Chapter thirteen - Pollution of silver and silver nanoparticles in the ecosystems and their interactions with plants and soil microbiota

Abstract

Antibacterial properties of silver (Ag) have been known for a long time; however, only in the last decade, this element has attracted the attention of scientists. Despite the low clarkness of Ag in the soil, its technophilicity has been growing exponentially over the past half-century and, according to modern forecasts, will increase in the coming years. As a result of anthropogenic activity, silver is increasingly acting as a polluting element, which leads to the contamination of ecosystems and soils with various chemical compounds of silver (nanoparticles, oxides, sulfides, etc.). The dynamic development of nanotechnology contributes to an increase in the intake of Ag nanoparticles into the environment. Silver nanoparticles are the most widely used among other nanomaterials. They are widely used in cosmetic, hygienic, and medical products due to their potent antimicrobial properties and due to the fact that their larvicidal activity can be used to reduce insect populations. At the same time, their behavior in the surrounding environment is quite unpredictable. When silver nanoparticles enter waste streams, they accumulate in sewage sludge at treatment plants. Sewage sludge is used as fertilizers for agricultural soils. Silver nanoparticles are often used in agriculture as part of nanopesticides and antifungal agents. The use of nanoparticles in agriculture can increase short-term yields, but high levels of metals in soils can create the opposite effect. The absorption of silver and its nanoparticles by the soil may adversely affect the state of the soil biota, which necessitates a more detailed study and determination of the effects of influence on living organisms. According to the results of studies conducted earlier, in most cases, it was noted that contamination of soils with silver and their nanoparticles most often has a pronounced negative character, consisting in a violation of the biocenosis, the death of its inhabitants, and a decrease in their reproduction. In addition, silver and its nanoparticles can penetrate, move, and accumulate in plants. Since agricultural crops receive trace elements from irrigation water and soil, direct contact of silver nanoparticles with plant roots can lead to their absorption and transportation to shoots, stems, and leaves. As it is known, there are several ways for silver nanoparticles to enter the plant organs from the soil. The first way is diffusion into seeds, then into the root, and eventually migration into plant organs. The second way is to be absorbed by the roots of plants and then migrate to other organs. And the third way is based on direct migration to plant organs and localization in the cells of the epidermis or xylem. All these routes of entry from soil or water into plant cells depend on the size, concentration, and physicochemical characteristics of silver nanoparticles, as well as on the nature of crops and soil structure. However, there are still not enough studies to assess the effect of silver and its nanoparticles on plants, because most studies are conducted at the initial stage of plant development.