Secondary aerosol sources

The source contributions of aerosol formed from gaseous emissions, such as sulfate, nitrate and certain organic species, cannot be quantified by chemical mass balance methods, Watson (9>) proposes a unique source type which will put an upper limit on the contributions of secondary aerosol sources, but it cannot attribute those contributions to specific emitters. 

Identification of chemical tracers for the wide variety of organic combustion and secondary aerosol sources, which can be used to identify and quantify source contributions to ambient aerosol. For the health effects community, it would especially valuable to have simple indicators of sources, which need not be highly accurate but can be easily measured and used to correlate source contributions with health criteria. 

The ablated vapors constitute an aerosol that can be examined using a secondary ionization source. Thus, passing the aerosol into a plasma torch provides an excellent means of ionization, and by such methods isotope patterns or ratios are readily measurable from otherwise intractable materials such as bone or ceramics. If the sample examined is dissolved as a solid solution in a matrix, the rapid expansion of the matrix, often an organic acid, covolatilizes the entrained sample. Proton transfer from the matrix occurs to give protonated molecular ions of the sample. Normally thermally unstable, polar biomolecules such as proteins give good yields of protonated ions. This is the basis of matrix-assisted laser desorption ionization (MALDI). 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Secondary , in Chemical Composition of the Atmospheric Aerosol Source/Air Quality Relationships, E.S. Macias and P.K. Hopke, Eds., A.C.S. Symposium Series, 1981. 

Particulate carbon in the atmosphere exists predominantly in three forms elemental carbon (soot) with attached hydrocarbons organic compounds and carbonates. Carbonaceous urban fine particles are composed mainly of elemental and organic carbon. These particles can be emitted into the air directly in the particulate state or condense rapidly after Introduction into the atmosphere from an emission source (primary aerosol). Alternatively, they can be formed in the atmosphere by chemical reactions involving gaseous pollutant precursors (secondary aerosol). The rates of formation of secondary carbonaceous aerosol and the details of the formation mechanisms are not well understood. However, an even more fundamental controversy exists regarding... 

A further complication is the basic assumption of the statistical methods that source profiles neither change during air transport nor with time. Therefore they cannot be applied strictly to secondary aerosol constituents formed in the atmosphere by gas-to-particle conversion processes. Still, the secondary aerosol constituents tend to be grouped into one source group since they have a common source , i.e. formation in air triggered by solar irradiation. 

A receptor model analysis in western Germany separated nitrate-rich from sulphate-rich secondary aerosols, with the latter being accompanied with vanadium and nickel [7]. Such factor composition pinpoints to heavy oil combustion sources which can be found, e.g. in oil refineries, off-shore platforms and overseas ships. In addition, trans-boundary pollution from eastern European countries is a significant source. 

Nitrate-rich secondary aerosol, mainly composed of ammonium nitrate, on the other hand, is predominantly formed on medium spatial scale and hence may have its major origin within Germany. Large sources for NH3, one of the aerosol precursor compounds, are located in the agricultural areas of north-western Germany ( Swine belt ). The other precursors, oxides of nitrogen, stem mainly from industrial and traffic-related combustion sources. 

Industrial emissions may contribute significantly to the PM10 burden at selected receptor sites as was also shown using the Lenschow approach. To a large part this assessment is due to the assignment of measured secondary aerosol components to industrial emissions of sulphur dioxide and nitrogen oxides which are not produced locally. Statistical receptor models like PMF, on the other hand, are able to identify local industrial impacts which can be seen in elevated levels of trace compounds, but hardly attribute secondary aerosol compounds to any specific industrial source. For example, a PMF study was carried out for a receptor site located a few... 

Keywords Aerosol, Emission sources, Greece, Mediterranean Basin, Particulate matter, Road dust, Sahara dust, Secondary aerosol, Ship emissions... 

Particles in the atmosphere arise from natural sources, such as windbome dust, sea spray and volcanoes, and from anthropogenic activities, such as combustion of fuels. Emitted directly as particles (primary aerosol) or formed in the atmosphere by gas-to-particle conversion processes (secondary aerosol), atmospheric aerosols are generally considered to be the particles that range in from a few nanometres to tens of micrometres in diameter [1]. 

Globally, and as put forward by Gelencser (2004), it is possible that to a certain extent all pathways for secondary aerosol WSOM formation could occur this would explain the ubiquitous nature and abundance of WSOM in atmospheric aerosol. What is known for certain is that biomass burning is a primary source of WSOM. Its secondary origin, however, still is under discussion and awaits proper experimental support. 

Carbonaceous aerosols in the atmosphere are complex in nature and are found in both coarse particles (> about 2.5 pm) and fine particles (< about 2.5 pm). Sources of carbon-containing particles are varied and include resuspended soil particles, pollen, plant waxes, etc. in the coarse fraction, and soot particles, sorbed organics including PAHs, and secondary aerosols resulting from... 

The ablated vapors constitute an aerosol that can be examined using a secondary ionization source. Thus, passing the aerosol into a plasma torch provides an excellent means of ionization, and by such methods isotope patterns or ratios are readily measurable from otherwise intractable materials such as bone or ceramics. 

Presently very little is known about the atmospherie behaviour of nitrophenols and nitrocresols. The aim of the present study is to increase our knowledge with respeet to the fate of this compound class under simulated tropospheric conditions in the laboratory. Reeent smdies in our laboratory on the photolysis of nitrophenol and nitroeresols with aetinie lamps (Philips TL 05/40 W 320 < k< 480, Xmax = 360 nm) have indieated that these eompounds could be important secondary organic aerosol sources (Bejan et al., 2003). In order to assess the importance of this aerosol formation pathway for the atmosphere, kinetie information concerning other atmospherie loss processes, e.g. reactions with OH and NO3 radicals, is required. 

In this section we describe the methodology used to study the effect of emissions from the local sources of atmospheric pollution on the processes of secondary aerosol formation. The basic admixtures selected as the main objects of investigations were dust and oxides of sulphur and nitrogen which are the main components of die emissions from the industrial... 

Formation of combustion particles also involves nucleation and condensation of vapors, although the processes occur at elevated temperatures inside the combustion source and during cooling of the plume. Like secondary aerosols, combustion particles have a major semivolatile component composed of sulfates from sulfur dioxide oxidation and organic oxidation products, and of unburned fuel and oil as well. Furthermore, they contain a large non-volatile component consisting of soot, metals, and metal oxides. 

The total rate of aerosol pnoduction is of the order of 2000 Tg/yr. Some comparisons are of interest. Anthropogenic sources, both direct and indirect, contribute about 15% to the global aerosol production rate. The percentage of direct emissions from anthropogenic sources is only about 20% of the total contribution, so that most of it derives from gas-to-particle conversion. With regard to natural aerosol formation, the percentage contribution of direct emissions is 60%, so that direct and secondary aerosol production are approximately equivalent. 

The sources and chemical compositions of the fine and coarse urban particles are different. Coarse particles are generated by mechanical processes and consist of soil dust, seasalt, fly ash, tire wear particles, and so on. Aitken and accumulation mode particles contain primary particles from combustion sources and secondary aerosol material (sulfate, nitrate, ammonium, secondary organics) formed by chemical reactions resulting in gas-to-particle conversion (see Chapters 10 and 14). 

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