长春市城区近地表灰尘粒度特征及其环境意义

摘要

为剖析长春市城区近地表灰尘粒度特征，分别沿南北和东西轴线采集了34件城市近地表灰尘样品，采用激光粒度仪对样品进行了粒度测试分析。结果表明：长春市近地表灰尘颗粒物平均中值粒径和算术平均粒径分别为21．58μm和24．24μm ，分选极差；以粗粉粒（10．00～80．00μm ）为主，平均约占71．28％，黏粒组（＜5．00μm ）和细粉粒组（5．00～10．00μm ）分别约占14．75％和13．05％。频率曲线呈正偏双峰型分布，峰态中等偏窄，与现代尘暴和城市街道灰尘分布特征相一致，反映出其起源的多元性和相对稳定性，表明近地表灰尘沉积仍是风积作用的继续。近地表灰尘颗粒物粒径均小于100．00μm ，极易在外动力条件下再次扬起并悬浮搬运，PM 10和PM 2．5所占比例分别为27．76％和7．32％，其生态环境效应不应被忽视。粒径分布无显著空间变化，但城市中心区域粒径变化范围小，这可能说明城市边缘区域较中心区域近地表灰尘的起源更具多源性和复杂性。%A series of investigations were performed to provide particle size signatures of urban dust near the ground in Changchun ,China .A total of 34 samples of dust were collected along the north-south and the east-west axis using a systematic sampling strategy (about 1 .5 m above the ground surface) .The laser particle size instrument was employed to analyze the particle size .According to the analytical results ,the mean median grain size and the arithmetic mean diameter of the near-surface urban dusts in Changchun was 21 .58 μm and 24 .24 μm ,respectively .The coarse silt (10 .00 80 .00 μm) content in the urban dusts was higher relatively ,which was 71 .28% on average ,while the clay particle (<5 .00 μm) and fine silt (5 .00 10 .00 μm) was 14 .75% and 13 .05% ,respectively .The distribution of grain size was characterized by skewed positively ,bimodal and middling to narrow kurtosis ,which was similar to the gain size distribution of modern dust storms and street dust and indicated that urban dust near the ground is a mixture of coarse grains derived from local area and fine grains transported over long distances ,and was derived from aeolian processes .The gain size in urban dust near the ground was almost completely below 100 .00 μm ,which indicated that these particles were pick up and transported by suspension under proper aerodynamic conditions .Meanwhile ,the average content of PM10 and PM2 .5 in urban dust near the ground was 27 .76% and 7 .32% ,respectively ,which were much higher ,showing the high potential hazards . There were no significant spatial variations of gain size distribution , however ,the variation range of grain size in central urban area was small relatively ,which indicated that the origination of urban dust near the ground was multiple and complicated in suburban compared with that of the central urban area .