Volatilization of Trifluralin, Atrazine, Metolachlor, Chlorpyrifos, α-Endosulfan, and β-Endosulfan from Freshly Tilled Soil

Abstract

The volatile and soil loss profiles of six agricultural pesticides were measured for 20 days following treatment to freshly tilled soil at the Beltsville Agricultural Research Center. The volatile fluxes were determined using the Theoretical Profile Shape (TPS) method. Polyurethane foam plugs were used to collect the gas-phase levels of the pesticides at the TPS-defined critical height above a treated field. Surface-soil (0-8 cm) samples were collected on each day of air sampling. The order of the volatile flux losses was trifluralin > alpha-endosulfan > chlorpyrifos > metolachlor > atrazine > beta-endosulfan. The magnitude of the losses ranged from 14.1% of nominal applied amounts of trifluralin to 2.5% of beta-endosulfan. The daily loss profiles were typical of those observed by others for volatile flux of pesticides from moist soil. Even though heavy rains occurred from the first to third day after treatment, the majority of the losses took place within 4 days of treatment, that is, 59% of the total applied atrazine and metolachlor and >78% of the other pesticides. Soil losses generally followed pseudo-first-order kinetics; however, leaching due to heavy rainfall caused significant errors in these results. The portion of soil losses that were accounted for by the volatile fluxes was ordered as follows: alpha-endosulfan, 34.5%; trifluralin, 26.5%; chlorpyrifos, 23.3%; beta-endosulfan, 14.5%; metolachlor, 12.4%; and atrazine, 7.5%.

Gas-phase pesticide measurement using iodide ionization time-of-flight mass spectrometry

“…Volatilization of these current-use pesticides from agricultural soils to the atmosphere removes up to 27 % of the applied pesticide (26.5, 12.4, and 7.5 % for trifluralin, metolachlor, and atrazine, respectively) (Rice et al, 2002). The resulting atmospheric concentrations vary, and these currentuse pesticides have been detected hundreds of meters to kilometers away from application sites in both gas and particle phases (Coscollà et al, 2010(Coscollà et al, , 2008LeNoir et al, 1999).…”

“…These solid adsorbents are analyzed by offline techniques, typically gas chromatography coupled to mass spectrometry (GC-MS) or electron capture detection (GC-ECD) (Bedos et al, 2006;Coscollà et al, 2010;Foreman et al, 2000;Glotfelty et al, 1989;LeNoir et al, 1999;Majewski et al, 2014;Peck A.M, 2005;Rice et al, 2002). These measurement approaches are adequate for offline quantitation of airborne pesticides, with detection limits for trifluralin ranging from 1.3 pg m −3 (GC-MS) to 0.4 µg m −3 (GC-ECD) with sample collection times of 24 and 2 h, respectively (Peck A.M, 2005;Bedos et al, 2006).…”

“…These measurement approaches are adequate for offline quantitation of airborne pesticides, with detection limits for trifluralin ranging from 1.3 pg m −3 (GC-MS) to 0.4 µg m −3 (GC-ECD) with sample collection times of 24 and 2 h, respectively (Peck A.M, 2005;Bedos et al, 2006). These techniques have proven successful in quantifying atmospheric pesticide concentrations, although offline analysis introduces steps that can alter a compound's structure and reduce sampling efficiency (Coscollà et al, 2010;LeNoir et al, 1999;Peck A.M, 2005;Rice et al, 2002), and it is inadequate for rapid ambient measurement. Rapid measurements are necessary for (i) observing pesticide drift in real time to understand meteorological effects; (ii) directly measuring volatilization and surfaceatmosphere fluxes by eddy covariance or other micrometeorological approaches; (iii) determining whether agricultural workers are exposed to low concentrations over a long period of time or high concentrations over a short period of time, and thus for identifying activities that can be targeted to reduce exposure; and (iv) laboratory smog chamber or flow reactor measurements in which oxidation chemistry is typically observed on timescales of minutes.…”

“…While the ecological implications of these observations have been the focus of much research, little work has focused on their atmospheric chemistry, despite the fact that many of these pesticides are transported through the atmosphere (Bedos et al, 2006;Coscollà et al, 2008;LeNoir et al, 1999;Majewski et al, 2014;Peck A.M, 2005;Rice et al, 2002;Sauret et al, 2000;Tabor, 1965;White et al, 2006). The chemical fate of compounds in the atmosphere -including oxidation, gas-particle partitioning, and surface deposition -ultimately controls their chemical identities and concentrations, and thus their impact on ecosystems and human health.…”

“…However, the environmental and health impacts of current-use pesticides and chemical parameters controlling their atmospheric fate are not well understood. These pesticides have been studied with regard to deposition and volatilization (Glotfelty et al, 1989;Rice et al, 2002), but the investigation of surface-atmosphere fluxes is limited by currently available instrumentation. In order to fully understand transport, concentrations, and chemical behavior in the atmosphere, in situ measurements of these pesticides need to be fast (< 1 h), sensitive, and selective in both the gas and particle phases (Farmer and Jimenez, 2010).…”