Environ. Sci. Technol. 2000, 34, 2918-2924
Effect of Gasoline and Lubricant on Emissions and Mutagenicity of Particles and Semivolatiles in Chain Saw Exhaust ROGER MAGNUSSON* AND CALLE NILSSON Chemistry and Biomass, Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, P.O. Box 4097, SE-904 03 Umea˚, Sweden KURT ANDERSSON† AND BARBRO ANDERSSON‡ Center for Musculoskeletal Research, National Institute for Working Life, P.O. Box 7654, SE-907 13 Umea˚, Sweden, and Environmental Chemistry, Department of Chemistry, Umea˚ University, SE-901 87 Umea˚, Sweden ULF RANNUG Department of Genetic and Cellular Toxicology, Wallenberg Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden CONNY O ¨ STMAN Department of Analytical Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden
The exhaust from a two-stroke chain saw engine was characterized using two different types of gasoline, aliphatic gasoline and conventional lead-free gasoline, in combination with four lubricants differing in mineral oil, polyolester, and polyisobutylene (PIB) content. This characterization was focused on emissions of polycyclic aromatic hydrocarbons (PAH) and mutagenicity testing using Ames Salmonella assay. In addition, exhaust emissions of carbon monoxide (CO), nitrogen oxides (NOx), aldehydes, and hydrocarbons (HC) were measured. The two-stroke engine was tested in a test bench, and particulate, semivolatile, and gaseous exhaust components were sampled using a dilution tunnel. Much less PAH were emitted when using aliphatic gasoline due to a much lower gasoline content of PAH and aromatics than the conventional gasoline. Also about half the NOx emissions, up to 50% higher formaldehyde and acetaldehyde emissions, and 10% higher total HC emissions were observed for the aliphatic gasoline. The influence of lubricant on the studied exhaust emissions was found to be of minor importance. In terms of mutagenicity, significant effects were seen for six of the eight gasoline/ lubricant combinations, and the highest effects were observed without a metabolizing system. Generally, the conventional gasoline gave higher effects than did the aliphatic gasoline. A difference between lubricants was also seen, especially in combination with gasoline A; however, the interpretation of mutagenic effects of the lubricants was not straightforward. Overall, one synthetic ester-based lubricant and one mineral oil-based lubricant gave the highest mutagenicity.
Introduction Small hand-held utility machines such as chain saws, grass trimmers, and hedge trimmers are often equipped with two2918
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stroke engines due to their high power to weight ratio. However, their high output of unburned fuel due to scavenging losses is in the range of 30% of the fuel consumption. This leads to severe problems for the user, especially when the machines are used professionally. Complaints about irritation of the upper respiratory tract and eyes as well as fatigue and headache are common problems (1, 2). In an earlier study, we primarily addressed the problems with acute effects and recommended a new type of gasoline for use in hand-held utility machines (3). This gasoline consisted of only aliphatic saturated hydrocarbons (HC) as compared to conventional Swedish gasoline, which contains 30-50% aromatics and 2-15% olefins. On the basis of that study, a Swedish standard was adopted for this gasoline in 1995 (4). The fuel for simple two-stroke engines such as these contains 1-2% of lubricant. The traditional mineral oil used is now partly or totally replaced by various synthetic base stocks such as polyisobutylene and esters of various types, and for some applications, vegetable oils are used. Apart from the base stocks, additives are also used to improve temperature stability, pressure stability, and chemical stability of the lubricating oil. During ideal combustion in air, only carbon dioxide, nitrogen oxides, and water are formed. During actual combustion, however, a large number of other compounds are formed. One group of compounds formed is polycyclic aromatic hydrocarbons (PAH) that are formed mainly due to incomplete combustion. Many PAH have been identified as carcinogenic to rodents and are classified by the International Agency for Research on Cancer (IARC) as probably or possibly carcinogenic to human beings (5). Studies have shown that PAH in experimentally diluted exhaust gas are both particulate and gas-phase associated (6, 7). Other compounds in the exhaust gas that are also human health risks or environmental pollutants are carbon monoxide (CO), nitrogen oxides (NOx), HC, and aldehydes. It is wellestablished that gasoline engine exhaust contains genotoxic components; the IARC has classified gasoline engine exhaust as possibly carcinogenic to human beings (8). A study of exposure to the exhaust from two-stroke outboard engines shows that the exhaust can cause disruption of normal biological functions of living fish (9). In a review by McGinty and Dent (10) concerning fourstroke engines, it is shown that the gasoline composition influences the emission of PAH and also the emission of other exhaust components. For two-stroke engines, a gasoline composition dependency of PAH emissions (11, 12) and other exhaust components (3, 13, 14) is also observed. The choice and mixing ratio of lubricant might also influence the PAH exhaust emissions. This matter has been studied by both Cosmacini et al. (11) and Laimbo¨ck (12) but with different results. For simple two-stroke engines, the lubricant is added directly to the gasoline, and scavenging losses can give about 30-40% unburned oil in the exhaust gas (12). Furthermore, the lubricant as well as the gasoline may affect the mutagenicity and carcinogenicity of the exhaust. Some types of mineral oils, for example, are carcinogenic to human beings (15). However, for two-stroke engines the influence of gasoline and lubricant on PAH emissions and mutagenicity of the * Corresponding author phone: +46(0)907869495; fax: +46(0)907869404; e-mail:
[email protected]. † National Institute for Working Life, deceased. ‡ Umeå University and National Institute for Working Life. 10.1021/es9912022 CCC: $19.00
2000 American Chemical Society Published on Web 06/16/2000
TABLE 1. Chemical and Physical Properties of the Two Types of Gasoline Used in the Study property
method
gasoline A
gasoline B
octane no. (research) octane no. (motor) density (15 °C), g/mL vapor pressure, kPa distillation initial boiling point, °C 10% recovered, °C 50% recovered, °C 90% recovered, °C final boiling point, °C aromatic content, % v/v benzene, % v/v olefin content, % v/v sulfur content, mg/kg energy content (LHV), MJ/kg sum of 20 PAH,a mg/L
D2699 D2700 ASTM-D4052 A-D5191
95 91.5 0.686 56
95.5 85 0.739 91.5
ASTM-D86 ASTM-D86 ASTM-D86 ASTM-D86 ASTM-D86 SS 155120 SIS 155136 ASTM-1319 A-D5453 SS 155138
40 58 101.5 111 125.5 0.1 0.1 0.1 2.3 44.5 0.13
34 45 95 158 196 34.3 2.05 10.2 17 43.8 99
a
The same PAH compounds as analyzed in the exhaust emissions. For analytical method, see the section Polycyclic Aromatic Hydrocarbons.
exhaust is an area that has been dealt with only to a limited extent. In an earlier publication (16), we studied mainly the reproducibility in mutagenicity and emissions of PAH, CO, NOx, HC, and aldehydes when sampling chain saw exhaust and made a comparison between two fuels. In this study, we have extended the study to comprise eight fuels: conventional gasoline and aliphatic gasoline combined with four different lubricating oils chosen to cover the base stocks on the market. This was done in order to screen for differences in mutagenic effects between the various fuels and to find possible correlation to PAH emissions.
Experimental Section Chain Saw. The chain saw used during all measurements was a new Husqvarna 242 XP (Husqvarna AB, Husqvarna, Sweden) with a displacement of 41.6 cm3 and a maximum power output of 2.4 kW at 9900 rpm. The saw was used in its original configuration with a few exceptions. The guide bar and chain were removed (since the saw was mounted in a test bench), and instead of using the original tank, the fuel was led directly to the carburetor through a glass buret, where the fuel consumption was measured. A stainless steel funnel was mounted at the silencer blow off in order to lead all the exhaust gas into a dilution tunnel. Fuels. Eight different fuels were used, which consisted of two different types of gasoline combined with four different lubricating oils. The two different types of gasoline used were 95 octane aliphatic gasoline (gasoline A) and regular 95 octane lead-free gasoline (gasoline B). The composition of gasoline A was according to a Swedish Standard (4). The chemical and physical properties of the two types of gasoline are given in Table 1. The lubricants used in the tests where chosen to represent different types of base stocks on the market. Oil 1 and oil 2 were different types of ester-based synthetic oils, and oil 1 was claimed to be biodegradable. Oil 3 had a high content of polyisobutylene (PIB), and oil 4 was a traditional mineral oil. The compositions of the lubricants are presented in Table 2. The lubricants were mixed with the gasoline in an amount of 1.7 vol % (lubricant solvent excluded). Exhaust Dilution and Experimental Procedure. The chain saw was mounted on a stationary test bench, equipped with an eddy current dynamometer, during the exhaust sampling and was run applying a constant load at 9000 rpm, giving a power output of 2.1 kW. Since the fuel/air mixing
TABLE 2. Main Components of Lubricating Oils Used in the Study component (%)
oil 1
oil 2
oil 3
oil 4
mineral oil polyolester PIBa additive package solvent
46 ∼24 ∼5 25
30 40 4.4 25
∼25 ∼45 ∼5 ∼25
82 4.8 13
a
Polyisobutylene or polybutene.
ratio has a large effect on emissions (2), the carburetor setting was adjusted so that a constant CO emission of 3.0% was obtained. Before the exhaust sampling was started, the chain saw was run on the test bench for about 1 h in order to achieve stable test conditions. All exhaust sampling was made from diluted exhaust gas. In addition, CO was analyzed from raw exhaust gas. However, all emission data given in this paper show concentrations calculated for raw exhaust gas. The dilution tunnel used consisted of a 4 m long stainless steel tube with an i.d. of 200 mm and was connected to the saw through a flexible tube. A multi-hole probe for the measurement of the CO emission in the raw exhaust gas was positioned at the dilution tunnel exhaust inlet. Three stainless steel probes inside the dilution tunnel were used for isokinetic sampling of particles and semivolatiles. Five more stainless steel probes were used for sampling of aldehydes, HC, CO, and NOx. The whole testing arrangement is described in detail in an earlier publication (16). For each fuel, one sampling run was performed where particles and semivolatiles were sampled in triplicate for 2 h. During this 2-h period, emissions of CO and NOx and temperatures were measured in intervals of 5 min, aldehydes and HC were sampled in duplicate three times, and the fuel consumption was measured three times. Between each sampling run, the dilution tunnel and sampling probes were cleaned with isooctane (Merck, p.a.) to eliminate deposits from previous emission tests. After being cleaned, the tunnel was ventilated with air for at least 2 h. Temperatures, Flow, and Dilution Ratio. Temperatures were measured by thermocouples (chromel/alumel, type K, Pentronic AB, Gunnebo, Sweden) at four points: in the dilution air, at the cylinder of the engine, in the dilution tunnel exhaust inlet, and in the diluted exhaust near the particle sampling probes. The airflow through the dilution tunnel was measured to 0.6 m3/min by a thermo-anemometer (GGA-65, Alnor Oy, Turku, Finland), and the raw exhaust gas flow was calculated to 0.2 m3/min giving a dilution ratio of about 4 (total flow divided by raw exhaust gas flow). The exact dilution ratio for each sampling run was calculated by dividing the CO concentration in the raw exhaust gas by the CO concentration measured in the diluted exhaust gas. Carbon Monoxide and Nitrogen Oxides. The emission of CO was measured by an IR instrument (HC/CO tester model 590, Beckman). The emission of NOx was measured by a chemiluminescence instrument (nitrogen oxides analyzer model 8440E, Monitor Labs, Englewood, CO). Water was separated from the exhaust before measurement by means of a Peltier gas cooler (ECP 1000, M & C Products Analysentechnik GmbH, Ratingen, Germany). Aldehydes. Aldehydes were sampled from diluted exhaust gas using two parallel impingers containing a solution of 2,4-dinitrophenylhydrazine in acetonitrile (Rathburn, HPLC grade) at a flow of approximately 1.0 L/min for 20 min. The aldehyde-2,4-dinitrophenylhydrazones formed were then analyzed by high-performance liquid chromatography (HPLC) using a Hewlett-Packard 1100 series HPLC system. A C18 column (ODS Hypersil 5 µm, 100 × 2.1 mm, Hewlett-Packard) was used eluted with a methanol:water gradient program. VOL. 34, NO. 14, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 3. Temperatures, Fuel Consumption, and Concentration of Gaseous Emissions When Running the Chain Saw with 95 Octane Aliphatic Gasoline (Gasoline A) Using Four Different Lubricating Oilsa parameter
unit
temp dilution air temp engine temp exhaust sampling temp fuel consumption dilution ratio CO NOx isopentane isooctane toluene total HC formaldehyde acetaldehyde
°C °C °C °C mL/min % ppm g/m3 g/m3 g/m3 g/m3 mg/m3 mg/m3
oil 1 19 257 282 83 20.8 4.2 3.1 180 3.9 5.7 ndc 18 270 67
oil 2 (6) (1) (3) (3) (0) (6) (11) (18) (15) (16) (16) (8) (2)
19 281 288 82 20.9 4.2 3.0 230 3.6 4.9 ndc 15 400 69
oil 3 (3) (3) (1) (1) (2) (8) (10) (26) (14) (11) (11) (5) (5)
18 262 291 83 20.7 4.2 3.1 210 4.1 5.4 ndc 17 260 52
nb
oil 4 (4) (0) (0) (1) (1) (4) (6) (10) (18) (12) (12) (9) (5)
18 257 276 79 21.2 4.3 3.1 240 3.8 5.5 ndc 17 320 63
(8) (1) (2) (1) (2) (6) (12) (25) (9) (5) (5) (8) (6)
23 23 23 23 3 23 23 23 6 6 6 6 6 6
a Concentrations are given for raw exhaust gas, and relative standard deviation is given in parentheses. b Number of measurements/samples for each run. c nd, not detected (
