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Neurochemical Pollutants in Aquatic Ecosystems: Modes of Interaction with Microalgae
Our previous publication in “Life on the Earth” [7] was concerned with neuroactive substances in the capacity of new-generation pollutants exemplified by neurotransmitters such as acetylcholine and biogenic amines. At low concentrations, these substances exert a growth-promoting effect on microalgae. The present work deals with the mode of action of extremely low concentrations (“trace amounts”) of neurotransmitters that comprises their antioxidant effects and the influence on the dynamics and rhythms of microalgal cultures’ development, i.e. on the succession of their age-related stages. Such neurotransmitters that can enter natural ecosystems with the wastewater of food, drug, and cosmetic industry, can be grouped into (1) substances that increase the unsaturated fatty acid (UFA) content in microalgal membranes, elevate the photosynthetic pigment concentration in the cells, and prolong the “youth” of microalgal cultures; and (2) substances that decrease the UFA content, reduce the photosynthetic pigment concentration, and, accordingly, accelerate the “aging” of microalgal cultures.
SILICATIZATION OF CULTURAL LAYER SOILS IN ARCHAEOLOGICAL EXCAVATIONS
The preservation and in situ museumification of archaeological objects of stratigraphic sections of cultural layer soils, whose value depends on the integrity and intactness, is a complex and underdeveloped problem. This is due to some specific properties of these soils, such as the heterogeneity of soil composition both vertically and horizontally; the diversity of inclusions, the uneven compressibility of the strata, the ability to self-compact from their weight, changes in hydrogeological conditions, soil soaking and the decomposition of organic inclusions. As a result, these soils are the most unfavorable in artificial stabilization. In the study, a wide range of soils of the cultural layer from various places with stabilization plans were examined. Our analysis of the deposits made it possible to separate these soils by geochemical features which have the highest impact on the intensity of the chemical solution’s interaction processes with the mineral component of the soil.
This chemical solution is in a family of silicate compositions with surfactants of the amide class. These organic liquid glass hardeners activate the skeletal part of the soil and provide the complete mobilization of the main cementing substance (silica gel). Pilot tests of various modifications of organo-silicate solutions were carried out at the sites of Chersonesos (Sevastopol), Tanais (Rostov region), Moscow, etc. The soils ranged from sandy to loamy with various inclusions (building stone, ceramics, bones, fish scales, shells, ash, soot, plant roots, etc.). Soil stabilization was carried out by injecting chemical solutions of various densities with the use of vertical and horizontal injections. An important finding of the work was that forming a new soil mass with improved properties was determined by the composition, properties of the soil and injection solutions, the distance from the injector and the depth of the stabilized area.
For the first time in Russia, at the center of Moscow, it was possible to preserve the soil mass in situ of the cultural layer of the 16–17th centuries and exhibit it for 32 years to visitors in the underground archaeological museum.