Figure 2

Groundwater chemistry at 23A13, sampled May 23, 2003 (prior to the phosphate injection), (a) Dissolved oxygen (DO) in micromoles per liter (μM), specific conductance (SpC) in microsiemens per centimeter (μS/cm), and concentrations of total dissolved arsenic (AsT), arsenic(III) [As(III)], and arsenic(V), [As(V)] in μM. (b) Phosphorus (P) in μM and pH. Bars show error limits for measured As(V) concentrations. Also shown are locations of the water table at the time of sampling, the injection and breakthrough-curve-sampling ports used for the tracer test, and the uncontaminated (UZ) and suboxic zones (SZ).