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Title: Effects of soil fumigants on methanotrophic activity

Author
item Spokas, Kurt
item KING, JENNIFER - UNIV. OF MN
item Wang, Dong
item Schneider, Sharon

Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2007
Publication Date: 11/16/2007
Citation: Spokas, K.A., King, J., Wang, D., Papiernik, S.K. 2007. Effects of soil fumigants on methanotrophic activity. Atmospheric Environment. 41:8150-8162.

Interpretive Summary: The slow down in the concentration growth of atmospheric methane is the result of several measures that have been taken over the last decades. Reduction in methane (CH4) oxidation rates have already been observed for a variety of agronomic practices, but effects of soil fumigation on CH4 oxidizing bacteria have not been investigated. Fumigation is a common practice in agricultural crop and nursery seedling protection. Soils from various agricultural experiment stations, forest nurseries, and a landfill were evaluated for effects of three soil fumigants on CH4 oxidation capacities. All three fumigants evaluated significantly reduced CH4 oxidation rates in historically non-fumigated soils. Chloropicrin universally decreased oxidation capacity regardless of fumigation history. These results support the conclusion that CH4 oxidation effects are fumigant specific and prior fumigation history plays a vital role in determining the impact on CH4 oxidizer community. This research benefits all of society, since it is vital to document the impacts of human activity to this biological sink for methane in soils. The soil bacteria responsible for oxidizing methane are the only known biological sinks for atmospheric methane. This research documents the impacts to these bacteria and thereby creates the foundation for examining better soil fumigation practices to minimize this impact. Without this sink, atmospheric methane levels could potentially increase.

Technical Abstract: Negative impacts on methane (CH4) oxidation capacity have already been observed for a variety of agronomic practices, but effect of soil fumigation on CH4 oxidation has not been investigated. Fumigation is a common practice in agricultural crop and nursery seedling protection. Soils from various agricultural experiment stations, forest nurseries, and a landfill were evaluated for effects of 1,3-dichloropropene (1,3-D), methyl isothiocyanate (MITC), and chloropicrin (CP) on CH4 oxidation capacities. All three fumigants significantly reduced CH4 oxidation rates in historically non-fumigated soils. 1,3-D enhanced CH4 oxidation in three out of five previously fumigated soils and MITC increased CH4 oxidation rates in all historically MITC fumigated soils compared to controls. CP universally decreased oxidation capacity regardless of fumigation history. These results support the conclusion that CH4 oxidation effects are fumigant specific and prior fumigation history plays a vital role in determining the impact on CH4 oxidizer community functionality, which may have implications on the global CH4 cycle.