Calcium carbonate content

The actual figure is, however, of value only in relation to calcium carbonate content and for calculation of alkali additions for pH corrections. A graphical form is included in the Langelier diagram ... 

The calcium carbonate content of surfece sediments is not a very sensitive indicator of the degree of PIC dissolution. Thus, a significant percentage of the sinking PIC must dissolve before an appreciable impact is seen in the %CaC03 of the surfece... 

Lysocline The depth at which shell dissolution starts to have a detectable impact on the calcium carbonate content of the surface sediments. 

The distribution of calcium carbonate in sediments with ocean depth shows wide variations. In open ocean basins, where rates of detrital sedimentation are moderate to low, sediments above 3000 meters water depth are generally high in calcium carbonate, whereas sediments below 6000 meters generally have very low calcium carbonate content. Between these depths there is a poor correlation between the weight % calcium carbonate and depth (Smith et al., 1968). Turekian... 

Figure 4.15. A plot of weight % calcium carbonate versus percent original calcium carbonate dissolved. For sediments of high initial calcium carbonate content, little change in weight % takes place until approximately 50 percent of the carbonate has dissolved. Small variations in initial calcium carbonate concentration can lead to large variations in calcium carbonate concentration at high dissolution values. (After Morse, 1973.)...

One major paper attacking the problem of the relationship between the preservation of calcium carbonate in shallow anoxic marine sediments and their chemistry was by Aller (1982). The study was conducted at sites in Long Island Sound. The calcium carbonate content of the sediments decreased with increasing water depth. At the shallow FOAM (Friends of Anaerobic Muds) site shell layers associated with storms resulted in irregular variations in the carbonate content of the sediment. Ca2+ loss from the pore waters, indicative of calcium carbonate precipitation, was found only at the FOAM site below -20 cm depth. During the winter, elevated Ca2+ to CL ratios were observed near the sediment-water interface... 

In soils, F can be found in four major fractions (1) dissolved in soil solution (2) sorbed to Al, Fe, and Mn oxides and hydroxides and carbonates (3) solid phases, such as fluorite and fluorophlogopite and (4) associated with organic compounds. The solubility of F in soil solution is variable and is affected by pH, speciation, adsorption and desorption reactions, and dissolution and precipitation reactions (Luther et al., 1996). Acidic conditions and low calcium carbonate content are favorable to F solubility and can therefore enhance both root uptake (Weinstein and Alscher-Herman, 1982) and migration to surface and ground water (Smith, 1983). These conditions can lead to human, plant, and animal health issues. Soils that do contain appreciable amounts of calcium carbonate and are neutral to slightly alkaline conditions can fix F as insoluble calcium fluoride (CaF2), and reduce its bioavailability and mobility (Kubota et al., 1982 Tracy et al., 1984 Reddy et al., 1993 Poulsen and Dudas, 1998). 

The carbonate compensation depth (CCD) occurs where the rate of calcium carbonate dissolution is balanced by the rate of infall, and the calcium carbonate content of surface sediments is close to Owt.% (e.g., Bramlette, 1961). The CCD has been confused with the calcium carbonate critical depth (sometimes used interchangeably with the lysocline discussed next), where the carbonate content of the surface sediment drops below 10 wt.%. A similar marker level in deep-sea sediments is the ACD, below... 

Pitty, A.F. (1968) Calcium carbonate content of karst water in relation to flowthrough time. Nature 217, 939-940. 

Figure 19.31 Tensile strength, elongation and impact strength of PVC containing 20 phr CPE vs. calcium carbonate content. [Data from Ventresca D A, Berard M T, Antec 97. Conference proceedings, Toronto, April 1997, 3574-9.]...

Laser granulometry indicated little variation in the particle size with depth in the trench section, the median size being 12-15 pm. On average the bulk sediments were found to contain approximately 20% clay ( < 2 pm), 70% silt (2-63 pm) and < 10% sand ( > 63 pm). Bulk sediment XRF analyses also showed that the major element proportions are also relatively constant with depth (Figure 7.7). X-ray diffraction (XRD) analyses showed some variability in the relative proportions of clay minerals present in the < 2 pm fraction, but all samples were dominated by illite, smectite, kaolinite and chlorite. The calcium carbonate content was low ( < 1%), much of the detrital material apparently having been dissolved. The sediment pH ranged from 6.2 to 6.7. 

Frey, R.W. Pinet, P.R. (1978) Calcium-carbonate content of surhcial sands seaward of Altamaha and Doboy Sounds, Georgia. J. sediment. Petrol., 48, 1249-1256. 

Figure 11.6 Dependence of yield stress and Young s modulus on calcium carbonate content. (From Reference 34 with permission from The Society of Plastics Engineers.)...

The material was collected at San Pellegrino Parmense (Italy) in February 1994, following a prospective study of various sites in Italy which aimed at identifying a material with reasonably high calcium carbonate content. Stones... 

Alkalinity and buffer capacity Dissociation of ammonium ions to ammonia results in the production of hydrogen ions. Unless the water column or soils are well buffered, the medium can be acidified and the rate of ammonia volatilization can decrease. Thus, a water column with high alkalinity and calcium carbonate content can buffer the system and maintain high-pH conditions. Alkalinity is affected by the balance between photosynthesis and respiration by algae and submersed macrophytes in the water column. Ammonia volatilization losses are directly proportional to the alkalinity of the system. 

A second attempt (run NITAC-S) was based on more aggressive process conditions. In order to reduce the buffer capacity of sediment, the 500 pm oversize fraction, which had high calcium carbonate content due to the presence of numerous shells fragments, was preliminarily removed through sieving. This fraction accounted... 

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