Anthropogenic CH4 Emissions in the Yangtze River Delta Based on A “Top-Down” Method

Wenjing Huang,Yongbo Hu,Jingzheng Xu,Cheng Hu,Wei Wang,Xuhui Lee,Shoudong Liu,Wei Xiao,Mi Zhang

doi:10.3390/atmos10040185

Abstract

There remains significant uncertainty in the estimation of anthropogenic CH4 emissions at local and regional scales. We used atmospheric CH4 and CO2 concentration data to constrain the anthropogenic CH4 emission in the Yangtze River Delta one of the most populated and economically important regions in China. The observation of atmospheric CH4 and CO2 concentration was carried out from May 2012 to April 2017 at a rural site. A tracer correlation method was used to estimate the anthropogenic CH4 emission in this region, and compared this “top-down” estimate with that obtained with the IPCC inventory method. The annual growth rates of the atmospheric CO2 and CH4 mole fractions are 2.5 ± 0.7 ppm year−1 and 9.5 ± 4.7 ppb year−1, respectively, which are 9% and 53% higher than the values obtained at Waliguan (WLG) station. The average annual anthropogenic CH4 emission is 4.37 (± 0.61) × 109 kg in the YRD (excluding rice cultivation). This “top-down” estimate is 20–70% greater than the estimate based on the IPCC method. We suggest that possible sources for the discrepancy include low biases in the IPCC calculation of emission from landfills, ruminants and the transport sector.

Highlights

The source apportionment of CH4 is important for the study of carbon cycle and climate change.The mole fraction of CH4 in the atmosphere increased by 157% from 1750 to 2011 [1,2]
There is slight variations between the four seasons according to the national level fuel consumption [58], so we focused on wintertime (December to February inclusive) measurements because plant photosynthesis is minimal and atmospheric CO2 variations are driven primarily by anthropogenic sources
Data for 2014 and 2015 are nearly gap-free and are representative of Figure 4 shows the temporal variations of half-hourly atmospheric CH4 and CO2 mole fractions seasonal variations

Summary

Introduction

The source apportionment of CH4 is important for the study of carbon cycle and climate change. The mole fraction of CH4 in the atmosphere increased by 157% from 1750 to 2011 [1,2]. As the second largest greenhouse gas next to CO2 , CH4 has a warming potential of 28 times that of CO2 with a. 100-year time horizon [2]. In addition to the greenhouse effect, CH4 affects the chemical and photochemical reactions in the atmosphere [3]. The annual growth rate of atmospheric CH4 was. 6.9 ± 2.4 ppb year−1 from 2007 to 2017 [4]. The source contributions of CH4 have so far not been accurately quantified, especially at the regional and the city scale [5]

Methods

Results

Discussion

Conclusion