283 
the base line, were shown to be directly proportional 
to Chi concentrations in the range of 3 to 2 0 mg.m -3 . An 
accuracy of Chi estimation of about 0.5 mg.m -3 was achieved. 
2. Magnitude and position of the peak near 700 nm depend strongly 
on Chi concentration and can be used for quantitative estimation 
of Chi. It was shown that the reflectance ratio R(max)/R(670) and 
the reflectance height, at wavelength corresponding to the peak 
of reflectance, above the base line through 670 to 850 nm, can Be 
sensitive indices for Chi assessment. For Chi ranging from 10 to 
185 mg.m -3 an estimation error < 7 mg.m -3 was obtained. The sum 
of reflectance above the base line and the peak position may be 
also used for remote Chi measurements. 
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