SURFACE CONCENTRATION OF CHLORPYRIFOS EVALUATED BY ELECTROMAGNETIC DISCHARGE IMAGING TECHNIQUE

Image analysis is used in conjunction with the Electromagnetic Dischar ge Imaging (EDI) technique to evaluate the surface concentration and t he characteristic discharge intensity of chlorpyrifos. Nearly identica l surface condition of gypsum specimens were subjected to chlorpyrifos solutions of various concentrations. The EDI discharges were then app lied to detect the changes. Experimental results show that the EDI dis charge intensity increases with increasing chlorpyrifos concentration up to 0.4% where a saturation limit is reached. Since the changes of t he ionization property and the dielectric property caused by the conce ntration variation have opposing effects on the EDI discharge intensit y, saturation by the foregoing two effects occur at high concentration . Further analysis shows that three characteristic gray levels were fo und in the gray-level distribution curve for each chlorpyrifos concent ration of 0.1%, 0.4%, and 1.6%. These characteristic gray levels can b e used to rank concentration of chlorpyrifos. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.