U.S. EPA’s AirNow International Air Sensor Applications ... · Manager, AirNow & International...

U.S. EPA’s AirNow International Air Sensor

Applications and Initiatives in Accra, Ghana

915406-6930

Alan C. Chan and Levi G. StantonSonoma Technology, Petaluma, CA, U.S.A.

Phil Dickerson, John White, and Lourdes MoralesU.S. Environmental Protection Agency, Research Triangle Park, NC, U.S.A.

Emmanuel AppohGhana Environmental Protection Agency, Accra, Ghana

for

2018 Better Air Quality ConferenceInternational Action and Cooperation on

Air Pollution Management

Kuching, MalaysiaNovember 12-16, 2018

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Outline

• Overview and Motivation

• Project Scope

• Instrument & Siting

Considerations

• Sensor Data Management

• Collocation Study

• Initial Results

• Next Steps

AirNow International Ghana

3

Overview and Motivation

Many African cities lack the capacity and

cost-effective means to measure and

characterize ambient air quality to support

critical objectives.

• This work is part of the Africa

Megacities Partnership’s Air Quality

Management Planning Initiatives.


Air quality data gaps (source: AQICN.org)

• Ghana Environmental Protection Agency (Ghana EPA), U.S. EPA,

U.S. Department of State, and World Bank’s Pollution Management and

Environmental Health program are collaborating on this effort.

• The project includes low-cost particulate matter (PM) air sensor network

deployment and operations, infrastructure for sensor data management,

and capacity building.

AQICN.org

4

Objectives


• In Accra, complement the Ghana EPA’s

existing monitoring network and planned

regulatory grade monitors from the World

Bank with low-cost sensors.

• Demonstrate the feasibility/capabilities of a

PM sensor network with real-time data.

• Characterize the performance of low-cost

sensor technologies in Accra’s unique

environmental conditions.

• Integrate an advanced data system (AirNow

International) into Ghana EPA’s monitoring

and management practices, and communicate

timely air quality information to the public

(important for sensitive groups).

• Build capacity among Ghana EPA staff to

operate and analyze the data from the sensor

network.

5

Project Scope

• Select sites and sensors

• Deploy sensors and conduct

sensor collocation study

• Operate sensors from August 2018

to July 2019

• Manage collected data using the

new U.S. EPA AirNow-International

system

• Interpret findings from data

• Build EPA Ghana’s real-time

monitoring capacity


6

Instrument and Siting Considerations


✓ Pollutants measured

✓ Monitoring methodology

✓ Sensor performance

✓ Data handling

transparency

✓ Power requirements

✓ Communications

✓ Affordability

✓ Customer support

✓ Troubleshooting options

✓ Sites selected in consultation

with EPA Ghana

✓ Representativeness of a

variety of urban emissions

sources (near-road, industrial,

and residential)

✓ Access

✓ Security

✓ Power

7

Instruments


• Clarity Node-S sensors (18) measure PM2.5,

temperature (T), and relative humidity (RH),

and include a battery and solar panel to

reduce the need for line power at the sites.

Sensors collect 90-second averages of PM2.5,

PM10, T, and RH about every five minutes.

Data are transmitted via cellular network.

• PurpleAir sensors (5) provide 80-second data

for PM1.0, PM2.5, and PM10 along with T, RH,

and pressure, using on-board storage.

• Campbell Scientific all-in-one MetSens600

weather stations (3) measure T, RH, pressure,

wind (speed, direction), and precipitation.

8

Sensor Data Management


• AirNow-I system is set up in the cloud to

allow EPA Ghana to manage data collected

from the low-cost sensors, existing PM10

monitoring stations, and future sites.

– Quality control

– Email reports

– Data query and export

– Visualization and data analysis tools

• AirNow-I database provides a secure

repository, with the scalability to process

and store high-time-resolution data.

• Raw sensor measurements from the Node-

S sensors are transmitted to the Clarity

Cloud (where “Smart Calibration” is

performed) and also directly to the

AirNow-I system.

9

Collocation Study


Collocation is performed to assess sensor

precision, accuracy, and bias.

1. All sensors and meteorological

instruments were collocated at the EPA

Ghana building for one week before being

deployed to sites.

2. Pending the upcoming deployment of

regulatory-grade PM instruments by the

World Bank program, we will collocate all

sensors with the reference instruments in

the middle of the measurement period.

3. At the end of the measurement period, all

sensors will be collocated again for

inter-comparison.

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Correlation Analysis Across all Sensors


A scatter plot matrix for all sensors during collocation. Darker red indicates a lower R2 (0.89 ≤ R2 ≤ 0.99). Darker

blue indicates a greater deviation of the slope from 1 (0.0≤ |1-m| ≤ 0.12).

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Initial Results


μg/m3

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Temporal PM2.5 Trends Across Entire Network


13

Sensor-to-sensor correlation over study period

at four different sites (1-hr averages)


Black diagonal line is the 1:1 line, red diagonal line is the equation determined by

linear regression

14

Next Steps

• Collocation with World Bank’s Pollution Management

and Environmental Health (PMEH) program’s

regulatory grade instruments

• Backfill of historical PM10 data

• Completion of Quality Assurance Project Plan (QAPP)

• Final data analysis

• Scientific journal paper


Alan C. ChanManager,

AirNow & International Programs

[email protected]

Levi G. StationSensor Program Lead /

Project Manager

[email protected]

15

+1-707.665.9900 sonomatech.com @sonoma_tech


mailto:[email protected]

mailto:[email protected]

U.S. EPA’s AirNow International Air Sensor Applications ... · Manager, AirNow & International...

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