Thesis
Assessing near-field naturally occurring isothiocyanates emissions after mustard green manure cover crop incorporation
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/104944
Abstract
An assessment of near-field naturally occurring isothiocyanate air emissions was conducted in Benton County, Washington, in the fall of 2008. The purpose of the study was to assess and quantify selected natural isothiocyanate (NITC) compounds in emissions from green manure soil amendments and to develop a method to detect and quantify multiple NITCs in ambient air for human inhalation risk assessment. An analytical method was developed specific to three selected NITC compounds commonly known to be associated with the mustard green manure cover crop: allyl-, benzyl-, and 2-phenethyl isothiocyanate. Air samples were taken in and around a crop circle sown with high biomass-producing brassicas typically used in the Columbia Basin of Washington state before, during and after cover crop incorporation. A total of eight discrete intervals of approximately four hours each were evaluated for assessing potential human inhalation exposure. Emissions of the selected NITCs were quantified or detected from samples taken before and during cover crop incorporation and when field operations ceased. Allyl isothiocyanate and benzyl isothiocyanate concentrations were observed during the period of active cover crop incorporation, while phenethyl isothiocyanates were detected below the analytical method's Limit of Quantification (LOQ). The selected NITCs were not detected during the pre-incorporation period or on post green manure incorporation days 1 through 3. On the fourth day, allyl isothiocyanate was again observed at levels above LOQ. This observation occurred on a day with light precipitation and suggests increased surface moisture may have enhanced formation and emission of NITCs from previously unhydrolyzed glucosinolates residing on the incorporated land surface. We found the time weighted average (TWA) amounts of allyl- were greater than the benzyl- and phenethyl isothiocyanates by an order of magnitude. The maximum observed TWA air concentration for the allyl-, benzyl-, and phenethyl isothiocynanates were observed during soil incorporation and were respectively 47, 1.0, and 0.1 ppb. Values for acute or chronic inhalation exposure for these NITCs are not available in public databases.
Metrics
2 File views/ downloads
15 Record Views
Details
- Title
- Assessing near-field naturally occurring isothiocyanates emissions after mustard green manure cover crop incorporation
- Creators
- Donna M. Trott
- Contributors
- Vincent R. Hebert (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525119801842
- Language
- English
- Resource Type
- Thesis