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Fig. 6. Projection of variables onto the plane defined by the two first principal component multiple factor analysis (MFA). The coordinates of each variable are the correlation coefficients with the two first principal components. The variables are better represented in this plane when arrow points are close to the circle. When they are correctly represented, the correlations between variables are greater when the angle between their direction is smaller. Org, organic; Tot, total; Inorg, inorganic; No/Co, organic N to organic C ratio; Co/No, organic C to organic N ratio; C/N, total C to total N ratio; W20, water-soluble fraction at 20°C; W20–100, water-soluble fraction from 20 to 100°C; W100, water-insoluble fraction at 100°C; SOL, soluble compounds; HEM, hemicellulose-like compounds; CEL, cellulose-like compounds; LIG, lignin-like compounds; AcS, acid-soluble fraction; Dist, distillable; NDist, nondistillable; AcIns, acid-insoluble fraction. An abbreviation preceded by C/N, C, or N refers to the C to N ratio or the part of sludge C or N present in that specific organic fraction, respectively. The number (day) following C or N refers to carbon or nitrogen mineralization at that day.
