Use in rice paddies

Using as starting materials 2-chloropropanoic acid, aniline, and 2-naphthol, propose a synthesis of naproanilide, a herbicide used in rice paddies in Asia ... 

Starting materials for the synthesis of the herbicide propanil, a weed killer used in rice paddies, are... 

Concentrations of Herbicides Used in Rice Paddy Fields in River Water and Impact on Algal Production... 

Ammonium Chloride. Most ammonium chloride [12125-02-9], NH Cl, is used as rice paddy fertilizer small amounts are used in dry cells and as fluxing agents (see Ammonium COMPOUNDS). 

Na is a very reactive substance which is never found free in nature. It is not generally used as an incendiary agent as such but, because of its tendency not only to float on w, but also to ignite spontaneously in contact with it, it may be added to napalm for use against river targets or enemy positions in rice paddy fields or in snow (Ref 7, p 103 Ref 4, pp 28-29)... 

The application of pesticides to paddy fields represents a unique set of issues compared with many other use patterns. Agrochemicals used in rice production are introduced directly or indirectly into paddy water, and there are more opportunities for... 

Kok, L.T., 1973. Toxicity of insecticides used for Asiatic rice borer control to tropical fish in rice paddies. In Farvar, M.U., Milton, J.P. (Eds.), The Careless Technology, Chapter 26. The Natural History Press, New York. 

Structure VII (with R = CC13 and R2 = H) is useful for controlling water grass in rice paddies (9). We have done some studies on this and... 

The ammonium chloride process, developed by Asalii Glass, is a variation of the basic Solvay process (9—11). It requires die use of solid sodium cliloride but obtains higher sodium conversions (+90%) than does the Solvay process. This is especially important in Japan, where salt is imported as a solid. The major difference from the Solvay process is that here the ammonium cliloride produced is crystallized by cooling and dirougk die addition of solid sodium cliloride. The resulting mother liquor is then recycled to dissolve additional sodium cliloride. The ammonium cliloride is removed for use as rice paddy fertilizer. Ammonia makeup is generally supplied by an associated synthesis plant. 

It has been proposed to use hemoglobin adducts in biomonitoring, as a dosimeter for the biologically active dose of arylamines/arylacetamides. This may also provide information about the individual susceptibility to the toxic and carcinogenic effects of these chemicals30,31. Field workers exposed to Propanil (38), a major herbicide in rice paddies,... 

When applied as a spray, PBO may come into contact with the surface of water bodies either indirectly through spray drift or by direct application, for example in insect control in rice paddies. This situation can be simulated in the laboratory using small-scale sediment and water microcosms (Fig. 7.3). Such systems are useful in estimating the rate of loss of the applied compound from the water phase to the sediment and any subsequent redistribution of parent compound or metabolites. 

Applications of immunoassay to pesticide chemistry have been described which address some difficult problems in analysis by classical methods. These include stereospecific analysis of optically active compounds such as pyrethroids (38), analysis of protein toxins from Bacillus thuringiensis (5,37), and compounds difficult to analyze by existing methods, such as diflubenzuron (35) and maleic hydrazide (15 also Harrison, R.O. Brimfield, A.A. Hunter, K.W.,Jr. Nelson, J.O. J. Agric. Food Chem. submitted). An example of the excellent specificity possible is seen in assays for parathion (10) and its active form paraoxon (3). Some immunoassays can be used directly for analysis without extensive sample extraction or cleanup, dramatically reducing the work needed in typical residue analysis. An example of this is given in Figures 2 and 3, comparing the direct ELISA analysis of molinate in rice paddy water to the extraction required before GC analysis. 

The Gas Stripping System. This system has been the most popular for denitrification stupes probably because it provides the most immediate and sensitive measurement of denitrification rates. It was first used by Gersberg et al. (13,14) to measure denitrification rates in rice paddy soils, sediments, and hypoltonion water, and later by Tiedje et al. (15) and Stout and More (16) to measure denitrification rates in soils. A schematic of the system used by our group is shown in Figure 1. 

Tejada AW, Varca LM, Calumpang SMP, et al. 1997. Fate of pesticides in a model rice paddy ecosystem. In Environ Behav Crop Prot Chem Proc Int Symp Use Nucl Relat Tech Stud Environ Behav Crop Prot Chem 1996, Int Atom Energy Agency Vienna, Austria pp. 265-278. 

Sonication helps improve solid-liquid extractions. Usually a finely ground sample is covered with solvent and placed in an ultrasonic bath. The ultrasonic action facilitates dissolution, and the heating aids the extraction. There are many EPA methods for solids such as soils and sludges that use sonication for extraction. The type of solvent used is determined by the nature of the analytes. This technique is still in widespread use because of its simplicity and good extraction efficiency. For example, in research to determine the amount of pesticide in air after application to rice paddy systems, air samples collected on PUF were extracted by sonication, using acetone as the solvent. The extraction recoveries were between 92% and 103% [21]. 

Damgaard LR, Revsbech NP, Reichardt W. 1998. Use of an oxygen-insensitive microscale biosensor for methane to measure methane concentration profiles in a rice paddy. Applied and Environmental Microbiology 64 864-870. 

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