Geoscience Reference
In-Depth Information
Fig. 8.4
Rates of selenium volatilization from soil versus time (Lin et al. 2000 )
( 1983 ) also report that NH 3 volatilization losses are greater from lime-stabilized
sludge with pH = 12 than from aerobic or anaerobic sludge. A linear relationship
between volatilization decrease and temperature decrease also characterizes NH 3
behavior in the sludge-amended lands.
A special case is given by ammonia volatilization from flooded land surfaces,
which involves a more complex pathway. This is because the kinetics and extent of
the volatilization are affected by water quality, type of land, and biological and
environmental factors. In this particular case, the rate of NH 3 volatilization is
mainly a function of ammonia concentration in the flooding water (Jayaweera and
Mikkelsen 1991 ).
Nitrite formation may lead to nitrous oxide (N 2 O) emission. An example of
such a process under reclaimed effluent disposal on the land surface is reported by
Master et al. ( 2004 ). Irrigating a grumosol (\60 % clay content) with fresh and
reclaimed effluent water, it was found that, under effluent irrigation, the amount of
N 2 O emissions was double the amount emitted under freshwater treatment, at
60 % w/w. The N 2 O emission from effluent-treated bulk soil was more than
double the amount formed from large aggregates.
Plant-mediated volatilization of inorganic compounds is an accepted method
for reclaiming selenium-contaminated lands. Volatile Se is formed mostly from
dimethyl selenide, evolving from the land surface. For example, dimethyl selenide
produced more than 90 % of the total volatile Se in the San Joachim Valley,
California (Karlson and Frankenberger 1988 ). Lin et al. ( 2000 ) report on Se vol-
atilization from a Salicornia bigelovii field which occurs as a result of Se meth-
ylation by plants. In their experiment, Lin et al. ( 2000 ) found that biological
volatilization removed 62 mg Se m/yr, which accounted for 6.5 % of the total
annual Se input to the S. bigelovii field. The fluctuation of Se volatilization rates
during a 12-month study period is presented in Fig. 8.4 . Linear regression analysis
Search WWH ::




Custom Search