Features of the polycyclic aromatic hydrocarbon's spatial distribution in the soils of the Don River delta.

PAHs are one of the most toxic organic compounds classes which is obligatory controlled all over the world. There is a luck of studies devoted to the PAHs levels and sources identification in the south of Russia. The features of the PAHs accumulation and spatial distribution in hydromorphic soils (Fluvisol) were studied on the example of the soils of the Don River delta floodplain landscapes. It has been shown that changes in the PAHs content in soils depended on the type and intensity of the emission source. A factor analysis and multivariate linear regression analysis were carried out to determine the features of the spatial distribution for individual PAH compounds, considering the properties of soils and typical differences in the emission source. The most polluted areas in the studied area located along the transit line of the long-distance tankers, where the content of the most toxic high molecular PAHs compounds reached 8862 ng g-1. As a result of regression analysis, a relationship was established between the PAHs accumulation rate with the content of silt (particles less than 0.001 mm in size) and Ca2+ and Mg2+ exchangeable cations in the soil (at p-level < 0.0001). Differences in individual PAH content for medium and heavy loamy Fluvisol and depend on the influence of different types of pollution sources.

Bioaccessible PAH influence on distribution of antibiotic resistance genes and soil toxicity of different types of land use.

For a better understanding of the dissemination of antibiotic resistance genes (ARGs) in natural microbial communities, it is necessary to study the factors influencing it. There are not enough studies showing the connection of some pollutants with the dissemination of ARGs and especially few works on the effect of polycyclic aromatic compounds (PAHs) on the spread of resistance in microbiocenosis. In this respect, the aim of the study was to determine the effect of bioaccessible PAHs on soil resistome. The toxicity and the content of bioaccessible PAHs and ARGs were studied in 64 samples of soils of different types of land use in the Rostov Region of Russia. In most soils, a close positive correlation was demonstrated between different ARGs and bioaccessible PAHs with different content of rings in the structure. Six of the seven studied ARGs correlated with the content of 2-, 3-, 4-, 5- or 6-ring PAHs. The greatest number of close correlations was found between the content of PAHs and ARGs in the soils of protected areas, for agricultural purposes, and in soils of hospitals. The diverse composition of microbial communities in these soils might greatly facilitate this process. A close correlation between various toxic effects identified with a battery of whole-cell bacterial biosensors and bioaccessible PAHs of various compositions was established. This correlation showed possible mechanisms of PAHs' influence on microorganisms (DNA damage, oxidative stress, etc.), which led to a significant increase in horizontal gene transfer and spread of some ARGs in soil microbial communities. All this information, taken together, suggests that bioaccessible PAHs can enhance the spread of antibiotic resistance genes.

Pollution status and human health risk assessment of potentially toxic elements and polycyclic aromatic hydrocarbons in urban street dust of Tyumen city, Russia.

This study investigated levels and sources of pollution and potential health risks associated with potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in urban street dust collected from Tyumen city, a large transport centre with one of the highest motorization rates in Russia. Twenty street dust samples were collected from four grades of roads in five different land use areas. Research methods included measurements of physical and chemical properties of street dust, concentrations of 18 PTEs using inductively coupled plasma mass spectrometry, 12 PAHs using high-performance liquid chromatography, and statistical analysis of the data. Concentrations of Ni, Cr, Sb, and Mo, as well as medium and high molecular weight PAHs in urban street dust, were notably higher than in soils within the city, which indicates that transport is the main source of these elements. Concentrations of Cu, Cd, Pb, Zn, Mn, and As in street dust of Tyumen were lower compared to many large cities, while Cr, Ni, and Co were higher. Concentrations of PAH were comparable to other large nonindustrial cities. Total contamination of street dust by both PTEs and PAHs showed more robust relationships with the number of roadway lanes rather than land use. The estimated carcinogenic risks were low in 70% of samples and medium in 30% of samples. Noncarcinogenic risks were attributed to exposure to Co, Ni, V, and As. The total noncarcinogenic risk for adults was found to be negligible, while the risk was found to be moderate for children.

Sorption of benzo[a]pyrene by Chernozem and carbonaceous sorbents: comparison of kinetics and interaction mechanisms.

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon, highly persistent and toxic and a widespread environmental pollutant. Although various technologies have been developed to remove BaP from the environment, its sorption through solid matrixes has received increasing attention due to cost-effectiveness. The present research compares the adsorption capacity of Haplic Chernozem, granular activated carbon and biochar in relation to BaP from water solution. Laboratory experiments with different initial BaP concentrations in the liquid phase and different ratios of the solid and liquid phases show that Freundlich model describes well the adsorption isotherms of BaP by the soil and both sorbents. Moreover, the BaP isotherm sorption by the Haplic Chernozem is better illustrated by the Freundlich model than the Langmuir equation. The results reveal that the sorption capacity of the carbonaceous adsorbents at a ratio 1:20 (solid to liquid phases) is orders of magnitude higher (13 368 ng mL-1 of activated carbon and 3 578 ng mL-1 of biochar) compared to the soil (57.8 ng mL-1). At the ratio of 0.5:20, the adsorption capacity of the carbonaceous sorbents was 17-45 times higher than that of the soil. This is due to the higher pore volume and specific surface area of the carbonaceous sorbents than soil particles, assessed through scanning electron microscopy. The sorption kinetic of BaP by Chernozem was compared with the adsorption kinetics by the carbonaceous sorbents. Results indicate that the adsorption dynamic involves two steps. The first one is associated with a fast BaP adsorption on the large available surface and inside macro- and meso-pores of the sorbent particles of the granular activated carbon and biochar. Then, the adsorption is followed by a slower process of BaP penetration into the microporous space and/or redistribution into a hydrophobic fraction. The effectiveness of the sorption process depends on both the sorbent properties and the solvent competition. Overall, the granular activated carbon and biochar are highly effective adsorbents for BaP, whereas the Haplic Chernozem has a rather limited capacity to remove BaP from contaminated solutions.

Soil PAHs contamination effect on the cellular and subcellular organelle changes of Phragmites australis Cav.

The concentrations of ∑16 priority polycyclic aromatic hydrocarbons (PAHs) for soils, roots, and above-ground parts of reed (Phragmites australis Cav.) were determined on different monitoring plots located near the city of Kamensk-Shakhtinsky, southern Russia, where historically received industrial sewage and sludge. The total PAHs concentration in monitoring soil plots was significantly higher than those in the background site which situated at the distance of 2 km from the contamination source. Accordingly, the maximum accumulation was found for phenanthrene and chrysene among the 16 priority PAHs in most of the plant samples collected in the impact zone. The effects of PAHs' pollution on changes of Phragmites australis Cav. cellular and subcellular organelles in the studied monitoring sites were also determined using optical and electron microscopy, respectively. The obtained data showed that increasing of PAHs contamination negatively affected the ultrastructural changes of the studied plants. Phragmites australis Cav. showed a high level of adaptation to the effect of stressors by using tissue and cell levels. In general, the detected alterations under the PAHs effect were possibly connected to changes in biochemical and histochemical parameters as a response for reactive oxygen species and as a protective response against oxidative stress. The obtained results introduce innovative findings of cellular and subcellular changes in plants exposed to ∑16 priority PAHs as very persistent and toxic contaminants.

Effects of benzo[a]pyrene toxicity on morphology and ultrastructure of Hordeum sativum.

Many studies have been devoted to investigation of toxic benzo(a)pyrene (BaP) compound, but studies involving changes at the cellular level are insufficient to understand the mechanisms of polycyclic aromatic hydrocarbons (PAHs) effect on plants. To study the toxicity of BaP, a model vegetation experiment was conducted on cultivation of spring barley (Hordeum sativum distichum) on artificially polluted BaP soil at different concentrations. The article discusses the intake of BaP from the soil into the plant and its effect on the organismic and cellular levels of plant organization. The BaP content in the organs of spring barley was determined by the method of saponification. With an increase in the concentration of BaP in the soil, its content in plants also rises, which leads to inhibition of growth processes. The BaP content in the green part of Hordeum sativum increased from 0.3 µg kg-1 in control soil up to 2.6 µg kg-1 and 16.8 µg kg-1 under 20 and 400 ng/g BaP applying in soil, as well as in roots: 0.9 µg kg-1, 7.7 µg kg-1, 42.8 µg kg-1, respectively. Using light and electron microscopy, changes in the tissues and cells of plants were found and it was established that accumulation of BaP in plant tissues caused varying degrees of ultrastructural damage depending on the concentration of pollutant. BaP had the greatest effect on the root, significant changes were found in it both at histological and cytological levels, while changes in the leaves were observed only at the cytological level. The results provide significant information about the mechanism of action of BaP on agricultural plants.

Impact of humic acid on degradation of benzo(a)pyrene polluted Haplic Chernozem triggered by modified Fenton-like process.

In this study, the applicability of a modified Fenton reaction for remediation of polycyclic aromatic hydrocarbons (PAHs) was demonstrated in chernozem soil. The main aim was to investigate the impact of variation of humic acid (HA) on the modified Fenton capabilities to degrade of benzo(a)pyrene (BaP). Experimental was designed with two independent variables, including hydrogen peroxide (H2O2) and hematite (α-Fe2O3), to determine the most effective BaP treatment conditions with exploring natural and an extra added amount of HA. For modified Fenton reaction at Haplic Chernozem, the best BaP degradation conditions resulted in an overall degradation of 68% with the following conditions: 0.95 M H2O2; 17.54 mg/g hematite; pH 7.8 without adjustment; 24 h; unsaturated (soil: water ratio 1:0.5). In the soil supplemented with 1% HA, Fenton-like reaction was found to perform better and resulted in 76% BaP degradation with less amount of hematite dosage (16.71 mg). The fact that HA, a significant class of naturally occurring compounds in soil, supports the Fenton reaction has strong relevance in the field of enhancing PAHs degradation field to obtain a more economical route.

Levels, sources, and toxicity assessment of polycyclic aromatic hydrocarbons in urban topsoils of an intensively developing Western Siberian city.

This study investigates the levels, sources, spatial distribution, and toxicity of polycyclic aromatic hydrocarbons (PAHs) in urban soils of Tyumen, Russia. Observations of PAHs in cities of Western Siberia accomplished by a representative set of samples are very rare, even though it is one of the most urbanized parts of Russia. Therefore, it is important to estimate the status of PAHs in soils of urban environments representing vast Siberian regions. Tyumen, as one of the most intensively developing cities of Western Siberia, is a good object for such studies. Topsoil samples (0-10 cm) were collected from 241 sampling sites on a regular grid within Tyumen city limits. It was found that total concentration of 12 priority PAHs ranged from 33.4 to 2147.9 µg kg-1, with a median value of 280.3 µg kg-1. High-molecular-weight (HMW) PAHs were dominant, accounting for the majority (62%) of the total PAHs. Among the PAHs in soils, 4-ring compounds were predominant in all studied samples, followed by 5- and 6-ring PAHs. Phenanthrene, pyrene, fluoranthene, and benzo(ghi)perylene had values of 28%, 19%, 15%, and 10% of total PAHs, respectively. Results showed that large high-contrast anomalies of HMW PAHs were related to low-residential and transport areas. The diagnostic ratios, as well as hierarchical cluster analysis (HCA) and principal component analysis (PCA), confirmed that sources associated with the transport were the most significant, while biomass combustion played an important role as a source of PAHs in agricultural, low-residential, and recreational areas. Levels of individual PAHs, as well as total PAHs in urban soils of Tyumen, were comparable with those in non-industrial cities with similar populations but were significantly lower than those in large industrial centers. Assessment of soil toxicity using toxic equivalent quantity (TEQBaP) showed that the TEQBaP values varied from 2.0 to 388.2 µg kg-1, with a mean value of 34.9 µg kg-1 and median of 19.8 µg kg-1, and were lower than those in heavy industrialized cities, but higher than those in soils of cities specializing in consumer and service industries.

Environmental pollution of soil with PAHs in energy producing plants zone.

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed environmental toxicants primarily formed during the incomplete combustion of organic materials (for example, coal, oil, gasoline and wood). Power energy plants are the main sources of organic contaminants including PAHs. The purpose of the present research was to study the Novocherkassk Electric Power Station (NEPS) emission effects of PAHs accumulation in soils. The regional levels, types (groups) and spatial distribution of 16 priority PAHs were investigated. The monitoring sites were located on fallow lands of the 20 km around NEPS. PAHs extraction from collected soil samples was performed using the ecologically clean express-method of subcritical water extraction. The total PAHs content gradually increased in soil of the studied territories during 2016-2017 due to an increase in contaminants emission. Accordingly 16 priority PAHs were determined in the soil samples collected from the sites located to the northwest from NEPS in direction of predominant winds. The 5-km zone situated in direction of predominant winds was highly subjected to PAHs contamination, with maximal accumulation at a distance of 1.6 km from the source. The ratio of high- and low-molecular weight PAHs content in soils of monitoring sites was taken as an index of environmental soil contamination. The high-molecular weight PAHs concentration prevailed in monitoring sites soils situated in direction of predominant winds from NEPS, while the concentration of low-molecular weight PAHs prevailed in the monitoring sites soils situated around NEPS. Soil properties also influenced PAHs accumulation. Polyarenes content in Haplic Chernozems and Haplic Chernozems (Stagnic) was higher versus Fluvisols. This study provides the understanding and model the fate of PAHs in regional technogenic landscape.

Benzo[a]pyrene degradation and bioaccumulation in soil-plant system under artificial contamination.

The involvement of benzo[a]pyrene (BaP) one of the most toxic polycyclic aromatic hydrocarbons (PAHs) in the soil-plant system causes its potential carcinogenicity and mutagenicity for human health. The aim of this article is benzo[a]pyrene (BaP) degradation and bioaccumulation in soil-plant system under artificial contamination in model experiment with Haplic Chernozem and that spiked with various doses of BaP (20, 200, 400 and 800µgkg-1) equivalent to 1, 10, 20 and 40 levels of maximal permissible concentrations (MPC) planted with spring barley (Hordeum sativum distichum). The experimental soil samples were planted every spring and incubated outdoor during 4years. The express-method of subcritical water extraction was used for BaP extraction from samples. It was established the values of BaP period of semi-degradation in soil (T50, y) contaminated with 10, 20 and 40MPC deviated from 1.4 to 1.8years, while these values in low contaminated soils deviated from 2.9 to 5.4years. It was found the BaP concentrations in plants depended on initial BaP contamination and reduced simultaneously with diminish of BaP concentration in the related spiked samples. Growing of spring barley in the BaP spiked soils lead to BaP accumulation in plants. The bioaccumulation factors for BaP in roots and vegetative part of barley plants (BAFr and BAFv respectively) fluctuated within 0.035-0.065 and 0.015-0.025 respectively at the 1st season and then reduced about twice to the 4th season. Meantime those values in control soils vice-versa increased twice from 0.03 and 0.01 respectively.

The effect of technogenic emissions on the heavy metals accumulation by herbaceous plants.

The effect of technogenic emissions on the input of Pb, Zn, Cd, Cu, Mn, Cr, and Ni into plants from the Poaceae and Asteraceae families has been studied. Soil and plant contamination by anthropogenic emissions from industrial enterprises leads the decreasing of crop quality; therefore, the monitoring investigation of plants and soils acquires special importance. The herbaceous plants may be used as bioindicators for main environmental changes. It was found that the high level of anthropogenic load related to atmospheric emissions from the power plant favors the heavy metal (HM) accumulation in herbaceous plants. Contamination with Pb, Cd, Cr, and Ni was revealed in plants growing near the power plant. Heavy metals arrive to plants from the soil in the form of mobile compounds. Plant family is one of the main factors affecting the HM distribution in the above- and underground parts of plants. Plants from the Poaceae family accumulate less chemical elements in their aboveground parts than the Asteraceae plants. Ambrosia artemisiifolia and Artemisia austriaca are HM accumulators. For assessing the stability of plants under contamination with HMs, metal accumulation by plants from soil (the bioconcentration factor) and metal phytoavailability from plants above- and underground parts (the acropetal coefficient) were calculated. According to the bioconcentration factor and translocation factor values, Poaceae species are most resistant to technogenic contamination with HMs. The translocation factor highest values were found for Tanacetum vulgare; the lowest bioconcentration factor values were typical for Poa pratensis.