Phosphine Dosimeter Tubes A Alternate Approach for Fumigation Monitoring

摘要

To ascertain the adequacy of fumigation as well as to comply with the regulatory norms one has to monitor the phosphine concentration from the beginning to the end of fumigation which can last five to seven days. When aluminium phosphide tablets are used in an enclosure to generate phosphine the phosphine concentration starts building up from zero and reaches a maximum and starts declining from the peak value with time. To calculate the total phosphine dose（which is the most important parameter)received by the food grains, it is necessary to make several measurements during the entire period of fumigation. The phosphine dose is then determined by by calculating the area under the curve phosphine concentration v/s time. As an alternative to making several measurements for measuring the total dose,we have developed a phosphine dosimeter tube, which does the same job with a single measurement. For this purpose, a calibrated freshly opened phosphine dosimeter tube is kept at a suitable place inside the enclosure at the beginning and the phosphine dosage in ppm h is read at the end of fumigation on the dosimeter scale. The total phosphine dosage received by the food commodities is governed by the phosphine loss due to leaky enclosures,the amount of aluminium phosphide used,its quality,and the total time of exposure. Hence the total dosage measured on the dosimeter tells about the adequacy or other dosage related factors of fumigation and can throw light on the underlying cause for the eventual failure of a fumigation like substandard amount of aluminium phosphide tablets, leaky enclosure, or inadequate time of exposure etc. The paper will describe the method of calibration of dosimeter tubes and their various uses in fumigation experiments.