Evaluation of anthropogenic emissions of carbon monoxide in East Asia derived from the observations of atmospheric radon-222 over the western North Pacific

Abstract

Abstract. We used the observed CO/ 222 Rn ratio in the Asian outflows at Minamitorishima (MNM), Yonagunijima (YON), and Ryori (RYO) in the western North Pacific from 2007 to 2011, together with a three-dimensional chemical transport model (STAG), in order to estimate anthropogenic emissions of CO in East Asia. The measurements captured highfrequency synoptic variations of enhanced 222 Rn (ERN) events associated with the long-range transport of continental air masses. 222 Rn and CO showed high correlation during the ERN events observed at MNM and YON in the winter and spring, but not at RYO. The STAG transport model reproduced well the concentrations of observed 222 Rn when forced with a constant and uniform flux density of 1.0 atom cm −2 s −1 , but underestimated the associated enhancement of synoptically variable CO caused by the underestimated flux values in the EDGAR ver. 4.1 emission database used in the model for East Asia. Better estimates for the East Asian emission were derived using a radon tracer method based on the difference in the enhancement ratio of CO/ 222 Rn between the observation and the model. The anthropogenic emissions of CO for China, Japan, and Korea were estimated to be 203 Tg CO yr −1 , 91 % of which originated in China. When compared with other estimated emissions of CO, our estimated result showed consistency with those of the inverse method, whereas the emission database of EDGAR was about 45 % smaller than our anthropogenic estimation for China.

Towards a Universal “Baseline” Characterisation of Air Masses for High- and Low-Altitude Observing Stations Using Radon-222

“…An internal flow loop operates at approximately 4-5 times the sampling flow rate in order to maximise the number of newly formed radon progeny that are trapped for counting on a second filter before they decay or plate-out on the detector walls or internal components. This measurement configuration typically results in a detection level for an hourly count that is almost an order of magnitude lower than that of other common techniques of direct radon measurement (e.g., electrostatic precipitation, lower limit of detection, LLD = 160 mBq m -3 ; Wada et al, 2012).…”

Increasing the accuracy and temporal resolution of two-filter radon–222 measurements by correcting for the instrument response

“…1). The model is based on the one described by Whittlestone and Zahorowski (1998), but with additions which were needed for an unbiased fit to observations necessary for deconvolution. The model is described in full alongside a description of the detector itself.…”

“…Following the notation of Whittlestone and Zahorowski (1998), radioelement concentrations in air are given in number densities (atoms m −3 ), using the symbols shown in Fig. 2: N Rn for radon-222, N A for polonium-218, N B for lead-214, and N C for bismuth-214.…”

“…Equation (2) differs from the Whittlestone and Zahorowski (1998) model in two ways. First, the last term in Eq.…”

“…One of the challenges of using radon as a tracer is that emissions are small (∼ 1 atom cm −2 s −1 ; Zhang et al, 2011) and ambient concentrations are low. Low-level atmospheric measurements are therefore a niche served largely by instruments built in-house (Frank et al, 2012;Levin et al, 2002;Schmithüsen et al, 2016;Wada et al, 2010Wada et al, , 2012Whittlestone and Zahorowski, 1998;Grossi et al, 2012). The dual-flow-loop two-filter radon detector (Whittlestone and Zahorowski, 1998;Chambers et al, 2011) is the focus of this paper.…”