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.

Adsorption and degradation of triazophos, chlorpyrifos and their main hydrolytic metabolites in paddy soil from Chaohu Lake, China

“…Interestingly, the log K OC of TCP (1.95e2.46) in this study was similar to previously published results in different soils (1.43e2.59, 1.85e2.20 and 1.88e2.10) (Racke, 1993;Baskaran et al, 2003). The log K OC of chlorpyrifos (3.40) was lower than the previously published result (3.68e4.19) (Racke, 1993;Baskaran et al, 2003;Lu et al, 2006). The mechanism of chlorpyrifos partitioning and the model that best fits the shape of the isotherm is currently in debate.…”

Dose-response curve to soil applied herbicides and susceptibility evaluation of different amaranthus species using model identity

“…herbicides such as pendimethalin, high soil OM and clay contents reduce herbicide availability in soil solution (Lu et al, 2006;Sharma & Singh, 2007) leading to the need of higher doses to ensure adequate control. ) ( Table 2).…”

Sorption of hydrophobic pesticides on a Mediterranean soil affected by wastewater, dissolved organic matter and salts

“…K OC values for pendimethalin ranged between 1.0 and 2.2 Â 10 4 (Zheng and Cooper, 1996;Lu et al, 2006), between 5.2 Â 10 3 and 7.7 Â 10 4 for deltamethrin (Zhu and Selim, 2002) and 6.1 Â 10 4 for a-cypermethrin (www.…”