Dissolved Organic Matter in Natural Waters - Photobiogeochemistry of Organic Matter - page 3

et al. 2010 ; Ballaré et al. 2011 ; Zepp et al. 2011 ). DOM with its degradation prod-
ucts can extensively influence photosynthesis, thereby playing a key role in global
carbon cycle processes (Mostofa et al. 2009a ; Mostofa and Sakugawa 2009 ; Ma
and Green 2004 ; Johannessen et al. 2007 ; Palenik and Morel 1988 ; Fujiwara et
al. 1993 ; Komissarov 1994 , 1995 , 2003 ; Miller and Moran 1997 ; Meriläinen et al.
2001 ; Malkin et al. 2008 ). DOM also plays important roles in regulating drinking
water quality, complexing behavior with metal ions, water photochemistry, biolog-
ical activity, photosyhthesis, and finally global warming.
This chapter will provide an overview on the origin of DOM, its contents and
sources in natural waters, the contribution of organic substances to DOM, the bio-
geochemical functions of DOM, its physical and chemical properties, as well as
its molecular size distribution. It comprehensively discusses the controlling fac-
tors and their effects on the distribution of DOM in natural waters, the emerging
contaminants and their sources, transportation and impacts, as well as methodol-
ogies and techniques for the detection of pharmaceuticals in fish tissue. Finally,
it is discussed how DOM acts as energy source for living organisms and aquatic
ecosystems.
2 What is Dissolved Organic Matter?
DOM is conventionally defined as any organic material that passes through
a given filter (0.1-0.7 μ m). The organic material that is retained on the filter is
termed 'particulate organic matter (POM) (Mostofa et al. 2009a ). The permeate
from ultrafiltration (<10 kiloDaltons or kDa) is often defined as the truly dis-
solved organic carbon fraction and the filter-passing fraction between >10 kDa and
<0.4 or 0.7 μ m as the total dissolved organic carbon fraction in aqueous solution.
Colloids are operationally defined as particles between 1 nm and 1 μ m in size, and
the 'dissolved' fraction can include a subset of the colloidal materials (Sharp 1973 ;
Vold and Vold 1983 ; Koike et al. 1990 ; Benner et al. 1992 ; Buesseler et al. 1996 ;
Wells 2002 ). These types of colloidal particles are not entirely retained by filters
with pore sizes between 0.2 and 0.7 μ m. DOM can be in the size range of tens to
hundreds of nm when they are associated with other colloidal materials in water
(Lead and Wilkinson 2006 ). It has been shown that colloids make up a significant
fraction, approximately 10-40 %, of the marine DOM pool.
DOM in natural waters is composed of a heterogeneous mixture of numerous
allochthonous and autochthonous organic compounds containing low molecu-
lar weight substances (e.g. organic acids) and macromolecules such as fulvic and
humic acids (humic substances), with molecular weight ranging from less than
100 to over 300,000 Daltons (Thurman 1985a , 1986 ; Ma and Ali 2009 ; Rashid
and King 1969 ; MacFarlane 1978 ; Hayase and Tsubota 1983 ; Amy et al. 1987 ;
Wagoner et al. 1997 ; Jerry and Jean-Philippe 2003 ; Xiao and Wu 2011 ). DOM
found in natural ground and surface waters are also referred as natural organic
matter (NOM). The most common organic substances are humic substances