Protective mechanism of the soil–plant system with respect to heavy metals

Purpose

The aim of this work was to select and assess the efficiency of different amendments applied to ordinary chernozems artificially contaminated with heavy metals (Zn and Pb).

Materials and methods

The effect of different amendments on ordinary chernozem contaminated with Zn and Pb acetate salts was studied in a long-term 3-year field experiment. Glauconite, chalk, manure, and their combinations were chosen as ameliorating agents. Spring barley (Hordeum sativum) was used as test culture for three successive years. The heavy metal concentration in all the soil samples decomposed by HF?+?HClO₄ was determined by atomic absorption spectrophotometry (AAS). One normal concentration of CH₃COONH₄ at pH 4.8 was used to estimate the actual mobility of metals. The compounds of heavy metals extracted by 1 N HCl are regarded as mobile compounds. The concentration of metals in the plants was determined using the dry combustion in a mixture of HNO₃ and HCl at 450 °C. The content of heavy metals in extracts from soil and plant samples was determined by AAS.

Results and discussion

The content of weakly bound metal compounds increased upon the contamination of the soil with Pb and Zn salts, which led to a low quality of barley grown in these soils. Metal concentrations in the barley grain exceeded the maximum permissible concentrations (MPCs). The content of Zn and Pb in grains was higher than the MPC for at least 3 years after the soil pollution. The application of amendments significantly decreased the mobility of metals, and the simultaneous application of chalk and manure was most significant. The share of weakly bound metal compounds in the contaminated soils decreased to the level typical for the clean soils or even below.

Conclusions

The combined application of chalk and manure to Zn- and Pb-contaminated ordinary chernozems decreased the content of weakly bound metal compounds in the soil and lowered their concentrations in barley plants. The polyfunctional properties of the soil components with respect to their capacity for metal fixation were established. The decrease in the intensity of Zn accumulation in grains of barley shows the presence of a barrier at the root–stalk and stalk–grain interfaces.

     

Analysis of oil composition in cultivars and wild species of oat (Avena sp.)

Oil quality and content were analyzed in 33 accessions from 13 wild species and 10 accessions of cultivated oat. Wild oat species tended to have higher oil and 18:1 fatty acid (FA) contents and lower amounts of 18:2 and 18:3 FAs as compared to cultivated oats. In addition to common FAs, minor amounts of several hydroxy and epoxy FAs were also present in the oat oil and mainly confined to specific lipid classes. These unusual FAs included the previously reported 15-hydroxy 18:2 (Delta9,12) (avenoleic acid) mostly found among polar lipids and a novel 7-hydroxyhexadecanoic acid located to 1,2-diacylglycerol. The present study highlights the potential of making use of the existing germplasm, consisting of wild oat species, in breeding programs for achieving new oat varieties that produce a range of oils with different FA compositions as well as having high oil contents. However, in one matter, oats apparently lack genetic diversity and that is for oil qualities that are highly enriched in the omega 3 (omega-3) FA 18:3. Consequently, developing oat cultivars with highly unsaturated oils will need involvement of other techniques such as biotechnology.     

Specificity of soil functioning and formation on gas-bearing areas

Background, aim, and scope  Exploited gas fields and underground gasholders are specific sources of increasing methane concentration. Methane migrates into the soils by diffusion and convection through natural and technogenic cracks in geological structures and influences the function of the soils. Soil cover of gas-bearing area functions as a specific, bilateral, periodically penetrating, geomembrane. Soils shield, transform, and differentiate migrating fluxes of technogenic-allochthonous methane, preventing its emission to the atmosphere. Problems of methane’s emission are rather current at the present, as methane is the second in importance after CO₂ greenhouse gas, since its concentration in the atmosphere annually grows by approximately 1%. By global estimations, methane emissions in the gas industry make about 8% of annual receipt to the atmosphere, equal on the average to 500 Тg per a year (Cicerone and Oremland, Global Biogeochem Cy 2:299–327, 1988). But these calculations are based on the account of the technological losses making 3–12% from the mining of natural gas. The contribution of migratory methane fluxes to the atmosphere, as a rule, is not considered. The need for research of soil cover functioning on gas-bearing areas is explained by the fact that processes of methane oxidation, its transformation in soils, and emission to the atmosphere at these objects are now practically not being studied. The aim of our study was to reveal specific processes of soil function and formation on gas-bearing areas by an example of underground gasholder. Materials and methods  The material was sampled in 1998–2003 at the territory of underground gasholder located in Albeluvisol’s zone in Russia. According to the comparative-geographical method, 51 soil profiles have been studied in similar litologically geomorphological conditions in various geochemical zones: in the industrial zone, in the zone of gas dissipation, and at the regional background. The total square of investigated territory is about 60 km². Six soil profiles were investigated in seasonal dynamics. Samples of soils for physical, chemical, and microbiological analyses were taken from each horizon of soil profiles (202 samples). Samples of soil air for a definition of methane concentration were taken from depths of 20, 40, and 60 cm. Methane emission to the atmosphere was measured near soil’s cuts and, in addition, on all area of the investigated territory at knots of squares network through 700–1,000 m, in total at 32–42 points in May, July, and November. Years of investigation have been split by technological and hydrothermal conditions. The periods with the normal and lowered compression of gas in gasholder, dry and warm, and damp and cool years have been allocated. It has influenced the soil function processes and considered an interpretation of the data received. Results  The changes of functional parameters of soils at a gas-bearing area influenced by methane fluxes migrating from gas deposits, in comparison with background soils, are revealed. Such functional parameters are methane concentration in the soils, activity of its bacterial oxidation, methane emission to the atmosphere, and oxidation–reduction potential. Spatial and temporary dynamics of these parameters at gas-bearing and background territory are investigated. Discussion  Methane interaction with soil’s air is in its ascending (descending) and lateral diffusion and convection in soils. Methane fluxes dissipate in porous space of soils forming gas anomalies. The technogenic-allochthonous methane concentration strongly varies in soil’s air on gas-bearing area (1–10,500 ppm) and, on average, exceeds the autochthonous, microbiologically produced methane at background territories. Migratory methane is deposited on diffusion and sorption barriers. The capacity of diffusion barrier depends on effective coefficient of diffusion, the attitude of air and general porosity, and granulometric composition and sharply differs in auto-, semi-hydro-, and hydromorphic soils reaching maximum in hydromorphicity and among the soils with identical water content—in heavy soils. The capacity of the sorption barrier is defined by abiotic methane absorption and a specific surface of soils and grows with their increasing intensity in soils to a heavier granulometric composition or into soils with peat and gleyic horizons. The low sorption capacity leads to an increase of methane concentration in the soil’s air and decreases its utilization by microorganisms, in which its quantity depends on sorption properties. The central component of functioning that promotes a number of essential transformations in soils on gas-bearing areas is methane interaction with the biotic phase. The periods of methane deposition by diffusion and sorption barriers are used for biological methane oxidation and formation of biogeochemical barriers in soils. The activity of bacterial methane oxidation is characterized by spatial variability and depends on the entrance of methane, defined by granulometric composition, soil moisture, the attitude of air and general porosity, Eh, organic matter content, and salinization. During interaction between technogenic-allochthonous methane and soil on diffusion, sorption, and biogeochemical barriers, its transformation occurs, accompanied by a strengthening of variability of oxidation–reduction potential and formation of pedogenic, bacteriomorphic, and nanodispersic magnetic oxides of iron. Conclusions and perspectives  Specificity of soil functioning on a gas-bearing area is in interaction of technogenic-allochtonous methane with solid, liquid, gaseous, and living substance of the soil system. Spatial laws of soils functioning on gas-bearing area in the Albeluvisol’s zone are revealed. Distinctions of soil functions depending on litologically geomorphological conditions are shown. The greatest changes of parameters of functioning under the influence of technogenic-allochthonous methane occur in automorphic soils, and it is less in semi-hydromorphic soils. Activity of bacterial methane oxidation in soils, emission, and consumption from the atmosphere and their spatial laws are characterized by the time dynamics depending on hydrothermal and technological conditions of seasons and years. During oxidation in soils of gas-bearing areas, carbon of methane is concentrated on a biogeochemical barrier that is shown in the increase of methylotrophic microorganisms’ biomass and leads to a high variability and decrease of Eh and to the formation of magnetic oxides of iron. Recommendations  Results of research can be used for carrying out ecological monitoring and an estimation of tightness of objects of the gas industry. Activity of bacterial methane oxidation, Eh, and magnetic oxides of iron can be used as diagnostic parameters of soils on gas-bearing areas. This paper has been developed from a presentation at the conference SUITMA-4 (Soils in Urban, Industrial, Traffic, Mining and Military Areas) Nanjing, China, 2007     

Comparing two methods of sequential fractionation in the study of copper compounds in Haplic chernozem under model experimental conditions

Purpose

It is very important to obtain the information on the soils capacity to immobilize HMs and distribute them among soil components. The aim of this work was to study the fractional composition of Cu compounds in Haplic chernozem under model contamination conditions using different fractionation methods.

Materials and methods

The fractional composition of copper compounds in Haplic Chernozem artificially contaminated with copper acetate has been studied under model experimental conditions. General regularities and differences in the distribution of Cu forms in soils at the use of sequential fractionation by the Miller method modified by Berti and Jacobs (1996) and the Tessier method (Tessier et al. 1979) are revealed.

Results and discussion

The differences are related to the metal affinity for specific carrier phases, as well as to the selectivity and extraction capacity of the reagents used in these methods. A significant increase in the most mobile exchangeable Cu fraction is observed in contaminated soils. Aluminosilicates and soil organic matter make the largest contribution to the adsorption and retention of Cu.

Conclusions

The Tessier method is more suitable for the separation of the total technogenic component from contaminated soils. The Miller method is more informative at the determination of loosely bound HM compounds because of the use of weaker extractants.

     

Antiparasitic Effects of Sulfated Polysaccharides from Marine Hydrobionts

This review presents materials characterizing sulfated polysaccharides (SPS) of marine hydrobionts (algae and invertebrates) as potential means for the prevention and treatment of protozoa and helminthiasis. The authors have summarized the literature on the pathogenetic targets of protozoa on the host cells and on the antiparasitic potential of polysaccharides from red, brown and green algae as well as certain marine invertebrates. Information about the mechanisms of action of these unique compounds in diseases caused by protozoa has also been summarized. SPS is distinguished by high antiparasitic activity, good solubility and an almost complete absence of toxicity. In the long term, this allows for the consideration of these compounds as effective and attractive candidates on which to base drugs, biologically active food additives and functional food products with antiparasitic activity.     

Influence of intermediate deformation rates in softwoods characterized with fracture resistance R-curves

Fracture resistance curves of Norway spruce were evaluated over a range of crosshead speeds between 0.05 and 200 mm/min using compact tension specimens. The fracture resistance curves were determined via J-integral K _R versus Δa (crack extension) using hybrid experimental–finite element method with stepwise quasi-static and transient dynamic analysis. Coupling experiments and high-speed camera with a rate of 0.5–135 frames/s capture enabled determination of crack kinetics and velocities. Digital image correlation method was employed to evaluate strain distribution maps of the fracture process zone. Deformation measurements suggested strong strain localization and significant influence of the loading rate. The most distinct strain map was evaluated for the loading rate of 200 mm/min, suggesting inertial effects. Rising fracture resistance develops for smaller crack lengths (0.15–0.20 a/w) for all loading rates, with an increase of up to 20–50% compared to initiation values. Fracture resistance R-curves were evaluated for single individual specimens as well as for averaged load–deformation responses, which hide strong localisations in single responses. Influence of deformation rate on the shape and magnitude of fracture resistance curves is significant. Inertial effects in transient dynamic response give rise to twofold higher fracture resistance of softwoods compared to quasi-static resistance.     

History,current status and prospects of sturgeon aquaculture in Russia

Since natural sturgeon populations have drastically declined, aquaculture of these valuable fish is important to meet the ever‐increasing demand for meat and caviar, thereby reducing the pressure on natural sturgeon resources. There are two directions in sturgeon aquaculture: controlled propagation for release and commercial farming. The controlled propagation supports the conservation of natural fish populations, while the commercial cultivation of sturgeons supplies the needs of the consumer market with the delicacy production of caviar (mainly). This review deals with the current status of the controlled propagation and stocking in the Volga‐Caspian basin and the commercial farming of sturgeons in Russia. The article also investigates the management of farmed broodstocks of sturgeons, which are used for obtaining seedlings and caviar. It is for sure that the active and continuous development of the two directions of sturgeon aquaculture will allow preserving these unique ancient fish on our planet until natural populations can be re‐established by self‐sustaining populations.     

A Collagen Basketweave from the Giant Squid Mantle as a Robust Scaffold for Tissue Engineering

The growing applications of tissue engineering technologies warrant the search and development of biocompatible materials with an appropriate strength and elastic moduli. Here, we have extensively studied a collagenous membrane (GSCM) separated from the mantle of the Giant squid Dosidicus Gigas in order to test its potential applicability in regenerative medicine. To establish the composition and structure of the studied material, we analyzed the GSCM by a variety of techniques, including amino acid analysis, SDS-PAGE, and FTIR. It has been shown that collagen is a main component of the GSCM. The morphology study by different microscopic techniques from nano- to microscale revealed a peculiar packing of collagen fibers forming laminae oriented at 60–90 degrees in respect to each other, which, in turn, formed layers with the thickness of several microns (a basketweave motif). The macro- and micromechanical studies showed high values of the Young’s modulus and tensile strength. No significant cytotoxicity of the studied material was found by the cytotoxicity assay. Thus, the GSCM consists of a reinforced collagen network, has high mechanical characteristics, and is non-toxic, which makes it a good candidate for the creation of a scaffold material for tissue engineering.