482
K. M. G. Mostofa et al.
(C-like) at the peak C-region is relatively high, or similar to the intensity at the
peak A-region (Fig. 3h–j; Table 2) (Mostofa et al. 2009b; Stedmon and Markager
2005a; Balcarczyk et al. 2009). In contrast, the fluorescence intensity of allochthonous fulvic acid (C-like) is higher at peak A-region than at peak C-region
(Figs. 2a, 3a). The autochthonous fulvic acid (C-like) showed fluorescence
peaks at Ex/Em = 340–350/460 nm in the peak C-region and at 260/460 nm in
the peak A-region in mainstream and tributaries of NenJiang River, China; at
335–340/442–464 nm and 260/442–464 nm in surface waters of Lake Hongfeng,
China; at ~360/~460 nm (peak A-region not mentioned) in streams; at 340–
350/460, 340/448–454 and 260–270/448–454 nm upon photo-assimilation
of algae in Milli-Q and river water; at 340/448–455, 290–300/430–448, and
260–448 nm upon microbial respiration (or assimilation) in Milli-Q and river
water; at 365/453 and 270/453 nm upon microbial respiration (or assimilation)
of phytoplankton in isotonic water (0.5 ‰ salinity); at 355/445 and 280/435 nm
when originateng from algae under both light and dark incubation (12 h each);
at 350/400–450 and 275/400–450 nm in bay waters (Brazil); at 370/466 and
<260/466 nm in the deep waters of Okhotsk Sea and the North Pacific Ocean; at
340/420 and 260/420 nm in the Southern ocean; at 355/434 and 260/434 nm in
north Pacific and Atlantic oceans; and at 330–350/420–480 and 250–260/420–
480 nm in marine waters (Table 2) (Mostofa et al. 2009b; Coble 1996, 2007;
Parlanti et al. 2000; Stedmon et al. 2007a; Zhang et al. 2009a; Wedborg et al.
2007; Luciani et al. 2008; Zhao et al. 2009; Chen et al. 2010; Yamashita et al.
2010; Balcarczyk et al. 2009; Murphy et al. 2008).
On the other hand, the second fluorescent component of algal or phytoplankton origin can exhibit one strong fluorescence peak in the peak C-region and one
minor peak (not often shown) in the peak A-region. The peak in the C-region is
located at shorter wavelengths compared to the first component of autochthonous
fulvic acid (C-like) (Fig. 3k, l) (Mostofa et al. 2009b; Coble 1996, 2007; Parlanti
et al. 2000; Stedmon et al. 2003, 2007a; Stedmon and Markager 2005a, 2005b;
Zhang et al. 2009a; Balcarczyk et al. 2009; Murphy et al. 2008; Yamashita et al.
2008; Yamashita and Jaffé 2008; Wang et al. 2007). Considering the EEM images
of the second fluorescent component, which are similar to those of allochthonous
fulvic acid (M-like) (Fig. 3c) and of marine humic acid denoted as M (Coble
1996), such component can be denoted as autochthonous fulvic acid (M-like). The
autochthonous fulvic acid (M-like) of algae or phytoplankton origin usually exhibits two fluorescence peaks at Ex/Em = 290–330/358–434 nm in the peak C-region
and at 225–360/358–416 nm in the peak A-region (Table 2). The autochthonous
fulvic acid (M-like) is often detected in several studies in field and experimental observations, at Ex/Em = 295–300/396–422 nm in the peak C-region and at
235–240/396–422 nm in the peak A-region in surface waters (0–25 m) of Lake
Hongfeng, China; at 315/372 nm in the waters of Lake Taihu; at 322/407 nm in
the waters of Lake Taihue; at 300/406 and 240/405 nm upon microbial respiration (or assimilation) of algae in river water; at 290–310/400–410 nm upon microbial assimilation of marine algae in Milli-Q water; at 295/398 nm upon microbial
production in a mesocosm experiment; at 320–325/388–428 nm in estuaries;
K. M. G. Mostofa et al.
(C-like) at the peak C-region is relatively high, or similar to the intensity at the
peak A-region (Fig. 3h–j; Table 2) (Mostofa et al. 2009b; Stedmon and Markager
2005a; Balcarczyk et al. 2009). In contrast, the fluorescence intensity of allochthonous fulvic acid (C-like) is higher at peak A-region than at peak C-region
(Figs. 2a, 3a). The autochthonous fulvic acid (C-like) showed fluorescence
peaks at Ex/Em = 340–350/460 nm in the peak C-region and at 260/460 nm in
the peak A-region in mainstream and tributaries of NenJiang River, China; at
335–340/442–464 nm and 260/442–464 nm in surface waters of Lake Hongfeng,
China; at ~360/~460 nm (peak A-region not mentioned) in streams; at 340–
350/460, 340/448–454 and 260–270/448–454 nm upon photo-assimilation
of algae in Milli-Q and river water; at 340/448–455, 290–300/430–448, and
260–448 nm upon microbial respiration (or assimilation) in Milli-Q and river
water; at 365/453 and 270/453 nm upon microbial respiration (or assimilation)
of phytoplankton in isotonic water (0.5 ‰ salinity); at 355/445 and 280/435 nm
when originateng from algae under both light and dark incubation (12 h each);
at 350/400–450 and 275/400–450 nm in bay waters (Brazil); at 370/466 and
<260/466 nm in the deep waters of Okhotsk Sea and the North Pacific Ocean; at
340/420 and 260/420 nm in the Southern ocean; at 355/434 and 260/434 nm in
north Pacific and Atlantic oceans; and at 330–350/420–480 and 250–260/420–
480 nm in marine waters (Table 2) (Mostofa et al. 2009b; Coble 1996, 2007;
Parlanti et al. 2000; Stedmon et al. 2007a; Zhang et al. 2009a; Wedborg et al.
2007; Luciani et al. 2008; Zhao et al. 2009; Chen et al. 2010; Yamashita et al.
2010; Balcarczyk et al. 2009; Murphy et al. 2008).
On the other hand, the second fluorescent component of algal or phytoplankton origin can exhibit one strong fluorescence peak in the peak C-region and one
minor peak (not often shown) in the peak A-region. The peak in the C-region is
located at shorter wavelengths compared to the first component of autochthonous
fulvic acid (C-like) (Fig. 3k, l) (Mostofa et al. 2009b; Coble 1996, 2007; Parlanti
et al. 2000; Stedmon et al. 2003, 2007a; Stedmon and Markager 2005a, 2005b;
Zhang et al. 2009a; Balcarczyk et al. 2009; Murphy et al. 2008; Yamashita et al.
2008; Yamashita and Jaffé 2008; Wang et al. 2007). Considering the EEM images
of the second fluorescent component, which are similar to those of allochthonous
fulvic acid (M-like) (Fig. 3c) and of marine humic acid denoted as M (Coble
1996), such component can be denoted as autochthonous fulvic acid (M-like). The
autochthonous fulvic acid (M-like) of algae or phytoplankton origin usually exhibits two fluorescence peaks at Ex/Em = 290–330/358–434 nm in the peak C-region
and at 225–360/358–416 nm in the peak A-region (Table 2). The autochthonous
fulvic acid (M-like) is often detected in several studies in field and experimental observations, at Ex/Em = 295–300/396–422 nm in the peak C-region and at
235–240/396–422 nm in the peak A-region in surface waters (0–25 m) of Lake
Hongfeng, China; at 315/372 nm in the waters of Lake Taihu; at 322/407 nm in
the waters of Lake Taihue; at 300/406 and 240/405 nm upon microbial respiration (or assimilation) of algae in river water; at 290–310/400–410 nm upon microbial assimilation of marine algae in Milli-Q water; at 295/398 nm upon microbial
production in a mesocosm experiment; at 320–325/388–428 nm in estuaries;