Figure 4. Principal component analysis (PCA) by integrating all measured parameters (CR, AE, RR, ER, O:N, SFG, E) for four times (days: 1, 3, 7 and 14) and six different treatments (▴–TiO₂ 0 × pH 8.1, △–TiO₂ 0 × pH 7.3, ▪–TiO₂ 2.5 × pH 8.1, ▫–TiO₂2.5 × pH 7.3, ♦–TiO₂10 × pH 8.1, ◊–TiO₂ 10 × pH 7.3) with a biplot.

Both the scores of the experimental conditions and the loadings of the parameters (○) were present.