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Title: Simulating and characterizing agricultural ground applications for soil VOC deposition studies

Author
item Fritz, Bradley - Brad
item Hoffmann, Wesley
item ROHDE, ARLEAN - Exxonmobil
item WARREN, CHRISTOPHER - Exxonmobil
item FAULKNER, WILLIAM - Texas A&M University

Submitted to: Journal of ASTM International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2010
Publication Date: 7/23/2010
Citation: Fritz, B.K., Hoffmann, W.C., Rohde, A., Warren, C., Faulkner, W. 2010. Simulating and characterizing agricultural ground applications for soil VOC deposition studies. Journal of ASTM International. 7(7):Paper ID JAI102776.

Interpretive Summary: The relationship between applied agricultural pesticides and the emissions of volatile organic compounds is not well understood. Presently, regulations for applying agro-chemical products in controlled areas are based on an assumption that all of the volatile compounds that comprise a spray formulation volatilize and contribute to the formation of ozone. However, there is little or no data supporting this assumption due to the difficulty of characterizing and sampling deposition and loss of applied sprays in the field. A laboratory spray table was used to mimic agricultural ground application spray rates and spray droplet sizes which were applied over sample boxes containing a specified test soil. Deposition of the applied spray was mapped over the soil surface and soil samples were collected for further analysis of volatile organic compound concentrations. The spray table methodology allows for precise applications of spray formulations at specified spray rates and droplet sizes to better understand the link between applied agricultural sprays and the emission of volatile compounds.

Technical Abstract: Reactive volatile organic compounds (RVOCs) play a major role in the formation of photochemical oxidants in the atmosphere by reacting with oxides of nitrogen and solar ultraviolet energy producing ozone which is a criteria pollutant regulated under the National Ambient Air Quality Standards (NAAQS). The United States is one of the most agriculturally productive countries in the world due, in part, to the use of chemical pesticides which consist of active ingredients that are typically non-volatile or semi-volatile organic compounds (SVOCs), and inert ingredients such as solvents, emulsifiers, and diluents that may also be volatile. Presently, VOC determination of emission factors from agricultural pesticide applications assume that all of the inert VOC ingredients volatilize. This research focuses on the development of a laboratory methodology for applying agricultural spray formulations in accurate and measurable levels to support volatile organic compound deposition onto and loss from soil surfaces. Adapting a laboratory spray table system with a modified spray and deposition sampling scheme resulted in repeatable spray applications with the deposition pattern being mapped across the treatment area. These mapped deposition values allow for measurements from soil samples to be correlated to actual spray deposition. This methodology provides for a rapid and repeatable means for surveying VOC deposition and losses from a variety of spray formulations under varying spray rates and spray droplet sizes.