The Deptford Bridge area includes several major traffic intersections that are key thoroughfares for South East London. There are high levels of automobile, HGV, bus and related traffic in the area, and idling traffic and buses are frequently spotted near the Deptford Bridge DLR station. Citizen data reveals that pollution levels are especially high due to the arterial network and traffic intersections in this area.
This data story details below how citizen data, weather data and local observations reveal these specific pollution patterns. Drawing on workshops with local residents, the data story also suggests how best to address the problem, from planning for improved transport, to reducing emission levels at major traffic intersections, and creating green buffers between roadways and housing.
Deptford Bridge is a residential, commercial and industrial area near the Deptford Bridge DLR station in the Borough of Lewisham, South East London. The monitoring area is located at the busy intersections of Greenwich High Road and New Cross Road, and Deptford Church Street with New Cross Road.
Dustbox monitors are placed in a number of sites throughout Deptford Bridge as illustrated in the map below. Dustbox 151 is located on the northeastern corner of the junction, where New Cross Road (A2) and Deptford Church Street (A2209) intersect. Dustbox 151 is located approximately 6 metres from the roadside on a second-storey balcony facing an internal courtyard. Dustbox 138 is located on a third-floor balcony near the Deptford Bridge DLR station, which lies approximately 55 metres to the east. Dustbox 138 is on the southwest side of Deptford Bridge (A2) at the intersection with Greenwich High Road (A206).
Deptford Church Street (A2209) runs north-south through the centre of the monitoring area. New Cross Road (A2) runs east-west through the centre of the monitoring area. To the east of the monitoring area is the DLR rail line that runs from Deptford Bridge to Greenwich.
Currently, sites to the north of Deptford Bridge at Creekside are under construction for residential development. Two miles to the northeast of the site is Blackwall Tunnel Southern Approach, and just over five miles to the northeast is London City Airport.
Local sources of particulate pollution
The above map highlights possible emissions sources in the Deptford Bridge area, primarily related to road transportation. This area is home to a large junction that controls traffic flow between four major A-roads; New Cross Road/Deptford Bridge (A2), Brookmill Road (A2210) and Deptford Church Street (A2209), as well as Greenwich High Road (A206). Queues of idling traffic are often visible as vehicles wait for traffic lights to change. Below the DLR train station is a bus stop and turnaround where buses often park and idle while waiting (although more recently hybrid buses have been deployed in the area for some routes). In addition, there is ongoing construction to the north of both monitors on the Faircharm Quarter site at Creekside.
London-wide, regional and global sources of particulate pollution
Particulate matter sources in London can be attributed to a broad range of emissions. Within London, PM2.5 from transport (particularly diesel), industry, construction, cooking and heating all contribute significantly to London-wide levels. A significant amount of PM2.5 emissions also comes from heavy industry and agriculture outside the UK, particularly France, Belgium, the Netherlands, Luxembourg, Germany and Poland. These emissions are thought to account for an urban background of approximately 10 µg/m3. The importance of these transboundary effects of PM2.5 emissions from outside of the UK on the total London PM2.5 can vary between 40% to 80% daily depending on weather conditions. When long-range pollution episodes do occur in London, they are generally carried on easterly winds. There are a number of global emissions, events and practices that contribute particulate matter to the total London PM2.5, including fuel production, industrial and domestic combustion, transportation, waste disposal, and agriculture, although these are harder to quantify.
Participants have emphasized just how busy the New Cross Road (A2) junctions are throughout daytime, afternoon and evening periods. They have noted that the junction seems visibly less congested only at around midnight. Participants have described the high number of HGVs that use this route (particularly vehicles from European hauliers). During the collection of supplementary data, we observed idling at a bus stopping point off Deal’s Gateway road (A206). Participants have observed that changes to the traffic light timing causes traffic to idle for long periods at the intersection of Friendly Street and the A2210. However, these changes also help to make the walkways more navigable by pedestrians and cyclists.
Other observations include unpleasant, intermittent odours from the Ravensbourne River. One local resident has made complaints to Lewisham and Greenwich councils due to visible floating debris and oil fluid pollution in the River.
II. Is there evidence of a problem?
The Dustbox device used to monitor PM2.5 particles is an “indicative” monitor. This means that measurements can give an indication of pollutant concentrations, but cannot be directly compared with national and international guidelines and standards in an “official” or regulatory sense. Despite this, indicative monitoring is a well-established method within atmospheric science for carrying out initial surveys of an area to establish whether a potential problem merits further investigation. Indicative monitors are also becoming increasingly available for citizen-based air-quality monitoring, similar to this study. Where possible, the Dustboxes were co-located at the start and the end of the study to account for differences in the sensors and drift during the monitoring period.
Indicative daily mean concentrations of PM2.5 are shown as a time-series chart in Figure 1. This figure shows an extract of the monitoring data for the entire monitoring period from the Dustbox 138 site and Dustbox 151 site presented as 24-hourly mean concentrations of PM2.5.
As shown in Figure 1, the World Health Organisation (WHO) guideline of 25 µg/m3 for 24-hour daily mean concentration of PM2.5 is exceeded on a number of occasions at Dustbox 138 and 151, and this pattern is repeated in the surrounding Dustboxes, suggesting that further investigation may be merited.
However, it is important to determine whether these breaches were caused by “local” sources of pollution close to the sensor (i.e., within 300 meters), or by regional sources affecting the whole area. Local sources often augment regional sources, which can be revealed as a spike on top of a hump. In a general sense, this regional-local pattern occurs because pollution mixes in the atmosphere as it travels away from a source, smoothing the speed of changes in concentrations.
Figure 2 shows an extract of the monitoring data from the Dustbox 138 site presented as hourly mean concentrations of PM2.5. Measurements from Dustbox 108, a monitor in New Cross Gate, are shown for comparison.
Regional sources of pollution again appear as broad “humps” of elevated pollution affecting both sites, for example, in the period between 5 to 7 April 2017. Local sources of pollution appear as short “spikes” typically affecting only one or the other site, for example, 12 to 13 April 2017 at Dustbox 138.
Figure 2 therefore indicates that there are significant local sources of particulate pollution elevating ambient concentrations well above those caused by regional sources across the monitoring period.
There are many possible sources of pollution in the area and we have to look at the measurements more closely to see if we can deduce what activities are causing these spikes. Knowing the source of pollution is important as some activities produce more toxic particulate matter than others, and actions to mitigate sources should be targeted to the cause of the problem.
III. Characterizing the problem
When is the source most evident?
Using time plots, it is possible to analyse time of day and day of week, as well as month, when pollution levels are elevated. Time plots aggregate PM2.5 concentrations according to time, so that key patterns such as rush hours and traffic, as well as possible construction or industry sources, along with regional pollution events due to seasonal variation, are evident.
Figure 3 investigates when these elevated levels in pollution occur by grouping concentrations by hour, month and day of the week. Sources of pollution related to commuter or transit traffic typically show peaks in concentrations coincidental with peaks in traffic flow, i.e., morning and evening rush hour with notably lower levels at night and on Sundays. This can also be seen in Figure 3, where there is evidence of early morning and evening peaks.
These charts can be used to match patterns in the occurrence of spikes with working patterns of particulate-generating activities in the area. Figure 3 shows that on most days there are elevated levels in the early hours of the morning and from midday through the evening at the Dustbox 138 site. However it is clear the morning peaks are around 5 am, perhaps suggesting higher levels of particulates from earlier traffic, such as deliveries or construction crews.
Figure 4 groups concentrations by hour, month and day of the week for Dustbox 151. As this Dustbox came online later, Figure 4 shows a different date range to Figure 5, so these plots are not directly comparable. Figure 4 shows a large morning peak at around 4 am and a lower afternoon peak from approximately 5 pm. This profile may correspond to transport-related emissions sources. Like Dustbox 138 readings, shown in Figure 3, levels do not go down much in the evening, from 5 pm onwards. Levels are lowest on Saturday and Sunday as would be expected with a commuting pattern. Levels are highest on Thursdays as shown in Figure 3 for Dustbox 138, something that may merit further investigation.
In a general sense, it should be noted that the weather plays a large role in particulate levels. For example, dust tends to be dispersed more slowly during the hours of darkness, as vertical and horizontal wind speeds are generally lower. This phenomenon may skew charts somewhat.
Which direction is PM2.5 coming from?
Wind direction has a considerable influence on pollution measurements. A sensor will only record emissions from a particular source or activity if the wind blows it from the source towards the sensor. Therefore, we can investigate where a source of pollution is likely to be located by plotting wind direction against pollution concentrations. Figure 5 shows how pollutant concentrations at Dustbox 138 site are influenced by wind direction. It shows the highest pollution levels are from a north to northeast direction (0O to 70O), with also regular high readings from the southwest (240O).
A polar plot, as shown in the figures below, is a more intuitive way of looking at this relationship. This shows colour contours of pollutant concentrations in relation to wind direction and wind speed, with zero wind in the centre, increasing up to 20 metres per second (ms-1) at the outer ring. The highest mean concentrations are shown in red, the lowest are in blue.
Figures 6a and 6b highlight the fact that, on average, the most frequent high concentrations of PM2.5 are recorded at Dustbox 138 and Dustbox 108 during northeasterly winds. As both sites show a source to the east there may be a regional source of air pollution in that direction, which is detected by most sensors in the area. Dustbox 108 is exposed to similar emissions sources from New Cross Road, and displays comparably high levels to 138.
Under which weather conditions are PM2.5 levels most evident?
Different sources of pollution will act in distinct ways according to the weather. For example, windblown dust will primarily occur during dry, windy conditions. Sometimes, you can learn about a source by characterizing this weather-related behaviour.
Figure 7 indicates that the highest readings for Dustbox 138 occur at levels of relatively high humidity, over 75%. During higher humidity there would be fewer occurrences of wind-blown dust. This suggests that emission sources are localised.
IV. Drawing the evidence together
Using the tools provided through the Citizen Sense Airsift Dustbox Data Analysis Toolkit, we have characterized sources of particulate pollution detected by the Dustbox 138 and Dustbox 151 Deptford Bridge monitors as follows:
- While regional sources of pollution were detected, there was clear evidence of additional local source or sources, often at high levels.
- The strongest local source(s) appear to be to the northeast of the Dustbox 138 site. Due to the irregularity of the Dustbox 151 data collection, it was difficult to establish a clear direction for the source of emissions.
- There is some evidence of local emissions combining with city-wide emissions. These local emission sources could travel from the A2 in both directions, Deptford Church Street, as well as the occasional idling of bus traffic. Dustbox 108 in New Cross Gate shows a very similar pattern to 138, suggesting the A2 flow is impacting the monitors in similar ways.
- The local source is strongest during the early hours before 6 am, and in the afternoon/early evening. It is therefore also likely to be related to delivery, construction crew and commuter road traffic.
- PM2.5 levels are unlikely to be related to re-suspended or wind-blown dust due to low wind speeds and high humidity at which higher concentrations occur.
- The high peaks shown in late January can be accounted for as two periods of poor air quality across London, beginning 19 January 2017 and 23 January 2017. These pollution episodes were partly due to cold, settled weather slowing the dispersion of local pollutants.
In relation to the evidence and findings from the Dustbox citizen monitoring study, preliminary actions are proposed here that take into account the neighbourhood context and existing community organisations and initiatives. The key areas for addressing air pollution include transport, construction, green infrastructure, and additional monitoring. These actions have been developed in consultation with monitoring participants and local area residents. Some actions are shared across the 7 data stories, while others are specific to this data story location:
Traffic and transport
- Building on the Lewisham Council Local Implementation Plan, develop a traffic management plan traffic for Deptford and New Cross in order to identify areas to improve pedestrian, cycle and public transport routes, and to understand the potential impact of the Ultra Low Emission Zone (ULEZ) on the area. Address the impact of new development and increasing population in the area, with a realistic projection of the likely numbers of new cars that will be in the area.
- Encourage the use of the River Thames as an alternative transport route for goods, construction and commuters and to reduce road traffic. However, require diesel-free or clean ship fuel to be used by vessels on the River Thames.
- Encourage and support transportation pilots to trial improved roadway design and circulation.
- Improve cycling opportunities in the area, and separate vehicle traffic from cycling traffic, including through the use of car-free green corridors.
- Post signs to encourage no idling. Signs that read ‘Turn your engine off’ and include images of people in pollution masks are more effective than text-only signs that read ‘No idling’.
- Encourage hybrid vehicles and busses, and investigate ways to integrate solar panels into the design of buses and bus stops. Allow for electric vehicle charging points to be requested by residents as part of community transport initiatives, and not only by those who own an electric vehicle.
Construction and development
- Ensure the fulfillment of Air Quality Impact Assessments (AQIAs), both at the planning and implementation stage of new developments, in order to accurately gauge the effect of construction with new developments. Develop adequate monitoring and compliance mechanisms for possible breaches of AQIAs.
- Develop planning and regulatory mechanisms for addressing the accumulative effects from construction and new developments. Impacts from construction and new development can include air pollution from demolition and siteworks, traffic during construction, and higher densities of buildings, people and traffic from new developments. Require that all new developments are ‘air quality neutral’, and ensure transparent and legible processes are in place for ensuring neutrality.
- Join up traffic planning across existing and new developments to facilitate walking, cycling and public transport. Design for neighbourliness with pedestrianized and play streets.
- Encourage cross-borough collaboration on construction and new development. Pending developments at the edge of Deptford, including the Silvertown Tunnel, the Enderby Wharf cruise ferry terminal, the Knight Dragon development at North Greenwich peninsula, and the Royal Docks Enterprise Zone could have a considerable effect on traffic in the area, especially along Evelyn Street.
- Include plans for managing construction traffic as part of providing planning approval for new developments. Ensure that construction traffic does not exceed set levels so as to avoid additional local pollution events.
- Address and prevent the loss of green space and public space due to new development. Green spaces can have a significant mitigating effect on air quality, and also provide a lower emission space in which people can spend time outdoors.
- Provide indicators for how to measure the effectiveness of dust measurement plans and practices at construction sites. Working with the London Low Emission Construction Partnership, provide mechanisms for enforcing dust management plans when they are not adhered to, and for reporting violations.
- Require an audit of green spaces in the borough, including an assessment of the suitability of green space as green infrastructure in relation to air pollution mitigation, and in relation to improving walkability and cycleability. Using existing London tree mapping resources, develop a tree plan for planting in the borough, and in relation to best guidance for trees suitable for minimising and lowering air pollution.
- Plant trees and preserve green spaces in relation to air quality guidance for vegetation.
- Investigate opportunities for planting air quality enhancing vegetation in existing neighbourhood green spaces, as well as at schools, hospitals, playgrounds and key community sites.
- Provide guidance on planting for air quality, including preferred species, optimal planting arrangements, and best practices for maintenance.
- Host air pollution monitoring and awareness events in green spaces to raise awareness about the importance of urban design and planning in relation to mitigating and prevent air pollution.
Air quality monitoring
- Prioritise air-quality audits of emission levels at Deptford and New Cross schools, in line with the Mayor of London’s initiative. Expand and provide courses in schools for children to learn about air quality and to undertake air quality monitoring in their local area, including promoting actions for reducing air pollution such as walking to school.
- Provide resources for community organisations and residents to continue to monitor air quality over time in order to assess improvements from preventative and mitigating actions.
- Provide resources to undertake speciation to understand the composition and sources of particulate matter, including from roads, construction and other sources.
- Develop protocols and channels for citizens to provide monitoring data to local and GLA environmental health and planning officers, and require officers to act on identified exceedances in relation to air quality guidelines.
The Citizen Sense project is led by Professor Jennifer Gabrys. These data stories were developed working in collaboration with Helen Pritchard and Dr Lara Houston. Thanks are due to our collaborators including:
Dr Benjamin Barratt and Khadija Jabeen at the Environmental Research Group, King’s College, University of London contributed to co-location and calibration of the Dustboxes, and Dr Barratt contributed to the analysis of the data stories.
The Citizen Sense Dustbox included contributions to the printed circuit board design, which was developed in collaboration with Adrian McEwen of MCQN Ltd, and to the ceramic housing, which was rendered into 3D-printable format in collaboration with materials designer Francesca Perona.
Special thanks are due to the participants and residents in southeast London who contributed to the development and testing of the Dustbox monitoring kit, as well as to the collection and analysis of data, and communication of results to wider publics and regulators. For more information on project contributors, see Citizen Sense People.
These data stories are generated using the Citizen Sense Airsift Data Analysis Toolkit, which was developed to allow for citizen-led interpretation of datasets. The core data available for interpretation is the Dustbox PM2.5 sensor data. The Airsift toolkit also brings in air quality data from select sites in the London Air Quality Network (LAQN) for comparison with the citizen data.
In order to blur the exact monitoring locations, the monitoring locations are shown with large blue circles to indicate the approximate monitoring location. Additional citizen monitoring locations are anonymous, and are not included on the Airsift map.
At the start of the monitoring period, the Dustboxes were co-located with the Marylebone Atmospheric Observatory, and a scaling factor was applied to calibrate the devices. Because the sensors were co-located and calibrated during a time of low to moderate pollution, the scaling factor could slightly amplify higher readings in relation to the LAQN readings. However, this would require further testing to demonstrate, since when comparing Dustbox levels with nearby LAQN levels (where available), readings are often comparable.
The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 313347, “Citizen Sensing and Environmental Practice: Assessing Participatory Engagements with Environments through Sensor Technologies.”
To cite this data story, please use the reference: Citizen Sense (2017) “Deptford Bridge,” Deptford Data Stories, 14 November. Available at: https://datastories-deptford.citizensense.net/deptford-bridge.
This Deptford Bridge data story is also available to download as a PDF.