title: Sorption and degradation of pesticides in nursery recycling ponds.
abstract: Knowledge of pesticide distribution and persistence in nursery recycling pond water and sediment is critical for preventing phytotoxicity of pesticides during water reuse and to assess their impacts to the environment. In this study, sorption and degradation of four commonly used pesticides (diazinon, chlorpyrifos, chlorothalonil, and pendimethalin) in sediments from two nursery recycling ponds was investigated. Results showed that diazinon and chlorothalonil were moderately sorbed [K(OC) (soil organic carbon distribution coefficient) from 732 to 2.45 x 10(3) mL g(-1)] to the sediments, and their sorption was mainly attributable to organic matter content, whereas chlorpyrifos and pendimethalin were strongly sorbed (K(OC) > or = 7.43 x 10(3) mL g(-1)) to the sediments, and their sorption was related to both organic matter content and sediment texture. The persistence of diazinon and chlorpyrifos was moderate under aerobic conditions (half-lives = 8 to 32 d), and increased under anaerobic conditions (half-lives = 12 to 53 d). In contrast, chlorothalonil and pendimethalin were quickly degraded under aerobic conditions with half-lives < 2.8 d, and their degradation was further enhanced under anaerobic conditions (half-lives < 1.9 d). The strong sorption of chlorpyrifos and pendimethalin by the sediments suggests that the practice of recycling nursery runoff would effectively retain these compounds in the recycling pond, minimizing their offsite movement. The prolonged persistence of diazinon and chlorpyrifos, however, implies that incidental spills, such as overflows caused by storm events, may contribute significant loads of such pesticides into downstream surface water bodies.
authors.affiliation: Department of Environmental Sciences, University of California-Riverside, Riverside, CA 92521, USA. Jianhang@ucr.edu
authors.forename: Jianhang
authors.initials: J
authors.lastname: Lu
authors.forename: Laosheng
authors.initials: L
authors.lastname: Wu
authors.forename: Julie
authors.initials: J
authors.lastname: Newman
authors.forename: Ben
authors.initials: B
authors.lastname: Faber
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Merhaut
authors.forename: Jianying
authors.initials: J
authors.lastname: Gan
mesh_terms: D000327:Adsorption; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D001711:Biotransformation; D003247:Conservation of Natural Resources / Q000379:methods; D010575:Pesticides / Q000032:analysis* / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism; D018508:Water Purification / Q000379:methods
chemical_list: D010575:Pesticides; D014874:Water Pollutants, Chemical