Similarly, the Ni concentrations in Group 3 were relatively high (median: 17 μg/L in Group 3 vs. 0.44 μg/L in Group 2). Each of Groups 1-3 included sampling sites from at least two of three different original datasets (Fig. , Table ), and it was difficult to further interpret the geographic distribution shown in Fig. . However, sampling sites from legacy mine surveys were more frequently included in Group 1, whereas those from the nickel survey were more frequently included in Group 3.