NOAA PMEL Aerosol Chemistry Station Data
Contact person:  Trish Quinn, patricia.k.quinn@noaa.gov

Station ID
BRW = Barrow, AK (71.3N, 156.6W)

Submicron and supermicron samples are collected at sample periods that change with season and aerosol loading. 

The submicron - supermicron split is made with a Berner-type cascade impactor having a 
D50,aero of 1.0 um at the RH of the sample stream. Hence, the submicron data are for 
particle sizes < 1.0 um and supermicron data are for particle sizes > 1.0 um and < 10 um.
The RH of the sampled aerosol is < 40% at all stations.

All samples have been analyzed by ion chromatography for Cl-, NO3-, SO4-2, Na+, NH4+, K+, Mg2+, and Ca+2, MSA-, Br-, and oxalate

Samples also are analyzed for total mass by gravimetric analysis at 55 +/- 5% RH.
All ion and mass concentrations are given in ug/m3 at STP.

More details of the sampling and IC and gravimetric analysis methods can be found in
Quinn et al., J. Geophys. Res., 105, 6785 - 6805, 2000.

Barrow submicron samples were analyzed by XRF for Mg, Al, SI, P, S, Cl, 
K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Br, Sr, and Pb.  Element concentrations are given 
in ug/m3 at STP. Error for the XRF data, defined as the square root of the total uncertainty 
based on regression and counting are given in ng/cm2.  Minimum detection limit (MDL), 
defined as 3 times the square root of the background intensity measured from a standard 
of known concentration is given in ng/cm2.  The XRF filter area is 11.3 cm2 (area correction already applied to the mass concnetrations). XRF is measured only during high-frequency sampling period (January-April) 

More details of the XRF analysis can be found in Buck, N.J., P.M. Barrett, P.L. Morton, 
W.M. Landing, and J.A. Resing (2021): Energy dispersive X-ray fluorescence methodology 
and analysis of suspended particulate matter in seawater for trace element compositions 
and an intercomparison with high-resolution inductively coupled plasma-mass spectrometry.
Limnol. Oceanogr. Methods, 19(6), 401-415, doi: 10.1002/lom3.10433

There are two separate files of data for each station: one for submicron data
and one for supermicron data.

Flags used in the files are:

V = Volume zero or unknown.
NS = Filter not sampled.
BDL = Below detection limit.
NA = Data not available.
Filters 2 through 8 = submicron filter.
Filter S = supermicron filter.

Detection limit values prior to 2015 were (ug/m3)

Mass = 0.02
Na = 0.0002
NH4 = 0.0001
K = 0.0001
Mg = 0.0001
Ca = 0.0001
MSA = 0.0001
Cl = 0.0002
Br = 0.0001
NO3 = 0.0001
SO4 = 0.0001
Oxalate = 0.0001

Beginning in 2015 the blank value and 2 sigma of the average blank are given for each sample.  
Flags are used to indicate missing data (M), samples that do not exceed the blank value plus 
2 standard deviations of the average blank (BDL), and samples with volumes less than 1 m3 (V).
The Barrow data can be downloaded in many formats from the PMEL ERDDAP server:
https://data.pmel.noaa.gov/pmel/erddap/tabledap/

In the above ERDDAP server the Aerosol Chemistry Station Data has the following "Titles",
Long-term Air Chemistry Monitoring Experiment-Submicron
Long-term Air Chemistry Monitoring Experiment-Supermicron