SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 19044883
CASRN 19044-88-3
SynonymsOryzalin
Benzenesulfonamide, 4-(dipropylamino)-3,5-dinitro-
Surflan
Analytical Method EPA Method 638
Molecular FormulaC12H18N4O6S

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use Selective pre-emergence herbicide Control of many annual grasses and broad-leaved weeds in cotton, fruit trees, nut trees, vines, ornamentals, soya beans, groundnuts, oilseed rape, sunflowers, lucerne, peas, sweet potatoes, mint, and non-crop areas. At recommended rates, oryzalin is effective for controlling many annual grass and broadleaf weeds such as: barnyardgrass (Echinochloa crusgalli), annual bluegrass (Poa annua), brachiaria (Brachiaria sp.), browntop panicum (Panicum fasciculatum), crabgrasses (Digitaria sp.), crowfootgrass (Dactyloctenium aegyptium), Southwestern cupgrass (Eriochloa gracilis), fall panicum (Panicum dichotomiflorum), foxtails (Setaria sp.), goosegrass (Eleusine indica), seedling johnsongrass (Sorghum halepense), wild oat (Avena fatua), Texas panicum (Panicum texanum), carpetweed (Mollugo verticillata), common purslane (Portulaca oleracea), Florida purslane (Richardia scabra), lambsquarters (Chenopodium album), pigweeds (Amaranthus sp.), chickweed (Stellaria media), and prostrate spurge (Euphorbia supina). Surface-applied herbicide for established bermudagrass turf, and established ornamentals. C-327]
Apparent Color Yellow-orange crystals
Odor No appreciable odor
Melting Point 137-138 deg C
Molecular Weight 346.36
Sensitivity Data Slightly to moderately irritating to skin, eyes, and mucous membranes.
Environmental Impact Oryzalin's use as a pre-emergence herbicide releases the compound directly to the environment through applications in sprays and other routes of application. If released to the atmosphere, oryzalin will degrade rapidly in the vapor-phase by reaction with photochemically produced hydroxyl radicals (half-life of about 3.7 hr). Particulate-phase oryzalin and aerosols released to air during spray applications of oryzalin herbicides will be physcially removed from air by dry and wet deposition. If released to soil or water, oryzalin may degrade through microbial degradation and photodecomposition. The results of one biological screening study (which demonstrates the role of microorganisms) have shown that oryzalin degrades much slower in sterilized soil as compared to nonsterile soil. Sunlight exposure studies have shown that oryzalin photodecomposes after application to soil surfaces and exposure to sunlight. Delaying soil incorporation increases oryzalin's degradation in soil. Oryzalin leaches to a limited extent under natural rainfall conditions. The soil persistence half-life can range from 15 days to several months. Occupational exposure to oryzalin occurs through dermal contact and inhalation of sprays, especially to workers applying the compound as a herbicide.
Environmental Fate TERRESTRIAL FATE: Microbial degradation and photodecomposition contribute to the degradation of oryzalin in soil . The results of one biological screening study, which demonstrates the role of microorganisms, have shown that oryzalin degrades much slower in sterilized soil as compared to nonsterile soil . Sunlight exposure studies have shown that oryzalin photodecomposes when oryzalin (applied to soil surfaces) is exposed to sunlight(3-4). In one photodegradation study , oryzalin was applied to air dried clay loam and exposed to unfiltered solar radiation for 7 days in July ; comparison with 7 day dark controls indicated that 26.2% of initially applied oryzalin had photodecomposed . Koc values of 75 to 150 indicate a medium to high mobility in soil(5,SRC); however, results of field, greenhouse and laboratory studies have shown that oryzalin does not leach appreciably in soil, especially when the moisture content is low(5-6). Limited leaching can occur under natural rainfall conditions . TERRESTRIAL FATE: In greenhouse studies using Drummer silty clay loam and Cisne silt loam soils, oryzalin was observed to have a persistence half-life ranging from 1.6 to 4.3 months . In laboratory studies using Weld loam soil, oryzalin had half-lives of 1.4 and 4.35 months at respective temperatures of 30 and 15 deg C under aerobic conditions ; under anaerobic conditions, the half-life fell to 0.34 months . In 1974 and 1975 Wisconsin field studies, oryzalin was observed to have an initial half-life of approximately 15 to 40 days . Presumably due to surface photodegradation, delaying the time between soil application and soil incorporation will increase oryzalin's degradation in soil ; in one test, a 7 day delay reduced the oryzalin concn by nearly 20% . The US Dept of Agric's Pesticide Properties Database lists a soil half-life of 20 days for oryzalin . AQUATIC FATE: Using (14)C labelled oryzalin and a terrestrial aquatic laboratory model ecosystem, an oryzalin BCF value of 50 was determined for fish (Gambusia affinis) ; this BCF value suggests that bioconcentration in aquatic organisms may not be an important fate process. The relative importance of individual degradation processes has not been determined for natural water. Since photodegradation and microbial degradation have been identified as important mechanisms for soil systems(2-4), they may also be important in water. Adsorption to aquatic sediments is not likely to be important based upon experimentally-derived Koc values of 75 to 180(5,SRC). Aquatic volatilization is not expected to be an important fate process. ATMOSPHERIC FATE: Based upon a reported vapor pressure of <1X10-8 mm Hg at 25 deg C , oryzalin can exist in both the vapor and particulate-phases in the ambient atmosphere(2,SRC). It will degrade rapidly in the vapor-phase by reaction with photochemically produced hydroxyl radicals with an estimated half-life of about 3.7 hr(3,SRC). Particulate-phase oryzalin and aerosols released to air during applications of oryzalin herbicides will be removed from air physically by dry and wet deposition.

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