SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 85007
CASRN 85-00-7
SynonymsDiquat dibromide
Dipyrido[1,2-a:2',1'-c]pyrazinediium, 6,7-dihydro-, dibromide
Aquacide
Dextrone
Reglone
Analytical Method EPA Method 549.2
Molecular FormulaC12H12N22Br

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

Use CONTACT HERBICIDE USED ALSO TO PRODUCE DESICCATION & DEFOLIATION. ITS USES INCL POTATO HAULM DESTRUCTION (420-840 G DIQUAT/HA) USED AS DESICCANTS TO AID HARVESTING (ON COTTON, RAPE, & OTHER OIL SEED CROPS, CEREALS, LUCERNE, ETC) & TO ASSIST IN THE CONSERVATION OF FORAGE (PREWILTING FOR SILAGE, PREPN OF STANDING HAY, ETC). HERBICIDE FOR INDUSTRIAL, COMMERCIAL, & AQUATIC USES. SUGARCANE-FLOWERING SUPPRESSANT Plant growth regulator
Consumption Patterns HERBICIDE FOR INDUSTRIAL/COMMERCIAL USES, 67%; AQUATIC USES, 33% (1982)
Apparent Color Colorless to yellow crystals
Melting Point 335-340 DEG C
Molecular Weight 344.07
Density 1.22 TO 1.27 @ 20 DEG C/20 DEG
Sensitivity Data Diquat concentrate may cause severe skin irritation and burning on contact. Contact with dilute liquid or dust formulations of diquat may result in reversible skin irritation. Systemic toxicity may occur from skin absorption, especially with repeated contact. Contact with dilute liquid or dust (Diquat dibromide) formulations may cause reversible eye irritation. Some respiratory distress may be present in acute poisoning, but it is nonspecific.
Environmental Impact Diquat is released to the environment during its use as a herbicide, seed dessicant, and aquatic weed control agent. In the atmosphere, it will exist mainly as an aerosol and be subject to photolysis (half-life approx. 2 days) and gravitational settling. It will tightly bind to the upper layers of soil where it may remain for long periods of time. The binding to some soils is considered to be irreversible and makes it unavailable for biodegradation and photodegradation. Diquat is removed rapidly from aquatic systems, principally by adsorption. If adsorption is initially to weeds, biodegradation to soluble or volatile products occurs in several weeks. When sorbed to sediment, little or no degradation probably occurs. In any case, the diquat disappears from the water in 2-4 weeks. Little or no bioconcentration in fish will occur. Human exposure will principally be by agriculture workers or others who use the chemical or are in the vicinity of fields or bodies of water where diquat is used.
Environmental Fate TERRESTRIAL FATE: Diquat is rapidly adsorbed by clay constituents of soil and in the sorbed state is resistant to biodegradation and photodegradation. The duration of residual activity in soil is a few days ; the deactivation resulting from its binding to the soil. In some soils such as montorillonite clay, adsorption is considered irreversible. There is some evidence of a more loosely bound component, the fraction of which depends on the type of soil may be subject to slow biodegradation. AQUATIC FATE: Diquat is intentionally applied to water to control aquatic weeds. Diquat disappeared from two experimental ponds within 14 and 30 days and was more persistent in the pond that had a lower average temperature of 18 deg C . The most reasonable explanation for the difference in persistence in the two ponds was a higher turbidity level and hence more adsorption in the pond from which the diquat disappeared the fastest . When added to a weed-infested simulated lake impoundment, it was initially adsorbed by the weeds. After complete weedkill (4 days after treatment), biodegradation proceeded rapidly. After 22 days, only 1% of the diquat remained in the water and 19% was adsorbed to sediment. The organically-bound diquat was available for microbial degradation and formed water soluble and volatile products . In other studies, diquat concentrations in a reservoir declined from 1000 to 9 ppb in 12 days and levels in New York lakes declined to <.005 ppm 8 days after 4.48 kg/ha was applied . It is contended that the dissipated diquat was merely adsorbed to hydrosoil . Diquat will photodegrade in surface layers of water in 1-3 or more weeks when not adsorbed to particulate matter. AQUATIC FATE: Should diquat be released to the atmosphere during spraying operations, it would be associated with aerosols. It will be subject to photolysis (half-life approx 48 hrs) and gravitational settling.
Drinking Water Impact DRINKING WATER: Diquat is rapidly oxidized by chlorine oxide above pH 8.14 and below pH 7.12 . Similar results are observed for chlorine gas . Therefore, diquat would disappear rapidly from chlorinated drinking water which was slightly alkaline.

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