Chemical speciation of inorganic pollutants in river - Estuary - Sea water systems

Monitoring studies and thermodynamic modeling were used to reveal the changes of inorganic chemical species of some water pollutants (nutrients and trace metals such as Fe, Mn, Zn, Cu, Cd and Pb) in the river - estuary - sea water system. The case studies were two rivers, Kamchiya and Ropotamo, representing part of the Bulgarian Black Sea water catchment area, and having different flow characteristics. There were no major differences in inorganic chemical species of the two river systems. NO3- and NO2- chemical species showed no changes along the river - estuary - sea water system. Concerning phosphates six different species were calculated and differences between the three parts of the systems were established. The HPO42- and H2PO4- species were found to be dominant in river waters. The H2PO4- species quickly decreased at the expense of HPO42- and Ca, Mg and Na phosphate complexes in estuary and seawater. Trace metals showed a great variety of chemical species. Fe(OH)2+ species prevailed in river waters, and Fe(OH)3 0 species - in sea waters. Me2+ and MeCO30 (Me = Cu, Pb) and PbHCO3+ were dominant in river waters, while Cu(CO3)22- and PbCl- species appear also in sea waters. Cd2+ species prevailed in river and estuary waters, and CdCln2-n (n = 1 - 3) species, in seawater. Free Zn2+ species predominated in all systems but downstream their percentage decreased at the expense of Zn phosphates, carbonates, sulfates and chlorides complexes. Only free Mn2+ species were dominant along the systems. © Springer Science+Business Media B.V. 2008

Chemical speciation in natural and brine sea waters

A combined approach consisting of monitoring and thermodynamic modeling was used in order to calculate the concentration of trace element species in water samples of a broad salinity range and to explain their chemical behaviour. The study was performed on water samples (fresh, marine, hyper-saline) taken from the area of Burgas Bay, Bulgaria. The ion association model based on Debye-Hückel theory using the sst2008.dat database and the ion interaction model based on Pitzer theory using a new pit2010.dat database were compared and combined for the purposes of this study. The new pit2010.dat database combines the sst2008.dat database and the pitzer.dat database of the PHREEQCI computer program as well as the thermodynamic data for the elements Fe, Mn, Cu, Zn, Cd and Pb and their Pitzer ion interaction parameters. The results showed that: (1) the predominant species in fresh waters were free ions of Mn2+ (73.6%), Zn2+ (58.0%) and Cd2+ ions (78.3%) as well as carbonate species CuCO3 0(81.8%), PbCO3 0(77.2%) and hydroxy species Fe(OH) 3 0 (55.2%) and Fe(OH) 2 + (35.6%); (2) an increase in chloride species MeCln 2-n(n = 1-4, Me = Mn, Zn, Cu, Pb and Cd) and of the hydroxy species Fe(OH)2 + for Fe was calculated for sea and hyper-saline water. © 2010 Springer Science+Business Media B.V

Chemical speciation of inorganic pollutants in river - Estuary - Sea water systems

Monitoring studies and thermodynamic modeling were used to reveal the changes of inorganic chemical species of some water pollutants (nutrients and trace metals such as Fe, Mn, Zn, Cu, Cd and Pb) in the river - estuary - sea water system. The case studies were two rivers, Kamchiya and Ropotamo, representing part of the Bulgarian Black Sea water catchment area, and having different flow characteristics. There were no major differences in inorganic chemical species of the two river systems. NO3- and NO2- chemical species showed no changes along the river - estuary - sea water system. Concerning phosphates six different species were calculated and differences between the three parts of the systems were established. The HPO42- and H2PO4- species were found to be dominant in river waters. The H2PO4- species quickly decreased at the expense of HPO42- and Ca, Mg and Na phosphate complexes in estuary and seawater. Trace metals showed a great variety of chemical species. Fe(OH)2+ species prevailed in river waters, and Fe(OH)3 0 species - in sea waters. Me2+ and MeCO30 (Me = Cu, Pb) and PbHCO3+ were dominant in river waters, while Cu(CO3)22- and PbCl- species appear also in sea waters. Cd2+ species prevailed in river and estuary waters, and CdCln2-n (n = 1 - 3) species, in seawater. Free Zn2+ species predominated in all systems but downstream their percentage decreased at the expense of Zn phosphates, carbonates, sulfates and chlorides complexes. Only free Mn2+ species were dominant along the systems. © Springer Science+Business Media B.V. 2008

Trace metals pollution of waters and soils in Kardjali region, Bulgaria

Trace metals pollution of surface waters and their nearby soils in the metallurgically polluted Kardjali region, Bulgaria, were studied. Thermodynamic modeling including the dissolved organic carbon (DOC) was carried out for evaluating the distribution of metal species in waters and soil solutions. Zn was found to be the most widespread pollutant in the water samples, followed by Cu, Mn, and Cd. Geoaccumulation indices of trace metals for the tested soils were calculated, indicating that regarding Al, Fe, Co, Ni, and Cu all soils are “uncontaminated”. The most significant soil pollutant was found to be Cd, with all soils being either “extremely contaminated” by this metal or close to the limit, followed by Pb and Zn. The dynamics of trace metal chemical species distribution in surface waters and in the water-soluble soil fractions, as a result of possible spontaneous precipitations, was calculated by applying different thermodynamic models. Regarding Mn, Co, Ni, and Cd in waters and aqueous soil extracts and Zn in aqueous soil extracts, their free ion species prevailed, being more labile and hence toxic for the ecosystem. In the case of Al, Fe, Cu, Cd, and Pb in the waters and aqueous soil extracts and of Zn in waters, stable organic complexes with bidentate bonds, Me(OH)4 − or Me(OH)0 2 prevailed. © 2018, Springer International Publishing AG, part of Springer Nature

Chemical speciation in fresh, saline and hyper-saline waters

A thermodynamic model is proposed, which combines the ion association and the ion interaction models using the extended database pit2010.dat for a more precise modeling of the chemical species of micro components in natural waters of varying ionic strength (fresh, saline and hyper-saline). Compared to the ion association model, the proposed combined model more adequately describes the complex character of the ionic interactions. The performance of the combined ion association/ion interaction model compared to that of the ion association model is illustrated in case studies of several Bulgarian natural water systems of different ionic strength and type of pollution. The results are interpreted in terms of the chemical behavior of the metals and of their chemical species in the water systems, which is defined by the redox potential, pH, cationic and anionic organic and inorganic composition of the water systems and by the ability of the metals to preferentially coordinate with some anions, as well as by the stability of the corresponding species. The affinity of the transition metals towards the ligands is explained by the "hardness-softness" factor and the crystal field stabilization energy (CFSE). © 2014 IUPAC & De Gruyter

Modelling of chemical species of Al, Mn, Zn, and Pb in river body waters of industrial areas of West Rhodope Mountain, Bulgaria

The assessment of the ecological status of natural surface water, in terms of dominant trace metals, within an area subject to various sources of pollution including a non-ferrous metal ore mining, such as the West Rhodope Mountain, Bulgaria, is significant. The present study estimates the ecological status of river body waters at industrial areas of the West Rhodope Mountain, Bulgaria, simultaneously evaluating the possibility of state forecasting, together with assessing the potential risks, through the study of scenarios focusing on (i) possible variations of physicochemical parameters such as pH, concentration levels of trace metals, sulphates, and dissolved organic carbon (DOC) of surface water and (ii) consideration of potential spontaneous precipitation reactions in the studied waters. The ecological status of river body waters was assessed through a combination of experimental field, laboratory, and computational techniques. Al, Mn, Zn, and Pb were found to be the dominant pollutants with a variety of chemical species and distribution. The most significant difference characterizing the chemical species distribution in light of total spontaneous crystallization in the systems was found for Pb, followed by Zn and Mn, with the differences being more significant at lower trace metal levels. The calculated species were discussed on the basis of HSAB (hard and soft acids and bases) principle. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG

Trace metals accumulation in the eco-system water – soil – vegetation (Agropyron cristatum) – common voles (Microtus arvalis) – parasites (Hymenolepis diminuta) in Radnevo region, Bulgaria

Background: Coal and coal processing industries provoke trace metal pollution, which has a negative effect on the water – soil – vegetation – small mammals eco-system, constituting part of the food chain and exerting a serious impact on human health. Objectives: Assessment of the environmental impact of Maritza iztok coal complex, situated east of Radnevo town, Bulgaria, by tracking the dynamics and accumulation of trace metals in the eco-system water – soil – vegetation – common voles – parasites. Methods: Samples from surface waters, their nearby uncultivated soils, meadow uncultivated vegetation (Agropyron cristatum) and field common voles (Microtus arvalis) were collected. In situ measurements and laboratory extraction procedures and analyses were performed. Accumulation and mobility indices were calculated. The distribution of dissolved Mn, Ni, Cu, Zn and Pb chemical species in water-soil extracts was calculated using a thermodynamic approach. Two thermodynamic models were applied – the classical ion-association model for calculating the inorganic trace metal species and the Stockholm Humic Model (SHM) accounting for the complexation reactions of trace metals with organic matter. Visual Minteq computer program, Version 3.1 was used. The relationship chemical species - bioaccumulation was discussed. Results: Pb and Mn, together with SO42− and PO43- were found to be the main pollutants of waters in the region. The soils studied exhibited low concentrations of trace metals, not exceeding the specified MACs. The content of Mn was the highest, followed by Zn, Pb, Cu and Ni. The highest phytoaccumulation coefficients in the studied uncultivated grass vegetation were calculated for Cu and Zn, being 1–2 orders of magnitude higher than those of Mn and Ni. The accumulation of trace metals was explained on the basis of ions mobility and chemical species distribution. In the case of the host-parasite system Microtus alvaris - Hymenolepis diminuta, Zn displays the highest accumulation coefficient, followed by those of Cu and Pb. The parasite showed a higher bioaccumulation compared to infected common voles, with the highest bioaccumulation found for Ni. Conclusions: The bioaccumulation of trace metals depends on their mobility, concentration and chemical forms in water-soil solutions. Metal-organic species stimulate the phytoaccumulation of trace metals while inorganic ones suppress it. The sequence of trace metals bioaccumulation in common voles is analogous to that of soil contamination. The parasite exhibited higher bioaccumulation levels compared to infected common voles. © 2021 Elsevier Gmb

Cell cultures in biocompatibility assessment of new materials for bone implants

The extended life expectancy and the increasing number of overweight people place bone diseases among the most serious health and social problems of our time. To meet this challenge there is a need for advanced new ma­terials for bone implants that maximally resemble the properties and behaviour of natural bones as well as ex­perimental designs to evaluate their biological activity. The aim of our study was to assess the cytocompatibili­ty of different classes of scaffolds for bone implants, including fine calcium phosphate powders, composite ma­terials, cements, and bacterial cellulose-based materials. Murine (bone marrow cells, cell cultures from bone ex­plants, BALB/c 3T3 and L929 fibroblasts) and human (Lep-3 and MRC-5 fibroblasts) cells were used as model sys­tems in our investigations. The effect of the materials on cell viability and proliferation was evaluated in direct (the cells were seeded on the material surface) and/or indirect (the cells were cultured in a medium where the ma­terials were incubated for various periods of time) experiments by the MTT test (the gold standard for cytotox­icity assessment), neutral red uptake cytotoxicity assay, double staining with acridine orange and propidium io­dide, SEM, Comet assay, Annexin V (FITC assay, alkaline phosphatase activity assay, alizarin red staining. The results obtained revealed that: the cell cultures used as model systems in our investigations have different advan­tages and disadvantages and provide complementary information on the biological activity of materials. Some of the examined scaffolds show promising biocompatibility and require additional studies on their osteoinductivi­ty and osteoconductivity