Result 2 · Figure 4
Below pH 6.5, nickel mobilises. Above it, the water stays clean.
Nickel versus pH for the 35 quantified groundwater samples from the production wells of Wasserwerke Breyell (BTB 1–2) and Kaldenkirchen (KTB 4). Above pH 6.5 the samples below the detection limit are omitted; the elevated population lies entirely at pH below 6.9, the great majority at pH below 6.5. In the Breyell wells nickel and iron are uncorrelated, which excludes pyrite oxidation as the source. *