TOTAL LUMINESCENCE SPECTROSCOPY OF AQUEOUS PINE LITTER (O-HORIZON) EXTRACTS - ORGANIC-LIGANDS AND THEIR AL OR CU COMPLEXES

Total luminescence spectra are surfaces (in a graphical representation ) generated by plotting fluorescence intensity against both excitation (lambda(ex)) and emission (lambda(em) wavelengths as independent vari ables. Traditional fluorescence spectra can be pictured as single tran sects across a total luminescence spectrum and, accordingly, they prov ide only a single profile of a fixed section through the complete surf ace. Total luminescence spectra in the range, 300<lambda(ex)<400 nm, 4 00<lambda(em)<600 nm, were obtained for solutions containing 25 g C m- 3 prepared from aqueous extracts of ponderosa pine foliage and litter- layer (O horizon) samples. The spectra exhibited three principal featu res: a broad peak at lambda(ex) almost-equal-to 310 nm, lambda(em) alm ost-equal-to 450 nm (gradually shifting to longer wavelengths with inc reasing humification of the sample); a dome at lambda(ex) almost-equal -to 390 nm, lambda(em) almost-equal-to 500 nm whose relative prominenc e decreased with increasing humification of the sample; and a ridge of maxima near lambda(ex) = 360 nm that was unaffected by sample provena nce. Increasing the pH from 4.0 to 5.5 increased the fluorescence inte nsity overall, more so for the dome than the broad peak. Adding Cu to the extract solutions quenched fluorescence uniformly, whereas adding Al enhanced fluorescence overall, again more so for the dome than the broad peak. The relatively uncomplicated structure of the total lumine scence spectra and their response to changes in pH or metal addition s uggested that reactions between the foliage or litter organic ligands and either protons or metals were not highly heterogeneous.