local authority case study large scale deployment of...

Local Authority Case Study – Large Scale

Deployment of Sensors

D. Carruthers1, D. Clarke2, K. J. Dicks3, R. A. Freshwater4, M. Jackson1,

R. L. Jones4, C. Lad1, I. Leslie5, A. J. Lewis3, H. Lloyd4, O. A. M. Popoola4,

A. Randle6, S. Ulrich4

1Cambridge Environmental Research Consultants, UK 2Cambridgeshire County Council, Cambridge, UK3Cambridge City Council, Cambridge, UK4Department of Chemistry, University of Cambridge, UK5Computer Laboratory, University of Cambridge, UK6Environmental Instruments Ltd., Stratford-upon-Avon, UK

AQE 2017, Telford, 25th May 2017 1

AQE 2017, Telford, 25th May 2017

Talk outline

• Premise of inter-comparison

• AQMesh, network deployment

• Comparison with reference instruments

• What can we do with the measurements?

- Model comparison

- Source attribution• Local emissions

• Long range sources

2

AQE 2017, Telford, 25th May 2017

Premise of inter-comparison:

• Test of ‘out of box’ AQMesh performance

• No local calibration/re-scaling

• No pan-network analysis (individual sensors)

• NO, NO2, PM2.5, PM10 only (determined by

available reference instruments)

3

Sensor Calibration Gas sensors

Comparison between Alphasense electrochemical

sensors and local (to AQMesh) reference

instrumentation to determine sensor specific calibration

parameters.

Particle sensor

OPCs co-located with a “gold standard pod” at the

AQMesh outdoor test facility to provide consistent

calibration parameters.


CO, NO, NO2, O3, SO2,

PM1, PM2.5 and PM10

Cross network NO2 performance

(pre-deployment)

Gradients = 0.94 ± 0.07

R2 = 0.8 ± 0.11

Intercepts = 0.34 ± 0.47ppb


Sensor-sensor

comparisons

Cross network PM2.5 performance

(pre-deployment)

Gradients = 0.98 ± 0.07

R^2 = 0.98 ± 0.17

Intercept=0.13 ± 0.3ug/m3


Sensor-sensor

comparisons


Cambridge deployment (20 nodes)

Northwest Cambridge(building development)

Central Cambridge(high traffic density)

South Cambridge(biomedical campus development)

Reference site(Gonville Place)


NO2 city centre comparison (pre-ratified)

Gradient Intercept R2

0.55 (0.006) 10.0 (0.1) 0.50

• Similar features (diurnal

signatures) in both

• AQMesh significantly higher

in absolute amounts than

reference (not consistently)


NO2 city centre comparison (pre-ratified)


0.75 (0.01) 4.5 (0.2) 0.64

1.67 (0.02) 6.1 (0.16) 0.64

0.67 (0.007) 4.9 (0.19) 0.78

• Clear calibration changes

(three distinct phases) (in

which instrument……?)


NO2 city centre comparison (ratified)

No reference data!

NO2 Gradient Intercept R2

pre 0.55 (0.01) 10.0 (0.1) 0.50

post 0.82 (0.01) 5.1 (0.13) 0.74*

*Improvement is from AURN ratification

NO Gradient Intercept R2

pre 0.85 (0.01) 4.4 (0.21) 0.49

post 0.87 (0.01) 0.63 (0.3) 0.65*


PM2.5 city centre comparison (ratified)

• PM events captured

• Some overestimation by AQMesh

• Little/no difference on ratification


pre 0.92 (0.01) -3.0 (0.15) 0.41

post 0.92 (0.01) -3.0 (0.15) 0.42


PM10 city centre comparison (ratified)

• PM events captured by AQMesh

• Magnitudes significantly

overestimated in AQMesh

• Little/no difference on ratification


pre 1.17 (0.02) -8.7 (0.51) 0.21

post 1.17 (0.02) -8.7 (0.51) 0.21

Gonville Place AQMesh reference

comparison statistics summary


NO2 pre 1.07 (0.01) 10.0 (0.1) 0.50

NO pre 1.07 (0.01) 4.4 (0.21) 0.49

PM2.5 pre 0.92 (0.01) -3.0 (0.15) 0.41

PM10 pre 1.17 (0.02) -8.7 (0.51) 0.21



NO2 post 0.82 (0.01) 5.1 (0.13) 0.74

NO post 1.09 (0.01) 0.63 (0.27) 0.65

PM2.5 post 0.92 (0.01) -3.0 (0.15) 0.42

PM10 post 1.17 (0.02) -8.7 (0.51) 0.21

Pre- AURN ratification

Post- AURN ratification

Improvement is from AURN ratification


NO2 city centre model-AQMesh

comparisons

Gradient R2

AQMesh - ADMS 0.34 0.24

AQMesh - reference 0.82 0.74

• Model captures broad behaviour

• Poorer R2 c.f. AQMesh-reference

• Poorer model-reference R2


PM2.5 city centre model-AQMesh

comparisons

Gradient R2

AQMesh - ADMS 0.265 0.03

AQMesh - reference 0.92 0.42

• Model captures magnitudes of

events but not timing…..

• Significantly poorer R2 c.f. AQMesh -

reference


Average NOx model-AQMesh comparisons

– all stations

• Model ~ captures AQMesh spatial gradients

• Local (spatially heterogeneous) sources


Average PM model-AQMesh comparisons

– all stations

• Model ~ captures (lack of) spatial gradients

• Averages dominated by non-local sources


What does this mean?

Spatial gradient implies local

source in city…..

Local intervention possible

No spatial gradient implies

mainly regional source…..

Regional intervention

required

NO2: significant differences– road sources (1)– local sources (2)– non local sources (3)

1

1

1

2

3

3

3


3

3

3

PM10: broadly similar – longer range transport?– building site influences (1)

1

11



Summary

• AQMesh sensor performance ‘out of box’ performance:• Sensor- sensor reproducibility very good.

• NO/NO2/NOx inter-comparison with ratified measurements good.

• PM measurements capture events, some overestimation (esp. PM10).

• Ratification process produces some rather surprising results……

• AQMesh captures spatial gradients well• Spatial gradients for NOx (local emissions)

• Little spatial gradients for PM (long range transport)

Important for understanding role of policy interventions

• Source attribution

- Hotspot detection

- NO2 short term exceedences

- PM emissions building works

AQMesh performs well: hotspots, A/Q monitoring/control

D. Carruthers1, D. Clarke2, K. J. Dicks3, R. A. Freshwater4, M. Jackson1,

R. L. Jones4, C. Lad1, I. Leslie5, A. J. Lewis3, H. Lloyd4, O. A. M. Popoola4,

A. Randle6, J. Stocker1, T. Townend6, S. Ulrich4

1Cambridge Environmental Research Consultants, UK 2Cambridgeshire County Council, Cambridge, UK3Cambridge City Council, Cambridge, UK4Department of Chemistry, University of Cambridge, UK5Computer Laboratory, University of Cambridge, UK6Environmental Instruments Ltd., Stratford-upon-Avon, UK


local authority case study large scale deployment of...

Documents