Particulate fraction

Filtration. Except for the in situ pumps, large-volume filtration has to be performed on board, for which a variety of pressure or suction techniques is available (compare with Chapter 2 and Chapter 12, Section 12.6). In order to prevent the loss of any particulate or dissolved activity, the risk of settling of particles and adsorption/adhesion to walls of the sampling bottles has to be considered. If a water pump is used before the filter, it should be carefully checked, e.g., by microscopy, whether the pump leaves the particles intact. Centrifugal pumps are notoriously harmful to plankton. An elegant filtration method has been described by Dehairs et al. (1997). A 30L calibrated Perspex cylinder with a conical bottom is filled with the sample obtained from a Rosette cast. The outlet is connected to a 142 mm Teflon filtration unit. Controlled (50-100 kPa) air pressure is applied to a series of these units from a simple small compressor. 

Ultra filtration. There is increasing interest in the measurement of radionuclides in colloids, especially since it has been suggested that particle-reactive nuclides such as Th can be used as in situ coagulometers (Honeyman and Santschi, 1989). These measurements are beyond the scope of this chapter the reader is referred to Baskaran et al, 1992, Moran and Buesseler, 1993, and to an intercalibration conducted by Buesseler et al (1996). 

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Micro-mesh sieves have been applied to the determination of solid propint ingredients (Refs 17 35) and similar materials where sieve analyses are required with great accuracy in the very fine range. They are also applicable to specific problems such as the analysis of magnetic powders, and of powders consisting of mixts of substances of different specific gravities or the preparation of clearly defined particulate fractions in a short time... 

DBH is a monooxygenase and uses ascorbate as an electron donor, copper at the active site, and fiimarate as modulator. DBfl is in the particulate fraction of the medullary cells, probably in the secretion granule thus. 

We synthesized H-okadaic acid chemically and demonstrated its specific binding to the particulate and cytosolic fractions of mouse skin. The specific binding of H-okadaic acid to the particulate fraction was not inhibited by TP A, lyngbyatoxin... 

Mitcham, E.J., Gross, K.C., and Wasserman, B.P. (1991) Synthesis of uridinediphospho-[U- C]-D-galacturonic acid by enzyme particulate fractions and purification via high performance liquid chromatography. Phytochem.Anal. 2 112-115. 

The values of kj calculated by Bacon and Anderson (1982), and used in most models of Th scavenging, varied with particle concentration and ranged from 0.2 to 1.2 Such values are appreciably longer than expected from sorption rates onto particle surfaces. The discrepancy can be explained if dissolved Th is initially sorbed to surfaces of very small particles (colloids) that pass through the typical filters (0.1-0.4 im) used to separate dissolved from particulate fractions (Santschi et al. 1986). 

Determination of the POC/ Th ratio on sinking particles. Application of Equation (9) requires knowledge of the POC/ Th ratio on sinking particles. As noted above, this has often been taken as the POC/ Th ratio in the large-size particulate fraction, with the assumption that this fraction is more likely to be sinking. 

An additional bacterial component displaying appreciable adjuvanticity is the C. granulosum-derived p40 particulate fraction. p40 is composed of fragments of cell wall peptidoglycan and... 

The biodegradability within a period of time corresponding to the residence time in a sewer network (typically between a few hours and one day) must be reasonably detailed. Therefore, the fast biodegradable fractions considered as Ss and fast hydrolyzable substrate must be included as separate fractions. On the contrary, what is not biodegradable within 1-2 days is of minor interest. As a consequence, there is no need to distinguish between a rather slowly biodegradable, particulate fraction of a substrate and a fraction that is inert, whatever it is — soluble or particulate. 

For practical purposes, the distinction between dissolved organic carbon and particulate organic carbon is that the latter is retained on filters of known porosity. Membrane filters with 0.25-1. Oum pore size and glass fibre Whatman G F/C filters are commonly used. By using the particulate fraction of a sample retained on pre-combusted Whatman G F/C filters for... 

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