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长三角是中国经济发展最活跃和城市化程度最高的地区之一,同时也是全国最早成立化工园区的地区之一[1]。随着长三角地区近年来城市经济的快速发展,城市工业化水平不断提高,而化工园区作为各项产业的集聚地,在工业生产过程中会产生大量的大气污染物,是城市空气污染的重要污染源[2]。颗粒物(particulate matter,PM)作为其排放的主要大气污染物导致雾霾事件在秋冬季节频繁发生[3]。PM具有粒径小、比表面积大、活性强、易富集有毒、有害物质等特点[4]。PM2.5和PM10(空气动力学当量直径分别≤2.5 μm和≤10 μm的PM[5])是当前长三角地区的首要污染物[6],并与近年来频发的雾霾天气有着密切的关系[4]。PM1.0被称为可入肺PM[7],容易渗透到呼吸道并沉积在肺部,对人体健康的影响极大[8]。研究表明,短期或长期暴露于雾霾天气中,会引发一系列健康危害,包括皮肤、心血管和呼吸道疾病等[9]。目前国内外对化工园区污染研究以VOCs(volatile organic compounds,VOCs)为主,如王红丽等[10]通过走航监测研究了化工园区VOCs的污染水平,发现园区周边的VOCs是城市环境大气浓度的3倍左右。Huang等[11]利用气相色谱-氢火焰/质谱对化工园区VOCs进行了监测分析并检测到了12种有害物质,主要以芳烃为主。Chen等[12]调查研究了大型化工园区中卤代烃的来源,发现工业溶剂使用、工业过程和车辆废气排放是环境空气中卤代烃的主要来源。垂直廓线代表了区域输送、垂直混合、与大气边界层的积累以及卷吸等多种因素的综合效应[13]。Liu等[14]利用无人机对中国澳门的细PM和黑炭进行了垂直分布分析,发现了平流和对流输送对PM污染物的垂直廓线有显著影响。Strbova等[15]研究了欧洲一个工业区内PM的垂直分布,发现垂直分布中PM浓度春季明显高于夏季,并在地面120—135 m观察到了逆温层的存在。我国化工园区对于PM垂直分布研究较少,对于大气PM的时空变化特征缺乏深度的研究分析,因此对于化工园区的PM垂直分布研究具有重要意义。
PM的垂直分布研究通常通过气象塔[16]、系留气球[17]、遥感[18]、多轴差分吸收光谱仪结合激光雷达[19]和载人飞行器[20]进行调查。气象塔是传统的监测方式,但其具有监测范围和高度有限等局限性。系留气球则是搭载不同仪器对垂直高空的污染物进行了监测,但其价格昂贵,并且只能用于垂直方向的观测。遥感虽然探测范围大、能在不同时空尺度上反映污染物的宏观分布情况,但是其监测高度位于300 m以上,监测的时间受卫星轨道限制,难以进行日常的实时监测。载人飞行器也可以进行大范围的监测,但其成本相对较高,一般不用于实验研究。无人飞机(unmanned aerial vehicle,UAV)是载人飞行器的良好替代品,针对PM污染物的垂直廓线测量,具有高效率[21]、灵活性和机动性[22]。
综上,化工园区是重要的大气污染源,而我国针对化工园区的PM垂直分布研究较少,对于化工园区大气PM的时空分布特征尚不清晰。本研究拟通过对长三角典型化工园区PM的时空分布特征进行调查分析,为我国化工园区的大气环境颗粒污染物监测及治理提供理论支持,有利于为相关部门制定相关大气污染治理的政策和标准提供科学依据[23]。
基于无人机研究长三角化工园区颗粒物垂直廓线
Vertical profiles of particulate matter in a chemical industrial park of Yangtze River Delta studied by a sensor on an unmanned aerial vehicle
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摘要: 化工园区的颗粒物污染非常严重,但目前对化工园区的颗粒物垂直廓线研究甚少,导致无法科学地评估化工园区的颗粒物排放对周边地区的影响。在2020年8月—2021年3月期间于杭州湾上虞经济技术开发区开展了23d,共计151次的颗粒物(PM1.0、PM2.5、PM10)垂直观测实验。利用无人机搭载微型检测仪研究化工园区0—500 m高度内颗粒物在不同季节及一天中的不同时间点(9、11、13、15、17时)的分布特征。结果表明,颗粒物平均浓度大小为冬季>秋季>春季>夏季,且秋冬季颗粒物浓度远大于春夏季,最高可达152.00 μg·m−3。由相关性分析可知,颗粒物分别与大气温度和相对湿度呈正相关,与风速呈负相关关系。颗粒物浓度总体随高度的升高而降低,由于粒径和质量影响,下降速率呈现为PM10>PM2.5>PM1.0。由粒径分析可知,在颗粒物浓度最高的当天,颗粒物数浓度主要由0.38—0.54 μm细粒子组成。由日变化可知,颗粒物浓度一般在9时达到最高,在13时达到最低。Abstract: The particle pollutions in chemical parks are quite serious, but there is little research on vertical profile of particulate matters (PM) in chemical parks recently, which makes it impossible to scientifically evaluate the impact of PM emissions from chemical parks on surrounding areas. From August 2020 to March 2021, a total of 151 vertical flights to observe of the vertical profiles of particulate matter (PM1.0, PM2.5, PM10) had been conducted in Shangyu Economic and Technological Development Zone of Hangzhou Bay during 23 d. The seasonal and diurnal variations of PM vertical profile in the range of 0—500 m height were studied by a micro-detector on an UAV. The seasonal concentration of PM is the highest in winter followed by autumn, spring, and summer, respectively. The PM concentrations in autumn and winter with peak value of 152.00 μg·m−3 were much higher than those in spring and summer. Correlation analysis shows that PM concentration is positively correlated with atmospheric temperature and relative humidity, and negatively correlated with wind speed. PM concentration generally was found to decrease with the increase of height in this study with their rates highest in PM10 followed by PM2.5, PM1.0 in order is due to particulate size and mass. Particle size analysis showed that the PM with their diameters in the range of 0.38—0.54 μm are the dominant on the day with the highest PM concentration. In the diurnal variation, the PM concentration generally reached its peaks at 9 o 'clock and the lowest at 13 o 'clock.
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Key words:
- vertical observation /
- particulate matter /
- chemical industrial park /
- seasonal variation
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表 1 实验期间气象参数记录情况
Table 1. Meteorological parameter record table during the experiment
日期
Date最低—最高温度/℃
Minimum - maximum temperatureRH/% 风速风向 2020.08.19 27—36 55 东南风2级 2020.08.20 27—37 57 东南风2级 2020.08.21 27—35 60 东南风2级 2020.10.20 15—22 83 东北风2级 2020.10.21 16—19 86 西北风2级 2020.10.24 12—19 69 东北风2级 2020.10.25 10-—18 80 东南风1级 2021.01.25 8—15 90 西北风1级 2021.01.26 9—10 91 西北风2级 2021.01.27 8—9 90 东北风2级 2021.01.28 7—12 70 西北风3级 2021.01.29 5—10 62 东北风2级 2021.01.30 5—15 64 东南风1级 2021.03.23 12—29 53 东南风2级 2021.03.24 13—29 67 东南风2级 2021.03.25 12—29 75 东北风1级 注:风速0.3—1.5 m·s−1为1级风,1.6—3.3m/s为2级风,3.4—5.4m/s为3级风
Note: Wind speeds of 0.3—1.5 m·s−1 are force 1, 1.6—3.3 m·s−1 are Force 2, and 3.4—5.4 m·s−1 are force表 2 PM浓度在不同季节每上升百米的变化情况
Table 2. Variation of particulate matters concentration in different seasons for each rising by 100m
PM1.0/(μg·m−3) PM2.5/(μg·m−3) PM10/(μg·m−3) 夏(2020年8月)
Summer−0.37 −1.04 −11.70 秋(2020年10月)
Autumn0.98 0.86 0.60 冬(2021年1月)
Winter−4.85 2.67 40.08 春(2021年3月)
Spring−0.74 −1.02 −1.96 注:负值代表PM浓度随着高度升高而减小.
Note: Negative values indicate that the concentration of particles decreases with the increase of height.表 3 不同粒径PM相关性分析
Table 3. Correlation analysis of particles of different sizes
平均值
Average value标准差
Standard deviationPM1.0 PM2.5 PM10 PM1.0 55.09 33.62 1.00 PM2.5 72.74 44.48 0.99* 1.00 PM10 87.71 53.16 0.96* 0.99* 1.00 * P<0.05. -
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