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伴随经济的快速发展,环境问题日益突出,大气污染尤为严重 [1]. 大气污染受人类活动影响较大,当大气污染物浓度升高到一定程度,就会破坏生态系统和人类正常生存条件. 近年来,中国许多城市都受到大气污染的困扰,特别是在京津冀地区、长三角地区等经济发达地区[2]. 另外,当空气中大气污染物浓度较高时,人体可能出现呼吸系统疾病,心脑血管疾病、肺癌等[3].
新型冠状病毒肺炎(COVID-19)疫情于2020年春节前夕爆发,并快速在全国范围内传播. 2020年1月23日到1月29日,各省陆续启动公共卫生一级响应,实行全面居家隔离政策有效降低了病毒的传播几率[4]. 虽然疫情防控使经济发展受到一定影响,但大气质量得到改善[5]. 自疫情爆发以来,许多学者对居家隔离政策下的大气状况和空气质量进行了一系列研究,艾文育等[6]发现济南市NO2浓度下降幅度最大,社会活跃指数呈阶梯状下降;余锋等[7]发现关中盆地空气质量整体得到改善,除O3以外的污染物浓度均出现不同程度的下降;潘勇军等[8]发现广州市大气污染物浓度除O3外大幅度下降,O3成首要污染物.
兰州市作为中国西北地区重要的工业重镇和交通枢纽,大气污染源分布较多;再加上地形封闭,大气扩散条件较差,空气质量下降的风险较大[9]. 疫情防控为比较全面地分析研究兰州市大气污染的时空变化规律和成因创造了良好的机会,本文利用2020年、2021年监测站点数据以及卫星数据,从时间上和空间上对兰州市疫情期间大气污染物变化进行分析,并利用Pearson相关系数法分析6种大气污染物之间以及气象因素之间的关系,为今后兰州市大气污染防控工作开展提供科学依据.
COVID-19疫情期间兰州市大气污染时空变化分析
Spatial-temporal changes of air pollution in Lanzhou during the outbreak of COVID-19
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摘要: 2020年新冠病毒席卷全球,我国政府采取一系列政策和措施进行防控,减少了污染排放,这个特殊时期为研究人类活动对大气污染的影响提供了良好机会. 本文结合了监测站点数据、卫星遥感数据以及气象资料等,从时间和空间上对兰州市疫情期间大气污染物浓度变化进行分析,并利用Pearson相关系数法分析了6种大气污染物(PM2.5、PM10、SO2、NO2、CO、O3)之间以及与气象因素(温度、湿度、风速、气压)之间的相关性,同时分析了2021年10月兰州突发疫情下,大气污染物浓度变化,并与2020年作对比. 结果表明:(1)2020年疫情防控期间NO2、CO、PM2.5、SO2等的浓度下降明显,其中PM2.5在进入全面抗疫阶段后,下降幅度最大,达到20.5%,NO2、CO次之,大多是在主城区人口密集地区;(2)SO2浓度与历年同期相比,下降幅度最大,达到26.8%,受工业影响较大;(3)CO、NO2、SO2三者具有强相关性,变化趋势保持一致;NO2、SO2浓度变化影响着PM2.5浓度;O3与5种大气污染物均呈负相关,其他5种大气污染物浓度升高时,太阳辐射减少,抑制O3的生成,O3浓度随之下降;(4)气象因素也影响着大气污染物浓度;温度与PM2.5、PM10、SO2、NO2、CO均呈负相关,与O3呈强正相关;湿度与6种大气污染物均呈负相关;风速与PM2.5、PM10、SO2、NO2、CO均呈负相关,与O3呈正相关,但是当风速过高时,也会使O3浓度下降. (5)2021年10月突发疫情防控期间,NO2、CO大幅度下降,PM2.5也受影响,PM10与O3并未有太大变化,而由于工厂并未停工,SO2浓度并未受太大影响.
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关键词:
- 兰州市 /
- 大气污染物 /
- 时空变化 /
- COVID-19 /
- Pearson相关系数
Abstract: In 2020, the Corona Virus Disease 2019(COVID-19) swept the world. The Chinese government has adopted a series of policies and measures for pandemic prevention and control, which further reduced the discharge of air pollutants. This special period provides a good opportunity for studying the impact of human activities on air pollution. Based on the in situ Data, satellite remote sensing data and meteorological data, this paper analyzed the change of air pollutant concentration in Lanzhou during this period from the perspective of time and space. The Pearson correlation coefficient method was used to analyze the correlations among 6 kinds of air pollutants and the correlation between these pollutants and the meteorological factors. In addition, the variation of air pollutant concentration during the outbreak of COVID-19 in Lanzhou in October 2021 was analyzed and compared with the situation in 2020. The results show that :(1) in 2020, the concentration of NO2, CO, PM2.5 and SO2 decreased significantly. Especially for the concentration of PM2.5, it dropped by 20.5%, which was followed by the decrease of NO2 and CO concentration that mostly distributed in urban areas with dense population. (2) Compared with the situation of the same period in previous years, the concentration of SO2 decreased by 26.8%, which was greatly affected by industry. (3) CO, NO2 and SO2 presents strongly correlation with each other, and their variation trends are consistent. The change of NO2 and SO2 concentration affects the concentration of PM2.5. In addition, O3 is negatively correlated with the other 5 kinds of air pollutants. When the concentration of the other 5 pollutants increases, the solar radiation decreases, which restrains the concentration of O3. (4) The meteorological factors also affect the concentration of these air pollutants. Temperature is negatively correlated with the concentration of PM2.5, PM10, SO2, NO2 and CO, and presents strongly positively correlation with the concentration of O3. Humidity is negatively correlated with all these air pollutants. Wind speed is negatively correlated with the concentration of PM2.5, PM10, SO2, NO2 and CO, and positively correlated with O3 concentration. However, when wind speed is too high, the concentration of O3 also decreases. (5) During the outbreak of COVID-19 in October 2021, the concentration of NO2 and CO decreased significantly, and the PM2.5 concentration was also affected. However, the concentration of PM10 and O3 presented little change. SO2 concentration was not affected significantly, since factories were still working. -
表 1 2020年疫情防控时期污染物浓度变化情况
Table 1. Change of pollutant concentration in four stages in 2020
污染物
Pollutants第一至第二阶段
Phase one to phase two第二至第三阶段
Phase two to phase three第三至第四阶段
Phase three to phase fourPM2.5 −20.49% −22.14% +1.15% PM10 −7.98% +12.68 +13.04 NO2 −27.38% −2.81% −8.33% SO2 −3.95% −26.85% −23.15% CO −16.86% −28.98% −17.34% O3 +76.21% +11.61% +5.47% 注:计算公式为(后阶段-前阶段)/ 前阶段,即变化率. (阶段划分依据见研究方法).
Note: The calculation formula is (latter stage - former stage)/former stage, that is, the rate of change.表 2 2020年第二阶段(全面抗疫阶段)与2018、2019年同期污染物平均浓度比较
Table 2. Comparison of the average pollutant concentration in the second phase (comprehensive containment phase) of 2020 with the same period in 2018 and 2019
污染物
Pollutants第二阶段
The second stage2018、2019年同期
The same period in 2018 and 2019与2018、2019年同期比较
Comparison with the same period in 2018 and 2019PM2.5/(μg·m−3) 49 48.71 0.595% PM10/(μg·m−3) 88.1 103.75 −15.08% NO2/(μg·m−3) 49.03 52.13 −5.95% SO2/(μg·m−3) 22.34 30.52 −26.8% CO/(mg·m−3) 1.38 1.68 −17.8% O3/(μg·m−3) 92 68.55 34.2% 表 3 2021年应急防控期与2020年同期污染物平均浓度比较
Table 3. Comparison of the average pollutant concentration between the emergency prevention and control period in 2021 and the same period in 2020
污染物
Pollutants2021年应急防控期
2021 epidemic control phase2020年同期
The same period in 2020与2020年同期比较
Comparison with the same period in 2020PM2.5/(μg·m−3) 36 43.3 −16.86% PM10/(μg·m−3) 71.38 106.25 −32.82% NO2/(μg·m−3) 44.04 61.92 −28.88% SO2/(μg·m−3) 12.29 18 −31.72% CO/(mg·m−3) 0.76 1.14 −33.33% O3/(μg·m−3) 75.5 68 11.02% 表 4 6种大气污染物相关性分析
Table 4. Correlation analysis of 6 kinds of air pollutants
污染物
PollutantsPM2.5 PM10 CO NO2 SO2 O3 PM2.5 1 0.402** 0.781** 0.672** 0.639** −0.512** PM10 1 −0.04 0.085 0.01 0.047 CO 1 0.864** 0.829** −0.481** NO2 1 0.757** −0.307** SO2 1 −0.265** O3 1 **在 0.01 级别(双尾),相关性显著;n=109. ** At level 0.01(double tail), the correlation was significant. n=109 表 5 6种大气污染物与气象因素之间相关性分析
Table 5. Correlation analysis between 6 kinds of air pollutants and meteorological factors
气象因素
Meteorological factorsPM2.5 PM10 NO2 SO2 CO O3 平均温度 −0.368** −0.275** −0.398** −0.314** −0.412** 0.703** 湿度 −0.384** −0.228* −0.133** −0.231** −0.264** −0.671** 风速 −0.176** −0.245* −0.298** −0.310** −0.326** 0.317** 气压 −0.089 −0.102 −0.212* −0.149 −0.094 −0.132 *在 0.05 级别(双尾),相关性显著;**在 0.01 级别(双尾),相关性显著;n=109.
*At level 0.05(double tail), the correlation was significant. ** At level 0.01(double tail), the correlation was significant. n=109. -
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