Bias caused by water adsorption in hourly PM measurements
2017
Beta-attenuation monitors are used worldwide to
monitor PM mass concentration with high temporal resolution.
Hourly PM10 and PM2.5 dry mass concentrations are
publicly available with the tacit assumption that water is effectively
removed prior to the measurement. However, as
both the filter material of the monitor and the aerosol particles
are capable of retaining a significant amount of water
even at low relative humidities, the basic assumption may
not be valid, resulting in significant bias in reported PM10
and PM2.5 concentrations. Here we show that in PM10 measurement,
particle-free air can produce apparent hourly average
PM concentrations in the range of −13–+21 µgm−3 under
conditions of fluctuating relative humidity. Positive and
negative apparent readings are observed with increasing and
decreasing relative humidities, respectively. Similar phenomena
have been observed when the instrument filter was previously
loaded with atmospheric aerosol. As a result the potential
measurement biases in hourly readings arising from the
interaction with water may be in the range of −53...+69 %.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
30
References
8
Citations
NaN
KQI