Environmental Engineering Reference
In-Depth Information
del Vecchio and Blough 2002 ; Vähätalo et al. 2000 ; Bertilsson and Tranvik 2000 ;
Allard et al. 1994 ; Amador et al. 1989 ; Fujiwara et al. 1995 ; Bertilsson and Allard
1996 ; Granéli et al. 1996 ; Granéli et al. 1998 ; Miller and Moran 1997 ; Clark et al.
2004 ; Xie et al. 2004 ; Johannessen et al. 2007 ; Fichot and Miller 2010 ). In surface
waters, the rate of photoinduced mineralization of CDOM ( pm z , mol C m 3 d 1 ),
modified by Vähätalo et al. ( 2000 ) from Schwarzenbach et al. ( 1993 ) and Miller
( 1998 ), can be expressed as follows (Eq. 4.1 ):
λ MAX
PM Z =
ϕ λ Q S,Z, λ A CDOM, λ D λ
(4.1)
λ MIN
where ϕ λ is the spectrum of the apparent quantum yield for photoinduced min-
eralization (mol produced DIC/mol absorbed photons), Q s,z, λ is the scalar photon
flux density spectrum at the depth z (also referred to as actinic flux, mol photons
m 2 d 1 ), and λ a CDOM, λ is the absorption spectrum of CDOM (m 1 ). The param-
eters λ max and λ min are the minimum and maximum wavelengths contributing to
photoinduced mineralization.
In the whole water column the rate of photoinduced mineralization, modified by
Vähätalo et al. ( 2000 ) from Miller ( 1998 ), can be expressed as follows (Eq. 4.2 ):
λ MAX
PM =
ϕ λ Q A, λ ( A CDOM, λ / A TOT, λ ) D λ
(4.2)
λ MIN
where Q a, λ represents the photons absorbed by the water column (mol photons
m 2 d 1 ) and the a CDOM, λ / a tot, λ ratio expresses how much CDOM contributes
to the total absorption. In infinitely deep waters, Q a, λ roughly equals the down-
ward vector photon flux density just below the surface ( Q d,v,0- λ ) (Sikorski and Zika
1993 ; Sikorski and Zika 1993 ).
The quantum yields related to CDOM decrease exponentially with increasing
wavelength (Moran and Zepp 1997 ; Vähätalo et al. 2000 ; Sikorski and Zika 1993 ;
Ratte et al. 1998 ; Gao and Zepp 1998 . A generalized equation linking quantum
yield and wavelength (Vähätalo et al. 2000 ) can be expressed as below (Eq. 4.3 ):
ϕ λ = c × 10 d λ
(4.3)
where c (dimensionless) and d (nm 1 ) are positive constants and λ is wavelength
(nm). Different combinations of c and d can cover a wide range of exponential
relationships between quantum yield and wavelength.
4.3.2 CDOM Absorption Loss in Long- and Short-Wavelengths
Due to Photoinduced Degradation
Photoinduced degradation rapidly lowers the CDOM absorption coefficients
across the entire spectrum, both in natural waters and in standard organic sub-
stances (Fig. 1 ) (Vodacek et al. 1997 ; Zhang et al. 2009 ; Shank et al. 2010 ; Moran
et al. 2000 ; Hernes and Benner 2003 ; Winter et al. 2007 ; del Vecchio and Blough
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