Application rate affects the degradation rate and hence emissions of chloropicrin in soil

• Published in: The Science of the total environment Vol. 622-623; pp. 764 - 769
• Main Authors: Ashworth, Daniel J., Yates, Scott R., Stanghellini, Mike, van Wesenbeeck, Ian J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-05-2018
• Subjects: Buffer zones; Fumigants; Fumigation; Half-life; Soil columns; Volatilization; Buffer zones; Fumigation; Half-life; Fumigants; Soil columns; Volatilization
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.12.060

Increasingly stringent regulations to control soil-air emissions of soil fumigants has led to much research effort aimed at reducing emission potential. Using laboratory soil columns, we aimed to investigate the relationship between chloropicrin (CP) application rate and its emissions from soil across a wide range of CP applications (equivalent to 56–392kgha−1). In contrast to the known behavior of other fumigants, total emission percentages were strongly and positively related to application rate (i.e., initial mass), ranging from 4 to 34% across the application rate range. When combined, data from a previous study and the present study showed good overall comparability in terms of CP application rate vs. emission percentage, yielding a second-order polynomial relationship with an R2 value of 0.93 (n=12). The study revealed that mass losses of CP were strongly disproportional to application rate, also showing a polynomial relationship. Based on degradation studies, we consider that a shorter half-life (faster degradation) at lower application rates limited the amount of CP available for emission. The non-linear relationship between CP application rate and CP emissions (both as % of that applied and as total mass) suggests that low application rates likely lead to disproportionally low emission losses compared with higher application rates; such a relationship could be taken into account when assessing/mitigating risk, e.g., in the setting of buffer zone distances.
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•Widespread use of agricultural fumigants is a concern in relation to air quality.•Soil columns were used to measure fluxes of chloropicrin from soil to air.•Emissions percentage of chloropicrin was positively related to application rate.•Chloropicrin was more rapidly degraded at low application rates.•The results may have implications for the setting of farm buffer zone sizes.