Preliminary Data from a Comprehensive Savannah River Study: The First 6 Months (original) (raw)
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Dynamics of Oxygen Demand Within the Middle and Lower Savannah River Basins
Ensuring dissolved oxygen (DO) concentrations remain above a certain critical minimum is important for sustaining healthy riverine systems. Since rivers worldwide are typically undersaturated with respect to DO and oversaturated with respect to carbon dioxide (CO 2), it is clear that oxygen loss mechanisms override oxygen production mechanisms in rivers. The predominant loss mechanism is bacterial respiration of carbonaceous and ammoniacal substrates. These substrates originate from both natural and human derived sources and have a range of bacterial degradation rates so some are broken down quickly while others require longer processing periods. Understanding DO dynamics within rivers is further complicated by the temporal-spatial dynamics as a single mass of water flows through various land use types toward a terminal water body. Each land use type contributes a myriad of substrates that can stimulate aerobic bacterial respiration resulting in loss of DO. The location of the exertion of oxygen loss along a river length as a result of a particular source is then a function of the input location, the exertion rate, and the river flow. In order to ensure that critical DO minima are met along an entire river length, it is therefore important to understand the juxtaposition of these parameters in order to resolve low DO concentrations within a particular stretch of river. This study was designed to assess the temporal-spatial dynamics of oxygen demanding substances along 200 river miles of the mainstem Savannah River basin. We sampled the mainstem of the Savannah River on a bimonthly basis from several of 12 permanent monitoring stations as well as several natural and human derived sources. For each sampling event, a Lagrangian sampling scheme (repeatedly sampling the same mass of water at multiple locations according to travel time) was used for the mainstem river samples which allowed an opportunity to assess effects due to land use differences. We used a 120 day bottle incubation period (GAEPD protocol) to determine the oxygen consumption rates and ultimate DO loss for each of the samples. Results of the Lagrangian sampling consistently showed that there was not a steady increase or decrease in ultimate oxygen consumption or consumption rates with downstream flow but showed that consumption changed with changing land usage. The data also showed that oxygen demand trends at a single site over time varied from 15-75%. These data indicate that further research is necessary in order to better characterize the sources of oxygen demanding substances within the Savannah River.
Biochemical Oxygen Demand in the Savannah River Basin: Results from Six Years of Research
2015
Biochemical oxygen demand (BOD) is a regulatory parameter that is used to determine how much oxygen will be consumed by a particular natural or manmade discharge to a water body. Over the past six years, we have assessed oxygen demand dynamics within this river system by applying multiple methods, experiments, and analysis approaches. By using a Lagrangian sampling approach (sampling according to travel time) from 2006-2008, we found that the river acts as a conduit for dissolved organic material in the winter but undergoes moderate organic matter loss in the summer. Using the EPA approved Long Term Biochemical Oxygen Demand method, we found large seasonal intra-site variability (20% to 90% coefficient of variation) for all sampled sites but also found that the oxygen consumption rate used in the Total Maximum Daily Load calculations for the Savannah Basin underestimates the fast kinetic rate and overestimates the slow kinetic rate used in the current modeling effort. Using a real-t...
Modeling Biochemical Oxygen Demand Through the Middle and Lower Savannah River 1
JAWRA Journal of the American Water Resources Association, 2013
In order to improve modeling accuracy and general understanding of lotic biochemical oxygen demand (BOD), this study characterized river metabolism with the current Georgia Environmental Protection Division method for the middle and lower Savannah River basin (MLSRB) and several alternative methods developed with 120-day, long-term biochemical oxygen demand (LTBOD) data from the MLSRB. The data were a subset of a larger two-year LTBOD study to characterize and understand BOD in the MLSRB, located approximately between Augusta, Georgia, and Savannah, Georgia, along the border of Georgia and South Carolina. The LTBOD data included total oxygen loss and nitrogen speciation for separately quantifying nitrification. Results support the following insights and opportunities for modeling methods: (1) it is important to modeling accuracy that residuals be checked for even dispersion to avoid areas of over-and underprediction; (2) modeling with bounded, yet unfixed, rates is a sufficiently simple alternative to fixed-rate modeling that can eliminate the need for manual adjustments and provide additional system understanding to inform regulation; (3) if fixed rates modeling is desired, model quality for this system might be improved through revising the current low rate (along with the associated f-ratio updates) from 0.02 ⁄ day rate to 0.006 ⁄ day and potentially adding a new rate at 1.0 ⁄ day in some cases; and (4) the current 57 ⁄ 43 ratio of slow ⁄ fast BOD is reasonable based on the 52 ⁄ 45 ⁄ 3 slow ⁄ fast ⁄ faster BOD proportions of this study.
Temporal variability in sources of dissolved organic carbon in the lower Mississippi river
Geochimica Et Cosmochimica Acta, 2004
Here we report on the temporal changes in the composition of dissolved organic carbon (DOC) collected in the tidal freshwater region of the lower Mississippi River. Lignin-phenols, bulk stable carbon isotopes, compound-specific isotope analyses (CSIA) and 13 C nuclear magnetic resonance (NMR) spectrometry were used to examine the composition of high molecular weight dissolved organic matter (HMW DOM) at one station in the lower river over 6 different flow regimes in 1998 and 1999. It was estimated that the annual input of DOC delivered to the Gulf of Mexico from the Mississippi River was of 3.1 ϫ 10 Ϫ3 Pg, which represents 1.2% of the total global input of DOC from rivers to the ocean. Average DOC and HMW DOC were 489 Ϯ163 and 115 Ϯ 47 M, respectively. 13 C-NMR spectra revealed considerably more aliphatic structures than aromatic carbons in HMW DOC. Lignin phenols were significantly 13 C-depleted with respect to bulk HMW DOM indicating that C 4 grass inputs to the HMW DOM were not significant. It is speculated that C 4 organic matter in the river is not being converted (via microbial decay) to HMW DOM as readily as C 3 organic matter is, because of the association of C 4 organic matter with finer sediments. The predominantly aliphatic 13 C NMR signature of HMW DOM suggests that autochthonous production in the river may be more important as a source of DOC than previously thought. Increases in nutrient loading and decreases in the suspended load (because of dams) in the Mississippi River, as well as other large rivers around the world, has resulted in significant changes in the sources and overall cycling of riverine DOC.
Aquatic Sciences, 2016
We examined seasonal and spatial patterns in dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) in the Chowan River watershed, North Carolina, a blackwater river which discharges into the second largest estuary in the United States, the Albemarle-Pamlico Estuarine System. From April 2008 to May 2010, DOC concentration did not significantly vary across seasons (range 7.69-30.39 mg L-1); however, CDOM molecular size and aromaticity increased throughout the spring, decreased during the summer and fall, and remained relatively low in the winter. Spectral slope ratios suggested microbial processing of CDOM in the spring and photodegradation of CDOM in the summer and fall. Spatially, DOC and CDOM concentrations were similar in the mainstem and at the mouths of two tributaries, Bennetts Creek and Wiccacon River, but were significantly higher upstream on the tributaries. DOC concentration was positively correlated with CDOM absorbance coefficients at 254 and 350 nm; however, these optical proxies explained only *60 % of the variance. DOC and CDOM absorption loads to the Albemarle Sound ranged from 2.63 9 10 10g year-1 and 9.84 9 10 10 m 2 year-1 , respectively, in a dry year and 7.9 9 10 10 g year-1 and 2.2 9 10 11 m 2 year-1 , respectively, in a wet year, which are comparable to nonblackwater rivers with larger watersheds. Blackwater rivers may therefore represent ''hotspots'' in coastal carbon chemistry, with seasonal variations in the quality and quantity of DOC and CDOM influencing estuarine food web dynamics and net ecosystem metabolism.
Geochimica et Cosmochimica Acta, 2012
The relative importance of hydrological conditions and upstream processes on the input and transport of organic carbon from land to sea was investigated in the Mullica River, a small system located in the southeastern New Jersey (USA), using molecular and d 13 C compositions. Sediment and particulate organic carbon (POC) samples were collected along the river, from upstream (draining predominantly pine-oak forests) in the Pinelands to the Great Bay Estuary (bordered by salt marshes) under normal and high flow conditions. During base river flow, terrestrial biomarkers (e.g., diterpenoids-conifer biomarkers) were detected predominantly upstream and sharply decreased downstream. From mid to down river sites, a mixture of higher plants (primarily from the salt marsh vegetation) and microbial biomarkers (e.g., mycose, cholesterol) predominated. d 13 C abundances of individual fatty acids presented a consistent pattern, with depleted values (e.g., d 13 C sed = À30.9& on average) upstream, becoming heavier toward the Great Bay (e.g., d 13 C sed = À23.1&; d 13 C POC = À22.8&). During the high discharge event, significant amounts of upland biomarkers (e.g., pimaric acid, ferruginol, ursolic acid) and depleted d 13 C values were observed from the Pinelands (d 13 C sed = À34.6&) to mid river (d 13 C sed = À32.0&; d 13 C POC = À30.8&), clearly demonstrating the transport of terrestrial material farther down river. However, downstream of this point, the occurrence of the terrestrial material strongly decreased, demonstrating that terrestrial plant biomarkers were not transported in significant amounts to the estuarine region, even at high river discharge. Since the mid river site is situated in the upper limit of salt water intrusions, it is likely that flocculation and sedimentation provide a depositional sink for terrestrial OC in the mid Mullica River, thereby depleting the terrigenous signature in downstream OC.
Dissolved organic carbon fluxes in the Shetucket River of eastern Connecticut, U.S.A.*
Freshwater Biology, 1978
Seasonal changes in dissolved organic carbon (DOC) concentrations were monitored biweekly for 1 year at seven stations in the Shetucket River watershed in eastern Connecticut, U.S.A. Nine monthly diurnal studies revealed 24-h fluctuations of up to 53% of the seasonal range of 250-2200 MM DOC. Net DOC removal along a 1.9-km stretch below a secondary sewage treatment plant (activated sludge effluent diluted to a final average volume of 1.4% in the river) ranged from 0 to 1600 and averaged 68 ±64 mmol m"^day"'. Removal of DOC further downstream could only be observed during a severe 3-h October storm when net uptake ranged from 16 to 92mmol m"^^ h"\ using upstreamdownstream techniques. Oxygen respiration could account for about half of the net DOC removal during the October storm. Even though net uptake was somewhat greater than reported in other lotic studies, about 97% of the DOC potentially available to benthic heterotrophs was exported further downstream. introduction Dissolved organic carbon (DOC) in lotic systems originates from several sources. In smaller headwater streams, almost all of the DOC is of terrestrial origin (Hynes, 1963) and most is exported downstream (Fisher & Likens, 197 2). In larger systems other sources of DOC become important. Excreted algal products (
Carbon, Nitrogen, And Phosphorus Discharge From The Altamaha River, Georgia
1989
Quantitative and qualitative aspects of the discharge of nutrients frxxn the Altamaha River to the coastal interface zone (CXZ) of Georgia was examined over a two year period. Sampling for various forms of carbon (dissolved organic, particulate organic), nitrogen (dissolved organic, particulate organic, ammonium, nitrate plus nitrite) and phosphorus (dissolved orthophosphate) was carried out at eleven stations located throughout the tidal portion of the river. Dissolved organic forms of carbon and nitrogen dominated the total annual discharge of these nutrients. Changes in the concentration of all dissolved nutrient forms occurred during passage of river water through the tidal freshwater portion of the river. Inorganic nutrients (ammonium, nitrate plus nitrate, dissolved orthophosphate) were decreased on several dates, while organic nutrients (dissolved organic carbon, dissolved organic nitrogen) were increased on several dates. These changes occurred during a wide range of physical conditions. Nutrient budgets indicate that riverine discharge of carbon was equal to appx. 10% of the total carbon available within the CIZ. Riverine discharge of nitrogen accounts for appx. 50% of the total new nitrogen available to the CIZ. This input of nitrogen from rivers is sufficient to supply appx. 10% of the annual needs of primary producers within the d Z. viii CARBCN, NITROGEN, AND PHOSHK3ROUS DISCHARGE FRCM THE ALTAMAHA RIVER, GEORGIA 1) Volume of tidal freshwater during all but high flow months (i.e. March 1983f April 1984): Assumed to be equal to the volume of the 'tidal fresh' zone. Volume of 'tidal fresh' zone = Surface area of 'tidal fresh zone* * Avg depth of Altamaha estuary (1.0*10* m*) * <2.65 m) * 2.6*10'' ' m* 2) Volume of tidal freshwater during high flow periods (i.e. March 1983, April 1984): Assumed to be sum of 'tidal fresh zone* volume plus 'mixing zone' volume. Volume of 'mixing zone'* Surface area of 'mixing zone* * Avg depth of Altamaha estuary <2.1*10* *«> * <2.65 m) * 5.6*10* m 3 Volume of 'tidal fresh zone' * Volume of 'mixing zone*-(2.65*10* m 3 > ♦ (5.6*10* m*> * 8.2*10* m» 3) Residence time: Volume/riverflow (freshwater volume m*)/((Riverflow m * / d a y) (8 6 4 0 0 sec/day))
Journal of Geophysical Research, 2007
1] In this study, we examined the temporal and spatial variability of dissolved organic matter (DOM) abundance and composition in the lower Mississippi and Pearl rivers and effects of human and natural influences. In particular, we looked at bulk C/N ratio, stable isotopes (d 15 N and d 13 C) and 13 C nuclear magnetic resonance (NMR) spectrometry of high molecular weight (HMW; 0.2 mm to 1 kDa) DOM. Monthly water samples were collected at one station in each river from August 2001 to 2003. Surveys of spatial variability of total dissolved organic carbon (DOC) and nitrogen (DON) were also conducted in June 2003, from 390 km downstream in the Mississippi River and from Jackson to Stennis Space Center in the Pearl River. Higher DOC (336À1170 mM), C/N ratio,% aromaticity, and more depleted d 15 N (0.76À2.1%) were observed in the Pearl than in the lower Mississippi River (223À380 mM, 4.7À11.5%, respectively). DOC, C/N ratio, d 13 C, d 15 N, and % aromaticity of Pearl River HMW DOM were correlated with water discharge, which indicated a coupling between local soil inputs and regional precipitation events. Conversely, seasonal variability in the lower Mississippi River was more controlled by spatial variability of a larger integrative signal from the watershed as well as in situ DOM processing. Spatially, very little change occurred in total DOC in the downstream survey of the lower Mississippi River, compared to a decrease of 24% in the Pearl River. Differences in DOM between these two rivers were reflective of the Mississippi River having more extensive river processing of terrestrial DOM, more phytoplankton inputs, and greater anthropogenic perturbation than the Pearl River.