Seasonal characterization of CDOM for lakes in semiarid regions of Northeast China using excitation–emission matrix fluorescence and parallel factor analysis (EEM–PARAFAC)

Abstract

Abstract. The seasonal characteristics of fluorescent components in chromophoric dissolved organic matter (CDOM) for lakes in the semiarid region of Northeast China were examined by excitation–emission matrix (EEM) spectra and parallel factor analysis (PARAFAC). Two humic-like (C1 and C2) and protein-like (C3 and C4) components were identified using PARAFAC. The average fluorescence intensity of the four components differed under seasonal variation from June and August 2013 to February and April 2014. Components 1 and 2 exhibited a strong linear correlation (R2 = 0.628). Significantly positive linear relationships between CDOM absorption coefficients a(254) (R2 = 0.72, 0.46, p < 0.01), a(280) (R2 = 0.77, 0.47, p < 0.01), a(350) (R2 = 0.76, 0.78, p < 0.01) and Fmax for two humic-like components (C1 and C2) were exhibited, respectively. A significant relationship (R2 = 0.930) was found between salinity and dissolved organic carbon (DOC). However, almost no obvious correlation was found between salinity and EEM–PARAFAC-extracted components except for C3 (R2 = 0.469). Results from this investigation demonstrate that the EEM–PARAFAC technique can be used to evaluate the seasonal dynamics of CDOM fluorescent components for inland waters in the semiarid regions of Northeast China, and to quantify CDOM components for other waters with similar environmental conditions.

A systematic examination of the relationships between CDOM and DOC in inland waters in China

“…Further, lower DOC concentrations are also measured with ice samples, which is consistent with previous findings (Bezilie et al, 2002;Shao et al, 2016). But relatively high DOC concentrations were observed for underlying waters covered by ice in Northeast China due to the condensed effect caused by the DOC discharged from ice formation (Bezilie et al, 2002;Shao et al, 2016;Zhao et al, 2016a). This condensed effect was particularly marked in these shallow water bodies where ice forming remarkably condensed the DOC in the underlying waters (Zhao et al, 2016a).…”

“…Total suspended matter (TSM) was determined gravimetrically using precombusted Whatman GF/F filters with a 0.7 µm pore size, details can be found in Song et al (2013). DOC concentrations were measured by high temperature combustion (HTC) with water samples filtered through 0.45 µm Whatman cellulose acetone filters (Zhao et al, 2016a). The standards for dissolved total carbon (DTC) were prepared from reagent grade potassium hydrogen phthalate in ultra-pure water, while dissolved inorganic carbon (DIC) concentrations were determined using a mixture of anhydrous sodium carbonate and sodium hydrogen carbonate.…”

“…But relatively high DOC concentrations were observed for underlying waters covered by ice in Northeast China due to the condensed effect caused by the DOC discharged from ice formation (Bezilie et al, 2002;Shao et al, 2016;Zhao et al, 2016a). This condensed effect was particularly marked in these shallow water bodies where ice forming remarkably condensed the DOC in the underlying waters (Zhao et al, 2016a). It also should be noted that DOC concentration has a strong connection with hydrological condition and catchment landscape features (Neff et al, 2006;Ågren et al, 2007;Lee et al, 2015).…”

“…Waters in Northeast China are surrounded by forest, wetlands, and grassland and therefore they generally exhibited a high proportion of colored fractions of DOC. Further, soils in Northeast China are rich in organic carbon, which may also contribute to high concentrations of DOC and CDOM in waters in this region (Jin et al, 2016;Zhao et al, 2016a). Compared with waters in East and South China, waters in Northeast China showed less algal bloom due to the low temperature; thus, autochthonous CDOM was less present in waters in Northeast China Zhao et al, 2016a).…”

“…The allochthonous CDOM is mainly derived from the surrounding terrestrial ecosystems, and it comprises a continuum of small organic molecules to highly polymeric humic substances. In terms of CDOM originating from anthropogenic sources, it contains fatty acids, amino acids, and sugar; thus, the composition of CDOM is more complex than that from natural systems (Zhou et al, 2016;Zhao et al, 2016a). Hydrological factors also affect the DOC and CDOM characteristics and particularly the discharge, catchment area, land use, and travel time are the important ones (Neff et al, 2006;Jaffé et al, 2008;Spencer et al, 2012).…”