Quantification of emission estimates of CO₂, CH₄ and CO for East Asia derived from atmospheric radon-222 measurements over the western North Pacific

Figures & data

Fig. 1.  Geographical locations of the observational sites of Minamitorishima (MNM) and Yonagunijima (YON).

Fig. 2.  Hourly mean observed atmospheric ²²²Rn concentration at MNM (a), YON (b). White circles indicate monthly mean concentration of ²²²Rn calculated from hourly mean data.

Fig. 3.  Time series of hourly mean concentrations of atmospheric ²²²Rn, CH₄, CO₂ and CO observed at MNM in January 2010. Arrows point to the peak of each enhanced ²²²Rn event. The dashed and solid lines for ²²²Rn (top panel) are the smoothed fitting curve and the upper threshold of smaller ΔRn variability, respectively. The black and grey dots represent the enhanced ²²²Rn (ERN) events and non-enhanced events, respectively (see text). The black dots for other gases relate to the corresponding periods of the ERN events.

Fig. 4.  Scatter plots of ΔCH₄, ΔCO₂ and ΔCO as a function of ΔRn observed at MNM in January 2010. The circles, crosses, diamonds and triangles represent enhanced ²²²Rn events of 4, 7, 8 and 10 in Fig. 3, respectively. The solid line represents the RMA regression for each event.

Fig. 5.  Scatter plots of ΔCH₄, ΔCO₂ and ΔCO as a function of decay-corrected ΔRn of the event of 4, 7, 8 and 10 in Fig. 3. The solid lines represent the RMA regressions for each plot.

Fig. 6.  Frequency distribution of the enhancement ratios of ΔCO/ΔRn, ΔCH₄/ΔRn and ΔCO₂/ΔRn for the ERN events observed at MNM and YON from December to April. The open and grey bars represent the observed and preformed enhancement ratios, respectively. Data with correlation coefficients greater than 0.5 are used here.

Fig. 7.  Simulated and observed atmospheric concentration of ²²²Rn at MNM (a) and YON (b) in 2010. The black dots represent 6-hourly mean observed ²²²Rn and the red solid line represents simulated ²²²Rn.

Fig. 8.  Contributive percentage and its grid-point distributions for the ²²²Rn tagged traced experiments for MNM (left panel) and YON (right panel). The resolutions of the grid are 5°×5° for MNM and 1.875°×1.875° for YON.

Fig. 9.  Identified catchment areas for MNM (a) and YON (b). The grey shaded area represents the identified catchment area, together with the CO emission field (red contour) of the EDGAR ver. 4.2.

Table 1. Comparison of estimated emissions of CO, CH₄, CO₂ for the catchment areas of MNM and YON

		MNM			YON
		CO	CH4	CO2	CO	CH4	CO2
	Reference year	TgCO yr^−1	TgCH4 yr^−1	PgC yr^−1	TgCO yr^−1	TgCH4 yr^−1	PgC yr^−1
This work	2007–2011 (MNM)	127	30	1.5^**	63	9	0.9^**
	2008–2011 (YON)	±31	±9.6	±0.5	±28	±2.9	±0.3
EDGAR ver. 4.2	2009^*	71	35	1.6	36	10	0.6
REAS	2009^*	104	No data	1.2	45	No data	0.6
CDIAC ver. 2011	2009^*	No data	No data	1.4	No data	No data	0.5

The error (±) represents the estimated uncertainties for the catchment areas.

*The emissions of EDGAR and CDIAC were calculated by extrapolation of the data from 2005 to 2008, and the emissions of REAS are predictions by linear interpolation between 2003 and 2010 (estimated).

**The biogenic CO₂ emissions based on CASA were subtracted from the ²²²Rn-derived CO₂ emissions.

Fig. 10.  Comparisons of the estimated emissions of CO, CH₄ and CO₂ between this study and three emission databases for the catchment areas of MNM and YON. The databases are derived from the EDGAR ver.4.2, REAS for 2009, CDIAC ver. 2011. The error bars represent the estimated uncertainties (see text).