Formation Of Hydrosulfuric Layer Under Stratificaton Layer
Formation of hydrosulfuric layer under stratificaton layer
P.T. Savin, S.A. Dozenko
Odessa Branch Institute of Biology of Southern Seas, National Academy of Sciences of Ukraine
Regulated run-off of a river drain, deep eutrophication and pollution of coastal waters of a northwest part of the Black sea have resulted in sharp change of a hydrochemical mode of waters, deterioration of their quality and, as a consequence, to sharp deterioration of biotope aquatic life, down to biological accidents as large-scale kill.[1] In particular, in the Odessa region during supervision с1988 for 1999 the average long-term contents of oxygen in near-bottom a layer (Fig.1) has made 3,8 mg/l, the spatial security of concentration of oxygen in the field of critical meanings (2 mg/l and is lower) on all summer shootings (Fig.2) achieves 60% in the Odessa bay, and, actually, is not reduced below than 20% on all an extent of a coastal zone of researched area. Thus the decrease of oxygen below critical frequently is accompanied by formation hydrosulfuric at small depth at the chamfer of seabed directly under strutificaton layer. As have shown separate shootings the maximal deficiency of oxygen and presence hydrosulfuric sometimes it are found out not at seabed, as it is usual, and under a layer of jump.
In particular, the summer in a coastal zone on Ilichevsc beam at sharp stratification of waters (Fig.3) on depth 13-20 m finds out a powerful layer hydrosulfuric, which maximal concentration (400 mkg/l) is marked on depth of 13 m. For presentation on Fig.4 the schematic section through stations of this area including hydrosulfuric lens under a layer of jump is submitted. Hydrosulfuric the layer is well traced on the diagram of vertical distribution Eh (Fig.5), where the area negative is precisely allocated meanings with a minimum in a zone of 15 m horizons. As the layer of water under strutificaton layer, struck hydrosulfuric is visible from Fig.4, covers an extensive zone of researched water area. Thus, only in area sharp deepening (item 39) hydrosulfuric zone adjoined with bottom layer. Such processes the making lens with attributes hypoxia and anoxia, apparently, are not exclusive.
In particular, the similar situation was marked by us at the end of July in a coastal zone of the sea subject to influence of the Danube drain on depth of 8m. Here within the 3-rd day the process of formation hypoxia in bottom layer, introduction depleted of a layer of water under a layer of jump, detachment non-oxygen of a layer of water from the chamfer of seabed and migration it as a lens under strutificaton layer was traced. As the formation hydrosulfuric of zones is continuation of development hypoxia, in view of above-stated, the process of formation hydrosulfuric of lenses can be presented as follows. The ground adjourment enriched with organic substance, under favorable summer conditions provoke activity of oxidizing processes directly in near-bottom layer of water. At presence strutificaton layer it conducts to fast linkage of the rests of oxygen.
Near-bottom sea water deprived of oxygen is favorable environment for development sulphatereducing bacterium, injection which is direct from ground deposits starts process of oxidation of organic carbon on new ways. This process in kill zones is accompanied by allocation hydrosulfuric according to the circuit [1,2]:
2SO4-2 + 4C + 3H2O and H2S + HS - + CO2 + 3HCO
At some mixture of water weights. At the sufficient contents of organic substance in volume and appropriate hydrodynamical mode in a zone deepening of seabed, the layer of waters infected hydrosulfuric, is wrung out from near-bottom of layer and freely moves in water weight as a lens.
O2mg/l
month
Fig.1. An annual course of the contents of the dissolved oxygen in superficial (¾·¾) and near-bottom (¾▲¾) layer
Fig.2. Security (% of sizes of the contents of oxygen in near-bottom of layer 2mg/l on the data of summer shootings for all period of supervision
Fig.3. Vertical distribution of temperature of water in area of researches
Fig.
4. Hydrosulfuric lens in a conditional section on stations
Fig.5. Vertical distribution Eh in area of researches
References
1. U.P. Zaycev, G.P. Garkavaya, D.A. Nesterkova, L.N. Polishuk, A.G.Tsokur. State-of-the-art ecosystem northwestern part of Black See. // State-of-the-art ecosystem Black See. – M.: Nauka, 1987.-p. 216-230.
2. A.A.Zenin, N.V.Belousova. Hydrochemical dictionary.-L.:Hidrometeoizdat, 1988. –239p.
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