Next generation sensors for urban air quality management and public health protection

Experience in Hong Kong and the way forward

Dr. Zhi Ning, City University of Hong Kong

Ms. Christine Loh, Environmental Bureau

Dr. Peter Louie, Hong Kong Environmental Protection Department

Prof. Greg Carmichael, University of Iowa

Prof. Alexis Lau, Hong Kong University of Science and Technology

WHO Third Meeting of the Global Platform on Air Quality and Health, Madrid, Spain.

March 2017

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Background

Lancet, GBD, 2014

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▪ Urban: small fraction of the Earth’s surface (0.5%) , yet with > 50% of

the world population (3.42 b);

▪ Cities have different “genes”. Hong Kong being representative.

Background

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Background

▪ Integrated urban development and policy making

5

Issues with current practice

▪ High interest by public for more personalized info and by

industry/government for smarter air quality management

Traditional compliance monitor/equipment

• High price and maintenance cost;• High precision but requires professionals.• Regional/local air quality instead of personal info.

“Professional "sensors

• Lower cost and small, compact, easy to deploy;

• Good performance in certain applications with different data quality objective.

Consumer grade sensors (low cost sensors)

• Cheap and small for personal and family usage;• Indication purpose, not scientifically reliable.

Citizen

Science？

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A paradigm shift in air monitoring

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A paradigm shift in air monitoring

▪ However, … expectations and realities

– Data quality is a concern

Credit to:

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Lessons learnt from air quality and public health assessment

▪ Current issues:

– Sensor makers:

No reliable specifications on actual

sensor performance;

Only lab tests for cal curves prior to shipping

– System integrator and vendor

Lack of understanding on sensor performance

Provide incomplete or incorrect QAQC with

system

– System users (Different data objectives)

Rely only on face values from

sensors/systems;

Lack of ability for application specific QAQC

implementation

– 3rd party evaluators

Only evaluation, no practical QAQC

recommendation for applications

Sensor characteristics

Sensor system for desirable sensor performance;

Algorithms for sensor corrections;

Application in air quality and public health

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• Understand actual application needs;

• Design and develop application specific QAQC protocols;

• Ability to implement the QAQC with support of facility and data mining.

• Be clear on the data objectives

• Provide more real-world

specs

• Inform users of pre-filters,

electronics, chemistry

changes

• Detailed testing and

provide results relevant to

applications

• Communicate specs in

reports

• Use and communicate

recommendations

• Provide information useful

to all users—help with

system selection on different

applications

Role of different participants

System developer

Sensor maker

Evaluator

• Comprehensive lab and field

tests for actual system

performance;

• Suggest and demonstrate

the QAQC protocols

• Communicate with users on

the limits and capabilities of

sensor systems

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Protocol development

▪ We develop and integrate next gen sensors and into

complete systems

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Sensor & system test

▪ Sensors have 3 dimension of

factors (Conc, Temp, RH) while

conventional monitors have

only 1 dimension of factor

(Conc only);

▪ Drift has been a concern.

Autozero is important!

20 22 00 02 04 06 08 10

15

20

25

30

35

Sensor_Temp

Adj_CO_Diff_1

CO_step_V (mV)

Time

-100

-50

0

50

100

150

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Concerns on the inter-consistency

▪ First tier of inter-consistency check on multiple devices

– Cross check on the

raw data output on the

multiple sensor devices;

– Main unit versus satellite

units for quality

assurance.

– Periodical quality control

for inter-consistency

check.

6 devices side by

side for their cross

consistency first

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Concerns on the field performance

QAQC protocol is

important.

Report on Evaluation and

QA/QC protocol for the

next generation air

monitoring, Ref 14-02771,

City University and Hong

Kong Environmental

Protection Department.

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2015 Standard Chartered International Green Marathon-our first sensor-based monitoring

In support of government initiative for “2015

Standard Chartered Green Marathon”

150.4

0.6

0.8

1

1.2

3:07 4:19 5:31 6:43 7:55 9:07 10:19 11:31 12:43

CO

/ p

pm

TST COTST CO

▪ Traffic control was

effective to

suppress pollution

levels during the

race

▪ Roadside traffic

related pollutants

quickly jumped

once traffic control

lifted

0

100

200

300

400

500

NO

/p

pb

TST NONO Concentration

before/during/after traffic control

Motorcycles created

spikes of CO

2015 SC Green Marathon network

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The product—a better informed public.

▪ Enhanced data

availability and

access

1717

• Bus mobile sensor platform

• Compact and multipollutant solutions for

PM2.5,NO2,SO2,CO2 (traffic pollutants)

• GPS/ traffic speed data and real time

transmission

• QAQC is very important for long term

unattended operation!

Auto zero

Nafion tube

for equilibrium

Mobile Air SEnsor Network (MASEN)

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• Real time and real world

pollution map;

• Roadway network emission

and air quality modelling；• Hotspot identification and

evidence based policy making;

• Transport optimization.

Mobile Air SEnsor Network (MASEN)

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Personal Exposure Kit (PEK)▪ A portable device

– Can be carried and placed anywhere

– Can measure, transmit + record real-time data

▪ Several microenvironments studied

– Office, Home, Commuting, schools, indoor and outdoor

▪ Multiple configurations possible

▪ PM and 5 gases possible

– 3-axis accelerometer, noise sensor, light sensor

– Temp/RH sensor

– GPS and telemetry

– Encrypted Q-R code for online survey

Restaurant Inside Subway Park Mini-Bus

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Personal Exposure Kit (PEK)

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Regulatory data representativeness?

▪ AQMS poorly

represents individual

exposure and large

variation of average

exposed PM2.5

▪ Day of week

differences by be due

to individual

activities

▪ Patterns of

exposures may differ

between

communities and

AQMS sites

8 times

Only 0.5

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Citizen involvement in school community

▪ Indoor and outdoor monitoring system

with cloud connection and data display

• Temp/RH

• CO2

• PM2.5

• NO/NO2

• TVOC

• Formaldehyde

• Wifi/GSM/Zigbee

• Ethernet

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Other on-going investigations

▪ UAV-based airborne monitoring

– Light weight application

SO2

CO2

Emission

1 3

2

32

Target ship plume

BC

NOx

SO2

CO

CO

Path

Radio

Path and command

USB cable, SDK

Path and command

Programming

Data

UART

Wi-Fi Data

Propeller mixing

Plume imaging

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The way forward…

▪ “Low cost” and “professional” sensors are here to stay and

there are ample opportunities for sensor usage;

▪ They should not be viewed as substitution of

regulatory/compliance monitoring;

▪ Awareness and understanding of potential and limitations of

sensor based monitoring systems is the key to their

successful use;

▪ A focus on systems and data quality objectives instead of

sensors in research, calibration and communications;

▪ Professional data user versus citizen science user have

different needs for QAQC and organizational support;

▪ Clear and coherent guidelines urgently needed …

We are ready for WHO’s involvement!