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Topic Review
Bauxite Tailings
Bauxite tailings, also known as bauxite residue, red mud, red sludge, or alumina refinery residues (ARR), is a highly alkaline waste product composed mainly of iron oxide that is generated in the industrial production of alumina (aluminium oxide, the principal raw material used in the manufacture of aluminium metal and also widely used in the manufacture of ceramics, abrasives and refractories). It is important to differentiate between the alkaline waste generated in the Bayer process and the tailings generated during the mining of bauxite. This article specifically covers the alkaline waste generated when operating the Bayer process. The scale of production makes the waste product an important one, and issues with its storage are reviewed and every opportunity is explored to find uses for it. Over 95% of the alumina produced globally is through the Bayer process; for every tonne of alumina produced, approximately 1 to 1.5 tonnes of bauxite tailings/residue are also produced. Annual production of alumina in 2018 was approximately 126 million tonnes resulting in the generation of over 160 million tonnes of bauxite tailings/residue.
  • 2.0K
  • 02 Nov 2022
Topic Review
NOAAS Murre II
NOAAS Murre II (R 663), previously NOAAS Murre II (FRV 63), was an American research vessel in commission in the National Oceanic and Atmospheric Administration (NOAA) fleet from 1970 to 1989. Prior to her NOAA career, she operated under the United States Department of the Interior′s Fish and Wildlife Service from 1949 to 1956 and under the United States Fish and Wildlife Service′s Bureau of Commercial Fisheries from 1956 to 1970 as Murre II. The ship originally operated as a self-propelled barge, first as BSP-1915 for the United States Army during World War II and then for the Fish and Wildlife Service before undergoing conversion into a research ship in 1963.
  • 265
  • 02 Nov 2022
Topic Review
Propagating Rifts
Propagating rifts are seafloor features associated with spreading centers at mid-ocean ridges and back-arc basins. They are more commonly observed on faster rate spreading centers (50 mm/year or more). These features are formed by the lengthening of one spreading segment at the expense of an offset neighboring spreading segment. Hence, these are remnant features produced by migration of the tip of a spreading center. In other words, as the tip of a spreading center migrates or grows, the plate itself grows at the expense of the shrinking plate, transferring lithosphere from the shrinking plate to the growing plate.
  • 491
  • 02 Nov 2022
Topic Review
Astrooceanography
Astrooceanography is the study of oceans outside planet Earth. Unlike other planetary sciences like astrobiology, astrochemistry and planetary geology, it only began after the discovery of underground oceans in Saturn's Titan and Jupiter's Ganymede. This field remains speculative until further missions reach the oceans beneath the rock or ice layer of the moons. There are many theories about oceans or even ocean worlds of celestial bodies in the Solar System, from oceans made of diamond in Neptune to a gigantic ocean of liquid hydrogen that may exist underneath Jupiter's surface. Early in their geologic histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, and a runaway greenhouse effect may have boiled away the global ocean of Venus. Compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites; notably, the ocean of the moon Europa is estimated to have over twice the water volume of Earth. The Solar System's giant planets are also thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of liquid water within a circumstellar habitable zone. Ocean planets are a hypothetical type of planet with a surface completely covered with liquid. Astrooceanography is closely related to Astrobiology, as oceans are expected to have higher chances to house simple forms of life.
  • 1.1K
  • 01 Nov 2022
Topic Review Video
New Drip Irrigation Technologies in Upper Egypt
Saving fresh water is a big challenge for the next generation due to enhanced living standards and population growth. In addition, the expansion of agricultural and industrial activities is causing unmatched demands for fresh water supplies across Egypt. The Nile River is Egypt’s main water resource, representing 69.4% of the total water resources, while rainwater, torrential water and groundwater, as well as recycled agricultural and sanitary drainage water and desalinated seawater, are estimated at about 30.6%. Smart drip irrigation systems are in great demand, especially in Upper Egypt. SDG’s of the circular economy and the WEF nexus lead to full implementation of drip irrigation systems, achieving ~6.6 BM3/year of direct saving from fresh water and/or doubling the cultivated area. In addition to PV tubes and other utilities, renewable energy, e.g, photovoltaic panels, will posses an important role in low-energy driven drip irrigation systems, reducing fossil-uses, CO2 emissions and devolving more sustainable processes that are less dependent on conventional energy sources.
  • 1.4K
  • 01 Nov 2022
Topic Review
Environmental Impact of Shipping
The environmental impact of shipping includes air pollution, water pollution, acoustic, and oil pollution. Ships are responsible for more than 18 percent of some air pollutants. It also includes greenhouse gas emissions. The International Maritime Organization (IMO) estimates that carbon dioxide emissions from shipping were equal to 2.2% of the global human-made emissions in 2012 and expects them to rise 50 to 250 percent by 2050 if no action is taken. There is a perception that cargo transport by ship is low in air pollutants, because for equal weight and distance it is the most efficient transport method, according to shipping researcher Alice Bows-Larkin. This is particularly true in comparison to air freight. However, because sea shipment accounts for far more annual tonnage and the distances are often large, shipping's emissions are globally substantial. A difficulty is that the annual increasing amount of shipping overwhelms gains in efficiency, such as from slow-steaming or the use of kites. The growth in tonne-kilometers of sea shipment has averaged 4 percent yearly since the 1990s, and it has grown by a factor of 5 since the 1970s. There are now over 100,000 transport ships at sea, of which about 6,000 are large container ships. The fact that shipping enjoys substantial tax privileges has contributed to the growing emissions.
  • 25.0K
  • 31 Oct 2022
Topic Review
Water Well
A water well is an excavation or structure created in the ground by digging, driving, boring, or drilling to access groundwater in underground aquifers. The well water is drawn by a pump, or using containers, such as buckets, that are raised mechanically or by hand. Wells were first constructed at least eight thousand years ago and historically vary in construction from a simple scoop in the sediment of a dry watercourse to the qanats of Iran, and the stepwells and sakiehs of India. Placing a lining in the well shaft helps create stability, and linings of wood or wickerwork date back at least as far as the Iron Age. Wells have traditionally been sunk by hand digging, as is the case in rural areas of the developing world. These wells are inexpensive and low-tech as they use mostly manual labour, and the structure can be lined with brick or stone as the excavation proceeds. A more modern method called caissoning uses pre-cast reinforced concrete well rings that are lowered into the hole. Driven wells can be created in unconsolidated material with a well hole structure, which consists of a hardened drive point and a screen of perforated pipe, after which a pump is installed to collect the water. Deeper wells can be excavated by hand drilling methods or machine drilling, using a bit in a borehole. Drilled wells are usually cased with a factory-made pipe composed of steel or plastic. Drilled wells can access water at much greater depths than dug wells. Two broad classes of well are shallow or unconfined wells completed within the uppermost saturated aquifer at that location, and deep or confined wells, sunk through an impermeable stratum into an aquifer beneath. A collector well can be constructed adjacent to a freshwater lake or stream with water percolating through the intervening material. The site of a well can be selected by a hydrogeologist, or groundwater surveyor. Water may be pumped or hand drawn. Impurities from the surface can easily reach shallow sources and contamination of the supply by pathogens or chemical contaminants needs to be avoided. Well water typically contains more minerals in solution than surface water and may require treatment before being potable. Soil salination can occur as the water table falls and the surrounding soil begins to dry out. Another environmental problem is the potential for methane to seep into the water.
  • 2.6K
  • 27 Oct 2022
Topic Review
Rainfall Threshold
Sediment-related disaster is one of the most significant natural disasters, from the perspective of magnitude, damage and loss to human life and infrastructure, and disruption to socio-economic activities. The rainfall threshold is the condition or amount of rainfall that is likely to initiate sediment-related disasters, it is agreed that the rainfall threshold is the most significant tool to predict impending occurrences.
  • 1.6K
  • 26 Oct 2022
Topic Review
Permeability (Earth Sciences)
Permeability in fluid mechanics and the earth sciences (commonly symbolized as κ, or k) is a measure of the ability of a porous material (often, a rock or an unconsolidated material) to allow fluids to pass through it. The permeability of a medium is related to the porosity, but also to the shapes of the pores in the medium and their level of connectedness.
  • 4.9K
  • 25 Oct 2022
Topic Review
Chemical Waste
Chemical waste is waste , that is made from chemicals that are mostly produced by large factories. Chemical waste can damage , the environment and cause health problems and as such may fall under regulations such as COSHH in the United Kingdom or the Clean Water Act and Resource Conservation and Recovery Act in the United States . In the U.S., the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA), as well as state and local regulations also regulate chemical use and disposal. The disposal and handling of radioactive waste is a particular focus for regulatory bodies due to the environmental and health risks of radiation and the challenges of safe disposal. Chemical waste may or may not be classed as hazardous waste. A chemical hazardous waste is a solid, liquid, or gaseous material that displays either a "Hazardous Characteristic" or is specifically "listed" by name as hazardous waste. There are four characteristics chemical wastes may have to be considered hazardous. These are ignitability, corrosivity, reactivity, and toxicity. This type of hazardous waste must be categorized as to its identity, constituents, and hazards so that it may be safely handled and managed. Chemical waste is a broad term and encompasses many types of materials. The Material Safety Data Sheet (MSDS), Product data sheet or Label can provide a list of constituents. These sources should state whether this chemical waste is a waste that needs special disposal.
  • 1.8K
  • 24 Oct 2022
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