Concentration, UV-spectroscopic characteristics and fractionation of DOC in stormflow from an urban stream, Southern California, USA

Environmental context. There is concern that there may be public health issues associated with dissolved organic carbon (DOC) because of its unknown composition and reactivity to disinfection in water used for public supply. Here, changes in the concentration and composition of DOC in stormflow (1995–2004) in the Santa Ana River and its tributaries is evaluated based on its optical properties, molecular weight and solubility differences of the contributing DOC components. Such a study may allow improved water management in the future. Ongoing work in the study area has shown that DOC in surface water diverted for groundwater recharge degrades to near natural levels in underlying aquifers pumped for public supply. Abstract. The composition of dissolved organic carbon (DOC) in stormflow from urban areas has been greatly altered, both directly and indirectly, by human activities and there is concern that there may be public health issues associated with DOC, which has unknown composition from different sources within urban watersheds. This study evaluated changes in the concentration and composition of DOC in stormflow in the Santa Ana River and its tributaries between 1995 and 2004 using a simplified approach based on the differences in the optical properties of DOC and using operationally defined differences in molecular weight and solubility. The data show changes in the composition of DOC in stormflow during the rainy season and differences associated with runoff from different parts of the basin, including extensive upland areas burned prior to the 2004 rainy season. Samples were collected from the Santa Ana River, which drains ~6950 km2 of the densely populated coastal area of southern California, during 23 stormflows between 1995 and 2004. Dissolved organic carbon (DOC) concentrations during the first stormflows of the ‘winter’ (November to March) rainy season increased rapidly with streamflow and were positively correlated with increased faecal indicator bacteria concentrations. DOC concentrations were not correlated with streamflow or with other constituents during stormflows later in the rainy season and DOC had increasing UV absorbance per unit carbon as the rainy season progressed. DOC concentrations in stormflow from an urban drain tributary to the river also increased during stormflow and were greater than concentrations in the river. DOC concentrations in stormflow from a tributary stream, draining urban and agricultural land that contained more than 320000 animals, mostly dairy cows, were higher than concentrations in stormflow from the river and from the urban drain. Fires that burned large areas of the basin before the 2004 rainy season did not increase DOC concentrations in the river during stormflow after the fires – possibly because the large watershed of the river damped the effect of the fires. However, the fires increased the hydrophobic neutral organic carbon fraction of DOC in stormflow from the urban drain and the tributary stream.

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Microbial and Dissolved Organic Carbon Characterization of Stormflow in the Santa Ana River at Imperial Highway, Southern California, 1999-2002

Scientific Investigations Report ◽

10.3133/sir20045116 ◽

2004 ◽

Cited By ~ 3

Author(s):

John A. Izbicki ◽

M. Isabel Pimentel ◽

Menu Leddy ◽

Brian A. Bergamaschi

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Southern California ◽

Santa Ana ◽

Santa Ana River

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Dissolved organic carbon and disinfection by-product precursors in waters of the Chickahominy River basin, Virginia, and implications for public supply

10.3133/wri004175 ◽

2000 ◽

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

River Basin ◽

Public Supply ◽

Chickahominy River

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Fluxes and retention of nutrients and organic carbon in Manko estuary, Okinawa, Japan: influence of river discharge variations

Advances in Oceanography and Limnology ◽

10.4081/aiol.2014.5354 ◽

2014 ◽

Vol 5 (2) ◽

pp. 141 ◽

Cited By ~ 1

Author(s):

D. Shilla

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

River Water ◽

Rainy Season ◽

River Discharge ◽

Geochemical Processes ◽

Dissolved Nutrients ◽

Transport And Transformation ◽

Organic Nutrients ◽

Annual Transport

Estuaries are often considered important filters for inorganic and organic nutrients, as they are located between the land and sea. This study reports on the fluvial fluxes and estuarine transformations and retention of dissolved nutrients (total oxidized nitrogen [TON = NO2− and NO3−]), NH4+, PO43−, and dissolved organic carbon (DOC) in Manko estuary, Okinawa, Japan. The transport and transformation of dissolved nutrients and DOC varied widely among the eight conducted surveys due to variations in freshwater discharge and subsequent flushing times. Under high fluvial discharge, particularly during the May–June rainy season, the transport of nutrients and DOC accounted for up to 70%, 88%, 93%, and 53% of the annual transport of TON, NH4+, PO43−, and DOC, respectively. The flushing times of river water into the estuary, which varied from 0.5 to 46 days, were important in determining the degree to which fluvial nutrients were transformed and retained within the estuary. The effect of long flushing times was evident during the dry months (December–March), when biological and geochemical processes within the estuary removed most of the fluvial nutrients and DOC.

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Damming effect on carbon processing in a subtropical valley-type reservoir in the upper Mekong Basin

10.5194/egusphere-egu2020-26 ◽

2020 ◽

Author(s):

Lin Lin

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Rainy Season ◽

Water Discharge ◽

River Channels ◽

Particulate Carbon ◽

River Continuum ◽

Dissolved Carbon ◽

Carbon Retention ◽

Valley Type

Damming rivers has been identified as one of the most intense artificial perturbations on carbon transportation along the river continuum. To quantify the damming effect on the riverine carbon flux in the upper Mekong River, seasonal carbon fluxes were monitored in a subtropical valley-type reservoir (the Gongguoqiao Reservoir) in 2016. Annually, around 20% of the incoming carbon was sequestered within the reservoir with most of the carbon retention occurring in the rainy season. Since higher rainfalls and water discharge brought large amounts of terrestrial carbon into the reservoir in summer, the concentrations of dissolved organic carbon (DIC), particulate inorganic carbon (PIC) and particulate organic carbon (POC) in the topwater show significant decreasing trends from the river inlet to the outlet (p<0.01). During the cooler dry season (winter), however, the damming effect was much weaker. Precipitation of PIC owing to the alkaline environment and decelerated flow velocity contributed over half of the carbon retention in the reservoir. Correlation between suspended sediment concentration and carbon concentrations reveals that heavy sedimentation also resulted in the sequestration of particulate carbon. Yet the damming impact on the flux of dissolved organic carbon (DOC) was relatively weak due to the short water retention time and refractory nature of allochthonous carbon. The anti-season operation of the dam allowed little time for the decomposition of the incoming DOC in the rainy season. The differentiation processing of the carbon flow significantly increased the dissolved carbon proportion in the outflow. The dams could be acting as filters and the effect might be exacerbated in the cascading system. Accumulation of dissolved organic carbon possibly can accelerate eutrophication processes in the downstream reservoirs and thus altered the aquatic carbon dynamics in the downstream river channels.&#160;

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Seasonal changes of dissolved organic carbon photo-oxidation rates in a tropical humic lagoon: the role of rainfall as a major regulator

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f07-103 ◽

2007 ◽

Vol 64 (9) ◽

pp. 1266-1272 ◽

Cited By ~ 35

Author(s):

Albert Luiz Suhett ◽

André Megali Amado ◽

Alex Enrich-Prast ◽

Francisco de Assis Esteves ◽

Vinicius Fortes Farjalla

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Rainy Season ◽

Annual Rainfall ◽

Rainfall Regime ◽

Photo Oxidation ◽

Oxidation Rates ◽

Doc Concentration ◽

In The Beginning

In this paper, we report the seasonal variation of photo-oxidation rates in a tropical humic lagoon and its relation to annual rainfall regime. Photo-oxidation rates ranged from 8.96 to 415.06 µmol C·L–1·day–1, being higher in the beginning to middle of the rainy season and declining throughout the year. Although dissolved organic carbon (DOC) concentration, water color, and sunlight incidence were generally higher in the rainy season, photo-oxidation rates were not significantly related to any of these parameters. Photo-oxidation seems to be influenced mainly by changes in DOC photoreactivity, which was up to threefold higher early in the rainy season, when inputs of fresh allochthonous DOC take place. In the following months, in addition to being continuously degraded by sunlight, DOC is also removed from the water column by processes such as microbial degradation and sedimentation, leading to a decline in DOC concentration and photoreactivity throughout the year until the next rainy season. Thus, the dynamics of DOC inputs caused by the rainfall regime in Comprida Lagoon lead to a yearly pulse of DOC photoreactivity and photo-oxidation rates. We believe this pulse model also fits other aquatic ecosystems subject to similar seasonal inputs of allochthonous DOC, although rainfall would not necessarily be the driving factor.

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