Park Chaerin, Jeong Sujong, Park Moon-Soo, Park Hoonyoung, Yun Jeongmin, Lee Sang-Sam, Park Sung-Hwa
Department of Environmental Planning, Graduate School of Environmental Studies, Seoul National University, Seoul, Republic of Korea.
Department of Climate and Environment, Sejong University, Seoul, Republic of Korea.
Carbon Balance Manag. 2022 May 3;17(1):3. doi: 10.1186/s13021-022-00206-w.
Cities are a major source of atmospheric CO; however, understanding the surface CO exchange processes that determine the net CO flux emitted from each city is challenging owing to the high heterogeneity of urban land use. Therefore, this study investigates the spatiotemporal variations of urban CO flux over the Seoul Capital Area, South Korea from 2017 to 2018, using CO flux measurements at nine sites with different urban land-use types (baseline, residential, old town residential, commercial, and vegetation areas).
Annual CO flux significantly varied from 1.09 kg C m year at the baseline site to 16.28 kg C m year at the old town residential site in the Seoul Capital Area. Monthly CO flux variations were closely correlated with the vegetation activity (r = - 0.61) at all sites; however, its correlation with building energy usage differed for each land-use type (r = 0.72 at residential sites and r = 0.34 at commercial sites). Diurnal CO flux variations were mostly correlated with traffic volume at all sites (r = 0.8); however, its correlation with the floating population was the opposite at residential (r = - 0.44) and commercial (r = 0.80) sites. Additionally, the hourly CO flux was highly related to temperature. At the vegetation site, as the temperature exceeded 24 ℃, the sensitivity of CO absorption to temperature increased 7.44-fold than that at the previous temperature. Conversely, the CO flux of non-vegetation sites increased when the temperature was less than or exceeded the 18 ℃ baseline, being three-times more sensitive to cold temperatures than hot ones. On average, non-vegetation urban sites emitted 0.45 g C m h of CO throughout the year, regardless of the temperature.
Our results demonstrated that most urban areas acted as CO emission sources in all time zones; however, the CO flux characteristics varied extensively based on urban land-use types, even within cities. Therefore, multiple observations from various land-use types are essential for identifying the comprehensive CO cycle of each city to develop effective urban CO reduction policies.
城市是大气中一氧化碳的主要来源；然而，由于城市土地利用的高度异质性，了解决定每个城市净一氧化碳通量的地表一氧化碳交换过程具有挑战性。因此，本研究利用在韩国首尔首都圈九个不同城市土地利用类型（基线、住宅、旧城区住宅、商业和植被区）的站点进行的一氧化碳通量测量，调查了2017年至2018年期间城市一氧化碳通量的时空变化。
首尔首都圈的年一氧化碳通量从基线站点的1.09千克碳/平方米·年到旧城区住宅站点的16.28千克碳/平方米·年有显著差异。所有站点的月一氧化碳通量变化与植被活动密切相关（r = -0.61）；然而，其与建筑能源使用的相关性因土地利用类型而异（住宅站点r = 0.72，商业站点r = 0.34）。所有站点的日一氧化碳通量变化大多与交通流量相关（r = 0.8）；然而，其与流动人口的相关性在住宅（r = -0.44）和商业（r = 0.80）站点相反。此外，每小时的一氧化碳通量与温度高度相关。在植被站点，当温度超过24℃时，一氧化碳吸收对温度的敏感性比前一温度时增加了7.44倍。相反，非植被站点的一氧化碳通量在温度低于或超过18℃基线时增加，对低温的敏感性是高温的三倍。平均而言，无论温度如何，非植被城市站点全年每小时排放0.45克碳/平方米的一氧化碳。
我们的结果表明，大多数城市地区在所有时区都是一氧化碳排放源；然而，即使在城市内部，一氧化碳通量特征也因城市土地利用类型而有很大差异。因此，对各种土地利用类型进行多次观测对于确定每个城市的综合一氧化碳循环以制定有效的城市一氧化碳减排政策至关重要。
