Page 28 - Materials Chemistry, Second Edition

Site Assessment and Remedial Investigation 11

(c) An empty warehouse (200′ × 50′ × 20′) containing 10 ppmV xylenes
in air (T = 20°C; see Equation 2.1)

Solution:
(a) Mass of xylenes in liquid = (liquid volume)(liquid concentration)
= [(1,000,000 gal)(3.785 L/gal)](10 mg/L)
= (3.785 × 10 )(10) = 3.79 × 10 mg
6
7
(b) Mass of xylenes in soil = [(soil volume)(total bulk density)](COC
concentration in soil)
= {[(100 yd )(27 ft /yd )(30.48 cm/ft) ] × [(1.8 g/cm )(kg/1000g)]}
3
3
3
3
3
(10 mg/kg)
= (1.37 × 10 )(10) = 1.37 × 10 mg
5
6
(c) Mass of xylenes in air:
MW of xylenes [C H (CH ) ] = (12)(6) + (1)(4) + [12 + (1)(3)](2) = 106
6
3 2
4
g/mole
At T = 20°C and P = 1 atm
1 ppmV of xylenes = (MW of xylene/24.05) mg/m 3
= (106/24.05) mg/m = 4.407 mg/m 3
3
10 ppmV of xylenes = (10 ppmV)[4.407 (mg/m )/ppmV]
3
= (10)(4.407) = 44.07 mg/m 3
Mass of xylenes in air = (air volume)(vapor concentration)
= [(200 × 50 × 20 ft )(0.3048 m/ft) ](44.07 mg/m )
3
3
3
= (5.66 × 10 )(44.07) = 2.5 × 10 mg
5
3
∴ The liquid contains the largest amount of xylene.
Discussion:
1. To convert a ppmV value to a mass concentration basis, we need
to specify the corresponding temperature and pressure.
2. It should be noted that xylenes have three isomers, i.e., ortho-,
meta-, and para-xylenes (o-, m-, p-xylenes).

Example 2.2: Mass and Concentration Relationship (in SI units)
Which of the following media contains the largest amount of toluene
[C H (CH )]?
3
5
6