广州市中心城区公交车站颗粒物污染暴露特征及影响因素分析

Exposure Characteristics and Determinants of Particulate Matter at Bus Stops in Central District of Guangzhou

为探究超大城市居民在中心城区公交车站候车的颗粒物暴露情况,使用Grimm Aerosol 11-A型便携式气溶胶光学粒径谱仪对广州市越秀区和天河区共7个典型公交车站的颗粒物污染暴露进行平行监测.结果表明:①各公交车站的平均PM 1、PM_(2.5)和PM 10暴露浓度分别为(33.35±15.96)(46.97±22.94)和(89.70±67.07)μg m^(3),休息日公交车站的暴露浓度约为工作日的2倍,高峰期颗粒物暴露浓度略高于平峰期.②候车乘客数、道路车流量和相对湿度是影响PM_(1)、PM_(2.5)暴露浓度的主要因素,纯电动公交车停靠次数虽对细颗粒物暴露浓度无明显贡献,但其制动、轮胎与路面摩擦以及扬尘产生的粗粒径排放成为PM 10污染的主要因素之一.③粗粒径模态(1~10μm)颗粒物是颗粒物浓度的主要贡献源,其浓度占比高达63%,但数浓度占比不足1%;而积聚模态(0.25~1μm)颗粒物数浓度占比在99%以上,部分车站积聚模态颗粒物质量浓度占比超过40%,说明细颗粒污染严重.④单位时间内公交车站候车乘客PM_(1)、PM_(2.5)和PM 10总暴露剂量分别为(241.80±82.85)(342.59±112.11)和(681.17±226.89)μg h,表现出工作日高于休息日、工作日高峰期高于平峰期、休息日高峰期低于平峰期的特征,部分车站(如DF和LS站)老人总暴露剂量占比超过40%,成为公交车站主要暴露对象之一.研究显示,广州市中心城区公交车站颗粒物暴露特征时空差异明显,道路车流量、相对湿度、候车乘客数和公交车停靠次数是影响颗粒物暴露浓度的主要因素.

In order to evaluate the exposure of passengers to particulate matter(PM)while waiting at bus stops in the central district of a typical megacity,an experimental study was carried out using the portable aerosol optical spectrometer Grimm Aerosol 11-A at 7 typical bus stops in Yuexiu District and Tianhe District of Guangzhou.The key findings were as follows:(1)The mean exposure concentration of PM_(1),PM_(2.5) and PM 10 was(33.35±15.96)(46.97±22.94)and(89.70±67.07)μg m^(3),respectively.The PM exposure concentration on weekends was twice as much as that on weekdays with slightly higher concentration during peak period than that during off-peak period.(2)The number of waiting passengers,road traffic flow and relative humidity were three determinants that have a statistically significant impact on personal exposure to PM 1 and PM_(2.5).The contribution of electric buses to fine particles when entering and leaving the bus stops was not obvious,but due to brakes,tire friction and road dust,a large amount of coarse particles were generated,which account for the causes of PM_(10) pollution.(3)Coarse particle mode(1-10μm)was the main contributor to PM mass concentration,accounting for 63%,although it only accounted for less than 1%of the particulate number concentration.Accumulated particulate matter(0.25-1μm)accounted for more than 99%of the number concentration,and its contribution to mass concentration at some bus stops exceeded 40%,indicating that the pollution of fine particulate matter at bus stops was serious.(4)The total hourly pollution exposure of PM 1,PM_(2.5) and PM_(10) was(241.80±82.85)(342.59±112.11)and(681.17±226.89)μg h,respectively.It revealed the pattern that the exposure dose on weekdays was higher than that on weekends,with higher during peak hours than off-peak hours on weekdays,and lower during peak hours than off-peak hours on weekends.In addition,at the DF and LS stops,the total pollution exposure dose ratio of the elderly exceeded 40%,indicating that the elderly was one of the riskiest groups.The studies have shown that there are obvious temporal and spatial differences in the exposure characteristics of particulate matter at bus stops in central district of Guangzhou.Road traffic,relative humidity,number of passengers waiting for the bus,and frequency of bus entering and leaving bus stations are the main factors that significantly affect the concentration of particulate matter exposure.