Fluorescence excitation-emission spectroscopy with regional integration analysis for assessment of compost maturity.

Composting of animal manures is believed as an alternative way for directly recycling them in farms, and therefore assessment of compost maturity is crucial for achieving high quality compost. Fluorescence excitation-emission matrices (EEMs) combined with regional integration analysis is presented to assess compost maturity. The results showed that the EEM contours of water-extract organic matter (WEOM) from immature composts exhibited four peaks at excitation/emission (Ex/Em) of 220/340nm, 280/340nm, 220/410nm, and 330/410nm, whereas EEM contour of WEOM from mature composts had only two peaks at Ex/Em of 230/420nm and 330/420nm. Pearson correlation demonstrated that peaks intensity rather than their ratios had a significantly correlation with the common indices assessing compost maturity, whereas the normalized excitation-emission area volumes (Φ(i,n)s) from regional integration analysis had a stronger correlation with the common indices assessing compost maturity than peaks intensity. It is concluded that the Φ(i,n)s from regional integration analysis are more suitable to assess the maturity of compost than the intensities of peaks. Therefore, the fluorescence spectroscopy combined with regional integration analysis can be used as a valuable industrial and research tool for assessing compost maturity, given its high sensitivity and selectivity.

PARAFAC modeling of fluorescence excitation-emission spectra for rapid assessment of compost maturity.

Assessment of compost maturity is crucial for achieving high quality compost in order to guarantee its marketability. In this context, a novel technique that combines fluorescence excitation-emission matrices (EEMs) with parallel factor (PARAFAC) analysis to assess compost maturity is presented. A total of 60 fluorescence EEMs of composts were successfully decomposed into a three-factor model using PARAFAC analysis. Components 1 [excitation/emission (Ex/Em) wavelengths=(230, 330)/410] and 2 [Ex/Em wavelengths=(250, 350)/450] were attributable to humic-like and fulvic-like substances, whereas component 3 [Ex/Em wavelengths=(220, 280)/340] belonged to protein-like substances. Pearson correlation analysis between the common maturity indices and log scores of three components demonstrated that components 1 and 3 are more suitable to assess compost maturity than component 2. These results reveal that EEM-PARAFAC could be applied as a valuable tool for assessing compost maturity, given its high sensitivity and selectivity.