Changes In Total Carbon Research Articles

Soil carbon fractions based on their degree of oxidation, and the development of a carbon management index for agricultural systems

Increasing population pressure is increasing the demand on agricultural systems in many parts of the world and this has often led to the degradation of the soil resource. Soil carbon (C) is a major determinant of sustainability of agricultural systems and changes can occur in both total and active, or labile, C pools. A procedure is presented to determine the degree of lability of soil C. By treating a ground sample of soil with 333 mM potassium permanganate (KMnO4) to oxidize a proportion of the carbon and by determining the total carbon by combustion, two fractions of C can be measured. These fractions represent carbon of different lability, with fraction I representing the Labile C (CL), which is oxidized by 333 mM KMnO4, and fraction I1 representing the non-labile C (CNL), which is not oxidized by 333 mM KMnO4. On the basis of changes in total carbon (CT), a Carbon Pool Index (CPI) is calculated and, on the basis of changes in the proportion of labile C in the soil between a reference site and those subjected to agricultural practice or research treatments, a Lability Index (LI) is determined. These two indices are used to calculate a Carbon Management Index (CMI), with CMI = C Pool Index (CPI) xLability Index (LI) x 100. Analyses of paired samples (cropped and uncropped) from three sites in northern and central New South Wales, Australia, have shown a decline in CPI, a greater decline in LI and hence a decline in the CMI with cropping. Introduction of a legume into a wheat cropping system restored the CMI from 22 to 37 at the Warialda site. Analyses of paired samples from a sugarcane area in north Queensland have shown a decline in CMI in systems dominated by trash burning, but an increase in CMI in systems dominated by green cane trash management. Similar data from Brazil showed no increase in CT with mulching but a 48% increase in CMI due to an increase in the lability of C in the soil. The fractionation procedure and CMI outlined can be used to determine the state and rate of change in soil C of agricultural and natural systems.

Shoreline, Grain-Size, and Total-Carbon Distribution Changes Before and After Hurricane Alicia, Galveston Island, Texas, 1983: ABSTRACT

Shoreline, grain-size, and sediment total-carbon changes were monitored, on a monthly basis, on three Galveston Island beaches, from January through December 1983. The study area included: (1) East Beach, obstructed by groins and a seawall; (2) Galveston Island State Park, obstructed by fences artificially stabilizing the dunes; and (3) West Beach, an unobstructed beach. Beach profiles revealed the effects of beach obstruction, such as erosion and undercutting at East Beach, and truncation of the dunes at Galveston Island State Park. Approximately 20 m of expansional cutback occurred on the beaches after Hurricane Alicia hit on August 18, 1983. Contour maps of grain-size and total-carbon distributions reflect the movement of beach sand by either onshore-offshore transport during low-energy periods, or longshore, edge-wave transport during high-energy periods. Statistical analyses revealed a small variation in grain size throughout the year. There were well-defined times of either no correlation or strong correlation between total carbon vs. mean grain size, skewness vs. mean grain size, kurtosis vs. mean grain size, total carbon vs. percent sand, total carbon vs. skewness, and skewness vs. kurtosis. Strong correlation was found in response to high-energy events, whereas no correlation was found in response to low-energy events. Galveston Island is undergoing net erosion and appears to be in a metastable state, still capable of responding to oceanographic conditions. The economic effects of Hurricane Alicia include considerable loss of the shoreline and destruction of property. Beach nourishment appears to be the only economically feasible solution to counteract the extensive erosion. End_of_Article - Last_Page 303------------

The simultaneous use of tracers for ocean circulation studies

A method for the simultaneous use of tracers for oceanic circulation studies is developed. To permit the inclusion of tracers that are subject to biochemical transformation a simple model for photosynthesis, bacterial decomposition and chemical dissolution is formulated based on the use of Redfield ratios for the chemical compounds interaction. The finite difference analogue to the steady state tracer continuity equation, applied to the tracers chosen, leads to a set of simultaneous algebraic equations that in principle can be solved by matrix inversion methods. Two cases are considered: (1) The problem is indeterminate, which may be the case when too few tracers are available and/or some tracer equations are redundant. A solution is obtained by minimizing the transport vector; (2) The problem is incompatible, which may result from making use of many tracers. A solution is obtained by minimizing the errors in satisfying the tracer continuity equations. The method is applied to a 12-box model of the world oceans by considering the surface water, intermediate water, deep water and bottom water of the Arctic, Atlantic, Antarctic and Pacifichndian Oceans (with some simplification for the polar seas). Total dissolved inorganic carbon, alkalinity, phosphorus, oxygen and radiocarbon are used as tracers. A series of steady state solutions are presented and the uncertainties as dependant on box configuration and erroneous or nonrepresentative data are analysed. In the reference solution, circulation cells emerge where Antarctic surface water penetrates into intermediate levels of the two major oceans, from where it undergoes lifting and, at the surface, advection back towards the south. In the Atlantic, much of the penetrating water reaches as far north as to involve the Arctic deep water, which sinks and moves towards the deep Antarctic Ocean through the deep Atlantic. The total upwelling in the Antarctic Ocean is about 30 Sv. Turbulent exchange prevails between surface and intermediate waters in both major oceans with an average K, of about 1 cm 2 s -1 . Particular consideration is given to the transfer of carbon by computing the changes in total carbon and radiocarbon that are induced by fossil fuel combustion and nuclear bomb testing by using the steady state circulation and turbulent transfer deduced. It is concluded that better spatial resolution is required to determine the role of the ocean as a sink for injections of carbon and radiocarbon. DOI: 10.1111/j.1600-0889.1983.tb00025.x

A comparison of the organic matter, biomass, adenosine triphosphate and mineralizable nitrogen contents of ploughed and direct-drilled soils

SUMMARYSoil samples were taken from four field experiments on the growth of cereals in direct-drilled and in mouldboard-ploughed soil. When sampled, one of the experiments had run for 5 years, one for 6, one for 8 and one for 10 years. Sampling was to just below plough depth and was done on an ‘equivalent depth’ basis, i.e. the more compact direct-drilled plots were sampled more shallowly than the ploughed plots in such a way that both samples represented the same weight of soil per unit area. No significant differences in total nitrogen or in total organic carbon were observed between cultivation treatments at any of the four sites.In three of the four sites, there was no significant difference in microbial biomass carbon, adenosine 5'-triphosphate (ATP), or mineralizable nitrogen between directdrilled and ploughed soils. In the fourth, which contained more clay than the others, there was slightly more biomass carbon and ATP in the direct-drilled soil. As microbial biomass carbon (or ATP, which is closely correlated with microbial biomass carbon) responds more rapidly to changes in management than do total carbon and nitrogen, a change in biomass carbon should provide early warning of changes in soil organic matter, long before changes in total carbon and nitrogen become measurable. That no such change was observed, with one partial exception, is evidence that a change from traditional methods of cultivation to direct drilling has little effect on soil organic matter other than altering its distribution in the soil profile.

Energy, total carbon, and oxygen demand

The biodegradable content of organics in aqueous solution can be assessed in two ways: by measuring the change in organic content effected by bacterial metabolism; or by measuring the consumption of oxygen by bacteria in effecting the removal of organics. In addition to oxygen, two possible parameters for pollution measurement are thermodynamic energy change and total carbon change. The validity of applying thermodynamic concepts to biological systems is questioned. Total carbon changes during the process of biological oxidation are considered to offer an excellent potential as a measure of biodegradable organic content. The use of carbon as a parameter in the context of the two analytical procedures derived at Rice University affords a flexibility in selection of technique based on the required precision of results. (Key words: Pollution measurement; oxygen demand; bacterial synthesis.)

The Effect of Changes in Total Carbon and in the Condition of Carbides on the Magnetic Properties of Steel

The Effect of Changes in Total Carbon and in the Condition of Carbides on the Magnetic Properties of Steel