in the figure with PSE samples in the negative side of PC2 and DFD samples n the positive side of PC2. The RFN samples are located in between he DFD and PSE clusters. The edge of the PSE and RFN clusters are somewhat overlapped, with some RFN samples mixed in the PSE cluster. These samples, although presenting chemical characteristics of the RFN class, have a spectral signature similar to the PSE category