Mode-based equivalent multi-degree-of-freedom system for one-dimensional viscoelastic response analysis of layered soil deposit

Discrete models such as the lumped parameter model and the finite element model are widely used in the solution of soil amplification of earthquakes. However, neither of the models will accurately estimate the natural frequencies of soil deposit, nor simulate a damping of frequency independence. This research develops a new discrete model for onedimensional viscoelastic response analysis of layered soil deposit based on the mode equivalence method. The new discrete model is a one-dimensional equivalent multi-degree-of-freedom（MDOF） system characterized by a series of concentrated masses, springs and dashpots with a special configuration. The dynamic response of the equivalent MDOF system is analytically derived and the physical parameters are formulated in terms of modal properties. The equivalent MDOF system is verified through a comparison of amplification functions with the available theoretical solutions. The appropriate number of degrees of freedom（DOFs） in the equivalent MDOF system is estimated. A comparative study of the equivalent MDOF system with the existing discrete models is performed. It is shown that the proposed equivalent MDOF system can exactly present the natural frequencies and the hysteretic damping of soil deposits and provide more accurate results with fewer DOFs.

Analysis of Water and Soil Quality Characteristics in Turpan City

[ Objective] The study aimed to analyze water and soil quality characteristics in Turpan City. [ Method] According to Drinking Water Hy- gienic Standards （GB5749-2006） and Standards for Irrigation Water Quality （GB5084-2005）, five kinds of water samples collected from a karez, motor-pumped well, canal, village well and Aydingkol Lake in Turpan City as well as two types of soil samples irrigated by the karez and motor- pumped well water were analyzed in quality. [ Remit] Chloride and sulfate content in the village well and Aydingkol Lake water were higher than their limits in Dnnking Water Hygienic Standards, as well as sulfate content in the motor-pumped well and canal water. However, chloride and sul- fate content in the karez water did not exceed their limits. The soil irrigated by the karez water was salinized slightly, and organic matter content was higher; the soil irrigated by the motor-pumped well water was salinized seriously, and organic matter content was lower. [ Conclusion] The karez water is more applicable to farmland irrigation.

Rapid Detection of Oil Pollution in Soil by Using Laser-Induced Breakdown Spectroscopy

Detection of oil pollution in soil has been carried out using laser-induced breakdown spectroscopy（LIBS）. A pulsed neodymium-doped yttrium aluminum garnet（Nd：YAG） laser（1,064 nm, 8 ns, 200 mJ） was focused onto pelletized soil samples. Emission spectra were obtained from oil-contaminated soil and clean soil. The contaminated soil had almost the same spectrum profile as the clean soil and contained the same major and minor elements. However, a C–H molecular band was clearly detected in the oil-contaminated soil, while no C–H band was detected in the clean soil. Linear calibration curve of the C–H molecular band was successfully made by using a soil sample containing various concentrations of oil. The limit of detection of the C–H band in the soil sample was 0.001 mL/g. Furthermore, the emission spectrum of the contaminated soil clearly displayed titanium（Ti） lines, which were not detected in the clean soil. The existence of the C–H band and Ti lines in oil-contaminated soil can be used to clearly distinguish contaminated soil from clean soil. For comparison, the emission spectra of contaminated and clean soil were also obtained using scanning electron microscope-energy dispersive X-ray（SEM/EDX） spectroscopy,showing that the spectra obtained using LIBS are much better than using SEM/EDX, as indicated by the signal to noise ratio（S/N ratio）.

Carbonates and organic matter in soils characterized by reflected energy from 350-25000 nm wavelength

The soil carbon pool which is the sum of soil organic carbon(SOC)and soil inorganic carbon(SIC)is the second largest active store of carbon after the oceans and it is an important component of the global carbon cycle.Hence,accurate estimation of SOC and SIC as important carbon reservoirs in terrestrial ecosystems using fast,inexpensive and non-destructive methods is crucial for planning different climate change policies.The aim of the current research was to examine the effectiveness of Vis-NIR(visible and near-infrared spectroscopy:350-2500 nm)and MIR(mid-infrared spectroscopy:4000-400 cm-1)to characterize and estimate soil organic matter(SOM)and carbonates as main components of soil carbon stocks in Juneqan,Charmahal va Bakhtiari,Iran.To do so,a total of 548 soil samples from this area were collected(October 2015)and analyzed in laboratory(August 2017).In order to develop models capable of predicting SOM and carbonates content,seven spectral preprocessing methods comprising Absorbance(Abs),De-trending(Det),Continuum removal(CR),Savitzky-Golay derivatives(SGD),standard normal variate transformation(SNV),multiplicative scatter correction(MSC)and Normalization by range(NBR)were conducted along with five multivariate methods including Random Forest(RF),Partial Least-Squares Regression(PLSR),Artificial Neural Network(ANN),Support Vector Machine(SVM)and Gaussian Process Regression(GPR).The content of carbonates caused spectral reflectance intensity to augment on several ranges of spectrum and strong absorption feature at 2338 nm in the Vis-NIR and 714,850,870,1796,2150 and 2510 cm-1 in the MIR spectra range.SOM absorbed energy in several ranges,but also showed specific peaks in MIR.Both facts are associated with the structure of carbonates and SOM and its interaction with energy.The best combination of preprocessing and calibration models for carbonates quantification in Vis-NIR spectra was Det/PLSR(R2=0.74,RPD=2.19,RMSE=6.45).For SOM,it was Det/PLSR(R2=0.82,RPD=2.41,RMSE=0.75).The Det/RF(R2=0.87,RPD=2.44,RMSE=0.66)for the quantification of SOM and MSC/RF(R2=0.84,RPD=2.84,RMSE=5.50)for carbonates in MIR spectra range showed the greatest results.The stronger occurrence of spectral bands in MIR as well as the specificity of the absorption features indicated that this range produced better predictions.The obtained results highlighted the significant role of soil spectroscopy technique in predicting SOC and soil carbonates as key components of soil carbon stocks in the study area.Therefore,this technique can be used as a more cost-effective,time saving and nondestructive alternative to traditional methods of soil analysis.

Phosphorus and potassium fertilization in no till southern Brazilian soils

Phosphorus (P) and potassium (K) levels in southern Brazilian (Rio Grande do Sul, RS) soils are largely below the critical concentrations more than four decades after implementation of the officially recommended system. This study aims to evaluate the increase in P and K levels in 0-10 and 0-20 cm deep samples from no-till soils using the Mehlich-1 (M1) and Mehlich-3 (M3) extractants as well as resin methods and to estimate the amount of P2O5 and K2O fertilizers necessary to increase the P and K soil levels by 1 mg·kg-1. The study was conducted in fields cultivated using a no-till system (direct planting) to grow soybeans, wheat, maize, pasture, and cover crops and fertilized with P2O5 and K2O. Soil samples were collected from the 0-10 and 0-20 cm soil layers and analyzed by the M1, M3, and resin methods. The results demonstrated that the P and K levels increased in the 0-10 and 0-20 cm layers. However, the amount of these levels increased depending on the source of phosphate fertilization and on the P and K extraction methods used. The amount of P2O5 fertilization needed to raise the P level by 1 mg·kg-1 was greater in the 0-20 cm layer than in the 0-10 cm layer, and the amount of K2O fertilization needed to raise the K level by 1 mg·kg-1 was higher in the 0-10 cm layer than in the 0-20 cm layer.

Changes in organic C stability within soil aggregates under different fertilization patterns in a greenhouse vegetable field

Knowledge of the stability of soil organic C(SOC)is vital for assessing SOC dynamics and cycling in agroecosystems.Studies have documented the regulatory effect of fertilization on SOC stability in bulk soils.However,how fertilization alters organic C stability at the aggregate scale in agroecosystems remains largely unclear.This study aimed to appraise the changes of organic C stability within soil aggregates after eight years of fertilization(chemical vs.organic fertilization)in a greenhouse vegetable field in Tianjin,China.Changes in the stability of organic C in soil aggregates were evaluated by four methods,i.e.,the modified Walkley-Black method(chemical method),13C NMR spectroscopy(spectroscopic method),extracellular enzyme assay(biological method),and thermogravimetric analysis(thermogravimetric method).The aggregates were isolated and separated by a wet-sieving method into four fractions:large macroaggregates(>2 mm),small macroaggregates(0.25–2 mm),microaggregates(0.053–0.25 mm),and silt/clay fractions(<0.053 mm).The results showed that organic amendments increased the organic C content and reduced the chemical,spectroscopic,thermogravimetric,and biological stability of organic C within soil aggregates relative to chemical fertilization alone.Within soil aggregates,the content of organic C was the highest in microaggregates and decreased in the order microaggregates>macroaggregates>silt/clay fractions.Meanwhile,organic C spectroscopic,thermogravimetric,and biological stability were the highest in silt/clay fractions,followed by macroaggregates and microaggregates.Moreover,the modified Walkley-Black method was not suitable for interpreting organic C stability at the aggregate scale due to the weak correlation between organic C chemical properties and other stability characteristics within the soil aggregates.These findings provide scientific insights at the aggregate scale into the changes of organic C properties under fertilization in greenhouse vegetable fields in China.

Risk assessment of heavy metals in topsoil along the banks of theYangtze River in Huangshi, China

High concentrations of heavy metal in farmland threatens food production and human health. Our study assesses soil quality and the distribution of Cd, Cr, Cu, Zn, Pb and Ni, to identify possible sources of heavy metals along the banks of the Yangtze River in Huangshi. Heavy metal concentrations of 22 topsoil samples were measured using the inductively coupled plasma mass spectrometry instrument and data was analyzed by multivariate statistic approaches. Heavy metal contamination risk assessment was performed using a combination of the Nemerow multi-factor index method, the Hakanson potential ecological risk index method and the Muller index of geo-accumulation method. These methods determined similar results indicating that cadmium(Cd) poses a health risk to residents at the study site while Cr, Cu, Zn, Pb and Ni do not. The Nemerow multi-factor index method demonstrated that 18 samples were heavily polluted, three moderately polluted and one lightly polluted. The Muller index of geo-accumulation method found ten samples were moderately to strongly polluted by Cd, five were moderately polluted, six were lightly to moderately polluted and one was lightly polluted. The Hakanson potential ecological risk index method proved six samples were strongly polluted, seven were moderately polluted and nine were lightly polluted. Since our sampling sites were all in agricultural lands, we recommend the potential ecological risk index method as the most effective given it not only considers the range of pollutants contributing to soil pollution but factors in heavy metals toxicity. We are apt that the source of the high concentrations of Cd found in topsoil is derived from alluvial sediments upstream of the Yangtze River with a high percentage of residual speciation and a low percentage of exchangeable speciation distribution of Cd. This in turns indicates that a high concentration of Cd in soil had little impact on the natural environment. However, 31.9% of the iron-manganese oxides bound speciation indicating that such levels of Cd in soil would be potentially hazardous to the crops, particularly if exposed to a reductive condition.

Evaluation of periglacial landforms and formation of soil properties on the Mount Honaz,SW Türkiye

The main aim of this study is to explain periglacial processes on the summits of Mount Honaz(2571 m a.s.l.),define periglacial landforms,and determine the relationships between morphometric features and topographic factors.Mud circles,stony earth circles,non sorted steps,and non sorted stripes were identified on the summits of Mount Honaz.Pearson's correlation coefficient(r)and linear regression analyses were performed by taking metric measurements from 125 periglacial landforms to describe their morphometric features(length,width,height)of periglacial landforms and explain the relationships between them and topographic factors(elevation,slope).To explain the relationships between periglacial landforms and soil properties,soil samples from 11 periglacial landforms were taken and analysed.Periglacial landforms,which continue to develop on the summits of Mount Honaz today,have been evaluated with present climate data.Analysis of soil samples indicates a notable impact of parent material on the genesis of periglacial landforms.The high ratio of organic matter in mud circle and non sorted step landforms and the high lime ratio in stony earth circle landforms prove a strong relationship between the formation mechanisms of landforms and the soil properties.Furthermore,it is consistent with the findings obtained from the analysis that severe periglacial processes and washing and scavenging events are experienced more on the northern slopes.

土钉墙技术及其发展前景

对土钉墙技术及其发展过程、分类、工作机理进行分析和归纳,介绍了利用土钉墙技术加固边坡的作用原理、土钉墙的应用现状和存在的问题,对喷锚、锚杆、加筋土挡墙进行了对比,展望了土钉墙技术的发展前景。

Ecological features of Aconitum balfourii (Bruhl) Muk.-an endangered medicinal plant in the northwest Himalaya

Aconitum balfourii （Bruhl） Muk. （Ranunculaceae） is an en- dangered medicinal plant. Natural populations were surveyed in the northwest Himalaya for population estimation and evaluation of elite germplasm. Vegetation sampling of quadrats was conducted using the vertical belt transect method in areas supporting A. balfourii. Plant den- sity and relative dominance ofA. balfourii were low compared with other alpine species. Threat status was determined on a site-by-site basis as well as for entire western Himalaya..4. balfourii was generally classified as endangered on the basis of geographic distribution and critically en- dangered on the basis of abundance. We found the natural geographic distribution of.4. balfourii to be diminishing due to habitat destruction. Immediate corrective management measures are needed for sustainable utilization and long-term conservation of the species in the wild.

Influence of Environmental Variables on the Natural Regeneration of a Forest under Restoration after Bauxite Mining and in a Reference Ecosystem in Southeastern Brazil

The shrub-tree floristic composition of the natural regeneration stratum of a bauxite mine in the process of restoration and in a reference ecosystem(remnant of a preserved secondary Seasonal Semi-Deciduous Forest)were analysed to evaluate forest restoration conditions after five years of planting.The influence of canopy openness,accumulated leaf litter and soil attributes in the regeneration stratum were also investigated in both the forests.The floristic composition of the regeneration stratum in the forest under restoration(16 species and 5,083 individuals ha-1)and in the reference ecosystem(58 species and 26,250 individuals ha-1)are distinct due to the difference in the environmental variables.Results showed that the reference ecosystem favours the presence of species that tolerate environments with greater shading and higher aluminium and organic matter content in the soil like Psychotria carthagenensis Jacq.,while the forest under restoration favours the presence of species adapted to fertile soils and those that tolerate greater luminosity like Vernonanthura phosphorica(Vell.)H.Rob.

土工合成材料试验工作中的决策分析方法和数据再现性

土工合成材料试验指标值与它应用效果密切相关。指标值需要应用决策分析的方法最终确定。而粗集理论则能为它提供一种较好的决策分析方法，对日前试验指标值间进行相关或比较及一致性程度的统计分析时，要先考察其来源和试验数据的再现性是否符合要求。

A Probabilistic Liquefaction Hazard Assessment for Urban Regions Based on Dynamics Analysis Considering Soil Uncertainties

Earthquake induced liquefaction is one of the main geo-disasters threating urban regions, which not only causes direct damages to buildings, but also delays both real-time disaster relief actions and reconstruction activities. It is thus important to assess liquefaction hazard of urban regions effectively and efficiently for disaster prevention and mitigation. Conventional assessment approaches rely on engineering indices such as the factor of safety(FS) against liquefaction, which cannot take into account directly the uncertainties of soils. In contrast, a physics simulation-based approach, by solving soil dynamics problems coupled with excess pore water pressure(EPWP) it is possible to model the uncertainties directly via Monte Carlo simulations. In this study, we demonstrate the capability of such an approach for assessing an urban region with over 10 000 sites. The permeability parameters are assumed to follow a base-10-lognormal distribution among 100 model analyses for each site. A dynamic simulation is conducted for each model analysis to obtain the EPWP results. Based on over 1 million EPWP analysis models, we obtained a probabilistic liquefaction assessment. Empowered by high performance computing, we present for the first time a probabilistic liquefaction hazard assessment for urban regions based on dynamics analysis, which consider soil uncertainties.

Alkaline hydrolyzable nitrogen and properties that dictate its distribution in paddy soil profiles

Nitrogen(N) is a key nutrient for rice production, and its bioavailability in paddy soils is strongly coupled to soil organic matter(SOM) cycling. A better understanding of potentially available N forms in soil, such as alkaline hydrolyzable N(AH-N), and their depth distribution will support the development of best management practices to improve the N use efficiency of rice while minimizing adverse environmental effects. Fifteen rice(Oryza sativa L.) fields from Southern Brazil were selected, and stratified soil samples were taken to a depth of 60 cm before crop establishment. Selected soil physical and chemical properties were analyzed to evaluate their relationships with AH-N contents in the soil profile. The AH-N contents below 20 cm varied extensively(increased,reduced, or constant) compared with that above 20 cm. Although clay and clay + silt contents were highly correlated to AH-N for some soils, the major property dictating AH-N distribution by depth was total N(TN), as the correlation between TN and AH-N was mainly by direct effect. The proportion of TN recovered as AH-N across sites and depths presented high amplitude, and thus AH-N was not a constant N pool across depths, indicating that AH-N can be affected by soil management practices even when TN showed no major changes. The distinct distribution of AH-N across soil sampling sites and depths indicates that depths greater than 20 cm should be considered when calibrating the AH-N index for N fertilizer recommendations for flooded rice in Southern Brazil.

Proximal sensor-enhanced soil mapping in complex soil-landscape areas of Brazil

Portable X-ray fluorescence(pXRF) spectrometry and magnetic susceptibility(MS) via magnetometer have been increasingly used with terrain variables for digital soil mapping. However, this methodology is still emerging in many countries with tropical soils. The objective of this study was to use proximal soil sensor data associated with terrain variables at varying spatial resolutions to predict soil classes using the Random Forest(RF) algorithm. The study was conducted on a 316-ha area featuring highly variable soil classes and complex soil-landscape relationships in Minas Gerais State, Brazil. The overall accuracy and Kappa index were evaluated using soils that were classified at 118 sites, with 90 being used for modeling and 28 for validation. Digital elevation models(DEMs) were created at 5-, 10-, 20-, and 30-m resolutions using contour lines from two sources. The resulting DEMs were processed to generate 12 terrain variables. Total Fe, Ti, and SiO_(2) contents were obtained using pXRF, with MS determined via a magnetometer. Soil class prediction was performed using the RF algorithm. The quality of the soil maps improved when using only the five most important covariates and combining proximal sensor data with terrain variables at different spatial resolutions. The finest spatial resolution did not always provide the most accurate maps. The high soil complexity in the area prevented highly accurate predictions. The most important variables influencing the soil mapping were MS, Fe, and Ti. Proximal sensor data associated with terrain information were successfully used to map Brazilian soils at variable spatial resolutions.