Replicated flux measurements of 1,3-dichloropropene from a bare soil under field conditions

Authors: ASHWORTH, DANIEL - University Of California; Yates, Scott; Anderson, Raymond - Ray; VAN WESENBEECK, IAN - Dow Agrosciences; Sangster, Jodi; MA, LI - University Of California

Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2018
Publication Date: 7/30/2018
Publication URL: https://handle.nal.usda.gov/10113/6125065
Citation: Ashworth, D.J., Yates, S.R., Anderson, R.G., Van Wesenbeeck, I.J., Sangster, J.L., Ma, L. 2018. Replicated flux measurements of 1,3-dichloropropene from a bare soil under field conditions. Atmospheric Environment. 191:19-26. https://doi.org/10.1016/j.atmosenv.2018.07.049.
DOI: https://doi.org/10.1016/j.atmosenv.2018.07.049

Interpretive Summary: Agricultural fumigants are extremely useful for controlling plant pests in soil, especially prior to the planting of vegetable crops of high value in areas such as California. However, despite their benefits in improving crop yields, they can be harmful to humans and the environment as they are released as a gas from the soil into the atmosphere. Various experiments have quantified the extent of these emissions and studied approaches designed to limit their release from the soil. Under field conditions, these experiments are complex and expensive; therefore, they are usually not conducted using replication. This is a major drawback as replication is a fundamental aspect of experimental design in relation to both precision and accuracy of the data. In this experiment, we conducted a field experiment with duplicate flux measurements of 1,3-dichloropropene (a common fumigant). We found that the both the flux over time and the total emissions loss were highly replicable across three calculation methods; at least as replicable as fluxes observed in highly controlled laboratory soil column experiments. This finding is useful for state regulators conducting risk assessments of fumigant use as it allows them a greater level of confidence in their predictions.

Technical Abstract: Field experiments offer the most acceptable approach to quantifying agricultural fumigant emissions but there is an absence of replicated field data in reported literature. Air concentration profiles of 1,3-dichloropropene (1,3-D) were determined on duplicate masts above the center of a treated field over 14 days. Meteorological parameters were also measured. Three meteorological approaches were then used to determine the total and flux density emissions of 1,3-D. Across the three calculation methods, the averages of the duplicated measurements showed total emission losses of cis 1,3-D ranging from 27% to 36% and of trans 1,3-D ranging from 18% to 24%. The replicate measurements differed by between 1.6 and 7.7 percentage points, which we consider to be excellent replicability. Flux densities over time showed maximum emissions during the first nighttime and early morning of the day following application. A general declining trend in emission fluxes was accompanied by nighttime peaks. Flux density curves during the experiment showed excellent agreement between replicates, with linear regression of the two data sets yielding r2 values of 0.95–0.98 and slopes of 1.01–1.17. To our knowledge, this is the first time that replicated fumigant fluxes have been reported. The high degree of replicability indicates the robustness of the approaches and lends credence to previous non-replicated flux data.