Effects of Urbanization Intensity on Glomalin-Related Soil Protein in Nanchang, China: Influencing Factors and Implications for Greenspace Soil Improvement

Glomalin-related soil protein (GRSP) is a stable and persistent glycoprotein secreted by arbuscular mycorrhizal (AM) fungi that plays important roles in sequestering soil organic carbon (SOC) and soil quality improvement. Rapid urbanization has led to serious greenspace soil disturbances, resulting in soil degradation. However, few researches have examined the effects of urbanization on GRSP and its influencing factors. In this study, impervious surface area (ISA) was selected as an indicator of urbanization intensity. A total of 184 soil samples were collected from the 0-20 cm soil layer in the Nanchang greenspace, China (505 km2). The GRSP content, soil properties, urban forest characteristics, and land-use configuration were determined and investigated. The results showed that total GRSP (TG) and easily extractable GRSP (EEG) averages were 2.38 and 0.57 mg·g-1, respectively. TG and EEG decreased by 16.22 % and 19.68 %, respectively, from low to heavy urbanization areas. Linear regression analysis revealed a negative correlation between SOC and GRSP/SOC. SOC decreased from 39.9 to 1.4 mg·g-1, while EEG/SOC and TG/SOC increased by about 17 % and 34 %, respectively, indicating the important contribution of GRSP to the SOC pool. Pearson and redundancy analysis showed that GRSP was positively correlated with soil SOC, P, N, vegetation richness, and tree height but negatively correlated with pH, bulk density, and impervious area. The partial least squares path model (PLS-PM) further showed that urbanization affected soil properties, forest characteristics, and land use factors leading to GRSP changes. This study revealed the effects and key influencing factors of urbanization on GRSP. In the future, urban greenspace soil improvement can be considered from the new perspective of enhancing GRSP soil content.

Rhizosphere analysis of field-grown Panax ginseng with different degrees of red skin provides the basis for preventing red skin syndrome

Background Ginseng red skin root syndrome (GRS) is one of the most common ginseng (Panax ginseng Meyer) diseases. It leads to a severe decline in P. ginseng quality and seriously affects the P. ginseng industry in China. However, as a root disease, the characteristics of the GRS rhizosphere microbiome are still unclear. Methods The amplicon bacterial 16 S rRNA genes and fungal ITS (Internal Transcribed Spacer) regions Illumina sequencing technology, combined with microbial diversity and composition analysis based on R software, was used to explore the relationship between soil ecological environment and GRS. Results There were significant differences in the diversity and richness of soil microorganisms between the rhizosphere with different degrees of disease, especially between healthy P. ginseng (HG) and heavily diseased groups. The variation characteristics of microbial abundance in different taxa levels were analyzed. The interaction network of rhizosphere microorganisms of P. ginseng under GRS background was established. We also found that different P. ginseng rhizosphere microbial communities have multiple changes in stability and complexity through the established interaction network. Microbes closely related to potential pathogenic fungi were also identified according to the interaction network, which provided clues for looking for biological control agents. Finally, the Distance-based redundancy analysis (dbRDA) results indicated that total phosphorus (TP), available potassium (AK), available phosphorus (AP), catalase (CAT), invertase (INV) are the key factors that influence the microbial communities. Moreover, the content of these key factors in the rhizosphere was negatively correlated with disease degrees. Conclusions In this study, we comprehensively analyzed the rhizosphere characteristics of P. ginseng with different levels of disease, and explored the interaction relationship among microorganisms. These results provide a basis for soil improvement and biological control of field-grown in the future.

Residue from coal combustion for plastic soil improvement

The combustion of coal in Hoffman-type furnaces generates ash as one of the process residues. This research seeks to make use of this residue to improve plastic subgrade soils in tertiary roads, considering that in Colombia a large percentage of these are not paved. A soil with high plasticity has been selected to make mixtures with ash dosages that vary from 0% to 15% with respect to the dry weight of the soil. To determine the variation of the physical and mechanical properties of the soil-ash mixtures tests of consistency limits, compaction tests, and California bearing ratio were carried out. The results showed that the mixture in which 12% of the coal combustion residue is added to the soil, as a percentage for the dry weight of the soil, has a better physical behavior and bearing capacity than the soil in its natural state. obtaining an increase of up to 75% in the California bearing ratio.

Red Yeast Improves the Potential Safe Utilization of Solid Waste (Phosphogypsum and Titanogypsum) Through Bioleaching

Phosphogypsum (PG) and titanium gypsum (TG), as a by-product (solid waste) in phosphate fertilizer and titanium dioxide industry, are causing serious environmental hazards. The resource/harmless application of PG and TG is the development trend in the future. The biological function of red yeast (Rho: Rhodotorula mucilaginosa) can effectively reduce the concentration of pollutants in the environment and has the potential of biological flotation/purification of mineral solid waste. In this study, the bioremediation mechanism and safe utilization efficiency of Rho for different contents of PG and TG were explored by using its biological flotation function. The X-ray fluorescence spectrometry (XRF) results showed that F was the main toxic element in PG and TG, and Pb and Cd did not reach the detection limit. The processing capacity of Rho for PG (>10 g/ml) is higher than that of TG (<5 g/ml). After bioleaching by Rho, the proportion of F in PG and TG solid decreased by 61.45–63.79% and 49.45–59.19%, respectively. The results of three-dimensional fluorescence, extracellular polymeric substance (EPS) extraction, X-ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed that Rho could accelerate the release of harmful elements (F) in PG and TG. SEM showed that Rho cells and secretions adhered and wrapped on PG/TG, causing PG/TG decomposition and fragmentation. In addition, the adsorption of EPS and the formation of Ca5(PO4)3F are two main ways for Rho to remove F. Furthermore, under the condition of high concentration bioleaching, Rho can accelerate the release and utilization of P in PG, which is not only for the re-precipitation of Ca5(PO4)3F but also conducive to the reproduction and utilization of microorganisms. Meanwhile, the purification/safe reuse of PG by Rho is easier than that of TG. Therefore, the toxicity of PG and TG bioleaching by Rho can be greatly reduced, suggesting the huge potential of Rho in soil improvement and remediation.

ANALYSIS OF LATERITE SOIL WITH PORTLAND CEMENT MIXED VARIATIONS AND THE EFFECT ON THE CBR UNSOAKED

Ketapang and Kayong Utara Regency have road construction that often suffers damage before the planned life age caused by the behavior of expansive clay. The subgrade is a fundamental structure in building road construction because the subgrade will support traffic loads or construction loads. The strength and durability of the pavement structure road will depend on the properties and bearing capacity of the subgrade. Practically soil stabilization is a reinforcement engineering against foundation or subgrade by using mixed materials. Therefore, different soil improvement variations are needed. Based on the test result, the CBR value of Sukadana initially gets a 2.95% point. The CBR value for the 6% and 10 % mixture, respectively, gets 17.14% and 25.02%. The CBR value of Sungai Melayu Rayak originally get 4.65% point. Then, for the 6% and 10% mixture, the CBR values increased by 13.78% and 18%. The value of the bearing capacity of the highway soil construction can be know from the results of CBR testing on each variation. The CBR also can measure the strength of the soil. The addition of cement to the earth tends to increase the bearing capacity of the ground. It is because cement can function as a binder between soil particles with chemical compounds contained in cement.

Review on Soil Improvement by Using Various Chemical Additives for Foundation

This work aimed to study the most effective chemical additives to increase the strength of the clay soil. The problem statement is to improve the soil strength to avoid failure in the ground. The chemical additives that be used are lime, cement, and fly ash. These chemical additives were commonly used to stabilize the soil and make the shear strength of the soil increase. The data taken was from the previous research, where the data was compared to get the most effective chemical additives to improve the soil stability and soil strength. The percentage of the chemical additive used in the soil mixture was 8% to 10%. The data from previous research was chosen based on the rate used of the chemical additive and the research was taken from Science Directed website only. Data were collected through 30 previous studies using clay and chemical additives such as cement, lime, and fly ash. The data for Plastic Limit, Liquid Limit, Plasticity Index, Optimum Moisture Content, Maximum Dry Density, and Unconfined Compressive Strength was taken by referring to the previous study. Then the data was listed in Microsoft Excel to generate the graph for comparison. All the data obtained are then compared to get which chemicals can increase the strength of the soil. The result of this study shows that the cement was the most effective chemical additive to improve the soil strength and to stabilize the soil than the lime and fly ash.

Strength properties of biopolymer treated clay/marble powder mixtures

Depending on their unique layer structures and chemical structures, soil problems such as swelling, settlement and loss of strength can be seen especially on clay soils when exposed to water. Settlement occurring on clay soils on which the structure is built, causes various damages in the building. Additionally, in the clay soil interacting with water, strength loss occurs due to the effect of the building load. Today, when soil improvement techniques are developed and diversified, clay soils can be stabilized by using different additives. A clay soil that has been improved by adding waste marble powder within the scope of this study in certain percentages (5%, 15%, 25%), biopolymer added clay / marble powder samples were obtained by interacting with locust bean gum in certain percentages (0.5%, 1%, 1.5%). There are many studies in the literature on improving clay soils using only marble powder or only biopolymer. In this study, marble powder and biopolymer were used together and thus, the feasibility of a more effective soil improvement has been investigated. The results showed that the unconfined compressive strength of the biopolymer added clay-marble powder mixtures are higher when compared with natural clay. Similarly, shear box test results showed that the unconsolidated-undrained cohesions and internal friction angles of the doped clay samples increased. It was observed that the strength values of marble powder-added clay increased after improving with biopolymer.

SOIL IMPROVEMENT METHODS USING MINIPILE FOR REDUCING SETTLEMENT VALUE IN HIGHWAY TOLL KERTOSONO – KEDIRI

A highway toll project is an urgent need in this modernization era, especially in our country, which currently has a population of around 250 million people. From the population that has been increasing, In the current era the need for transportation is also growing rapidly, Therefore, a safe and comfortable transportation is needed. Relationship with the occurred of soft soil in the STA. 18 + 000 to STA. 20 + 300, the authors need to provide an analyzing way of handling the soft soil in order to meet the criteria for the settlement criteria. Meanwhile, the purpose of making analysis soft soil improvement using minipile is to find out a technical point still meets the requirements stated in the design criteria. To achieve this goal, analysis of the soft soil improvement in carrying out the analysis and calculations was taken from the results analysis of the N-SPT value and laboratory testing material from the soil investigation of the borehole. The calculation results obtained are in the soil improvement methods at the location which was originally using a minipile it can reduce settlement value < 20 mm/years, safety factor in earthquake condition > 1.10 and time schedule for implementation pilling work on site 1 month faster than the time required when using another methods for each location that has of soft soil content, especially in the section STA. 18 + 000 to STA. 20 + 300.

Water and Heat-Triggered Changes of Bacterial Community Structure and Function in Biological Soil Crusts

Background and Aims：The outstanding ability of biological soil crusts (BSCs) in soil microenvironments regulation is mainly attribute to microorganisms that colonizing in biocrusts. We aimed to investigate the changes of bacterial community structure and function with biocrust succession, as well as their responses to climatic changes across large geographical scales.Methods: Algal BSCs and lichen BSCs were sampled along an aridity gradient on alpine grasslands. Bacterial communities in biocrusts were measured using high-throughput sequencing, and soil underlying biocrusts (0-5 cm) was collected for nutrients determination. Results: Our results indicated that compared with algal BSCs, bacterial community in lichen BSCs was characterized by lower diversity, more complex co-occurrence network and mutually beneficial relationships. The bacterial community assembly was governed mainly by stochastic processes for lichen BSCs, which was different from the almost equally important roles of stochastic and deterministic processes for algal BSCs. Geographical location had a significant effect on bacterial communities in both algal and lichen BSCs, while had a greater effect on lichen BSCs. It is noteworthy that the bacterial diversity of algal BSCs was positively correlated with aridity index, while that of lichens was negatively correlated with aridity index. Moreover, we determined lower soil pH and higher soil phosphorus content underlying lichen BSCs, implying their advantages in soil improvement. Conclusions: Aridity index was one of important driving factors of bacterial community in biocrusts, and its effects were biocrust type dependent. Lichen BSCs had greater effects on soil improvement than that of algal BSCs.