COMPARISON OF ENHANCED AND ROUTINE METHODS FOR MEASURING AMBIENT LOW-LEVEL SULFUR-DIOXIDE

The work reported here was designed to determine: the adequacy of a conventional monitoring method for measuring low-level (<20 ppbv) ambient sulfur dioxide; and the measurement improvement obtained with an enhanced monitoring method. Two analyses were used. In the first analysis, two different continuous monitoring methods were evaluated against an independent measure of ambient sulfur dioxide concentration - an integrated filterpack technique. In the second analysis, hourly average concentrations from the two methods were compared directly. Routine continuous monitoring methods give good agreement at low ambient sulfur dioxide concentration levels in the range of 2 to 20 ppbv. However, an instrument with a manufacturer reported MDL of 0.6 ppbv and a more demanding data reduction and processing scheme (e.g., chemical zero checks at six-hour intervals and daily quality assurance span checks at 0, 3, and 20 ppbv) produced an enhanced sensitivity level of 0.2 ppbv.