ASSURANCE OF THE QUALITY OF THE MEASURED DATA

TABLES - DETECTION LIMIT VALUES AND UNCERTAINLY:
MANUAL AIR POLLUTION MEASUREMENT METHODS   AUTOMATIC AIR POLLUTION MEASUREMENT METHODS   SUSPENDED PARTICULATE MATTER AND HEAVY METALS IN THE AIR

PRECIPITATION QUALITY MONITORING   AIR POLLUTION DATA CONTROL AND VALIDATION

 

Assurance of the quality of the measured data

The quality assurance of air pollution measurements by means of automated methods and their calibration, the manual methods of air pollution, aerosols and precipitation monitoring and the subsequent quality control of the obtained data are in charge of the Central air pollution laboratories, CHMI Prague and laboratories in regional offices in Brno, Hradec Králové, Ostrava and Ústí nad Labem. The quality of the measured data is assured at all levels.

For continuous measurements within the AIM network analysers of gaseous pollutants (SO2, NOx, CO, O3) are used. They are equipped with the zero-span check system (121-h interval). Twice a year the analysers are checked by five-point calibration in the calibration laboratory which has been accredited for air pollution measurements and has a role of a reference centre on air pollution monitoring.

Manual sampling methods for air pollution measurements, aerosol composition monitoring and precipitation quality are controlled by parallel sampling at selected sites and with the use of blank samples. The quality assurance and control of the activity of chemical laboratories is carried out according to the requirements for trace and ultra-trace chemical determination.

Central Air Pollution Laboratory Prague participates regularly in international round robin tests organized by World meteorological organization (WOM/GAW). The activity of CHMI laboratories is regularly controlled in international round robin tests within European monitoring network EMEP. Central Air Pollution Laboratories are involved in international programmes and research projects. The central CHMI laboratories also perform regular interlaboratory tests (SO2 for West Gaeke method) both for the laboratories of CHMI regional offices and for other cooperating organizations.

The accuracy of laboratory determinations is controlled regularly by the analysis of the respective certified reference materials NIST. The precision of laboratory determinations is evaluated by repeated analyses of the same sample. The precision of determinations as a whole, i.e. including the sampling and the analysis, is estimated from parallel samplings according to the guidelines set by the Operation rules of the National air pollution network. The relative uncertainty of determination incl. the sampling covers the determination accuracy, precision of laboratory determination and sampling variability. The presented uncertainties are expanded uncertainties (expansion coefficient k=2). Due to the increasing number of determinations ranging close to the margin of detection the presented uncertainties of measurements incl. the samplings are relatively high. The detailed description of uncertainty calculation is given in the standard operating procedure (SOP) for each method and the respective sampling of the monitored pollutant.

The ISKO database includes also data from other special-purpose monitoring networks operated by further cooperating organizations (ČGS, VÚLHM, VÚV and HBÚ AVČR).

Detection limit values and uncertainty - manual air pollution measurement methods

MethodUncertainty Margin of detection
[μg.m-3]		Calibration range
[mg.l-1]
Standard/Expanded
[μg.m-3]		Relative/Expanded
[%]
SO2 (West-Gaekova method) 3.28 16.7 3 3
SO2 (IC as SO2-4) 0.57 14.4 0.03 20
HNO3, NO-3 1.23 31.2 0.01 20
NOx 9.08 15.3 5.0 15.3
NH3, NH4+ 0.96 28.8 0.02 10
Total suspended particles 3.44 8 5 -


Detection limit values and uncertainty - automatic air pollution measurement methods

PollutantMargin of detection
[μg.m-3]		Standard uncertainty
abs. [μg.m-3]rel. [%]
SO2* (UV fluorescence) 1.5 1.5 8
NO* (chemiluminiscence) 0.7 0.7 8
NO2* (chemiluminiscence) 1.0 1.0 10
NOx* (chemiluminiscence) 1.0 1.0 10
CO* (IR correlation spectrometry) 125 125 8
O3* (UV absorption photometry) 1.0 1.0 8
PM10** (radiometry) 3.5   20
BTX*** (gas chromatography) <1  20

Detection limits according to parameters of the following device
*
Thermoelectron
**
Verewa
***
Chrompack
Description
The given deviations are provisional. The values will be futher precised.


Detection limit values and uncertainty - dust fallout and trace elements in the air

MethodUncertainties Margin of detection
[μg.m-3]		Calibration range up
[μg.cm-2]
Standard/Expanded
[ng.m-3]		Relative/Expanded
[%]
TSP 3.44 8.0 5.0  
MetodaUncertainties Margin of detection
[ng.cm-2]		Calibration range up
[μg.cm-2]
Standard/Expanded
[ng.m-3]		Relative/Expanded
[%]
Al(XRF) 292 60.6 17.6101.2
Br(XRF) 2.34 50.4 0.6 17.5
Ca(XRF) 278 48 9 75.9
Cl(XRF) 186 123.64.8 87.4
Cu(XRF) 6.96 57.6 0.7 96.7
Fe(XRF) 294 49.2 0.7 99.8
K(AAS) 148.643.8 6.3 37.6
Mg(XRF) 35 37.2 3.2 83.7
Mn(XRF) 8.96 61.2 0.8 54.8
Na(XRF) 75.8 59.6 5.3 56.7
Ni(XRF) 0.8 37.4 0.6 89.2
Pb(XRF) 8.56 43.6 1.5 196.3
S(XRF) 462 34.0 2.6 25.1
Si(XRF) 650 48.6 8 63.7
Zn(XRF) 26.8 45.2 1 296
MethodUncertainties Margin of detection
[ng.m-3]		Calibration range up
[μg.m-3]
Standard/Expanded
[ng.m-3]		Relative/Expanded
[%]
As(AAS) 0.48 20 0.2 50
Cd(AAS) 0.06 20 0.015.0
Pb(AAS) 1.02 20 0.2 50


Detection limit values and uncertainty - precipitation quality monitoring

Method)Uncertainties Margin of detectionCalibration range up
Standard/ExpandedRelative/Expanded
[%]
pH 0.62 12.2 0.01  
MethodUncertainties Margin of detection
[μS.cm-1]		Calibration range up
[μS.cm-1]
Standard/Expanded
[μS.cm-1]		Relative/Expanded
[%]
conductivity 7.66 25 0.5 100*
MethodUncertainties Margin of detection
[μg.l-1]		Calibration range up
[μg.l-1]
Standard/Expanded
[μg.l-1]		Relative/Expanded
[%]
F- (IC) 0.25 178.1 10 2
Cl- (IC) 0.23 16.3 20 20
NO-3 (IC) 0.76 20.5 40 20
SO2-4 (IC) 1.12 27.2 40 20
Na+ (AAS) 0.05 22.6 7 1
K+ (AAS) 0.05 42 8 1
Mg2+ (AAS) 0.11 15.4 2 1
Ca2+ (IC) 0.13 17.6 14 1
NH+4 (SFA) 0.67 20.8 20 10
Cd (AAS) 0.06 35 0.040.001
Fe (AAS) 0.03 30.8 6 1
Mn (AAS) 5.77 23 0.5 0.05
Ni (AAS) 0.47 32.6 1 0.05
Pb (AAS) 0.68 20.4 0.7 0.05
Zn (AAS) 0.01 21.8 3 1


Air pollution data control and validation

Air pollution data submitted to ISKO are checked in compliance with the Operation rules of the National air pollution network. The measured results are checked twice: the first, monthly control is in charge of the regional network administrator. This is done prior to data affirmation or supply to ISKO. The second control is implemented by ISKO, and namely for each quarter of the current year.

Both procedures are based on the control of formal and logic parameters aimed at the detection and elimination of gross errors which could affect and lower the statistical characteristics of the data file. For the 2nd control in ISKO the statistical method aimed at revealing the striking daily averages of the measured air pollution levels has been used for several years. The method proceeds from the fact that the differences of the subsequent daily averages should generally remain within the limits of double exponential distribution and that the course of daily concentrations of air pollutants from the neighbouring stations should be similar.

The air pollution data are authorized exclusively by the regional network administrator to whom the shortcomings encountered during the 2nd control and potential proposals for their remedy are reported. It is the regional network administrator who makes the decision on data authorization, keeps the archives of the data file and in case the file is changed, supplemented or amended he/she sends the updated version to ISKO without delay.