1. Quiz Solution 1 ug/L benzene = ? ppbv For gases, RT = 24 liters/mole at 20C How to go from volume to mass? Ug/L = mass/volume ppbv = volume/volume PV=nRT so V= nRT/P n = 1/MW For benzene, MW=78 325ppbv V = (1/MW)*RT = 24/78 = 0.325 ppmv *1000 = 325 ppbv

2. Solution to Consultant’s Report SG screening level (from table) = 36.2 ug/m3 0.005 ppmv = 5 ppbv * (78/24.0) = 16 ug/m3 SS screening level = 0.084/0.05 = 1.68 ug/m3 Lab report level (MDL): Lab report level > SS screening level, hence consultant conclusion incorrect SG screening level (from att factor) = 0.084/0.002 = 42 ug/m3

3. Solution - GW Data Exercise TCE in soil gas ~= 50 µg/L x 0.5 = 25 ug/L = 25,000 ug/m 3 TCE in indoor air ~= 25,000 ug/m 3 x 0.001 = 25 ug/m 3 Residential Setting, allowed C indoor = 2.1 µg/m 3 Does TCE exceed allowable value? YES, by over 10xx Is vapor intrusion likely occurring? Possible. Why? Predicted value likely overestimated but must test to be sure

4. Solution - Soil Gas Data Exercise Benzene indoor air ~= 6 µg/L x 0.002 = 0.012 ug/L = 12 ug/m 3 Commercial Receptor, allowed C indoor = 15 µg/m 3 Does the benzene value exceed allowable value? No Is vapor intrusion likely occurring? Probably not Why? Predicted value likely to be lower than 12 ug/m3 due to non-equilibrium & bioattenuation

5. Solution – Sub-Slab SG Exercise PCE indoor air = 2 µg/L x 0.03 = 0.06 ug/L = 60 ug/m 3 Dry cleaner, allowed C indoor = 46 µg/m 3 Does the PCE value exceed allowable value? YES What other data might you collect to see if VI is an issue? Radon to determine slab att factor or Building ventilation rate