Search

Measurements of CO 2 and counting of occupants were carried out in 37 public bus trips during commuting rush hours in Barcelona (NE Spain) with the aim of evaluating parameters governing ventilation inside the vehicles and proposing actions to improve it. The results show that CO 2 concentrations (1039 and 934 ± 386 ppm, as average and median, during rush hours but with average reduced occupancy due to the fair to be infected by SARS-CoV-2 during the measurement period, and measured in the middle of the busses) are in the lower range of values recorded in the literature for public buses, however an improvement in ventilation is required in a significant proportion of the journeys. Thus, we found better ventilation in the older Euro 3+ (retrofitted with filter traps and selective catalytic reduction) and Euro 5 buses (average 918 ± 257 ppm) than in the hermetically closed new Euro 6 ones (1111 ± 432 ppm). The opening of the windows in the older buses yielded higher ventilation rates (778 ± 432 ppm). The opening of all doors at all stops increases the ventilation by causing a fall in concentrations of 200–350 ppm below inter-stop concentrations, with this effect typically lasting 40–50 s in the hermetically closed new Euro 6 hybrid buses. Based on these results a number of recommendations are offered in order to improve ventilation, including measurement of CO 2 and occupancy, and installation of ventilation fans on the top of the hermetically closed new buses, introducing outdoor air when a given concentration threshold is exceeded. In these cases, a CO 2 sensor installed in the outdoor air intake is also recommended to take into account external CO 2 contributions. • Measurements of CO 2 were carried out in public buses during commuting rush hours. • An evaluation of factors governing ventilation inside the vehicles was carried out, and actions to improve it were suggested. • The opening of the windows in the older buses yielded higher ventilation rates. • The opening of all doors at all stops increases the ventilation by causing a fall in concentrations lasting 40–50 s. • Measurement of CO 2 and occupancy and installation of roof ventilation fans in the hermetically closed new buses. [ABSTRACT FROM AUTHOR]

Vehicle interior air quality (VIAQ) was investigated inside 14 diesel/non-diesel taxi pairs operating simultaneously and under normal working conditions over six weekday hours (10.00–16.00) in the city of Barcelona, Spain. Parameters measured included PM 10 mass and inorganic chemistry, ultrafine particle number (N) and size, lung surface deposited area (LDSA), black carbon (BC), CO 2 , CO, and a range of volatile organic compounds (VOCs). Most taxi drivers elected to drive with windows open, thus keeping levels of CO 2 and internally-generated VOCs low but exposing them to high levels of traffic-related air pollutants entering from outside and confirming that air exchange rates are the dominant influence on VIAQ. Median values of N and LDSA (both sensitive markers of VIAQ fluctuations and likely health effects) were reduced to around 104 #/cm3 and < 20 µm2/cm3 respectively under closed conditions, but more than doubled with windows open and sometimes approached 105 #/cm3 and 240 µm2/cm3. In exceptional traffic conditions, transient pollution peaks caused by outside infiltration exceeded N = 106 #/cm3 and LDSA= 1000 µm2/cm3. Indications of self-pollution were implicated by higher BC and CO levels, and larger UFP sizes, measured inside diesel taxis as compared to their non-diesel pair, and the highest concentrations of CO (>2 ppm) were commonly associated with older, high-km diesel taxis. Median PM 10 concentrations (67 µg/m3) were treble those of urban background, mainly due to increased levels of organic and elemental carbon, with source apportionment calculations identifying the main pollutants as vehicle exhaust and non-exhaust particles. Enhancements in PM 10 concentrations of Cr, Cu, Sn, Sb, and a "High Field Strength Element" zircon-related group characterised by Zr, Hf, Nb, Y and U, are attributed mainly to the presence of brake-derived PM. Volatile organic compounds display a mixture which reflects the complexity of traffic-related organic carbon emissions infiltrating the taxi interior, with 2-methylbutane and n-pentane being the most abundant VOCs, followed by toluene, m-xylene, o-xylene, 1,2,4-trimethylbenzene, ethylbenzene, p-xylene, benzene, and 1,3,5-trimethylbenzene. Internally sourced VOCs included high monoterpene concentrations from an air freshener, and interior off-gassing may explain why the youngest taxi registered the highest content of alkanes and aromatic compounds. Carbon dioxide concentrations quickly climbed to undesirable levels (>2500 ppm) under closed ventilation conditions and could stay high for much of the working day. Taxi drivers face daily occupational exposure to traffic-related air pollutants and would benefit from a greater awareness of VIAQ issues, notably the use of ventilation, to encourage them to minimise possible health effects caused by their working environment. • Main PM 10 sources inside taxis are vehicle exhaust and non-exhaust (wear) particles. • PM 10 averaged 67 µg/m3 and enriched in Cr, Cu, Sn, Sb, Zr attributed to brake wear. • Self-pollution inside (especially older) diesel taxis raises BC, CO, and UFP size. • VOCs inside taxi dominated by 2-methylbutane, n-pentane and other exhaust emissions. • Intelligent use of taxi ventilation reduces infiltration and build-up of pollutants. [ABSTRACT FROM AUTHOR]

Sampling campaigns using the same equipment and methodology were conducted to assess and compare the air quality at three South European subway systems (Barcelona, Athens and Oporto), focusing on concentrations and chemical composition of PM 2.5 on subway platforms, as well as PM 2.5 concentrations inside trains. Experimental results showed that the mean PM 2.5 concentrations widely varied among the European subway systems, and even among different platforms within the same underground system, which might be associated to distinct station and tunnel designs and ventilation systems. In all cases PM 2.5 concentrations on the platforms were higher than those in the urban ambient air, evidencing that there is generation of PM 2.5 associated with the subway systems operation. Subway PM 2.5 consisted of elemental iron, total carbon, crustal matter, secondary inorganic compounds, insoluble sulphate, halite and trace elements. Of all metals, Fe was the most abundant, accounting for 29–43% of the total PM 2.5 mass (41–61% if Fe 2 O 3 is considered), indicating the existence of an Fe source in the subway system, which could have its origin in mechanical friction and wear processes between rails, wheels and brakes. The trace elements with the highest enrichment in the subway PM 2.5 were Ba, Cu, Mn, Zn, Cr, Sb, Sr, Ni, Sn, Co, Zr and Mo. Similar PM 2.5 diurnal trends were observed on platforms from different subway systems, with higher concentrations during subway operating hours than during the transport service interruption, and lower levels on weekends than on weekdays. PM 2.5 concentrations depended largely on the operation and frequency of the trains and the ventilation system, and were lower inside the trains, when air conditioning system was operating properly, than on the platforms. However, the PM 2.5 concentrations increased considerably when the train windows were open. The PM 2.5 levels inside the trains decreased with the trains passage in aboveground sections. [ABSTRACT FROM AUTHOR]

Access to detailed comparisons in air quality variations encountered when commuting through a city offers the urban traveller more informed choice on how to minimise personal exposure to inhalable pollutants. In this study we report on an experiment designed to compare atmospheric contaminants inhaled during bus, subway train, tram and walking journeys through the city of Barcelona. Average number concentrations of particles 10-300 nm in size, N , are lowest in the commute using subway trains ( N <2.5×10 4 part. cm −3 ), higher during tram travel and suburban walking (2.5×10 4 cm −3 < N <5.0×10 4 cm −3 ), and highest in diesel bus or walking in the city centre ( N >5.0×10 4 cm −3 ), with extreme transient peaks at busy traffic crossings commonly exceeding 1.0×10 5 cm −3 and accompanied by peaks in Black Carbon and CO. Subway particles are coarser (mode 90 nm) than in buses, trams or outdoors (<70 nm), and concentrations of fine particulate matter (PM 2.5 ) and Black Carbon are lower in the tram when compared to both bus and subway. CO 2 levels in public transport reflect passenger numbers, more than tripling from outdoor levels to >1200 ppm in crowded buses and trains. There are also striking differences in inhalable particle chemistry depending on the route chosen, ranging from aluminosiliceous at roadsides and near pavement works, ferruginous with enhanced Mn, Co, Zn, Sr and Ba in the subway environment, and higher levels of Sb and Cu inside the bus. We graphically display such chemical variations using a ternary diagram to emphasise how “air quality” in the city involves a consideration of both physical and chemical parameters, and is not simply a question of measuring particle number or mass. [ABSTRACT FROM AUTHOR]