uncertainties in atmospheric observations wenche aas emep/ccc
TRANSCRIPT
Uncertainties in atmospheric observations
Uncertainties in atmospheric observations
Wenche Aas EMEP/CCC
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Sources of uncertaintiesSources of uncertainties
Sampling and analytical method Detection limit Interference Instrument drift, calibration Positive or negative artefact
Sampling procedure Contamination Temperature and period for storage Transport
Representativity. Local farming (NH3) Nearby roads (NOx; O3) Dust (PM, Ca..)
Lab- and field intercomparison
Field inter-comparison; model comparison
Repr. studies, i.e passive sampling. Model comparison
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Monitoring programme:Level 1•Main ions in precipitation and in air •heavy metals in precipitations•ozone •PM10 and PM2.5 mass •meteorology
at ca 125 sites
Level 2, supersite (joint EMEP/GAW)• POPs• Heavy metals in air and aerosols• VOC• EC/OC, OC speciation• Mineral Dust• PM speciation incl. gas particle ratio
+ all level 1 activities
15-20 sitesBoth levels are mandatory by all Parties
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Data quality objectivesData quality objectivesAcidifying and eutrophying compounds
o 15-25% uncertainty in annual average (10-15% for indiv meas.)
Heavy metals
o 30% uncertainty in annual average (15-25% for indiv meas.)
o 40 % uncertainty for As, Cd, Ni in the EU 4th DD (70% in dep)
o 50% uncertainty for Hg (total gas) in the EU 4th DD
POPs (not defined in EMEP)
o 50% uncertainty for PAH in the EU 4th DD (70% in dep)
PM (not defined in EMEP)
o 25% accuracy in continuous measurements EU 1st DD
Photooxidants (not defined in EMEP)
o: 15% accuracy in continuous O3, NOx measurements, EU 3rd DD
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Lab intercomparisons annually, 2005Lab intercomparisons annually, 2005
Spread: 2RSD % Bias: RB %
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
WMO
ICP
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
0
1
2
3
4
5
Nov-02 Dec-02 Jan-03 Feb-03 Mar-03 Apr-03 May-03 Jun-03 Jul-03 Aug-03 Sep-03 Oct-03
g-S
/m3
Preila
NILU
y = 0.83x + 0.05
R2 = 0.960
2
4
6
0 2 4 6
Preila
NIL
U
all for slope
Preila (LT) using filterpack
SO2 field intercomparisonSO2 field intercomparisonZarra (ES) , abs (H202) and monitor
0
1
2
3
4
5
Jun-00 Aug-00 Oct-00 Dec-00 Mar-01 Apr-01
g-S
/m3
Reference filterpack
Absorption, H2O2
UV fluoresence monitor
0
2
4
6
8
10
0 30 60 90 120 150 180 210 240 270 300 330 360
julian day, 2000
gS
/m3
Filterpack
TCM
y = 1.18x - 0.05
R2 = 0.87
0
2
4
6
8
10
0 2 4 6 8 10TCM
filt
erp
ac
k
0
0.5
1
1.5
2
2.5
0 30 60 90 120 150 180 210 240 270 300 330 360
julian day, 2000
gS
/m3
Filterpack
TCM
y = 0.87x + 0.34
R2 = 0.26
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2 2.5
TCM
filt
erp
ac
k
TCM ain Germany (historic data) at DE09 (left and DE03 (right)
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
SO2. UV fluoresence monitor, interference
0
2
4
6
8
samples from Jan 02 - Jan 03
g
-S/m
2
NILU - filterpackEMPA -not corrEMPA -corr for NOEMPA -corr for NO and H20
'
y = 0.40x + 0.24
R2 = 0.66
y = 0.69x + 0.13
R2 = 0.82
0
4
8
0 4 8
EMPA
NIL
U
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
NO2. Chemiluminisence (Mo converter)NO2. Chemiluminisence (Mo converter)
0
5
10
15
20
samples from Nov 01 - Nov 02
g-N
/m3
NILU -glass sinters
EMPA (Monitor)
y = 0.68x - 0.17
R2 = 0.77
0
10
20
0 10 20
EMPA
NIL
U
Not selective for NO2
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
QA flagQA flagLab flag
Field flag
Green: Bias < 10%Spread <20% (S,N)
Blue:Bias < 40%Spread <40% (S,N)
Green: Bias < 10%Spread <25%
Blue:Bias < 50%Spread <50%
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
QA Flag for main ions in 2005QA Flag for main ions in 2005In precip In air
Analysis in lab are in general better than 20% (both in air and precip)
Total uncertainty (field intercomp):
about half the measurements is better than 25%
rest better than 50%
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Lab intercomparison of HM annuallyLab intercomparison of HM annually
Average per cent error, 2005
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Hg intercomparison at DE02 in 2006Hg intercomparison at DE02 in 2006
-50
-40
-30
-20
-10
0
10
20
30
40
50
J G X D B H E I C A F
Dif
fere
nce
s in
%
Data quality objective within EMEP (accuracy in annual average)
Tekran
Tekran
Tekran
Tekran TekranManual
Manual
Manual
Other Other Other
Laboratory
2 9 7 3 1 4 8 5
20
18
16
14
12
10
8
VR
Vr (w-o)
(w-o)
(w-o)(w-o)
(bulk)(bulk) (bulk)
(bulk)
Data quality objective within EMEP (30% in annual average)
Ove
rall
wei
ghte
d m
ean
in n
g/L
SR = ± 5.8 ng/L
SR
Tot Hg(g) in air
Tot Hg in precip
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Heavy metal deposition, CEN WG20Heavy metal deposition, CEN WG20
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
WO Bulk WO Bulk WO Bulk WO Bulk
Pb As Cd Ni
g/m
2 d
ay
Funnel
Sampler
WO Bulk Avg SD rel SD nrCd 0.11 0.10 0.10 ± 0.02 20 % 17Pb 4.2 4.4 4.3 ± 0.7 15 % 17As 0.4 0.4 0.4 ± 0.1 13 % 17Ni 1.6 1.4 1.5 ± 0.6 43 % 16
Birkenes, wet only - bulk
Birkenes, comparing wet only (analysed at UBA) and bulk (NILU)
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Parallell wet only, CEN WG 20Parallell wet only, CEN WG 20
Avg SD rel SD nr Avg SD rel SD nr Avg SD rel SD nr Avg SD rel SD nrCd 0.18 ± 0.03 18 % 11 Cd 0.05 ± 0.01 13 % 19 Cd 0.07 ± 0.01 9 % 17 Cd 0.44 ± 0.04 9 % 19Pb 7.4 ± 0.5 7 % 11 Pb 2.2 ± 0.3 15 % 19 Pb 3.2 ± 0.3 10 % 17 Pb 28 ± 3 11 % 19As 0.7 ± 0.1 19 % 11 As 0.18 ± 0.02 11 % 19 As 0.26 ± 0.02 6 % 17 As 0.72 ± 0.05 7 % 19Ni 2.8 ± 0.3 12 % 10 Ni 0.8 ± 0.1 13 % 19 Ni 1.3 ± 0.3 20 % 14 Ni 4.0 ± 0.4 11 % 19mm 34.7 ± 3.1 9 % 7 mm 15.7 ± 1.6 10 % 18 mm 15.7 ± 0.5 3 % 19 mm 16.4 ± 0.5 3 % 19
deposition, µg/m²/day deposition, µg/m²/day deposition, µg/m²/day
Birkenes Peyrusse Copenhagen
Between sampler uncertainty, Wet only
deposition, µg/m²/day
Duisburg
From To
Cd 9% 18%
Pb 7% 15%
As 6% 19%
Ni 11% 20%
Relative SD in deposition measurements:
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
POP lab intercomparison,2002POP lab intercomparison,2002
pp'-DDT
-100
-50
0
50
100
150
200
250
129A
121
105
118
113
103
131
131
104
123
108
110
116
102
109
101
115
Lab no.
Dev
. fro
m m
edia
n [
%]
10075
g-HCH
-80
-60
-40
-20
0
20
40
60
109
115
131
131
118
101
102
103
116
113
104
105
121
123
108
110
129A
Lab no.
Dev
. fro
m m
edia
n [
%]
PCB 153
-40
-20
0
20
40
60
80
100
120
140
113
121
105
131
131
109
129A
118
104
103
115
108
110
116
102
101
Lab. no.
Dev
. fro
m m
edia
n [
%]
113237
Phenanthrene
-50
-40
-30
-20
-10
0
10
20
30
40
50
101
129A
116
131
131
109
108
102
103
105
107
113
104
123
Lab no.
Dev
. fr
om
med
ian
[%
]
-58
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Artefact in gas/particle for NArtefact in gas/particle for N
0
1
2
3
4
5
6
SO4 NO3 NH4
g/m
3
Artefact free fine
PM2.5
PM10
Artefact free total
0
1
2
3
4
5
6
SO4 NO3 NH4
g/m
3
Artefact free fine
PM2.5
PM10
Artefact free total
IT01, Jan 2007
IT01, June 2007
Artefact free measurements using denuders only done at Montelibretti
NO3 NH4 NO3 NH4Fine 53 % 27 % 82 % 64 %Total 31 % 50 %
June 2006 Jan 2007
Underestimation of N
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Estimates of the positive artefact of OC in PM10 and PM2.5/PM1 -June 2006
Estimates of the positive artefact of OC in PM10 and PM2.5/PM1 -June 2006
0
10
20
30
40
50
60
70
NO56 IT01 NO01
Po
siti
ve a
rtef
act
OC
p/O
C (
%)
PM10
PM2.5 or PM1
QBQ-approach
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Measurement and model intercomparisonMeasurement and model intercomparison
Cd in precip at FI17
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1990,Jan 1992,Jul 1995,Jan 1997,Jul 2000,Jan 2002,Jul
Mod
Obs??
NO
ES
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Uncertainties in trendsUncertainties in trends
First year Last Year Signific. % change Signific. % changeAT02 1980 2003 * -33 % *** -39 %AT04 1985 2003 ** -34 % 0 -13 %CH02 1980 2003 ** -28 % ** -30 %CZ01 1980 2003 * -33 % *** -37 %DE07 1980 2003 + -27 % * -33 %DE01 1980 2003 0 -20 % ** -27 %DE03 1980 2003 ** -44 % * -19 %DE05 1980 2003 ** -49 % *** -33 %DK05 1980 2003 * -32 % *** -36 %FI04 1980 2003 * -22 % *** -38 %FI09 1980 2003 0 -34 % *** -56 %FR03 1980 2003 0 -11 % 0 -24 %FR05 1980 2003 0 -36 % *** -55 %GB02 1980 2003 + -26 % 0 -8 %GB06 1985 2003 0 18 % 0 -24 %HU02 1980 2003 0 -26 % ** -32 %IE01 1985 2003 0 -16 % 0 -15 %IT01 1980 2003 0 -18 % + 49 %LT15 1980 2003 * -45 % * -28 %NO01 1980 2003 0 -17 % ** -24 %NO39 1980 2003 0 -4 % * -24 %PL02 1985 2003 * -38 % *** -42 %PT01 1980 2003 0 -1 % 0 41 %RU01 1985 2003 * -34 % 0 42 %SE05 1980 2003 * -23 % * -28 %CS05 1985 2003 + -25 % 0 41 %
measurmentsNO3 precip
ModelSO2
SO4 in air
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Representativity, NO2
Representativity, NO2
Site Nr Obs Model Bias Spread R^2AT0002 2345 1.57 2.57 -0.39 1.76 0.57BE0032 3493 3.33 4.83 -0.31 2.42 0.69ES0007 3122 0.87 2.73 -0.68 7.71 0.15IT0001 3300 3.16 4.79 -0.34 2.55 0.22NL0091 2774 5.84 7.03 -0.17 2.45 0.68
NO2, 1999-2005
Comparing EMEP model and obs. in light of population density
ES07
IT01
NL91
AT02BE32
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
ConclusionsConclusions Many factors influence uncertainty in measurements
Methodology, sampling procedure, Representativity
Need to distinguish between uncertainty in one data point, in averages and trends; and distinguish between bias and spread
In general, the measurements are within DQO if reference methods are used and the site is representative, but there are exceptions
Need to have better control of artefacts, especially nitrogen gas/particle and EC/OC
More intercomparison of other species than main comp and HM are needed
Wenche Aas, Measurement uncertainty. TFMM/TFEIP Dublin 22 Oct 2007
Data quality objectivesData quality objectivesAcidifying and eutrophying compounds
o 15-25% uncertainty in annual average (10-15% for indiv meas.)
Heavy metals
o 30% uncertainty in annual average (15-25% for indiv meas.)
o 40 % uncertainty for As, Cd, Ni in the EU 4th DD (70% in dep)
o 50% uncertainty for Hg (total gas) in the EU 4th DD
POPs (not defined in EMEP)
o 50% uncertainty for PAH in the EU 4th DD (70% in dep)
PM (not defined in EMEP)
o 25% accuracy in continuous measurements EU 1st DD
Photooxidants (not defined in EMEP)
o: 15% accuracy in continuous O3, NOx measurements, EU 3rd DD