Pearson correlation coefficiency (<i>R</i>) between properties (pH, EC) and functional groups derived from solid state ¹³C NMR spectroscopy.^a

aNote: *p<0.05; **p<0.01; EC, electrical conductivity; NA, not available.注： *p<0.05； **p<0.01；EC：电导率（electrical conductivity）；NA：不可用（not available）。