Contamination of soils with heavy metals leads to reduction of soil fertility, destruction of natural ecosystems and detrimental effects on the health of society by increasing content of metals in the food chains from microorganisms to plants, animals and humans. Bioremediation is one of the most promising and cost-effective methods of cleaning soils polluted with toxic metals. According to current researchers, microorganisms and plants have the genetic potential to remove toxic metals from contaminated sites. The method of thermodynamic prediction was used to theoretically substantiate the mechanisms of interaction of soil microorganisms and plants with heavy metals. According to the our prediction, exometabolite chelators of anaerobic microorganisms may increase the mobility of metals and thereby contribute to the active transport of metals and their accumulation in plants. Plants of Nicotiana tabacum L. of Djubek cultivar were used as plant material for the current investigation. The examined toxicants were heavy metals, namely cobalt (II), nickel (II), chromium (VI), copper (II) and cadmium (II). The aqueous solutions of metal salts were added to the boxes after two months of plants growing to the final super-high concentration – 500 mg/kg of absolutely dry weight of soil. Quantitative assessments of copper and chromium-resistant microorganisms were made by cultivation on agar nutrient medium NA with a gradient of Cu(II) and Cr(VI). The concentration of metals in soil and plant material (leaves, stems and roots) was determined by atomic absorption method. The study revealed that heavy metals inhibited the growth of the examined tobacco plants. This was expressed by the necrosis of plant tissues and, ultimately, their complete death. Despite this, all investigated heavy metals were accumulated in plant tissues during 3–7 days before death of plants. The uptake of metals was observed in all parts of plants – leaves, stems and roots. The highest concentrations of Co(II), Ni(II), Cd(II), Cr(VI) were found in the leaves, Cu(II) – in the roots. The results show that the bioremoval efficiency of the investigated metals ranged 0.60–3.65%. Given the super-high initial concentration of each of the metals (500 mg/kg), the determined removal efficiency was also high. Cadmium was the most toxic to plants. Thus, the basic points of the thermodynamic prognosis of the possibility of accumulation of heavy metals by phytomicrobial consortium were experimentally confirmed on the example of N. tabacum plants and metal-resistant microorganisms. The study demonstrated that despite the high initial metals concentration, rate of damage and death of plants, metals are accumulated inplant tissues in extremely hight concentrations. Soil microorganisms were observed to have high adaptation potencial to Cu(II) and Cr(VI). In anaerobic conditions, microorganisms presumably mobilize heavy metals, which later are absorbed by plants. The obtained results are the basis for the development of environmental biotechnologies for cleaning contaminated soils from heavy metal compounds.
The results of long-term observations on the geochemical peculiarities of technogenic lead distribution in atmospheric aerosol of Zaporizhia, as well as in soils, bottom sediments, suspended matter from Dnipro river and substance from wet gas filters of open-hearth furnaces PJSC Zaporizhstal are presented. The actual material was obtained on the basis of comprehensive field monitoring during 2015-2019. Simultaneous involvement of data on hydrometeorological conditions (seasonality, precipitation, wind speeds, directions and duration) in the study area provided a integral approach to the processing and generalization of research results. A number of peculiarities of sedimentary substance distribution in air, interrelations of its anthropogenic and natural components are defined. Correlations were revealed between lead concentrations changes and aeolian mineral component distribution, seasonality, and a number of other factors. The highest concentration of lead was found in solid aerosol particles accumulated by the sedimentary trap at the monitoring site. It was revealed that the average concentration of investigated element in river suspension of Dnipro exceeds significantly background values, and for soils exceeds more than 3.5 times the permissible norms. At the same time, the fixed form of lead in atmospheric aerosol, in contrast to other environmental objects, loses its domination, giving the way to easily soluble forms, so the evidence of environmental hazard. Monitoring of seasonal patterns of the element distribution in the city air showed excess concentrations in the cold period of the year, which, according to the authors, is due to both meteorological conditions and redistribution of natural and anthropogenic factors that serve the driving force in processes of arriving and conversion of lead in atmosphere during different seasons of the year.
Рекомендовано членом редакційної колегії д-ром геол. наук О.І. Меньшовим) У роботі наведено нові результати вивчення газового складу повітря (ГСП) печер Поділля (Атлантида, Оптимістична, Млинки) та Буковини (Попелюшка) хроматографічним методом. Порівняння ГСП виконане на підставі проб повітря, відібраних у зимовий період. Підтверджені раніше відомі особливості ГСП печер. Зокрема показано, що повітря печер містить підвищену кількість СО 2 порівняно з атмосферним повітрям. Найвищі концентрації СО 2 зафіксовані в Попелюшці (4,10 об.%), а найнижчі-в Оптимістичній (0,12 об.%). Крім того, спостерігається збіднення киснем повітря віддалених від бортів гіпсового блоку частин Оптимістичної. У цій печері також виявлені гелій та водень у значних концентраціях, що дозволяє передбачати глибинні розломні порушення в межах печерного поля. Встановлено довготермінову стабільність ГСП печери Попелюшка та показано відсутність метану в її повітрі. Виявлені зміни ГСП печер, по'вязані з антропогенним навантаженням. Зокрема в печері Атлантида відмічається забруднення повітря вуглеводнями.
Semiconductor I-III-VI nanocrystals are highly luminescent low toxic materials with direct band gap and tunable emission in visible and near infrared region which can be synthesized in aqueous media via simple procedure making them competitive object in compare with well developed and investigated II-VI quantum dots. However the nature of radiative recombination pathways definition and effect of synthesis conditions on spectral characteristics of the nanocrystals investigation remains an important task. In the present work influence of the cation precursors ratio as well as the heat treatment duration on the composition, optical properties and photostability of AgInS2 and AgInS2/ZnS nanocrystals synthesized in aqueous media have been investigated. Due to the low reactivity of indium salts in aqueous solution coused by formation of a stable complexes with stabilizer or hydroxycomplexes the nearest stoichiometric Ag1,1InSx quantum dots are formed at the initial [In]:[Ag] ratio 7:1. Under high excess of Ag formation of Ag2S/AgInS2 core/shell quantum dots confirming by presence of large 12-15 nm nanocrystals and red shift of the photoluminescence maximum with increasing [In]:[Ag] ratio from 1 to 3 (shell thickness should increase proportionally) is possible. With a further increase of the [In]:[Ag] ratio the absorption edge and the photoluminescence maximum are green shifted indicating increase of the quantum dots band energy. That can be explained by lowering of the valence band ceiling energy and rising of the conduction band bottom energy due to decrease of density of states of Ag 4d orbitals and increase of density of states of In 5s and 5p orbitals involved in the AgInS2 band gap formation. Increase of Indium content leads to significant increase of the photoluminescence intensity of AgInS2 nanocrystals eliminating nonradiative defects such as Agi. It have been shown that the ZnS shell epitaxial grow occurs due to the cation exchange between Zn2+ and In3+ and takes place only at low concentration of Zinc precursor ([Zn]:[Ag] ≤ 4). With further enhancement of the ratio the solid solution of AgInS2-ZnS is forming. To achieve the highest possible photoluminescence intensity and energy the AgInS2-ZnS nanocrystals should be heated at 950C at least for 120 minutes. It have been shown that the nearly stoichiometric Ag1,1InSx nanocrystals posess the highest photostability under UV light irradiation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.