Data quality assurance

ASSURANCE OF THE QUALITY OF THE MEASURED DATA

TABELS - DETECTION LIMIT VALUES AND UNCERTAINLY:
PRECIPITATION QUALITY MONITORING MANUAL AIR POLLUTION MEASUREMENT METHODS SUSPENDED PARTICULATE MATTER AND HEAVY METALS IN THE AIR

AIR POLLUTION DATA CONTROL AND VALIDATION

Assurance of the quality of the measured data

The quality of the measured data is assured at several levels. The analyses accuracy is controlled by the analysis of verified standard reference materials (for the determination of SO2 using the thorin method: Titrisol-Sulfat-Standard, Merc, Cat. No. 9872; for ions in precipitation: NIST 3183 Fluoride Standard Solution; NIST 3182 Chloride Standard Solution; NIST 3185 Nitrate Anion Solution; NIST 3181 Sulfate Anion Solution; Simulated Rainwater NIST - SRM 2694 a-I, SRM 2694 a-II). The analyses precision is evaluated by repeated analyses of the same sample. The precision of methods as a whole, i. e. of sampling and analysis, is verified by parallel sampling according to the guidelines set by the Operation rules of the National air pollution network.

CHMI laboratories participate regularly in international round robin tests organized by the World Meteorological Organization/Global Atmospheric Watch (WMO/GAW) and other international tests within international programmes and projects (e. g. EMEP, the Black Triangle). The central CHMI laboratories also performs regular interlaboratory tests (SO2 for the West-Gaeke method) both for the laboratories of the CHMI regional offices and for other organizations that supply their data to the Air Quality Information System (ISKO) database.

Detection limit values and uncertainty - precipitation quality monitoring

Parameter	Detection limit value [μg.l^-1]	Relative standard deviation [%]
cond.		13.6
pH		3.6
F^-	20	21.2
Cl^-	20	15.8
NO^-₃	30	13.7
SO^2-₄	20	10.7
Na⁺	2	14.4
K⁺	3	12.3
Mg²⁺	1	17.1
Ca²⁺	11	10.7
NH₄	20	13.0
Mn	1	20.3
Zn	10	36.6
Fe	50	33.4
Al	100
Pb	2	21.0
Cd	0.1	19.9
Ni	2	30.6

Detection limit values and uncertainty - manual air pollution measurement methods

Pollutant	Detection limit value [μg.m^-3]	Relative standard deviation [%]
SO₂ (West-Gaeke method)	2	to 10 μg.m^-3 30.8 over 10 μg.m^-3 23.8
SO₂ (thorin method)	0.2	28.4
NO_x	0.7	to 10 μg.m^-3 38.2 over 10 μg.m^-3 27.6
HNO₃, NO^-₃	20
NH₃, NH₄	0.01
suspended particulate matter	7.5

Detection limit values and uncertainty - suspended particulate matter and heavy metals in the air

Pollutant (measurement methods)	Detection limit value	Relative standard deviation [%]
SPM [μg.m^-3]	7.5	18.9
CD(AAS) [μg.l^-1]	0.05	7.4
Pb(AAS) [μg.l^-1]	0.78	4.4
Pb(XRF) [μg.m^-3]	1.3	35.2
Zn(XRF) [μg.m^-3]	1.1	23.9
Cu(XRF) [μg.m^-3]	0.5	53.6
Mn(XRF) [μg.m^-3]	0.9	31.0
Fe(XRF) [μg.m^-3]	0.7	26.1
S(XRF) [μg.m^-3]	2.5	18.5

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.