CaCO3 Levels Research Articles

Minjingu phosphate rock availability in low-pH highly weathered soil as affected by added salts

Concentrations and identity of ions in the soil solution may affect soil phosphorus (P) reactions and P availability. In this study, the magnitude of these reactions was evaluated following the application of Minjingu phosphate rock (MPR) combined with chloride and carbonate salts of Na and Ca within an incubation experiment. Twenty-one days later NaOH-P and HCl-P were determined. This investigation was undertaken with the aim of identifying the role of Ca-ion activity in the liquid phase on the solubilization of MPR and formation of insoluble Ca-P phases. The increase in pH was higher with Na2CO3 than with CaCO3, while both CaCl2 and NaCl resulted in slight decreases in pH. The dissolution of MPR was higher overall when MPR was applied singularly than for the combined application of the phosphate rock with salts of calcium or sodium after 60 days of incubation. Dissolution of MPR decreased as levels of CaCO3 or CaCl2 increased but the decrease was more pronounced in CaCO3-treated than in CaCl2-treated soils. Ca-ion activity in the liquid phase is the main factor responsible for the insolubilization of MPR and the formation of insoluble Ca-P phases (HCl P). The formation of Ca-P solid phases increased with the concentration of Ca-ions, and was governed by the pH and nature of the accompanying anion. For soils with low levels of exchangeable cations and where liming is a recommended intervention measure, Ca from lime will form insoluble P phases and reduce the dissolution of PR and P availability to plants.

Levels of metals, arsenic and phosphorus in sediments from two sectors of a Brazilian Marine Protected Area (Tupinambás Ecological Station)

The Tupinambás Ecological Station (TES) is a Marine Protected Area consisting of two sectors: the Archipelago of Alcatrazes and the Cabras and Palmas islets. This investigation aimed to provide a first diagnosis of the concentrations of metals (Al,Cr,Cu,Fe,Hg,Ni,Pb,Zn), As and P in sediments from the TES. 24 sediment samples were collected in both sectors using a Van Veen grab sampler. Sediment textures and levels of Organic Matter (OM) and CaCO3 were determined, as well as the concentrations of the above-mentioned elements after partial acid digestion. Sediments were predominantly sandy. Higher levels of CaCO3 occurred in the Alcatrazes sector, whereas the OM contents were higher in the islets sector. Metals concentrations were low and associated with fines, while P and As presented a different behavior. The observed concentrations to all studies elements in sediments from the TES were considered as background values.

Soil Strength Improvement by Microbial Cementation

The biologically induced cementation (BioGrout) method has been used in this study to improve engineering properties of soil. Laboratory tests have been carried out to quantify the effect of BioGrout treatment on the strength of two types of sand by using Sporosarcina pasteurii bacteria. Bearing strength and other parameters, such as colony forming units (number of bacteria), pH level, temperature, and amount of CaCO3, have also been studied. Calcification (cementation) through precipitation of CaCO3 on the mineral surfaces has been clearly observed from the images of a scanning electron microscope (SEM). Finally, the effect of sand material on the effectiveness of biocementation was investigated via employement of different sand types.

Chronostratigraphy and paleoceanography of a piston core (EBP-3) from the South Korea Plateau in the East Sea (Japan Sea)

A piston core (EBP-3) collected from the South Korea Plateau in the East Sea (Japan Sea) preserved typical alternations of thick, dark laminated mud layers and bioturbated hemipelagic mud layers, but included several intercalated volcanic lapilli layers. The age estimate of core EBP-3 was aided by correlation of biostratigraphic radiolarian data, the abundance of microfossils (warm-water radiolarians), and geochemical properties (CaCO3) with the proxies of the well-dated core MD01-2407 obtained from the Oki Ridge. A part from the Marine Isotope Stage (MIS) 11 to MIS 9 in the middle of core EBP-3 was missing, presumably because of erosion following the abrupt deposition of a volcanic lapilli layer. Despite some uncertainty, the age estimate of core EBP-3 revealed that the lower part of core EBP-3 represents MIS 13, as was also evident from a comparison with the oxygen isotope stratigraphy.Downcore biogenic opal and CaCO3 variations in core EBP-3 exhibited less distinct orbital-scale cyclic changes than cores from other areas in the East Sea (Japan Sea). However, differences in features were discernible between MIS 2 and MIS 12 in terms of their lithology and CaCO3 constituent, although both periods were characterized by relatively high levels of CaCO3 (about 30% for MIS 2 and about 50% for MIS 12). MIS 2 preserved a typical thick, dark laminated mud layer, whereas MIS 12 preserved a distinctly light mud layer with thin parallel laminations. This difference of the lithologic facies between MIS 2 and MIS 12 highlighted a discrepancy among the major constituents, indicating that planktonic foraminifera were dominant in MIS 2, whereas coccolithophores were dominant in MIS 12. Our results suggest that the thinly-laminated light mud layer, which is characterized by a high CaCO3 content primarily composed of coccolithophores in MIS 12, can be used as a reliable time marker for the establishment of chronostratigraphy in the East Sea.

Effects of Soil Chemistry on Plant Germination and Growth in a Northern Everglades Peatland

Vegetation patterns across the Florida Everglades peatland are influenced by anthropogenic gradients in both hydrology and chemistry. These gradients often overlap, making it difficult to isolate specific causes of vegetation change. We examined whether differences in plant communities between the minimally impacted interior and the impacted perimeter of the northern Everglades could be attributed to soil chemistry as opposed to other factors such as hydrology or seed-bank composition. Seedling establishment from soil seed banks collected from interior locations was examined under conditions that reflected either the phosphorus (P)- and calcium-carbonate (CaCO3)-depleted chemistry of the peatland interior or enriched conditions around the perimeter. Three soil moisture treatments were used to increase seed-bank expression. The interior seed bank contained viable seeds of both interior and perimeter taxa, but distinct plant assemblages established in the two chemistry treatments. Perimeter species germinated in both chemistry treatments, but only survived under enriched conditions. Establishment of these species in the interior is likely limited by low P availability. Germination and survival of some interior species were reduced by enrichment, likely due to elevated CaCO3 levels. Protection from both increased P and CaCO3 loads thus appears important to maintain plant communities in mineral-poor remnants of the Everglades.

Pewarisan Sifat Ketahanan Hidup dan Karakter Fenotipik Melon (Cucumis melo L. “TALITA” & “TANIA”) Hasil Persilangan Backcross dan Testcross Induk Tacapa Pada Kondisi Karst Secara In-Vivo

Melon (Cucumis melo L.) is one of the fruits commodity priorities and require more attention. Plant breeding efforts led to improved varieties like TACAPA .TACAPA is a new melon cultivar derived from crosses between ♀ PI and ♂ Action with cross test PI. Since 2012, superior melon reassembled from crosses between ♀ TACAPA and ♂ PI become TANIA and ♀ TACAPA and ♂ Action become TALITA which projection can growth in critical lands karst. The objective of this research was to know ability to grow and morphological characteristics TALITA and TANIA melons were tested to determine nutrient levels of CaCO3. This research started from a field survey conducted in Hills of Mountain Sewu, South Mountain hills Sentolo Kulon Progo, and Dlingo Bantul, Yogyakarta.Melons grown on soil with fertilizer mixed media which further watering treated CaCO3 solution with a concentration of 0.5 % , 1%, 3%, 4%, and 5%. Observations were made until the time of harvest (± 10 weeks). TANIAand TALITA melon could grow on critical lands karst compared with parental. TANIA melonfruits have a weight, round, D - horizontal, D - vertical lower than two parental. TALITA melon fruits have a weight, D-horizontal higher than two parental, and D-vertical is lower than two parental. Keywords: critical land karst, Cucumis melo L., TALITA, TANIA

Dynamics of soil chemistry in different serpentine habitats from Serbia

To enhance understanding of edaphic conditions in serpentine habitats, a thorough investigation of chemical and mechanical properties of three soils from disjunct ultramafic outcrops in the central Balkans was undertaken. Soil from a nearby chemically-contrasting limestone habitat was also analyzed. Three plant species differently associated with serpentine (Halacsya sendtneri, Cheilanthes marantae, and Seseli rigidum) were references for site and soil selection. Twenty elements were scanned for, and fourteen were measured in seven sequentially-extracted soil fractions. Quantified soil properties also included: pH, levels of free CaCO3, organic matter, P2O5, K2O, N, C, S, cation exchange capacity, total organic carbon, field capacity and soil mechanical composition. The usual harsh components for plant growth in serpentine soil such as elevated Mg:Ca ratio, high levels of Ni, Cr, or Co, were significantly lower in the available fractions. There was a significant positive correlation of organic matter and field capacity, with most available Ca (70-80%) found in the mobile, rather than the organically-bound fraction. This showed that a more favorable Mg:Ca ratio is highly dependent upon a higher field capacity, which is also in accordance with a more developed vegetation. Increasing the availability of metals (Al, Ba, Ca, Cr, Cu, Mg, Ni, Zn) in a more developed serpentine grassland and forest vegetation, occurred only simultaneously with decrease of the Mg:Ca ratio and rise in other factors of fertility (N, P, K). Progressive development of ecosystem complexity therefore raised the availability of metals, but also reduced harsh Mg:Ca ratio disproportion, boosted levels of nutrients and raised soil field capacity. Principal components analysis confirmed that the main differences among serpentine habitats lay primarily in factors of fertility. The common habitat which hosts all three reference species offers intermediate conditions in a plant habitat selection gradient. Comparing serpentine with limestone showed ample difference in total content and availability of most of the surveyed elements, but very few differences in other chemical properties. The fragility of soil and ecosystem, and biological value of serpentine habitats demand intensive research and protection of these diversity and endemism hotspots of the Balkan Peninsula.

Gênese e classificação dos solos de uma topossequência em área de carste na Serra da Bodoquena , MS

Pouco se conhece sobre os solos dos sistemas cársticos carbonáticos no Brasil, apesar da sua importância e reconhecida fragilidade. Os objetivos deste estudo foram avaliar a gênese de solos desenvolvidos de rochas calcárias e materiais derivados e caracterizar os atributos desses, contribuindo para o Sistema Brasileiro de Classificação de Solos (SiBCS). Foram estudados três perfis de solos em uma topossequência na Serra da Bodoquena, MS, dispostos nas posições de sopé (P1), terço médio (P2) e topo (P3) de encosta suave-ondulada com pendente longa e perfil longitudinal plano-convexo-plano. Todos os perfis são profundos, com cores bruno-escura nos horizontes superficiais e avermelhada em subsuperfície, além de textura argilosa com incremento de argila em profundidade. O íon cálcio predomina no complexo sortivo, bem como a fração humina entre as frações húmicas. A micromorfologia dos solos revela feições de iluviação de argila em associação com feições de acumulações de CaCO3. Porém, em nenhum dos perfis, os teores de CaCO3 equivalente foram suficientes para o reconhecimento do horizonte cálcico e, ou, petrocálcico, ou de caráter carbonático ou hipocarbonático. Com sequência de horizontes A-Bt (P1); A-E-Bt (P2); e A-Bi (P3), os solos apresentam a seguinte ordem de evolução pedogenética: P1 > P2 > P3. De acordo com o SiBCS, os solos são classificados como Argissolo Vermelho eutrófico nitossólico (P1); Argissolo Vermelho distrófico típico (P2); e Cambissolo Háplico Tb eutrófico típico (P3). Para todos os perfis, no quinto nível aplica-se a classe de atividade de argila - Tm (atividade média), validando proposta recente do SiBCS.

Modelling and optimization of rebound resilience and hardness of defatted rice bran/calcium carbonate-filled NR vulcanisates

Hardness and rebound resilience of natural rubber (NR) vulcanisates filled with defatted rice bran (DRB)/calcium carbonate (CaCO3) were modelled and optimized. Second-order polynomial functions were generated to model the properties and to generate contour plots. Predicted properties of NR vulcanisates showed good agreement with experimental results. Hardness of filled-NR vulcanisates increased with filler loading, whereas rebound resilience decreased. At a fixed hardness level, lower CaCO3 loading can be used with partial DRB replacement. DRB incorporation into rubber compounds can improve their stiffness. Contour plots were used to identify DRB and CaCO3 level ranges for achieving optimum hardness and rebound resilience.

Induction of Calcium Carbonate by Bacillus cereus

The purpose of this research was to study how the bacteria Bacillus cereus (DCB1) utilizes calcium ions in a culture medium with carbon dioxide (CO2) to yield calcium carbonate (CaCO3). The bacteria strain DCB1 was a dominant strain isolated from dolomitic surfaces in areas of Karst topographies. The experimental method was as follows: a modified beef extract-peptone medium (beef extract 3.0 g, peptone 10 g, NaCl 5.0 g, CaCl2 2.0 g, glass powder 2.0 g, distilled water 1 L, and a pH between 6.5 and 7.5) was inoculated with B. cereus to attempt to induce the synthesis of CaCO3. The sample was then processed by centrifugation every 24 h during the 7-day cultivation period. The pH, carbonic anhydrase (CA) activity, and the concentrations of both HCO- 3 and Ca2+ in the supernatant fluid were measured. Subsequently, precipitation in the culture medium was analyzed to confirm, or otherwise, the presence and if present, the formation, of CaCO3. Methods used included X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy Dispersive Spectroscopy (EDS). Meanwhile, the carbon source in the carbonate was classified by its isotope composition. Results showed that B. cereus can improve its pH value in this culture medium; concentrations of HCO- 3 and Ca2+ showed a significant decline over the duration of the cultivation period. CA activity reached its maximum during the second day; XRD, SEM, TEM, and isotope analysis all revealed the presence of CaCO3 as a precipitate. Additionally, these results did not occur in an aseptic control group: no detectable level of CaCO3 was produced therein. In conclusion: B. cereus can metabolize active materials, such as secretase, by its own growth and metabolism, and can either utilize atmospheric CO2, or respire, to induce CaCO3 production. Experimental evidence is offered for a concomitant CO2 reduction and CaCO3 induction by microorganisms.

Determination of calcium carbonate and styrene-butadiene latex content in the coating layer of coated paper

The surface infrared spectra of coated paper with different levels of calcium carbonate and SB-latex in the coating layer were measured using ATR-FTIR. The relations between different levels of CaCO3 and SB-latex and their respective characteristic peak areas were then established. The results show that the general regression neural network (GRNN) model can be used to estimate the CaCO3 and SB-latex contents in coatings of coated papers. The maximum errors for calcium carbonate and SB-latex were only 3.32% and 3.39%, respectively, and occurred under conditions that are at the extreme of what might be encountered in an actual production facility.

ASSESSMENT OF CHEMICAL AND BIOCHEMICAL INDICES FOR DIAGNOSING ZN DEFICIENCY AND SOIL ASSOCIATED FACTORS OF CITRUS (CITRUS SINENSIS L. OSBECK) NUTRITION

A three phase research programme was planned to assess the chemical and biochemical indices for diagnosing Zinc (Zn) deficiency and soil associated factors of citrus nutrition in Marathwada region of Maharashtra state of India. In the first phase a survey of sweet orange orchards was carried out to evaluate the nutritional status and determine constraints in fruit production. In the second phase a pot culture experiment was conducted to evaluate the critical concentration of Zn in soil and leaf. Similarly biochemical indices the CAA (Carbonic Anhydrase Activity) and chlorophyll was also studied. While in third phase, another pot culture experiment was conducted to determine the effect of lime, organic manure and Zn on growth of sweet orange seedlings. Phase I revealed that sweet orange orchards (Citrus sinensis L. Osbeck) of the region are grown on variety of soils (Entisol, Inceptisol and Vertisol) without considering their suitability. Similarly intercrops are planted without testing compatibility. Analysis of orchard soils showed they were calcareous and predominantly clay in texture. Leaf analysis confirmed wide spread deficiency of N and Zn followed by P. Biochemical indices viz. CAA and chlorophyll content of sweet orange leaf were found to be a sensitive and indicator of Zn deficiency. Sweet orange orchards established on Inceptisols performing better than the orchards established on other soil types. Improvement in sweet orange seedling was recorded with high Zn soils supplied with 5 mg Zn, marginal Zn status soils with 10 mg Zn and low Zn status soils with 15 mg Zn kg-1. Reduction in sweet orange growth was noticed with 15 to 20% CaCO3 level. It was further concluded that detrimental effect of high CaCO3 content (up to 20%) on growth can be alleviated to some extent by applying double or triple (10 to 15 g organic manure kg-1) the recommended dose of organic manure. Organic manure in combination with Zn application performed best in improving growth, uptake of Zn, CAA, chlorophyll content and dry matter production of sweet orange seedlings. Critical soil Zn concentration under different levels of CaCO3 and organic matter content for sweet orange varied from 1.04 to 1.17 mg kg-1, while critical leaf Zn con¬centration varied from 28.80 to 36.40 mg kg-1. The variations in critical concentration of Zn in soil and sweet orange leaf are attributed to the variability of CaCO3 and organic matter in soil.

Impact of calcium carbonate and temperature on survival of Escherichia coli in soil

Spreading of waste organic matter on agricultural lands is considered to enhance soil microbial activities and physical properties and improves soil nutrient status. However, organic wastes have also been shown to be a source of microbial contaminants including pathogens. Related risks are governed by pathogens' survival and transport particularities. We evaluated the significance of high levels of CaCO3, common in arid and semi-arid soils, on survival of Escherichia coli NAR at different temperatures. Amendments of 0, 5, 10, 15 or 25 g CaCO3 were mixed into variable soil amounts to obtain 100 g soil–CaCO3 mixtures. Both sterile and non-sterile soil mixtures were tested. Suspensions of a nalidixic acid-resistant E. coli strain (E. coli NAR) were added to the mixtures at a rate of 106 cell g−1 soil. Mixtures were incubated at 4, 15, or 37 °C at the soil's field capacity for water (i.e. 0.13 g g−1). Each treatment was tested in triplicate. Persistence of culturable E. coli NAR was verified throughout the incubation period. The recovery rates of culturable E. coli NAR were significantly correlated to CaCO3 concentrations (P < 0.05). Incubation temperature (T) was the most significant factor (P < 0.01). In non-sterile mixtures the largest decline in survival rates of E. coli NAR was measured for treatments with larger CaCO3 content (i.e. 15 and 25%). Interaction of temperature and CaCO3 was significant for E. coli NAR die-off. Sterilization of soil caused non-uniform fluctuations in the effect of treatments. The maximum calculated decay rate for E. coli NAR was 0.83 d−1 for the 15 g CaCO3 non-sterile mixture incubated at 37 °C while the minimum was 0.09 d−1 for the control unamended sterile soil incubated at 15 °C. A combination of high temperature, large CaCO3 concentrations and a non-sterile, biologically active soil created the least favorable conditions for E. coli survival.

Optimizing Available Phosphorus in Calcareous Soils Fertilized with Diammonium Phosphate and Phosphoric Acid Using Freundlich Adsorption Isotherm

In calcareous soils, phosphorus (P) retention and immobilization take place due to precipitation and adsorption. Since soil pH is considered a major soil variable affecting the P sorption, an acidic P fertilizer could result in low P adsorption compared to alkaline one. Therefore, P adsorption from DAP and phosphoric acid (PA) required to produce desired soil solution P concentration was estimated using Freundlich sorption isotherms. Two soils from Faisalabad and T. T. Singh districts were spiked with 0, 10, and 20 % CaCO3 for 15 days. Freundlich adsorption isotherms (P = aC b/a) were constructed, and theoretical doses of PA and DAP to develop a desired soil solution P level (i.e., 0.20 mg L−1) were calculated. It was observed that P adsorption in soil increased with CaCO3. Moreover, at all the levels of CaCO3, P adsorption from PA was lower compared to that from DAP in both the soils. Consequently, lesser quantity of PA was required to produce desired solution P, 0.2 mg L−1, compared to DAP. However, extrapolating the developed relationship between soil CaCO3 contents and quantity of fertilizer to other similar textured soils needs confirmation.

Parathyroid hormone levels in neonates with suspected osteopenia

The goal of this study is to describe secondary hyperparathyroidism in extremely low birthweight (ELBW) neonates and their response to enteral calcium carbonate (CaCO(3)) supplementation. A retrospective case series was conducted on extremely low birth infants, <1000 g birthweight, who survived hospitalisation, had no major congenital anomalies and had all their care in our institution During this 6-year period, 231 ELBW infants survived hospitalisation at our institution. Of the 231 patients, parathyroid hormone (PTH) levels were performed in 66 of these patients (29%) and were elevated in 54 patients (82% of those tested). The timing of this testing was sporadic and was often performed after recognising osteopenia on radiography. Of the 54 patients with high PTH levels, 44 (81%) were treated with CaCO(3) and PTH levels were monitored while on therapy. The average duration of therapy was 41 ± 28 days, with 64% of PTH levels returning to normal before discharge. PTH is a major hormone responsible for bone resorption, and serum levels may be a useful marker in identifying ELBW neonates at risk for metabolic bone disease. ELBW neonates with secondary hyperparathyroidism may benefit from enteral supplementation with CaCO(3). Further studies are needed to better evaluate the incidence, timing and potential treatment of hyperparathyroidism in ELBW infants.

Effects of sulphur and zinc applications on growth and nutrition of bread wheat in calcareous clay loam soil

-1 with 5 mg Znkg -1 application to the soil, the grain Zn concentration increased 38.47% when compared with no sulphur and zinc treatment to soil. The zinc treatment led to a significantly reduced straw Fe concentration. The straw dry weight was significantly affected by sulphur alone and it increased from 2.53 to 3.86%. The grain dry weight was significantly affected by zinc alone and it decreased by 12.18%. But, the grain zinc concentration increased 25% by increasing the zinc. The results suggest that application of sulphur and zinc could be a good approach for the nutrition of wheat plants. However, the generated salinity was high for sulphur applications, which means that plants might be faced high salinity problems. Also, with the application of high sulphur to plants, it should be considered that an N:S imbalance can occur. On the other hand, N:S imbalance can occur in crops grown in high N fertility in especially, S-deficient soils. Therefore, the levels of electrical conductivity, pH, texture, CaCO3, organic matter, sulphur and nitrogen of soils and cultivated plant species should be taken into consideration when recommending sulphur and zinc application to soils.

Effects of sulphur and zinc applications on growth and nutrition of bread wheat in calcareous clay loam soil

The objective of this study was to evaluate the effects of sulphur (S) and zinc (Zn) on soil pH and electrical conductivity (EC), nitrogen (N), S, iron (Fe), Zn, N:S ratio; and straw and grain dry weight of wheat grown in a calcareous clay loam soil. For this purpose, a pot experiment was conducted in greenhouse conditions. Sulphur was applied at 0, 10, 50, 250 mg Skg-1 (as CaSO4.2H2O) and zinc at 0, 5 mg Znkg-1 (as ZnSO4.7H2O) to the soil. The soil pH decreased by S alone. The soil EC increased due to increase in sulphur with zinc. The straw S concentration increased by sulphur alone. In the 250 mg Skg-1 application to soil, the straw S concentration increased by 28.13% when compared with 0 mg Skg-1 treatment. The concentrations of grain S and Fe, straw Zn, straw and grain N and N:S ratios were not significantly affected by sulphur and zinc. The grain Zn concentration was significantly increased by sulphur with zinc. In the 250 mg Skg-1 with 5 mg Znkg-1 application to the soil, the grain Zn concentration increased 38.47% when compared with no sulphur and zinc treatment to soil. The zinc treatment led to a significantly reduced straw Fe concentration. The straw dry weight was significantly affected by sulphur alone and it increased from 2.53 to 3.86%. The grain dry weight was significantly affected by zinc alone and it decreased by 12.18%. But, the grain zinc concentration increased 25% by increasing the zinc. The results suggest that application of sulphur and zinc could be a good approach for the nutrition of wheat plants. However, the generated salinity was high for sulphur applications, which means that plants might be faced high salinity problems. Also, with the application of high sulphur to plants, it should be considered that an N:S imbalance can occur. On the other hand, N:S imbalance can occur in crops grown in high N fertility in especially, S-deficient soils. Therefore, the levels of electrical conductivity, pH, texture, CaCO3, organic matter, sulphur and nitrogen of soils and cultivated plant species should be taken into consideration when recommending sulphur and zinc application to soils. Key words: Sulphur, zinc, soil pH, soil salinity, calcareous soil, wheat, N, Fe, Zn, N:S ratio.

Experimental investigations and optimization of processibility of sheet moulding compound

Abstract Sheet moulding compound (SMC) is a combination of glass fibers and filled polyester resin. It is processed by a compression moulding process and finds extensive applications in structural, automotive, electrical and electronic industries. The compression moulding process is characterized by the flow behavior of SMC under heat and pressure in the press mould. This paper is focused on the prediction of ideal processibility conditions of SMC. The qualitative aspect of a properly thickened (matured) moulding compound could be seen from its tack-free nature, which was quantitatively calibrated in terms of penetration depth, measured by a specially constructed softness indicator. The weight (wt)% of calcium carbonate (CaCO3) as filler, magnesium oxide (MgO) as thickener, graphite (C) and zinc stearate [Zn (C18H35O2)2] (ZnSt) as lubricants along with the maturation time (Tm) were selected as process variables. Taguchi’s scheme of experimental design was adapted to perform the experiments. It was found that the higher levels of MgO and CaCO3 were favorable for a good penetration depth as well as a reduced maturation time. We have also found that a penetration depth of at least 5 mm was required for achieving good processability conditions of SMC. An optimization study was under taken to find the right blend of additives and fillers, at their minimal weights and in the least possible maturation time, to achieve the desired processability. This study is particularly useful in a production run to make moulded parts from SMC.

Bioavailability of arsenic in the soil horizon: a laboratory column study

Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long-term detrimental effects to surface soils. Such contamination can also directly affect human health when irrigated crops, such as rice, vegetable and fruits, are used for human consumption. Therefore, an understanding of the leaching behavior of As in surface soils is of high importance, because such behavior may increase the bioavailability of As in the soil horizon. In this study, we have investigated the role of phosphate ions in leaching and bioavailability of As in the soil horizon, where drinking groundwater contains elevated levels of As (≥50 μg/L). Soil and groundwater samples were characterized in the laboratory and measured for physical and chemical constituents. The soils are generally neutral to slightly alkaline in character (pH range 7.5–8.1) with low to moderate levels of free Fe2O3, Al2O3, CaCO3, organic carbon, and clay content. The measured electrical conductivity (mean 599 μS/cm) of the soils demonstrates their non-saline nature. The Eh values (range −37 to −151 mV) of the groundwater indicate anoxic condition with low to moderate levels of bicarbonate (range 100–630 mg/L) and phosphate (range 0.002–4.0 mg/L). The arsenic content (range 50–690 μg/L; mean 321 μg/L) in groundwater has exceeded both WHO recommended guideline values (10 μg/L) and the National safe drinking water limit (50 μg/L). Regression analyses demonstrate that the bioavailability of As in the soil horizon is mainly controlled by the composition of free Fe2O3 and CaCO3 content of the soils. However, application of P could increase bioavailability of As in the soil horizon and become available to plants for uptake.

The effects of CaCO3 on adsorption, immobilization and activity of cellulase in a decarbonated soil

The interaction of organic molecules with mineral surfaces is a subject of interest in a variety of disciplines. The present study was done to elucidate some aspects of sorption and immobilization of cellulase on soil components by analysis of the sorption, desorption, immobilization and activity of cellulase on a decarbonated soil treated with different levels of CaCO3 (0, 2.5, 10 and 20 %). Applied concentrations of cellulase protein on Ca-homoionized soil suspensions were 0, 0.014, 0.028, 0.070, 0.140, 0.280, 0.701, 0.981 and 1.402 mg mL-1. After shaking for 1 h in sterile conditions, they were centrifuged and the amount of the cellulase protein remaining in solution was determined. The adsorbed cellulase protein was calculated. The immobilized and desorbed cellulase proteins were calculated after washing soil suspensions thrice with distilled water. Analysis of variance showed that the effects of the enzyme concentration, CaCO3 level and their interaction on cellulase protein adsorption and activity were statistically significant. The adsorption and immobilization capacities of the decarbonated soil increased by application of CaCO3. However, these effects of CaCO3 were only significant when high concentrations of cellulase protein were added to the soil. The desorption of cellulase protein from the decarbonated soil did not depend on the amount of cellulase adsorbed on the soil and the CaCO3 level in the soil. The immobilized cellulase activity, and particularly its specific activity, decreased considerably by increasing CaCO3 levels in the soil. This negative effect of CaCO3 on the cellulase specific activity in the decarbonated soil was significant even for low levels.