Institute for Advanced Sustainability Studies , Berliner Strasse 130, 14467 Potsdam, Germany.
Geography Department, Humboldt-Universität zu Berlin , Unter den Linden, 10099 Berlin, Germany.
Environ Sci Technol. 2017 Jun 6;51(11):6120-6130. doi: 10.1021/acs.est.6b06514. Epub 2017 May 17.
The potential of emissions from urban vegetation combined with anthropogenic emissions to produce ozone and particulate matter has long been recognized. This potential increases with rising temperatures and may lead to severe problems with air quality in densely populated areas during heat waves. Here, we investigate how heat waves affect emissions of volatile organic compounds from urban/suburban vegetation and corresponding ground-level ozone and particulate matter. We use the Weather Research and Forecasting Model with atmospheric chemistry (WRF-Chem) with emissions of volatile organic compounds (VOCs) from vegetation simulated with MEGAN to quantify some of these feedbacks in Berlin, Germany, during the heat wave in 2006. The highest ozone concentration observed during that period was ∼200 μg/m (∼101 ppb). The model simulations indicate that the contribution of biogenic VOC emissions to ozone formation is lower in June (9-11%) and August (6-9%) than in July (17-20%). On particular days within the analyzed heat wave period, this contribution increases up to 60%. The actual contribution is expected to be even higher as the model underestimates isoprene concentrations over urban forests and parks by 0.6-1.4 ppb. Our study demonstrates that biogenic VOCs can considerably enhance air pollution during heat waves. We emphasize the dual role of vegetation for air quality and human health in cities during warm seasons, which is removal and lessening versus enhancement of air pollution. The results of our study suggest that reduction of anthropogenic sources of NOx, VOCs, and PM, for example, reduction of the motorized vehicle fleet, would have to accompany urban tree planting campaigns to make them really beneficial for urban dwellers.
城市植被排放与人为排放相结合产生臭氧和颗粒物的潜力早已被认识到。随着温度的升高，这种潜力会增加，并且在热浪期间可能会导致人口稠密地区的空气质量严重恶化。在这里，我们研究了热浪如何影响城市/郊区植被挥发性有机化合物的排放以及相应的地面臭氧和颗粒物。我们使用天气研究与预报模型与大气化学（WRF-Chem），并用植被的MEGAN 模拟挥发性有机化合物（VOCs）的排放，以量化德国柏林在 2006 年热浪期间的一些这种反馈。在此期间观察到的最高臭氧浓度约为 200 μg/m（约 101 ppb）。模型模拟表明，生物源 VOC 排放对臭氧形成的贡献在 6 月（9-11%）和 8 月（6-9%）低于 7 月（17-20%）。在分析的热浪期间的特定日子里，这种贡献增加到 60%。实际贡献预计会更高，因为模型低估了城市森林和公园的异戊二烯浓度 0.6-1.4 ppb。我们的研究表明，生物源 VOC 可以在热浪期间大大加剧空气污染。我们强调了植被在温暖季节对城市空气质量和人类健康的双重作用，即去除和减轻与增强空气污染。我们的研究结果表明，减少人为来源的氮氧化物、VOC 和 PM 等，例如减少机动车数量，将不得不伴随城市植树运动，以使它们真正有益于城市居民。
