Degradation and volatilization of the fumigant chloropicrin after soil treatment

Chloropicrin (CP) is used in fumigation of soil-borne pests. Because of its high volatility and toxicity, atmospheric emission of CP during soil application may become a source of air pollution. We investigated degradation of CP in three different soils as a function of soil temperature and moisture conditions, and evaluated its volatilization against methyl bromide (MeBr) from packed soil columns. Chloropicrin degraded much faster than MeBr in the same soil, mainly via microbial degradation. Degradation of CP accelerated as soil temperature increased, but was relatively independent of changes in soil moisture. When the soil surface was uncovered, overall volatilization loss of CP was similar to that of MeBr. Covering the soil surface with a polyethylene or high-barrier film was much more effective in reducing volatilization of CP than MeBr. Therefore, surface covers may be used in sensitive areas to reduce human exposure to CP.