Figure 3

The relationship between (a) Cl− and Na+, (b) Cl− and SO42−, (c) Ca2+ and SO42−, and (d) Al and SO42−. The samples in each season are denoted by different colors. Linear regression (black line) is fitted for the whole study period. The Cl−/Na+ mass ratio of seawater34 is represented by the purple dash line for reference in Fig. 3a.