Lake sampling

Sampling Methods From the outset of the high density lake sampling program in 1987, the application of a robust and consistent sampling protocol was considered paramount and this is still the case. Lake sediment and water sampling is performed by 2-person teams primarily from float-equipped Bell 206B helicopters. 

Lake samples are more similar to the glacier samples than to fresh samples obviously adipocere formation is similar in glaciers and a deep alpine lake. 

For comparison the same fatty acid data have been visualized by Sammon s NLM with parameter p set to 1 which makes a local mapping preserving well the small distances between objects (Figure 3.25, left). The NLM result shows a compact cluster of the fresh reference samples (class 6), and somewhat separated the desert sample (5). The horizontal map coordinate separates fresh samples from the high mountain samples (4) and the other samples (glacier samples, 2 lake samples, 3 and iceman samples, 1). The clustering has been indicated by manually drawn ellipses it is very similar as obtained with the scores of the PCI and PC2. Furthermore, Figure 3.25... 

Fresh reference samples (class 6), samples from Glacier samples (2), lake samples high mountain Ampato (4), and from desert (5) (3), and iceman samples (1)... 

Diehlorobenzidine in lake water samples was not metabolized by mieroorganisms over a 4-week period (Sikka et al. 1978) although 1 lake sample of the 2 tested eontained approximately 5 million microorganisms per mL. The composition of the biologieal eommunity was not described. Minor decreases in 3,3 -dichlorobenzidine concentrations were attributed to adsorption onto suspended sediment. 

Error bars are standard error of the mean. Also included for reference is the weekly mass concentration measured at the Mono Lake sampling site. Error bars are 15% measurement system error. 

Figure 10.1. Four measurement results corresponding to measurands. 1, the amount concentration of chromium in the test sample 2, the amount concentration of chromium(VI) in the test sample 3, the amount concentration of chromium(VI) in the lake sampled and 4, the amount concentration of bioavailable chromium(VI) in the lake sampled.

Figure 3. Locations of the lakes sampled in Vilas County, WI. Trout Lake was not sampled. Little Rock Lake has been artificially divided thus, it was sampled as two different lakes (Little Rock North and Little Rock South).

The observed slow increase in 15N content of POM at the start of the experiment was probably caused by isotopic dilution from unlabeled dissolved inorganic nitrogen (DIN) brought into the lake from the catchment or input from the hypolimnion via cross-thermocline mixing. Horizontal mixing in the epilimnion is rapid in this small lake samples of moss and periphyton from next to the 15N drippers and on the opposite shores of the lake were equally labeled. 

Figure 10. 31P FT-NMR spectra of Crystal Lake samples. Letters correspond to sample designations in Table I. (Continued on next page.)...

Figure 12. 31P FT-NMR spectrum of Crystal Lake sample G, 1000-dalton membrane retentate fraction, before and after alkaline bromination. The total soluble phosphorus concentration was 50 mg of P/L.

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. 

H NMR data from these seven sites are presented by spectral peak-height ratios in Table III. The sites were listed in order of increasing aromatic plus olefinic carbon percentages. Fulvic acids from all the lake samples are much lower in aromatic plus oleflnic carbon content than those from river samples. These results confirm the hypothesis that autothonous inputs result in dissolved humic substances that have a low aromatic plus oleflnic carbon content. The lake samples also are lower in the ratios of peak 2 (carboxylated chains and aliphatic ketones), peak 3 (carbohydrates), and peak 4 (phenolic tannins and lignins) to peak 1 (branched methyl groups and alicyclic ali-phatics) than are the river samples. 

Figure 8. Effect of baseline acid-neutralizing capacity (ANC) and episodic conditions in Adirondack lakes, a, Relationship between baseline ANC and the springtime depression in ANC (baseline ANC—minimum ANC) for 11 lakes sampled in 1986 and 1987. b, The relative contributions of base cations (Cb) and nitrate (N03 ) to the springtime ANC depressions in Adirondack lakes. Lakes at intermediate ANC values undergo the largest springtime depressions in ANC. Lakes with lower baseline ANC are affected more by N03 pulses, and lakes with higher baseline ANC are affected more by base-cation dilution. Solid lines represent best-fit relationships. (Redrawn with permission from reference 126. Copyright 1990 American Geophysical Union.)...

Equilibrium calculations suggested that Hg complexation varies greatly among redox and pH levels typical of the regions of lakes sampled during this study. In an oxic lake, pore water, and groundwater, Hg complexation with organic matter most likely dominates. Under anoxic conditions in the hypolimnion and pore waters, Hg most likely forms soluble bisulfide and polysulfide complexes. 

Measurements of 14C have rarely been used as tracers to study sources of individual DOC fractions. Aiken et al. (1996) used 14C measurements of fulvic acid in a permanently ice-covered closed basin lake in Antarctica to investigate sources of DOC in the lake. Sampling along a depth profile in the lake showed that the fraction of modern carbon decreased with depth and confirmed that the high concentrations of fulvic acid in the bottom waters represented an old source, with an age of around 3000 years, which was diffusing into the upper water column (Fig. 3). 

It is interesting to note that the highest lability was observed at both ends of the concentration spectrum (i.e., low-DOM marine and high-DOM lake samples), and there are important ecological consequences to this... 

Prometryn also was detected frequently in the Playa Lakes sampling in Texas (Thurman et al., 2000). The degradation product of prometryn, deisopropylprometryn, was detected in nearly every sample that contained prometryn. 

As may be seen from Figure 3, there is considerable difference in the general appearance of these GC-FID traces from the various petroleums. In the Syncrude sample the quantities of dibenzothiophene and monomethyldibenzothiophenes are low and most of the dibenzothiophenes have a >C2 alkyl side chain(s) attached to the ring system. This contrasts sharply with the Bellshill Lake sample where dibenzothiophene, mono- and dimethyldibenzothiophenes dominate the mixture. With... 

Walker Lake. Walker Lake, located in west-central Nevada, is a remnant of pluvial Lake Lahontan, which, at its high stand, had a depth of 280 meters (21). Walker Lake is the terminus of the Walker River. Although its salinity is only 30% that of seawater, its sulfate concentration is identical to that of seawater (0.028 mol/L). The Walker Lake samples represent 300,000 years of depositional history (Yang, unpublished report). Preliminary interpretations of paleontological and mineralogical data (Benson and Spencer, written communication) suggest that lake levels have fluctuated. 

Figure 6. Scatter plots of carbonate-free data from Great Salt Lake samples (squares, freshwater stage circles, saline stage) (a) weight % sulfide sulfur...

A research vessel on Lake Ontario had a slow leak of diesel fuel as it cruised around the lake sampling sediment. Over a few days, this vessel lost 50 gal of diesel fuel. The research scientists on this vessel patched the leak, and then, being a conscientious group, they began to wonder about the environmental ramifications of this spill. They assumed that diesel fuel was composed entirely of n-hexadecane (C16H34), and looking... 

Figure 4 Isotopic compositions versus of precipitation and lake samples from northern Wisconsin...

USA). The precipitation samples define the LMWL (5D = 8.035 0 + 10.95), which is virtually identical to the GMWL. The lake samples plot along an evaporation line with a slope of 5.2 that intersects the LMWL at the eomposition of average local groundwater, with additional data (after Kendall et aL, 1995a). 

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