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Techniques

Techniques

Physical Techniques & Protocols

Laser Particle Size Analysis - This technique is carried out in the Malvern Room with the use of a Malvern Mastersizer 2000. The Malvern Mastersizer 2000 is a laser particle sizer used to measure the particle size distribution of soils and sediments. It allows for the measurement of particles ranging from 0.02µm to 2mm. The Mastersizer is connected to a personal computer, on which the particle size data can be displayed in both table and graph form. The data can also be exported to Excel spreadsheets for more sophisticated analyses.

Loss On Ignition - This technique may be used to measure %water, bulk density, % charcoal, %organic, % calcium carbonate and % silicate residue in a variety of soils and sediments. The 105°C oven is used to dry the samples, while the muffle furnace is employed at 400°C, 480°C, 550°C and 950°C to remove organic matter and break down carbonate respectively. Electronic balances (2 and 3 dp) are routinely used to determine the loss in mass at various stages of the analysis. However, analytical balances are available for work with very small samples.

Magnetic Susceptibilty - The Bartington Magnetic Susceptibility Meters are used to measure the magnetic susceptibility of a variety of soils and sediments. Magentic susceptibility depends on the amount, type and particle size of the ferro-magnetic minerals present. The meter may be used with a scanning loop to measure cores of sediment, or with a well-type sensor for discrete samples. One of these meters is connected to a personal computer, and data can be exported to Excel spreadsheets for detailed analysis.

Analytical Balances - The laboratories has one extremely accurate balance (4 dp), which reads down to ten thousandths of a gram. It is connected to a personal computer, and can download data directly onto Excel spreadsheets. This brings the advantages of speed, accuracy, precision, and the ability to handle a large volume of data.

Sieving, Pulverising and Milling - The Soils and Sediments Laboratory houses a variety of sieves ranging from large diameter gravel sieves with metal meshes up to 36mm to small nylon sieves with apertures of only 5µm. Although the sieves can be used for particle size analysis, they are usually employed for separating plant and animal fossils, pebbles, or other material for subsequent analysis. The laboratories have several sieve shakers which can be used for either wet or dry sieving of soils and sediments. The pulveriser and ball mill are used to comminute soils and sediments prior to various physical and chemical analyses.

Hydraulics - The Soils and Sediments Laboratory houses an Armfield Engineering Tilting Flume which is used to simulate the flow dynamics of rivers. The gradient, discharge, depth and bed type can all be varied with relative ease. The flume also has a wave generator, which can produce pulses of varying frequency and amplitude to mimic lacustrine and shallow marine conditions.

Palaeontological Techniques & Protocols

Pollen Preparation of Fossil Pollen and Pollen Analysis - The Quaternary Palaeoenvironments Group studies fossil pollen assemblages from terrestrial and marine sediments, which are used to determine changes in past vegetation and climate. Fossil pollen preparation is carried out in the Preparation Rooms, which are fitted with special fume cupboards. The procedure involves treating sediment with hydrofluoric acid (HF) to remove silicate minerals, whilst leaving the fossil pollen intact. Prepared pollen samples are counted using high power light microscopes in the Microscope Rooms. An excellent reference collection of modern pollen for comparison is also maintained. A pollen preparation sheet and pollen count data sheet are available.

Pollen Preparation for Modern Reference Pollen - This protocol details how to make slides of modern pollen from flowering plants for reference use in pollen analysis. Pollen reference slides made from specimens collected in the field or acquired through a botanic garden are a valuable aid in the identification of fossil pollen, and are especially important when working in a region for which the flora is poorly represented in an existing reference collection.

Dinoflagellate Cyst Preparation - This protocol details how to prepare samples and make slides for dinoflagellate cyst analysis.

Environmental Chemistry Techniques & Protocols

Wet Chemistry - The wet chemistry used to dissolve samples into a suitable medium for ICP, atomic absorption and UV-visible spectrophotometry is an important part of the analytical process. Standard wet chemical techniques for analysis of chloride, total and calcium hardness and alkalinity are available. The Teccator block digestor is used for the acid digestion of soils.

ICP-OES - Inductively Coupled Plasma - Optical Emission Spectra. A Perkin-Elmer ICP-OES analyser is available for multi-element analysis down to parts per billion. The machine uses an ICP source to dissociate samples into their constituent atoms or ions, exciting them to a level where they emit light of a characteristic wavelength. Up to 60 elements can be screened per single sample. The set-up and calibration time required for the analysis of a large number of elements is considerable, although the run-time for each sample can be quite short.

pH, Ion Sensitive Electrodes and Electrical Conductivity - pH is the negative logarithm of the hydrogen ion concentration of a solution. A probe is introduced into the solution to be measured, which gives a read-out on a meter. Ion Sensitive Electrodes work in a similar way and are used to measure the concentration of ions such as nitrate and chloride. Electrical Conductivity is a measure of the total ionic solutes. It provides a useful measure of ionic strength, but does not identify which ions are present.

Nitrate - Ion Sensitive Electrodes are used to measure the concentration of ions such as nitrate.

Flame Emission Spectrophotometry - This technique is used to measure exchangeable cations, such as calcium, sodium and potassium. Spectrophotometry measures the emission of photons as electrons of a specific element are excited to higher orbitals and drop back to the ground state.

Potassium - Flame Emission Spectrophotometry techniques is used to measure exchangeable cations, such as calcium, sodium and potassium.

UV-visible spectrophotometry - This technique is mostly used to determine phosphate concentrations down to parts per million. In this case, the absorption of light at a specific wavelength as it passes through an aqueous solution is measured.

Phosphate - Using UV-visible spectrophotometry phosphate concentrations can be determind. In this case, by the absorption of light at a specific wavelength as it passes through an aqueous solution is measured.