Abstract
A SIMPLE INEXPENSIVE METHOD IS DESCRIBED FOR DETERMINING CONCENTRATIONS OF TOTAL MERCURY IN THE ATMOSPHERE. MERCURY AND ITS COMPOUNDS WERE EFFECTIVELY COLLECTED BY PASSING AMBIENT AIR THROUGH ACTIVATED CHARCOAL CONTAINED IN VYCOR TUBES. THE CHARCOAL TUBES WERE PREPARED BY HEATING UNDER NITROGEN TO ACTIVATE THE CHARCOAL AND TO REMOVE IMPURITIES. IMMEDIATELY AFTER CLEANING, THE TUBES WERE SEALED WITH BALL JOINTS UNTIL READY FOR SAMPLE COLLECTION TO PREVENT CONTAMINATION. AFTER SAMPLING, THE TUBES WERE RESEALED FOR TRANSPORT TO THE LABORATORY WHERE THEY BECAME AN INTEGRAL PART OF THE ANALYTICAL GAS TRAIN. THE MERCURY AND ITS COMPOUNDS WERE VAPORIZED BY HEATING UNDER A STREAM OF NITROGEN AND CARRIED TO A THERMAL REACTOR, WHICH CONVERTED THE COMPOUNDS TO THE ELEMENTAL STATE. ELEMENTAL MERCURY THEN AMALGAMATED ON SILVER, ALLOWING POTENTIAL INTERFERENCES TO PASS THROUGH THE ABSORPTION CELL. THE SILVER AMALGAM WAS HEATED TO 300C TO GIVE ABSORPTION PEAKS IN THE ULTRAVIOLET AT 253.7 NM THAT WERE SHARP AND REPRODUCIBLE. THE METHOD WAS TESTED WITH SIMULATED AND REAL ATMOSPHERES UNDER FIELD CONDITIONS. PRECISION AND ACCURACY OF THE METHOD WAS GREATER THAN 95% WITHIN THE RANGE OF 0.15 TO 1.5 MICROGRAMS/CU M. OUTSIDE THIS RANGE, THE ERROR WOULD BE GREATER; HOWEVER, THE DYNAMIC RANGE MAY BE SHIFTED UPWARD OR DOWNWARD BY CHANGING SAMPLING RATES, SAMPLE TIMES, OR CELL PATH AND BY COMBINATION OF THESE VARIABLES. (JERNIGAN-VANDERBILT)