Soils fluoride

Patterson, M.M. et al., Assessment of Ambient, Plant Tissue, and Soil Fluoride Concentrations Associated with Phosphate Fertilizer Plant, Proceedings of Biogeochemistry of Trace Elements Conference, University of Guelph, Guelph, Ontario, Canada, 2001. 

An atomic absorption spectrophotometer has been applied for heavy metal determination in soils. Concentrations of potassium and sodium were determined with a flame photometer. For the determination of soil fluorides, an ion-selective electrode was used. Statistical methods were applied to describe quantitatively the relationships between industrial emissions and other components of the ecosystems. 

Fluoride is the most unique halide chemically and is the most common halide in igneous rocks. The igneous minerals fluorspar (CaF2) and apatite (Cas(F,OH)(P04)3) are both insoluble in water. Fluoride can substitute for OH- to some extent in soil minerals. This mechanism is probably also responsible for F retention by aluminium and iron hydroxides in acid soils. Fluoride also associates strongly with H+. HF is a weak acid, pK = 3.45. 

In 1954 the surface fluorination of polyethylene sheets by using a soHd CO2 cooled heat sink was patented (44). Later patents covered the fluorination of PVC (45) and polyethylene bottles (46). Studies of surface fluorination of polymer films have been reported (47). The fluorination of polyethylene powder was described (48) as a fiery intense reaction, which was finally controlled by dilution with an inert gas at reduced pressures. Direct fluorination of polymers was achieved in 1970 (8,49). More recently, surface fluorinations of poly(vinyl fluoride), polycarbonates, polystyrene, and poly(methyl methacrylate), and the surface fluorination of containers have been described (50,51). Partially fluorinated poly(ethylene terephthalate) and polyamides such as nylon have excellent soil release properties as well as high wettabiUty (52,53). The most advanced direct fluorination technology in the area of single-compound synthesis and synthesis of high performance fluids is currently practiced by 3M Co. of St. Paul, Minnesota, and by Exfluor Research Corp. of Austin, Texas. 

Minerals and Ash. The water-soluble extract solids which iafuse from tea leaves contain 10—15% ash. The tea plant has been found to be rich in potassium (24) and contains significant quantities of calcium, magnesium (25), and aluminum (26). Tea beverages are also a significant source of fluoride (27), owing in part to the uptake of aluminum fluoride from soils (28,29). 

The harmful effects of air pollutants on human beings have been the major reason for efforts to understand and control their sources. During the past two decades, research on acidic deposition on water-based ecosystems has helped to reemphasize the importance of air pollutants in other receptors, such as soil-based ecosystems (1). When discussing the impact of air pollutants on ecosystems, the matter of scale becomes important. We will discuss three examples of elements which interact with air, water, and soil media on different geographic scales. These are the carbon cycle on a global scale, the sulfur cycle on a regional scale, and the fluoride cycle on a local scale. 

Research has shown that when polychlorpinen, ammonium nitrate, and superphosphate are present together in the soil, phosgene, carbon monoxide, nitric oxide, hydrochloric acid, ammonia, hydrocyanic anions, ozone, hydrogen fluoride and phosphide, etc. could appear in the air over the beet fields. Photooxidants could also appear. Airborne toxic compounds over this crop were noted in areas after precipitation with little wind, and with an air temperature of over 2CP . The combined and complex activity of pesticides and other chemical compounds led people who manually sowed beets to develop symptoms of poisoning. [21]... 

Cooke, J.A., S.M. Andrews, and M.S. Johnson. 1990a. Lead, zinc, cadmium and fluoride in small mammals from contaminated grassland established on fluorspar tailings. Water Air Soil Pollut. 51 43-54. 

Sheppard, C.R.C. and D.J. Bellamy. 1974. Pollution of the Mediterranean around Naples. Mar. Pollut. Bull. 5 42-44. Shore, R.F. 1995. Predicting cadmium, lead and fluoride levels in small mammals from soil residues and by species-species extrapolation. Environ. Pollut. 88 333-340. 

Nixon277 compared atomic absorption spectroscopy, flame photometry, mass spectroscopy, and neutron activation analysis as methods for the determination of some 21 trace elements (<100 ppm) in hard dental tissue and dental plaque silver, aluminum, arsenic, gold, barium, chromium, copper, fluoride, iron, lithium, manganese, molybdenum, nickel, lead, rubidium, antimony, selenium, tin, strontium, vanadium, and zinc. Brunelle 278) also described procedures for the determination of about 20 elements in soil using a combination of atomic absorption spectroscopy and neutron activation analysis. 

Simple anions in soil are the halogens, chlorine (Cl ), and bromine (Br ). If present, the other halogens—fluoride, F, and iodide, I-—will also occur as simple anions. Because the compounds of these anions are generally soluble, they readily leach out of the soil and so are present at low concentrations. Exceptions occur in low-rainfall regions where significant, sometimes deleterious (to plants and animals), levels of simple anions can be found. 

There is only one simple anion commonly found in soil, and that is chloride (Cl ). Chloride is an essential nutrient for plants but is typically present in sufficiently high concentrations that deficiencies are never observed. If other halogens are present, they will also be present as simple anions. Most soils do contain small amounts of bromide as the second most common simple anion. In some cases, significant levels of fluoride and iodide may be present, although this is rare. These anions are generally soluble in water and tend to exist as the simple anion. However, they can combine with other components and exist as other species. For instance, halogens are present in organic compounds such as solvents, insecticides, and herbicides, which can be soil contaminants. There are also other nonionic species of these elements that may be present [20],... 

Inorganic salts that contain halogens are usually soluble. They commonly occur as simple, single, negatively charged anions in soil. There are two common exceptions to this generalization. First, fluorine is commonly found bonded to phosphate in insoluble minerals called apatites, which are calcium phosphate fluorides. 

A further spectrophotometric method [3, 4] for water soluble boron in soil, boron is extracted from soil with boiling water. Borate in the extract is converted to fluoroborate by the action of orthophosphoric acid and sodium fluoride. The concentration of fluoroborate is measured spectrophotometrically as the blue complex formed with methylene blue and which is extracted into 1, 2-dichloroethane. Nitrates and nitrites interfere they are removed by reduction with zinc powder and orthophosphoric acid. 

Anger WK, Moody L, Burg J, et al. 1986. Neurobehavioral evaluation of soil and structural fumigators using methyl bromide and sulfuryl fluoride. Neurotoxicology 7 137-156. 

Uses Manufacture of fluorocarbon refrigerants, fluorocarbon plastics, and propellants solvent for natural products analytical chemistry cleansing agent soil fumigant insecticides preparation of chlorodifluoromethane, methyl fluoride, salicylaldehyde cleaning electronic circuit boards in fire extinguishers. 

Trace element retention on earth materials is illustrated in several case studies, where selected contaminants (e.g., fluoride, cesium, mercury) interact with rocks, clays, soils, and sediments under different environmental conditions (e.g., pH, presence of organic ligands, salinity). 

Fluoride in minor concentrations is beneficial for animals and humans, bnt it becomes toxic when ingested in excessive amounts. Bar-Yosef et al. (1989) investigated adsorption kinetics and isotherms of K -montmorillonite and a series of soils (clay, 4-61% organic matter, 2-7%), as affected by solution pH. The flnoride... 

Fig. 8.35 Fluoride adsorption from aqueous suspensions as affected by pH (a) on K+- montmoril-lonite, (b) on six soils. (Bar-Yosef et al. 1989)...

Fluoride is widely distributed in soil and is present naturally in drinking water. 

Hiemstra,T, van Riemsdijk, W.H. Borkovec, M. (1996) Predicting multicomponent adsorption and transport of fluoride at variable pH in a goethite-silica sand system. Environ. Sci. Technol. 30 481-488 Mehra, O.P. Jackson, M.L. (1960) Iron oxide removal from soils and days by dithionite-ci-trate system buffered with sodium bicarbonate. Clays Clay Min. 7 317-327 Meier, M. Namjesnik-Dejanovic, K. Maurice,... 

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