Real-Time Measurement of Herbicides in the Atmosphere: A Case Study of MCPA and 2,4-D during Field Application

Abstract

Atmospheric sources of herbicides enable short- and long-range transport of these compounds to off-target areas but the concentrations and mechanisms are poorly understood due, in part, to the challenge of detecting these compounds in the atmosphere. We present chemical ionization time-of-flight mass spectrometry as a sensitive, real-time technique to detect chlorinated phenoxy acid herbicides in the atmosphere, using measurements during and after application over a field at Colorado State University as a case study. Gas-phase 2,4-dichlorophenoxyacetic acid (2,4-D) mixing ratios were greatest during application (up to 20 pptv), consistent with rapid volatilization from spray droplets. In contrast, atmospheric concentrations of 2-methyl-4-chlorophenoxyacetic acid (MCPA) increased for several hours after the initial application, indicative of a slower source than 2,4-D. The maximum observed gas-phase MCPA was 60 pptv, consistent with a post-application volatilization source to the atmosphere. Exposure to applied pesticides in the gas-phase can thus occur both during and at least several hours after application. Spray droplet volatilization and direct volatilization from surfaces may both contribute pesticides to the atmosphere, enabling pesticide transport to off-target and remote regions.

Herbicide Drift from Genetically Engineered Herbicide-Tolerant Crops

“…These tools include the aerosol mass spectrometer (AMS), to assess speciation of major organic and inorganic particle components, and the thermal desorption chemical ionization mass spectrometer (TDCIMS), to assess the composition of new particles . Gas-phase species may be investigated by various CIMS − methods such as the proton transfer reaction mass spectrometer (PTRMS) and Vocus PTR-ToF . Furthermore, quantification of organic molecules in both gas and particle fractions can be performed simultaneously by the semivolatile thermal desorption aerosol gas chromatograph (SV-TAG), , a type of in situ GC/MS system. − These methods are also suited to track the multiphase oxidative evolution of both the herbicides and their formulation components, including formation of reaction products that may be toxic and/or contribute to the generation of secondary organic aerosols. , …”

Adsorption of Phenoxyacetic Herbicides from Water on Carbonaceous and Non-Carbonaceous Adsorbents

“…The atmospheric lifetime of a given herbicide depends on its structure and the rate of the chemical and physical processes it undergoes. Depending on the weather conditions and herbicide form (vapour, droplets, and suspension with soil and dust), it may be transported in the air for a certain distance from the application location [ 37 ].…”

Snails as Temporal Biomonitors of the Occurrence and Distribution of Pesticides in an Apple Orchard

“…Atmospheric pesticide measurements could be conducted via continuous monitoring programs, which allow real-time continuous measurement of the pesticides' concentration in the atmosphere over a period of time [26], or by integrated monitoring programs where pesticides in the air are accumulated on a collecting media for later analyses [25]. While continuous monitoring programs allow fast and direct measurement of pesticides in the atmosphere, their use is still limited and atmospheric pesticide measurements are mainly conducted using integrated measurement approaches [27]. These integrative approaches rely either on an active or a passive sampling technique.…”