Cumulative Mass Loss Research Articles

Dynamic of fungal community composition during maize residue decomposition process in north-central China

Crop residue decomposition is a process largely mediated by soil microbes. This study aimed to investigate the dynamic of crop residue decomposition, change in fungal community composition and extracellular enzymatic activity in maize (Zea mays L.) residue via utilization of a two-year residue-bags study in north-central China. After the residue was buried in soil, the cumulative residue mass loss rate was 33%, 74%, and 85% after 2, 12, and 24 months, respectively. Total fungal abundance and the activities of beta (β)-glucosidase, β-d-cellobiosidase, and β-xylosidase were greater at the initial stage of decomposition and gradually decreased over time. However, the phenol oxidase activity presented an opposite pattern relative to the hydrolytic enzymes. The fungal community composition was similar in the residue during the initial (0) and 2 months after, with the phylum Ascomycota (classes Sordariomycetes and Dothideomycetes) dominating the community composition for the first two months but then decreased gradually over time. Phyla Basidiomycota, Cercozoa, and classes Eurotiomycetes and Tremellomycetes presented an increasing-decreasing trend during the decomposition process. The phylum Zygomycota (class Leotiomycetes) gradually increased over time and showed greater abundance at the later stage of decomposition; while the fungal community composition was similar in soil and residue samples for the 20–24 months. This study highlights the relevancy of fungal abundance for playing a critical role in residue decomposition, with the composition of this community changing from the dominance of copiotrophic populations in the early stage to oligotrophic populations in the later stage.

Cross‐linked polymers increase nutrient sorption in degraded soils

AbstractCross‐linked polymer hydrogels, polyacrylamide co‐polymer (XPAM) or polyacrylate (XPAA) offer potential solutions for soil degradation, declines in soil resilience, and poor productivity in marginal soils. However, little is known about their long‐term effect on soil nutrient availability. This 9‐yr, irrigated, outdoor, cropped pot study evaluated a single, one‐time addition of XPAM or XPAA at 0.25 or 0.5% dry wt. (5.6 or 11.2 Mg ha–1) in a degraded (artificially eroded) soil. Controls included an unamended degraded soil and an unamended, non‐degraded soil (i.e., topsoil). We measured nutrients in soil and leachate water each year, and in the first 5 yr, crop yields and nutrient uptake. Both hydrogels increased average soil pH and electrical conductivity (EC), soil extractable K, Na, and total organic carbon (TOC), and decreased soil extractable Mg relative to the control. Unlike XPAM, XPAA produced a greater increase in soil extractable K, increased extractable Fe, Zn, Mn, and Cu, increased Olsen P, and decreased total inorganic carbon (TIC). Neither hydrogel affected crop yields but XPAA increased K and Zn and decreased Mg and Na uptake in crops compared to controls. Relative to the control, both hydrogels decreased cumulative Ca, Mg, and S leaching mass losses and increased mean EC of leachate. Unlike XPAM, XPAA increased cumulative leaching mass losses of K, P, NO3–N, and NH4–N relative to the control. The hydrogels’ soil effects persisted for ≥7 yr, differing as a function of the quantity of included counterions and the stability of the gel structure after soil placement.

Effects of WC on the cavitation erosion resistance of FeCoCrNiB0.2 high entropy alloy coating prepared by laser cladding

To improving the cavitation erosion resistance (Re) of the FeCoCrNiB0.2 high entropy alloy (HEA), the FeCoCrNiB0.2 + WC (0 wt.%, 20 wt.%) HEA coatings were synthesized with premixed high-purity on Q235 steel by laser cladding (LC). The effects of WC on the hardness and Re were investigated. The cavitation erosion (CE) behavior in distilled water and 3.5 wt.% NaCl solution and microhardness were evaluated using an ultrasonic vibrator and Microscopy/Vickers hardness tester. The cavitation mass loss and surface morphology were used to characterize the cavitation damage. Experimental results showed that the Vickers hardness of FeCoCrNiB0.2 + 20 wt.% WC coating was higher than that of FeCoCrNiB0.2 coating, and the cumulative mass loss of FeCoCrNiB0.2 + 20 w.t% WC coating was less than that of FeCoCrNiB0.2 coating. The presence of chloride ion interacts with CE, forming a combined cavitation-corrosion damage, which accelerates the removal of material from the surface. Adding 20 wt.% WC, the number of cavitation pits was significantly reduced and the depth of pits also became shallower, which means that the addition of WC could weaken the degree of cavitation damage.

Cavitation erosion behaviour of AISI 420 stainless steel subjected to laser shock peening as a function of the coverage layer in distilled water and water-particle solutions

Influences of the coverage layer on cavitation erosion (CE) behaviour, cavitation-silt erosion (CSE) behaviour and damage morphologies of AISI 420 steel subjected to massive laser shock peening treatment (MLSPT) was studied through mass loss measurement, scanning electron microscopy observation, microstructure characterization, and residual stress measurement. Results showed that original martensitic laths with an average width of 450 nm were refined into fine equiaxed grains of 94–220 nm under the mechanical effect of ultra-strong laser shock wave. Moreover, MLSPT induced a compressive residual stress layer up to 1 mm deep, and the surface residual stress was up to −400 MPa. In addition, the average cumulative mass losses of LSPed specimens were respectively 42.2% and 26.5% lower than that of the non-treated specimen in distilled water and water-particle solution, and the erosion resistance was significantly improved with increasing the coverage layer due to the MLSPT-induced grain refinement and compressive residual stresses in the surface layer.

Dynamic modeling of chemical membrane degradation in polymer electrolyte fuel cells: Effect of pinhole formation

The continuous chemical degradation of the polymer membrane in polymer electrolyte fuel cells causes membrane pinhole formation, therefore substantial increase in the gas cross-over flux. In this paper, a numerical method to simulate the pinhole formation process during chemical degradation is proposed. The method assumes that a membrane pinhole is formed by connected local micro-pores, which are generated owing to the mass loss during chemical membrane degradation. In addition, pinhole formation is combined with reduction of the membrane thickness to account for the membrane structure changes. A dynamic chemical degradation model that incorporates the effects of membrane structure changes is validated against the experimental results of the accelerated stress test. Results confirm the proposed method increases the accuracy of the chemical degradation model in predicting the macroscopic properties, including cumulative mass loss, hydrogen cross-over and open circuit voltage. Formation of pinhole starts from the anode, where degradation is more severe, and propagates to the cathode. The model also systemically studies the effects of temperature, pressure, and relative humidity on chemical degradation. The degradation rate increases with elevated temperatures and pressures. The degradation is shown to be more severe at moderate relative humidity, and the comparison with experimental findings are discussed.

Influencing Factors and Prediction Model for the Antierosion Performance of Cement‐Improved Loess Compacted Using Different Compaction Methods

To analyze the antierosion performance of cement‐improved loess (CIL), several influencing factors have been investigated based on two different compaction methods, which include the quasi‐static compaction method (QSCM) and the vertical vibration compaction method (VVCM). Then, a prediction model for the cumulative erosion mass loss (CEML) has been established. The effects of erosion on the strength deterioration of CIL were also studied. The results show that, compared with QSCM, specimens compacted using the VVCM have better antierosion performance. As the cement content and the compaction coefficient are increased by 1%, the antierosion performance is increased by 16% and 6.2%, respectively. The eroding time has a significant effect on the antierosion performance of CIL, and the CEML increases linearly with an increase in the eroding time. The compressive strength of CIL decreases significantly due to erosion, and based on the average deterioration degree of the specimens, the design criteria for strength of CIL are proposed, which can provide reference for the design of CIL.

Durability Evaluation of Concrete with Multiadmixtures under Salt Freeze‐Thaw Cycles Based on Surface Resistivity

According to the climatic characteristics of seasonal frozen area in northeast China, the concrete strength tests, surface resistivity, rapid chloride permeability, and freeze‐thaw test under salt solution were carried out to study the influences of mineral admixtures and air content on the conventional properties and salt freeze‐thaw resistance of concretes. Then, the correlation analysis of surface resistivity with strength and rapid chloride permeability were further investigated. Subsequently, the changes of cumulative mass loss and relative dynamic elastic modulus varying with salt freeze‐thaw cycles were analyzed to study the influences of mineral admixtures and air content on salt freeze‐thaw resistance of concrete. The test results showed that fly ash (FA) was not conducive to improve the strength and salt freeze‐thaw resistance of concrete. However, blast furnace slag (BFS) and silica fume (SF) could improve the compressive and flexural strength of concrete, in which SF can improve its strength more significantly. Increasing the air content of concrete will lead to the reduction of its compressive strength, and the flexural strength first increased and then decreased. Nevertheless, the addition of air‐entrainment agent (AEA) has the best effect on improving the salt freeze‐thaw resistance of concrete. Moreover, surface resistivity of concrete has a good exponential function relationship with strength and a good power function relationship with rapid chloride permeability. Therefore, it is of great significance for engineering quality control and quickly and nondestructive testing.

Polyurethane coating with heterogeneity structure induced by microphase separation: A new combination of antifouling and cavitation erosion resistance

Cavitation erosion and biofouling are the most severe factors of metal materials fatigue failure and degradation in seawater. Herein, a series of hydrophobic fluorinated polyurethane coatings (SFPU-x) with various contents of fluorinated isocyanate prepolymer (FIP) were synthesized via a simple addition reaction for anti-cavitation erosion property combined with biofouling resistance. The microstructure and phase composition of as prepared coatings were analyzed by ATR-IR, SEM, TG, EDS and AFM. The addition of FIP increases the content of hard segments microregion and affects the microphase separation of the coating and induces the construction of surface heterogeneity microstructures. The static water contact angle and water absorption were measured as well. The antifouling tests were conducted using Nitzschia Closterium cell and the fluorescence labeled bovine serum albumin (FITC-BSA) as fouling models. Especially, the SFPU-5 coating with 5% FIP shows excellent antifouling and cavitation erosion resistance abilities due to surface heterogeneity microstructure, the attachment rates of FITC-BSA (1.1 %) and Nitzschia cell (1.3 %) far less than that of SFPU-0 coating (72.3 % and 85.1 %), respectively. Marine field test for 30 days also proven the antifouling properties of the SFPU-5 coating. In addition, there were no obvious holes and cracks on the surface of SFPU-5 after 10 h of cavitation, the cumulative mass loss were 2.7 mg and 2.9 mg in deionized water and in seawater, respectively.

Cavitation erosion behavior of nitinol coating sealed by epoxy resin

AbstractThe nitinol coating against cavitation erosion was prepared by air plasma spraying and sealed with epoxy resin successfully. After the coating sealed with epoxy resin, the pores and cracks of the coating were filled with the epoxy resin and then the cohesiveness between the lamellae was improved, the hardness increased from 3.68 GPa to 7.49 GPa, the energy recovery ratio (superelasticity) was improved from 41.9 % to 49.0 % and the toughness was enhanced from 0.011 GPa to 0.045 GPa. During the cavitation erosion test, the epoxy resin reduced the cavitation resources and absorbed the impact energy from the micro‐jet or shock waves. Meanwhile, the high hardness and superelasticity can help the coating to resist cavitation erosion and the high toughness can delay the expansion of cracks during the cavitation erosion test. As a result, after cavitation erosion for 300 min the cumulative mass loss of the coating sealed by epoxy resin was 1/5 times as much as that of the nitinol coating without sealing. Therefore, the cavitation erosion resistance of the nitinol coating can be improved by sealed with epoxy resin.

Cavitation erosion behavior of microwave-processed Ni–40Cr3C2 composite clads: A parametric investigation using ultrasonic apparatus

Cavitation erosion is the primary cause of material failure of the hydroelectric power plant components. The rapid development in the advanced surface engineering techniques has provided an effective treatment solution for cavitation erosion. One such novel method is microwave cladding. Hence, the Ni–40Cr3C2 composite clad was deposited on austenitic stainless steel (SS-316) using a microwave cladding process in the present study. The processing was carried out in a domestic microwave oven of 2.45 GHz frequency and 900 W power. The developed clad was thoroughly characterized for the metallurgical and mechanical properties related to its behavior as a successful cavitation erosion resistance material, like microstructure, crystal structure, porosity, microhardness, flexural strength, and fracture toughness. The results showed that the stripe-type and agglomerated carbides were present in the Ni–40Cr3C2 clad. The developed composite clad consists of various carbides (SiC, Ni3C, Cr3Ni2SiC, Cr7C3, and NiC) and intermetallic phases (Ni3Fe, Ni2Si, and Cr3Si). Microhardness, flexural strength, and fracture toughness of the microwave-processed clad were observed to be 605 ± 80 HV0.3, 813.23 ± 16.2 MPa, and 7.44 ± 0.2 MPa√m, respectively. The microwave-processed composite clad performance in terms of cavitation erosion resistance was determined using the ultrasonic apparatus (ASTM-G32-17). The cavitation experiments were carried out according to Taguchi L9 orthogonal array, taking into account three parameters: standoff distance, amplitude, and immersion depth. The developed composite clad exhibited significant resistance (mass loss 7.6 times lesser as compared to SS-316) to cavitation erosion. ANOVA results showed the standoff distance as the most important factor followed by amplitude and immersion depth. Least cavitation resistance was observed at a smaller standoff distance, higher amplitude, and lower immersion depth. Linear regression equations were obtained to establish the correlation between parameters and cumulative mass loss. The microwave clad specimens tested at optimized test parameters were damaged in the form of fractured intermetallic, extruded lips, pits, and craters.

The satellite observed glacier mass changes over the Upper Indus Basin during 2000\u20132012

Decadal glacier thickness changes over the Upper Indus Basin in the Jammu and Kashmir Himalaya were estimated using the TanDEM-X and SRTM-C Digital Elevation Models (DEMs) from 2000 to 2012. In the study area 12,243 glaciers having 19,727 ± 1,054 km2 area have thinned on an average of − 0.35 ± 0.33 m a−1 during the observation period. The highest thinning of − 1.69 ± 0.60 m a−1 was observed in the Pir Panjal while as the marginal thinning of − 0.11 ± 0.32 m a−1 was observed for the glaciers in the Karakoram. The observed glacier thickness changes indicated a strong influence of the topographic parameters. Higher thickness reduction was observed on the glaciers situated at lower altitudes (− 1.40 ± 0.53 m a−1) and with shallower slopes (− 1.52 ± 0.40 m a−1). Significantly higher negative thickness changes were observed from the glaciers situated on the southern slopes (− 0.55 ± 0.37 m a−1). The thickness loss was higher on the debris-covered glaciers (− 0.50 ± 0.38 m a−1) than on the clean glaciers (− 0.32 ± 0.33 m a−1). The cumulative glacier mass loss of − 70.32 ± 66.69 Gt was observed during the observation period, which, if continued, would significantly affect the sustainability of water resources in the basin.

Tracking of disc cutter wear in TBM tunneling: a case study of Kerman water conveyance tunnel

Disc cutters are the dominant cutting tools used in tunneling by rock TBMs. During the operation, disc cutters wear out and should be replaced with new ones. The wear rate of the disc cutters can be defined in terms of rolling distance/time and volumetric wear. Furthermore, the wear rate can be attributed to the mass loss. The wear prediction models for disc cutter have been developed on the basis of the intact rock abrasion indices, most commonly Cerchar abrasivity index (CAI). Examination of these models and comparing their results with actual wear observed in the Kerman water conveyance tunnel (KWCT) project show that the available models are conservative. In other words, reliance only on the intact rock abrasion does not offer an accurate prediction of the wear rate of the disc cutter. Therefore, rock mass conditions should also be considered in the calculations. The current study shows that volumetric mass loss is a more appropriate method to predict wear life of disc cutters due to consideration of various geometric parameters such as spacing between disc cutters, penetration rate, installation radius, and bored length. Subsequently, a new empirical prediction model is proposed by nonlinear multivariable regression based on CAI as a rock material parameter and RQD (rock quality designation) as a rock mass parameter to estimate the cumulative volumetric mass loss of disc cutters. For ease of using the model, a chart is introduced that determines the wear on the disc cutters based on the CAI and RQD.

Cavitation-corrosion behaviors of HVOF sprayed WC-25WB-10Co-5NiCr and MoB-25NiCr coatings

Cavitation erosion, corrosion and synergism behaviors of HVOF sprayed WC-25WB-10Co-5NiCr and MoB-25NiCr coatings were investigated in this study. Conventional WC-10Co-4Cr and Cr3C2-25NiCr coatings were also characterized for comparison purposes. The cavitation erosion and cavitation-corrosion experiments were carried out in deionized water and 3.5 wt% NaCl solution respectively. The average mass loss rate was defined to assess the destruction of the coating surface. The cavitation erosion resistance and the cavitation-corrosion resistance were adopted to quantitatively analyze the difference of cavitation erosion and cavitation-corrosion performance of the coatings. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were employed to evaluate the corrosion resistance of all the coatings. In addition, the equivalent circuit models were designed to fit the EIS. The cumulative mass loss of all the coatings was measured under the conditions of pure cavitation erosion, pure corrosion and cavitation-corrosion. The total mass loss rate, pure cavitation rate, pure corrosion rate as well as synergistic mass loss rate were calculated to discuss their relative contributions responsible for the material removal. The cavitation-corrosion mechanisms were also discussed by analyzing the eroded surface for all the coatings.

Assessment of the Cavitation Resistance of Stainless Steel X5crni18-10, Subjected to Thermal Sensitization Based on Average Durability

Among the uses of stainless steel GX5CrNi18-10 one mentions the hydraulic machine blades and the rotors, which are highly susceptible to cavitation. To achieve a long life service under cavitation conditions, the pieces made of this steel are subjected to volumetric thermal treatments, which change the structure and mechanical properties. In this paper, one presents the results of the research concerning the behavior and the resistance to the cavitation erosion of the thermally sensitized GX5CrNi18-10 stainless steel, applying four different temperature regimes (two at 650°C and two at 750°C) and different durations (30 minutes and respectively 60 minutes). The results are presented in the form of cumulative mass loss curves M (t) and erosion rate v (t). The assessment of the cavitation resistance provided by each heat treatment regime is based on the average durability cavitation parameter, as defined by K. Steller. The research was conducted on the standard vibrator with piezo-ceramic crystals from the Cavitation Laboratory of the Politechnica University of Timisoara.

Comparative investigation of ultrasonic cavitation erosion for three materials in deionized water

To investigate the response of material to cavitation erosion, a comparative work was carried out on three materials, aluminum, copper alloy and titanium. Ultrasonic cavitation erosion was produced as the specimen was submerged in the deionized water. Within a cavitation erosion period of 120 min, the cumulative mass loss was measured at certain time intervals. Surface structure and cavitation damage patterns were observed for the three materials. Microhardness was measured and compared. The results indicate that the cumulative mass loss of aluminum is the highest among the three materials, while the slightest material removal is associated with titanium, which is still in the initial stage of cavitation erosion after 120 min of cavitation erosion. The surface of the aluminum specimen is eroded rapidly after the cavitation erosion commences. Large erosion pits dominate the eroded surface as the cavitation erosion progresses. The surface of the titanium specimen manifests needle-like erosion pits and cleavage cracks. Even at the later stage of the cavitation erosion, non-eroded surface elements are identifiable. The cavitation erosion pattern on the copper alloy specimen surface is related to the twin-phase crystal structure and large erosion pits are produced at the later stage of cavitation erosion. The highest resistance to the cavitation erosion of titanium is related to the close-packed hexagonal structure and the weak slip effect associated.

Cadmium influences the litter decomposition of Solidago canadensis L. and soil N-fixing bacterial communities.

It is important to illuminate the effects of litter decomposition of invasive alien species on soil N-fixing bacterial communities (SoNiBa), especially under heavy metal pollution to better outline the mechanisms for invasion success of invasive alien species. This study attempts to identify the effects of litter decomposition of Solidago canadensis L. on SoNiBa under cadmium (Cd) pollution with different concentrations (i.e., low concentration, 7.5mg/kg soil; high concentration, 15mg/kg soil) via a polyethylene litterbags-experiment. Electrical conductivity and total N of soil were the most important environmental factors for determining the variations of SoNiBa composition. S.canadensis did not significantly affect the alpha diversity of SoNiBa but significantly affect the beta diversity of SoNiBa and SoNiBa composition. Thus, SoNiBa composition, rather than alpha diversity of SoNiBa, was the most important determinant of the invasion success of S.canadensis. Cd with 15mg/kg soil did not address distinct effects on alpha diversity of SoNiBa, but Cd with 7.5mg/kg soil noticeably raised the number of species and species richness of SoNiBa mainly due to the hormonal effects. The combined S.canadensis and Cd with 15mg/kg soil obviously decreased cumulative mass losses and the rate of litter decomposition (k) of S.canadensis, but the combined S.canadensis and Cd with 7.5mg/kg soil evidently accelerated cumulative mass losses and k of S.canadensis. Thus, Cd with 7.5mg/kg soil can accelerate litter decomposition of S.canadensis, but Cd with 15mg/kg soil can decline litter decomposition of S.canadensis.

Invertebrate phenology modulates the effect of the leaf economics spectrum on litter decomposition rate across 41 subtropical woody plant species

Abstract Litter quality and decomposers are critical to carbon and nutrient cycling through litter decomposition. However, how relationships between litter quality and invertebrate detritivores change litter mass loss through time is poorly known. Species’ initial leaf litter quality, as a legacy of their position on the ‘leaf economics spectrum’ (LES), may determine the invertebrate contribution to litter mass loss. This contribution may change through time, as both population peaks of invertebrate detritivores and litter quality of given species will change through time. Here we introduce invertebrate phenology into a conceptual model of drivers of litter mass loss. We hypothesized that in the early decomposition period, LES can predict litter decomposability with or without a strong invertebrate contribution, that is, litter with higher nutrient content would decompose faster. But in the later decomposition period, when higher quality litter will already have decomposed too much and lower quality litters have still been less degraded, a strong invertebrate peak would coincide with relatively more consumption of initially lower quality litters; this would lead to a humpback relationship between leaf litter mass loss and initial LES position in this period. We tested our hypothesis through a 1‐year field decomposition experiment using leaf litter of 41 woody species in each of two sites in subtropical forest in China; only one of these sites had a strong late peak of leaf litter‐feeding moth larvae in the litter layer. LES score of litter species had a positive linear relationship with litter mass loss before the key invertebrate consumer peaks in the litter layer. However, with the invertebrates peaking later into the decomposition process, the invertebrate consumption peaked at initially lower quality litters, which altered the species’ decomposability trajectory on the LES, consistent with the hypothesized humpback relationship between leaf litter mass loss and LES. This phenomenon resulted in a strongly reduced slope of cumulative mass loss on initial LES score across species. Our finding highlights the importance of considering interactions between the timing of detritivore activities and the timing of litter quality for better understanding the relationships between soil animals and ecosystem carbon and nutrient cycling. A free Plain Language Summary can be found within the Supporting Information of this article.

Resistance of thermally modified and pressurized hot water extracted Scots pine sapwood against decay by the brown-rot fungus Rhodonia placenta

The thermal degradation of wood is affected by a number of process parameters, which may also cause variations in the resistance against decay fungi. This study compares changes in the chemical composition, water-related properties and decay resistance of Scots pine sapwood that was either thermally modified (TM) in dry state at elevated temperatures (≥ 185 °C) or treated in pressurized hot water at mild temperatures (≤ 170 °C). The thermal decomposition of easily degradable hemicelluloses reduced the mass loss caused by Rhodonia placenta, and it was suggested that the cumulative mass loss is a better indicator of an actual decay inhibition. Pressurized hot water extraction (HWE) did not improve the decay resistance to the same extent as TM, which was assigned to differences in the wood-water interactions. Cross-linking reactions during TM caused a swelling restraint and an effective reduction in moisture content. This decreased the water-swollen cell wall porosity, which presumably hindered the transport of degradation agents through the cell wall and/or reduced the accessibility of wood constituents for degradation agents. This effect was absent in hot water-extracted wood and strong decay occurred even when most hemicelluloses were already removed during HWE.

Durability of silty soil stabilized with recycled lignin for sustainable engineering materials

Lignin is an industrial waste derived from the paper plant, which poses a potential threat to the surrounding environment without proper disposal. The present study aims to evaluate the durability performance of recycled lignin stabilized silty soil subjected to different adverse environments. A series of laboratory experiments were conducted to determine unconfined compressive strength (qu), moisture stability coefficient (Kr), mass loss (Sm) and pH value of the stabilized silt exposed to water soaking and wetting-drying cycles. The results showed that the strength and durability of natural silt were obviously improved with the inclusion of lignin. Lignin cementation and matrix suction played important roles in the strength behavior of the unsaturated stabilized silt. The compressive strength suffered a dramatic drop after 1 day of soaking due to the dissolution of cementing materials and the loss of suction. Lignin stabilized silt possessed a higher Kr than that of quicklime stabilized one, indicating its superiority in durability. After 28 days of standard curing, 12% lignin stabilized silt had an ability to resist 4 cycles of wetting-drying, resulting in the cumulative mass loss (Cm) of approximately 20%. Soil pH value presented a decreasing trend with wetting-drying cycles, and an exponential correlation of pH with Cm was found by data fitting. Scanning electron microscope analysis revealed that the lignin-based cementing materials are gradually lost during the process of wetting-drying cycles. Additional research is encouraged to explore an effective method to prevent the deterioration of mechanical properties of lignin stabilized soils in practical projects.

Simultaneous control of soil erosion and arsenic leaching at disturbed land using polyacrylamide modified magnetite nanoparticles

Rapid urbanization and human disturbance of land often results in serious soil erosion and releases of fine sediments and soil-bound toxic metals/metalloids. Yet, technologies for simultaneously controlling soil erosion and metals/metalloids leaching have been lacking. This study developed a new class of polyacrylamide-dispersed magnetite (PAM-MAG) nanoparticles and tested the effectiveness for simultaneous control of soil erosion and arsenic leaching from a model soil. Two parallel box test setups (L × W × H: 91.4 × 30.5 × 7.6 cm) were constructed to test the releases of sediments and soluble pollutants from the surface soil under simulated rainfall conditions (intensity = 11.15 cm/hr). A sandy loam soil from a local quarry mining site was used as the model soil, and arsenate As(V) as a prototype leachable metalloid. A stable dispersion of PAM-MAG was prepared with 0.3 wt% of PAM and 0.1 g/L as Fe of magnetite. The results indicated that treating the soil with 5.985 g/m2 of PAM-MAG was able to decrease cumulative soil mass loss in the runoff by 90.8% (from 254.50 ± 0.10 g to 23.35 ± 3.19 g), or turbidity of the runoff by 79.9% (from 244.5 ± 27.5 NTU to 49.2 ± 22.5 NTU). Compared to PAM only, the PAM-MAG suspension showed a 30% reduction of viscosity, allowing for easier application and transport of the nanoparticles in soil. Concurrently, the PAM-MAG treatment also immobilized 82.5% of water-leachable arsenate compared to untreated controls. Fourier-transform infrared (FTIR) spectroscopy analyses revealed that arsenate was immobilized by magnetite nanoparticles through inner sphere surface complexation (Fe-O-As). Overall, the PAM-MAG based technology holds the promise for simultaneously controlling soil erosion and metal/metalloid releases from disturbed land.