Sediment sampling devices

Tab. 1 Samples of Havel and Spree river sediments. Sampling devices EB = Eckman-Birge-grab sampler NF = liquid nitrogen deep freeze method.

In the 1990s, Pawliszyn [3] developed a rapid, simple, and solvent-free extraction technique termed solid-phase microextraction. In this technique, a fused-silica fiber is coated with a polymer that allows for fast mass transfer—both in the adsorption and desorption of analytes. SPME coupled with GC/MS has been used to detect explosive residues in seawater and sediments from Hawaii [33]. Various fibers coated with carbowax/divinylbenzene, polydimethylsiloxane/divinylbenzene, and polyacrylate are used. The SPME devices are simply immersed into the water samples. The sediment samples are first sonicated with acetonitrile, evaporated, and reconstituted in water, and then sampled by SPME. The device is then inserted into the injection port of the GC/MS system and the analytes thermally desorbed from the fiber. Various... 

The whole column, apart from a small portion of the sediment, is sam pled in this way. The chemical checks were carried out every 15 days, determining pH, Conductivity, C.O.D., Ammoniacal Nitrogen, Orthophosphate Phosphorus and, furthermore, each month Total phosphorus, Total Kjeldahl Nitrogen, Total Solids and Volatile Solids. The methods utilized are those indicated in the Standard Methods (A.P.H.A., 1980). The amount of matter particles sedimented in the tanks was estimated with the use ol appropriate sampling devices located at the bottom of the tanks and withdrawn after a variable permanence of 40 to 60 days. 

Evaluations of various soil and sediment samplers have been reported [56, 57]. The sediment shovel proved highly practical, but was limited because small particles tend to be lost when the shovel is lifted [56]. A cryogenic sediment sampler was less convenient to use, but allowed the collection of almost undisturbed samples. Houba described a different device for the automatic subsampling of soil, sediment and plant material for proficiency testing [57]. In another study, Thoms showed that freeze-sampling collects representative sediment samples, whereas grab-sampling introduces a bias into the textural composition of the 120 mesh fraction, due to washout and elutriation of the finer fractions [58]. 

Sampling device operated using a boat-mounted winch that allows collection of a relatively undisturbed surface sediment sample. Essentially, a set of "jaws" with a trigger that closes the sampling device on impact. Volume 2(10). 

Slowly lower the sampling device into the water to a desired depth without disturbing the sediment and agitating the water. 

Sampling suspended materials in rivers and lakes is particularly problematic. Not only does the suspended load tend to vary in space and time, but also it is necessary to take care not to introduce systematic error when taking the sample. For example, sampling devices which suck or pump water from depth along pipes can result in substantial loss of suspended materials by sedimentation. It is better therefore to have a sample bottle which may be both opened and then closed at the appropriate depth. 

Four sediment samples were taken in 1998 and 1999 from three locations at the Teltow Canal in Berlin, as indicated in Fig. 1. In addition to the surface sediment samples T1 and T3 taken by means of a 4L Ekman-Birge grab sampler a short sediment core T2 was obtained by using a tube coring device. The sediment core was subdivided into an upper part T2a (0-3 cm) and a lower part T2b (3-10 cm), that represents an older accumulation time between 1980 and 1990. 

Whatever device is used to collect sediment, the device used and its material of construction should be such that contamination of samples is avoided. For example, if corers are used, they should be appropriately precleaned and sealed before use, and sediment grabs used to take a series of samples should be cleaned of any adhering sediment between each sample. 

To collect oil-contaminated soil samples, common tools such as shovels, trowels, scoops, hand-operated auger coring devices are suitable for the top 30 cm. From 30 to 100 cm, one can manually remove the top layer of soil and then use the common tools as described above. For oil deposited on solid surfaces such as wood, rock, and concrete, it can be scrapped off the solid surfaces and placed directly into a sample container. On prolonged weathering at sea, oil tends to form blackish, semisolid tar balls (in diameter of 1 mm to 300 mm). They can be collected by hand and placed into sample containers without difficulty. If freshly spilled oUs or refined products have been absorbed and penetrated into sand or soil, representative oil-contaminated sand or sediment samples from various sites and varying depth should be collected. 

Fig. 3.13 Application of a high-momentum gravity corer (Meischner and Rumohr 1974) to obtain samples from marine sediments. The device can also be stationed on smaller vessels and is suited to extract almost unperturbed cores measuring 1 m in length to be applied in pore water analysis.

Grab samples of this material are usually taken either by hand (shallow water) or by using a small dredge (deep or inaccessible water). A dredge consits of two spring loaded steel jaws. It is lowered by hand using a rope, chain, or cable to the sediment and then the jaws are triggered to close and trap a sample of the sediment. The device must be clean and free of debris from previous samples before use. 

A report from a forensic science laboratory in 1989 described a technique to pyrolyze synthetic polymer samples and simultaneously chemically derivatize (methylate) the pyrolysis products prior to analysis by capillary GC and GC/MS, a technique that was referred to as simultaneous pyrolysis methylation-capillary gas chromatography (SPM-GC) and SPM-GC/MS. The methylation is caused to take place in situ by the simple expedient of adding a few microliters of methanol containing tetramethyl ammonium hydroxide (TMAH) to the sample in the sample holder of the pyrolysis device. When applied to sediment samples for characterization of the organic matter, this technique is referred to as TMAH-Py-GC/MS. The methylation procedure quite likely allows measurement of many compounds that otherwise would pass undetected. Table 7.8 shows a list of compounds that were identified in programs of river and lake sediments subjected to analysis by TMAH-Py-GC/MS. ... 

Sediment samples (10-100 g) are collected using mechanical grabs, coring devices, or vacuum suction. At low tide, samples are obtained by simply scooping the sediment while water divers use hand coring. Special traps are used for collecting newly deposited sedimentary material. 

Chadwick, D. B. Lieberman, S. H. Reimers, C. E. Young, D. An evaluation of contaminant flux rates from sediments ofSincMr Inlet, WA, using a benthic flux sampling device Technical Document 2434 Naval Command, Control and Ocean Surveillance Center, RDT E Division San Diego, CA, 1993. 

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