Encyclopedia of Environmental Science and Engineering, Volume I and II

ACID RAIN 7

Therefore the pH will most frequently be either very large or

very small, giving a bimodal distribution.

To calculate (HCO 3 ), for charge balance calculations, it

is also useful to note that from equation (8),

HCO

10 Pco

H

3

6

^2

 



()

()

()

0 0153.

(17)

Thus, for Pco 2  316  10 ^6 atm,

HCO

H

3



() 

()

484.

(18)

Therefore, at pH  5, (H^ ^ )  10 m eq L^ ^1 , and (HCO 3 ) is

only about 5% as large as (H^ ^ ).

A = 25°C 158 ppm

B = 25°C 316 ppm

C = 25°C 632 ppm

D = 5°C 316 ppm

TPCO

2

OH

HCO –

• 3
  B

23456789 pH

0.1

• 0.1


• 1.0
  
  
  • 10
  
  
  
  


• 100


• 1000

1.0

10

100

1000

A

B

C

D

B

PCO

2

= 0

with

H+

NET IONS (

m

eq/L)

NET IONS (

m

eq/L)

with PCO

2

= 0

FIGURE 1 The concentration of Net Ions versus pH for precipitation samples with

different values of T (temperature) and PCO 2.

C001_001_r03.indd 7C001_001_r03.indd 7 11/18/2005 10:07:26 AM11/18/2005 10:07:26 AM