Low-Volume Filter Pack Air Chemistry Data Variable Descriptions With Units
- YEAR year during which sampling week ended
- MONTH month during which sampling week ended
- #WEEKS number of weeks included in calculation
- ACH mean air concentration of particulate H (ueq/m^3)
- ACCA mean air concentration of particulate Ca (ug/m^3)
- ACMG mean air concentration of particulate Mg (ug/m^3)
- ACNA mean air concentration of particulate Na (ug/m^3)
- ACK mean air concentration of particulate K (ug/m^3)
- ACNO3 mean air concentration of particulate NO3 (ug/m^3)
- ACSO4 mean air concentration of particulate SO4 (ug/m^3)
- ACCL mean air concentration of particulate Cl (ug/m^3)
- ACNH4 mean air concentration of particulate NH4 (ug/m^3)
- ACHNO3 mean air concentration of gaseous HNO3 (ug/m^3)
- ACSO2 total mean air concentration of gaseous SO2 (ug/m^3)
- VDSO2 mean deposition velocity for SO2 (cm/s)
- VDHNO3 mean deposition velocity for HNO3 (cm/s)
- VDFP mean deposition velocity for fine particles (cm/s)
- SO2FLUX total SO2 dry deposition for the month (mol/ha)
- HNO3FLUX total HNO3 dry deposition for the month (mol/ha)
- NO3FLUX total particulate NO3 dry deposition for the month (mol/ha)
- SO4FLUX total particulate SO4 dry deposition for the month (mol/ha)
- NH4FLUX total particulate NH4 dry deposition for the month (mol/ha)
Low-Volume Filter Pack Air chemistry instrument make, model and dates used
Pump: Gast, Inc. oil-less vacuum pump model 1031 (1988-1998), model 1531-107B-6288 (1998- present)
Mass Flow Controller: Tylan-Millipore model FC280V (1988-1998) FC2604S (1998-2002) Aalborg GFC17 (2002-present)
Low-Volume Filter Pack Air Chemistry data quality assurance and quality control parameters and methods
All filter packs and bottles are cleaned by rinsing in deionized water 7 times, allowing to soak overnight in deionized water, rinsing again 4 times in deionized water and finally either dried in a drying oven at no more than 60 degrees C or allowed to sit with caps loosened (bottles) until dry. Every 12 months a filter pack with a set of filters is exposed under a vacuum of 3.00 lpm for 3 minutes. The filter pack and filters are handled and analyzed as regularly exposed filters. This is to ensure that the sample handling procedures introduce no contamination.
When analytical results are received from the Cary Institute analytical lab, data are examined and checked using two methods. First, ion balances and ionic strength are calculated using the following equations:
Ion Balance = ((ANIONS - CATIONS)/((CATIONS+ANIONS)/2))*100;
Ion Strength = CATIONS + ANIONS;
Where:
Cations = CA/20 + MG/12 + NA/23 + K/39 + NH4/18 + HA;
Anions = NO3/62 + SO4/48 + CL/35.5;
And:
HA is teflon filter H+ conc (mg/l)
CA is teflon filter Ca concentration (mg/L)
MG is teflon filter Mg concentration (mg/L)
NA is teflon filter Na concentration (mg/L)
K is teflon filter K concentration (mg/L)
NO3 is teflon filter NO3 concentration (mg/L)
SO4 is teflon filter SO4 concentration (mg/L)
CL is teflon filter Cl concentration (mg/L)
NH4 is teflon filter NH4 concentration (mg/L)
HA is calculated as (10**PH)*1000, where PH = pH of teflon filter extractant.
Ion balances and ionic strength are examined and samples are considered for reanalysis if the following criteria are met:
| Ionic Strength (ueq) and | Ion Balance (%) |
| Less than 50 | greater than 40 |
| Between 50 and 100 | greater than 20 |
| Greater than 100 | greater than 10 |
The second quality control step is to examine time series graphs of sample concentrations for each analyte. If any samples are obvious outliers, they are considered for reanalysis.
Instrument notes including calibration schedule, malfunctions and repairs, new instrumentation, anecdotal information etc. can be made available on request.
Missing Value Codes
Missing value codes are represented by a single decimal point.
