富铁炭对填埋覆土层甲烷氧化主导微生物活动的影响

为了进一步明晰甲烷氧化菌群与环境间的相关关系,通过比较其甲烷氧化量和胞外聚合物(EPS)2种重要的微生物生命活动来探讨不同基质浓度与不同炭组间交互产生的环境差异对微生物群落的影响.结果表明,不同基质浓度对微生物多样性和种群差异影响最大.在甲烷与氧气(15％,V/V)均充足的情况下甲烷氧化累积量主要由Ⅰ型甲烷氧化菌贡献;...     

Ammonium-dependent regulation of aerobic methane-consuming bacteria in landfill cover soil by leachate irrigation

The impacts of landfill leachate irrigation on methane oxidation activities and methane-consuming bacteria populations were studied by incubation of landfill cover soils with leachate and (NH₄)₂SO₄ solution at different ammonium concentrations. The community structures and abundances of methane-oxidizing bacteria (MOB) and ammonia-oxidizing bacteria (AOB) were examined by PCRDGGE and real-time PCR. Compared with the pure (NH₄)₂SO₄ solution, leachate addition was found to have a positive effect on methane oxidation activity. In terms of the irrigation amount, ammonium in leachate was responsible for the actual inhibition of leachate. The extent of inhibitory effect mainly depended on its ammonium concentration. The suppression of the predominant methaneconsuming bacteria, type I MOB, was responsible for the decreased methane oxidation activity by ammonium inhibition. Methaneconsuming bacteria responded diversely in abundance to ammonium. The abundance of type I MOB decreased by fivefold; type II MOB showed stimulation response of fivefold magnification upon the first addition but lessened to be lower than the original level after the second addition; the amount of AOB was stimulated to increase for 20-30 times gradually. Accumulated nitrate from nitrification strengthened the ammonium inhibition on type I and type II MOB, as a result, repetitive irrigation was unfavorable for methane oxidation.     

Methanotrophic community structure of aged refuse and its capability for methane bio-oxidation

Aged refuse from waste landfills closed for eight years was examined and found to contain rich methanotrophs capable of biooxidation for methane. Specially, community structure and methane oxidation capability of methanotrophs in the aged refuse were studied. The amount of methanotrophs ranged 61.97 103–632.91 103 cells/g (in dry basis) in aged refuse from Shanghai Laogang Landfill. Type I and II methanotrophs were found in the aged refuse in the presence of sterilized sewage sludge and only Type I methanotrophs were detected in the presence of nitrate minimal salt medium (NMS). The clone sequences of the pmoA gene obtained from the aged refuse were similar to the pmoA gene of Methylobacter, Methylocaldum, and Methylocystis, and two clones were distinct with known genera of Type I methanotrophs according to phylogenetic analysis. Aged refuse enriched with NMS was used for methane biological oxidation and over 93% conversions were obtained.     

甲烷氧化菌在填埋场覆盖层中的工程应用(Ⅱ):基质选择性及长效性

针对已筛选获得的甲烷氧化混合菌,选取填埋场覆盖土(LCS)、矿化垃圾(AR)和塘渣(TZ)3种填埋场周边易得的材料为供试生存基质,从基质选择性及长效性角度进行了甲烷减排应用条件的探究及使用效能评估.结果表明,在TZ、LCS、AR、TZ-AR和LCS-AR这5种生存基质中,TZ-AR最适合甲烷氧化混合菌的生长,且TZ与AR的复配比例以5∶5为最佳.甲烷氧化混合菌在TZ-AR的粒径≤4 mm和含水率为20%时具有最高甲烷氧化能力.一次性接种甲烷氧化混合菌在静态体系中的最佳使用有效期为31 d.其在接种量为0.08、0.16、0.20 m L·g-1和0.25m L·g-1时甲烷氧化速率无明显差异,从工程应用角度而言,8%的接种量为最佳.     

水稻田土壤甲烷厌氧氧化在整个甲烷氧化中的贡献率

对黄松土水田土壤中>0.02mm的颗粒和<0.02mm的颗粒按不同比例组合成的土壤、不同绝对含水量的黄松土水田土壤、不同温育时段的水田土壤和长期定位不同施肥的水稻田土壤中的甲烷好氧氧化和厌氧氧化的速率的检测结果进行比较,结果相当一致,不仅证实了水稻田土壤甲烷厌氧氧化过程的存在,而且表明水田土壤中的甲烷厌氧氧化活性远较甲烷好氧氧化活性要低,如以两者的氧化活性作为对甲烷氧化的贡献来计,则甲烷厌氧氧化的贡献率一般都在整个甲烷氧化的10%以下.但在水田土壤被水淹没的情形下,由于土壤厌氧条件的形成和甲烷扩散受阻,甲烷厌氧氧化的速率明显超过好氧氧化的速率,甲烷厌氧氧化在整个甲烷氧化中的贡献率可到达30%以上.长期施肥对于水稻田土壤的甲烷好氧氧化活性和甲烷排放通量影响显著,而对甲烷的厌氧氧化活性有影响但未达到显著水平.长期施肥处理的土壤中甲烷好氧氧化活性在(9.072～41.088)×10^-6mol·(d·g)^-1之间,而甲烷厌氧氧化活性仅在(0.325～0.671)×10^-6mol·(d·g)^-1之间,仅及甲烷好氧氧化活性的1.31%～4.43%,占整个甲烷氧化的1.3%～4.14%.     

长期不同施肥对暗棕壤甲烷氧化菌群落特征与功能的影响

不同施肥方式对我国旱地农田土壤甲烷氧化影响的微生物机制尚不明确.本研究利用PCR-DGGE和实时荧光定量PCR技术,结合甲烷氧化速率和土壤性质测定,探索了长期不同施肥条件下暗棕壤的"土壤性质-甲烷氧化菌群落特征-土壤甲烷氧化速率"关系.结果表明,有机肥和无机肥配施处理显著降低了土壤甲烷氧化速率,降幅为61.2%,而单独施用有机肥或无机肥对暗棕壤甲烷氧化速率的影响不显著;与对照相比,有机肥处理土壤甲烷氧化菌多样性指数增加91.9%,有机肥和无机肥配施处理增加102.5%,而单施无机肥后土壤甲烷氧化菌多样性指数变化不明显;有机肥处理土壤的pmoA基因丰度显著增加,平均pmoA基因丰度为不施用有机肥的12.7倍;土壤甲烷氧化速率与甲烷氧化菌的群落结构和比活性呈显著正相关,相关系数分别为0.363和0.684,但与甲烷氧化菌群落丰度和多样性不相关;甲烷氧化菌的群落结构和比活性与土壤pH值、全氮和有机质含量呈显著正相关.上述结果说明,长期不同施肥可以通过改变暗棕壤的pH值、全氮和有机质含量等土壤性质,改变甲烷氧化菌群落结构和比活性,进而影响土壤甲烷氧化速率;有机肥和无机肥配施土壤甲烷氧化菌多样性和丰度大幅度增加,而甲烷氧化速率却显著降低,说明有机肥和无机肥配施土壤中只有部分微生物发挥了甲烷氧化活性,但有待进一步研究.     

硝酸盐和甲烷对覆土中苯系物厌氧氧化的影响

苯系物是填埋场填埋气中恶臭有机气体的重要成分之一,填埋气中的CH4则是重要的温室气体.填埋覆土层中的微生物可以氧化CH4和苯系物,因此,强化微生物的氧化效能有助于削减和控制填埋气的污染.电子受体还原可耦合甲烷和某些有机物的厌氧氧化,从而去除甲烷和有机物.鉴此,本研究通过静态培养试验,分析了电子受体SO2-4共存条件下,NO-3和CH4共存对覆土中苯系物厌氧降解的影响.结果表明不外加NO-3时,苯系物抑制CH4的降解,加入NO-3后,苯系物共存反而有利于CH4的去除;单独添加NO-3或CH4都能促进填埋覆土中苯系物的去除;而同时添加NO-3和CH4能更好地促进苯系物的去除,甲苯、二甲苯和异丙苯的去除率最高可达65%、88%和82%,远高于不添加NO-3和CH4对照处理的53%、76%和31%;NO-3还原与CH4厌氧氧化耦合过程能同步促进苯系物的厌氧氧化.     

Diversity of methanotrophs in a simulated modified biocover reactor

A simulated landfill biocover microcosm consisting of a modifying ceramsite material and compost were investigated. Results show that the mixture can improve the material porosity and achieve a stable and highly efficient (100%) methane oxidation over an extended operating period. The diversity of the methanotrophic community in the microcosm was assessed. Type I methanotrophs were enhanced in the microcosm due to the increased air diffusion and distribution, whereas the microbial diversity and population density of type II methanotrophs were not significantly affected. Moreover, the type I methanotrophic community structure significantly varied with the reactor height, whereas that of type II methanotrophic communities did not exhibit a spatial variation. Phylogenetic analysis showed that type I methanotroph-based nested polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) resulted in the detection of eight different populations, most of which are related to Methylobacter sp., whereas that of type II resulted in the detection of nine different populations, most of which are related to Methylocystaceae. Methanotrophic community analysis also indicated that a number of new methanotrophic genera not closely related to any known methanotrophic populations were present.     

甲烷胁迫下不同填埋场覆盖土的氧化活性及其菌群结构

对比研究了常规填埋场覆盖材料(粘土)和甲烷胁迫下垃圾生物处理后的材料(垃圾土)的甲烷氧化活性及其菌群结构.结果表明,粘土由于持水能力弱,其含水量较低,随着环境温度、降水等条件的变化,极易结块,从而影响其中甲烷氧化菌的生长;而垃圾土富含有机物,持水力强,空隙率高,有利于甲烷氧化菌的生长和繁殖.暴露于甲烷气流120 d后,垃圾土柱中下层土壤的甲烷氧化潜力达到了11.25～13.48 μmol/(g·h),是相应粘土层甲烷氧化潜力的10.4～24.5倍.土柱上层土壤由于水分蒸发、变干,抑制了其甲烷氧化活性.试验结束时,垃圾土柱甲烷氧化去除率达到了48.3%,是粘土柱的5～6倍.甲烷氧化菌TypeⅠ和TypeⅡ的生物标记物 PLFAs 16：1ω8c和18：1ω8c分析表明,土样的PLFA18：1ω8c含量与其甲烷氧化潜力具有很好的线性相关性.     

垃圾填埋场覆盖黄土的甲烷氧化能力及其影响因素研究

利用西安江村沟填埋场不同覆盖时间的临时覆盖黄土和新鲜黄土掺堆肥配置的土样,开展了甲烷氧化培养瓶试验,培养历时最长达22d,研究了不同覆盖时间的覆盖黄土和不同堆肥掺量的新鲜黄土的甲烷氧化能力,以及含水量对覆盖黄土甲烷氧化能力的影响,分析了甲烷氧化过程中各组分气体体积变化关系.研究结果表明:不同覆盖时间的覆盖黄土的甲烷氧化能力相差很大,覆盖3~5年的黄土最大甲烷氧化能力达26.05~53.95μg CH4/(g×h), 而未覆盖的新鲜黄土几乎没有甲烷氧化能力.在新鲜黄土中掺入堆肥,能有效提高其甲烷氧化能力,且在堆肥掺量小于50%时,土样的最大甲烷氧化能力与堆肥掺量呈正比例关系.含水量对覆盖土的甲烷氧化能力有很大影响,黄土甲烷氧化的最适宜含水量约为20% ~ 30%.在甲烷氧化过程中,甲烷氧化菌将CH4中约44%的碳氧化为CO2,其余碳转化为甲烷氧化菌胞内物质.实际工程中进行覆盖层设计时,需要根据填埋场实际产气量和覆盖层导气性确定与甲烷通量相匹配的甲烷氧化速率,进而合理确定堆肥掺量.     

湿地甲烷代谢微生物产甲烷菌和甲烷氧化菌的研究进展

湿地作为一种独特的生态系统,是大气中重要温室气体甲烷（CH₄）的"源",湿地CH₄的排放是CH₄的产生、传输和氧化三个过程的最终结果,其排放量与产甲烷菌（methanogens）和甲烷氧化菌（methanotrophs）的活动密切相关。本文对湿地甲烷代谢重要微生物产甲烷菌和甲烷氧化菌的分类、特点、代谢途径、分子生态学研究现状及影响湿地产甲烷菌和甲烷氧化菌的重要环境因子等方面进行了综述,旨在促进我国湿地产甲烷及甲烷氧化菌群的领域更加系统和深入的研究,为有效调控湿地CH₄代谢,减少CH₄排放通量提供参考。     

Effect of bio-column composed of aged refuse on methane abatement – A novel configuration of biological oxidation in refuse landfill

An experimental bio-column composed of aged refuse was installed around the exhaust pipe as a new way to mitigate methane in refuse landfill.One of the objectives of this work was to assess the effect of aged refuse thickness in bio-column on reducing CH 4 emissions.Over the study period,methane oxidation was observed at various thicknesses,5 cm (small size),10 cm (middle size) and 15 cm (large size),representing one to three times of pipeline diameters.The middle and large size both showed over 90% methane conversion,and the highest methane conversion rate of above 95% occurred in the middle-size column cell.Michaelis-Menten equation addressed the methanotrophs diffusion in different layers of the bio-columns.Maximum methanotrophic activity (V max) measured at the three thicknesses ranged from 6.4 × 10 3 to 15.6 × 10 3 units,and the half-saturation value (K M) ranged from 0.85% to 1.67%.Both the highest V max and K M were observed at the middle-size of the bio-column,as well as the largest methanotrophs population,suggesting a significant efficiency of methane mitigation happened in the optimum zone with greatest affinity and methanotrophic bacteria activities.Therefore,bio-column is a potential style for methane abatement in landfill,and the aged refuse both naturally formed and artificially placed in the column plays a critical role in CH 4 emission.     

Influence factors for the oxidation of pyrite by oxygen and birnessite in aqueous systems

The oxidation of exposed pyrite causes acid mine drainage, soil acidification, and the release of toxic metal ions. As the important abiotic oxidants in supergene environments, oxygen and manganese oxides participate in the oxidation of pyrite. In this work, the oxidation processes of natural pyrite by oxygen and birnessite were studied in simulated systems, and the influence of pH, Fe(II) and Cr(III) on the intermediates and redox rate was investigated. SO₄^2 − and elemental S were formed as the major and minor products, respectively, during the oxidation processes. Ferric (hydr) oxides including Fe(OH)₃ and goethite were formed with low degree of crystallinity. Low pH and long-term reaction facilitated the formation of goethite and ferric hydroxide, respectively. The rate of pyrite oxidation by birnessite was enhanced in the presence of air (oxygen), and Fe(II) ions played a key role in the redox process. The addition of Fe(II) ions to the reaction system significantly enhanced the oxidation rate of pyrite; however, the presence of Cr(III) ions remarkably decreased the pyrite oxidation rate in aqueous systems. The introduction of Fe(II) ions to form a Fe(III)/Fe(II) redox couple facilitated the electron transfer and accelerated the oxidation rate of pyrite. The present work suggests that isolation from air and decreasing the concentration of Fe(II) ions in aqueous solutions might be effective strategies to reduce the oxidation rate of pyrite in mining soils.     

木屑生物炭对填料土的氮磷吸附及雨水持留改良影响

现阶段生物滞留系统的填料土存在氮磷营养盐净化效果不稳定、雨水持留能力下降等问题.为评估木屑生物炭作为生物滞留系统填料土添加剂的改良效果,选用对照填料土和施用了木屑生物炭的改良填料土进行对比研究,通过理化性质测试、等温吸附实验、土柱实验和土水特征曲线测定,研究木屑生物炭对填料土的改良影响与优化机制.结果表明,木屑生物炭孔隙率大、比表面积大、饱和含水率高和CEC高,可优化填料土的结构,提升填料土的离子交换能力;木屑生物炭对填料土的氮磷吸附改良效果突出,对NH4+-N的最大吸附量提高了 2.80倍,去除率由31.30％提高至64.10％,对PO43--P的最大吸附量提高了 1.28倍,去除率由61.90％提高至90.00％;经木屑生物炭改良后,填料土的饱和含水率提高1.63倍,渗透系数提高2.43倍,在各含水率下的基质吸力明显增加.木屑生物炭的添加可优化生物滞留系统填料土的性能,加强对雨水径流中氮磷营养盐的吸附,提高系统的渗透性和雨水持留能力.     

Diversity of methanotrophs in Zoige wetland soils under both anaerobic and aerobic conditions

Zoige wetland is one of the most important methane emission centers in China. The oxidation of methane in the wetland a ects global warming, soil ecology and atmospheric chemistry. Despite their global significance, microorganisms that consume methane in Zoige wetland remain poorly characterized. In this study, we investigated methanotrophs diversity in soil samples from both anaerobic site and aerobic site in Zoige wetland using pmoA gene as a molecular marker. The cloning library was constructed according to the pmoA sequences detected. Four clusters of methanotrophs were detected. The phylogenetic tree showed that all four clusters detected were a liated to type I methanotrophs. Two novel clusters (cluster 1, cluster 2) were found to relate to none of the recognized genera of methanotrophs. These clusters have no cultured representatives and reveal an ecological adaptation of particular uncultured methanotrophs in Zoige wetland. Two clusters were belonging to Methylobacter and Methylococcus separately. Denaturing gradient gel electrophoresis gel bands pattern retrieved from these two samples revealed that the community compositions of anaerobic soil and aerobic soil were di erent from each other while anaerobic soil showed a higher metanotrophs diversity. Real-time PCR assays of the two samples demonstrated that aerobic soil sample in Zoige wetland was 1.5 times as much copy numbers as anaerobic soil. These data illustrated that methanotrophs are a group of microorganisms influence the methane consumption in Zoige wetland.     

长江口沉积物甲烷产生潜力与产甲烷菌群落特征

采用室内培养与高通量测序技术,研究了长江口沉积物产甲烷潜力及其产甲烷菌群落组成特征.结果表明,研究区沉积物甲烷排放速率为4.15～7.12 nmol·g~(-1)·d~(-1),且表现出厌氧区高、丰氧区低的特点.甲烷产生潜力为丰氧区大于厌氧区,说明甲烷在水体中氧化是减少甲烷排放的重要环境过程.研究区沉积物中产甲烷菌群落组成具有明显的差异.厌氧区沉积物产甲烷菌的优势群落为Methanococcoides(拟甲烷球菌属)、Methanosarcina(甲烷八叠球菌属)和Methanosaeta(甲烷鬃菌属),丰氧区沉积物为Methanosarcina(甲烷八叠球菌属)、Methanosaeta(甲烷鬃菌属)和Methanocella(甲烷胞菌属),因而缺氧过程会对产甲烷菌群落产生重要的影响.通过估算发现,研究区甲烷的排放量为2487～6819 t·a~(-1),表明长江口是甲烷排放的净产生源.因此,由缺氧过程导致的河口环境因子变化会影响甲烷的代谢循环过程及其微生物群落组成,进而对河口生态系统甲烷排放产生重要的影响.     

闽江口鳝鱼滩芦苇湿地沉积物甲烷产生与氧化潜力对外源物质输入的响应

研究河口湿地沉积物甲烷(CH4)产生和氧化对外源物质输入的响应,对环境保护及温室气体减排具有重要意义.本研究基于室内培养-气相色谱法,探讨了闽江河口半咸水芦苇(Phragmites australis)沼泽湿地沉积物CH4产生与氧化对不同外源物质(底物、电子受体和营养物质)输入的响应.结果表明:CH3OH(500 mg·kg-1)、C3H9N(500 mg·kg-1)和Fe2+(0~500 mg·kg-1)对CH4产生潜力起促进作用(p0.05);NO-3(0~500 mg·kg-1)、NO-2(0~500 mg·kg-1)、Fe3+(50 mg·kg-1)和NH+4(50~500 mg·kg-1)表现为抑制CH4产生潜力(p0.05);而0~50 mg·kg-1的CH3OH和C3H9N、0~500 mg·kg-1的CH3COOH、SO2-4、Mn4+、PO3-4和低剂量的NH+4(0~5 mg·kg-1)对CH4产生的影响不显著(p0.05).实验剂量内(0~500 mg·kg-1),Fe3+和Mn4+的添加可促进CH4氧化(p0.05);CH3COOH、CH3OH、C3H9N、NO-3、NO-2、SO2-4、NH+4和低剂量的PO3-4(0~50 mg·kg-1)对沉积物CH4氧化潜力均有显著的抑制作用(p0.05);而Fe2+对CH4氧化没有显著影响(p0.05).综合分析表明,CH3COOH、CH3OH、C3H9N、NO-3、NO-2、SO2-4、PO3-4、NH+4和Fe2+的输入对沉积物CH4产生和氧化的综合作用为增加CH4排放通量,而Fe3+和Mn4+输入的综合作用则与之相反.     

Characterization of Methylocystis strain JTA1 isolated from aged refuse and its tolerance to chloroform

To accelerate the efficiency of methane biodegradation in landfills,a Gram-negative,rod-shaped,non-motile,non-spore-forming bacterium,JTA1,which can utilize methane as well as acetate,was isolated from the Laogang MSW landfills,Shanghai,China.Strain JTA1 was a member of genus Methylocystis on the basis of 16S rRNA and pmoA gene sequence similarity.The maximum specific cell growth rates(μmax=0.042 hr-1,R2=0.995) was derived through Boltzmann simulation,and the apparent half-saturation constants(Km(app)=7.08mmol/L,R2=0.982) was calculated according to Michaelis-Menton hyperbolic model,indicating that Methylocystis strain JTA1 had higher-affinity potential for methane oxidation than other reported methanotrophs.By way of adding the strain JTA1 culture,the methane consumption of aged refuse reached 115mL,almost two times of control experiment.In addition,high tolerance of Methylocystis strain JTA1 to chloroform could facilitate the methane oxidation of aged refuse bio-covers.At the chloroform concentration of 50mg/L,the methane-oxidation rate of bio-cover reached 0.114mL/(day·g),much higher than the highest rate,0.0135mL/(day·g),of reported bio-covers.In conclusion,strain JTA1 opens up a new possibility for environmental biotechnology,such as soil or landfills bioremediation and wastewater decontamination.     

典型污染物包覆层中氯仿的沿程生物转化机制

为明晰氯仿（CF）在包覆层中的降解过程,构建了模拟覆盖层系统（SLCS）,并结合高通量测序技术首次系统分析了CF在SLCS中的沿程生物转化机制,结果表明,覆盖层可根据氧气含量分为有氧区（0~20cm）、缺氧区（20~40cm）和无氧区（>40cm）.高通量测序分析表明,有氧区的优势菌为甲烷氧化菌,其中I型菌Methylobacter（甲基杆菌属）及Ⅱ型菌Methylosinus（甲基弯菌属）居多,缺氧区甲烷氧化菌的相对丰度为13%左右,缺氧和无氧区中Anaeromyxobacter（厌氧粘细菌属）成为了优势CF厌氧降解菌.CF在有氧、缺氧和无氧条件下均有效降解.在缺氧和无氧区,CF经厌氧还原脱氯转化为二氯甲烷,部分二氯甲烷在Dehalobacter（脱卤素杆菌属）作用下产生乙酸盐、H₂和CO₂.在有氧区,其余二氯甲烷通过甲烷氧化菌共代谢降解.改变进气口通量发现,SLCS对甲烷的去除率与通量呈负相关关系（R²=0.80）,但甲烷氧化速率与通量呈正相关关系（R²=0.90）.与甲烷类似,SLCS对CF的去除率与进气口通量呈负相关关系（R²=0.86）,但降解速率与进气口通量呈正相关关系（R²=0.89）.此外,进气口通量的增加对CF好氧共代谢降解的促进作用大于厌氧还原脱氯降解.该研究对氯代烃类污染物的降解提供了新的基础,对该类污染物的原位生物修复提供了理论依据.     

利用方式对红壤硝化作用的水分效应的影响

风干过程是土壤水分丢失的过程,研究亚热带酸性土壤硝化作用对水分水平的响应,有助于分析干土效应对硝化作用影响.本试验以分别发育于第四纪红土(Quaternary red earth,Q)和红砂岩(Tertiary red sandstone,S)、利用方式为水稻(rice,R)与旱地(upland,U)的4个农田土壤的风干土为供试材料,分别加入铵态氮0和150mg·kg-1,在5个即时水分含量下室内培养35d.结果表明,土壤水分水平显著影响供试土壤的硝化作用(p0.01),但影响程度因利用方式而异.对供试条件下无外源铵输入的处理而言,旱地土壤QU和SU硝化率的极差分别为11%和8%,显著低于水稻土的硝化率极差(QR与SR分别为35%和20%).外源铵的加入增加了土壤硝化率的极差,土壤QR、QU、SR和SU硝化率的极差分别达到56%、26%、31%、26%,且随水分水平的增高,加铵有促进土壤酸化的趋势.总之,利用方式显著影响了土壤硝化作用对水分效应的响应,进而体现为干土效应的差异.