Early ambient air pollution monitoring in the UK began in the 1950s in response to deadly smog events. This led to the first national monitoring network in the 1960s measuring smoke and sulfur dioxide. Understanding of complex photochemical smog developed in the 1970s from US experiences, widening monitoring to include other traffic-related pollutants. By the 1990s, many ambient air quality surveys had begun, facilitated by new instrumentation. Current strategies for monitoring individual sites involve defining clear objectives to design cost-effective programs considering parameters, timing, locations, and methods.

1. rpsgroup.com
IAQM EARLY CAREERS GROUP MONITORING
WORKSHOP, 17TH JULY 2019
Ambient Air Pollution
Monitoring – a Brief History from Early
UK Measurement Surveys to Modern
Investigative Strategies
Jon Pullen

2. Introduction
A look back over nearly 60 years of ambient air pollution monitoring:
➢Starting with the events here in the 1950s that drove policy leading to the
earliest national monitoring surveys
➢The establishment in the early 1960s of the world`s first coordinated national air
pollution monitoring survey
➢How improved understanding of air pollution sources and atmospheric chemical
interactions led to large-scale monitoring surveys covering a wider range of air
pollutants using more sophisticated measurement techniques
➢The power industry`s monitoring networks running from the 1970s to the 1990s
➢The development of the UK`s government-funded automatic monitoring network
➢The blossoming of ambient air monitoring surveys from the 1990s onwards
➢Strategies for monitoring around individual regulated sites
2
Introduction

3. Early Days
The drivers….
• The `Great Smog` of December 1952 arose from:
➢ Stationary high pressure system 9-11 Dec, windspeeds fell, temperatures around
freezing, prevailing through much of Britain with London severely affected
➢ Widespread diffuse domestic sources burning coal releasing large amounts of
smoke and SO2 through low level chimneys, combined with industrial emissions
• High concentrations of pollutants trapped below a temperature inversion
<100 m high
➢ Estimated daily smoke concentration of 4,500 µg m-3 and SO2 at 3,800 µg m-3
• Within 12 hours, large numbers showed symptoms of respiratory illness
➢ mortality rates up 230% over 2-weeks
➢ number of deaths for December put at 3,500 – 4,000
P. Brimblecome `The Great London Smog – Effects and Repercussions`, pp10-12 in NSCA, `The Clean Air Revolution
1952-20152. Marking 50 Years since the Great London Smog`, Clean Air and Environmental Protection, Vol.32, No.4,
Winter 2002.
D.Elsom `Smog – More than a London Problem`, pp13-18 in NSCA, `The Clean Air Revolution 1952-20152. Marking 50
Years since the Great London Smog`, Clean Air and Environmental Protection, Vol.32, No.4, Winter 2002.
3
Early Days

4. The response….
• Vociferous public concern and eventual Government action led
to the introduction of the first Clean Air Act. However:
➢ CAA was not passed until 1956 and not implemented until much later
➢ CAA only controlled smoke (industrial smoke plus domestic sector by
LA powers to designated Smoke Control Areas)
• Progress not fast enough to prevent the smog episode of 1962,
when weather conditions similar to the 1952 episode prevailed
• Ambient levels of both smoke and SO2 in urban areas did fall
significantly over the following years, but:
➢ wasn’t necessarily evidence of success of the CAA alone
➢ general move away from the use of solid fuel for heating, to the use of
gas (or even electricity) to heat premises
➢ general trend by the new, nationalised CEGB to move power
generation from city centres to much larger power stations with taller
stacks, located away from urban areas.
Williams M., The Policy Response to Improving Urban Air Quality, pp129-145, Air Quality in Urban Environments,
Issues in Environmental Science and Technology, Vol 28, Royal Society of Chemistry (2009)
4
Early Days
Early Days (continued)

5. The beginnings of a national monitoring network
• Working Party created in 1959 that led to the formation in 1961 of
the National Survey of Air Pollution to assess the benefits of the
CAA 1956 and guide future direction
• World`s first coordinated national air pollution monitoring network:
➢ run by the newly established Warren Spring laboratory (WSL), on behalf
of the then Department of the Environment
➢ monitoring and laboratory analysis was carried out by participating
organisations (mostly LAs), while WSL co-ordinated, processed the data
and summarised, and provided QA/QC
➢ In the first two decades of its existence was composed of around 1,200
monitoring sites measuring black smoke and sulphur dioxide
• In 1981, the survey was reduced in size, renamed the UK Smoke
and Sulphur Dioxide Network and continued until 2005
➢ to monitor compliance with the then relevant EC Directives on sulphur
dioxide and suspended particulate matter; and
➢ to provide a long-term database of smoke and SO2 measurements to
assess trends in concentration and spatial distribution in major population
centres throughout the UK
Williams M., The Policy Response to Improving Urban Air Quality, pp129-145, Air Quality in Urban Environments, Issues in
Environmental Science and Technology, Vol 28, Royal Society of Chemistry (2009)
5
Early Days
Early Days (continued)

6. Early Days (continued)
• Used the relatively cheap and simple smoke stain/ bubbler
method, standardised in BS1747: Part 3, 1969 (1986)
• The 8-port sampler was used, an instrument which provides
daily mean concentrations of suspended particulate (as
black smoke) and SO2 (as total acidity)
➢ Sampler draws a metered volume of air through a filter then
dilute, acidified hydrogen peroxide in a bubbler
➢ The solution is acidified, initially, to pH 4.5 so that strong acids
(primarily SO2) are absorbed in preference to weakly acidic
compounds such as carbon dioxide
➢ SO2 in the sampled air reacts with the peroxide to form sulphuric
acid in solution, increasing its acidity (decreasing the pH)
• Darkness of stain on cellulose filter measured by
reflectometer, then converted to µg m-3 International
Equivalent Standard Smoke using calibration curve
• The total amount of acid in the exposed solution is
determined by a back-titration to pH 4.5 using a standard
alkaline solution of di-sodium tetraborate. The titre allows
calculation of the ambient SO2 concentration
6
Early Days (continued)

7. Widening Monitoring Networks
7
Widening Monitoring Networks
Widening Monitoring Networks
Emerging understanding of photochemical smog
• A very different type of smog had been causing problems in the US and would widen our
understanding of air pollution effects, causes and atmospheric chemical interactions
➢ During the 1940s, Los Angeles began experiencing air pollution episodes causing serious eye and
nose irritation, coughing, nausea and shortness of breath
➢ occurred during warm, sunny conditions so were unlike the well-known winter London smogs
➢ High concentrations of fine particulates and nitrogen dioxide contributed to reduced visibility and so
encouraged the term “smog” to be applied
• The story of LA Smog (photochemical smog) is complex
➢ Initially a synthetic rubber plant was suspected source and was shut down but the smogs continued
➢ The sources of the primary pollutants, their reactions, the role of the hydroxyl radical and the fact that
there are multiple mobile polluters made understanding difficult
➢ the nature of the smog only began to be unravelled when Jan Haagen-Smit, a biochemist concerned
with crop damage who had the skill of identifying components of the air by smell, was able to identify
the presence of Criegee intermediates (products of ozonolysis) in the smog and hence say that it
was caused by ‘the action of sunlight and automotive vapours’
➢ in early 1970s, the hydroxyl radical identified as an essential component of photochemical smog
• The US Clean Air Act promulgated in 1970, setting standards for wider set of air pollutants.
RSC Environmental Chemistry Group Bulletin January 2012, on `Arie Jan Haagen-Smit and the History of Smog` given by Prof Peter Brimblecombe (UEA) at RSC
meeting Environmental Chemistry: A Historical Perspective, Burlington House, Oct 26th 2011.

8. Widening Monitoring Networks
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Widening Monitoring Networks
Widening Monitoring Networks
• In the UK, vehicle emissions were causing more complex pollution
episodes than earlier sources of traditional smog.
➢ Investigation of London Dec 1975 episode with daily smoke conc of 800
µg m-3 and SO2 at 1,200 µg m-3 indicated diesel vehicle emissions were
now the dominant source of the problem
• By the 1970s the UK and Europe began experiencing
photochemical smog episodes
➢ would later lead to increasingly stringent emission controls for vehicles
➢ monitoring stations set up to measure traffic-related pollutants in a small
number of locations, using the newly emerging automatic monitoring
techniques to record hourly NO and NO2, SO2, O3 and CO as well as PM
and lead.
• As well as WSL, networks were run by:
➢ Greater London Council (GLC) and its London Scientific Services (LSS)
▪ London was a key player from early on: the London County Council (LCC) had already set
up its own Committee of Inquiry on Air Pollution in 1953 in the wake of The Great Smog,
alongside the Government’s own Beaver Committee that would eventually lead to the
CAA in 1956
➢ Central Electricity Generating Board (CEGB) and its Central Electricity
Research Laboratory (CERL)
➢ and others

9. 9
Testing writing over pictures…
Widening Monitoring Networks (continued)
• Despite the increased importance of motor vehicles, industry –
and power generation in particular – remained substantial
pollution contributors
• The Central Electricity Generating Board (CEGB) had an
active programme of air pollution monitoring (carried out by
the Board`s regional Scientific Services Departments) around
major fossil-fuelled power stations (or groups of):
• Thames Estuary
• Eggborough
• Fiddler`s Ferry
• Ratcliffe
• Pembroke
• Fawley
• Most included PM (smoke), SO2, NO and NO2, O3 and CO
• Routine monitoring compared with WHO guidelines and EC
Directive air quality standards of the time set for [smoke and
SO2 from 1980 and NO2 from 1985
• Research and early model validation led by Central Electricity
Research Laboratories (CERL) at Leatherhead)
Widening Monitoring Networks)

10. • Ran from 1970s to 1990s
• Covered periods of controversy for the Board
➢ 1984 miners` strike (increased use of high S fuel oil)
➢ Late 1980s acid rain
• Large number of power stations
• Concerns over `plume reinforcement` during easterly winds
• Pollutants measured:
➢ Deposited dust – deposit gauge, gravimetric and SEM/EDAX
analysis
➢ Suspended PM (smoke and particle count/ size distribution),
➢ SO2 - automatic coulometric titration (later replaced by uv
fluorescence analysers)
➢ NO and NO2, - chemiluminescence analyser
➢ O3 – uv absorption analyser
➢ CO – NDIR analyser
➢ Met data – wind speed/direction, solar radiation
10
Widening Monitoring Networks
CEGB Thames Estuary Air Pollution Network
Widening Monitoring Networks (continued)

11. Widening Monitoring Networks
11
Widening Monitoring Networks
Current Government Network
• In 1987, the UK established an automatic urban monitoring network, to
monitor O3, NO2, SO2 and suspended particulate matter for compliance with
the emerging EC Directive limit values on air quality.
• Following commitments by the UK Government to expand urban monitoring
in the UK and improve public availability of air quality information, this
network subsequently expanded.
• In 1992, the then Department of Environment established an Enhanced
Urban Network (EUN), and in 1995, all statutory and other urban monitoring
was consolidated into one comprehensive programme.
• During the following five years, over 50 local authority sites were integrated
into the resulting network, including 14 of the London Air Quality Monitoring
Network sites.
• In 1998, the previously separate UK urban and rural automatic networks
were combined to form the current Automatic Urban and Rural Network
(AURN). The AURN is the most important and comprehensive automatic
national monitoring network in the country, which is made up of 127 sites,
across the UK.
• The graphs opposite show the increase in the number of sites and the total
hourly measurements made every year, since the commencement of
automatic air quality monitoring in the UK.
[https://uk-air.defra.gov.uk/networks/brief-history]

12. Widening Monitoring Networks
12
Let a Hundred Surveys Blooms
Let a Hundred Surveys Bloom
• From around the 1990s, ambient air quality surveys became more
widespread, facilitated by:
➢ Wider availability of reliable automatic instrumental techniques
➢ Easier data collection, processing and reporting
➢ Low-cost passive NO2 diffusion tube sampler (Palmes tube) – developed by
Edward Palmes and first used in early 1970s for monitoring gaseous pollutants
(SO2 then NO2). In regular UK use by 1980s
• Monitoring surveys now fulfilling a number of needs:
➢ Continuing the monitoring of compliance with EU limits and national air
quality standards
➢ LAQM Review and Assessment
➢ Monitoring for pollution control legislative and regulatory requirements,
e.g. EPR and its predecessors (WML Regs, PPC Regs), Part B.
➢ Planning
➢ Other reasons for carrying out ambient air quality monitoring, e.g.
assessing effectiveness of abatement/control measures; in response to a major
pollution incident; or in response to complaints, pressure groups or public
opinion.
• Palmes` Tube, Chemistry World, p.78, November 2016
• E.D. Palmes and A.F.Gunnison, Personal monitoring device for gaseous contaminants, Journal of American Industrial Hygiene
Association, 34, 78, 1973).

13. Strategies for Monitoring Around Individual Sites
• Useful guidance on developing a suitable monitoring strategy
around individual regulated sites is given by the Environment
Agency in its “M” series (monitoring) Technical Guidance:
• M8 Environmental Monitoring Strategy – Ambient Air
➢ originally published in 2000
➢ 2011 saw an updated version published, that incorporated the formerly
separate M9 (on ambient air monitoring methods)
• More specific guidance for waste facilities provided in the
Environment Agency Technical Guidance Note M17
➢ limited to particulates and dusts
➢ originally published in 2004 and then revised/ updated in 2013
• To be technically valid and cost effective, the objectives of the
proposed monitoring programme should be clearly defined at
the outset.
• This allows the design of a monitoring strategy to meet these
needs. The key issues are summarised in the next slide.
13
Monitoring Strategies

14. Strategies for Monitoring Around Individual Sites
14
Monitoring Strategies
What?
• What parameter(s) to measure? In many cases this may be
obvious, but in others it merits careful consideration.
When?
• When to sample and for how long? Should sampling be
continuous or periodic? Factors to consider are:
➢ what temporal resolution is required; and
➢ is there an environmental quality standard (EQS) with a defined averaging
period against which the data will be compared?
➢ Duration v emissions pattern, diurnal met cycles, seasonal met changes
Where?
• Where to sample? Two factors to consider are:
➢ the locations of monitoring positions relative to the emission source and
different sensitive receptors, and the spatial resolution required
➢ suitability criteria for individual sampling sites, e.g. position relative to local
emission sources and any interfering effects.
How?
• Selection of measurement method involves an appraisal of cost
versus performance,
➢ limits of detection, sensitivity, speed of instrument response, susceptibility
to interfering species and the overall uncertainty of the measurement.

15. Thank You
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