The influence of application of biochar and metal-tolerant bacteria in polluted soil on morpho-physiological and anatomical parameters of spring barley.

The paper presents the results of the model experiment on spring barley (Hordeum vulgare L.) grown in polluted soil. The influence of separate and combined application of wood biochar and heavy metal-tolerant bacteria on morpho-physiological, anatomical and ultrastructural parameters of H. vulgare L. has been studied. The joint application of biochar and bacteria increased the shoot length by 2.1-fold, root length by 1.7-fold, leaf length by 2.3-fold and dry weight by threefold compared to polluted variant, bringing the plant parameters to the control level. The maximal quantum yield of photosystem II decreased by 8.3% in H. vulgare L. grown in contaminated soil, whereas this decrease was less in biochar (7%), bacteria (6%) and in combined application of bacteria and biochar (5%). As for the transpiration rate, the H. vulgare L. grown in polluted soil has shown a decrease in transpiration rate by 26%. At the same time, the simultaneous application of biochar and bacteria has led to a significant improvement in the transpiration rate (14%). The H. vulgare L. also showed anatomical (integrity of epidermal, vascular bundles, parenchymal and chlorenchymal cells) and ultrastructural (chloroplasts, thylakoid system, plastoglobules, starch grains, mitochondria, peroxisomes, ribosomes, endoplasmic reticulum, vacuoles) changes, revealed by light-optical and transmission electron microscopy of leaf sections. The effects were most prominent in H. vulgare L., grown in polluted soil but gradually improved with application of biochar, bacteria and their combination. The use of biochar in combination with metal-tolerant bacteria is an efficient tool for remediation of soils, contaminated with heavy metals. The positive changes caused by the treatment can be consistently traced at all levels of plant organization.

Common and rare iron, sulfur, and zinc minerals in technogenically contaminated hydromorphic soil from Southern Russia.

Soils formed after the desiccation of Lake Atamanskoe, which has served as a reservoir for liquid industrial waste from the city of Kamensk-Shakhtinsky during a long time, were studied. These soils differ from zonal soils by a strong contamination with zinc and sulfur. Preliminary studies showed that Fe compounds fix a significant part of zinc. This requires to study S, Zn, and Fe minerals. In this work, Mössbauer spectroscopy was used for the identification of iron compounds and scanning electron microscopy was used for the microanalysis of these and other minerals. To facilitate the identification of Fe minerals, brown iron ocher was removed from a contaminated soil sample and analyzed. From electron microscopy and Mössbauer spectroscopy data, ocher contained hydrogoethite with a high content of sorption water and schwertmannite (a rare mineral, probably found in Russia for the first time). The chemical composition of this schwertmannite better corresponds to the Cashion-Murad model than to the Bigham model. Particles of partially oxidized magnetite and wustite enriched with zinc were revealed under electron microscope. Siderite with partial substitution of Fe2+ by Zn2+ was detected. Thus, contaminated hydromorphic soil contains both common minerals (illite, goethite, hematite, gypsum) and rare minerals (schwertmannite, Zn siderite, partially oxidized magnetite and wustite enriched with zinc).