Applications of Chemical Kinetics in Environmental Systems - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 409

(iii) Equate the two rate constants and obtain the value of δ if the pH
of the solution is 5.5. What does this δ represent?

6.9 2 A chemical spill near Morganza, Louisiana, occurred at about 1.45 P.M.
on Monday 19, 1994, from a barge on the Mississippi river. The barge was
carrying 2000 gallons of a highly flammable product called naphtha. The
U.S. Coast Guard closed the river traffic for about 4 miles from the spill
to about 22 miles down river, ostensibly so that naphtha could dissipate.
First determine from the literature the major constituents of naphtha. Using
this as the key, perform calculations (considering a pulse input) to check
whether the Coast Guard's decision was appropriate and prudent. Flow
characteristics of the Mississippi river are given in problem 6.5.
6.10 3 Assume a global CO 2 increase in air at the rate of 0.41% per year. The
current P CO 2 is 358 ppmv. Predict what will be the average pHof rainwater
in the year 2050? Is your estimate realistic? Justify your conclusions.
6.11 2 Tropospheric CO is an important pollutant. It has a background mix-
ing ratio of 45:250 ppbv. In the period between 1950 and 1980, it has
been shown that P CO increased at ∼ 1% per year in the northern hemi-
sphere. Recent data (1990-1993) showed a significant decrease in CO in
the atmosphere. Consider the fact that the largest fraction of CO in air is
lost via reaction with the hydroxyl radical: CO + OH •

k OH

−−→ CO 2 + H • .
If the CO emission rate from all sources is considered to be repre-
sented by a single term Σ S i , the rate of change of P CO is given by

(Novelli et al., 1994): d P CO / d t = i S i − k OH P CO , what is the con-
centration of CO at steady state? Utilize the expression to derive the
differential expression d P CO /P CO . Assume that CO is mainly emit-
ted from automobile exhaust. In the mid-1970s, stringent regulations
have reduced the automobile emissions. Hence assume that no change
in CO sources have occurred during 1990-1993. If P CO presently is
120 ppb and the [OH] concentration in the atmosphere has increased
1 ± 0.8% per year, what is the percent change in P CO during the period
1990-1993?
6.12 2 Using the following data establish the contribution to global warming for
each of the following greenhouse gas. Assume a predicted equilibrium
temperature change of 2 ◦ C for a doubling of the partial pressure of each
gas. (a) Calculate the total temperature increase in the year 3000 due to
the combined emissions of all five gases, if the rate of accumulation is
unchecked.

Preindustrial Current Rate of

Atmospheric Accumulation

Concentration 1990 in Air

Compound (1750-1800) Concentration (% per year)

CO 2 280 ppmv 353 ppmv 0.5

CH 4 0.8 ppmv 1.72 ppmv 0.9

N 2 O 288 ppbv 310 ppbv 0.25

CFC-11 0 280 pptv 4

CFC-12 0 484 pptv 4