884 
2 - MATERIALS AND METHODS 
2.1. The apparatus 
The ENEA lidar fluorosensor [2] is based on an excimer laser source exciting the fluorescence of chlorophyll 
pigments contained in the chloroplasts of terrestrial plants as well as algae. The emitted fluorescence is optically 
collected by a Newtonian telescope and analyzed both in spectral and time domains by means of an Optical 
Multichannels Analyzer (OMA HI EG&G) and a Streak Camera (C2830 Hamamatsu), respectively. 
The laser source is emitting @ 308 nm with a maximum prr of 200 Hz, and a low divergence (0.4 
mrad) beam. Each laser pulse has a duration af 16 ns (HWFM) and an energy of 100 mJ. The choice of the 
excitation wavelength (wl) is the result of a trade-off among different requirements, such as a high chlorophyll 
excitation efficiency, high power pulse, robustness, reliability of the laser source and eye-safe wl operatioa 
The use of a Raman cell, filled with CH4 and optically pumped by the excimer laser, allows to 
obtain additional exciting laser lines for exploring the excitation efficiency vs wL However, frequency shifting 
towards the visibile region has resulted in a bit more complex experimental arrangement, due to the eye-safe 
operation requirements. 
In the laboratory, the sample under test was placed at a distance of about 15 m from the receiving 
telescope and irradiated top-down by steering both the transmitter and the receiver lines of sight The laser spot 
at this distance was about 20 cm 2 and a complete covering of the target has been accomplished by slowly rotat 
ing the sample (5-10 tums/min). 
2.2. Sample preparation 
All the heibaceus samples of Spinach and Lolium have been sown and grown in pots inside the glasshouse of 
the Dip. Coltivazione e Difesa Specie Legnose, Univ. Pisa, in suitable pots (20*30*5 cm 3 ) under fully con 
trolled conditions. The pots have been placed into ermetically closed perspex boxes (lxlxl m 3 ) allowing for 
immission of the pollutant gas without affecting the environment of the other boxes or of the glasshouse. 
A group of pots in the first box has been exposed for a period of 10 hours to air mixed with 120 
p.p.b. of S0 2 , while a comparable number of pots in a second box has been used as the reference samples group. 
A different group of boxes with pots has been placed under artificial actinic light in a special chamber into the 
glasshouse. In the artificially illuminated chamber the pots of the first box have been exposed to 0 3 for a period 
of 4 hours at concentration levels of 100 ppb, the second box has been exposed twice, and the last unpolluted 
group has been used as reference. 
At the end of the exposure periods, all the polluted plants look like their corresponding reference 
samples making impossible any easy visual screening. The samples have been quickly carried from Pisa to our 
laboratory and analyzed in a few hours. Table I shows the kind of treatment and the exposure times for each 
group. 
TABLE I - Exposition pollutants of various plants groups. 
N. of pots 
Plant 
Pollutant gas 
Time 
[hours] 
Concentration 
[ppb] 
Group 
3 
Spinach 
None 
I 
3 
" 
so 2 
10 
120 
n 
3 
Lolium 
None 
m 
3 
•• 
so 2 
10 
120 
IV 
3 
Spinach 
None 
V 
3 
•• 
°3 
4 
100 
VI 
3 
° 3 
4+4 
100 
vn 
3 
Lolium 
None 
vm 
3 
°3 
4 
100 
IX 
3 
" 
23 
4 + 4 
100 
X