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To quantify CH4 emissions at policy-relevant spatial scales, the Korea Meteorological Administration (KMA) started monitoring its atmospheric levels in 1999 at Anmyeondo (AMY) and expanded monitoring to Jeju Gosan Suwolbong (JGS) and Ulleungdo (ULD) in 2012. The monitoring system consists of a cavity ring-down spectrometer (CRDS) and a new cryogenic drying method, with a measurement uncertainty (68 % c.i. (confidence interval)) of ± 0.7–0.8 ppb. To determine the regional characteristics of CH4 at each KMA station, we assessed the CH4 level relative to local background (CH4xs), analyzed local surface winds and CH4 with bivariate polar plots, and investigated CH4 diurnal cycles. We also compared the CH4 levels measured at KMA stations with those measured at the Mt. Waliguan (WLG) station in China and Ryori (RYO) station in Japan. CH4xs followed the order AMY (55.3 ± 37.7 ppb) > JGS (24.1 ± 10.2 ppb) > ULD (7.4 ± 3.9 ppb). Although CH4 was observed in well-mixed air at AMY, it was higher than at other KMA stations, indicating that it was affected not only by local sources but also by distant air masses. Annual mean CH4 was highest at AMY among all East Asian stations, while its seasonal amplitude was smaller than at JGS, which was strongly affected in the summer by local biogenic activities. From the long-term records at AMY, we confirmed that growth rate increased by 3.3 ppbyr-1 during 2006/2010 and by 8.3 ppbyr-1 from 2016 to 2020, which is similar to the global trend. Studies indicated that the recent global accelerated CH4 -growth rate was related to biogenic sources. However, δ13CH4 indicates that the CH4 trend in East Asia is derived from both biogenic and fossil fuel sources from 2006 to 2020. We confirmed that long-term high-quality data can help understand changes in CH4 emissions in East Asia. [ABSTRACT FROM AUTHOR]

Background: It is important to quantify changes in CO2 sources and sinks with land use and land cover change. In the last several decades, carbon sources and sinks in East Asia have been altered by intensive land cover changes due to rapid economic growth and related urbanization. To understand impact of urbanization on carbon cycle in the monsoon Asia, we analyze net CO2 exchanges for various land cover types across an urbanization gradient in Korea covering high-rise high-density residential, suburban, cropland, and subtropical forest areas. Results: Our analysis demonstrates that the urban residential and suburban areas are constant CO2 sources throughout the year (2.75 and 1.02 kg C m−2 year−1 at the urban and suburban sites), and the net CO2 emission indicate impacts of urban vegetation that responds to the seasonal progression of the monsoon. However, the total random uncertainties of measurement are much larger in the urban and suburban areas than at the nonurban sites, which can make it challenging to obtain accurate urban flux measurements. The cropland and forest sites are strong carbon sinks because of a double-cropping system and favorable climate conditions during the study period, respectively (− 0.73 and − 0.60 kg C m−2 year−1 at the cropland and forest sites, respectively). The urban area of high population density (15,000 persons km−2) shows a relatively weak CO2 emission rate per capita (0.7 t CO2 year−1 person−1), especially in winter because of a district heating system and smaller traffic volume. The suburban area shows larger net CO2 emissions per capita (4.9 t CO2 year−1 person−1) because of a high traffic volume, despite a smaller building fraction and population density (770 persons km−2). Conclusions: We show that in situ flux observation is challenging because of its larger random uncertainty and this larger uncertainty should be carefully considered in urban studies. Our findings indicate the important role of urban vegetation in the carbon balance and its interaction with the monsoon activity in East Asia. Urban planning in the monsoon Asia must consider interaction on change in the monsoon activity and urban structure and function for sustainable city in a changing climate. [ABSTRACT FROM AUTHOR]

Although monitoring greenhouse gases (GHG) is of crucial significance in addressing global climate change, contemporary GHG measuring equipment is expensive, bulky, and installed in only a few areas, leading to several limitations for responding in real-time. Besides, there are difficulties in measuring atmospheric constitutions in living spaces due to problems caused by the detection method that is used in measuring devices and the limits of observation incurred by spatial and operational contingencies. Here, we report a graphene-based photoelectric detector that provides low-cost and high-precision monitoring of GHGs, irrespective of the contiguity of the gas to the sensor unit. The graphene photodetection materials, laminated under high temperature and pressure conditions, were designed as three-dimensional elements in order to optimally absorb light energy passed through the GHG layers. As a result, the photoelectric detector indicated accurate responsivity to 216 ppm of carbon dioxide, 0.06 ppm of carbon monoxide, and 0.88 ppm of mixed methane and carbon dioxide gas. Of greater interest, it showed a high responsivity of 45% when 12 μW/cm2 of incident light passed through 1.09 ppm of carbon monoxide atmosphere. Our study is at the cornerstone of building high-density GHG monitoring networks within cities and metropolitan areas. [Display omitted] [ABSTRACT FROM AUTHOR]