Penetration,Retention and Dissipation of Phosphine Under Different Fumigation Methods

Two fumigation methods:in a sealed warehouse(Method Ⅰ) and in a sealed plastic tent(Method Ⅱ) were compared.The phosphine(PH₃) concentration in the fumigation environment and tobacco case was determined.Combining with the relative indexes of PH₃ fumigation,the expectant effects of the two fumigation methods were analyzed by comparing the dynamic variation of PH₃ concentration inside and outside tobacco case.During the process for PH₃ dissipation,the PH₃ concentration inside tobacco case was measured to determine the time necessary for dissipation of PH₃ in a corrugated paperboard case with plastic liner.The results indicated that at the same dosage,Method Ⅱ was superior to Method Ⅰ in terms of the PH₃ concentration and retention duration of lethal concentration inside tobacco case,and expectant effect.When warehouse temperature was 20℃,the PH₃ concentration inside tobacco case in Method Ⅱ reached lethal concentration earlier than that in Method Ⅰ.The durations of fumigation process for plastic liner corrugated paperboard case of Method Ⅱ and Method Ⅰ were 9 to 10 and 11 to 12 days,respectively.In addition,Method Ⅱ reduced the total amount of phosphine application by 1/2 to 2/3 comparing with Method Ⅰ.