The science of the total environment

The use of fossil fuels is now widely accepted as unsustainable due to depleting resources and the accumulation of greenhouse gases in the environment that have already exceeded the “dangerously high” threshold of 450 ppm CO2-e. To achieve environmental and economic sustainability, fuel production processes are required that are not only renewable, but also capable of sequestering atmospheric CO2. Currently, nearly all renewable energy sources (e.g. hydroelectric, solar, wind, tidal, geothermal) target the electricity market, while fuels make up a much larger share of the global energy demand (∼66%). Biofuels are therefore rapidly being developed. Second generation microalgal systems have the advantage that they can produce a wide range of feedstocks for the production of biodiesel, bioethanol, biomethane and biohydrogen. Biodiesel is currently produced from oil synthesized by conventional fuel crops that harvest the sun’s energy and store it as chemical energy. This presents a route for renewable and carbon-neutral fuel production. However, current supplies from oil crops and animal fats account for only approximately 0.3% of the current demand for transport fuels. Increasing biofuel production on arable land could have severe consequences for global food supply. In contrast, producing biodiesel from algae is widely regarded as one of the most efficient ways of generating biofuels and also appears to represent the only current renewable source of oil that could meet the global demand for transport fuels. The main advantages of second generation microalgal systems are that they: (1) Have a higher photon conversion efficiency (as evidenced by increased biomass yields per hectare): (2) Can be harvested batch-wise nearly all-year-round, providing a reliable and continuous supply of oil: (3) Can utilize salt and waste water streams, thereby greatly reducing freshwater use: (4) Can couple CO2-neutral fuel production with CO2 sequestration: (5) Produce non-toxic and highly biodegradable biofuels. Current limitations exist mainly in the harvesting process and in the supply of CO2 for high efficiency production. This review provides a brief overview of second generation biodiesel production systems using microalgae.

https://www.springer.com/cda/content/document/cda_downloaddocument/BioEnergyResearch_Second+Generation+Biofuels+High-Efficiency+Microalgae+for+Biodiesel+Production.pdf?SGWID=0-0-45-1347846-0

Second generation biofuels: high-efficiency microalgae for biodiesel production

/pdf/an-introduction-to-the-aquatic-insects-of-north-america-20i7stzjkw.pdf

An Introduction to the Aquatic Insects of North America

Biochar application to soils is being considered as a means to sequester carbon (C) while concurrently improving soil functions. The main focus of this report is providing a critical scientific review of the current state of knowledge regarding the effects of biochar application to soils on soil properties and functions. Wider issues, including atmospheric emissions and occupational health and safety associated to biochar production and handling, are put into context. The aim of this review is to provide a sound scientific basis for policy development, to identify gaps in current knowledge, and to recommend further research relating to biochar application to soils. See Table 1 for an overview of the key findings from this report. Biochar research is in its relative infancy and as such substantially more data are required before robust predictions can be made regarding the effects of biochar application to soils, across a range of soil, climatic and land management factors. Definition In this report, biochar is defined as: “charcoal (biomass that has been pyrolysed in a zero or low oxygen environment) for which, owing to its inherent properties, scientific consensus exists that application to soil at a specific site is expected to sustainably sequester carbon and concurrently improve soil functions (under current and future management), while avoiding shortand long-term detrimental effects to the wider environment as well as human and animal health." Biochar as a material is defined as: "charcoal for application to soils". It should be noted that the term 'biochar' is generally associated with other co-produced end products of pyrolysis such as 'syngas'. However, these are not usually applied to soil and as such are only discussed in brief in the report. Biochar properties Biochar is an organic material produced via the pyrolysis of C-based feedstocks (biomass) and is best described as a ‘soil conditioner’. Despite many different materials having been proposed as biomass feedstock for biochar (including wood, crop residues and manures), the suitability of each feedstock for such an application is dependent on a number of chemical, physical, environmental, as well as economic and logistical factors. Evidence suggests that components of the carbon in biochar are highly recalcitrant in soils, with reported residence times for wood biochar being in the range of 100s to 1,000s of years, i.e. approximately 101,000 times longer than residence times of most soil organic matter. Therefore, biochar addition to soil can provide a potential sink for C. It is important to note, however, that there is a paucity of data concerning biochar produced from feedstocks other than wood, but the information that is available is discussed in the report. Owing to the current interest in climate change mitigation, and the irreversibility of biochar application to soil, an effective evaluation of biochar stability in the environment and its effects on soil processes and functioning is paramount. The current state of knowledge concerning these factors is discussed throughout this report.

Biochar Application to Soils - A Critical Scientific Review of Effects on Soil Properties, Processes and Functions

Under appropriate in vivo or in vitro conditions, certain somatic plant cells have the capability to initiate embryogenic development (somatic embryogenesis). Somatic embryogenesis provides an unique experimental model to understand the molecular and cellular bases of developmental plasticity in plants. In the last few years, the application of modern experimental techniques, as well as the characterization of Arabidopsis embryogenesis mutants, have resulted in the accumulation of novel data about the acquisition of embryogenic capabilities by somatic plant cells. In this review, we summarize relevant experimental observations that can contribute to the description and definition of a transitional state of somatic cells induced to form totipotent, embryogenic cells. During this somatic-to-embryogenic transition, cells have to dedifferentiate, activate their cell division cycle and reorganize their physiology, metabolism and gene expression patterns. The roles of stress, endogenous growth regulators and chromatin remodelling in the coordinated reorganization of the cellular state are especially emphasized.

http://www.cas.miamioh.edu/~meicenrd/pdevlmnt/feheretal2003.pdf

Transition of somatic plant cells to an embryogenic state

Heavy metals have been widely recognized as highly toxic and dangerous Plants, algae and bacteria respond to heavy metal toxicity by inducing different enzymes, creating ion influx/efflux for ionic balance and synthesizing small peptides These peptides bind metal ions and reduce toxicity Metals come from the natural weathering processes of the earth's crust, industrial discharge, pest or disease control agents applied to plants, urban run-off, mining, soil erosion, sewage effluents, air pollution fallout and other sources Plants can be affected directly by air pollutants, as well as indirectly through the contamination of soil and water At the same time, plant is a member of the food chain and may create a risk for man and animals through contamination of food supplies In recent years a considerable progress has been made in the assay of trace elements in environmental plant samples For higher plants, the accumulation of metals, especially cadmium, was tested when plants grew on sewage sludge-amended soils or in soils of cadmium residues from phosphate fertilizers No reports were accessible to us on the direct effect of tested metals (Pb, Hg, Cr, As, Cd) on seed germination and root growth The paucity of literature initiated our present work Inmore » this study, an attempt has been made to investigate the acute toxicity of five metals (Cr[sup 6+], Cd[sup 2+], Hg[sup 2+], Pb[sup 2+], As[sup 5+]) which are widely spread in the environment and are widely recognized as highly toxic and dangerous As the testing subject, mustard seeds (Sinapis alba) were used and their germination and root growth were observed 12 refs, 1 tab« less

Effect of Pb, Cd, Hg, As, and Cr on germination and root growth of Sinapis alba seeds

In plants, the excess of several heavy metals mimics iron (Fe) deficiency-induced chlorosis, indicating a disturbance in Fe homeostasis. To examine the level at which heavy metals interfere with Fe deficiency responses, we carried out an in-depth characterization of Fe-related physiological, regulatory, and morphological responses in Arabidopsis (Arabidopsis thaliana) exposed to heavy metals. Enhanced zinc (Zn) uptake closely mimicked Fe deficiency by leading to low chlorophyll but high ferric-chelate reductase activity and coumarin release. These responses were not caused by Zn-inhibited Fe uptake via IRON-REGULATED TRANSPORTER (IRT1). Instead, Zn simulated the transcriptional response of typical Fe-regulated genes, indicating that Zn affects Fe homeostasis at the level of Fe sensing. Excess supplies of cobalt and nickel altered root traits in a different way from Fe deficiency, inducing only transient Fe deficiency responses, which were characterized by a lack of induction of the ethylene pathway. Cadmium showed a rather inconsistent influence on Fe deficiency responses at multiple levels. By contrast, manganese evoked weak Fe deficiency responses in wild-type plants but strongly exacerbated chlorosis in irt1 plants, indicating that manganese antagonized Fe mainly at the level of transport. These results show that the investigated heavy metals modulate Fe deficiency responses at different hierarchic and regulatory levels and that the interaction of metals with physiological and morphological Fe deficiency responses is uncoupled. Thus, this study not only emphasizes the importance of assessing heavy metal toxicities at multiple levels but also provides a new perspective on how Fe deficiency contributes to the toxic action of individual heavy metals.

/pdf/heavy-metals-induce-iron-deficiency-responses-at-different-cxujeim47w.pdf

Heavy Metals Induce Iron Deficiency Responses at Different Hierarchic and Regulatory Levels

The inhibitory effects of Cd, Cu, Zn, Pb, and Fe on root elongation, contents of photosynthetic pigments, and metal accumulation in the roots and shoots of Sinapis alba were assessed. On the basis of growth inhibition metals can be arranged in a order Cu > Cd > Fe = Zn > Pb. All the metals, except Fe, were accumulated in significantly higher amount in the roots than in the shoots. Cd, Zn, Cu and Pb reduced chlorophyll a, and especially chlorophyll b content, and Zn and Pb reduced the carotenoid content, but less than that of chlorophyll a+b. The plants contained the highest concentration of Cd, and the lowest concentration of Zn.

Phytotoxic effects of Cd, Zn, Pb, Cu and Fe on Sinapis alba L. seedlings and their accumulation in roots and shoots

The priority of this study was to investigate how selenium influences toxicity of Cd, Zn, Cu and Pb when the metals appear in the hydroponic solution in pairs. As a model subject mustard seedlings (Sinapis alba L.) were used. Except phytotoxicity of individual metals and Se-metal combinations determined through photosynthetic pigments content (chlorophyll a, b, total carotenoids) also metal accumulation in the roots and shoots was determined by the AAS method. Se in all metal combinations reduced the unfavourable effect of other metals tested for chlorophylls content, however, for carotenoids primarily the opposite effect occurred. For metal accumulation in the roots and shoots it was confirmed that Se stimulated only Cd (about 24%) and slightly Cu (about 9%) accumulation in the roots, while in the shoots there was inhibited accumulation of all metals tested. The strongest inhibition was observed in Pb accumulation (84.9%). This fact indicates that Se generates some barriers for metal transfer from the roots to the underground plant parts. In contrast, Cu, Zn, Pb and Cd increased Se accumulation in the roots in the range of 4 (in combination with Cu) to 68% (in combination with Cd) and in the shoots in the range of 11 (in combination with Pb and Zn) to 44% (in combination with Cd). In the shoots only Cu inhibited Se accumulation (about 67%).

/pdf/effect-of-se-metal-pair-combinations-cd-zn-cu-pb-on-2307xb6hli.pdf

Agáta Fargašová

Papers

Effect of Pb, Cd, Hg, As, and Cr on germination and root growth of Sinapis alba seeds

Heavy Metals Induce Iron Deficiency Responses at Different Hierarchic and Regulatory Levels

Phytotoxic effects of Cd, Zn, Pb, Cu and Fe on Sinapis alba L. seedlings and their accumulation in roots and shoots

Effect of Se-metal pair combinations (Cd, Zn, Cu, Pb) on photosynthetic pigments production and metal accumulation in Sinapis alba L. seedlings

Toxicity of metals on Daphnia magna and Tubifex tubifex.