The CR and OFR systems were clearly separated on PC1. The ORF system was located on the positive axis of PC1 with high positive scores; the CR system was located on the negative axis of PC1 with high negative scores. The sample scores of systems reflected the loading score of protein or elements in PCA. In 2013, the high positive sample scores of the ORF system were because of the high positive loading scores: Ba, As, Mo, Ni, P and Cd; and the high negative sample scores of the CR system were due to the high negitive loading scores of Sr, As, B, Al and Cr. Similarly, in 2014, the high positive sample scores of ORF were related to P, Mo, Zn, Fe, Se, and Cd, and the high negative sample scores of CR were related to Cr, Al and Ca.