The Aburrá Valley region in Colombia, with Medellín as its main city, is an urban centre with about three million people. An investigation was carried out to deter-mine a set of baseline concentrations for VOC compounds associated with diesel fuel and gasoline, as vehicular emission tracers in the region. The VOC measurement campaigns, based on TENAX tube sampling and analysis according to TO-17 EPA method, were done in areas of low and high vehicular flow as well as on-board measurements covering major Medellín road networks during 24 hours. The results showed that there was a relation between VOCs concentrations and vehicular activi-ty. The diesel fuel sulfur content was also found as an important factor on VOC hy-drocarbon formation.
VOCs tend to be polluting considering both their inhalation and contact effects and as a source of secondary pollutants. For the present study, they were classified into two (2) groups: poly-nuclear aromatic hydrocarbons (PAHs) and aliphatic hydrocarbons (AH).
The studied VOCs behave differently, following the two main types (alkanes [AH], and PAH) and this has to do with their molecular weight, as shown in the behavior of their vapor pressure and boiling point, properties that have to do with their presence in the atmosphere (
Compound | Molecular weight | Vapor pressure at 25˚C, mm Hg | Boiling temperature at atm. pressure, ˚C | Nature | Formula |
---|---|---|---|---|---|
n-Nonane | 128.3 | 4.45 | 150.6 | AH | C9H20 |
n-Decane | 142.3 | 1.43 | 174.2 | AH | C10H22 |
n-Undecane | 156.3 | 0.412 | 196.0 | AH | C11H24 |
n-Dodecane | 170.4 | 0.135 | 214.0 | AH | C12H26 |
n-Tridecane | 184.4 | 0.0560 | 232.0 | AH | C13H28 |
n-Tetradecane | 198.4 | 0.0116 | 253.0 | AH | C14H30 |
n-Pentadecane | 212.4 | 0.00310 | 268.0 | AH | C15H32 |
Naphthalene | 128.2 | 0.0850 | 218.0 | PAH | C10H8 |
1-Methylnaphthalene | 142.2 | 0.0670 | 240.0 | PAH | C11H10 |
2-Methylnaphthalene | 142.2 | 0.0550 | 241.0 | PAH | C11H10 |
Phenanthrene | 178.2 | 0.000121 | 332.0 | PAH | C14H10 |
1-Methylphenanthrene | 192.3 | 0.0000501 | 354.0 | PAH | C15H12 |
2-Methylanthracene | 192.3 | 0.0000727 | 353.5 | PAH | C15H12 |
A review [
In general, VOCs play an important role in environmental problems by their accumulation and persistence in the environment [
So far no studies of these compounds have been done locally, so it is deemed important to carry out an exploratory work, in parallel with the fact that sulphur content of diesel fuel is undergoing changes at the time, from 2000 to 50 ppm and it is desired to correlate those changes with the said VOCs concentrations.
Alkanes tend to be emitted by vehicles, as they are components of fuels.
Compound | Residence half time in air, hr | Health impact | Occupational limits |
---|---|---|---|
n-Nonane | 40.8 | Irritation eyes, skin, nose, throat; headache, drowsiness, dizziness, confusion, nausea, tremor, discordination | TLV: 200 ppm (1050 mg/m3) |
n-Decane | 33.2 | Irritation eyes, skin. Little impact | TLV Not established |
n-Undecane | 29 | No clear indication of risks | TLV Not established |
n-Dodecane | 27 | Irritation eyes, skin. Little impact | TEEL-0: Concentration below which people will experience no adverse health effects is 0.015 ppm (105 μg/m3) |
n-Tridecane | 24 | Irritating to eyes and skin. Inhalation causes irritation of the lungs and respiratory system. | TLV Not established |
n-Tetradecane | 19.2 | Irritation eyes, skin. Inhalation causes irritation of the lungs and respiratory system | TLV Not established |
n-Pentadecane | 17 | No clear indication of risks | TLV Not established |
Naphthalene | 18 | Irritating to skin and eyes | TWA 10 ppm (50 mg/m3) |
1-Methylnaphthalene | 7.3 | Irritation. Toxic by all routes (i.e., ingestion, inhalation, and skin contact) | TLV = 0.5 ppm (2.9 mg/m3) |
2-Methylnaphthalene | 7.4 | Irritating to skin | TLV = 0.5 ppm (2.9 mg/m3) |
Phenanthrene | 36 - 1570 | A known irritant, photosensitizing skin to light. Potential occupational carcinogen | TWA = 0.028 ppm (0.2 mg/m3) |
Compound | Type | % in typical diesel low S fuel | % in gasoline |
---|---|---|---|
n-Nonane | AH | 0.84 | 0.24 |
n-Decane | AH | 0.92 | 0.19 |
n-Undecane | AH | 0.93 | 0.15 |
n-Dodecane | AH | 1.01 | 0.11 |
n-Tridecane | AH | 1.61 | 0.09 |
n-Tetradecane | AH | 1.21 | 0.03 |
n-Pentadecane | AH | 1.09 | 0.01 |
Total studied AH | AH | 7.61 | 0.82 |
Naphthalene | PAH | 0.36 | 0.30 |
The apparatus set up for the sampling is described in
The sampling method applied was EPA TO-17 using 90 mm length, 5 mm diameter stainless steel TENAX adsorption tubes filled with appropriate sorbent materials, prepared and supplied by the DRI (Desert Research Institute at Reno, Nevada, USA). The chemical analysis of the studied VOCs was also done at the DRI, using the Agilent Thermal Desorption-Gas Chromatograph/Mass Spectrometer (TD-GC/MS) system.
The environmental samples were taken in a measurement campaign conducted in three sites, two of them with heavy traffic, the other one with low or inexistent traffic, from July to August 2011, with sampling periods of 24 hours. Each zone was evaluated during a week.
Additional samples were taken in the discharge of a diesel motor working under standardized laboratory conditions with diesel fuel of variable sulfur content. Run cycles followed standard ECE-M2 at 2420 rpm.
The VOC measurement campaign was conducted in three sites, two of them with heavy traffic (Poblado zone and Botanical Garden Park), the other one with low or inexistent traffic (Arví Park), from July to August 2010, with sampling periods of 24 hours. Each zone was evaluated during a week. Another sample was taken sampling during 24 hours continuously within a vehicle moving through designed zones in the city (On Board test). In the
Compound | Poblado 05/08/10 | Poblado 07/08/10 | Poblado 10/08/10 | Botanic Garden 20/08/10 | Arvi Park 31/08/10 | On-Board 02/09/10 |
---|---|---|---|---|---|---|
Type of zone | urban | urban | urban | urban | rural | urban |
n-Nonane | 0.870 | 0.736 | 0.769 | 1.896 | 0.060 | 1.919 |
n-Decane | 0.980 | 0.696 | 0.693 | 2.273 | 0.046 | 1.986 |
n-Undecane | 0.668 | 0.473 | 0.467 | 1.417 | 0.038 | 1.728 |
n-Dodecane | 0.389 | 0.301 | 0.324 | 0.685 | 0.025 | 0.564 |
n-Tridecane | 0.274 | 0.237 | 0.237 | 0.516 | 0.031 | 0.730 |
n-Tetradecane | 0.244 | 0.218 | 0.225 | 0.583 | 0.027 | 1.588 |
n-Pentadecane | 0.241 | 0.190 | 0.207 | 0.986 | 0.057 | 6.379 |
Naphthalene | 0.989 | 0.839 | 0.836 | 2.269 | 0.139 | 0.637 |
1-Methylnaphthalene | 0.212 | 0.179 | 0.200 | 0.741 | 0.010 | 0.322 |
2-Methylnaphthalene | 0.428 | 0.357 | 0.407 | 1.520 | 0.016 | 0.576 |
Phenanthrene | 0.038 | 0.023 | 0.022 | 0.141 | 0.005 | 1.279 |
1-Metylphenanthrene | 0.000 | 0.000 | 0.000 | 0.158 | 0.000 | 0.426 |
2-Methylanthracene | 0.000 | 0.000 | 0.000 | 0.182 | 0.000 | 0.523 |
Total studied VOC | 5.334 | 4.248 | 4.388 | 13.369 | 0.456 | 18.657 |
Total studied AH | 3.666 | 2.851 | 2.922 | 8.357 | 0.286 | 14.894 |
Total estudied PAH | 1.667 | 1.398 | 1.466 | 5.012 | 0.170 | 3.763 |
thalene. The on-board sample shows higher VOC’s concentrations than the other sampling sites. Probably because the on board test environment was in continuous contact with mobile sources.
It is clear in
Following results reported elsewhere [
This analysis shows, in general, local values lower than the typical ones reported around the world. The typical values shown were chosen by the authors after elimination, at their own criteria, of extreme high values in the reported data.
Concentrations in urban areas (μg/m3) | Concentrations in rural areas (μg/m3) | |||||
---|---|---|---|---|---|---|
Compound | Range around the world | Typical around the world | Average of this study | Range around the world | Typical around the world | Average of this study |
n-Nonane | 0.07 - 467 | 5.06 | 1.24 | 0.0 - 58.2 | 4.067 | 0.060 |
n-Decane | 0.16 - 1100 | 18.68 | 1.33 | 0.0 - 161.2 | 5.919 | 0.046 |
n-Undecane | 0.15- 59 | 7.66 | 0.95 | 0.018 - 0.54 | 0.279 | 0.038 |
n-Dodecane | 0.0 -160 | 0.97 | 0.45 | 0.0 - 0.25 | 0.044 | 0.025 |
n-Tridecane | 0.18-2.7 | 0.93 | 0.40 | 0.01-0.12 | 0.066 | 0.031 |
n-Tetradecane | 0.0 - 36 | 8.46 | 0.57 | 0.0 - 0.116 | 0.058 | 0.027 |
n-Pentadecane | 0.19 - 158 | 15.47 | 1.60 | 0.01 -0.149 | 0.080 | 0.057 |
Naphthalene | 0.0 - 77 | 2.27 | 1.11 | - | - | 0.139 |
1-Methylnaphthalene | 0.00 - 5.1 | 0.59 | 0.33 | - | - | 0.010 |
2-Methylnaphthalene | 0.00 - 1.1 | 0.39 | 0.66 | - | - | 0.016 |
Phenanthrene | 0.01 - 129 | 1.08 | 0.30 | 0.0 -0.032 | 0.006 | 0.005 |
Total | 61.58 | 8.94 | 10.52 | 0.456 |
At the time of the study, S content of diesel fuel used in the region was undergoing changes, from 2000 ppm to 50 ppm and it was desired to correlate those changes with VOCs concentrations in the exhaust gases coming from a diesel motor working under standardized laboratory conditions.
The region atmosphere shows presence of VOCs.
The concentrations in urban areas are clearly greater than the ones in rural area. In the average urban total VOCs are 27 times larger.
The values found in rural and urban areas tend to be smaller than the typical values reported, around the world, in the literature. Total VOCs show values around 15% of the reported typical values for urban areas and about 5% for rural areas.
The VOC concentrations are related to vehicle emissions, especially to diesel fuel vehicle emissions.
An initial baseline has been established which should be useful for future work and public policy in relationship to vehicle related pollution control.
Reducing S content on diesel fuel has been a beneficial step in this direction.
Compound | Fuel with sulfur at 50 ppm, µg/m3 | Fuel with sulfur at 500 ppm, µg/m3 | Fuel with sulfur at 2100 ppm, µg/m3 |
---|---|---|---|
n-Nonane | 177 | 62 | 160 |
n-Decane | 407 | 153 | 528 |
n-Undecane | 254 | 203 | 501 |
n-Dodecane | 199 | 250 | 649 |
n-Tridecane | 186 | 311 | 586 |
n-Tetradecane | 111 | 311 | 450 |
n-Pentadecane | 61 | 361 | 356 |
Naphthalene | 179 | 140 | 141 |
1-Metylnaphthalene | 87 | 134 | 176 |
2-Metylnaphthalene | 170 | 218 | 317 |
Phenanthrene | 1.43 | 12.83 | 5.60 |
Total studied VOC | 1832 | 2155 | 3869 |
Total studied AH | 1395 | 1650 | 3230 |
Total estudied PAH | 437 | 505 | 639 |
This work was supported by POLITÉCNICO COLOMBIANO JAIME ISAZA CADAVID and ECOPETROL. We acknowledge the DRI Institute for the analytical and sampling assistance and the University of Antioquia, GIMEL group, for the work done in the laboratory motor testing.
Posada, E., Gómez, M. and Monsalve, V. (2016) Assessment of Organic Compounds as Vehicular Emission Tracers in the Aburrá Valley Region of Colombia. Journal of Environmental Protection, 7, 1561-1570. http://dx.doi.org/10.4236/jep.2016.711129