SF6 releases and ground concentration during the field campaign of the Bolzano Tracer EXperiment (BTEX)

On 2017-02-14, two controlled releases of a passive and inert gas tracer (SF6) were performed into the stack of the incinerator (46.468345 N, 11.308716 E, 307 m ASL): one in the morning (under stable atmospheric conditions and light northerly winds) and one in afternoon (under weak unstable conditions and light southerly winds). At each release, samples of ambient air were collected at selected points in the surrounding area by means of vacuum-filled glass bottles and plastic bags. Tracer concentration in each sample was measured in the laboratories of Eco-Research s.r.l. by means of a GC-MS tipple quadrupole mass spectrometer (TSQ 8000 EVO from Thermo Scientific) with chemical ionization (CI) with methane as reagent gas. The obtained sensitivity allowed to measure down to background levels. In the year 2017 the background SF6 levels in the Bolzano basin were close to 10 ppt. To avoid the influence of the background, the quantification was performed at levels above 30 ppt.