Sediments, and Rocks

Acid digestions have the advantage that they provide sample solutions with lower dissolved solids contents than fusion methods, and allow removal of silicon as the fluoride by volatilization, thus avoiding the risk of chemical interference from large amounts of silicon. Care is needed when hydrofluoric acid is used with perchloric acid, on both safety and analytical grounds. Hydrofluoric acid causes severe burns if it comes into contact with skin, and any point of 

A Handbook of Silicate Rock Analysis , Blackie and Son, Glasgow, 1987. 

Some laboratories employ operationally defined procedures to extract total elements from soils, such as a one hour reflux with a mixture of boiling nitric and hydrochloric acids. Such an approach may be adequate, for example, to study the build up of elements such as zinc, cadmium, copper, lead, and nickel in sludge-treated soils. However, operationally defined procedures are much more often used to extract the portions of elements present in soils and sediments in a labile or plant-available form. For example, solutions of EDTA or CDTA may be used to extract copper, zinc, manganese, and iron from soils,17 or hydroxylamine hydrochloride may be used to extract easily reducible manganese or manganese oxide-bound trace elements.6 

Sometimes these operationally defined procedures have a sound theoretical basis. For example, it is quite reasonable to suppose that leaching with magnesium nitrate solution will displace zinc from cation exchange sites in soils, or leaching with ammonium acetate will displace exchangeable calcium, magnesium, sodium, and potassium. Flame spectrometry, especially flame AAS, is widely used for the analysis of such extracts. 

---

An experiment on toluene biodegradation under field and laboratory conditions provided results of value in the design of laboratory simulation experiments, and illustrated the caution required in assessing the fate of contaminants. Experiments were carried out under three conditions (i) in flow-through horizontal columns containing sediment and rocks, (ii) in shaking cultures containing sediments, rocks, or plant material, and (iii) in situ in a contaminated stream (Cohen et al. 1995). There were a number of important conclusions ... 

Alien-King R, Grathwohl P, Ball W (2002) New modeling paradigms for the sorption of hydrophobic organic chemicals to heterogeneous carbonaceous matter in soils, sediments, and rocks. Adv Water Resour 25 985-1016... 

The dispersivity of natural sediments and rocks, as we have noted, is a property notable for its tendency to scale strongly with the scale on which it is observed (e.g., Neuman, 1990). Dispersivities observed in field studies, for example, are almost invariably larger than those observed on a smaller scale of study in the... 

Table 4. Se concentration and 6 Se of marine sediments and rocks (Hagiwara 2000).

Seafloor spreading eventually pushes oceanic crust into subduction zones where the hydrothermal sediments and rock are recycled back into the mantle. A small fraction of these deposits is uplifted, or obducted, onto land. These rescued deposits are termed ophiolites. Because of their metal enrichments, they serve as major ore bodies and have been mined for various precious metals, such as copper, for thousands of years. 

Figure 9.48 Correlation of halogen concentration measured in sediments and rock samples by isotope dilution LA-ICP-MS using a high ablation system UNA-Spark n -Atomizer and double-focusing sector-field / -MS Element 2 with the indicative values 59 Samples SRM 2704 (Buffalo River Sediment), SRM 1646 (Estuarine Sediment), Granite GS-N, Bauxite BX-N and Disthene DT-N. (S. Boulyga and K. G. Heumann, Int. ). Mass Spectrom., 242, 291 (2005). Reproduced by permission of Elsevier.)...

The above use of "stable coexisting minerals" is of course based upon the fundamental consideration that the chemical system is "closed" that is, the chemical components K, Si and OH are "inert", their relative proportions, mass, in the system determines the phases formed. This can be assumed valid for many argillaceous sediments and rocks. However, in some geological environments, aqueous solutions containing alkalis and hydrogen ions in various concentrations (whose activities, therefore, are variables but constant throughout a given system) react with kaolinite or other minerals to influence its stability under otherwise constant physical and chemical parameters. 

Initial geochemical analyses indicated that organic matter from these slope sediments differed from previously investigated organic matter (from nearshore Recent sediments, older sediments, and rocks) in three significant respects ... 

Geogenic Naturally occurring. Refers to the contamination of groundwater, soils, sediments, and rocks by natural sources. 

Saturated zone Soils, sediments, and rocks whose pores are entirely filled with groundwater (compare with unsaturated zone and capillary fringe). 

In this chapter, we introduced the reader to some basic principles of solution chemistry with emphasis on the C02-carbonate acid system. An array of equations necessary for making calculations in this system was developed, which emphasized the relationships between concentrations and activity and the bridging concept of activity coefficients. Because most carbonate sediments and rocks are initially deposited in the marine environment and are bathed by seawater or modified seawater solutions for some or much of their history, the carbonic acid system in seawater was discussed in more detail. An example calculation for seawater saturation state was provided to illustrate how such calculations are made, and to prepare the reader, in particular, for material in Chapter 4. We now investigate the relationships between solutions and sedimentary carbonate minerals in Chapters 2 and 3. 

In order to communicate further ideas on sediment diagenesis, it is necessary to consider briefly the sedimentaiy materials that make up carbonate sediments and rocks and classifications of these materials. For detailed discussion the reader is referred to Pettijohn (1957), Folk (1959), Dunham (1962), Ham (1962), and Blatt et al. (1980). 

Chave K.E. (1954b) Aspects of the biogeochemistry of magnesium 2. Calcareous sediments and rocks. J. Geol. 62, 587-599. 

Land L.S. and Hoops G.K. (1973) Sodium in carbonate sediments and rocks A possible index to salinity of diagenetic solutions. J. Sediment. Petrol. 43, 614-617. 

The squeezing method represents an approach where it is possible to modify the pressure during the extraction. This technique has been proved to be effective with various structured materials (coherent sediments and rocks) and has also been used for incoherent materials, including peat, clay, till, sand, silt, chalk and sea sediments (Entwisle and Reeder, 1993), but only recently has been used on soils (Di Bonito, 2005). 

Acidified stored water samples are generally analysed directly, or after filtration through a 0.2 or 0.4 p membrane filter. Particulates on filters are dissolved in a suitable digestion acid mixture, generally following dry ashing to destroy the membrane (see Soils, Sediments, and Rocks , below). 

---