Fig. 3: Spline and relationship of gaseous elemental mercury (GEM) to carbon monoxide (CO) and the distance of the endpoint of each 48h trajectory from the corresponding cruise observation location (Traj48h).

Spline of gaseous elemental mercury (GEM) to (a) CO and (b) Traj48h (the distance of the endpoint of each 48 h trajectory (hourly resolution) from the corresponding cruise observation location). The y-axis in each subplot represents the smooth function term of each predictor with the estimated degrees of freedom inside the brackets. The gray area around the line is the 95% confidence bound for the response. c Relationship between the fraction of the 168 h backward trajectory’s transport time over land area over the total transport time (Land fraction (Traj)) and its corresponding average GEM concentration. The error bars of x-axis and y-axis indicate the standard deviations of the average Land fraction (Traj) and the corresponding average GEM concentrations, respectively.