The coefficient of variation representing the non-uniformity of the strain field and its implication to detect earthquake precursor

Before the major earthquake or rock damage occurs,it is often accompanied by a sudden change in the degree of non-uniformity of the strain field.In order to find a stronger non-uniformity signal before the rock failure,the coefficient of variation(Cv)is examined and reformed in this study.We test the Cv calculation way of the"normal-abnormal"model proposed in the previous studies.Based on the analysis of the physical process of rock failure and its relationship to the shear strain field,we construct a new way to calculate the Cv value.The variation of shear strain field on rock sample with the increase of stress is obtained by the digital speckle correlation method(DSCM).The new Cv value calculation way is used to study the non-uniformity of the spatial distribution for the shear strain field.The results show that this Cv calculation way can get more obvious abnormal signals.When the number of observation points are limited,the specific distribution of points can increase the signal strength,which may provide reference for the research on precursor detection of earthquakes.

Method for calculating non-point source pollution distribution in plain rivers

The land area in a river network is divided into certain-scale square cells for the sake of precision, and, based on the physical mechanisms of rainfall-runoff processes and runoff pollution, the non-point source pollution from cells is estimated using the export coefficients of different land use types. The non-point source pollution from a land cell should all go into the closest fiver reach, so it is distributed according to the terrain of the plain river network area and the positions of land cells and river network reaches. A relationship between a single land cell and its pollution-receiving reach can be determined using this system. In view of the above, a spatial distribution model of the rainfall runoff and non-point source pollution in reaches of a plain river network area was established. This model can provide technological support for further research on the dynamic effects of non-point source pollution on water quality.

Modelling spatial variation in the treatment costs of nonpoint source pollution in mountainous regions of southwest China

Non-point source(NPS) pollution is considered to be one of the main threats of the aquatic environment. Mountainous regions are particularly important water sources for urban areas. The various driving factors of NPS pollution such as terrain, precipitation, and vegetation type in mountainous regions show clear spatial heterogeneity. Consequently, the management systems required for NPS pollution in mountainous regions are complex. In this study, we developed a framework to estimate and map the treatment costs for NPS pollution in mountainous regions and applied this method in Baoxing County, a typical mountainous county in Sichuan Province of southwest China. The export levels of total nitrogen(TN) and total phosphorus(TP) in Baoxing County were estimated using the water purification model in InVEST(Itegrated Valuation of Ecosystem Services and Tradeoffs) tool. NPS pollutant treatment costs were calculated based on the level of pollutants exports, water yield, water quality targets, and treatment costs of NPS pollutants per unit mass. The results show that at the watershed level the amounts of TN and TP exported in Baoxing County were below threshold limits. However, at the sub-watershed level, TN and TP excesses of 291.64 and 2.96 tons per year were found, respectively, with mean TN and TP treatment costs of 6.58 US$/hm^2 and 0.35 US$/hm^2. Appraising pollution treatment cost intuitively reflects the overall expenditure in NPS pollution reduction from an economic perspective. This study provides a foundation for the implementation of Payment for Ecosystem Service(PES) and the prevention and control of NPS pollution.

The Effect of Different Artificial Soil on Urban Non-Point Source Pollution Reduction in the Artificial Rapid Infiltration System

The non-point source pollution posed great risks to the urban water environment which has aroused great concerns. Artificial rapid infiltration systems have been widely used in sewage treatment, which have great environmental and economic values. This study investigated the potential of utilizing artificial rapid infiltration systems on the reduction of urban non-point source pollution. The obtained results showed that the components and composition of artificial soils were vital to the operational performance. The mixture of natural soil, coarse sand and zeolite was ideal for the construction of artificial soils. The permeability coefficient of soils could be improved to 0.166 cm/min at the optimized ratio of 1:1:0.05 (natural soil, coarse sand and zeolite). Also, high removal efficiency for the typical pollutants in rain runoffs (i.e. COD, NH4+-N, TN and TP) could be simultaneous obtained which was above 74% in the artificial rapid infiltration systems. The results demonstrated the effectiveness on the reduction of urban non-point pollution by optimized artificial rapid infiltration system.

Study on Pollution Sources and Degree of Sediments in Northwestern Rivers Flowing into Taihu Lake

[ Objective] The study aimed to analyze the pollution sources and degree of sediments in seven northwestern rivers flowing into Taihu Lake. [ Method] Based on a survey for the sediments in seven rivers flowing into the northwestern Taihu Lake from 2005 to 2007, the molar ratio of major elements was used to determine the main pollution sources of each channel, and the heavy metal pollution of sediments in the seven rivers was assessed by enrichment coefficient. [ Result] Mashan River, Liangxi River and Xiwan River mainly suffered municipal pollution; Zhihu Port and Caoqiao River were chiefly subjected to industrial pollution; Dapu River and Wujin River were mainly affected by agricultural pollution. In addition, the rivers mainly suffering industrial pollution had the most serious heavy metal pollution, followed by the rivers mainly undergoing agricultural pollu- tion, while the rivers chiefly affected by municipal pollution had the minimum pollution. [ Conclusion] The research could provide scientific references for the control of river pollution by heavy metals along Taihu Lake basin.

Effect of non-uniform swelling on coal multiphysics during gas injection: The triangle approach

In current dual porosity/permeability models,there exists a fundamental assumption that the adsorption-induced swelling is distributed uniformly within the representative elementary volume (REV),irrespective of its internal structures and transient processes.However,both internal structures and transient processes can lead to the non-uniform swelling.In this study,we hypothesize that the non-uniform swelling is responsible for why coal permeability in experimental measurements is not only controlled by the effective stress but also is affected by the adsorption-induced swelling.We propose a concept of the swelling triangle composed of swelling paths to characterize the evolution of the non-uniform swelling and serve as a core link in coupled multiphysics.A swelling path is determined by a dimensionless volumetric ratio and a dimensionless swelling ratio.Different swelling paths have the same start and end point,and each swelling path represents a unique swelling case.The swelling path as the diagonal of the triangle represents the case of the uniform swelling while that as the two perpendicular boundaries represents the case of the localized swelling.The paths of all intermediate cases populate inside the triangle.The corresponding relations between the swelling path and the response of coal multiphysics are established by a non-uniform swelling coefficient.We define this method as the triangle approach and corresponding models as swelling path-based ones.The proposed concept and models are verified against a long-term experimental measurement of permeability and strains under constant effective stress.Our results demonstrate that during gas injection,coal multiphysics responses have a close dependence on the swelling path,and that in both future experiments and field predictions,this dependence must be considered.

Research on the Non-Point Pollution Loads in the Lake Uluabat Basin

Lake Uluabat, having an international significance and subject to the Ramsar Convention, is fed by the basin of Mustafakemalpasa Stream which runs through fertile lands utilized for livestock breeding and agriculture. In this study, total amount of nitrogen (TN) and phosphorus (TP) loads of non-point pollutants (agriculture, livestock breeding, vegetation, surface runoff and small settlements) was calculated. It was found out that most intensive pollution load stemmed from livestock breeding which causes dispersion of 13653.57 tons·year-1 of TN and 3224.45 tons·year-1 of TP into the Lake Uluabat. Additionally, seasonal changes in concentration of TN and TP were observed during the period of 2008-2009 in Lake Uluabat. It was concluded that the rise of agricultural activities in summer months was the reason underlying the increase in pollution during the months in question.

Investigation of Dynamic Behavior in 1D Non-uniform Granular System

We present a non-uniform granular system in one-dimensional case, whose granularity distribution has the fractal characteristic. The particles are subject to inelastic mutual collisions and obey Langevin equation between collisions. By Monte Carlo simulation we study the dynamic actions of the system. Far from the equilibrium, i.e., τ 〉〉 τe, the results of simulation indicate that the inhomogeneity of the system and the inelasticity of the particles have great influences on the dynamic properties of the system, and correspondingly the influence of the inhomogeneity is more significant.

Numerical simulation on rotordynamic characteristics of annular seal under uniform and non-uniform flows

Currently, the flow field of annular seals disturbed by the circular whirl motion of rotors is usually solved using computational fluid dynamics(CFD) to evaluate the five rotordynamic coefficients. The simulations are based on the traditional quasi-steady method. In this work, an improved quasi-steady method along with the transient method was presented to compute the rotordynamic coefficients of a long seal. By comparisons with experimental data, the shortcomings of quasi-steady methods have been identified. Then, the effects of non-uniform incoming flow on seal dynamic coefficients were studied by transient simulations. Results indicate that the long seal has large cross stiffness k and direct mass M which are not good for rotor stability, while the transient method is more suitable for the long seal for its excellent performance in predicting M. When the incoming flow is non-uniform, the stiffness coefficients vary with the eccentric directions. Based on the rotordynamic coefficients under uniform incoming flow, the linearized fluid force formulas, which can consider the effects of non-uniform incoming flow, have been presented and can well explain the varying-stiffness phenomenon.

Sources of Particular Pollutants inAmbient Air at a Petrochemical Enterprise

The study on source apportionment of particular pollutants in ambient air at a petrochemical enterprise is the ba-sis of the control over air pollution. Through analyzing particular pollutants in the samples collected from one petrochemi- cal enterprise in northwestern China, the sources of particular pollutants were discussed. The test results showed that con- centrations of particular pollutants in different sites were remarkably different. Results showed that the sampling sites with higher concentrations of particular pollutants, including toluene, xylenes, NH3 and H2S, were located at the boundary of the petrochemical enterprise. Instead, the concentrations of NMHC in the ambient air sampling sites were higher than those at the boundary of the petrochemical enterprise. The sampling sites with higher concentrations of particular pollutants were located in the area that was close to the petrochemical enterprise. The results obtained from the Pearson correlation co- efficients analyses, the factor analyses, and x^2-tests of the particular pollutants had revealed that NH3, H2S, toluene and xylenes at all sampling sites came from the same source, while NMHC might come from some other sources besides the petrochemical enterprise.

The Introduction of Specific Water and Maximum Airborne Specific Water &the Improvement of Dynamic Equations on Non-Uniform Saturated Moist Atmosphere

To eliminate the irrational supposition that condensed liquid water always falls immediately, specific water m?and maximum airborne specific water mm are introduced into the dynamic framework on non-uniform saturated moist atmosphere (m?is the ratio of the airborne liquid water mass to the moist air mass in unit cubage moist air, mm is its maximum value with , , and are airborne coefficient, vertical velocity and saturated specific humidity respectively). The balance equation between water vapor and airborne liquid water is derived. From the balance equation, a new formula of precipitate rate is got. The analysis shows that in the air stream with some upward vertical velocity ( ), the condensed liquid water can precipitate under the condition with (q is specific humidity) and? only, otherwise it is detained in the air and becomes airborne liquid water. Not only does precipitating liquid water contain condensed liquid water, but also contains converged and existing airborne liquid water. Following above discussion, improved dynamic equations on non-uniform saturated moist atmosphere are provided.

Characteristics of Mesh Wave Impedance in FDTD Non-Uniform Mesh

In order to increase the evaluating precision of mesh reflection wave, the mesh wave impedance (MWI) is extended to the non-uniform mesh in 1-D and 2-D cases for the first time on the basis of the Yee's positional relation for electromagnetic field components. Lots of characteristics are obtained for different mesh sizes and frequencies. Then the reflection coefficient caused by the non-uniform mesh can be calculated according to the theory of equivalent transmission line. By comparing it with that calculated by MWI in the uniform mesh, it is found that the evaluating error can be largely reduced and is in good agreement with that directly computed by FDTD method. And this extension of MWI can be used in the error analysis of complex mesh.

Loss coefficient of nitrogenous non-point source pollution under various precipitation conditions

In this study,calibrations of non-point source(NPS)pollution models are performed based on Black River basin historical real-time runoff data,sedimentation record data,and NPS sources survey information.The concept of NPS loss coefficient for the watershed or the loss coefficients(LC)for simplicity is brought up by examining NPS build-up and migration processes along riverbanks in natural river systems.The historical data is used for determining the nitrogenous NPS loss coefficient for five land use types including farmland,urban land,grassland,shrub land,and forest under different precipitation conditions.The comparison of outputs from Soil and Water Assessment Tool(SWAT)model and coefficient export method showed that both methods could obtain reasonable LC.The high Pearson correlation coefficient(0.94722)between those two sets of calculation results justified the consistency of those two models.Another result in the study is that different combinations of precipitation condition and land use types could significantly affect the calculated loss coefficient.As for the adsorptive nitrogen,the order of impact on LC for different land use types can be sorted as:farm land.urban land.grassland.shrub land.forest while the order was farmland.grass land.shrub land.forest.urban land for soluble nitrogen.

Generation and Discharge of Pollutants in Closed Aquaculture

[Objectives]To gain an in-depth understanding of pollutant generation and discharge from closed aquaculture.[Methods]In 2018,the pollutant generation and discharge coefficients of 7 farming modes in 16 farming bases were calculated and analyzed.[Results]A total of 28 pollutant generation coefficients and 28 pollutant discharge coefficients were obtained,and the generation and discharge of pollutants in closed aquaculture were grasped preliminarily.Compared with the data of the first census of pollutions sources published by the state in 2008,7 kinds of pollution generation coefficients increased,while 14 kinds decreased;and 4 kinds of pollutant discharge coefficients increased,while 17 kinds decreased.[Conclusions]In recent years,the pollutant generation and discharge coefficients of aquaculture show a decreasing trend.

Study on the Migration Mechanism of Typical Characteristic Pollutants in Coking Enterprises

Groundwater pollution in north China is serious, which is mostly caused by complex factors. Aiming at the problems such as the unknown reasons for the differences in the migration characteristics of typical characteristic pollutants in the same medium and the unknown migration rules of complex pollutants in soil and groundwater, this paper selected a single sample and a mixed sample of typical characteristic pollutants in coking enterprises to carry out the static adsorption test. The results showed that the distribution coefficients of benzene series and aromatic hydrocarbon pollutants in soil-water were K_(d)benzene >K_(d)toluene >K_(d)ethylbenzene >K_(d)pyrene >K_(d)anthracene >K_(d)naphthene, and the distribution coefficients of ammonia nitrogen, phenols and cyanogen were K_(d)ammonia nitrogen >K_(d)phenols >K_(d)cyanogen. The overall distribution coefficient of benzene series was higher than that of PAHs, and it was easier to be adsorbed by silty loam. Different carbon and hydrogen mass and even electron distribution of typical characteristic pollutants led to differences in the migration characteristics of benzene and aromatic pollutants. The more carbon and hydrogen there were, the more even the electron distribution was, and the more difficult it was to migrate in the soil. Among the same kind of pollutants, the migration of complex pollutants was weaker than that of single pollutants. The research could provide the parameter basis for establishing the solute transport model of groundwater and the design basis for developing the related risk control and pollution prevention strategies.

土壤磷素地表径流提取系数研究进展

土壤磷素地表径流提取系数(phosphorus extraction coefficient,ECp)是模拟表层土壤可溶性磷随地表径流迁移,估算农业磷非点源污染负荷模型中的一个重要参数。当前ECp的相关研究存在内涵模糊,确定方法各异,变异范围和影响机制也不够清晰等问题。本文梳理了国内外相关研究中ECp的提取方法、影响因素,为提高农业磷非点源污染评估的精度提供理论依据。ECp定义为地表径流溶解态磷(dissolved phosphorus,DP)浓度与表层土壤可溶性磷含量的比率。该系数通常基于降雨试验,通过建立地表径流DP和表层土壤磷含量的线性回归方程,用回归线的斜率表示ECp,因此其概念本质主要体现在统计学意义上。ECp受降雨、土壤、植被覆盖和农田管理措施等多种因素影响,变异范围较大。ECp通常与土壤黏粒含量、吸附性、植被覆盖度等因素呈反比,而与土壤初始含水量呈正比。非石灰性土壤ECp值一般大于石灰性土壤。为简化计算,ECp在NPS污染模型中通常被设为一个定值。例如,在化学物质、径流和土壤侵蚀(chemicals,runoff,and erosion from agriculture management,CREAMS)及农业非点源(agricultural nonpoint source,AGNPS)模型中,ECp值设为7.5,而在土壤侵蚀和作物生产力评价(erosion/productivity impact calculator,EPIC)和水土评估工具(soil and water assessment tools,SWAT)模型中,ECp值则设为5.7。因此,未来研究仍需重视ECp的物理内涵,精准测算多次降雨平均和动态ECp,阐明土壤磷素地表径流提取的动力机制;加强地表径流和表层土壤中可溶性磷素含量间的非线性关系的研究,提高ECp值确定方法的适用性;深入分析不同区域ECp的变异特征和影响因素,针对施肥频繁且易发生复杂强烈水力侵蚀的坡耕地,尤其需要提出ECp的校正值;用核定后或者监测获得的ECp统计值代替现有NPS污染模型中的常数,以提高土壤磷素流失负荷模拟精度。

渭河流域陕西段农业面源污染空间分布及特征分析

为探究渭河流域陕西段农业面源污染成因,明晰污染物空间分布,以精确评估区域内农业面源污染状况,采用产污系数法与等标污染负荷法核算渭河流域陕西段2021年各县(区、市)农业面源污染物化学需氧量(COD)、总氮(TN)、总磷(TP)的排放量、等标污染排放量和排放强度。运用自然断裂法和ArcGIS软件对农村生活、农田化肥、畜禽养殖、水产养殖4类污染源产生的污染物排放强度进行生态敏感性分析。结果表明:2021年渭河流域陕西段农业面源污染物总排放量为325.6万t,其中COD、TN、TP排放量分别为142.2万、129.1万、54.3万t;COD、TN、TP排放强度分别为2936、2665、1121 kg/km^(2)。渭河流域陕西段内各县(区、市)农业面源污染排放以农田化肥源和畜禽养殖源为主体,农业面源污染排放量的空间分布特征为从高到低、以中部县(区、市)为中心的环状分布。研究结果可为区域内农业面源污染防治提供数据支持与参考,为当地生态保护和农业产业结构调整助力。

农田土壤—小麦系统重金属迁移特征和风险评估

冬小麦是中国主要的粮食作物之一,本研究旨在探讨豫北典型农田土壤和小麦籽粒中重金属的富集特征及其潜在风险,为小麦种植及籽粒安全质量提供科学依据。采集了豫北典型农田的土壤和小麦籽粒样本,测定了其中的铁、锰、锌、铜、铬、镍等元素的含量,并对重金属的污染及其生态风险进行评价。结果表明,土壤中重金属元素铁、锰、锌、铜、铬、镍平均含量分别为11397.33、287.83、23.33、7.41、31.41、8.56 mg/kg;元素之间多数呈显著正相关关系;铜、锌、铬、镍单项污染评价和综合污染评价均为清洁无污染。小麦籽粒中重金属元素铁、锰、锌、铜、铬、镍平均含量分别为30.42、61.75、23.17、1.52、0.28、0.16 mg/kg;少数元素之间呈显著正相关关系。铁、锌、铜含量低于小麦可耐受最高含量,锰含量高于小麦可耐受最高含量;铬元素综合污染评价为轻度污染,镍元素污染评价为清洁无污染。土壤—小麦系统中重金属之间存在协同或拮抗作用,小麦籽粒对土壤重金属的富集系数表现为锌>锰>铜>镍>铬>铁。可得出结论豫北农田土壤重金属污染风险程度较低。

基于系统动力学模型的综合货运枢纽绿色转型机理及实施路径研究

为助力加快实现交通运输行业绿色转型,以综合货运枢纽为着眼点,探索其绿色转型和高质量发展的实施方案。首先,识别出政策、技术创新、管理效率等3个关键因素,揭示综合货运枢纽绿色转型的动态支撑机理。然后,基于对各因素的分析,将环保政策松紧系数、科技投入系数、污染物排放系数作为变量,构建包含枢纽物流供应子系统、枢纽物流需求子系统、节能减排子系统的系统动力学模型。再以四川省某综合货运枢纽为例进行模拟,验证模型的有效性和实用性。最后,从政策标准、技术组合和管理效率等3个方面提出绿色转型路径。研究结果显示:(1)表征政策因素的环保政策松紧系数对节能减排有显著正面影响,但同时限制了枢纽总产值的提升,需关注政策出台时机和松紧度;(2)表征科技研发投入的科技投入系数对节能减排有显著正面影响,既减少碳排放,又不影响枢纽总产值提升,且存在后发优势;(3)表征绿色技术设备投入效果的污染物排放系数对节能减排有显著正面影响,但提示资金投入与减排效果并不是简单的线性关系,需重点关注绿色技术设备的组合优化,做好技术与业务流程的融合;(4)表征管理效率的排放治理投资系数呈现先增后减的趋势,说明需在枢纽结构、招商、人力、资金等方面设定合理区间以确保环保投入产出效果。通过动态模拟综合货运枢纽绿色转型机理,为地方政府因地制宜出台相关政策,以及为货运枢纽运营企业采取科学有效的技术手段和管理措施提供了理论依据。

引入空间修正入河系数的改进输出系数模型研究——以长江流域为例

针对长江流域开展面源污染负荷研究具有重要实践意义。传统输出系数模型为集总式模型,无法体现污染物的空间差异性,且未考虑污染源和受纳水体之间的污染物迁移损失,计算结果常为产污量而非入河量。为了降低区域自然地理条件差异造成的模拟结果的误差,综合考虑污染物在输移过程中受降雨、地形、植被和距离等因子的影响,对传统的Johnes输出系数模型引入空间修正的入河系数,构建具有空间分布性的改进输出系数模型。将改进后的输出系数模型应用于长江流域,对长江流域干流自上至下9个监测断面的总磷、化学需氧量进行模拟。分别将集总式输出系数模型和引入空间修正入河系数的改进输出系数模型的模拟结果与实测值进行比较,结果显示改进后的输出系数模型模拟精度较改进前显著提高,为流域面源污染综合治理提供参考依据和理论支撑。