Volume 7, Issue 7 (July 2010)
Simulating and Characterizing Agricultural Ground Applications for Soil VOC Deposition Studies
Reactive volatile organic compounds (VOCs) 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. The United States is one of the most agriculturally productive countries in the world due in part to the use of chemical pesticides that consist of active ingredients that are typically non-volatile or semi-VOCs and inert ingredients such as solvents, emulsifiers, and diluents that may also be volatile. Presently, the VOC determination of emission factors from agricultural pesticide applications assumes 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 VOC 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 with 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.