The Robert H. Smith Faculty of Agriculture, Food and Environment, Department of Soil and Water Sciences, The Hebrew University of Jerusalem, Rehovot, Israel.
Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel.
Sci Total Environ. 2019 Mar 25;658:1316-1333. doi: 10.1016/j.scitotenv.2018.12.272. Epub 2018 Dec 19.
Dry deposition of ozone (O) to vegetation is an important removal pathway for tropospheric O, while O uptake through plant stomata negatively affects vegetation and leads to climate change. Both processes are controlled by vegetation characteristics and ambient conditions via complex mechanisms. Recent studies have revealed that these processes can be fundamentally impacted by coastal effects, and by dry and warm conditions in ways that have not been fully characterized, largely due to lack of measurements under such conditions. Hence, we hypothesized that measuring dry deposition of O to vegetation along a sharp spatial climate gradient, and at different distances from the coast, can offer new insights into the characterization of these effects on O deposition to vegetation and stomatal uptake, providing important information for afforestation management and for climate and air-quality model improvement. To address these hypotheses, several measurement campaigns were performed at different sites, including pine, oak, and mixed Mediterranean forests, at distances of 20-59 km from the Eastern Mediterranean coast, under semiarid, Mediterranean and humid Mediterranean climate conditions. The eddy covariance technique was used to quantify vertical O flux (F) and its partitioning to stomatal flux (F) and non-stomatal flux (F). Whereas F tended to peak around noon under humid Mediterranean and Mediterranean conditions in summer, it was strongly limited by drought under semiarid conditions from spring to early winter, with minimum average F/F of 8-11% during the summer. F in the area was predominantly controlled by relative humidity (RH), whereas increasing F with RH for RH < 70% indicated enhancement of F by aerosols, via surface wetness stimulation. At night, efficient turbulence due to sea and land breezes, together with increased RH, resulted in strong enhancement of F. Extreme dry surface events, some induced by dry intrusion from the upper troposphere, resulted in positive F events.
臭氧（O）向植被的干沉降是对流层 O 的重要去除途径，而通过植物气孔吸收 O 会对植被产生负面影响，并导致气候变化。这两个过程都通过复杂的机制受到植被特征和环境条件的控制。最近的研究表明，这些过程可能会受到沿海效应以及干燥和温暖条件的根本影响，但这些影响的特征尚未得到充分描述，这主要是由于缺乏此类条件下的测量结果。因此，我们假设沿着急剧的空间气候梯度，并在距海岸不同的距离测量 O 向植被的干沉降，可以为 O 沉降到植被和气孔吸收的这些效应的特征提供新的见解，为造林管理和气候与空气质量模型改进提供重要信息。为了解决这些假设，在不同地点进行了几次测量活动，包括距东地中海海岸 20-59km 处的松树、橡树和混合地中海森林，这些地点处于半干旱、地中海和湿润地中海气候条件下。采用涡度相关技术来量化垂直 O 通量（F）及其向气孔通量（F）和非气孔通量（F）的分配。在夏季，湿润地中海和地中海气候条件下，F 倾向于中午左右达到峰值，而在半干旱条件下，F 受到干旱的强烈限制，从春季到初冬，平均 F/F 最小为 8-11%。该地区的 F 主要受相对湿度（RH）控制，而 RH<70%时，F 随 RH 的增加表明通过表面湿润度刺激增强了 F 由气溶胶引起的。夜间，由于海陆风引起的高效湍流以及 RH 的增加，导致 F 得到了强烈增强。一些由对流层上部干入侵引起的极端干燥表面事件导致了正的 F 事件。
