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April2021 M7VGW--1 pHMemo♦8 <br /> Dissolved iron and manganese concentrations in POC well MNGW-1 have been below their <br /> respective NPLs of 5 mg/L and 0.79 mg/L,respectively. <br /> Dissolved iron concentrations also have been low in MNGW-3 and MNGW-4 (<0.0092 to <br /> 0.385 mg/L) and in NNG-40/NNG-50 (0.0173 to 0.40 mg/L) (Figure 10). <br /> Dissolved manganese concentrations in MNGW-3 and MNGW-4 were above 1 mg/L when <br /> initially sampled in 2014, but both have decreased to generally below 0.5 mg/L (Figure 11). <br /> One exception is the January 2016 sample from MNGW-4,which yielded a concentration of <br /> 0.81 mg/L. Dissolved manganese concentrations in NNG-40 and NNG-50 ranged from 1.2 <br /> to 4.79 mg/L. <br /> Dissolved selenium concentrations in MNGW-1 have been below the NPL of 0.02 mg/L and <br /> have been similarly low in MNGW-3 and MNGW-4 (Table 3). The concentrations in NNG- <br /> 40 and NNG-50 have ranged from <0.00042 to 0.0034 mg/L. <br /> Dissolved zinc concentrations in MNGW-1 have ranged from 0.0072 to 0.055 mg/L,which <br /> are below the NPL of 2 mg/L (Figure 12). Dissolved zinc concentrations in MNGW-3 and <br /> MNGW-4 have ranged from <0.002 to 0.957 mg/L. The concentrations in NNG-40 and <br /> NNG-50 have ranged from 0.391 to 2.02 mg/L. <br /> As shown on Figure 13, sulfate concentrations at NNG-40 and NNG-50 have ranged from <br /> 26.7 to 110 mg/L. Sulfate concentrations in MNGW-1 have varied seasonally, ranging <br /> between 30.9 and 281 mg/L. Sulfate concentrations in MNGW-3 and MNGW-4 have ranged <br /> between 224 and 673 mg/L and 162 and 339 mg/L,respectively. <br />