Carlos M. Rojas

Aerosols in Santiago de Chile: a study using receptor modeling with x-ray fluorescence and single particle analysis.

Between 15 January and 26 February 1987, 51 fine and coarse mode aerosol samples were collected at the Universidad de Santiago de Chile Planetarium using a dichotomous sampler. The samples were analyzed by X-ray fluorescence for up to 17 elements (Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br and Pb). Aerosol particles were individually studied by Electron Probe Microanalysis (EPMA) and Laser Microprobe Mass Analysis (LAMMA). The data set consisting of aerosol elemental concentrations and meteorological variables was subjected to Principal Factor Analysis (PFA), allowing the identification of six fine mode particle source classes (soil, industrial, sulfate particles, traffic, residual oil, wood-burnings), and five coarse mode particle source classes (soil, industrial, traffic, residual oil, sulfate particles). Both PFA solutions explained about 81 and 90% of the total variance in the data set, respectively. The regression of elemental mass concentrations on the Absolute Principal Factor Scores allowed the estimation of the contribution of the different source classes to the Santiago aerosol. Within the fine fraction, secondary SO42− particles were responsible for about 49% of the fine mode aerosol mass concentration, while 26, 13, 6.4 and 5.6% were attributed to wood-burning/car exhausts, residual oil combustion, soil dust/metallurgical, and soil dust/wood-burning releases, respectively. The coarse fraction source apportionment was mainly dominated by soil dust, accounting for 74% of the coarse mode aerosol mass concentration. A composite of soil dust and industrial release accounted for 13%; a composite of secondary sulfates contributed with 9%; a composite of soil dust and automotive emissions, and secondary sulfates were responsible for 4 and 0.03% of the coarse aerosol mass concentration, respectively. EPMA results are in satisfactory agreement with those from the bulk analysis and allowed the identification of eight particle types in both fine and coarse mode aerosols, pertaining to different source classes, namely soil, seaspray, secondary SO42−, metallurgical emissions and biomass burning release. EPMA also evidenced that one of the most abundant particle types corresponded to marine aerosol, having an average diameter of 0.7 μm for the fine mode and 2.2 μm for the coarse mode aerosol. LAMMA results indicate that, in fact, seaspray has been transported into the city of Santiago de Chile airshed, suffering several transformations and a sulfur enrichment. This analytical technique also provided evidence of the abundance of carbon-rich particles, which were not detected by either the bulk X-ray analysis or EPMA; they are probably due to fossil-fuel combustion releases.

Dry and wet deposition fluxes of Cd, Cu, Pb, and Zn into the Southern Bight of the North Sea

Abstract During the period from September 1988 to October 1989, 23 sampling flights were carried out over the Southern Bight of the North Sea. In this campaign, both bulk and size-segregated airborne particulate matter samples were collected. Dry deposition velocities for Cd, Cu, Pb and Zn have been estimated using a modified version of the two-layer of Slinn and Slinn and the particle size distribution obtained from size-fractionated samples. Results pointed out that the main difference between our results and those reported in the literature lies in the aerosol size distribution. Dry deposition rates calculated using these deposition velocities as a function of wind sector showed that continental air masses, particularly those associated with the wind sector west/southwest, are predominant in the deposition process. Wet flux estimates were carried out using Slinns approach. Results were also classified taking into account different wind sectors. Here, the wet flux of Pb and Zn is mainly related to wind sectors east/northeast, south/southeast and local, the latter represents air masses with variable origin; whereas those of Cd and Cu correspond to wind sectors west/southwest and south/southeast. Results showed that wet deposition is responsible for almost 70% of the total deposition into the Southern Bight of the North Sea. However, some topics, like heavy metal content in large aerosol particles, temporal distribution of precipitation events, variation of precipitation intensity aloft, need better knowledge before accurate assessments can be made.

Electron microprobe characterization of individual aerosol particles collected by aircraft above the southern bight of the North Sea

Abstract About 50,000 individual aerosol particles from a total of 108 samples collected at six different altitudes above the Southern Bight of the North Sea, have been analysed using electron probe X-ray microanalysis. The results of hierarchical cluster analysis on each sample revealed that, for continental air masses, most of the aerosol particulate matter is characterized by high amounts of aluminosilicates, CaSO4 and Fe-rich particles. For western and marine air masses there was no change in the composition of the most abundant particle type with height. This is in connection with the rather mixed nature of the atmosphere. Non-hierarchical cluster analysis showed that the most abundant particle types in this airshed are: aluminosilicates from coal combustion releases, Fe-rich, sea salts enriched with Pb, and organic material associated with residual oil combustion tracers, accounting for 21, 16, 15 and 12% of the total analysed particles, respectively. Almost 60% of the analysed particles is related to combustion or energy-generation processes. Principal factor analysis on an elemental frequency matrix led to comparable results with principal factor analysis used in combination with cluster analysis. This shows that the method described here is useful for the identification of aerosol sources.

THE ELEMENTAL COMPOSITION OF AIRBORNE PARTICULATE MATTER IN THE ATACAMA DESERT, CHILE

Abstract Air particulate samples were collected at Chapiquina near Arica (Chile) with a six-stage cascade impactor for about 17-day periods during a 31 month interval. Sixteen elements were determined by energy dispersive X-ray fluorescence analysis, and the elemental concentrations were subjected to principal factor analysis. The variability with time of the coarse particles was described by two factors both related to soil dispersion, whereas the fine particle variations could be explained by a third factor related to marine influence. Enrichment factors were compared with those obtained in other remote continental areas, in particular those of air particulate matter sampled at Chacaltaya, Bolivia. Results point to a negligible anthropogenic influence.

Comparison of three dry deposition models applied to field measurements in the Southern Bight of the North Sea

Abstract Dry deposition velocities have been calculated using three different approaches. Turbulent wind profile theory has been used to predict the drag coefficient, wind speed and friction velocity at 10 m height when the wind speed is measured at a higher altitude. The resulting parameters were introduced in a two-layer deposition model. The second approach was the well-known model of Slinn and Slinn (1980, Atmospheric Environment14, 1013–1016), whereas the third corresponded to the model published by Williams (1982, Atmospheric Environment16, 1933–1938). Results point to clear differences. However, in a field experiment carried out at the Southern Bight of the North Sea, all three approaches show relatively comparable results. The role played by the size distribution of atmospheric particulate matter is essential. In our case any of the three models could have given satisfactory outcomes taking into account the wide spread of the experimental results cited in the literature for the same airshed.

Elemental composition of aircraft-sampled aerosols above the Southern bight of the North Sea

During the period from September 1988 to October 1989, 23 flights were carried out over the Dutch Continental Shelf of the North Sea and a total of 108 aerosol filter samples were collected. The samples were analyzed for Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br and Pb using both particle-induced X-ray emission (PIXE) and energy-dispersive X-ray fluorescence (EDXRF). The results from PIXE exhibited better precision and lower detection limits than those from EDXRF. Therefore the further discussion and interpretation was based on the PIXE data only. It was observed that Si, S, V, Mn, Ni, Cu and Pb were enriched with respect to the earths crust. It was seen that winds from the sector Southeast-South contributed most significantly to the total aerosol concentration. The vertical profiles of several elements indicated that their concentration increases with proximity to the sea. Principal factor analysis on the data matrix containing elemental concentrations, height and wind direction parameters allowed us to identify 6 possible aerosol sources, namely, a composite of CaSO4 and metallurgical activities, refuse incineration, residual oil combustion, quartz, soil dust and sea-salt aerosol.

Composition and sources of atmospheric particulate matter at Kayseri, central Turkey

A total of 166 atmospheric particulate matter samples were co!!~ted from three different !ocatiens in the city of Kayseri, Central Anatolia, Turkey, during the period from January 1986 to October, 1988. The aerosol samples were analyzed for AI, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br and Pb by energy-dispersive X-ray fluorescence. The results indicated that the aerosol elemental composition at Kayseri is mainly dominated by secondary sulfates, reaching an average concentration of up to 34 t~g m -3. It was observed a much higher elemental concentration of those species associated with anthropogenic activities, compared with those from another urban a~rshed with similar characteristics. Enrichment factor calculations showed that the anomalously enriched elements were S, Cr, Ni, Cu, Zn and Pb. The seasonal variability of the elemental concentrations was studied using Si and S. The former was thought to be representative of a natural aerosol, while the latter was associated with anthropogenicaily generated elements. Multivariate analysis of the data base containing the element0t concentrations allowed the identification of five different aerosol sources, namely: secondary sulfates, residual oil combustion, industrial emissions, car exhausts and soil dust.

Penetration of atmospheric aerosols during collection in cellulose filters, studied by secondary ion mass spectrometry

The penetration of aerosol particles in a Whatman-41 cellulose filter has been studied via the depth profiles of different elements present in the aerosol. Depth profiles were obtained by analyzing both fine and coarse fractions from a dichotomous sampler by secondary ion mass spectrometry. The fine particles had an aerodynamic diameter dae of less than 2.5 μm, whereas the coarse fraction had 2.5 ≤ dae ≤ 15 μm. Elements such as Al, Si, Ca, Ti and Fe were associated with coarse airborne particles, while S, Cl, Zn, and Br were more abundant in the fine fraction. Results showed that particle size plays an important role in the distribution of particulate matter throughout the filter. SiTi-containing particles were mostly deposited near the surface of the filter, and their profiles can be estimated using a polynomial function, whereas the profile of AlCaFe-containing particles can be approached by an exponential decay function. Elements associated with fine fraction aerosols mainly originating from combustion processes, can penetrate up to about 25% of the total filter thickness, and their profiles are better represented by a diffusion function.

Dry Aerosol Deposition Over the North Sea Estimated from Aircraft Measurements

A mathematical approach based on the Monin-Obukhov similarity theory is used to predict the wind speed, friction velocity and drag coefficient, which are then introduced in the well-known deposition model of Slinn and Slinn (1980), to calculate the dry deposition of heavy metals into the North Sea. This model is perfectly suitable for aircraft sampling considering the fact that usually due to safety reasons, flights at the reference height used in deposition models (10 m), are not possible. To check this approach, deposition velocities were calculated based on the airborne concentrations of Cu, Cd, Zn and Pb obtained by sampling with the aid of an aircraft over the Dutch continental shelf of the North Sea. Results are in agreement with those found in the literature. A rough estimation of the atmospheric input for these heavy metals and comparison with riverine inputs and direct discharges is also included.

Fluxes and Sources of Heavy Metal Inputs into the Southern Bight of the North Sea

Chemicals, both natural and man-made, reach the North Sea through a number of different routes. For many years, research on pollution of the marine environment has focused on the most obvious inputs: those borne by rivers and direct discharges of waste. However, a number of studies conducted at the end of the 1970’s and at the beginning of the 1980’s revealed that a substantial fraction of the contamination entering the ocean, the North Sea and Baltic Sea, derives from sources located on land via atmospheric input. Gradually more importance has been given to the atmospheric route relative to the other pathways. The aim of this study was to estimate from field measurements the atmospheric input of some heavy metals into the Southern Bight of the North Sea, namely between the Dutch and English coast, for comparison with the input by other pathways, and to serve as a calibration reference for model calculations.