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NOx is a pervasive pollutant in urban environments. This review assesses the current state of the art of photocatalytic oxidation materials, designed for the abatement of nitrogen oxides (NOx) in the urban environment, and typically, but not exclusively based on titanium dioxide (TiO2). Field trials with existing commercial materials, such as paints, asphalt and concrete, in a range of environments including street canyons, car parks, tunnels, highways and open streets, are considered in-depth. Lab studies containing the most recent developments in the photocatalytic materials are also summarised, as well as studies investigating the impact of physical parameters on their efficiency. It is concluded that this technology may be useful as a part of the measures used to lower urban air pollution levels, yielding ∼2% NOx removal in the immediate area around the surface, for optimised TiO2, in some cases, but is not capable of the reported high NOx removal efficiencies >20% in outdoor urban environments, and can in some cases lower air quality by releasing hazardous by-products. However, research into new material is ongoing. The reason for the mixed results in the studies reviewed, and massive range of removal efficiencies reported (from negligible and up to >80%) is mainly the large range of testing practices used. Before deployment in individual environments site-specific testing should be performed, and new standards for lab and field testing should be developed. The longevity of the materials and their potential for producing hazardous by-products should also be considered.
Hugo Russell; Louise Frederickson; Ole Hertel; Thomas Ellermann; Steen Jensen. A Review of Photocatalytic Materials for Urban NOx Remediation. Catalysts 2021, 11, 675 .
AMA StyleHugo Russell, Louise Frederickson, Ole Hertel, Thomas Ellermann, Steen Jensen. A Review of Photocatalytic Materials for Urban NOx Remediation. Catalysts. 2021; 11 (6):675.
Chicago/Turabian StyleHugo Russell; Louise Frederickson; Ole Hertel; Thomas Ellermann; Steen Jensen. 2021. "A Review of Photocatalytic Materials for Urban NOx Remediation." Catalysts 11, no. 6: 675.
Formaldehyde (HCHO) and nitrogen dioxide (NO2) often co-exist in urban environments at levels that are hazardous to health. There is a demand for a solution to the problem of their combined removal. In this paper, we investigate catalysts, adsorbents and composites for their removal efficiency (RE) toward HCHO and NO2, in the context of creating a pollution control device (PCD). Proton-transfer-reaction mass spectrometry and cavity ring-down spectrometry are used to measure HCHO, and chemiluminescence and absorbance-based monitors for NO2. Commercially available and lab-synthesized materials are tested under relevant conditions. None of the commercial adsorbents are effective for HCHO removal, whereas two metal oxide-based catalysts are highly effective, with REs of 81 ± 4% and 82 ± 1%, an improvement on previous materials tested under similar conditions. The best performing material for combined removal is a novel composite consisting of a noble metal catalyst supported on a metal oxide, combined with a treated active carbon adsorbent. The composite is theorized to work synergistically to physisorb and oxidize HCHO and chemisorb NO2. It has an HCHO RE of 72 ± 2% and an NO2 RE of 96 ± 2%. This material has potential as the active component in PCDs used to reduce personal pollution exposure.
Hugo S. Russell; James Bonomaully; Rossana Bossi; Magdalena E. G. Hofmann; Hasse C. Knap; Jakob B. Pernov; Marten In ‘T Veld; Matthew S. Johnson. Novel Materials for Combined Nitrogen Dioxide and Formaldehyde Pollution Control under Ambient Conditions. Catalysts 2020, 10, 1040 .
AMA StyleHugo S. Russell, James Bonomaully, Rossana Bossi, Magdalena E. G. Hofmann, Hasse C. Knap, Jakob B. Pernov, Marten In ‘T Veld, Matthew S. Johnson. Novel Materials for Combined Nitrogen Dioxide and Formaldehyde Pollution Control under Ambient Conditions. Catalysts. 2020; 10 (9):1040.
Chicago/Turabian StyleHugo S. Russell; James Bonomaully; Rossana Bossi; Magdalena E. G. Hofmann; Hasse C. Knap; Jakob B. Pernov; Marten In ‘T Veld; Matthew S. Johnson. 2020. "Novel Materials for Combined Nitrogen Dioxide and Formaldehyde Pollution Control under Ambient Conditions." Catalysts 10, no. 9: 1040.
In this pilot study, low-cost air pollution sensor nodes were fitted in waste removal trucks, hospital vans and taxis to record drivers’ exposure to air pollution in Central London. Particulate matter (PM 2 . 5 and PM 10 ), CO 2 , NO 2 , temperature and humidity were recorded in real-time with nodes containing low-cost sensors, an electrochemical gas sensor for NO 2 , an optical particle counter for PM 2 . 5 and PM 10 and a non-dispersive infrared (NDIR) sensor for CO 2 , temperature and relative humidity. An intervention using a pollution filter to trap PM and NO 2 was also evaluated. The measurements were compared with urban background and roadside monitoring stations at Honor Oak Park and Marylebone Road, respectively. The vehicle records show PM and NO 2 concentrations similar to Marylebone Road and a higher NO 2 -to-PM ratio than at Honor Oak Park. Drivers are exposed to elevated pollution levels relative to Honor Oak Park: 1.72 μ g m − 3 , 1.92 μ g m − 3 and 58.38 ppb for PM 2 . 5 , PM 10 , and NO 2 , respectively. The CO 2 levels ranged from 410 to over 4000 ppm. There is a significant difference in average concentrations of PM 2 . 5 and PM 10 between the vehicle types and a non-significant difference in the average concentrations measured with and without the pollution filter within the sectors. In conclusion, drivers face elevated air pollution exposure as part of their jobs.
Louise Frederickson; Shanon Lim; Hugo Russell; Szymon Kwiatkowski; James Bonomaully; Johan Schmidt; Ole Hertel; Ian Mudway; Benjamin Barratt; Matthew Johnson. Monitoring Excess Exposure to Air Pollution for Professional Drivers in London Using Low-Cost Sensors. Atmosphere 2020, 11, 749 .
AMA StyleLouise Frederickson, Shanon Lim, Hugo Russell, Szymon Kwiatkowski, James Bonomaully, Johan Schmidt, Ole Hertel, Ian Mudway, Benjamin Barratt, Matthew Johnson. Monitoring Excess Exposure to Air Pollution for Professional Drivers in London Using Low-Cost Sensors. Atmosphere. 2020; 11 (7):749.
Chicago/Turabian StyleLouise Frederickson; Shanon Lim; Hugo Russell; Szymon Kwiatkowski; James Bonomaully; Johan Schmidt; Ole Hertel; Ian Mudway; Benjamin Barratt; Matthew Johnson. 2020. "Monitoring Excess Exposure to Air Pollution for Professional Drivers in London Using Low-Cost Sensors." Atmosphere 11, no. 7: 749.
Airborne particulate matter (PM) exposure has been identified as a key environmental risk factor, associated especially with diseases of the respiratory and cardiovascular system and with almost 9 million premature deaths per year. Low-cost optical sensors for PM measurement are desirable for monitoring exposure closer to the personal level and particularly suited for developing spatiotemporally dense city sensor networks. However, questions remain over the accuracy and reliability of the data they produce, particularly regarding the influence of environmental parameters such as humidity and temperature, and with varying PM sources and concentration profiles. In this study, eight units each of five different models of commercially available low-cost optical PM sensors (40 individual sensors in total) were tested under controlled laboratory conditions, against higher-grade instruments for: lower limit of detection, response time, responses to sharp pollution spikes lasting
Florentin Michel Jacques Bulot; Hugo Savill Russell; Mohsen Rezaei; Matthew Stanley Johnson; Steven James Johnston Ossont; Andrew Kevin Richard Morris; Philip James Basford; Natasha Hazel Celeste Easton; Gavin Lee Foster; Matthew Loxham; Simon James Cox. Laboratory Comparison of Low-Cost Particulate Matter Sensors to Measure Transient Events of Pollution. Sensors 2020, 20, 2219 .
AMA StyleFlorentin Michel Jacques Bulot, Hugo Savill Russell, Mohsen Rezaei, Matthew Stanley Johnson, Steven James Johnston Ossont, Andrew Kevin Richard Morris, Philip James Basford, Natasha Hazel Celeste Easton, Gavin Lee Foster, Matthew Loxham, Simon James Cox. Laboratory Comparison of Low-Cost Particulate Matter Sensors to Measure Transient Events of Pollution. Sensors. 2020; 20 (8):2219.
Chicago/Turabian StyleFlorentin Michel Jacques Bulot; Hugo Savill Russell; Mohsen Rezaei; Matthew Stanley Johnson; Steven James Johnston Ossont; Andrew Kevin Richard Morris; Philip James Basford; Natasha Hazel Celeste Easton; Gavin Lee Foster; Matthew Loxham; Simon James Cox. 2020. "Laboratory Comparison of Low-Cost Particulate Matter Sensors to Measure Transient Events of Pollution." Sensors 20, no. 8: 2219.