[Grabmer2004] "Disjunct eddy covariance measurements of monoterpene fluxes from a Norway spruce forest using PTR-MS",
International Journal of Mass Spectrometry
, vol. 239, no. 2: Elsevier, pp. 111–115, 2004.
Interest in reliable quantification of organic trace compounds released from terrestrial ecosystems stems from their impact on oxidant levels such as ozone and hydroxyl radicals and on secondary organic aerosol formation. In an attempt to quantify these emissions, a disjunct sampler (DS) was coupled to a PTR-MS instrument. In the disjunct eddy covariance (DEC) technique, an instantaneous grab sample is taken at intervals of tens of seconds and vertical wind speed is recorded at the instant of sample collection. The intermittent periods are used for sample analysis by a moderately fast chemical sensor, in this case a PTR-MS instrument, which allows for fast and sensitive detection of biogenic volatile organic compounds. The vertical turbulent transport of a trace compound is then calculated from the covariance of the fluctuations in vertical wind speed and compound mixing ratio. Fluxes of monoterpenes from a Norway spruce forest were measured during the 2002 summer intensive field campaign of BEWA2000 and results compared well with data obtained using relaxed eddy accumulation (REA) and the enclosure approach. In addition to this field experiment, a laboratory test was carried out to validate the disjunct sampling procedure.
[Beauchamp2004] "Short-term measurements of CO, NO, NO< sub> 2, organic compounds and PM< sub> 10 at a motorway location in an Austrian valley",
, vol. 38, no. 16: Elsevier, pp. 2511–2522, 2004.
In situ measurements of CO, NOx, PM10 and certain organic compounds took place over an 11 day period encompassing a 12 h motorway blockade. Located within the Inn valley (Tirol, Austria), the monitoring site experiences varying meteorological conditions and traffic frequency throughout the day which both strongly influence air pollutant levels. Early morning increases of NOx, PM10 and aromatic hydrocarbons were clearly correlated with rising traffic. Midday minima and afternoon maxima may be explained by changing wind conditions and varying inversion layer dynamics. Night time lows in concentrations can be explained by minimal traffic activity. Classification of compound sources was made through grouping of data, separated into times when heavy duty vehicles (HDV) were permitted to use the motorway and HDV-ban periods. Increased levels of NOx and PM10 were observed from data that included periods of high HDV numbers, with levels decreasing significantly during HDV-ban periods. In contrast, the aromatic hydrocarbons and CO displayed only minor variations between these two periods. Furthermore, on typical workdays NOx levels reached a maximum that corresponded to a peak in HDV numbers, whereas the aromatic compounds peaked later when LDV numbers had reached their maximum. Our findings give strong evidence that increased NOx and PM10 levels can be predominantly attributed to HDV traffic. Principal components analyses for the separated data further support this conclusion.