Volatilization of Parathion and Chlorothalonil from a Potato Crop Simulated by the PEARL Model

Abstract

The volatilization of pesticides from crop canopies in the field should be modeled within the context of evaluating environmental exposure. A model concept based on diffusion through a laminar air-boundary layer was incorporated into the PEARL model (pesticide emission assessment at regional and local scales) and used to simulate volatilization of the pesticides parathion and chlorothalonil from a potato crop in a field experiment. Rate coefficients for the competing processes of plant penetration, wash off, and phototransformation in the canopy had to be derived from a diversity of literature data. Cumulative volatilization of the moderately volatile parathion (31% of the dosage in 7.6 days) could be simulated after calibrating two input data derived for the related compound parathion-methyl. The less volatile and more slowly transformed chlorothalonil showed 5% volatilization in 7.6 days, which could be explained by the simulation. Simulated behavior of the pesticides in the crop canopy roughly corresponded to published data.

Estimation/calculation of emissions of Plant Protection Products from protected crops greenhouses and cultivations grown under cover) to support the Development of risk assessment methodology under Council Directive 91/414/EEC and EU regulation 1107/2009 (EC)

“…Consensus PEARL was chosen for this assignment because it allows the use of hourly climatic data and because it has been tested against data from field and wind tunnel experiments by Leistra et al (2005Leistra et al ( , 2007Leistra et al ( , 2008. The model concepts are similar to those of the greenhouse emission model, and every effort was made to harmonise the two modelling approaches as much as possible, but there are some conceptual differences that could not be overcome.…”

Effect of the spray volume adjustment model on the efficiency of fungicides and residues in processing tomato

“…Chlorothalonil vapor pressure of 0.076 mPa at 25°C (Tomlin, 2000) facilitates its disappearance from plant surface. However, the results obtained in a field on potato crops showed only 5% volatilization after 7.6 days (Leistra & Van Den Berg, 2007), while on wheat crops 0.6% after 31 h (Bedos et al, 2010) and 2.9% after 5 days (Lichiheb et al, 2014). Azoxystrobin vapor pressure of 1.1 × 10 -7 mPa at 20 °C (Tomlin, 2000) causes low risk of the loss of substance as a result of volatilization.…”

“…According to vapor pressure of chlorothalonil (0.076 mPa at 25 °C) and azoxystrobin (1.1 × 10 -7 mPa at 20 °C) the potential risk of volatilisation was higher for the first fungicide (Tomlin, 2000). However in field trial on potato the fate of chlorothalonil due to volatilization was only 5% after 7.6 days (Leistra & Van Den Berg, 2007). Furthermore, Monadjemi et al (2011) estimated half-life of chlorothalonil due to photodegradation at 5.3 days.…”

Environmental Fate and Toxicology of Chlorothalonil

“…Because of the low vapor pressure, initial volatilization is slow and volatility loss continues over a longer time period (Leistra and Van den Berg 2007). In general, the volatilization of chlorothalonil can be regarded as negligible and does not represent a significant dissipation route.…”

“…Aqueous dissolved concentrations of chlorothalonil absorb sunlight within the wavelength range of 300-340 nm, and direct photolysis represents a major degradation pathway for this fungicide (Leistra and Van Den Berg 2007). Chlorothalonil, exposed directly to light (300-400nm) photolytically degraded more rapidly in natural waters (DT 50 = 0.21-0.76 d) than in a buffered aqueous system (pH 7; DT 50 = 1.1d; Wallace et al 2010).…”