Source tracers

Gryning, S. E., and Lyck, E., "Comparison between Dispersion Calculation Methods Based on In-Situ Meteorological Measurements and Results from Elevated- Source Tracer Experiments in an Urban Area." National Agency of Environmental Protection, Air Pollution Laboratory, MST Luft - A40. Riso National Laboratory, Denmark, 1980. 

The samples were analyzed for trace metals and sulfate as well as for three fractions of particulate organic matter (POM) using sequential extraction with cyclohexane (CYC), dichloromethane (DCM) and acetone (ACE). Factor analysis was used to identify the principal types of emission sources and select source tracers. Using the selected source tracers, models were developed of the form POM = a(V) + b(Pb) + - - -, where a and b are regression coefficients determined from ambient data adjusted to constant dispersion conditions. The models for CYC and ACE together, which constitute 90% of the POM, indicate that 40% (3.0 pg/m ) of the mass was associated with oil-burning, 19% (1.4 pg/m ) was from automotive and related sources and 15% (1.1 pg/m ) was associated with soil-like particles. 

Factor analysis was used to identify principal types of emission sources and to select elemental source tracers. As factor analysis has been described in detail in the literature (10-13), only a general description of the technique will be given... 

C. = the concentrations of source tracer elements k = the regression coefficients determined by least equates analysis ... 

Source Tracers. The principal anthropogenic sources of primary suspended particulate matter in New York City are transportation, fuel, oil combustion for power and space heating, and incineration (, 15). From approximately November through... 

Mathematical relationships between tracer elements and organics will be affected by both physical and chemical factors. Thus, it was anticipated that relationships between POM fractions and source tracers would be more readily apparent if these species were all measured for samples of the same particle-size "cut" (1 ). This was confirmed by some preliminary investigations of relationships between POM in RSP samples and tracer elements in TSP samples in which few correlations were found. As POM is found largely in particles < 3.5 ym aerodynamic diameter... 

As can be seen in Table I, particularly in No. 1, the source tracers in the TSP and RSP samples tend to factor out together, with the exception of manganese. Manganese can be used as a soil tracer (, 1, 20) in areas in which there are no other large sources of this element, such as steel manufacturing. 

Based on these results and considerations, it was concluded that Pb, V, Cu and SO. could be used as source tracers for automotive sources, oil-burning, incineration and secondary (or sulfate-associated) sources, respectively. Mn, however, should probably be considered as a composite tracer of automotive emissions and soil-related sources (resuspension of dust). 

Based on the results of the factor analysis, V, PB, CU, and MN(C) were chosen as source tracers for oil-burning, automobile emissions, incineration and resuspended soil, respectively. 

Source Apportionment Models for the Cyclohexane-Soluble Fraction of Respirable Suspended Particulate Matter. Stepwise multiple regression analysis was used to determine the coefficients of the source tracers for the models proposed for CYC in equations (7)-(9). These models are shown in Table IV. As expected from the factor analyses, the coefficient for V, accounting for the greatest proportion of the variance of CYC, was fitted first into the equation. Equation (14) was the simplest and the F value was slightly higher than for equations (15) and (16). In addition, as will be discussed later in this paper, the coefficient for PB was in reasonable agreement with the ratio of CYC /PB for samples collected in the Allegheny Tunnel. 

The most appropriate models for CYC is probably equation (14) as this is the simplest and is most closely related to the results of the factor analysis which indicated that the variances in CYC were most closely related to those in V and PB. The inclusion of coarse particle manganese as a soil tracer diminished the significance of the coefficient of PB and the contribution of automotive sources. Ideally, MN would be used as a tracer for resuspended soil but Interferences from the use of MMT as a fuel additive during part of the period in which this data were collected make this a mixed source tracer for the contributions of automobiles and soil resuspension. 

The data were analyzed first by factor analysis. Depending upon the number of variables included in the analysis, three to five factors were obtained which could be associated with emission sources or with meteorology. The source tracers V, Pb, Cu and... 

Comparisons of the regression coefficients of the source tracer elements with available source emission data, as well as comparisons with estimated source emission data for total suspended particulate matter, provide evidence of the validity of the models. 

Zweidinger, R. B., R. K. Stevens, C. W. Lewis, and H. Westburg, Identification of Volatile Hydrocarbons as Mobile Source Tracers for Fine-Particulate Organics, Environ. Sci. Technol., 24, 538-542 (1990). 

One means to assess the relative contributions of the various sources of sulfur to the atmosphere is through the use of sulfur isotope ratios (12-16). Isotopic ratios may be used as source tracers if 1) the isotopic composition of the sources as they enter the atmosphere are known, 2) the isotopic compositions of the various sources are different from one another, and 3) the isotopic changes that occur during biological, physical and/or chemical transformations are understood. Presently, isotopic data for sulfur compounds in the remote atmosphere (Table I) are limited. However, collection and analytical techniques are now available to make isotopic measurements of the critical species. In the text that follows, various aspects of sulfur isotope chemistry will be discussed. 

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