Measuring organic matter

Cindy Lee is a Professor at the Marine Sciences Research Center of Stony Brook University. Dr. Lee s research examines the distribution and behavior of biogenic organic compounds, in particular the rates and mechanisms of transformation reactions occurring as these compounds undergo alteration. Her research investigates organic compounds in the sediments and waters of open ocean and coastal areas, salt marshes, lakes, as well as the atmosphere above these areas. Her expertise centers on the analytical techniques used to measure organic matter in the ocean. Dr. Lee is cur-... 

Loss on ignition measures organic matter, and a single invariant factor (generally 0.58, the van Bremmelen factor) is usually multiplied by the observed organic-matter content to calculate the percentage of carbon in the sample. However, it is known, for example, that this factor is variable and can be as low as 0.45 in the tropics (Burringh, 1984). Uncertainties in this factor will flow directly into uncertainties in the calculated carbon densities. 

Most of the analytical methods that are used to measure organic matter paleoenvironmental proxies are relatively routine, but the procedures are typically not completely uniform among their practitioners. Instead, different groups have developed their individual protocols that are specialized to the instruments available to them, the number of analyses demanded from these instruments and their operators, and the kinds of paleolimnologic questions that are being asked. Because the procedures that are employed to obtain the organic matter parameters are rarely identical, use of sediment standards that have accepted compositions is important to compare analytical results from different laboratories. 

The Development of a Fluorescence Index to Measure Organic Matter Humification Preserved in Cave Stalagmites and Create Long-Term Records... 

SW-846, is used to measure emissions of semivolatile principal organic constituents. Method 0010 is designed to determine destruction and removal efficiency (DRE) of POHCs from incineration systems. The method involves a modification of the EPA Method 5 sampling train and may be used to determine particulate emission rates from stationary sources. The method is applied to semivolatile compounds, including polychlorinated biphenyls (PCBs), chlorinated dibenzodioxins and dibenzofurans, polycyclic organic matter, and other semivolatile organic compounds. 

Refuse tips invariably result in the production of methane from the decay of organic matter. Measures are necessary to avoid trapping the methane in or beneath the building. This can be achieved by a system of methane vent pipes in the fill together with an impermeable membrane at sub-ground-floor level. Alternatively, a vented cavity can be constmcted sub-ground floor. 

The major chemical problem met in ion-exchange practice is the fouling or poisoning of the anion resins by organic matter. The various counter measures deployed include pre-flocculation, oxidation of the organic material, the use of specially developed resins, and treatment of the fouled resins by brine and/or hypochlorite. 

As shown in Fig. 10-13, there is also a flux of O2 produced during net photosynthesis from the ocean to the atmosphere and an export flux of particulate and dissolved organic matter out of the euphotic zone. For a steady-state system, new production should equal the flux of O2 to the atmosphere and the export of organic carbon (Eppley and Peterson, 1979) (when all are expressed in the same units, e.g., moles of carbon). Such an ideal state probably rarely exists because the euphotic zone is a dynamic place. Unfortunately, there have been no studies where all three fluxes were measured at the same time. Part of the difficulty is that each flux needs to be integrated over different time scales. The oxygen flux approach has been applied in the subarctic north Pacific (Emerson et al, 1991) and subtropical Pacific (Emerson et al, 1995, 1997) and Atlantic (Jenkins and Goldman, 1985). The organic carbon export approach has... 

Despite Lavoisier s early work on the link between energy and life, calorimetric measurements played a relatively minor role in biology until recent years, primarily because of practical obstacles. Every organism must take in and give off matter as part of its normal function, and it is very difficult to make accurate heat-flow measurements when matter is transferred. Moreover, the sizes of many organisms are poorly matched to the sizes of calorimeters. Although a chemist can adjust the amount of a substance on which to carry out calorimetry, a biologist often cannot. 

The quantification of gross root production, rhizodeposition, microbial assimilation, and the production of organic materials in soil has made increasing progress ever since stable ( C) and radioactive ( C) carbon isotopes have been used (see Chap. 12). Measurements of soil organic matter dynamics without these isotopes are difficult due to the large amount present as compared to the smaller rates of input. 

W. Cheng, Measurement of rhizosphere respiration and organic matter decomposition using natural C, Plant Soil /84 263 (1996). 

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