Net CO₂ surface emissions at Bern, Switzerland inferred from ambient observations of CO₂, δ(O₂/N₂), and ²²²Rn using a customized radon tracer inversion

Abstract

The 222 Radon tracer method is a powerful tool to estimate local and regional surface emissions of, e.g., greenhouse gases. In this paper we demonstrate that in practice, the method as it is commonly used, produces inaccurate results in case of nonhomogeneously spread emission sources, and we propose a different approach to account for this. We have applied the new methodology to ambient observations of CO 2 and 222 Radon to estimate CO 2 surface emissions for the city of Bern, Switzerland. Furthermore, by utilizing combined measurements of CO 2 and δ(O 2 /N 2 ) we obtain valuable information about the spatial and temporal variability of the main emission sources. Mean net CO 2 emissions based on 2 years of observations are estimated at (11.2 ± 2.9) kt km À2 a À1 . Oxidative ratios indicate a significant influence from the regional biosphere in summer/spring and fossil fuel combustion processes in winter/autumn. Our data indicate that the emissions from fossil fuels are, to a large degree, related to the combustion of natural gas which is used for heating purposes.

Radon as a tracer of atmospheric influences on traffic-related air pollution in a small inland city

“…An optimum decay half-distance of around 2 km is found for benzene, which fits very well with the average radius of Bern being around 4 km (see Fig. 1; also considering a total area of 51.6 km 2 as noted by van der Laan et al, 2014). On the other hand, correlation coefficients for CO increase for decreasing half-distances, until a broad plateau is reached for all values below about 1 km.…”

“…This is likely to be incomplete combustion associated with idling vehicles, and possibly residential heating, in the central city district close to the measurement site. As noted in the study of van der Laan et al (2014), a significant fraction of the fossil fuel-based emissions in Bern are known to be from natural gas combustion associated with residential heating (e.g. 28% for CO 2 ).…”

“…A proxy frequently used for relative changes in mixing depth is the 'atmospheric stability', for which numerous measures based on in-situ meteorological measurements are available, varying considerably in sophistication and ease of application (e.g. Pasquill, 1961;Turner, 1964;Pasquill and Smith, 1983;Foken, 2006).…”

“…Of these sources, domestic heating would be expected to be significantly enhanced in wintertime. For CO, the likely additional source in Bern is incomplete natural gas combustion, again associated with enhanced wintertime domestic heating (ATSDR, 2012;van der Laan et al, 2014).…”

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

“…Radon measurements have been used to identify baseline air masses at atmospheric monitoring stations (Brunke et al, 2004;Chambers et al, 2014Chambers et al, , 2015aXia et al, 2013), for model validation (Considine et al, 2005;Jacob and Prather, 1990;Zhang et al, 2008), and for making land surface flux estimates (Biraud et al, 2000;Slemr et al, 2013;van der Laan et al, 2014). Radon has also been used as a tracer in recent studies of vertical mixing Griffiths et al, 2013;Williams et al, 2011Williams et al, , 2013Vargas et al, 2015) and in many earlier studies, some of which are reviewed by Zahorowski et al (2004).…”