OBTENCIÓN DE EXTRACTOS

The sheltered car park in Christchurch was situated at the centre of town. Since it was a public car park, there was increased traffic leaving and entering the car park, especially at peak times. The underground car park in Auckland, on the other hand, was not accessible to the general public, but serviced businesses and organisations in the area. While the time spent in the Christchurch car park averaged less than four minutes, just over five

minutes were spent in the Auckland one. Both periods of time were considerably shorter than the time spent on the actual car drive (average time spent on the Christchurch car rides totaled 17.52 minutes, and on the Auckland car journeys average time spent was 38.10 minutes).

The mean CO exposure in the car park in Christchurch averaged more in the car park than the journeys. The maximum level in the car park was highest compared to other segments (54.74 ppm). This is congruent to results in other studies obtained in CO exposure studies done in car parks. Papakonstantinou et al., (2002, pp. 933) reported that ‘ the garage micro-environment [is an] important determinant to CO exposure’. Similarly an earlier study (Barker and Fox, 1976) noted that instantaneous concentrations of up to 210 ppm were experienced in the exit area of a multi- storey car park, where traffic flows were restricted. The elevated levels of CO in the car park could be attributed to malfunctioning or insufficient ventilation which leads to a build- up of contaminated air. Comparing these results to the underground car park in Auckland, it was found that mean exposures in the car park were slightly lower than those found on the car journey. One reason for this could be that the traffic volumes in Auckland were much higher than they were for Christchurch, so the car driver was exposed to higher concentration while traveling in the car. Another potential explanation could be that while the Christchurch car park was a commercial car park open the public, the Auckland car park was only open to business employees. This would have reduced vehicle movement quite substantially in the underground car park due to reduced traffic flow. The car park could also have been better ventilated which allowed adequate mixing of inlet air with the indoor air, thus obtaining a uniform fresh air distribution (Papakonstantinou et al., 2002).

While examining particulate pollution in the car parks, the results showed that the average levels of all three fractions of particulate monitored exceeded the mean exposures experienced while traveling in the car. The maximum value for PM10 at the car

park (100 µg3) exceeded the maximum values found on both trips (62.70 µg3 for J1; 94.80 µg3 for J2). Since the car park got relatively busy during peak hours, there would have been a build up of slow- moving traffic either entering or exiting the car park.

Furthermore, all cars had to stop before entering and leaving the park to pay at the parking kiosk, and although the windows were kept shut for the entirety of the journey, the driver had to open the window to collect the ticket at the beginning and pay before leaving. This would have allowed the emissions from surrounding vehicles to enter the car, and contaminate the in-vehicle air, thus increasing the PM exposure. In Auckland, the results for PM exposures were slightly different. While the PM10 reached the highest

mean exposure levels, the PM2.5 and PM1 levels were lower compared to the in-vehicle

journey exposures. This could be potentially explained by the fact that the PM10

particulates did not originate from traffic sources, but were other suspended particles such as dust from the floor. The mean PM2.5 and the PM1 particulate exposures were

higher for the car trips compared to the mean exposures at the underground car park. The journey exposures for all three grades of particulates reached maximum levels (shown as outliers in Figures 6.14, 6.15 and 6.16). The low levels in the car park could mean that the indoor air was not heavily contaminated by vehicle emissions. Adequate ventilation and low traffic movement could have both contributed to low vehicle emissions in the car park. Although the mean UFP count in the car park was lower in the Christchurch car park compared to the exposures in the car journeys, extremely high numbers were experienced in the micro-environment (Figure 5.20). This could have resulted from emissions from surrounding cars using the car park, especially when the windows were opened to receive and pay for the parking ticket. The slow moving and idling traffic could have also lead to the raised UFP levels in the sheltered car park.

As with other pollutants in other micro-environments, elevated levels were found in both the sheltered and underground car parks for all five pollutants monitored. This shows that while in some cases, the mean exposures may be lower in those micro-environments, pollutant levels can often reach very elevated levels.