Environmental Project's Achievements Reports Query System

Accuracy Estimate of Air Pollutant Automatic Monitor Measurement Technology

Absrtact	This research investigates the accuracy differences between the automatic monitoring methods of PM10 (β-gauge and TEOM) in ambient air and NOx ( NDIR and CLD) inside the stack. The estimated items in laboratory include the principles, the ranges of monitoring concentrations, interferences, the detection limits and the response times. Field samplings work at the same time to compare the factual differences in monitoring data for the above automatic monitoring methods of PM10 and NOx. We summarize the fruitful results as following: On the part of PM10, the results of uniformity test showed that the β-count increased with decreasing uniformity, indicating that the β-gauge might underestimate when non-uniform aerosol deposition occurred. From the perspective of response time that Wedding took longest (3 hours) to reach stable concentration, while VEREWA and TEOM can attain stable concentrations within one hour. In terms of accuracy, TEOM has the best agreement with the filter method. The relative humidity had no obvious effect on the performance of these real time instruments. The mass attenuation coefficient was found to decrease with increasing Z/A value, indicating a strong material dependence. The test results of Sample Equilibration System revealed that Nafion removed the water effectively. In the ambient RH range from 20% to 90%, moisture could be maintained around 20% in the sensing unit after the ambient air passing through the SES. On the part of NOx, the measured results of the detection limits for the automatic monitoring methods of NDIR and CLD were 1.4 and 8.6 ppm, respectively. The results of interfered tests by CO2 showed that NO monitoring values both increased with increasing CO2 concentrations, indicating that NO monitoring values of NDIR and CLD inside the stack might overestimate when the additive interference occurred, CO2 concentrations more than 5% especially. On the other hand, the additive interference of NH3 were obvious and non-linear in ambient NO monitoring. The critical concentration was about 20 ppb.
Keyword	air pollutant,automatic monitor,monitoring technology,accuracy

Absrtact

This research investigates the accuracy differences between the automatic monitoring methods of PM10 (β-gauge and TEOM) in ambient air and NOx ( NDIR and CLD) inside the stack. The estimated items in laboratory include the principles, the ranges of monitoring concentrations, interferences, the detection limits and the response times. Field samplings work at the same time to compare the factual differences in monitoring data for the above automatic monitoring methods of PM10 and NOx. We summarize the fruitful results as following: On the part of PM10, the results of uniformity test showed that the β-count increased with decreasing uniformity, indicating that the β-gauge might underestimate when non-uniform aerosol deposition occurred. From the perspective of response time that Wedding took longest (3 hours) to reach stable concentration, while VEREWA and TEOM can attain stable concentrations within one hour. In terms of accuracy, TEOM has the best agreement with the filter method. The relative humidity had no obvious effect on the performance of these real time instruments. The mass attenuation coefficient was found to decrease with increasing Z/A value, indicating a strong material dependence. The test results of Sample Equilibration System revealed that Nafion removed the water effectively. In the ambient RH range from 20% to 90%, moisture could be maintained around 20% in the sensing unit after the ambient air passing through the SES. On the part of NOx, the measured results of the detection limits for the automatic monitoring methods of NDIR and CLD were 1.4 and 8.6 ppm, respectively. The results of interfered tests by CO2 showed that NO monitoring values both increased with increasing CO2 concentrations, indicating that NO monitoring values of NDIR and CLD inside the stack might overestimate when the additive interference occurred, CO2 concentrations more than 5% especially. On the other hand, the additive interference of NH3 were obvious and non-linear in ambient NO monitoring. The critical concentration was about 20 ppb.

Keyword

air pollutant,automatic monitor,monitoring technology,accuracy