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S21 Kam.m.ez'bauer H, H Selinger, R Rommelt, A ZieglerJons, D Knoppik, BfioCk. 1987, Toxic coraponents of 

motor vehicle exaissions for the spruce Pcic;a abies. 

Environ. pollut. 48:235-243. 

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Environmen.tal Pollution 48 (1987) 235-243 

Toxic Components of Motor Vehicle Emissions for the 

Spruce Picea ables 

H. Kaln7nerbauer,° H. Selinger, b R. R6inmelt,° 

A. Ziegler-Jons, b D. Knoppik' & B. Hocka* 

°Department of Botany, 6 Department of Physics, Technical University of Munich, 

D-8050 Freising 12, Federal Republic of Germany 

(Received 17 February 1987; accepted 15 June 1987) 

ABSTRACT 

Six-year-old Nortivay spruce trees were exposed for 30 nzin under standardised conditions to the exhaust fi•om an Otto engine running on leadfree petrol. Gas-exchange measurements in an open system using an infr-ar•ed 

gas analyser showed a sudden, sevel•e drop in COzassimilation. an.d 

transpiration rates. By using filters which absor-bed differen tfi -actions of the 

exhaust it could be dernonstrated that the toxic effects can be attr- ibuted to the 

NO Xfraction. 

INTRODUCTION 

The toxic effects of motor vehicle emissions on Norway spruce Picea abies 

have been investigated by Kammerbauer et al. (1986). For this purpose, a 

standard set-up with a five-cylinder Otto engine running on lead-free petrol 

was used. It produced emission loads which occur at speeds of c. 120 km h -1 

in the fifth gear. A sudden drop in photosynthetic capacity and an 

impairment of stomatal regulation in spruce was observed after a 

fumigation of only 15 min, followed by changes in colour and, finally, by 

needle dropping. The visible symptoms at the shoot depended upon the 

developmental stage of the trees. If fumigation was performed in the spring, 

before sprouting, or even during early stages of sprouting, the buds were not 

* To whom all correspondence should be addressed. 

235 
236 H. Kammerbauer, H. Selinger, R. Romnlelt, A. Ziegler-Jons, D. Knoppilc, B. Hock 

visibly impaired and continued to develop normally. The twigs which grew 

were green with brown inner needles. Treatment, later in the season, 

however, led to a browning of the young shoots. No such symptoms were 

observed when a catalytic converter was added, which reduced NO c , 

hydrocarbons and CO to a tenth of the original concentrations. It was 

speculated that the toxic effects could be attributed to the NO Yfraction. By 

using filters which absorb various fractions of exhaust we can show that it is 

most likely the NO Yfraction which is acutely toxic to Norway spruce. 

MATERIALS AND METHODS 

The experimental arrangement for fiimigation has been described in detail 

; elsewhere (Kammerbauer et al., 1986). Essentially, a five-cylinder Otto 

engine was run on lead-free petrol under the load of an eddy-current brake 

to simulate conditions which occur at speeds of c. 120 km h -1 . The emissions 

; were cooled to room temperature, passed through filters (cf. below) and 

; finally piped into the exposure chamber with the trees (6-year-old clones of 

No. 814, Provenienz 84019 of the Bayerische Landesanstalt fi.ir Forstliche 

' Saat- und Pflanzenzucht, Teisendorf), where gas samples were also taken for I . NO.,, hydrocarbon and CO analyses. The gas exchange was measured in an 

open system using an infrared gas analyser one day before and 3 h after 

I fumigation, as described elsewhere (Kammerbauer et al., 1986). The gas 

; exchange parameters V ~m~Xand JmaX were calculated as described by Selinger 

i et al. (1987). 

! Filters were used to reduce the hydrocarbon and NO x concentrations 

(Table 1) and were mounted between the cooling site and the flow meter. 

; Figure 1 shows the construction of the hydrocarbon filter. The charcoal 

,. 

i collar was made of two nesting cylinders of perforated galvanized metal 

sheets which were joined at the bottom by a plate to form a stable unit. The 

space between the two cylinders was filled with active charcoal (Fa. Camfil, 

i D-2067 Reinfeld) and packed down with a vibrator. The collar was mounted 

TABLE 1 

Reduction of Exhaust Emissions by the Use of Filter Devices 

Filter• type NO., Hyclrocarbons CO 

(Pprll) (ppnn) (vol. %) 

Activated chai-coal filter 650 120 2•2 

Chemisorbant filter 50 170 1•0 

Control (without filter) 650 230 2•0 

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Toxic conzponents of motor vehicle emissions for Picea abies 237 

inlet 

activated charcoal 

perforated sheet metal cylinder 

—• outlet 

outer wall 

Fig. 1. Activated charcoal filter (longitudinal section) for adsorbing hydrocat -bons from 

exhaust emissions. 

outlet 

prefilter 

Fflg. 2. Chemisorbant f lter-for oxidising NOxin exhaust emissions. 
238 H. Kammerbauer, H. Selinger, R. Rommelt, A. Ziegler-J6tis, D. Knoppik, B. Hock 

inside a plastic cylinder with an inlet for the exhaust and an outlet for the 

filtered gases. 

The NOxconcentrations were reduced with a chemisorbant filter (ATEXLabor-Aircleaner, type LAC 3 s, ATEX-Filter Co., D-5830 Schwelm). It 

consisted of the following parts (Fig. 2): one Macrofalt M 45-2-36 prefilter, 

two chelnisorbant filters with PM-12-DP modules and one Macrofalt M 45- 

2-36 after-filter. The filter modules were tightly packed with PurafilChemisorbant II medium (Purafil Inc., Atlanta, USA), which consisted of 

activated aluminium oxide impregnated with 4% (w/v) potassium 

permanganate. During the oxidation of NO xto nitrate, the permanganate 

was reduced to MnO z . The optimal reactions were obtained at temperatures 

up to 40°C, a relative humidity between 15 and 95% and a holding time of at 

least 0•2 s. Particulate components were removed froin the exhaust by the 

cellulose prefilter. 

RESULTS 

Trees were exposed to inotor emissions before sprouting (April 1986) for 

30 min in the presence and absence of filters reducing different fractions of 

the emissions. Figure 3 shows representative measurements for the CO Z 

assimilation and transpiration rates obtained from single plants. The results 

of calculations for several gas exchange parameters, derived from four 

independent measurements, are given as percentage changes in Table 2. The 

controls were kept under the same conditions as the fumigated plants, but 

not exposed to the exhaust gases. No significant changes in the transpiration 

rate could be noted over the observation period (Table 2, Fig. 3a,b). 

However, when the trees were exposed to unfiltered exhaust einissions, a 

sudden and dramatic reduction in the CO Zassimilation (A350, A,,,

~tX) and 

transpiration (T350) rates was observed (Table 2). The changes were in the 

same range as those seen in earlier experiments (Kammerbauer et al., 1986), 

even though a different clone of Norway spruce was used and the 

fumigations were carried out at an earlier point in the season. This also holds 

true for the parameters which were computed from the CO 2response curve, 

V': ,,,.,v which depends upon the ribulose bisphosphate carboxylase (RuBP 

caroxylase) activity, and J ~,,.,X , which is limited by the rate of photosynthetic 

electron transport. 

Similar dramatic changes were. observed when the fumigation was 

performed in the presence of an activated charcoal filter, which reduced the 

proportion oChydrocarbons to 52% by adsorption, but left the NO,. and CO 

concentrations essentially unchanged (Table 1). The decrease in the 

transpiration rate, the rise in the compensation point, and the loss of 
~ 

Toxic components oJ'inotor uehicle emissiazs for Picea abies 239 

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Intercellular CO2 partial pressure (μbar) 

Fig. 3. Rate of CO, assimilation, A(a, c; e) and rate of transpiration, T(b,d,f) versus 

intercellular CO, partial pressure measured 1 day before treatment (- -Q- -Q-) and 3 h after 

treatment (—G—tm'—). a,b, Control; c,d, tunligation in the presence of a chenzisorbant filter; 

e,f, fumigation in the presence of an activated charcoal filter. Arrows indicate net 

photosynthesis rates under normal atmospheric conditions (330 hbar CO,). 

stomatal regulatory ability should be noticed, although no visible symptoms 

could be observed in this clone, in contrast to earlier experiments with other, 

more sensitive clones. Nevertheless, even here there was practically no 

recovery with respect to photosynthesis and transpiration when single trees 

were measured again o'iae month later. 

Wheirn the proportion of NO Ywas reduced to 8% by means of a 

chemisorbant filter, no major differences from the controls (without 

fuznigation) could be observed. The photosynthetic and transpirational 
240 H. Karntnerbattet•, H. Selinger, R. Rommelt, A. Ziegler-J6ns, D. Knoppik, B. Hock 

TABLE 2 

Effect of Fumigation in the Presence and Absence of Filters on the Gas Exchange of Norway 

Spruce (% Change compared to the values before fumigation.) 

I Coiztrol Funiigation Fcunigation in the 

vvithout fzlter presettce of an 

(%) activated 

charconl flter 

(%) 

Fumigation iii the 

preserice of a 

c1leinisorbant 

filter 

(%) 

Measured parameters 

A350 —0+5 —100+7 —87±5 4+1 

Amax +4±3 —68±8 —70±11 4-I-2 

T350 —0±11 —87±15 —73±3 4±2 

I' —9+3 +255+55 +670±260 5±2 

gn (200)/ga (> 2000) —13 ± 6 — 66 ± 18 — 50 ± 6 23 ± 5 

Calculated parameters 

V°m°x 4+6 —86+21 —75±14 5±2 

Jm°x 6-I- 5 — 66 ± 10 — 61 -I- 13 3-I- 4 

The data were obtained from four independent experiments and are given as ineans + standard errors. 

A350+ Am°x; net; CO,,assimilation rate at ambient CO, partial pressure (350 Febar) and at saturating CO, 

partial pressure (>2000 μbar), respectively. T350: transpiration rate at ambient CO Z partial pressure 

(350μbar); I': CO, compensation point: ga (200), g;, (>2000): stomatal conductance at 200μbar and at 

>2000μbar CO, partial pressure, respectively; g; (200)/g; (>2000): stomatal regulatory ability. V°m°x: 

maximal carboxylation capacity; J, n;,x : maximal ribulose bisphosphate regeneration capacity. 

parameters remained essentially unchanged. Only the stomatal regulatory 

ability was increased by this treatment. Although the hydrocarbon and CO 

concentrations were also reduced to 74% and 50%, respectively, by this 

procedure, there are compelling reasons for attributing the absence of toxic 

effects to the reduction of NOx . This was suspected as soon as a motor 

adjustment which reduced NO X concentrations (90 ppm (- μl litre -1 )), but 

left high concentrations of hydrocarbons (250ppm) and CO (1•5vol.%), 

produced less toxic effects than when NO x concentrations relnained high 

(Kammerbauer et al., 1986). On the other hand, the CO concentration r.anges 

applied in our experiments do not have lasting toxic effects on plants. It is 

taken up, oxidised in darkness to CO 2and released, whereas in the light, it is 

incorporated into serine glycine and subsequently into sucrose (Bidwell & 

Bebee, 1974). These authors observed a recovery time of 60 to 90 min in air, 

after a 15 to 20 min exposure to 99 % CO for a variety of plants. 

DISCUSSION 

Decreasing individual components in motor emissions made it evident that 

the NO„ fraction was responsible for the bulk of the toxic effects on Norway 

spruce. Nitrogen oxides arise during the high-temperature combustion 
Toxic cornponents of rnotor oehicle emissions for Picea abies 241 

processes, for the 7nost part as a result of the combination of atmospheric 

Y I oxygen and nitrogen. This process produces mainly NO, which is then 

; oxidised at decreasing temperatures to NO 2 . The latter accounted for 

20-40% of the total nitrogen oxides under our experimental conditions in 

the exposition chambers. Nitric oxide and NO 2react at high partial 

pressures with water to form nitrite and nitrate according to the equations 

NO + NO2"—'O) 2 HONO 

2 NO2'"— ' 0 ,-HONO +'H3 0 + + NO3 

(cf. Finlayson-Pitts & Pitts, 1986). 

The rate drops rapidly as the concentrations approach ambient levels. 

; However, surface-catalyzed reactions, such as those occurring in plants, can 

increase the rates. 

The importance of NO xas a pollutant has often been overlooked (cf. Bell, 

1986). Although toxicological studies were usually performed in combin- 

- ation with other pollutants, such asSO Zor 03 , investigations dealing 

z exclusively with NO, in plants were carried out as early as 20 years ago 

(Taylor & Eaton, 1966). 

t Small doses usually stimulate growth, because NO 2is then used as a 

nitrogen source. The resulting nitrite activates leaf nitrite reductase, which 

detoxifies the compound by reducing it to ammoniuin. This in turn is 

~ incorporated into amino acids (Rogers & Campbell, 1979; Yoneyama & 

~ Sasakawa,1979; Wellburn et a1.,1980). Whereas loads of 62 ppb (- nl litre -1) 

; caused an increase in shoot dry weight in some broad-leaf trees (21-week 

exposure in Tilia cordata, 60-week exposure in Alnus incana; Freer-Smith, 

1984), the conifer Pinus sylvestris exhibited a decrease in relative growth 

t ; rate after an 86-week exposure with the same concentration (Freer-Smith, 

1985, cited in Bell, 1986). The ftimigation of 2-year-old Pinus strobus with 

1 ; 0 1 ppm NO2for 4 h day -1 , over a period of 35 days, diminished the dry 

; ' matter of needles and produced necrotic changes, whereas no symptoms 

; were observed below 0•05 ppm (Yang et al., 1982). In most plants, how- 

; ever, the threshold to chronic injuries is estimated to be c. 0•17 ppm 

(Lichtenthaler, 1984). Above 3-4 ppm NO Z , the range of acute toxicity is 

~ reached (Kato et al., 1974; Yoneyama et al., 1979). 

Injury by NOxis not restricted to a single biochemical reaction. The 

impairment of the net assimilation rate is assumed to originate, in part, in its 

action as an acid gas, which destroys the proton gradient across the 

thylacoid tneinbranes in the chloroplasts (Lichtenthaler & Buschmaml, 

1984). Ultrastructural studies by Wellburn et al. (1972) demonstrated the 

swelling of thylacoids by NO 2 , indicating a disturbance of the ionic balance 

and ATP synthesis. As a radical, NOzinitiates lipid peroxidation and 

i therefore leads to membrane destruction (Heath, 1980; Elstner, 1984). 

i 
242 H. KammerGaater, H. Selinger, R. Ronzmelt, A. Ziegler-Jons, D. Knoppik, B. Hock 

The closure of stomata in response to motor emissions causes a decrease 

in transpiration and CO 2uptake. This is most likely due to NO2 . A similar 

effect was recognised back in the 1950s by Koritz & Went (1953) as a 

response to the oxidative components of smog. Consequently, it is also 

characteristic of the action of ozone (cf. summary by Dugger & Ting, 1970) 

and S02(Majernik & Mansfield,1972). Stomatal closure, which is due to the 

loss of turgor pressure in the guard cells, is interpreted as the consequence of 

an impairment of inembrane functions causing the leaching of ions across 

the plasmalemma. 

Our experiments with motor emissions and individual fractions were in 

the range of acute toxicity. Of course, it is not possible to extrapolate from 

these data to the influence of ambient concentrations on plants. Besides the 

lower concentrations, the cumulative effects of other pollutants, which often 

work synergistically (cf. Landolt & Keller, 1985), inust be considered. The 

formation of secondary air polh.itants in the presence of ozone and light 

must also be taken into account, since these lead to the production of yet 

other strong oxidants (Fuhrer, 1985). Therefore, special attention should be 

given to ways of reversing the present rise in NO xemissions. 

ACKNOWLEDGEMENTS 

This work was supported by a grant from the Bayerisches Staatsministerium 

fiir Unterricht und Kultus to Professor Hock. The fumigation experiments 

were carried out at the Institute fur Verbrennungsmaschinen of the 

Technical University of Munich. We are indebted to Dr K. Zeilinger and 

Dipl.-Ing. H. J. Riedl for their technical help with the experiments. 

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