2. The following information applies: Acute criterion: X(ug/L) = exp[MA(In(Hardness)) + bA] Chronic criterion: X(ug/L) = exp[Mc(ln(Hardness)) + bc] \mathbf{K}_{\mathbf{q}} \text { of } \mathbf{C d}\left(\mathbf{O H}_{\mathbf{z}}=5.33 \times 10^{-15} ;

\mathbf{M W}\right. \text { of cadmium }=112.4 \mathrm{~g} / \mathrm{mol} Downstream of the metal plating facility lagoon holding wastewater and sludges, surface water monitoring indicate 4-day and 1-hour average cadmium concentration of 6.8 and 14.2 ug/L, respectively. An average water hardness value of 125 mg/L as CaCO3 was also measured. Determine the cadmium criterion (ug/L) for long-term ecological protection of aquatic life (PE sample exam question).