Major environmental problem

Residue Disposal. The major environmental problem in the Bayer process is disposal of bauxite residue which is effected by marine disposal, lagooning, use of underdrain lakes, or semidry disposal. Marine disposal in oceans or rivers, diluting the alkaline residue by large quantities of water, is environmentally unacceptable. Lagooning behind retaining dikes built around clay-sealed ground is commonly used, but there have been isolated leaks into aquifers. This has motivated installation of underdrains between the residue and clay-sealed, plastic-lined, lake bottom. This design removes the hydraulic head from the lake bottom and improves consoHdation of the residue. 

Nitrate is one of the facts of life. It is essential for the growth of many plant species, including most of those we eat, but it becomes a problem if it gets into water in which it is not wanted. It is perceived mainly as a chemical fertilizer used by farmers, but much of the nitrate found in soil is produced by the microbes that break down plant residues and other nitrogen-containing residues in the soil. There is no difference between nitrate from fertilizer and that produced by microbes, but, whatever its origin, this rather commonplace chemical entity has now become a major environmental problem and is also treated as a health hazard. 

One major environmental problem is associated with the Bayer process for alumina production from bauxite. The residue (called red mud ) which is obtained in the process contains unextracted oxides (e.g., alumina, ferric oxide, titanium dioxide, silicon dioxide, calcium oxide) and various insoluble materials. This solid waste is washed and discharged into impoundment ponds or into the marine environment. 

Global climate change (GCC), 26 692-693. See also Global warming as a major environmental problem,... 

Green governments, 23 50 Greenhouse effect, 7 806-808 26 28 as a major environmental problem, 27 529-530... 

One of the major environmental problems facing the pulp and paper industry is the disposal of sludges. These arise from the settlement of... 

The contamination of groundwater by leakage of hydrocarbons or other pollutants from underground storage tanks, distribution systems and various industrial operations is a major environmental problem. Conventional treatment techniques suffer from serious shortcomings which limit their applicability and efficiency. These include high cost and maintenance requirements, the need to transfer the contamination from one medium to another, and the extended duration of the operation, since decades may be necessary to prevent continued growth of contaminant plumes (Yerushalmi et al., 1999). An alternative to these treatments lies in in situ remediation. 

Starting from Trifluoroacetic Acid Derivatives Trifluoroacetic acid and its derivatives (e.g., esters, anhydride, fluoral, trifluoroethanol) are the major channel of the organic fluorine industry. They are relatively inexpensive and, compared to halons, they do not exhibit major environmental problems. They are the main source for the synthesis of trifluoromethylated compounds. 

Because of the elevated concentrations of potentially ecotoxic metals and acid in mine water, and because of the potential for precipitation of benthos-smothering Fe, Al, Mn-oxyhydroxides (and other phases) in downstream recipient watercourses, water draining from mines is often regarded as a major environmental problem. Considerable effort and expense are incurred by treating... 

The above are only a few examples of the numerous major environmental problems that were created by the introduction of new products and processes. They should serve as reminders, as societies develop new products and processes to satisfy their... 

Generally, catalysts are called into action to eliminate emissions from mobile (cars) and stationary (industry) sources, to take part in liquid and solid waste treatment, and contribute to the effort to reduce volatile organic compounds and gases that pose major environmental problems such as photochemical smog and (at a global level) the greenhouse effect. 

Acid Rain Acid rain, a second major environmental problem, results primarily from the production of sulfur dioxide, SC 2, that accompanies the burning of sulfur-containing coal in power-generating plants. Sulfur dioxide is slowly converted to SO3 by reaction with oxygen in air, and SO3 dissolves in rainwater to yield dilute sulfuric acid, H2SO4. 

Atoms with the same number of protons, but different numbers of neutrons in their nuclei are chemically identical atoms of the same element, but have different masses and may differ in their nuclear properties. Such atoms are isotopes of the same element. Some isotopes are radioactive isotopes, or radionuclides, which have unstable nuclei that give off charged particles and gamma rays in the form of radioactivity. Radioactivity may have detrimental, or even fatal, health effects a number of hazardous substances are radioactive, and they can cause major environmental problems. The most striking example of such contamination resulted from a massive explosion and fire at a power reactor in the Ukrainian city of Chernobyl in 1986. 

In the course of our allelopathic studies to isolate potential bioherbicides from plants, we focused our attention on medicinal plants and vegetable wastes, which represent a primary and neglected source of allelochemicals, assaying their allelopathic phytotoxicity and identifying the site(s) of action of allelochemicals on seeds.1,3,4,6 The annual production of one hundred million liters and deposition of olive oil mill wastewater is a major environmental problem for agriculture in the Mediterranean basin, where the olive (O/ea europaea L.) is the most economically important fruit tree, because it has provided valuable storable oil as well as edible fruit since ancient times.35... 

Ecosystems that are severely disrupted by invasion of human activity attract a lot of attention among environmentalists. Pollution of aqueous systems by heavy metal ions is considered a major environmental problem that requires immediate solution. Heavy metal ions such as mercury, cadmium, and lead are... 

One major environmental problem with this technique is that cyanide is highly toxic. Although attempts are made to loop the cyanide through a closed system to try to ensure that none is lost, cyanide does commonly... 

Plastic waste is becoming a serious global issue, thanks to extensive plastic usage all over the world, the treatment of waste plastic has gained the utmost importance. Scientists and experts all over the world are concerned over this major environmental problem which is expected to attain mammoth proportions by the year 2010, with an expected annual increase of global plastic consumption crossing the 5.5% mark. 

In the past there was general agreement over what the major environmental problems were, and how they should be controlled. 

Polychlorinated biphenyls (PCBs) are a major environmental problem. These oily substances have many uses, but they resist breakdown by bacterial action when spilled in the environment and, being fat-soluble, can accumulate to dangerous concentrations in the fatty tissues of fish and animals. One little-appreciated complication in controlling the problem is that there are 209 different PCBs, all now in the environment. They are generally similar, but their solubilities in fats differ considerably. The best measure of this is Kay, the equilibrium constant for the partition of a PCB between the fat-like solvent octanol and water. 

Acid precipitation is a major environmental problem thronghout the indnstrial-ized world. One major sonrce is the bnrning of fossil fnels containing snlfnr (coal, oil, and natnral gas). The snlfnr dioxide released into the air dissolves in water or, more serionsly, may be oxidized fnrther to snlfnr trioxide. The SO3 dissolves in water to form snlfnric acid ... 

Estimates for usage of coal in the U.S.A. for the year 1980 range up to S-IO metric tons (t) (Surprenant et at, 1975). Waste products from coal combustion include fly ash and bottom ash. Projected production of these ashes in 1980 is estimated at 75 10 t (Faber et al., 1976). Disposal of the ash material is one of the major environmental problems associated with the use of coal-fired power plants. 

Marine pollution by oil spills or harmful chemicals is still one of the major environmental problems to be faced. Besides the accidental releases of pollutants the main source is assumed from the controlled release by ship traffic and oil production platforms. Since accidents or violations of regulations can never be completely excluded, precautions and instruments are needed to detect and combat maritime pollutions and a crucial element of this framework is airborne surveillance. Like no other system, airborne pollution control is capable a) to detect possible oil spills by radar sensors,... 

In this chapter, we introduce some of the major environmental problems that our societies face, and point out the need for using geochemical modeling. 

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