Figure 5: Scatter plots showing the relationship between measured particle emissions indices (EIs).

Solid lines are orthogonal distance regression (ODR) linear fits to the data, while dashed lines are ordinary least squares (OLS) linear fits. For both fits, the intercept was held at zero. Outlier test points 89 and 229 are noted, which correspond to the two plume intercepts of the GE GEnx engine. Note that kg−1 denotes ‘per kilogram of fuel’.