A Comparison of PM10 Monitoring Methods in New Zealand
There are a number of methods which comply with the requirements for monitoring PM10 under New Zealand’s Air Quality National Environmental Standards. These include gravimetric and equivalent methods such as the Tapered Oscillating Element Microbalance (TEOM), Filter Dynamics Measurement System (FDMS-TEOM) and Beta Attenuation Monitor (BAM).
The study pooled a New Zealand wide data set of co-located gravimetric and equivalent PM10 measurements. Over 3000 data points were collected from six environmental agencies within NZ. The data came from a total of 13 sites, located between Auckland and South Canterbury. Comparisons between the gravimetric and equivalent PM10 data were undertaken using quantitative methods.
The TEOM and BAM are USEPA equivalent-designated methods and are both defined as suitable for monitoring PM10 under the NES. However the analysis undertaken in this study suggests the measurements produced by the TEOM(40) and BAM are not equivalent in a quantitative sense to measurements obtained using gravimetric methods. At higher concentrations (>100 µgm-3) the TEOM and BAM under measured by 28 and 12% respectively. The TEOM-FDMS data is much closer to being quantitatively equivalent to measurements obtained using gravimetric methods.
To obtain a gravimetric equivalent measurement from TEOM or BAM data, it is necessary to apply an adjustment factor. Regression Tree and Multi Linear Regression models are used to determine adjustment factors. Both models improve the relationship between TEOM(40) and gravimetric data and significantly reduce both under-measurement.
The influences of season, location, site type and meteorology on the performance of the TEOM-FDMS, TEOM and BAM are investigated.