Back-trajectory analysis

Back electron-transfer (BET), peroxyoxalate chemiluminescence, 1268 Back trajectory analysis, analytical methods, 624... 

Figure 3.2. Annual emissions of sulfur dioxide and nitrogen oxides for the source area of the Hubbard Brook Experimental Forest. The source area was determined by 24-hour back trajectory analysis. Shown are emissions from both U.S. and Canadian sources...

Three techniques have been used to determine how much sulfur pollution is transported from one region to another computer simulation, back-trajectory analysis, and trace-element analysis. Each technique has confirmed the importance of longdistance transport. 

Computer simulation The distance that air pollutants are carried downwind can be estimated on a computer using data for the location of the emitters, the amount of pollution emitted and the direction and speed of the wind. " (More sophisticated computer programs also include the height of the smokestack, since wind speed varies with altitude.) The calculations also require estimates for how fast the pollution returns to earth. This will depend on how strongly SO2 and acid sulfate interact with the ground, and will involve estimates for the relative abundance of SO2 and sulfate in the air, which in turn depends on variables such as the amount of sunlight, the presence of other pollutants, the humidity, etc. (see Chapter 3). As a result of these uncertainties, computer simulations only provide estimates, not exact results. Nevertheless, the results from several computer simulations have agreed well with the experimental observations from back-trajectory analysis and other techniques (discussed below). 

By itself, back-trajectory analysis cannot determine precisely where along the trajectory a storm has picked up pollution. However, the location of the major emitters is known from in-... 

Source apportionment studies are frequently complemented by air mass origin analyses to identify where high pollution levels or certain compounds of interest come from. For small to meso scales this can be done by, e.g. wind rose analysis, whereas long-range transport is better assessed by using back trajectories calculated by a suitable dispersion model [20],... 

More recently, a statistical analysis of back trajectories [28] was carried out for the years 2005-2009 and five German regions. For each region, 12 trajectory clusters were identified (example shown in Fig. 7a) and evaluated with respect to their seasonality and correlation with high PM10 levels. While regional to local sources appear to be more important in the two westerly regions, a pronounced... 

Trace element compositions of airborne particles are important for determining sources and behavior of regional aerosol, as emissions from major sources are characterized by their elemental composition patterns. We have investigated airborne trace elements in a complex regional environment through application of receptor models. A subset (200) of fine fraction samples collected by Shaw and Paur (1,2) in the Ohio River Valley (ORV) and analyzed by x-ray fluorescence (XRF) were re-analyzed by instrumental neutron activation analysis (INAA). The combined data set, XRF plus INAA, was subjected to receptor-model interpretations, including chemical mass balances (CMBs) and factor analysis (FA). Back trajectories of air masses were calculated for each sampling period and used with XRF data to select samples to be analyzed by INAA. 

Dayan, U. (1986), "Climatology of back-trajectories from Israel based on synoptic analysis", J. Climate Appl. Meteorol., 25, 591-595. 

The source analysis of measured pollution has been supported by back-trajectory calculations. The trajec-tory model uses high-resolution ECMWF-analyzed meteorological data, as described by M.P. Scheele, P.C. Siegmund, and P.F.J. van Velthoven [Meteorological Applications, 3 261 (1996)]. 

Dispersion Model (Draxler and Rolph, 2003 Rolph, 2003). An example of the calculated air front tfajectories is shown in Figure 6. Rain events were classified in different categories according to their origin, as derived from 120 h air back mass trajectories based on 1000 and 3000 m as for the altitude. From the analysis of these trajectories westerly air fronts appear to be the most frequent (Figure 7). 

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