Benzobicyclon (BUTTEÒ, Rogue) is a newly approved rice pro-herbicide in the United States in California and anticipated for registration in southern states such as Louisiana. Louisiana rice fields are a unique environmental in which crops are rotated with other agricultural commodities such as crawfish. South Louisiana is in a current state of land loss and coastal erosion, therefore the risk for saltwater intrusion is likely. Field studies using benzobicyclon have shown the parent compound appears to prefer to bind to sediment, and sediment is likely a sink for BZB, and the hydrolysis product prefers the water where it has shown to undergo photolysis. Previous studies have shown the half-life of benzobicyclon hydrolysate is significantly different between fresh and seawater, with half-lives ranging 76 hr in distilled water and 3.4 in ASW (25 ppt). The purpose of this investigation was to determine the ion(s) that are responsible for the increased photodegradation rate of BH. Ions were chosen and solutions were determined based upon their concentrations in 35 ppt seawater; ions included but were not limited to SO4-, HCO3-, Ca2+Mg2+, and transition metals including iron and copper. Half-lives ranged from 3.8 hours (35 ppt ASW) to 40 hr in SO4-to 117 hr in HCO3-, and after 24 hours of irradiation, no BH was detected in iron solutions. Understanding the fate of BZB is potentially important in fields that are treated with copper sulfate or that may be at risk for saltwater intrusion.

Ion-specific influences on the photodegradation of benzobicyclon hydrolysate in seawater

2019 Fall National Meeting

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