ИСТИНА

The use of fly ash (FA) or bottom ash (BA) to improve soil quality has received much attention. High water holding capacity (WHC), favorable pH and presence of a large number of nutrients make it possible to consider FA as an element of the substrate for land reclamation. Coal ash is regard to problematic solid waste, due to the content of potentially toxic trace elements (As, Be) and organic compounds (polychlorinated biphenyls, polycyclic aromatic hydrocarbons). In Russia, these two types of ash are often stored together. Despite the vast areas occupied by the ash dumps, in Russia there is few researches on the possibility of their application for land reclamation and determining the degree of impact on the environment and plants. We examined the germination of oat (Avena sativa L.) seeds in Petri dishes on two samples of BA and one sample of FA of three different CHPPs (Central Heating and Power Plants (1, 2, 3)). Four parallel replicates of seeds germination were performed on each ash sample. Calcined quartz sand and a paper filter were used as a control. The substrates were humidified with distilled water. The number of sprouted seeds was counted. At the end of germination, the lengths of coleoptile and the longest root were measured for each seedling. It was found that BA and FA have a completely different effect, despite the similarity of the macronutrient composition, the absence of significant amounts of toxic elements in the samples and the presence of large amounts of nutrients such as potassium and phosphorus. Data on the length of roots and coleoptiles showed that in the case of FA these parameters are 3.5 times lower than in the case of BF of CHPP 1, 2.5 times lower in the case of a sample of BA of CHPP 2 and 2 times lower than quartz sand. Apparently, inhibition occurs due to insufficient aeration in an overly densified substrate, consisting of the finest particles, in the case of FA. The smallest lengths of both the roots and coleoptiles were found in seedlings sprouted on the FA of CHPP 3. On the one hand, this may be due to the unfavorable water-air properties of the substrate as shown above. This ash consists of the smallest particles that form tightly adhering mass, when moistened a continuous, that is not porous enough for the roots to breathe in it. On the other hand, as shown by gross chemical analysis, this ash contains an increased amount of Na and Be, which is toxic for coleoptile growth, and can inhibit seed germination. In addition, the content of As and Cr in FA is quite high and they can also be toxic. Varying of lengths of seedlings roots and coleoptiles grown on other substrates may be due to a variety of factors, such as pH, particle size distribution of the substrate, and the content of nutrients in their combination. It should only be noted that these substrates do not contain toxic elements in quantities that exceed permissible parameters.