EVALUATION OF SOIL ORGANIC-MATTER POLARITY BY PYRENE FLUORESCENCE-SPECTRUM VARIATIONS

Differences in polarity of soil organic matter can explain the variati on of K-oc for hydrophobic organic contaminant. A fluorescence spectru m investigation method has been developed for organic matter character ization which does not require harsh extraction. On the basis of the c hanges of the pyrene fluorescence spectrum related to the polarity of the solvents, the technique has been applied to heterogeneous samples: aqueous soil suspension and activated sludge. Pyrene sorption in orga nic particles leads to a modification in the observed ratio of the int ensity of the first (I-1) and the third (I-3) peaks of its fluorescenc e spectrum (R-obs = I-1/I-3) The polarity estimation of the systems te sted is expressed by the R-p value (derived from R-obs), which is the calculated I-1/I-3 ratio of the organic matter. This value appears to be negatively correlated to the pyrene K-oc value which varies from 24 x 10(3) to 109 x 10(3) L kg(-1). These results suggest that the R-p v alues could be used to correct the K-oc for non ionic hydrophobic orga nic compounds in soils. The practical uses of this methods are (i) the correction of K-oc values calculated from literature based on their K -ow or solubility values and (ii) the prediction of K-oc for different sorbents and non polar organic compounds.