Environmental Engineering Reference
In-Depth Information
can reduce DOM concentrations in surface waters. The consequence might be
an increased exposure of aquatic organisms to both UV-A and UV-B radiation
(Schindler et al.
1996
; Yan et al.
1996
; Morris and Hargreaves
1997
).
7 Scope of the Future Challenges
CDOM is generally produced from two major sources: allochthonous and autoch-
thonous. Absorption coefficients of CDOM have often been determined jointly in
earlier studies. Recent studies show that autochthonous DOM is significantly pro-
duced from photo- and microbial respiration or assimilation of algae or phytoplank-
ton biomass, yielding compounds that are very similar to allochthonous fulvic and
humic acids (Zhang et al.
2009
; Mostofa et al.
2009
; Yamashita and Tanoue
2004
;
Yamashita and Tanoue
2008
; Mostofa et al.
2009
). The specific absorption proper-
ties of allochthonous and autochthonous CDOM could be important to understand
the physical, photoinduced and microbial changes of those two CDOM pools in
natural waters. Remote sensing is widely applied to characterize various parameters
as explained earlier, but a key application could be the detection of algal blooms
in natural waters. The CDOM research for future challenges can be distinguished
as: (i) Investigation on CDOM absorption of allochthothous fulvic and humic acids
compared to autochthonous DOM originated from algae or phytoplankton biomass
in natural waters. (ii) Investigation on the absorption of radiation by various amino
acids or proteins originated from phytoplankton with respect to their standard sub-
stances. (iii) Study of the photoinduced and microbial changes of CDOM absorption
for both allochthonous and autochthonous DOM. (iv) Investigation on the differ-
ences of photoinduced reactivity between allochthonous (fulvic and humic acids)
and autochthonous DOM of algal or phytoplankton origin (termed autochthonous
fulvic acid, see chapter
“
Fluorescent Dissolved Organic Matter in Natural Waters
”).
(v) Application of remote sensing in investigation of algal blooms in natural waters.
Problems
(1) Define the chromophoric dissolved organiu matter (CDOM)?
(2) Define the chromophores in CDOM. Mention the key chromophores in
CDOM found in natural waters.
(3) Explain the CDOM absorbance theorem.
(4) What are the optical variables for the attenuation of UV and photosyntheti-
cally available radiation in waters? Mention the key optical variable and how
it affects the absorption properties of waters.
(5) Explain the effects of suspended particulate matter and chlorophyll on
absorption coefficients in waters.
(6) What are the controlling factors that affect CDOM absorption in waters?
Explain the role of CDOM contents on absorption properties.
