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Topic Review
Sulfate-Reducing Microorganisms
Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate (SO42–) as terminal electron acceptor, reducing it to hydrogen sulfide (H2S). Therefore, these sulfidogenic microorganisms "breathe" sulfate rather than molecular oxygen (O2), which is the terminal electron acceptor reduced to water (H2O) in aerobic respiration. Most sulfate-reducing microorganisms can also reduce some other oxidized inorganic sulfur compounds, such as sulfite (SO32–), dithionite (S2O42–), thiosulfate (S2O32–), trithionate (S3O62–), tetrathionate (S4O62−), elemental sulfur (S8), and polysulfides (Sn2−). Depending on the context, "sulfate-reducing microorganisms" can be used in a broader sense (including all species that can reduce any of these sulfur compounds) or in a narrower sense (including only species that reduce sulfate, and excluding strict thiosulfate and sulfur reducers, for example). Sulfate-reducing microorganisms can be traced back to 3.5 billion years ago and are considered to be among the oldest forms of microbes, having contributed to the sulfur cycle soon after life emerged on Earth. Many organisms reduce small amounts of sulfates in order to synthesize sulfur-containing cell components; this is known as assimilatory sulfate reduction. By contrast, the sulfate-reducing microorganisms considered here reduce sulfate in large amounts to obtain energy and expel the resulting sulfide as waste; this is known as dissimilatory sulfate reduction. They use sulfate as the terminal electron acceptor of their electron transport chain. Most of them are anaerobes; however, there are examples of sulfate-reducing microorganisms that are tolerant of oxygen, and some of them can even perform aerobic respiration. No growth is observed when oxygen is used as the electron acceptor. In addition, there are sulfate-reducing microorganisms that can also reduce other electron acceptors, such as fumarate, nitrate (NO3−), nitrite (NO2−), ferric iron [Fe(III)], and dimethyl sulfoxide. In terms of electron donor, this group contains both organotrophs and lithotrophs. The organotrophs oxidize organic compounds, such as carbohydrates, organic acids (e.g., formate, lactate, acetate, propionate, and butyrate), alcohols (methanol and ethanol), aliphatic hydrocarbons (including methane), and aromatic hydrocarbons (benzene, toluene, ethylbenzene, and xylene). The lithotrophs oxidize molecular hydrogen (H2), for which they compete with methanogens and acetogens in anaerobic conditions. Some sulfate-reducing microorganisms can directly utilize metallic iron [Fe(0)] as electron donor, oxidizing it to ferrous iron [Fe(II)].
  • 1.1K
  • 04 Nov 2022
Topic Review
Particle-Bound Mercury Characterization
Particulate Bound Hg (PBM) consists of all airborne particulate containing Hg, including both stable condensed and gaseous forms adsorbed on atmospheric particulate matter (PM); it is operationally sampled and quantified by pulling air through a glass fiber or a quartz filter. PBM usually includes all those particles with a diameter <2.5 μm, even if its characterization depends on the pore size of the filter used for its collection. The accurate dimensional characterization is then essential to estimate the dry deposition of PBM, as well as any other particulate pollutant; the particles diameters directly influence gravitational sedimentation and the PBM residence time in the atmosphere. In addition, PBM chemical speciation, as well as for the other Hg forms, is fundamental to understand PBM bioavailability and therefore the effects on human .
  • 1.1K
  • 05 Jul 2021
Topic Review
Remote Sensing Technique in Rice Weed Detection
Remote sensing technology aims to monitor and capture the earth’s information without making direct contact and destroying it. The utilization of the electromagnetic spectrum, ranging from visible to microwave for measuring the earth’s properties, is the main idea behind remote sensing technology. Machine learning (ML) and deep learning (DL) remote sensing techniques have successfully produced a high accuracy map for detecting weeds in crops using RS platforms. Therefore, this technology positively impacts weed management in many aspects, especially in terms of the economic perspective. The implementation of this technology into agricultural development could be extended further. 
  • 1.1K
  • 13 Dec 2021
Topic Review
Membrane Processes for Microplastic Removal
The world plastic production is constantly growing, with production rising from 335 million tons in 2016 to 348 million tons in 2017. The significant and continuous increase in the production of plastics causes an enormous amount of plastic waste on the land entering the aquatic environment. Furthermore, wastewater treatment plants (WWTPs) are reported as the main source of microplastic and nanoplastic in the effluents, since they are not properly designed for this purpose. Among the tertiary treatment processes, membrane operations can offer an effective solution to the microplastic and nanoplastic pollution in the effluents.
  • 1.1K
  • 24 Dec 2021
Topic Review
Taupo Volcano
Lake Taupo, in the centre of New Zealand’s North Island, is the caldera of a large rhyolitic supervolcano called the Taupo Volcano. This huge volcano has produced two of the world’s most violent eruptions in geologically recent times. The Taupo Volcano forms part of the Taupo Volcanic Zone, a region of volcanic activity that extends from Ruapehu in the South, through the Taupo and Rotorua districts, to White Island, in the Bay of Plenty region. Taupo began erupting about 300,000 years ago, but the main eruptions that still affect the surrounding landscape are the Oruanui eruption, about 26,500 years ago, which is responsible for the shape of the modern caldera, and the Hatepe eruption, dated 232 ± 5 CE. However, there have been many more eruptions, with major ones every thousand years or so (see timeline of last 10,000 years of eruptions). Considering recent history alone, the volcano has been inactive for an unusually long period of time, but considering its long-term activity, it was inactive for much longer between 8100 and 5100 BCE (3,000 year inactivity, compared to the current 1,800 years). Some volcanoes within the Taupo Volcanic Zone have erupted far more recently, however, notably a violent VEI-5 eruption of Mount Tarawera in 1886, and frequent activity of Whakaari/White Island, which erupted most recently in December 2019.
  • 1.1K
  • 18 Oct 2022
Topic Review
Nanobioremediation-Based Removal of Pollutants
Nanobioremediation is a cost-effective technique of utilizing plants and microbes for the breakdown of pollutant compounds, ultimately improving soil quality and reducing pollution. By breaking down contaminants in the soil, the process may be able to eradicate, retain, or reduce the amount of pollutants present.
  • 1.1K
  • 01 Mar 2022
Topic Review
Phytoremediation
Phytoremediation is defined as the use of plant species as a means of purifying polluted soil, water, and air. The term derives from the Greek word phyto (“plant”) and the Latin word remedium (“to correct or remove an evil”). Phytoremediation is a more economically feasible and efficient remediation option than other techniques, such as washing, flushing, or solidification.
  • 1.1K
  • 13 Feb 2023
Topic Review
Nomenclature for Hydrogeological Instability Risks
The nomenclature for hydrogeological instability risks includes four main risks, which are distinguished according to the risk causes : 1) hydrogeological risk, that is slowly caused by natural factors (e.g. collapse landslides in a calcareous cliff in uninhabited areas and erosion along a marly-calcareous slope) in environments where human activities are minimal, i.e. woods, forests and mountain pastures; 2) hydraulic-pedological farming risk, that implies the occurrence of landslides in every winter and is caused by incorrect crop selection, not suitable for the soil and climate parameters (e.g. on a hilly slope with a clay vertisol type with a landslide having different fronts, when the arable land is cultivated with a cereal-legume crop rotation), or the presence of springs with missing drainage in clay soils with a high gradient;3) hydraulic-infrastructural risk, that is caused by the building up of infrastructures not suitable for the surrounding environment, as they change the downflow of shallow water; 4) hydraulic-infrastructural-pedological-management risk, that is caused by crop operations not suitable for soil and crop parameters, where the selected cultivated plant species are suitable for the environment and field improvements change water downflow (e.g. in soils along hilly calcarenite slopes cultivated with olive orchards, where up-down soil tillage causes shallow water erosion).
  • 1.1K
  • 25 Jan 2022
Topic Review
Armenian Highlands
The Armenian Highlands (Armenian: Հայկական լեռնաշխարհ, romanized: Haykakan leṙnašxarh; also known as the Armenian Upland, Armenian plateau, or Armenian tableland) is the most central and the highest of the three plateaus that together form the northern sector of Western Asia. Clockwise starting from the west, the Armenian Highlands are bounded by the Anatolian plateau, the Caucasus, the Kura-Aras lowlands, the Iranian Plateau, and Mesopotamia. The highlands are divided into western and eastern regions, defined by the Ararat Valley where Mount Ararat is located. Western Armenia is nowadays referred to as eastern Anatolia, and Eastern Armenia as the Lesser Caucasus or Caucasus Minor, and historically as the Anti-Caucasus, meaning "opposite the Caucasus". During the Iron Age, the region was known by variations of the name Ararat (Urartu, Uruatri, Urashtu). Later, the Highlands were known as Armenia Major, a central region to the history of Armenians, and one of the four geopolitical regions associated with Armenians, the other three being Armenia Minor, Sophene, and Commagene. The population of the region has been primarily Armenian for most of its known history. Prior to the appearance of nominally Armenian people in historical records, historians have hypothesized that the region must have been home to various ethnic groups who became homogenous when the Armenian language came to prominence. The population of the Armenian Highlands seem to have had a high level of regional genetic continuity for over 6,000 years. Recent studies have shown that the Armenian people are indigenous to the Armenian Highlands and form a distinct genetic isolate in the region. The region was also inhabited during Antiquity by minorities such as Assyrians, Georgians, Greeks, Jews, and Iranians. During the Middle Ages, Arabs and particularly Turkmens and Kurds settled in large numbers in the Armenian Highlands. The Christian population of the western half of the region was exterminated during the Armenian genocide of 1915. Today, the eastern half is mainly inhabited by Armenians, Azerbaijanis and Georgians, while the western half is mainly inhabited by Kurds (including Yazidis), Turks, Azerbaijanis, Armenians (included crypto-Armenians and Hemshins) and Zazas. The region was administered for most of its known history by Armenian nobility and states, whether it was as part of a fully independent Armenian state, as vassals, or as part of a foreign state. Since the 1040s, the highlands have been under the rule of various Turkic peoples and the Safavid dynasty, with pockets of Armenian autonomy in places such as Artsakh. Much of Eastern Armenia, which had been ruled by the Safavids from the 16th century, became part of the Russian Empire in 1828 and was later incorporated into the Soviet Union, while much of Western Armenia was under the rule of the Ottoman Empire and later incorporated into Turkey. Today, the region is divided between Turkey, Georgia, Armenia, Azerbaijan and Iran.
  • 1.1K
  • 07 Nov 2022
Topic Review
Scientific Opinion on Climate Change
Scientific opinion on climate change is a judgment of scientists regarding the degree to which global warming is occurring, its likely causes, and its probable consequences. A related—but not identical—term, "scientific consensus on climate change," is the prevailing view on climate change within the scientific community. The consensus is that:
  • 1.1K
  • 29 Nov 2022
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