Formation And Development of Vertisols in Selivany Plain at Duhok Governorate, Kurdistan Region, Iraq

The study area located at the Selivany plain in Duhok governorate, Kurdistan Region, Iraq. Forty- three soil samples were taken from horizons in all studied pedons then physically and chemically analyzed according to standard methods. The studied soils were slightly alkaline non- saline. The values of CEC increased with increasing clay content. The Studied soils considered Vertisols and occurs pedoturbation, in turn, trans-locating organic matter from surface to subsurface and deep horizons, additionally, existing plant roots contribute in increasing organic matter in these horizons, and the humification process can occur in different soil horizons. Total carbonate content increased with increasing depth in subsurface horizons this due to the origin of limestone parent materials. The differences in carbonate distribution manner indicated to development. The studied soils contain a considerable amount of active carbonate that affecting different soil properties. Relatively high clay content in studied soils and its content at the surface horizons are lower than it at subsurface horizons. The high value of clay and silt content indicates to soil development. The following pedogenic processes can be specified loss, gain, leaching, illuviation, eluviation, alkalization, humification, lessivage, desalinization, calcification, decomposition, synthesis, pedoturbation, and braunification. Humification processes of organic matter are predominate because the ratio of carbon to nitrogen (C / N) is less than 25. According to the criterion (Total clay in B-horizon / Total clay at A-orizon) most of the studied pedons (1, 3, 6, 7, 8, 9, 10, 12, 13, and 14) considered as well developed soils. The ratio of (Active carbonate/ Total carbonate) was high ranged between (0.31-3.14%), and this may be due to the high weathering intensity of parent material, as a result of increased the ratio mass of active carbonate to total carbonate.

An Assessment of Cilacap Coast's Total Carbonate Sediment Content

Sediments are particles derived from the dismantling of rocks from the land and pieces of shell and remains of marine organisms that contain organic matter, included carbonate sediment. The total carbonate sediment content was influenced by many factors, such as sediment grain type. This study aimed to determine the carbonate content in sediments and to determine their relationship to the sediment grain characteristic on the Cilacap coast. The sediment's carbonate content used the titration method, while the sediment grain test used a dry filter. Statistical analysis was used to determine the sediment grain characteristic (mean, sorting, skewness, and kurtosis). The results showed that sediments' total carbonate content had a range of 1.93% - 6.23%, with an average of 4.21%. Sediments are dominated by fine sand with very well sorted, very platykurtic, and very fine skewed characteristics. The relationship between sediment grain characteristics and total sediment carbonate content showed a good correlation due to the sorting factor. Other parameters such as mean size and skewness have been shown a low correlation, whereas kurtosis has a shallow relationship with carbonate content.

Phacotus lenticularis content in carbonate sediments and epilimnion in four German hard water lakes

Autochthonous calcite precipitation is an important process for C-fixation in hard-water lakes, which is mainly induced by the photosynthesis of planktonic microorganisms. Among these, the widespread calcifying green alga Phacotus lenticularis (Ehrenberg) Diesing contributes to biogenic calcite precipitation in temperate regions. Its role in carbonate precipitation needs to be investigated, because there are no studies dedicated to the quantitative contribution of Phacotus shells to long term carbonate sequestration in hard-water lake sediments. In order to fill this gap, the Phacotus shell content in the sediments of four German hard-water lakes was determined and compared to the fraction of Phacotus shells in the total suspended autochthonous calcite of the euphotic zone.It was found that the Phacotus shells contributed at least 10% to the autochthonous carbonate precipitation in the upper water column in three investigated lakes. During a Phacotus mass occurrence with a cell density of 1.8 × 106 Ind L-1 in Lake Hopfensee, even 59% of the 3.6 mg L-1 total carbonate concentration consisted of Phacotus shells. In contrast to this high amount, the topmost basinal sediment contained a Phacotus shell content between 80 and 36,252 individuals per mg dry sediment, representing only 0.02% to 2.28% of the total carbonate sediment content. In a gravity core from Lake Grosser Ostersee, dating back ~150 years, the Phacotus shell content was continuously below 0.24% whereas the shell diameters remained equal to those of living individuals found in the water column proving that Phacotus shells are capable to persist in the sediment after deposition.A main reason for the large discrepancy between Phacotus shell abundance in the euphotic zone and in sediment was found to be the gross authigenic carbonate precipitation, which dilutes the sedimenting Phacotus shells that accumulate exclusively during short and intensive population peaks in summer. Additionally, dissolution of the carbonate shells during sedimentation was proven to be a relevant factor in Lake Igelsbachsee by means of reducing the number of Phacotus shells reaching the lake bottom. These facts explain that short-term high Phacotus carbonate contents of the total suspended carbonate in the water column do not mirror the contribution of Phacotus shells in the sedimentary record.

Factors Affecting the Generation of High-pH Environments Required for Stress Corrosion Cracking (SCC)

A series of seven experiments have been performed to investigate the effects of various environmental and operational parameters on the generation of high-pH SCC environments under disbonded permeable coating. The parameters investigated include: • the rate of CO2 generation; • direct CO2 production in the disbonded region under the coating; • preferential gas-phase transport of CO2; • the magnitude of the cathodic current density; and • simulated trapped water composition. In general, the total carbonate/bicarbonate concentrations of the simulated trapped water increased with: • increased CO2 flow rate; • direct production of CO2 under the disbonded coating; • increased cathodic current density; and • rapid gas-phase transport of CO2 through holidays above the level of the solution. Ca2+ and Mg2+ cations in groundwaters could buffer the solution in the disbondment at a range of pH 8 to 9 lower than the pH required for the occurrence of high pH SCC. Formation of insoluble carbonate minerals was detected in the simulated disbondment and in the coating with solutions rich in Ca2+ and Mg2+. However, the presence of poorly soluble Ca2+ and Mg2+ cations did not affect the total carbonate/bicarbonate concentration in the inner cell. These observations suggest that environments conducive to high-pH SCC are more likely to occur under the following circumstances: • in regions where the CO2 generation rate is higher, typically wetter and warmer locations; • for coating systems or in regions where there can be microbial activity under the disbonded coating; • in areas where the pipe is not permanently below the water table and where the coating has defects or holidays; and • in areas with a history of higher cathodic current density (which generally results in higher carbonate/bicarbonate concentration) and periodic loss of cathodic polarization.

Statistical patterns of carbonates and total organic carbon on soils of Tuber rufum and T. melanosporum (black truffle) brûlés

The ascocarps of several truffle species, such as Tuber rufum, are harvested in T. melanosporum brûlés; these species reduce T. melanosporum production. Some authors argue that this competition might be due to the evolution of organic matter in the soil. However, soil conditions in brûlés have yet to be clarified, and most studies on T. melanosporum fail to supply statistical data. We propose a study of 40 soils to compare the values for total organic carbon (TOC), pH, and carbonates inside the brûlés with the values for the outer edges of the same brûlés, where T. rufum ascocarps are collected. A principal component analysis relates the soils from the inner brûlés with high active carbonate content and soils outside the brûlés with high TOC and total carbonate content. ANOVA analyses indicate that the mean concentration of active carbonate, total CO32–, and % active/total carbonate differ significantly depending on soil location, but there are no significant differences for pH and TOC. These results lead us to propose a new hypothesis: T. melanosporum mycelia may solubilise active carbonate (<50 μm) and the other carbonate fractions (>50 μm) inside the brûlés; however the environmental conditions of the brûlés could favour a secondary carbonate precipitation with a net increase in active carbonate. This increase would counterbalance carbonate losses from leaching, which would in turn favour T. melanosporum mycelia, suggesting a feedback process.