A Survey On Air Quality And Impact Factors Related In Shanghai Rail Transit System

Rail transit system (RTS), as a rapid safe transportation, is increasingly accepted by urban residents. It was reported that the rail transit network has accounted for 35% of the public traffic volume in Shanghai by 2010. With the RTS becomes the main kind of public traffic, people spend more and more time in rail transit stations. Air quality in rail transit station may affect health of passengers and workers in stations.In order to clarify status of air quality and main pollutants in RST and provide the scientific basis for setting relevant standards for health, we conducted a comprehensive survey in Shanghai rail transit system in four seasons.Six representative stations (including four underground stations and two stations above the ground) and three representative lines of carriages in Shanghai RST were selected for survey. Environmental monitoring was carried on respectively in May, July, September of 2009 and January of 2010. We selected 14 health indicators for monitoring.-The monitoring index include 1 micro climate (temperature, relative humidity, average wind speed); 2 chemical pollutants such as carbon monoxide (CO), carbon dioxide (CO2), PM10, formaldehyde and volatile organic compounds (VOCs, benzene, toluene, ethylbenzene and xylene); 3 microbial index (bacteria, fungi, total hemolytic streptococcus, corps bacteria); 4 noise and fresh air volume. The volume of passenger in the monitoring time was investigated.The results showed that annual average temperature in underground station were fluctuated between 17.1℃and 28.7℃and the rates of exceeding reference standard were 90.6% and 76.2% respectively in winter and summer. In winter it manifested above the standard value and in summer it manifested below standard value. The rate of exceeding reference standard for relative humidity in winter was 90.8%, which manifested above the standard value. There were no significantly differences for micro climate indexes between platform and hall of subway station among four seasons. The monitoring results for air pollutants in stations shows that the average total count of bacterial was fluctuated 22.9-38.0 colony per plate with 0.59%annual rate of exceeding reference standard in underground stations and 22.1±4.1-22.1±4.1 colony per plate in ground stations. The average total count of fungi was fluctuated from 17.9 to 30.6 colony per plate in underground stations and 18.2-18.5 colony per plate for ground stations. The average concentration of PM10 was 0.124mg/m3～0.169 mg/m3 in underground stations and 0.111 mg/m3-0.117 mg/m3 in ground stations. The concentration of PM10in underground stations except one was higher than that of outside and the annual rate of exceeding reference standard was 1.81% in underground station. The annual average concentration of CO2 were 0.056±0.01%～0.071±0.01% in underground stations and 0.055±0.01%～0.059±0.01% in ground stations. The annual rates of exceeding standard for CO2 were 0.6% in underground station. The average concentration of VOC were.0.095±0.001 mg/m3～0.197±0.001 mg/m3 in underground stations and 0.069±0.002mg/m3～0.089±0.001 mg/m3 in ground stations. The annual rate of exceeding standard was 7.62% in underground station. The average concentration of formaldehyde were 0.012mg/m3～0.037 mg/m3 in underground stations and 0.007 mg/3～0.008 mg/m3 in ground stations. The annual rate of exceeding reference standard were 0.33% and 0.15% respectively. The average concentration of noise were 54.5±5.3dB(A)～60.8±2.5 dB(A) in underground stations and 56.4±8.7 dB(A)～59.4±5.1 dB(A) in ground stations. The annual rates of exceeding standard were 1.96% and 2.20% respectively. The concentration of CO both in underground stations and ground stations were not exceeded the reference standard The average level of total count of bacterial, total count of fungi, CO2, PM10 and noise in platform areas in underground stations were 38.5±2.7 colony per plate,33.1±6.6 colony per plate,0.075±0.003%,0.192±0.004 mg/m3 and 62.3±3.5 dB(A) respectively, and were higher than those in the hall areas respectively(23.5±2.8colony per plate,20.1±4.5colony per plate,0.046±0.009%,0.119±0.02 mg/m3,47.4±2.9 dB(A). The average level of total count of bacterial, total count of fungi, CO2, VOC, PM10 and noise in platform areas in ground stations were 26.5±3.6 colony per plate,30.8±0.9 colony per plate,0.065±0.007%,0.048±0.002 mg/m3,0.202±0.021 mg/m3 and 65.3±2.2 dB(A) respectively and higher than those in the hall areas respectively (14.0±1.8colony per plate,19.7±3.7colony per plate,0.042±0.007%,0.018±0.005 mg/m3,0.122±0.019 mg/m3,47.3±2.3 dB(A))). For CO and formaldehyde there was no significant difference between the platform and hall areas. The average levels of total count of bacterial and total count of fungi, CO2 and PM10 in rail transit stations in normal hours were significantly lower than those in the rushing hours. The concentration of formaldehyde in rush hours was significantly lower than that in the morning. The average total count of bacterial in the underground stations was 30.1±7.7 colony per plate in July which was significantly higher than that in other months. The average total count of fungi in the underground stations was 9.4±1.2 colony per plate in January, which was significantly lower than that in other months. The average concentration of formaldehyde and VOC were 0.230±0.042 mg/m3 and 0.050±0.005 mg/m3 respectively in July and significantly higher than those in January and May. There were no seasonal differences for CO and CO2. The average total count of bacterial in the ground stations was 21.5±4.1 colony per plate in May which was significantly lower than that in other months. The average total count of fungi in the ground stations was 37.1±8.6 colony per plate in July which was significantly higher than that in other months. The average concentration of formaldehyde and VOC were 0.043±0.004 mg/m3 and 0.472±0.019 mg/m3 respectively in July and significantly higher than those in other months. There were no seasonal differences in CO and CO2. According to multiple regression analysis results the total count of bacteria was negatively correlated with fresh air volume and positively correlated with temperature and concentration of PM10.The total count of fungi was negatively correlated with fresh air volume and positively correlated with relative humidity and concentration of PM10. The concentration of CO2 was negatively correlated with fresh air volume and positively correlated with passenger flow and concentration of PM10. The concentration of PM10 was negatively correlated with fresh air volume and positively correlated with passenger flow and temperature. The concentration of VOC was negatively correlated with fresh air volume. There was no significant relationship between the concentration of formaldehyde and CO and each impact factor. Hemolytic streptococcus was detected in November and no Legionella was found in monitoring samples.The results for monitoring carriages showed that there were no significant differences among the three selected rail transit lines in micro climate indices. The average levels of relative humidity, temperature and wind speed were 56.3±3.7%, 23.3±2.3℃,0.55±0.04m/s respectively. The relative humidity in January and May was below reference standard obviously. The average temperature in carriages was significantly lower in January and higher in November compared with reference standard. Wind speed in July, November and January were significantly higher than reference standard. Relative humidity in January was 34.4±3.7% and significantly lower than that in other monitoring months. The concentration of CO in carriage of line 3 was 0.46±0.03mg/m3 which was significantly lower than those in linel and line8(0.63±0.01 mg/m3 and 0.72±0.03 mg/m3 respectively). The concentration of CO2 in the carriage of line8 was 0.135±0.034% which was significantly lower than those in linel and line3(0.158±0.010% and 0.200±0.042% respectively). The concentration of VOC in the carriage of linel was 0.202±0.067 mg/m3 and significantly higher than those in line3 and line8(0.100±0.009 mg/m3 and 0.091±0.018 mg/m3 respectively). The concentration of PM10 in carriage of line1 was 0.112±0.007 mg/m3 and significantly higher than those in line3 and line8 (0.068±0.002 mg/m3 and 0.078±0.012 mg/m3 respectively). There were no significantly differences in total count of bacteria and fungi and noise among the three lines. The annual rate of exceeding reference standard for the total count of bacteria, CO2 and noise were 0.9%,42.5%,42.8% respectively. The concentration of CO2 and noise were obviously high in each monitoring month and total count of bacteria was significantly high in May and July. Total count of bacteria and total count of fungi, CO2 and PM10 at normal hours were significantly lower than those in rushing hours, while the concentrations of formaldehyde and VOC in the morning were significantly higher than those in noon and afternoon. The average level of total count of fungi in July in the three lines was 34.9±4.2 colony per plate and significantly higher than those in other months. The concentration of formaldehyde and VOC in July were 0.376±0.014 mg/m3 and 0.133±0.003 mg/m3 respectively and significantly higher than those in other months. The concentration of PM10 in January was 0.108±0.049 mg/m3,and significantly higher than that in other months. There was no seasonal difference for other indexes.The second part of the thesis was about health impact of air pollution in rail transit system by questionnaires to rail transit workers and passengers. The rail transit workers were selected by stratified random sampling and passengers were randomly sampled.281 qualified questionnaires were received. The results show that most respondents believed that the air quality in rail transit system was comparatively satisfactory. The results showed that there was no significant gender difference in perception to air quality in rail transit system. There was age difference existed in answering question. Old people have a higher requirement for air quality. The passengers flow and shortage of ventilation was two most important influencing factors for rail traffic environment. The proportion of occasionally or frequently discomfort in staff group was significantly higher than that in passengers group.