Long Term Trends and Dynamics of Dissolved Organic Carbon (DOC) in a Subtropical Reservoir Basin

Abstract

This study evaluates the long term trends and seasonal patterns of dissolved organic carbon (DOC) concentration in the Fei-Tsui Reservoir basin in Northern Taiwan during the period of 2000 to 2015. The non-parametric seasonal Mann-Kendall test was conducted to identify the trends of DOC and its potential drivers (e.g., temperature, runoff, atmospheric acid deposition and stream water chemistry). The monthly tributaries and water surface DOC concentrations in Fei-Tsui Reservoir had showed strong temporal and seasonal variability. The sulfate (SO 4 ) concentration had exhibited statistically significant decreasing trend over a period of 16 years. The decreasing trends of anions (SO 4 and NO 3 ) and base cations (Ca and Mg) as well as increasing trends of pH and acidification index (ACI) in Fei-Tsui Reservoir and streams indicated recovery from acidification. However, there was no significant annual trend in DOC concentration of Fei-Tsui Reservoir and streams. Significant positive correlation was obtained between DOC and trophic state index of Fei-Tsui Reservoir. The results suggested that DOC concentration at the water surface of Fei-Tsui Reservoir was mainly driven by the re-oligotrophication and temperature effects rather than a decrease in atmospheric sulfur deposition. Stream DOC concentration was largely determined by the temporal variability in temperature and rainfall. We concluded that climatic and hydrological factors are the dominant drivers for stream DOC dynamics in the study.

Shifting stoichiometry: Long‐term trends in stream‐dissolved organic matter reveal altered C:N ratios due to history of atmospheric acid deposition

“…with decreasing soil organic matter solubility (Clair et al, 2008), declines in carbon inputs from upstream acidified lakes (Schindler et al, 1997), increases in soil aluminum pools (Löfgren et al, 2010), and greater adsorption of DOM to the mineral layer and infiltration of DOM deeper into permafrost soils (Kendrick et al, 2018;Striegl et al, 2005). Long-term stability in stream DOC concentrations has also been observed (Chow et al, 2017;Clair et al, 2008;Monteith et al, 2007;Worrall et al, 2004), even in some of the longest existing records of stream chemistry (e.g., since 1975; Räike et al, 2012).…”

Study on the Impact of Land-Use Change on Runoff Variation Trend in Luojiang River Basin, China

“…This method does not require a specific distribution test for the data series and allows missing values in the data series. Therefore, it can effectively avoid the influence of undetected values or detected outliers on trends [26], which has been recommended by the World Meteorological Organization and widely used [26][27][28][29]. This paper set up the test of significance of the confidence level of 95% (|Z| > 1.96).…”

Physico-Chemical Characterization of an Urban Rainwater (Zagreb, Croatia)

“…Obtained data can be valuable for environmental quality assessment, as well as for insight into atmospheric deposition processes.Atmosphere 2020, 11, 144 2 of 18 transport and deposition is an important pathway of various substances, including organic compounds and trace metals to the surface environment [5,[8][9][10][11][12][13]. Removal of substances from the atmosphere by precipitation affects chemistry, biogeochemistry, and sedimentation in the aquatic environment [11,14]. These processes have a decisive role in global changes and in environmental protection [5,[8][9][10][11].Dissolved organic matter (DOM), measured as dissolved organic carbon (DOC), is an important component of the rainwater [5].…”

“…This process is crucial for the evaluation of the global carbon cycle [5,15]. The climate change in recent decades has led to increased interest in the study of DOC in atmospheric precipitation [16][17][18][19][20] and surface waters [14] (and references therein).Surface-active substances (SAS) make up a portion of rainwater DOC [21-23] (and references therein) and the water-soluble organic carbon (WSOC) fraction of atmospheric aerosols [24] (and references therein). These compounds are the most reactive part of DOC [25] because they tend to adsorb on the natural phase boundaries (air-water, water-sediment/suspended particles) and, in this way, significantly affect the transfer of mass and energy.…”

“…This process is crucial for the evaluation of the global carbon cycle [5,15]. The climate change in recent decades has led to increased interest in the study of DOC in atmospheric precipitation [16][17][18][19][20] and surface waters [14] (and references therein).…”