The role of oxidative stress in spring barley cross-adaptation to different heavy metals

The aim of this study is to investigate the possibilities and the mechanisms of spring barley (Hordeum vulgare L.) cross-adaptation to different heavy metals after hardening with ozone (O₃), drought and UV-B radiation. Dry shoot biomass, accumulation of superoxide (O₂˙^?) and malondialdehyde (MDA), and activities of enzymes superoxide dismutase (SOD), glutathione reductase (GR) and catalase (CAT) were measured after hardening and heavy metal treatments. Seedlings, exposed to ozone and drought prior to copper (Cu) treatment, showed significantly increased tolerance to this heavy metal. The most possible causes of cross-adaptation to this redox-active heavy metal, which triggered very strong oxidative stress in nonhardened barley seedlings, were increased CAT activity, mitigation of O₂˙^? accumulation and lipid peroxidation. Cross-adaptation to cadmium (Cd) was induced only by drought hardening. In this case, however, adaptation had lower effect on antioxidative enzymes, did not altered O₂˙^? accumulation and even slightly increased the intensity of lipid peroxidation. The study reveals that stimulation of CAT activity and mitigation of oxidative stress are the main reasons for plant adaptation to Cu; whereas cross-adaptation to Cd, heavy metal with much lower oxidative capacity, is determined by the mechanisms that are not related to oxidative stress directly.     

The implications of sample preparation on the particle size distribution of soil

Particle size distribution (PSD) is among basic parameters in soil and sediment characterization and provides essential information in sedimentological and environmental studies. The problem with the PSD determination is that for any given sample the result depends not only on the method used but also on the sample pre‐treatment, making them seldom comparable. In this study, the PSD of seven non‐treated and pre‐treated soil samples were determined by four granulometric methods (pipette, sedigraph, particle counter and laser diffraction analysis). Samples were subjected to pre‐treatments commonly used in sample preparation for the PSD determination, i.e., addition of dispersant (sodium metaphosphate) and removal of the organic matter (with hydrogen peroxide). The total organic carbon (TOC) analysis was used to estimate the content of organic matter before and after its removal. The effect of different pre‐treatments was evaluated based on the PSD variations and the changes in the specific surface area (SSA) of the samples. The results highlighted differences in the PSD curves of samples depending on the granulometric method and pre‐treatment applied. The most pronounced difference was the higher amount of clay fraction determined by settling techniques. The role of hydrogen peroxide in disruption of aggregates was evident in the increase in the SSA as well as the share of fine fraction determined by all four techniques, while sodium metaphosphate made no modifications of the SSA but acted in favour of prolonging settling of clay particles and increasing its content obtained by settling techniques.     

Competitive Effect of Copper,Zinc, Cadmium and Nickel on Ion Adsorption and Desorption by Soil Clays

This study evaluated the effect of competing copper, zinc, cadmium and nickel ions in 0.01 M Ca(NO₃)₂ on heavy metal sorption and desorption by soil clay fractions. Initial Cu addition levels varied from 99 mg kg^-1 to 900 mg kg^-1 and Zn, Cd and Ni levels were 94, 131 and 99 mg kg^-1, respectively. Sorption of Cu conformed to a Freundlich equation. The amounts of metals not displaced by successive 48 h desorption cycles with 0.01 M Ca(NO₃)₂ were considered ‘specifically adsorbed’. Total sorption of Zn and Cd generally decreased in the order: Vertisol > Gleyic Acrisol > Planosol clay. More than 70% of the copper was specifically sorbed. Specific sorption of Zn was depressed by competition with Cu in the three clays investigated. At surface coverages higher than 200 mg Cu per kg of soil clay, zinc sorption in the Planosol and Gleyic Acrisol clays took place at low affinity sites. The exchangeable component of sorbed cadmium accounted for >:60% of the sorption in the Vertisol clay, >70% in the Gleyic Acrisol clay and was almost 100% in the Planosol clay. Nickel was not retained by the Planosol and Gleyic Acrisol clays and was ionexchangeably adsorbed by the Vertisol clay. At the conditions studied, Ni and Cd remain a ready source of pollution hazard.     

An Analysis of Nearly One Billion Dollars of Aquaculture Grants Made by the US Federal Government from 1990 to 2015

The aquaculture industry relies on federal investments to stimulate aquaculture research and development (R&D). We conducted this study to track federal spending for aquaculture using a large database of 2957 US federal research grants awarded from 1990 to 2015. During that period, 1.04 billion US dollars (USD) were spent on aquaculture research, with 919 million USD from federal agencies and 123 million USD in matching funds. By comparison, over the same time frame, the US Department of Agriculture's R&D spending was 41 billion USD. Federal grant funding for aquaculture had a 37‐fold return on investment since 2000. Microalgae, oysters, salmon and trout, catfish, and shrimp received the most grant support, and the most common topics/disciplines were aquaculture production sciences, aquatic animal health and disease, genetics and breeding, and nutrition. Our findings can be used to identify research gaps and inform federal policy, grant making, and budget allocation.     

Structure and variation in the wild-plant pathosystem: <Emphasis Type="Italic">Lactuca serriola–Bremia lactucae</Emphasis>

Over the past decade, extensive research on the wild-plant pathosystem, Lactuca serriola (prickly lettuce)–Bremia lactucae (lettuce downy mildew), has been conducted in the Czech Republic. Studies focused on pathogen occurrence and distribution, host range, variation in symptom expression and disease severity, interactions of B. lactucae with another fungal species (Golovinomyces cichoracearum) on L. serriola, variation in resistance within natural populations of L. serriola, the structure and dynamics of virulence within populations of B. lactucae, sexual reproduction of B. lactucae, and a comparison of virulence structure and changes in B. lactucae populations occurring in wild (L. serriola) and crop (L. sativa) pathosystems. The incidence of B. lactucae on naturally growing L. serriola and other Asteraceae was recorded. Lactuca serriola was the most commonly occurring host species, followed by Sonchus oleraceus. Over the duration of these studies, the incidence of B. lactucae in L. serriola populations varied between 45–87%. Disease incidence and disease prevalence were partly related to the size, density and different habitats of L. serriola populations. In addition to B. lactucae infection, infection by the lettuce powdery mildew fungus (Golovinomyces cichoracearum) was quite common, including co-infection. Variation in resistance to B. lactucae was studied by using ten isolates (NL and BL races with known virulence patterns) at a metapopulation level, i.e. 250 L. serriola samples representing 16 populations from the Czech Republic (CZ). Our comparisons revealed broad variation in host resistance among host populations and also intrapopulation variability. In the CZ populations, 45 resistance phenotypes were recorded, the most frequent were race-specific reaction patterns. Structural and temporal changes in virulence variation of B. lactucae populations on L. serriola were studied during 1998–2005. Altogether, 313 isolates of B. lactucae originating from the Czech Republic were examined for the presence of 32 virulence factors (v-factors), and 93 different virulence phenotypes (v-phenotypes) were recorded. A study of v-factor frequency showed that common v-factors in B. lactucae populations match some of the race-specific resistance genes/factors (Dm genes or R-factors) originating from L. serriola. The highest frequency was recorded by v-factors v7, v11, v15–17, and v24–30. In contrast, v-factors (e.g. v1–4, 6, and 10) matching Dm genes originating from L. sativa were very rare. This demonstrates the close adaptation of B. lactucae virulence to the host (L. serriola) genetic background. Temporal changes in virulence frequencies over the period were recorded. In many v-factors (v11, v14, v16, and v25–28), fluctuations were observed, some (v14 and v17) shifting to higher frequencies, and others (v5/8 and v23) decreasing. The occurrence of mating types was studied (1997–1999) in a set of 59 B. lactucae isolates. Both compatibility types (B1 and B2) were recorded; however the majority of the isolates (96%) were type B2. A comparative study of B. lactucae virulence variation between the wild (L. serriola) and crop (L. sativa) pathosystems showed major differences. Migration and gene flow between both pathosystems and the potential danger of wild B. lactucae populations for cultivated lettuce are discussed. This paper summarizes comprehensive and unique research on an oomycete pathogen (B. lactucae) that is shared between a crop (lettuce, L. sativa) and its close wild relative (prickly lettuce, L. serriola). The data demonstrate clear evidence about race-specific interactions, variation and changes in virulence, and coevolutionary relationships in the wild pathosystem L. serriola–B. lactucae. Conclusions contribute to the broadening and better understanding of gene-for-gene systems in natural host–pathogen populations and their relationships to crop pathosystems.     

Natural Occurrence and Distribution of Fusarium Toxins in Contaminated Barley Cultivars

Grain samples of 15 naturally contaminated barley cultivars, collected after harvest in southeastern Poland, were analysed for occurrence of Fusarium trichothecenes and zearalenone (ZEA). Barley kernels were contaminated with the following toxic metabolites: deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), 15-acetyldeoxynivalenol (15-AcDON), nivalenol (NIV), HT-2 toxin (HT-2), T-2 toxin (T-2), diacetoxyscirpenol (DAS), T-2 tetraol and ZEA. Significant correlations between concentrations of individual toxins and the dominant Fusarium species were found. Moreover, significant differences in toxin concentrations between cultivars were detected. Distribution of these mycotoxins was studied in two fractions of kernels (diameter > 2.5 mm and < 2.5 mm). A two-factor analysis of variance revealed significant differences between the two fractions, and between the analysed cultivars. Most of the interactions between fractions and cultivars were also significant. The highest concentration of the analysed toxins was in the fraction of small kernels. Kernel fraction <2.5 mm, although accounting for only 12.8% of sample weight, contained high proportions of the total toxin content: 80% of DON, 94% of NIV, 85% of ZEA, 83% of T-2 tetraol, 80% of DAS, 68% of HT-2 toxin and 81% of T-2 toxin. The results indicate that the level of contamination with Fusarium trichothecenes and ZEA, can be reduced by rejection of small kernels.     

Ants and heavy metal pollution – A review

Ants due to their nesting habits are ideal for studying temporal fluctuations in trace metal accumulation, changes in morphological traits, as well as for assessing evolutionary processes and monitoring environmental impact of metals derived from human activities. Although metal pollution may affect basic ecological traits such as colony size and survival, ants can be considered relatively resistant to metal pollution at least partly due to relatively high metal regulation efficiency. At both polluted and unpolluted areas the body metal levels in ants vary considerably between species. This observation and other experimental data suggest differences in metal regulation physiology, however the physiological basis of these differences remains unknown. It was shown that metal pollution may suppress the immune defense systems, which in turn could theoretically lead to a higher risk of infections. Biodiversity studies are limited, however the evidence for a clear negative influence of metal pollution on ant species diversity and abundance was not yet provided. Since many aspects of ant ecotoxicology remain unclear, the questions for possible future research are suggested.     

The accuracy of land cover-based wetland assessments is influenced by landscape extent

Widespread degradation of wetlands has motivated the development of tools to evaluate wetland condition. The application of field-based tools over large regions can be prohibitively expensive; however, land cover data may provide a surrogate for intensive assessments, enabling rapid and cost-effective evaluation of wetlands throughout whole regions. Our goal was to determine if land cover data could be used to estimate the biotic integrity of wetlands in Alberta??s Beaverhills watershed. Biotic integrity was measured using both plant- and bird-based indices of biotic integrity (IBIs) in 45 wetlands. Land cover data were extracted from seven nested landscape extents (100?C3,000?m radii) and used to model IBI scores. Strong, significant predictions of IBI scores were achieved using land cover data from every spatial extent, even after factoring out the influence of location to address the spatial autocorrelation of land cover classes. Plant-based IBI scores were best predicted using data from 100?m buffers and bird-based IBI scores were best predicted using data extracted from 500?m buffers. Road cover or density and measures of the proportion of disturbed land were consistent predictors of IBI score, suggesting their universal importance to plant and bird communities. Simplified models using the proportion of undisturbed land were less accurate than more detailed models (reductions in r ² of 0.31?C0.32). Regardless of the level of detail in land cover classification, our results emphasize the need to optimize landscape extent for the taxonomic group of interest: an issue that is typically poorly articulated in studies reporting on the development of GIS-based assessment methods. Our results also highlight the need to calibrate models in test areas before scaling up, to ensure predictive accuracy.     

Remediation of a grey forest soil contaminated with heavy metals by means of leaching at acidic pH

Purpose

The purpose was to study the heavy-metal leaching from topsoil when acidolysis or combination of acidolysis/complexolysis was applied as an approach for in situ soil remediation. The question was how the acidolysis of ferric iron hydroxides from topsoil would effect on the heavy-metal leaching when soil pH was lowered with sulfuric acid in or without the presence of cut straw into the soil.

Materials and methods

Four zero-suction lysimeters were used in this study. The heavy-metal acidolysis was studied by the soil irrigation with diluted solutions of sulfuric acid or its in situ generation as a result of the bacterial oxidation of S° by Acidithiobacilus thiooxidans.The sulfur requirement was calculated having in mind the higher amount of acid soluble iron in the topsoil due to its contamination by AMD. The combination of acidolysis/complexolysis was studied by cut straw addition to S° at ratio 1:1 and 3:1, respectively. Regular sampling and analyses of the pregnant soil solutions was applied. The pollutant content, their distribution among the geochemical fractions, and the content of amorphous ferric iron hydroxides were determined before and after soil bioremediation.

Results and discussion

The reducible mobile fraction was the main fraction in which almost 50 % of each heavy metal was entrapped as a result of the soil pollution by AMD. The combination of acidolysis/complexolysis, realized by elemental sulfur and cut straw addition to horizon A of the AMD-affected soil at ratio of 1:1, allowed the concentration of lead, uranium, and arsenic after 9 months of remediation to be decreased near the relevant maximum admissible concentration (MAC), as their content in the exchangeable and specific adsorbed mobile fraction were drastically reduced. It determined the lower bioavailability of the pollutants at the end of the leaching stage.

Conclusions

A mixture of elemental sulfur and cut straw at a ratio of 1:1 was an efficient method for in situ bioremediation of AMD-affected soil. The heavy-metal leaching from easily leachable fractions was a result of the joint action of acidolysis/complexolysis, and as a result, the contaminant content in horizon A was significantly reduced.

     

ADSORPTION-DESORPTION CHARACTERISTICS OF HIGH LEVELS OF COPPER IN SOIL CLAY FRACTIONS

Copper adsorption and desorption under acid conditions by soil clay fractions separated from Vertisol, Planosol and Gleyic Acrisol has been studied in 0.01 M Ca(NO₃)₂. A Freundlich equation was appropriate to describe Cu adsorption. Within the range of 150 to 2600 mg of copper per kg of soil clay fraction the proportions of Cu not displaced during 5 successive 48-hour desorptions with 0.01 M Ca(NO₃)₂ decreased with increasing adsorption density and at the lower pHs. The proportions ranged from as high as 0.98 in th case of the Vertisol clay (pH 5.3) to as low as 0.12 (88% desorption) in the Planosol clay (pH 4.5). Measurement of separation factors (ga Cu/Ca) showed that the preference of the clay surface for Cu over Ca decreased in the order: Gleyic Acrisol > Planosol > Vertisol. A considerable amount of sorbed copper could be solubilized by decreasing pH values to 4 when in the Planosol clay 39% was desorbed and 45% was desorbed in the Gleyic Acrisol clay.