A New Approach to Quantify Herbicide Volatility

Abstract

Herbicide active ingredients, formulation type, ambient temperature, and humidity can influence volatility. A method was developed using volatility chambers to compare relative volatility of different synthetic auxin herbicide formulations in controlled environments. 2,4-D or dicamba acid vapors emanating after application were captured in air-sampling tubes at 24, 48, 72, and 96 h after herbicide application. The 2,4-D or dicamba was extracted from sample tubes and quantified using liquid chromatography and tandem mass spectrometry. Volatility from 2,4-D dimethylamine (DMA) was determined to be greater than that of 2,4-D choline in chambers where temperatures were held at 30 or 40 C and relative humidity (RH) was 20% or 50%. Air concentration of 2,4-D DMA was 0.399 µg m−3at 40 C and 20% RH compared with 0.005 µg m−3for 2,4-D choline at the same temperature and humidity at 24 h after application. Volatility from 2,4-D DMA and 2,4-D choline increased as temperature increased from 30 to 40 C. However, volatility from 2,4-D choline was lower than observed from 2,4-D DMA. Volatility from 2,4-D choline at 40 C increased from 0.00458 to 0.0263 µg m−3and from 0.00341 to 0.025 µg m−3when humidity increased from 20% to 50% at 72 and 96 h after treatment, respectively, whereas, volatility from 2,4-D DMA tended to be higher at 20% RH compared with 50% RH. Air concentration of dicamba diglycolamine was similar at all time points when measured at 40 C and 20% RH. By 96 h after treatment, there was a trend for lower air concentration of dicamba compared with earlier timings. This method using volatility chambers provided good repeatability with low variability across replications, experiments, and herbicides.

Physicochemical properties, droplet size and volatility of dicamba with herbicides and adjuvants on tank-mixture

“…It has been observed, for example, that inside hermetically sealed environments, relative humidity can rapidly increase, reaching up to 90%, and may affect the gas exchange dynamics and respiration in plants 41 . Furthermore, it has been shown that concentration of dicamba suspended in air decreases as relative humidity raises from 20 to 50% during 48 h after application 18 .

Figure 6 Dicamba injury symptoms observed in exposed soybean plants.

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“…A new methodology was proposed to evaluate herbicide volatility based on methodology recommendations by Reynolds 17 and adaptations described by Ouse et al 18 . Herbicides and adjuvant tank-mixtures combinations (Table 1 ) were applied using the MUG 11003 nozzle.…”

Dicamba volatility in humidomes as affected by temperature and herbicide treatment

“…Others have also employed plant bioassays as indicators of dicamba activity (Egan and Mortensen 2012;Penner and Michael 2014;Sciumbato et al 2004). Although the sensitivity of these bioassays is adequate, a quantitative assessment via air sampling followed by chemical extraction and analysis may yield more direct indications of herbicide behavior (Mueller et al 2013;Mueller 2015;Ouse et al 2018). This research aimed to examine the effect of temperature, dicamba formulation, and glyphosate addition on dicamba concentrations.…”

Evaluation of a Stable Isotope-Based Direct Quantification Method for Dicamba Analysis from Air and Water Using Single-Quadrupole LC–MS

“…To fully evaluate air sample extraction, we performed vapor chamber experiments using glass plates ( Figure 4 ) similar to those conducted with plants in other herbicide volatility studies [ 6 , 23 ]. Glass plates with a surface area of 190 cm 2 were sprayed with selected dicamba formulation using a single-nozzle, track-mounted research sprayer calibrated to deliver 140 L ha −1 per pass using a Turbo Teejet Induction nozzle (TTI 11002) (Teejet Technologies, Springfield, IL, USA).…”

“…Sub-picogram level detection of dicamba from water was also reported using paired-ion electrospray ionization (ESI) mass spectrometry [ 14 ]. Furthermore, several MS-based dicamba analytical methods have been reported for food items [ 17 , 18 ], water and agricultural cleanouts [ 13 , 14 , 16 , 19 , 20 , 21 , 22 ], air samplers [ 6 , 23 , 24 ], crops like apple, pepper, brown rice, and soybean [ 25 ], tobacco [ 26 ], barley [ 27 ], soybean [ 28 ], rice [ 29 ], as well as in other agricultural commodities [ 30 ]. Most of these protocols rely on triple quadrupole and/or higher resolution MS instruments, although quantification procedures using LC–diode array detection (DAD) [ 24 ] and single-quadrupole LC–MS [ 6 , 31 ] have been reported.…”