Short name:
GTHOS: OH

Full name:
Ground-based Tropospheric Hydrogen Oxides Sensor : Reporting OH

What is being measured:

Sampling Protocol:
Online

Manufacturer:
Custom

Model:
Custom

Instrument year :
None specified

Data recording software:
Inquire with PI

Data analysis software:
Inquire with PI

Raw data time resolution:
Inquire with PI

Analysis data averaging:
10 minute

Detection limit:
pptv

Sensitivity to temperature (and correction method, if applicable): :

Sensitivity to relative humidity (and correction method, if applicable): :

Sampling method:
Direct Sampling

Sample preparation method:
Chemical zeroing with C3F6 for some measurements to remove OH interference

Sample residence time (chamber to instrument) (seconds):

Length of tubing (cm):
0.03

Instrument flow rate:
6

Tubing inner diameter:

Tubing material:
Stainless Steel

Chemical identification method:
The instrument uses ultraviolet laser induced fluorescence (LIF) to detect OH in air that is pulled by a vacuum pumpthrough a small inlet into a low pressure detection chamber; HO2 is detected by reacting it with NO to form OH, which is detected by LIF in a second detection chamber

Data analysis method:
Inquire with PI

Quantification method:
Absolute fluorescence cross sections measured at 308 nm

Calibration method:
In the calibration, equal amounts of OH and HO2ranging from 0.15 pptv to 100 pptv are produced via photolysis of watervapor by the 185 nm emission from a low-pressure Hg lamp. Estimated absolute uncertainty at the 2σ confidence level is ± 32% for both OH and HO2.

Calibration drift estimate:
Low (on the order of weeks)

Calibration schedule:
As Needed

Uncertainty estimation method:
Inquire with PI

Known interferences:
In biogenic areas, there may be an interference in the OH channel if no chemical zeroing is done

Link to supplemental information:
Mao, J., Ren, X., Zhang, L., Van Duin, D. M., Cohen, R. C., Park, J.-H., Goldstein, A. H., Paulot, F., Beaver, M. R., Crounse, J. D., Wennberg, P. O., DiGangi, J. P., Henry, S. B., Keutsch, F. N., Park, C., Schade, G. W., Wolfe, G. M., Thornton, J. A., and Brune, W. H.: Insights into hydroxyl measurements and atmospheric oxidation in a California forest, Atmos. Chem. Phys., 12, 8009-8020, https://doi.org/10.5194/acp-12-8009-2012, 2012.

Additional notes:

Measurement uncertainty:

Measurement units: