Sediment trap sampling techniques

Figure 1. Box model for the calculation of Mn redox cycling near the sediment-water interface. Sedimentation rates are measured with sediment traps. The burial rate Sh is estimated from dated sediment cores. In situ sampling techniques (flux chambers and peepers) are used to quantify the diffusive flux across the sediment-water interface FS6. The resuspension rate R is estimated from the increase in the mass flux of settling material between the 81- and 86-m horizons.

Oxidation Rate of Mn near the Sediment-Water Interface. We used a box model approach to calculate rates of the Mn redox cycle from sediment-trap data and in situ sampling techniques (peeper and lander experiments). Figure 1 depicts an overview of the relevant processes and length scales. Sedimentation rates of particles were determined with sediment traps at 81 time intervals of about 2 weeks during 1988-1991 and at three depths (z = 20, 81, and 86 m). 

Trace elements in leachates and digests of loaded filters, sediment traps and centrifuge materials can be detected using different atomic absorption spectrometric techniques. Depending on the amount of available sample solution and concentration of the respective elements either common flame, flame-injection or electrothermal AAS (ETAAS) are selected. The principle of atomic absorption spectrometry, its advantages and limitations have... 

Samples from sediment traps subsampled by wet splitting techniques (e.g., v. Bodungen et al., 1991), should be filtered as described above. Flushing at the end of filtration is important. 

Figure 15-12 is a schematic illustration of a technique known as acid volatile sulfides/ simultaneously extracted metals analysis (AVS/SEM). Briefly, a strong acid is added to a sediment sample to release the sediment-associated sulfides, acid volatile sulfides, which are analyzed by a cold-acid purge-and-trap technique (e.g., Allen et ai, 1993). The assumption shown in Fig. 15-12 is that the sulfides are present in the sediments in the form of either FeS or MeS (a metal sulfide). In a parallel analysis, metals simultaneously released with the sulfides (the simultaneously extracted metals) are also quantified, for example, by graphite furnace atomic absorption spectrometry. Metals released during the acid attack are considered to be associated with the phases operationally defined as "exchangeable," "carbonate," "Fe and Mn oxides," "FeS," and "MeS."... 

Dynamic headspace-extraction stripping and purge-and-trap methodology are used most often for determination of M-hcxanc in water and hazardous wastes. Dynamic headspace extraction techniques have been applied to water samples (Roberts and Burton 1994) and sediment (Bianchi et al. 1991). Detection limits of 0.5 g/L were reported for lake water (Roberts and Burton 1994) and 20 ng/kg (ppt) for sediment (Bianchi et al. 1991). Supercritical fluid extraction (SFE) is a relatively new technique that has been applied to -hcxane in soil (Yang et al. 1995). Membrane extraction of M-hexane from water samples has been developed to provide online, continuous monitoring (Wong et al. 1995 Xu and Mitra... 

As analytical capabilities improve, multiple procedures are linked together in series to effect analyses. Procedures combined in this manner are called hyphenated techniques. Ferrer and Furlong [124] combined multiple techniques—accelerated solvent extraction (ASE) followed by online SPE coupled to ion trap HPLC/MS/MS—to determine benzalkonium chlorides in sediment samples. Online SPE, especially coupled to HPLC, is being used more routinely. This approach allowed online cleanup of the ASE extract prior to introduction to the analytical column. 

Propyn-l-ol is analyzed by GC-FID using a suitable column for alcohol. It can be analyzed in all types of samples, such as ground-water or soils, sediments, and sludges by GC/MS using a purge and trap technique or by direct injection (U.S. ERA 1986, Method 8240, SW-846). A column containing 1% SP-1000 on Carbopack-B is suitable. The primary ion is 55 and the secondary ions are 39, 38, and 53 (electron-impact ionization). 

A GC/ion trap MS method was used for the trace analysis of atrazine and its deethylated degradation product deethylatrazine in environmental water and sediment samples. The isotope dilution technique was applied for the quantitative analysis of atrazine at parts-per-trillion levels <2003ANA263>. 

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