Spatiotemporal characterization of dissolved carbon for inland waters in semi-humid/semi-arid region, China

Abstract

Abstract. Spatiotemporal variations of dissolved organic carbon (DOC) and inorganic carbon (DIC) in 26 waters across the semi-humid/semi-arid Songnen Plain, China, were examined with data collected during and brackish (n = 12) waters were grouped according to electrical conductivity (threshold = 1000 µS cm −1 ). Significant differences in the average DOC and DIC concentrations were observed between the fresh (5.63 mg L −1 , 37.39 mg L −1 ) and the brackish waters (15.33 mg L −1 , 142.93 mg L −1 ). Colored dissolved organic matter (CDOM) and DOC concentrations were mainly controlled by climatic-hydrologic conditions. The investigation indicated that the outflow conditions in the semi-arid region had condensed effects on the dissolved carbon, resulting in close relationships between salinity vs. DOC (R 2 = 0.66), and salinity vs. DIC (R 2 = 0.94). An independent data set collected in May 2012 also confirmed this finding (DOC: R 2 = 0.79, DIC: R 2 = 0.91), highlighting the potential of quantifying DOC and DIC via salinity measurements for waters dispersed in the plain. Indices based on the CDOM absorption spectra (e.g., the DOC-specific CDOM absorption (SUVA 254 ), absorption ratio a 250 : a 365 (E 250 : E 365 ) and the spectral slope ratio (Sr, S 275−295 /S 350−400 )) were applied to characterize CDOM composition and quality. Our results indicate that high molecular weight CDOM fractions are more abundant in the fresh waters than the brackish waters.

Spatio-seasonal variability of chromophoric dissolved organic matter absorption and responses to photobleaching in a large shallow temperate lake

“…CDOM in Lake Balaton is mainly terrestrial in origin and is thus rapidly degraded by exposure to UV irradiation. The implied importance of photobleaching to carbon dynamics is consistent with previous studies conducted in other inland water bodies (Zhang et al, 2013) as well as other studies carried out in shelf seas (Babin et al, 2003) and the open ocean (Helms et al, 2013).…”

“…We observed rapid changes in the absorption properties of CDOM in response to exposure to natural UV irradiation. In the allochthonous CDOM treatments, the rate of degradation was higher than that ob-tained for Lake Taihu by Zhang et al (2013), who reported a 22 % decrease over 9 days. Bacterial degradation was not noticeable in the allochthonous samples as there was almost no difference in a CDOM (440) for the dark treatment compared to the initial value (Fig.…”

“…The SUVA 254 values measured in Lake Balaton were broadly comparable to those reported for other lake systems. For example, Song et al (2013) reported a maximum value of 8.7 ± 2.8 (L mg −1 m −1 ) for 26 inland water bodies in China. SUVA 254 values were lower than those reported for marine waters where the relative contribution of autochthonous carbon sources is often greater.…”

Spatial Distribution of Diffuse Attenuation of Photosynthetic Active Radiation and Its Main Regulating Factors in Inland Waters of Northeast China

“…Lakes distributed in the Songnen Plain overall displayed high K d (PAR) values. The soil erosion around these lakes was strong, the lakes were shallow, and the re-suspension caused by strong winds in the area also contributed to high turbidity [39]. These findings were in agreement with the research conducted by Olmanson [61], which revealed that lakes of Minnesota that were located in forest regions were clearer than those located in plain regions.…”

“…Unlike reservoirs, most of the lakes are generally shallow and are located in plain areas, particularly in Western Songnen Plain. Due to the character of environmental factors like unevenly distributed precipitation, high evaporation and geomorphology of terminal-flow areas, many fresh and saline water bodies are distributed in the Songnen Plain [39]. …”