Big Soda Lake

DOM is derived from autochthonous sources such as phytoplankton and photosynthetic bacteria (16) at Big Soda Lake near Fallon, Nevada. This lake is alkaline (pH 9.7) and chemically stratified. It contains DOC concentrations as high as 60 mg/L and dissolved salt concentrations as high as 88,000 mg/ L (17). The DOM in this lake is colorless. The fulvic acid fraction was isolated by adsorption chromatography (Amberlite XAD-8 resin) (18) and by zeo-trophic distillation of water from N,N-dimethylformamide (19). Average molecular model synthesis was achieved in a manner similar to that used for fulvic acid from the Suwannee River. The characterization data are presented in Table I and the structural model is presented in Structure 2. 

Table I. Molecular Data Used for Average Structural Model of Fulvic Acid from Big Soda Lake...

Structure 2. One of several average structural models of fulvic acid from Big Soda Lake, Nevada. 

Fulvic acid was isolated in Big Soda Lake above and below the chem-ocline, which occurs at 34-m depth. Water near the lake surface has moderate salinity and is oxygenated, whereas water below the chemocline is hypersaline and anoxic (17). In spite of these environmental differences the chemical character of the fulvic acid from above or below the chemocline did not vary, as determined by elemental analyses and NMR spectrometry. 

The 14C age determination of the fulvic acid isolated rom water near the lake surface was 2300 years before the present, whereas the 14C age was 4900 years before the present for the fulvic acid isolated from water below the chemocline. These old ages for both fulvic acids from Big Soda Lake are in marked contrast to that reported for fulvic acid from the Suwannee River, less than 30 years before the present (11). The refractory nature of this type of fulvic acid derived from phytoplankton and photosynthetic bacteria is significant for carbon-cycling studies. 

Fulvic acid from the Suwannee River was used to calibrate peak-height ratios for aromatic carbon content. The application of this method to fulvic acid samples with known aromatic plus olefinic carbon content from various environments is shown in Table II. Aromatic plus olefinic carbon percentages calculated by the peak-height ratio method using lH NMR data closely agree with these percentages computed from 13C NMR data, with the exception of the Big Soda Lake samples. 

Determination Method Suwannee River above Fargo, GA Big Soda Lake near Fallon, NV Calcasieu River near Kinder, LA Mississippi River near St. Francisville, LA... 

Variation among Sampling Sites. Dissolved humic substance samples from seven end-member environments were isolated for study. Autochthonous inputs to DOM were expected to dominate in Big Soda Lake and in Island Lake, which is a groundwater-sustained eutrophic lake in the sandhills of western Nebraska. Allochthonous inputs to DOM from a swamp environment predominate in the Suwannee River. They also dominate in the Calcasieu River in western Louisiana, but the proportion of swampland is much lower there. The Temi River is a tropical blackwater tributary of the Orinoco River in Venezuela, where allochthonous inputs dominate. The entire Sagavanirktok River basin is located north of the tree line on the North Slope of Alaska a mixture of allochthonous and autochthonous inputs was expected for the various rivers and lakes in this basin. Lastly, Hidden Lake Creek, which is the outlet of Hidden Lake on the Kenai Peninsula of Alaska, was sampled to determine if nutrient inputs from decaying salmon were contributing to primary production and autochthonous inputs to DOM. 

In conclusion, DOM in water is a complex mixture of degraded moderate-sized biomolecules. As degradation proceeds in the aquatic environment, carbohydrates and lignin degradation products disappear within days to a few years. Only the carboxylated aliphatic alicyclic component persists for thousands of years in the marine environment (35) or in isolated lake environments like Big Soda Lake, Nevada. 

The author thanks Stephen W. Robinson and Yousif K. Kharaka of the U.S. Geological Survey, Menlo Park, California, for initiating the research investigation of the 14C age of DOM in Big Soda Lake, Nevada. The 14C ages were determined by Stephen W. Robinson. 

Iverson N., Oremland R. S., and King M. J. (1987) Big Soda Lake (Nevada) 3. Pelagic methanogenesis and anaerobic methane oxidation. Limnol. Oceanogr. 32, 804-814. 

Rosen, M.R., Arehart, G.B. Lico, M.S. (2004) Exceptionally fast growth rate of a <100 year old tufa, Big Soda Lake, Nevada Implications for using tufa as a paleoclimatic proxy. Geology 32, 409-412. 

Big Soda Lake, Mangrove Lake), interferring carotenols were removed via phase separation into 90% aqueous methanol (25-26). 

Mono, Big Soda, Walker, Crowley, and Searles desert alkaline lakes ... 

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