clay fraction
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2022 ◽  
Author(s):  
Tatiana Minkina ◽  
Dina Nevidomskaya ◽  
Aleksey Sherbakov ◽  
Victor Chaplygin ◽  
Yurii Litvinov ◽  
...  

Heavy metals (HM) are among the most hazardous soil pollutants. The intensity of accumulation and distribution of HM in soils directly depends on the ecological conditions of pedogenesis and its buffering properties. At the same time, a significant accumulation of HM in the soil as a result of anthropogenic impacts reduces the buffering capacity of the soil and its resistance to pollution. The purpose of this work was to assess the buffering capacity of soils to HM pollution in the Don River delta and the coast of the Taganrog Bay of the Sea of Azov undergoing the great anthropogenic impact. The buffer capacity of experimental soils was carried out using the Il’in’s method (1995), based on the calculation of the inactivation ability of soils: organic matter, clay fraction (particle size < 0.01 mm), carbonates, sesquioxides, and pH. The content of HM was compared with soil Clarke and the maximum permissible concentration of HM in soils accepted in the Russian Federation. It was found that the experimental soils could be ordered by buffer capacity value as following (in decreasing order): haplic chernozem ≥ alluvial-meadow light loamy ≥ solonchak > alluvial-meadow sandy and sandy loamy > sandy primitive soil ≥ stratified alluvial soil. Keywords: trace elements, contamination, impact territories


Author(s):  
Rayane de Lima Moura Paiva ◽  
Adriana Paiva Souza Martins ◽  
Lucas Rosse Caldas ◽  
Oscar A.M. Reales ◽  
Romildo Dias Toledo Filho

The incorporation of sustainable materials in the civil construction sector has grown in recent years to minimize environmental impacts. Among these materials, the use of earth, a local raw material that does not require much energy for its processing, appears as an advantageous and promising alternative. Earth mortars stabilized with natural binders, when compared to conventional mortars, can have technological, economic and environmental advantages. The objective of this work was to develop an earth-based mortar stabilized with mineral binders using a 1:3 binder to aggregate mass proportion, and to evaluate its fresh and hardened state properties, as well as its environmental impacts using Life Cycle Assessment (LCA) with a cradle to gate scope. The selected materials were divided in four groups: (i) cement, hydrated lime, fly ash and metakaolinite (binders), (ii) natural sand and coarse fraction of the earth (aggregates), (iii) calcium chloride and superplasticizer (additives) and (iv) water. In the matrix formulation the clay fraction from earth constituted the majority of the binder. The selection of supplementary cementitious materials as additional binders provided improvements in workability and mechanical properties of the mortar. A mix design was carried out using different cement (5; 7.5 and 10%) and fly ash (11; 13.5 and 16%) mass percentages. The water/binder material ratio, superplasticizer content and calcium chloride content were 0.65; 2% and 1%, respectively. The results showed that an increase in fly ash content combined with a decrease in cement content provided an increase in workability and a decrease in mechanical properties of mortars. Nevertheless, the mechanical performance of the mortars remained above the minimum values prescribed in Brazilian construction codes. From the results analysis it was concluded that partial replacement of cement by fly ash provided greater workability in the fresh state and reduced the environmental impacts of the earth-based mortar.


FLORESTA ◽  
2022 ◽  
Vol 52 (1) ◽  
pp. 025
Author(s):  
Rafael Cipriano da Silva ◽  
Karen Beneton ◽  
João José Cardinali Ieda ◽  
Antonio Carlos de Azevedo ◽  
Marcos Gervasio Pereira

Success in the production of eucalyptus seedlings directly affects the development of plants in the field. Several factors influence their initial growth, especially the substrate. This study aimed to evaluate the growth of Eucalyptus globulus seedlings and characteristics of the substrate using silicate agromineral (SA) in different proportions (substrate:SA; v/v): T0 – 100:00%, T1 – 90:10%, T2 – 80:20%, and T3 – 50:50%. The treatments were evaluated using a completely randomized design. Measurements of height (H), stem diameter (SD) and calculation of the H/SD ratio of the plants were performed every 3 weeks, totaling 4 measurements. At the end of the experiment (12 weeks), soil fertility analyses, granulometric analysis (sand, silt and clay) and total chemical analysis were carried out. Due to the chemical and mineralogical composition of SA, its use in substrate in a greater proportion (T3) promoted the increase of exchangeable K, Ca and Si contents, which influenced the increase in the sum of bases and cation exchange capacity. The levels of assimilable P and micronutrients Fe, Cu, Zn and Mn were also higher in this treatment. The increase in  SA proportions in the substrate composition also favored increase in the sand fraction and reduction in the clay fraction. As for the growth of seedlings, the results were not significant for H and SD as a function of SA doses, leading to the conclusion that the solubilization and slow release of nutrients by SA did not influence the growth of the plants


Author(s):  
Yang Zhang ◽  
Yan Zhang ◽  
Yan Gao ◽  
Dandan Huang ◽  
Xuewen Chen ◽  
...  

Residue return can prevent or restore the degradation of cropland, meanwhile, additional N input from residue return inevitably result in the changes of soil nitrogen (N) pools. Our objectives were to evaluate these changes in a 16-year field experiment. The residue return experiment consisted of no-tillage (NT) and mouldboard plough (MP), combined with continuous maize (Zea mays L.) (MM) and maize-soybean (Glycine max Merr.) rotation (MS) cropping systems, that is, NTMM, NTMS, MPMM, MPMS; conventional tillage (removal of crop residue and deep plough) with continuous maize (CTMM) was included as a control. The soil was separated into density (LF, light fraction) and particle size (sand, silt and clay) fraction. In 0-5 cm and 5-10 cm layers, soil TN content in NT was higher than MP, whereas the opposite trend was observed in 10-20 cm. Thus, the stratification ratio of soil TN was greater under NT. Cropping system affected soil TN as MM > MS. Residue return increased soil N storage by 6.44%-24.85% in the plough layer. Taking CTMM as the baseline, NTMM and MPMM increased the N storage in all physical fractions, while the decrease of silt-N storage was observed in NTMS and MPMS. Under residue return, the distribution of N storage changes in LF and sand fraction was affected by tillage practice, and that in silt and clay fraction was affected by cropping system. In summary, NTMM is effective for soil N accumulation due to its highest N storage and all physical fractions of N storage was enhanced.


2021 ◽  
Vol 9 ◽  
Author(s):  
Amin Ghafarpour ◽  
Farhad Khormali ◽  
Xianqiang Meng ◽  
Hossein Tazikeh ◽  
Thomas Stevens

Paleoclimatic investigation of loess-paleosol sequences from northern Iran is important for understanding past changes in a region highly sensitive to shifts in precipitation, and along potential routes of past human migration. Here, we present carbon and oxygen isotopic compositions of bulk carbonate (δ13Cbc and δ18Obc, respectively) coupled with particle size distributions of samples from the Mobarakabad section, northern Iran, to study past wind dynamics and hydroclimate. We also present new initial clay-sized Hf-Nd isotope results from key horizons in order to assess general dust sources. Variations of δ13Cbc and δ18Obc values of modern soils compared to paleosols allow reconstruction of late Pleistocene–Holocene climate change in the area. Our results show severe drought during a major eolian deposition phase (EDP) after 34 ka. The thickness and PSD of the C horizon of unit 5 suggest significant shifts in loess sources and depositional environments during this EDP after 34 ka. Indeed, based on our new clay-sized Hf-Nd data, we hypothesize that the loess unit 5 might originate from the young crustal source of the Alborz and Kopet Dagh mountains. In general, the PSD of C horizons in the section is bimodal in the silt fraction and the very small, very fine clay fraction, with a mode at c. 1 μm in the modern soil and paleosols possibly produced by weathering and pedogenic processes. There also appears to be a good correlation between δ13Cbc and δ18Obc values, differentiating phases of loess accumulation and paleosol formation and hence providing quantitative data for reconstructing paleoclimatic conditions in the study area.


2021 ◽  
Author(s):  
Madhujya L. Phukan ◽  
Saad A. Siddiqi ◽  
Abdulla Alblooshi ◽  
Maryam Alshehhi ◽  
Ashis Shashanka ◽  
...  

Abstract Objectives/Scope: The late Callovian to early Kimmeridigian deposited Tuwaiq Mountain, Hanifa and Jubaila Formations are among the most prolific source rocks in the middle east. These sediments have recently been considered as potential unconventional gas reservoir in UAE. This study integrates sedimentological, structural, geochemical and pore-scale datasets to provide a better understanding of the depositional framework and its effects on the reservoir properties. Methods, Procedures, Process: Dunham Classification (1962) which was later modified by Embry & Klovan (1971) is the basis of the descriptive lithofacies scheme used to characterize the organic-rich carbonate sediments. The association of these classified lithofacies based on their genetic relationship reflects their corresponding depositional environments. Petrographical and geochemical assessment including Rock-Eval pyrolysis were performed on selected samples. Mineralogical assessment was performed via whole-rock and clay-fraction XRD analysis, whereas pore-scale fabric/textural investigations were performed via conventional transmitted light microscopy and SEM using backscattered electron mode BS-SEM. Results, Observations, Conclusions: Sedimentological characterization of mud-dominated carbonate sediments indicates that they accumulated in a clastic starved, intrashelf basinal setting. The lack of textural variation is observed, highlighted by the dominance of mudstones noted across the Tuwaiq Mountain Fm., Hanifa and Jubaila Formations. Wackestones are the second most abundant texture observed. Wacke-packstones and packstones are rare but are present in the Tuwaiq Mountain Formation. also dominated by mudstone textures show presence of wackestones in form of thin beds. The occurrences of planktonic foraminifera along with thin shelled bivalves further emphasizes the low-energy, distal depositional setting. A quantitative description of the nature, density, and trends of the fracture network highlights the tectonic and structural history of the sediments. A certain degree of brittleness is associated with the organic-rich sediments, which is evident from the mineralogical analysis showing the abundance of calcite (&gt;82%). Rock-Eval data revealed high TOC content of the sediments. An evaluation of the HI and Tmax indicates that the sediments are dominantly gas prone (HI&lt;150mg HC/g TOC). Based on the calculated reflectance data (Ro: 0.06-3.30), the sediments display varied levels of thermal maturity, from immature to over mature. The vitrinite reflectance equivalent (%VRE) values assessed from microscopic investigations a range between 1.24-1.64, with the lower values suggesting late maturity with wet (condensate) gas generation and the higher values suggesting post maturity with dry gas generation. The TOC and TRA data highlight that the organic-rich, laminated mudstones associated with the Hanifa and Tuwaiq Mountain Formations have the highest TOC values (up to 4.25wt%) and the highest bulk volume (up to 3.39 %BV). It is also noted that the petroleum storage potential in these sediments largely resides with the mineral matrix pores along with the porosity hosted by the organic matter, which has been assessed by BS-SEM analysis. Novel/Additive Information: This integrated approach sheds light on the development of unconventional gas reservoirs. In addition, this study shows how the changes in depositional environment may have controlled the organic matter preservation. For a plausible way forward, this current understanding may be extrapolated to uncored intervals for representativeness.


Water ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 3441
Author(s):  
Jingyu Ji ◽  
Junzeng Xu ◽  
Yixin Xiao ◽  
Yajun Luan

The accurate monitoring of soil water content during the growth of crops is of great importance to improve agricultural water use efficiency. The Campbell model is one of the most widely used models for monitoring soil moisture content from soil thermal conductivities in farmland, which always needs to be calibrated due to the lack of adequate original data and the limitation of measurement methods. To precisely predict the water content of complex soils using the Campbell model, this model was evaluated by investigating several factors, including soil texture, bulk density and organic matter. The comparison of the R2 and the reduced Chi-Sqr values, which were calculated by Origin, was conducted to calibrate the Campbell model calculated. In addition, combining factors of parameters, a new parameter named m related to soil texture and the organic matter was firstly introduced and the original fitting parameter, E, was improved to an expression related to clay fraction and the organic matter content in the improved model. The soil data collected from both the laboratory and the previous literature were used to assess the revised model. The results show that most of the R2 values of the improved model are >0.95, and the reduced Chi-Sqr values are <0.01, which presents a better matching performance compared to the original. It is concluded that the improved model provides more accurate monitoring of soil water content for water irrigation management.


Geoderma ◽  
2021 ◽  
Vol 404 ◽  
pp. 115293
Author(s):  
Chong Wang ◽  
Shuang-yang Li ◽  
Xiao-jia He ◽  
Qian Chen ◽  
Hao Zhang ◽  
...  

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