Characteristics of airborne particles retained on conifer needles across China in winter and preliminary evaluation of the capacity of trees in haze mitigation.
Characteristics of airborne particles retained on conifer needles across China in winter and preliminary evaluation of the capacity of trees in haze mitigation.
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DOI：
10.1016/j.scitotenv.2021.150704
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
Zhiguo Cao;X. Wu;Tianyi Wang;Yahui Zhao;Youhua Zhao;Danyang Wang;Yu Chang;Ya Wei;G. Yan-G.
中科院分区：
文献类型：
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作者：
Zhiguo Cao;X. Wu;Tianyi Wang;Yahui Zhao;Youhua Zhao;Danyang Wang;Yu Chang;Ya Wei;G. Yan-G.
为全面了解大空间尺度上植物叶片颗粒物（PM）的分布特征以及植被对灰霾的影响，对中国31个城市（30个省会城市）78个公园和校园的针叶样品进行了调查，并建立了一种综合的植物叶片颗粒物（PM）分布特征分析方法。PMR负荷（包括水不溶性颗粒物（WIPM），水溶性无机离子（WSIS）和水溶性有机物（WSOM）），平均值为554 ± 345 mg m − 2叶面积，PMR的组分分布在城市之间表现出明显的空间差异。虽然灰霾污染水平在31个城市之间差异很大，但针叶的PM滞留能力并不取决于灰霾水平，因为PMR通常在冬季降水前达到饱和。水溶性成分（WSC）平均占PMR的52.3%，其中WSIS和WSOM分别占PMR的21.4%和30.9%。城市PMR中WSIS的主要离子为Ca2+、K+和NO3 −，表明扬尘、生物质燃烧和交通尾气是中国PM的重要来源。与以往的研究结果相比，我国PMR和PM的粒径分布基本一致，细颗粒物（PM2.5）在PMR中所占比例较大（43.8 ± 17.0%）。这些结果证明树木可以有效地去除空气中的细颗粒物，从而减少人类接触可吸入颗粒物。提出了一种估算雪松PMR年总量的方法，中国雪松PMR年平均值为11.9 ± 9.6 t km-2/a。通过与降尘负荷（大气颗粒物自然落在地面，全国平均138 ± 164 t km-2土地面积yr-1）的比较，可以看出树木在缓解雾霾污染中发挥了重要作用。
To fully understand the characteristics of particulate matter (PM) retained on plant leaves (PMR) and the effect of vegetation on haze on a large spatial scale, we investigated needle samples collected from 78 parks and campuses in 31 cities (30 provincial cities) of China and developed a comprehensive method to characterise PMR. Both the PMR load (including water-insoluble particulate matter (WIPM), water-soluble inorganic ions (WSIS) and water-soluble organic matter (WSOM)), with a mean value of 554 ± 345 mg m−2leaf area, and component profiles of PMR showed obvious spatial variation across the cities. Though haze pollution levels vary greatly among the 31 cities, the PM retention capacity of needles does not depend on haze level because PMR generally reaches saturation before precipitation in winter. The water-soluble component (WSC, the sum of WSIS and WSOM) accounted for 52.3% of PMR on average, among which WSIS and WSOM contributed 21.4% and 30.9% to PMR, respectively. The dominant ions of WSIS in PMR in the cities were Ca2+, K+and NO3−, indicating that raised dust, biomass combustion and traffic exhaust are significant sources of PM in China. Compared with previous reports, the particle size distributions of PMR and PM across China were consistent, with fine PM (PM2.5) constituting a substantial proportion (43.8 ± 17.0%) of PMR. These results prove that trees can effectively remove fine particles from the air, thereby reducing human exposure to inhalable PM. We proposed a method to estimate the annual amount of PMR onCedrus deodara, with an average value of 11.9 ± 9.6 t km−2canopy yr−1in China. Compared with the load of dust fall (atmospheric particles naturally falling on the ground, average of 138 ± 164 t km−2land area yr−1in China), we conclude that trees play a significant role in mitigating haze pollution.