Agriculture arsenic

Phosphate. Phosphoms occurs in water primarily as a result of natural weathering, municipal sewage, and agricultural mnoff The most common form in water is the phosphate ion. A sample containing phosphate can react with ammonium molybdate to form molybdophosphoric acid (H2P(Mo202q)4). This compound is reduced with stannous chloride in sulfuric acid to form a colored molybdenum-blue complex, which can be measured colorimetrically. SiUca and arsenic are the chief interferences. 

Monosodium methanearsonate (MSMA) [2163-80-6] CH AsONaOOH, disodium methanearsonate (DSMA) [144-21-8], CH2AsO(NaO)2, cacodyhc acid [75-60-5], (CH2)2AsOOH, and arsenic acid [7778-39-4], H AsO, are used ia agriculture appHcations (11,12). MSMA, DMSA, and cacodyUc acid are used as herbicides (qv) especially ia cotton (qv) fields for the control of Johnson and nutsedge grass and other weeds. Arsenic acid (13) and cacodyhc acid may be used as a desiccant for the defoHation of the cotton boU prior to harvesting. Calcium arsenate [7778-44-1], Ca2(As0 2> once an important chemical for the control of the boU weevil and cotton worm, has disappeared from appHcation and the use of lead arsenate [7784-40-9], Pb AsO, for fmit crops is currentiy restricted. 

The commercial uses of arsenic compounds in 1988, measured in terms of elemental arsenic, are wood (qv) preservatives, 69% agricultural products (herbicides (qv) and desiccants (qv)), 23% glass (qv), 4% nonferrous alloys and electronics, 2% and animal feed additives and pharmaceuticals (qv), 2% (see Feeds AND feed additives). Chromated copper arsenate (CCA) [11125-95-4] is the most widely used arsenic-based wood preservative. The Environmental Protection Agency has, however, restricted the use of arsenical wood preservatives to certified appHcators. 

Aristech Chemical Corporation, See Sunoco Chemicals Unit of Smioco hic. (US), 217 Arizona Chemical, 217 Arizona Department of Agriculture, 290 Arizona Department of Eiivkonmental Quality, 290 Arizona Industrial Commission, 290 Arizona Poison and Drug hiforniation Center, 311 Arkansas Department of Eiivironmental Quality, 290 Arkansas Poison and Drug Infomiation Center, 311 Arkansas State Plant Board, 290 Aniienian National Academy of Sciences, 255 Armour Polymers Ltd., 168 Arris Intemational Corporation, 218 Arsenic acid, 19... 

Tlie use of As comjiounds as herbicides and pest controls in agriculture is now considerably restricted because of environmental considerations though arsenic acid itself. AsO(OH).v, is still used in die formulation of wood preservatives. The oxide is widely used to decolorize glass. 

To Muller, just starting out on his search for an effective insecticide, the situation looked desperate indeed. A flood of patents had already been issued, and he realized that the chances were worse than poor only a particularly cheap or remarkably effective insecticide had any prospects of being used in agriculture. Yet there was hope. After experimenting with products described in the patent literature, he realized that practically none of the new compounds was being sold the existing arsenates, pyrethrum, and rotenone insecticides were more effective. Reassured about the competition, Muller had the courage to press on. 

Clearly pollution hazards exist when inorganic arsenic compounds are introduced into an environment where anaerobic bacteria are growing. Arsenic impurities in the phosphate used in detergents and for agricultural practices may pose serious problems because of the continuing synthesis of deadly poisonous methylarsenic compounds. 

Hawaiian streams received most of their lead from urban runoff, vehicle sources, and agricultural and residential use of lead arsenate (May and McKinney 1981). 

Large quantities of arsenicals are released into the environment as aresult of industrial and especially agricultural activities, and these may pose potent ecological dangers. 

Attention focused on inorganic arsenical pesticides after accumulations of arsenic in soils eventually became toxic to several agricultural crops, especially in former orchards and cotton fields. Once toxicity is observed, it persists for several years even if no additional arsenic treatment is made (Woolson 1975). Poor crop growth was associated with bioavailability of arsenic in soils. For example, alfalfa (Medicago sativa) and barley (Hordeum vulgare) grew poorly in soils con-... 

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