Carbon losses from soils

BROADBENT F.E. 1947. Nitrogen release and carbon loss from soil organic matter during decomposition of added plant residues. Proceedings of the Soil Science Society of America, 12, 246-249. 

J. K. Martin and J. R. Kemp, Carbon loss from roots of wheat cultivars. Soil Biology and Biochemistry /2 551 (1980). 

Bellamy, P. H. (2005). Carbon losses from all soils across England and Wales 1978-2003. Nature 437(7056), 245-248. 

In general, the vapor pressure of carbamates is low, but some may sublimate slowly at room temperature, and this would appear to explain their loss from soil surfaces. As the distribution in air is considered to be minor, the aquatic media is an important transport route for the very soluble carbamates. In this case, the hazard is limited by thefr rapid decomposition under aqueous conditions. Carbamates are hydrolyzed spontaneously yielding, as final products, an amine, carbon dioxide, and an alcohol or phenol ... 

Soil reaction (pH) The relationship between the environment and development of acid or alkaline conditions in soil has been discussed with respect to formation of soils from the parent rock materials. Soil acidity comes in part by the formation of carbonic acid from carbon dioxide of biological origin and water. Other acidic development may come from acid residues of weathering, shifts in mineral types, loss of alkaline or basic earth elements by leaching, formation of organic or inorganic acids by microbial activity, plant root secretions, and man-made pollution of the soil, especially by industrial wastes. 

Loss of carbon compounds from roo(s, or rhizodeposition, is the driving force for the development of enhanced microbial populations in the rhizosphere in comparison with the bulk soil. Although rhizodeposition is a general phenomenon of plant roots, the compounds lost from different species or even cultivars can vary markedly in quality and quantity over time and space. 

The loss of carbon compounds from roots can influence microbial populations in various ways. Since the presence of readily available carbon sources is thought to be the most limiting factor to microbial growth in soil (96), rhizodeposition acts at a gross level to stimulate microbial populations. This generates the rhizo-sphere effect (97), where the number of microorganisms in the rhizosphere (R)... 

For solids run-off it is assumed that this run-off water contains 200 parts per million by volume of solids thus the corresponding velocity term U12 is 200 x 10 6t Jn, i.e., 10 s m/h. This corresponds to the loss of soil at a rate of about 0.1 mm per year. If these solids were completely deposited in the aquatic environment (which is about l/10th the soil area), they would accumulate at about 0.1 cm per year, which is about a factor of four less than the deposition rate to sediments. The implication is that most of this deposition is of naturally generated organic carbon and from sources such as bank erosion. 

HBEF, much of the lead entering the ecosystem from the atmosphere appears to be retained in the forest floor. Concentrations and fluxes of lead in bulk deposition are much greater than in Oa horizon leachate. Solution concentrations and fluxes of Pb decrease through the soil profile and losses in stream water are low. There was a strong correlation between concentrations of Pb and dissolved organic carbon (DOC) in soil solution and stream water at Hubbard Brook Driscoll et al., 1994, 1998). 

Carbon dioxide is the most common inorganic extractant used for the extraction of organic compounds in soil. Under pressure, it remains in the liquid state and can be used to extract organic compounds from soil. When the pressure is released, the carbon dioxide becomes a gas and is thus removed from the extracted components. An additional benefit is that liquid carbon dioxide is converted to gas at relatively low temperatures, thus limiting the loss of... 

Hewitt found that volatile organic compounds are readily lost from soil samples unless care is taken to limit surface area exposure and to ensure subsample isolation [338]. Volatile organic carbon losses were found to be most abundant during field collection and storage. Hewitt reported that fortified soils held in sealed glass ampoules at 4 °C, or dispersed in methanol and held at 22 °C, showed no significant losses over 20 and 98 days, respectively [339]. 

None of the pure cultures that produced HFBT have been shown to further metabolize this compound. Bohonos et al. (46) found two further oxidation products, 3-hydroxybenzothiophene and 2,3-dihydrobenzothiophene-2,3-dione in aerobic mixed cultures co-metabolizing dibenzothiophene. Recently, Mormile and Atlas (61) inoculated portions of the filter-sterilized supernatant from a dibenzothiophene-degrading culture with soil and sediment samples and observed the loss of HFBT using a spectroscopic method. Under their aerobic growth conditions, they also observed the release of carbon dioxide from these cultures indicating that these products of dibenzothiophene degradation can be further oxidized. In addition, they observed carbon dioxide production from dibenzothiophene-sulfoxide. 

In water logged soils radial oxygen loss from the root raises the redox potential in the rhizosphere as a consequence of which iron oxide plaques are seen to develop on root surfaces. Bacha and Hossner (1977) removed the coatings on rice roots growing under anaerobic conditions. The coatings were composed primarily of the iron oxide mineral lepidocrocite (y-FeOOH) as the only crystalline component. St-Cyr and Crowder (1990) studied the iron oxide plaque on roots of Phragmites and detected both Fe and Mn. The Fe Mn ratio of the plaque resembled the ratio of Fe Mn in substrate carbonates. The plaque material also contained Cu. 

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