Characterizing Aquatic Ecological Risks From Pesticides Using a Diquat Dibromide Case Study. I. Probabilistic Exposure Estimates

Abstract

Abstract-Diquat dibromide (6,7-dihydrodipyrido [1,2-a:2Ј,1Ј-c] pyrazinediium dibromide; diquat) is one of the few herbicides registered for direct application to water systems in the United States to control noxious aquatic weeds. The dissipation of diquat dibromide in aquatic environments is highly dependent on the hydrodynamic and physicochemical characteristics of the receiving water body. Computer simulations (EXAMSII) were conducted to evaluate the variability of diquat cation dissipation in farm ponds, lakes, and canals following applications to control aquatic weeds across the United States. Within each scenario, probabilities were assigned to varying values for physical properties (velocity, dispersion, suspended sediment concentrations, bed sediment properties, and plant biomass) using a joint probability method, and the results were expressed as spatially and temporally explicit cumulative probability distributions by water-body type on a regional scale. The results showed that the dissipation of diquat cation in water was very rapid, with the highest exposure concentrations (90th percentile) predicted to be 0.194 mg/L diquat cation 1 h after treatment and typically reaching 0.01 mg/L by 96 h.

Effects of Aquatic Herbicides and Housing Density on Abundance of Pond-Breeding Frogs

“…In Florida the aquatic weed problem is related to the extent of surface water, climate, weed species and factors affecting dissemination of aquatic plants including recreational use and interconnections between waterways (Ritter et al, 2000).…”

“…Times to disappearance are useful tools for predicting impacts on biota and wildlife, particularly when used with calculated or estimated half-lives (Waterborne, 1995 andRitter et al, 2000). The persistence of diquat varies widely depending on the conditions of the system being tested.…”

“…With the exception of contamination by spills or illegal dumping, none these routes of ground water contamination is likely since diquat tenaciously adheres to soil and sediment and is unlikely to be released from soil except under the conditions of very heavy liming (Weber . With respect to ground water movement, the difference between terrestrial and aquatic weed control uses of diquat is that lakes provide, in essence, an isolated incubator in which diquat can be slowly released from the sediment and dissipated through slow microbial degradation or horizontal/vertical dispersion and advection by the slow flow of the water body (Ritter, 2000 andWaterborne, 1995).…”

Synthesis and Evaluation of Pyrazine Derivatives with Herbicidal Activity

“…It is used for preharvest desiccation of many crops, as a defoliant on hops, for general weed control on non crop land etc. (Ritter et al, 2000;Ivany, 2005). It is applied as an aquatic www.intechopen.com herbicide in many countries since the late 1950s for control of emergent and submerged aquatic weeds (Ritter et al, 2000).…”

“…(Ritter et al, 2000;Ivany, 2005). It is applied as an aquatic www.intechopen.com herbicide in many countries since the late 1950s for control of emergent and submerged aquatic weeds (Ritter et al, 2000). According to Massachusetts Department of Agricultural Resources (2010) following weeds are controlled by diquat: i) submersed aquatics: Ultricularia, Ceratophyllum demersum, Elodea spp., Najas spp., Myriophyllum spp., Hydrilla verticillata, Potamogeton spp.…”