增温对冻土区泥炭沼泽土壤孔隙水甲烷关联微生物和溶解性有机碳的影响

多年冻土区泥炭沼泽土壤孔隙水甲烷关联微生物及底物的研究有助于深入理解气候变化背景下寒区湿地生态系统甲烷循环过程。选取大兴安岭连续多年冻土区柴桦-泥炭藓和狭叶杜香-泥炭藓两种典型植被群落泥炭沼泽,设置开顶箱(Open Top Chamber,OTC)增温实验。于生长季(6月、7月、8月和9月)采集土壤孔隙水样品,对比分析OTC内外土壤孔隙水中产甲烷菌数量、甲烷氧化菌数量及溶解性有机碳(Dissolved Organic Carbon,DOC)浓度的动态变化特征,并探究土壤孔隙水甲烷关联微生物与DOC浓度的关系。结果表明:增温提高了生长季大兴安岭多年冻土区土壤孔隙水中产甲烷菌数量和DOC浓度,而对甲烷氧化菌数量的影响因月份而异。生长季柴桦-泥炭藓和狭叶杜香-泥炭藓泥炭沼泽土壤孔隙水中产甲烷菌数量的平均增加幅度分别为54.52%和44.97%,DOC浓度的平均增加幅度分别为34.16%和28.33%。增温使得生长季柴桦-泥炭藓和狭叶杜香-泥炭藓泥炭沼泽土壤孔隙水中甲烷氧化菌平均数量分别降低了46.20%和31.42%。一元线性回归分析结果表明,土壤孔隙水中DOC浓度可分别解释柴桦-泥炭藓和狭叶杜香-泥炭藓泥炭沼泽土壤孔隙水中产甲烷菌数量变化的29.00%和24.10%(P<0.01),而对两种植被群落下土壤孔隙水中甲烷氧化菌数量的影响并不显著(P>0.05)。

长期施肥潮土土壤呼吸的温度和水分效应

温度和水分是影响土壤呼吸的重要因素。利用室内培养试验研究因长期施用不同肥料造成有机质含量存在差异的土壤在不同土壤水分含量(30%WFPS、45%WFPS、60%WFPS、75%WFPS和90%WFPS)和培养温度(5℃、15℃、25℃、35℃)下的土壤呼吸。结果表明,土壤水分含量和培养温度对土壤呼吸既表现出相互制约作用,在一定范围内又具有相互促进作用。施肥影响着土壤呼吸所需的最适水分含量,不均衡施肥处理的土壤呼吸所需最适土壤水分含量高于均衡施肥处理的土壤。培养温度也影响土壤呼吸的最适水分含量,土壤呼吸所需最适水分随培养温度升高而升高。土壤水分含量的增加可增加土壤呼吸的Q10。施肥特别是施有机肥而增加的土壤有机碳的释放速率是最快的。因此,气温升高和降水增加等气候变化趋势下,不利于通过施用有机肥来增加农田土壤有机碳储量。

不同水分条件下不同土壤微生物类群产N_2O量的初步研究

本研究主要是通过微生物分离手段加富培养菜园土中的硝化菌、厌氧反硝化菌和异养硝化/好氧反硝化菌,并在30%、50%和100%3种土壤充水孔隙度(指土壤体积含水量与总孔隙度的百分比,V/V)水分条件下进行无菌菜园土反接种培养实验,研究了不同水分条件下、不同土壤微生物类群的产N2O量。结果表明:30%含水量的灭菌土壤反接种培养,N2O的产生是以异养硝化/好氧反硝化作用为主,自养硝化作用对于N2O亦有贡献,后者产N2O量仅是前者的15.2%～47.2%;而50%含水量的灭菌土壤反接种培养,N2O的产生过程是以自养硝化为主,其N2O产生量几乎是异养硝化/好氧反硝化菌处理的2.1倍。在上述3种水分条件下,厌氧反硝化菌活性均受到抑制,几乎不产生N2O。

水分非均匀分布条件下土壤CO_2的排放特征

为了研究水分非均匀分布条件下旱地土壤CO2的排放特征,采用静态箱-气相色谱法测定了SI、SDI12、SDI15及SDI18共4个处理的CO2排放通量。结果表明：总体上CO2排放通量平均值表现为SI〉SDI12〉SDI15〉SDI18,但仅SI处理与SDI18之间的差异具有显著性;2次灌水后SDI处理土壤CO2排放较高的WFPS范围分别是25.9%~33.8%和31.5%~33.0%,低于SI处理出现高峰排放的WFPS分别为47%和34.1%;由于温度的影响第2次灌水后CO2排放通量总体上高于第1次灌水后,但第1次灌水后CO2排放通量与温度具有较强的相关性,而第2次灌水后两者之间相关关系不显著,可能存在过高温度下的土壤呼吸抑制。此外降雨发生时空气湿度的增加对微生物的呼吸有刺激作用,各处理降雨后出现了短期的CO2排放通量的小高峰。

土壤水分垂直非均匀分布下CO_2的日排放特征

以黏土为研究对象,利用地表灌水（SI）和不同深度的地下灌水（SDI12、SDI15和SDI18）实现了不同的水分垂直非均匀分布,研究了不同水分分布下的旱地土壤CO2日排放特征。结果表明：不同的处理的CO2排放呈现相同的日变化规律,但不同处理间排放量存在差异;两次灌水后CO2日平均排放通量之间的大小关系均表现为SI〉SDI12〉SDI15〉SDI18,且SI处理在初次灌水后的排放通量显著大于SDI15和SDI18处理,而第二次灌水后各处理之间均有明显的差异性。各处理在两次灌水后同一观测日内,其0-12 cm土层的土壤水分WFPS之间的大小关系分别为：SI〉SDI12〉SDI15〉SDI18和SI〈SDI12〈SDI15〈SDI18。对同一处理来说,其土壤0-12 cm土层的平均含水率在不同观测日均呈现出逐渐递减趋势,相应的初次灌水后CO2日平均排放通量呈现出逐渐递增的趋势,而第二次灌水后SI和SDI12处理呈现出逐渐递增的趋势,SDI15和SDI18则呈现出先递减后递增的趋势。此外,比较第一次和第二次灌水后的CO2排放,发现季节温度变化是影响CO2日排放重要因素,CO2的排放随着温度的升高而增加,而温度过高时,CO2的排放随温度升高出现降低的趋势。

小麦秸秆还田对玉米季土壤养分和N_(2)O排放及玉米产量的影响

秸秆还田是华北地区冬小麦-夏玉米耕作的一项非常重要的农田管理措施,研究秸秆还田对土壤N_(2)O排放的影响,对推广秸秆还田节能减排、响应化肥零增长行动、促进农业可持续发展具有重要意义。设置秸秆还田(CS)和秸秆不还田(CF)2个处理,利用静态箱-气相色谱法对玉米季土壤N_(2)O排放情况进行研究,并采集土样研究秸秆还田对土壤理化性质的影响。结果表明,在玉米季,秸秆还田处理N_(2)O累积排放量比秸秆不还田处理下降9.56%;土壤温度和水分与N_(2)O排放呈显著相关(P<0.05)或极显著相关(P<0.01);与秸秆不还田处理相比,秸秆还田处理的有机质和全氮含量较高,容重较低;秸秆还田处理的产量比秸秆不还田高0.48%。说明华北平原冬小麦-夏玉米轮作制度下,小麦秸秆粉碎覆盖免耕还田有利于玉米季土壤N_(2)O减排和降低土壤容重,有利于增加土壤有机质和全氮以及玉米产量,但是相关影响因子的相互作用还需进一步研究。

某农药厂周围土壤四氯化碳污染特征研究

通过对土壤和土壤孔隙水四氯化碳含量的测试,研究了某农药厂附近土壤四氯化碳污染特征。该农药厂排污渠和供水井附近的土壤中均检测出四氯化碳和氯仿,含量分别为0.7～42.2μg·kg-1和2.6～26.5μg·kg-1;土壤孔隙水四氯化碳主要在农药厂供水井附近检出,含量1.4～2.8μg·L-1。污染源区土壤中不存在四氯化碳污染池。四氯化碳在土壤中的分布主要受四氯化碳来源、四氯化碳的挥发作用和四氯化碳的自然衰减作用所控制。四氯化碳最高含量均出现在农药厂供水井附近,四氯化碳主要在3m以下的土层中检测出,且随深度增加而增加;表层土壤四氯化碳含量相对较低或未检出。

不同土壤中镍的离子活度研究

自由离子浓度(或活度)是决定重金属的生物有效性和化学行为的关键因素,然而土壤系统中自由金属离子的活度测定与模型预测还存在很多不确定因素。该研究以重金属元素镍为研究对象,从它的固液分配系数、自由离子活度影响因素出发,通过经验的多元回归模型以及腐殖质平衡模型(WHAM VI)分析了影响其指标变化的关键因子。结果发现,土壤孔隙水的pH是影响镍在土壤固/液相分配的最关键因子,可以解释91%固液分配系数(K_d)的变化;同时,它也是影响自由镍离子活度占总镍百分比的最关键因子(r^2=0.74),土壤孔隙水中溶解性有机碳含量(DOC)可以提高回归模型的预测,但贡献率仅占10%。使用WHAM VI预测土壤孔隙水中自由镍离子活度的结果显示,采用惯用的65%活性富里酸(AFA)代替孔隙水中的活性DOM会导致预测值低于道南膜技术(DMT)测定值20%左右(碱性土壤除外),两者均方根误差(RMSE)达到15.7。分别降低碱性、中性、酸性土壤中的%AFA至50%、10%、5%,模型预测能力显著提高,预测值与实测值百分比的RMSE达到8.65。其研究结果说明土壤中的活性DOM比例较低(5%～50%),尤其对于中性与酸性土壤来说,活性DOM≤10%。该研究结果对于土壤系统的模型构建与重金属镍的环境风险评估具有重要意义。

水肥减量对设施芹菜地N_2O排放的影响

为明确减量灌溉和施肥对设施菜地N_2O排放的影响,提出有效的N_2O减排措施,本研究采用静态箱法,对北京郊区设施芹菜在灌溉和有机肥(沼渣)减量处理下的N_2O排放进行全生长季监测,分析灌溉和有机肥减量对土壤充水孔隙度(WFPS)、NO_3^--N和NH_4^+-N含量及土壤N_2O排放的影响。试验为2个灌溉量和3个有机肥施用量的裂区双因素设计,具体为:常规灌溉量(H处理)下的常规施肥(HN)、减量1/3施肥(HN3)和不施肥(HN0),以及减量20%灌溉(L处理)下的常规施肥(LN)、减量1/3施肥(LN3)和不施肥(LN0)共6个处理。结果表明,L处理在保证芹菜产量的前提下,对土壤充水孔隙度及无机氮含量无显著影响,但N_2O排放总量较H处理减少32.23%,达极显著水平(P<0.01)。与常规施肥处理相比,减量1/3施肥和不施肥处理的土壤NO_3--N含量分别降低43.96%和76.42%,均达极显著水平(P<0.01),不同施肥量处理间土壤NH_4^+-N含量无显著差异;芹菜产量随施氮量增加而增加,但减量1/3施肥和常规施肥处理对芹菜产量影响无显著差异,芹菜全生长季的土壤累积N_2O排放总量显著减少62.04%(P<0.01)。本试验条件下,减量20%灌溉(L处理)和减量1/3施肥(N3处理)均能保证芹菜产量,显著降低芹菜地N_2O排放通量,减少生产成本投入。

有机肥部分替代化肥对温室番茄土壤N2O排放的影响

【目的】在等氮量有机部分替代化肥条件下研究温室番茄土壤N2O排放特征,探讨影响温室土壤N2O排放的环境因素,为估算温室菜地系统N2O的排放清单及其减排潜力提供数据支撑和理论依据。【方法】以温室秋冬茬番茄为研究对象,设置不施肥(CK)、单施有机肥(MN)、单施化肥(CN)、有机肥部分替代化肥(CMN)4个处理,采用静态箱-气相色谱法,对番茄生育期内土壤N2O排放及土壤温度、含水量进行监测。【结果】在相同施氮量情况下,处理CMN(有机部分替代无机)的N2O排放总量为4.05 kg·hm^-2,相比处理CN(单施化肥)和MN(单施有机肥),土壤N2O排放总量降低了45.1%和33.2%;土壤N2O排放系数分别降低了50.0%和37.5%;排放强度降低了50.0%、42.1%。各处理土壤N2O排放通量峰值均出现在施肥灌水后第1天,排放主要集中在施肥灌溉后5 d内。温室番茄土壤N2O排放通量与0-5 cm地温呈显著或极显著线性相关关系;与土壤充水孔隙率(WFPS)呈显著或极显著的对数函数关系,且不同施肥处理下土壤N2O排放峰值出现在土壤充水孔隙率60%—80%范围内。【结论】温室番茄土壤N2O排放的消长关系表现在温湿度变化和氮肥投入类型等方面,合理的减排措施应综合考虑以上因素。有机部分替代化肥施肥模式是提高温室番茄产量,减少N2O排放排放强度、排放系数和排放总量,提高肥料利用率,实现化肥零增长的重要手段。

Characteristics of Soil Porosity and Changes of Soil Water Content in Eucalyptus Plantation

Objective] This study almed to investigate the characteristics of soiI total porosity （STP） and various factors affecting soiI water content （SWC） in eucalyptus pIantation （EP）, thereby providing references for soiI water utiIization in eucalyptus pIanting in the red soiI hiI y region of South China. [Method] In the same cIimatic region, soiI sampIes were coI ected from surface soiI Iayer （A）, iI uvial horizon （B） and parent material horizon （C） in the upper sIope, middIe sIope and Iower sIope of eucalyptus pIantation, native forest and pine forest, respectiveIy, to determine the soiI porosity and soiI water content and analyze changes and various infIuencing factors of soiI water content in horizontal and vertical direction. [Result] Average soiI porosity in eucalyptus pIantation, native forest and pine forest was 45.9%, 41.4%and 55.3%, respectiveIy; soiI water content in these three forest stands was 13.3%, 13.4% and 15.5%, respectiveIy. In addition, soiI water content in these three forest stands exhibited no significant differences （P＆gt;0.05） among different soiI profiIes and sIope positions, but soiI water content in surface soiI Iayer varied significantIy （P＆lt;0.05） among different forest stands; in the horizontal direction, soiI water content exerted an extremeIy significant positive correIation with total coverage. [Conclusion] Total coverage of canopy Iayer, herb and Iitter Iayer is one of the most critical fac-tors affecting the changes of soiI water content in surface soiI Iayer of forest stands.

施铁对普通野生稻田甲烷排放的影响

为了探究施铁对普通野生稻田甲烷的减排效果,对1个根表铁膜形成能力较强的普通野生稻居群进行了水泥池小区对比试验,观测了施铁处理和对照的CH_(4)排放速率、土壤孔隙水Fe^(2+)浓度和根表铁膜。结果表明:施铁导致CH_(4)总排放量减少了29.51%,在普通野生稻生长前期CH_(4)减排效应尤为明显。移栽后第19天,施铁小区的土壤孔隙水Fe^(2+)浓度为0.57 mmol·L^(−1),显著大于对照小区。根生物量和单株根表铁膜数量在施铁处理和对照之间的差异随植株年龄增大而增大。因此,施铁措施对具有厚铁膜潜力的普通野生稻居群的CH_(4)减排能起到明显的促进作用。

Soil Strength Characteristics Along an Arable Eroded Slope

Undisturbed soil cores were taken from different slope positions （upslope, backslope and footslope） and soil depths （0-15, 20-35 and 100-115 cm） in a soil catena derived from Quaternary red clay to determine the spatial changes in soil strength along the eroded slope and to ewluate an indicator to determine soil strength during compaction. Precompression stress, as an indicator of soil strength, significantly increased from topsoil layer to subsoil layer （P 〈0.05） and was affected by slope position. In the subsoil layer （20-35 cm）, the precompression stress at the footslope position was significantly greater than at the backslope and upslope positions （P 〈0.05）, while there were no significant differences at 0-15 and 100-115 cm. Precompression stress followed the spatial wriation of soil clay content with soil depth and had a significant linear relationship with soil porosity （r^2 = 0.40, P 〈 0.01）. Also, soil cohesion increased with increasing soil clay content. The precompression stress was significantly related to the applied stress corresponding to the highest change of pore water pressure （r^2 = 0.69, P 〈 0.01）. These results suggested that soil strength induced by soil erosion and soil management wried spatially along the slope and the maximum change in pore water pressure during compaction could be an easy indicator to describe soil strength.

Ecogeomorphic Feedbacks in Semiarid Rangelands:A Review

The ecogeomorphic processes occurring on semiarid rangelands are reviewed, with emphasis on the source-sink relations and positive feedback loops that existed between shrub patches and intershrub areas, and the way livestock presence affected these interactions. Compared with intershrub areas, the shrub patches had a higher soil porosity, infiltration capacity, water-holding capacity, hydraulic conductivity, structural stability, and organic matter content, and lower bulk density. These differences derived from a host of processes whose intensity was less in the shrub patches, including raindrop impact, mechanical crust formation, overland water flow, soil erosion, evaporative moisture loss, and flock trampling. There was also greater shading of the soil surface; soil and litter deposition; water accumulation; microbial, fungal, and mesofaunal activities in the shrub patches. The overland flow of water carried soil and litter from the intershrub areas to the shrub patches and resulted in microtopographic modifications that tended to strengthen these source-sink relations. Grazing had an impact on these processes, not only at the shrub-intershrub scale but also within the intershrub areas, through the creation of highly compacted trampling routes. The combined role of the above ecogeomorphic processes was to maintain the rangeland＇s functionality. Without these inter-relationships, water loss, soil erosion, and nutrient depletion would occur at the hillside scale, causing degradation of the landscape.

A case study of seismic response of earth embankment foundation on liquefiable soils

A case study of seismic response of an earth embankment foundation on liquefiable soils in Kansai area,western Japan was presented. Based on a calibrated cyclic elasto-plastic constitutive model for liquefiable sand and Biot dynamic coupled theory,the seismic analysis was carried out by using a dynamic effective stress finite element method under plane strain condition. A recent design study was illustrated in detail for a river earth embankment subjected to seismic excitation on the saturated deposits with liquefiable sands. Simulated results of the embankment foundation during liquefaction were obtained for acceleration,displacement,and excess pore water pressures,which were considered to yield useful results for earthquake geotechnical design. The results show that the foundation soil reaches a fully liquefied state with high excess pore pressure ratios approaching to 1.0 due to the earthquake shaking. At the end of the earthquake,the extensive liquefaction causes about 1.0 m lateral spreading at the toe and 60 cm settlement at the crest of the earth embankment.

Effective stress in soils under different saturation conditions

BISHOP’s effective stress or two state stress variables are unsatisfactory for unsaturated soils where one of fluid phases is discontinuous, so new expressions of effective stress should be founded. The approach for derivation was according to the principle of equilibrium of forces (i.e., the stress-sharing principle), and it was firstly validated by demonstrating TERZAGHI’s principle of effective stress. And then, the derivations were subdivided into four parts according to different pore air states: 1) air bubbles were spherical and suspended in pore water; 2) air bubbles were bound on soil skeleton; 3) air bubbles held almost the single section of pore; 4) air phase was continuous. The different formulae of effective stress were presented. Conclusions are drawn as follows: 1) For nearly-saturated soils, the "real" effective stress would be a little smaller than TERZAGHI’s effective stress; 2) For soils in which air phase is discontinuous in the form of bubbles, a new concept of pore air elastic pressure is put forward, and the total stress can be constituted by effective stress, pore water pressure and pore air elastic pressure; 3) For soils in which air phase is continuous, effective stress is equal to the value of the total stress plus suction; 4) Suction can be divided into two parts: one is the effect caused by additional pressure, and the other is the contract action by the "skin".

Numerical Investigation on the Initiation Mechanism of Debris-Flow under Rainfall

Rainfall is an important factor to trigger the debris flow.Numerical simulation on the responses of slopes and the initiation of debris flow under rainfall was processed by using the software FLAC2D based on the soil parameters in Weijia Gully,Beichuan County,Sichuan Province,China.The effects of the slope angle,rainfall intensity,soil parameters on the developments of the stress and pore pressure and deformation of the slope were studied.It indicates that large displacements of the slope are mainly located near the slope toe.With the increase of the rainfall intensity the stability of the slope decreases and so the debris-flow is easy to occur.

Experimental study on pore water pressure dissipation of mucky soil

Pore water pressure has an important influence on mechanical properties of soil.The authors studied the characteristics of pore water pressure dissipating of mucky soil under consolidated-drained condition by using refitted triaxial instrument and analyzed the variation of pore pressure coefficient with consolidation pressure.The results show that the dissipating of pore water pressure behaves in different ways depends on different styles of loading.What is more,the pore water pressure coefficient of mucky soil is less than 1.As the compactness of soil increases and moisture content reduces,the value of B reduces.There is a staggered dissipating in the process of consolidation,in which it is a mutate point when U/P is 80%.It is helpful to establish the pore water pressure model and study the strength-deformation of soil in process of consolidation.

纳米零价铁与土壤组分的相互作用及其环境效应

纳米零价铁(nZVI)具有良好的还原活性和吸附性能,已应用于土壤和地下水污染修复,且前景广阔。但性能优越的nZVI会与土壤组分相互作用,不仅可能影响土壤理化性质及其生态功能,也会影响nZVI的存在形态和修复功能。本文阐述了nZVI与土壤空气、孔隙水、黏土矿物、有机质、微生物等土壤组分的相互作用,分析了其对相应土壤组分及土壤整体理化性质的影响,探讨了各土壤组分作用下nZVI的形态转化,并提出了几个需要进一步研究的科学问题。本文将有助于nZVI环境修复应用领域的科学研究与技术进步。

红树林土壤盐分测定的几种方法比较

采集海南和福建共13个红树林的土壤,测定土壤孔隙水盐度、未校准的土壤盐度、经含水率校准的土壤盐度和土壤水溶性盐含量。结果显示,盐度计测定的土壤盐度经土壤含水率校准后与土壤孔隙水盐度接近,且相关性最好。未校准的土壤盐度平均只有孔隙水盐度的38%。土壤水溶性盐含量与孔隙水盐度不相关。结果表明,用盐度计测定土壤盐度再经土壤含水率校准是简便有效测定红树林土壤盐分的方法,而土壤水溶性盐含量对红树林土壤盐环境的指示性差。