土壤与大气Cu处理下迎春的耐性和富集特征研究

作为北京市常见园林灌木树种之一,迎春(Jasminum nudiflorum)因其在早春独特的观赏性而深受市民喜爱。Cu污染是北京市较为严重的重金属污染类型之一。为探讨迎春对城市Cu污染的修复作用,该文通过模拟北京市土壤和大气Cu污染条件,采用盆栽试验,设置9种不同浓度的土壤和大气Cu处理,以验证迎春Cu富集能力及生理生长特性。结果表明:(1)土壤和大气沉降处理均能显著增加迎春根、茎、叶中的Cu含量,其中土壤贡献率为63.48%~96.99%。各处理中Cu含量均表现为根>茎>叶。(2)大气处理下光化学转化效率(F_v/F_m)和相对叶绿素含量(SPAD值)提高,初始荧光(F_0)降低,光合能力增强,而土壤处理及土壤和大气双重处理则对迎春的光合作用产生抑制影响。(3)与大气处理相比,土壤处理及土壤和大气双重处理导致活性氧(ROS)积累增多,膜脂过氧化作用加剧,丙二醛(MDA)含量大幅升高,抗氧化酶活性与脯氨酸(PRO)含量逐渐下降,造成生物膜系统损伤。(4)低浓度Cu处理对迎春生长有促进作用,而高浓度Cu处理(SHAL、SHAH)则抑制迎春生长,迎春根系耐性指数(TI)最小值为69.19%,属于高耐受型植物。综上认为,在模拟北京市Cu污染处理下,迎春可以在维持自身正常生理生长活动的同时,有效吸收土壤和大气中的Cu。该研究结果为北京市Cu污染防治、生态环境修复提供一定的理论依据。

城镇燃气管道施工技术要点及相关问题阐述

随着城市化进程的推进,城镇燃气管网施工成为关键性工程。此类工程涉及多重因素,包括土壤沉降、温差影响等,均对管道的稳定性和安全性构成挑战。本文旨在探讨城镇燃气管网的基本特征,分析施工技术的关键点,并对施工过程中可能遇到的问题提供解决建议。

土壤成份分析实验的改进

土壤成份分析实验的改进潜江王场镇施场小学孙廷金（４３３１００）《自然》第二册（怎样认识物体（三）一土壤》一课，按教材中介绍的方法进行实验，实验现象不太明显，效果不好，如果在选用土壤时，土壤里含有的腐殖质不够充分，焙烧不充分，效果更差，在实验中应注意和...

氮添加对南方红豆杉叶功能性状及其可塑性的影响

【目的】氮沉降是显著影响林木生长的重要因素之一,南方红豆杉(Taxus chinensis var. mairei)是我国南方地区主要造林树种之一。研究南方红豆杉对氮添加环境的适应为营造林更新提供一定理论依据。【方法】研究以一年生南方红豆杉幼苗作为试验材料,设计盆栽实验,以NH4NO3作为外加氮源,设置4个土壤氮添加梯度(CK 0 kg/hm2,低氮40 kg/hm2,中氮80 kg/hm2,高氮160 kg/hm2)模拟氮沉降后的土壤环境,一年后测定南方红豆杉叶功能性状。【结果】(1)低氮添加对南方红豆杉各叶结构性状指标均有不同程度的抑制作用,但中高氮添加下比叶面积的回升辅以较小的叶厚度增强了叶片光合作用,在恢复部分叶片生物量的同时也提高了整体抗逆性,但整体指标仍不及CK处理。(2)受氮添加影响,南方红豆杉叶片磷显著提高而钾钙无显著变化,说明磷制约了叶片磷钾比与磷钙比,而钾与钙共同限制叶片钾钙比。(3)氮添加后叶厚度与比叶面积呈极显著负相关,与各化学性状均呈负相关关系,表明氮添加环境下南方红豆杉更倾向于养分储存而非快速生长。(4)CK处理的南方红豆杉幼苗可塑性最强,各处理下叶片化学性状的响应较结构性状更为迅速,表明氮添加环境削弱了南方红豆杉对叶结构性状的改变能力,生长策略也更加保守。【结论】南方红豆杉通过有限地增加比叶面积与减小叶厚度等适应性变化应对氮添加环境,通过提高磷元素利用率及调节化学计量比维持稳定生长并提高自身抗逆性,因此在林业生产中应适度控制传统氮肥的施用量并提高钾钙肥的施用配比,这将有助于提高南方红豆杉应对未来气候变化的适应能力。

运用多种手段做好自然实验

怎样灵活运用实验材料,设计合理的实验过程,提高实验效果?在多年的自然教学中我们做了以下几点尝试: 一、结合本地特点,选择实验材料做好实验 本地处于平原、丘陵、高山三结合的位置,享有“磷都”之称,自然资源极其丰富,在上《岩石》时,我们把班上的同学分成若干个组,按照东、南、西、北四个方向分别拣石头,然后观察、研究,并与对本地石灰窑场、凝灰岩的石器雕刻厂、矿粉厂、磷肥厂。

研究水文地质问题对地质灾害隐患的影响

地质灾害已威胁到人民生命财产安全,制约了我国经济的发展。融化、土壤沉降、砂土液化等地质灾害的应急机制与水文地质条件密切相关。本文分析了这三种地质灾害与水文地质条件之间的关系,并从预防、应急和资源利用方面提出了对策。根据这些对策,可以为我国地质灾害的防治和自然生态环境的有效保护提供参考。

Engineering behavior and sedimentation behavior of lead contaminated soil-bentonite vertical cutoff wall backfills

Soil-bentonite （SB） vertical slurry cutoff wall is a useful treatment for urban industrial contaminated sites. Due to the clay-heavy metal interaction, significant changes would occur in the engineering behavior of SB cutoff walls. However, previous study is limited to kaolinitic soils or montmorillonitic soils along using solidum chloride and/or calcium chloride as target contaminant. In this work, a series of oedometer tests were conducted to investigate the effects of lead （Pb） on the compressibility and the permeability of kaolin-bentonite （KB） mixtures, a simplified model of in-situ SB cutoff wall backfills. In addition, sedimentation tests were conducted to interpret the mechanism controlling the change of compressibility and permeability from the perspective of soil fabric. The Pb-contaminated KB mixtures for oedometer tests and sedimentation tests were prepared with bentonite contents of 0, 5%, 10%, and 15% by dry mass, and they were mixed with pre-determined volume of lead nitrate solution based on designed Pb concentration and solid-to-solution ratio. The Pb concentration was controlled as 0, 0.1, 0.5, 1.0, 5.0, 10, and 50 mg/g with a solid-to-solution ratio of approximate 0.5. The prepared KB mixtures with bentonite contents of 0, 5%, and 10% were chosen for the sedimentation tests. They were freeze-dried and mixed with DDI with a solid-to-solution ratio of 10 g/100 mL. The results indicate that pH, compressibility, and permeability of KB mixture changed considerably with respect to Pb concentration. It is concluded that the fabric of KB mixture, depending on the particle-particle interaction subjected to different ranges of pH and Pb concentration, governs the sedimentation behavior and permeability. The results of liquid limit （WE） cannot be explained in terms of the sedimentation behavior since it is only ionic-dependent.

Atmospheric Deposition-Carried Pb, Zn, and Cd from a Zinc Smelter and Their Effect on Soil Microorganisms

Dust emissions from smelters, as a major contributor to heavy metal contamination in soils, could severely influence soil quality. Downwind surface soils within 1.5 km of a zinc smelter, which was active for 10 years but ceased in 2000, in Magu Town, Cuizhou Province, China were selected to examine Pb, Zn, and Cd concentrations and their fractionation along a distance gradient from a zinc smelter, and to study the possible effects of Pb, Zn, and Cd accumulation on soil microorganisms by comparing with a reference soil located at a downwind distance of 10 km from the zinc smelter. Soils within 1.5 km of the zinc smelter accumulated high levels of heavy metals Zn （508 mg kg^-1）, Pb （95.6 mg kg^-1）, and Cd （5.98 mg kg^-1） with low ratios of Zn/Cd （59.1-115） and Pb/Cd （12.4-23.4）. Composite pollution indices （CPIs） of surface soils （2.52-15.2） were 3 to 13 times higher than the reference soils. In metal accumulated soils, exchangeable plus carbonate-bound fractions accounted for more than 10% of the total Zn, Pb, and Cd. The saturation degree of metals （SDM） in soils within 1.5 km of the smelter （averaging 1.25） was six times higher than that of the reference soils （0.209）. A smaller soil microbial biomass was found more frequently in metal accumulated soils （85.1-438 μg C g^-1） than in reference soils （497 μg C g^-1）, and a negative correlation （P 〈 0.01） of soil microbial biomass carbon to organic carbon ratio （Cmic/Corg） with SDM was observed. Microbial consumption of carbon sources was more rapid in contaminated soils than in reference soils, and a shift in the substrate utilization pattern was apparent and was negatively correlated with SDM （R = -0.773, P 〈 0.01）. Consequently, dust deposited Pb, Zn, and Cd in soils from zinc smelting were readily mobilized, and were detrimental to soil quality mainly in respect of microbial biomass .

Undrained Behaviour of Silt under Static and Cyclic Loading

In this study, the undrained behaviour of silt under low stress level is studied. An effective preparation method for built-in silt samples in the triaxial test was firstly developed. By triaxial testing of samples at low confining pressures it was found that silt easily loses stability and liquefies. Loose silt may show temporary liquefaction under static loading, and develop full liquefaction under cyclic loading. The most important factors influencing the silt behaviour are porosity, confining pressure, consolidation state, cyclic loading level and number of cycles. The maximum obtainable shear stress is primarily a function of the confining pressure and the internal frictional angle. The actual structure of the silt material is the key factor in controlling its behaviour.

Effect of Simulated N Deposition on Soil Exchangeable Cations in Three Forest Types of Subtropical China

The effects of simulated nitrogen(N)deposition on soil exchangeable cations were studied in three forest types of subtropical China.Four N treatments with three replications were designed for the monsoon evergreen broadleaf forest (mature forest):control(0 kg N ha-1 year-1),low N(50 kg N ha-1 year-1),medium N(100 kg N ha-1 year-1)and high N(150 kg N ha-1 year-1),and only three treatments(i.e.,control,low N,medium N)were established for the pine and mixed forests.Nitrogen had been applied continuously for 26 months before the measurement.The mature forest responded more rapidly and intensively to N additions than the pine and mixed forests,and exhibited some significant negative symptoms,e.g.,soil acidification,Al mobilization and leaching of base cations from soil.The pine and mixed forests responded slowly to N additions and exhibited no significant response of soil cations.Response of soil exchangeable cations to N deposition varied in the forests of subtropical China,depending on soil N status and land-use history.

Effect of Wet Settlement on Mercury in Alpine Soil in Mercury Mining Area

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Load-settlement behaviour of a strip footing resting on iron ore tailings as a structural fill

This study presents a laboratory investigation of load-settlement behaviour of a strip footing resting on iron ore tailings used as a structural fill.The footing was placed at various depths in the tailings bed.The relative density of the tailings was varied as D_r = 50%,70%and 90%.An incremental load was applied on the footing while observing the settlement until the failure took place.The results obtained for tailings were compared with those for the sandy soil.It is observed that the load-bearing capacity and stiffness increase with an increase in footing embedment depth and relative density.Compared to load-settlement behaviour of Perth sandy soil,the tailings fill could have as high as 22 times and 13.5 times the load-bearing capacity and stiffness,respectively.Therefore,the replacement of sandy soil with iron ore tailings for structural fills is cost-effective,and moreover,this application contributes to environmental sustainability in construction.

Anthropogenic,detritic and atmospheric soil-derived sources of lead in an alpine poor fen in northeast China

Ombrotrophic bogs are faithful archive of atmospheric metal deposition, but the potential for fens to reconstruct environmental change is often underestimated. In this study, some new data on the Pb depositional history in northeast China were provided using two ^210Pb-dated peat sequences from a poor fen in the Fenghuang Mountain of Heilongjiang province. Anthropogenic, detritic and atmospheric soil sources were discriminated using a two-step sequential digestion （weak acid leaching to liberate mobile Pb which is often regarded as anthropogenic Pb, especially for recent samples） and a ratio of unsupported ^210Pb and supported ^210Pb with the logic of that the ^214Pb mainly represents the residual detritus （constant throughout the core） and the unsupported ^210Pb arises from atmospheric fallout. A higher ^210Pb/^214Pb suggests more contributions from atmospheric deposition to the Pb content in the peat, and a ratio of 10 was defined to indicate the boundary between detrific input and atmospheric deposition. The detritic Pb was estimated to be 10-13 mg·kg^-1, the anthropogenic Pb ranged from 10-80 mg·kg^-1, and the atmospheric soil-derived Pb ranged from 〈 5 mg·kg^-1 to 30 mg·kg^-1. The history of anthropogenic Pb pollution over the last 150 years was reconstructed, and the calculated Pb deposition rate （AR Pb） ranged from 5 to 56 mg·m^-2·yr^-1. Using Ti as a reliable reference, the enrichment factor of Pb （EF Pb） relative to the upper continental crust was calculated. Both AR Pb and EF Pb increased with time, especially after the foundation of the People＇s Republic of China. This is consistent with increasing industrialization and coal burning in the last 60 years in northeast China. The present record of anthropogenic Pb deposition was consistent with the previous reports and an increasing trend of environmental pollution due to anthropogenic activities, in contrasts to Europe and North America which have experienced a major environmental cleanup. For the first time, this work estimates atmospheric Pb deposition via a minerotrophic peat core in China. This will enhance the use of peat archives for studies of environmental change.

Soil Acidification in Response to Acid Deposition in Three Subtropical Forests of Subtropical China

Long-term changes in soil pH, the current status of soil acidification, and the response of bulk soil and soil water pH to experimental nitrogen addition under three subtropical forests were investigated in Dinghushan Biosphere Reserve of subtropical China. The results showed that the mineral soil pH at 0-20 cm depth declined significantly from 4.60-4.75 in 1980s to 3.84-4.02 in 2005. Nitrogen addition resulted in the decrease of pH in both bulk soil and soil water collected at 20-cm depth. The rapid decline of soil pH was attributed to long-term high atmospheric acid deposition (nitrogen and sulphur) therein. The forest at earlier succession stage with originally higher soil pH appeared to be more vulnerable to acid deposition than that at later succession stage with originally low soil pH.

A simplified approach for settlement calculation of pile groups considering pile-to-pile interaction in layered soils

A simplified approach is presented for the analysis of the settlement of vertically loaded pile groups. In order to simulate the nonlinear pile-to-pile interaction in pile groups, the soils along the piles are assumed to behave as a series of nonlinear springs subjected to the shaft shear stress at the pile/soil interface. Considering the displacement reduction induced by the pile-to-pile interaction, the shear-deformation method is adopted to approximate the displacement field of the layered soils around the piles, and the equivalent stiffness of the springs is obtained. Furthermore, the load-settlement response of pile groups is deduced by modifying the load-transfer functions to account for the pile-to-pile interaction. The settlements of a laboratory pile groups computed by the presented approach are in a good agreement with measured results. The analysis on Contrastive parameters shows that the settlements of pile group decrease with the increase of the pile space and pile length, and the part of piles exceeding the critical pile length has little contribution to the beating capacity of the pile groups.

Influence of drainage of aquifer on settling of ground surface in mining area with high ground water level

Based on the basic principles of hydrogeology and soil mechanics, studied thegenesis mechanism and control factors of settling of ground surface caused by the drainageof the aquifer in the construction of coal mines, and put forward a corresponding calculatingmodel demonstrated by practical example.The study provides mining areas,which are covered with a very thick Quaternary soil layer and abundant ground water, witha theoretical basis aimed at forecasting the settling of ground surface.

Mercury Pollution of Soil-Crop System in Acid Precip-itation Area

In acid precipitation area of Chongqing suburb the average of Hg in soil rose from 0.158 mg/kg in 1984to 0.20 mg/kg in 1989, and Hg content of crops grown on these soils increased too. Both soil and vegetableHg came mainly from power plant emission, which caused Hg and acid precipitation pollution in environmentand the Hg pollution of water, crops and milk in the area.

Polychlorinated biphenyis in Beijing soil of China

The concentrations of polychlorinated biphenyls （PCBs） have been determined in soils collected in Beijing of China. According to Principle Component Analysis （PCA） of PCBs, the possible sources were studied. Relationship between PCBs and soil organic materials revealed that higher chlorinated PCBs are more inclined to be adsorbed by particles rich of organic materials. But the low chlorinated homologues are dominant in Beijing soils, which is very different from the foreign studies. It was concluded that the application of relatively low chlorinated commercial PCBs in China was the main reason leading to this homologue composition character. Besides, the relatively short pollution history is also one of the main reasons. PCA of PCBs data in Beijing soil and atmospheric deposition samples revealed that some other emission sources such as atmospheric deposition, automobile exhaust; chemical and petrochemical industry and steel industry may be the important reasons of elevated PCBs concentrations in Beijing soil

基于灰度计算饱和粘土的孔隙率

The chief concern of engineers is stabilization on building a road on saturated clay.The analysis of soil microstructure is of great’importance for preventing the collapse.sinking and distortion of groundwork.Porosity is one of parameters to analyse soil microstructure.This paper deals with a method based on the gray scale of soil microstructure graph to compute porosity.The scientific quality and feasibility can be guaranteed by the algorithm of porosity based on tri-dimensional space.The graphs can be directly used.The algorithm is proved to be more scientific.

Potential Contribution of Combined Atmospheric Ca^(2+) and Mg^(2+) Wet Deposition Within the Continental U.S. to Soil Inorganic Carbon Sequestration

Soil inorganic carbon （SIC） stocks continuously change from the formation of pedogenic carbonates, a process requiring inputs of Ca2＋ and Mg2＋ ions. This study ranked the soil orders in terms of potential inorganic carbon sequestration resulting from wet Ca2＋ and Mg2＋ deposition from 1994 to 2003 within the continental United States. The analysis revealed that average annual atmospheric wet deposition of Ca2＋ and Mg2＋ was the highest in the Central Midwest-Great Plains region, likely due to soil particle input from loess-derived soils. The soil orders receiving the highest total average annual atmospheric wet Ca2＋ and Mg2＋ deposition, expressed as potential inorganic carbon formation （barring losses from erosion and leaching）, were： 1） Mollisols （1.1 × 10^8 kg C）, 2） Alfisols （8.4 × 10^7 kg C）, 3） Entisols （3.8 × 10^7 kg C）, and 4） Aridisols （2.8 × 10^7 kg C）. In terms of area-normalized result, the soil orders were ranked： 1） Histosols （73 kg C km-2）, 2） Alfisols and Vertisols （64 kg C km-2）, 3） Mollisols （62 kg C km-2）, and 4） Spodosols （52 kg C kin-2）. The results of this study provide an estimate of potential soil inorganic carbon sequestration as a result of atmospheric wet Ca2＋ and Mg2＋ deposition, and this information may be useful in assessing dynamic nature of soil inorganic carbon pools.