Concentration of airbone trace metals in a bus station with a high heavy-duty diesel fraction

Abstract

Amostras de material particulado total (MPT) e MP 10 foram coletadas numa estação de ônibus, no período de agosto de 2006 a fevereiro de 2007. Na área, as únicas fontes importantes de emissão de poluentes são os ônibus, já que os veículos leves representam apenas 1-2% do fluxo total e não são desenvolvidas outras atividades no local. As concentrações de metais foram determinadas por espectroscopia de emissão por plasma indutivamente acoplado (ICP-OES). Os metais mais abundantes foram Ca, Mg, Fe e Al, que correspondem a 50,1%; 24,2%; 6,5% e 18,7%, respectivamente, do conteúdo metálico. O Co, Ni, Cd, Cr e Pb foram encontrados em níveis inferiores ao seu limite de detecção, exceto para algumas poucas amostras. Os fatores de enriquecimento calculados, mostram que o Zn e o Cu são devidos provavelmente à composição do combustível e do óleo lubrificante. O Ca, Mg e Al podem ser atribuídos à resuspensão de poeira, enquanto que o Fe pode ser devido tanto à ressuspensão de poeira como as emissões dos veículos.Total particulate matter (TSP) and PM 10 samples were collected in a bus station, in the period of August 2006 to February 2007. Buses are the only significant emission sources in this area once light duty vehicles represent about 1-2% of total flux and no other activities are developed in the location. Concentrations of metals in the samples were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Ca, Mg, Fe and Al were the most abundant elements and accounted for about 50.1%, 24.2%, 6.5% and 18.7% of the total metal content. Co, Ni, Cd, Cr and Pb were under detection limits except for a few samples. Calculated enrichment factors show that Zn and Cu are probably due to fuel and oil composition. Ca, Mg and Al may be attributed to dust resuspension while Fe may be due to both dust resuspension and contribution of vehicles.

Trace metals in the urban aerosols of Rio de Janeiro city

“…10 times higher than those obtained from our previous studies at the bus station. 13 The EF results are in close agreement with the calculated relative concentrations. Other metals, such as Ni, Cd and Pb, which are frequently identified as being of anthropogenic origin, were under their limits of detection and thus were not included in these calculations.…”

“…30 Additionally, metal-based oil additives containing Zn and Mg, Zn-based anti-wear agents and Ca-and Mg-based detergents are added to fuels and lubricating oils, influencing the sizes of emitted particles and their composition. 31 Our previous results from studies 13 at the bus station (TSP and PM 10 ) showed that for diesel emissions, Fe and Al were not enriched in the soil and were probably not due to vehicle emissions.For fine particles, Mn, Fe, Zn and Cu were presentin higher ratios than in crustal material. Because these particles mainly originate from combustion processes, being present in gasoline, oil and lubricants.…”

“…For the analysis of trace metals, the same procedures were followed as in our previous studies. 12,13,23 The filters were extracted by adding 5 mL of nitric acid (Merck Suprapur 65%), 2 mL of hydrochloric acid (Merck Suprapur 36%) and 10 mL of ultrapure water (18 MW cm -1 of specific resistivity) to a Pyrex tube and subsequently heating for 2 h at 95 °C on a heating plate. The extracted solution was filtered with a Whatman No.…”

“…The values determined for the diesel emissions were 50.2, 24.1, 18.7 and 6.5%, respectively for the same metals. 13 The differences are probably due to the composition of soils, aerosol particles, mechanical parts and , also, to the composition of fuels.To compare the results of the atmospheric particulate matter with motor emissions, the exhaust of a 1.8 gasohol engine was analyzed using the ABNT NBR 6601:2005 Protocol. The engine was operated with the gasohol that is currently used in Brazil.…”

“…43 It should be emphasized, however, that the flux calculations might vary by more than one order of magnitude due to differences in the methods used and the uncertainties in V d . Approximated values were estimated in order to compare our current data with data obtained in the bus station study 13 and in several locations in Salvador City (Bahia State, Brazil). 23 Calculated values are presented in Table 3.…”