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°C, 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.