Sample storage sediments

The devices used for sampling of solid samples (sludge, sediment, and soil) are usually grab samplers or corers. Box corers or multicorers can be employed if more detailed information on the spatial distribution of the analytes is needed. The samples are stored in the dark at 4 °C or more commonly at -20 °C, preferably in glass containers [53]. Very often, solid samples are also dried or lyophilized prior to storage. 

Thomson, E.A., Luoma, S.N., Cain, D.J. and Johansson, C. (1980) The effect of sample storage on the extraction of Cu, Zn, Fe, Mn and organic materials from oxidized estuarine sediments. Water Air Soil Pollute 14, 215. 

In analysis of marine samples by AAS problems are encountered in sampling procedure, sample storage, sample treatment and measurement procedures. Analytical difficulties arise from the low concentration of most elements and complex matrices in marine samples. In this chapter, a general discussion on marine analysis by AAS will be provided in terms of seawater, marine organisms and sediments. 

As previously outlined in the Sampling section, sediments and soils were prehomogenized on-site by subdividing the samples into different sub-samples (which will be similar, but not identical) in order to minimize the possible risk of contamination. Some of these specimens will be accurately homogenized at the BCAA in Italy and delivered to laboratories on request for valid comparison of data and analytical techniques and for the evaluation of the stability of specimens during storage (34, 35). 

An important consideration prior to sample collection is transportation and storage. Samples should be treated so as to retain the integrity of the sample from the moment of collection to the time of analysis. The physico-chemical characteristics of a sediment sample change during drying, with effects on the sorption-desorption behavior of chemicals. 

Standard analytical techniques for sampling and pretreatment and analytical requirements for sediment studies are less available than for water and soil studies. To obtain meaningful results from laboratory experiments, the sediment samples should be kept in the original aqueous matrix, and analyses should be carried out immediately to minimize changes to the sample matrix due to chemical and biological processes that could occur during storage. 

Monsanto. 1981. Stability study of natural sediments samples preserved by frozen storage with attachment. Monsanto Company, St. Louis, MO. 

In this case, a likely explanation for the apparent supersaturation is that the chemical analysis included not only dissolved aluminum and iron, but also a certain amount of aluminum and iron suspended in the water as colloids and fine sediments. Analytical error of this type occurs because the standard sampling procedure calls for passing the sample through a rather coarse filter of 0.45 tun p0re size and then adding acid to preserve it during transport and storage. 

Rossmann R. 1988. Estimation of trace metal storage in Lake St. Clair post-settlement sediments using composite samples. J Great Lakes Res 14 66-75. 

Bordas, F. and Bourg, A.C.M. (1998) A critical evaluation of sample pretreatment for storage of contaminated sediments to be investigated for the potential mobility of their heavy metal load. Water Air Soil Pollut., 103, 137. 

Uncontrolled species transformations during analysis form another source of error. For methylmercury determinations in sediments it was demonstrated that errors of up to 80% resulted from the formation of the compound from inorganic mercury during separation and analysis [28, 29], For the study of possible species transformations during analysis multiple isotope dilution could be used as a diagnostic tool for identifying the error and bias inherent in specific methods of storage, sample preparation and measurement [30, 31]. 

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