
Consequences
According to oceanographer Alexander Gorodnitsky, do not underestimate the threat from the waters of the Black sea. Even if humanity suddenly come to their senses and stop polluting the pond with waste in your life, be an unpleasant surprise might nature. The fact is that this area is in a seismically active region, and any powerful an earthquakeextended can cause an explosion of poisonous hydrogen sulfide and air emissions of concentrated sulfuric acid that would destroy life in the coastal region and will spill acid rain in other areas.
Solution
to prevent a negative scenario, the scientists put forward different solutions to problems.
Researchers from Kherson are encouraged to use the hydrogen sulfide as alternative fuel: for this, they propose to drop vertically into the sea 80-foot pipe and pumped the air out of it, to create the pressure differential causing the water to clog a fountain of gas required.
Other scientists suggest to reduce the concentration of hydrogen sulfide in the Black sea by means of artificial aeration, that is, to lower the pipe into the lower layers of the waters, and let it fresh water, the density of which is less than the sea.
Methane
in Addition to hydrogen sulfide, in the “interior” of the Black sea lies an explosive gas methane, which in 1927 provoked a surprising phenomenon — the burning water.
Break out due to fluctuations caused by the Crimean earthquake, the methane ignited by lightning and filled the air with a disgusting smell of rotten cabbage and eggs.
Ashkhen Avanesova
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