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1.
五华县崩岗洪积扇土壤分形特征及空间变异性研究   总被引:1,自引:0,他引:1  
以广东省五华县典型崩岗洪积扇为研究对象,通过GPS RTK获取从扇顶到扇缘64个采样点的坐标、高程信息,并采集土壤样品进行理化性质的测定及分析,通过分形理论、回归分析和地统计学相结合的方法研究洪积扇土壤分形特征和空间变异规律,以及分形维数与土壤颗粒组成和养分含量的相关关系。结果表明:土壤颗粒组成和养分含量具有明显的空间分异特征,且与分形维数的空间分布呈现出一定的规律性。从扇顶到扇缘,土壤粉粒、粘粒质量分数和养分含量逐渐增加,与分形维数呈显著正相关线性关系,砂粒质量分数则逐渐减少,与分形维数呈显著负相关线性关系,其中洪积扇土壤粘粒含量对土壤颗粒分形特征影响最大,相关系数达到0.969。研究结果表明,土壤分形维数是能反映土壤质地差异以及土壤肥力状况的一项综合性定量指标。  相似文献   

2.
崩岗是我国南方危害性极大的一种土壤侵蚀类型,尤其是产生的大量洪积物冲入农田,严重影响洪积扇农田质量。以苍梧县崩岗洪积扇为研究区域,采集洪积扇柑桔园不同培肥模式土样对其进行分析,探讨该地区沙化农田恢复过程中土壤颗粒组成及土壤养分的变化。结果表明:不同的培肥模式均能改良洪积扇土壤性质,土壤中的粉粒和黏粒含量有显著增加,养分含量也有显著提高。采用修正的内梅罗综合指数法对洪积扇土壤进行肥力评价可知,施化肥、施农家肥、种植绿肥+秸秆还田土壤肥力等级系数P值比对照区分别增加了42.11%,139.47%,135.53%,施肥模式以农家肥效果最佳。相关分析显示,土壤肥力指标与土壤砾石和砂粒含量呈显著负相关,而与粉粒和黏粒含量呈显著正相关。研究结果对改良崩岗洪积扇农田土壤,提高农业生产力和效益有重要的科学意义。  相似文献   

3.
以安溪县崩岗洪积扇农田为研究对象,采集不同培肥方式改良茶园的土样进行分析研究,探讨该地区沙化农田恢复过程中土壤颗粒组成及土壤养分的效应。结果表明:施化肥、施农家肥、施沼液肥、施沼液肥+种植绿肥均能有效改善洪积扇土壤理化性质。沙化农田经培肥后,砾石、砂粒含量均显著减少(P0.05),而粉粒、粘粒含量显著增加(P0.05);土壤CEC、有机质、氮磷钾含量也均呈显著增加趋势(P0.05)。土壤CEC、有机质、氮磷钾含量与砾石和砂粒含量呈显著负相关,与粉粒和粘粒含量则呈显著正相关。经分析,施农家肥与施沼液肥+种植绿肥总体效果较明显。  相似文献   

4.
崩岗作为南方红壤侵蚀区强度侵蚀的典型类型,是该区生态恢复和重建工作的一个难点。长汀水土流失区崩岗发育数量众多,本文选取长汀县濯田镇黄泥坑崩岗群内3条不同植被盖度(2%、20%和95%)的典型崩岗为研究对象,探讨不同植被盖度下崩岗土壤的质地特征,结果表明崩岗土壤机械组成以砂粒居多,粉粒与黏粒含量均较低,粗骨化现象明显;随着植被盖度的逐渐升高,崩岗土壤粉粒、黏粒含量呈增加趋势;沿集水坡面→崩壁→崩积体→沟道出口,崩岗土壤砂粒含量呈增加趋势。  相似文献   

5.
赣南崩岗侵蚀区不同部位土壤抗剪强度及影响因素研究   总被引:6,自引:1,他引:5  
为明确南方崩岗侵蚀区不同部位土壤抗剪强度的分布规律,探索在崩岗发育过程中土壤基本性质对抗剪强度指标的影响,以不同发育阶段崩岗各部位表层土(0~20cm)为研究对象,对土壤基本性质和抗剪强度的差异进行对比研究。结果表明:(1)随着崩岗的发育,表层土壤基本性质逐渐恶化,容重逐渐减小,颗粒组成粗骨质化现象明显,土壤有机质的含量与根系密度的变化,均随崩岗的发育呈现出典型的退化特征;(2)崩岗各部位黏聚力和内摩擦角的变化规律相似,集水区部位达到峰值,沟道部位达到最小值,随崩岗的发育呈明显下降趋势;(3)根系密度与黏聚力有良好的线性相关关系,砾石含量、粉粒含量和黏粒含量对崩岗土体内摩擦角有显著影响,可以用幂函数表示它们之间的关系;(4)试验以根系密度、砾石含量、粉粒含量和黏粒含量来表征土壤饱和状态下的抗剪强度,建立了在崩岗发育过程中饱和抗剪强度的预测方程(R2=0.891,P0.01),结果显示方程可信程度较高,预测效果较好。研究结果揭示了南方花岗岩崩岗区不同发育阶段抗剪强度的控制因素,为进一步防治水土流失提供理论依据。  相似文献   

6.
闽西南崩岗土壤理化性质及可蚀性分异特征   总被引:4,自引:0,他引:4  
崩岗是南方红壤区侵蚀沟在水力和重力交互作用下沟头遭受坍塌、陷蚀作用而形成的围椅状地貌,是该区域土壤侵蚀及生态系统退化的最高表现形式之一.为揭示崩岗侵蚀对土壤理化特性及可蚀性的影响,以福建省长汀县濯田镇黄泥坑崩岗群内植被盖度分别为2%,20%,95%的3个典型崩岗为研究对象,分别对崩岗系统内的集水坡面、崩壁、崩积体和沟口进行采样和理化特性的测定,并运用EPIC模型测算土壤可蚀性(K).结果表明:1)从集水坡面到崩壁、崩积体至沟口,3个崩岗的土壤砂粒质量分数、pH值和土壤密度呈升高趋势,粉粒、砂粒的质量分数和含水量呈下降趋势.2)1号和2号崩岗,集水坡面的土壤有机质质量分数最高,在崩壁最低;3号崩岗土壤有机质质量分数在崩壁处急剧下降,在崩积体中又明显上升.3)各崩岗中集水坡面、崩壁和崩积体的土壤颗粒组成、土壤密度和含水量差异较小,各土壤理化特性指标在沟口与集水坡面、崩壁和崩积体之间存在显著差异.4)崩岗系统内的集水坡面、崩壁、崩积体和沟口4个子系统的K值差异显著,1、2号崩岗呈现崩壁>崩积体>沟口>集水坡面的变化规律,而3号崩岗则表现为沟口>崩积体>崩壁>集水坡面的趋势.5)崩岗系统内的黏粒质量分数、pH值和有机质质量分数与土壤可蚀性关系密切,可以作为表征崩岗土壤可蚀性的有效指标.崩岗侵蚀造成土壤理化特性不断恶化,砂化严重,研究崩岗系统的土壤理化特性与可蚀性空间变化规律,对指导崩岗的恢复与重建具有重要意义.  相似文献   

7.
界限含水率是土壤水理性质的重要参数,可表征土体状态随含水量变化而变化的能力,与崩岗土体稳定性密切相关,对预测降雨和崩岗侵蚀关系具有重要意义。本研究选取桂东南区活动型、半稳定型和稳定型3种花岗岩崩岗为研究对象,分析各崩岗土壤界限含水率空间变异规律并利用通径分析方法揭示其影响因素。结果表明:崩岗各部位土壤界限含水率在空间上存在差异,活动型和半稳定型崩岗土壤液塑限在崩壁上部有最大值(液限分别为54.45%和57.08%,塑限分别为32.84%和34.04%),洪积锥顶部有最小值(液限分别为35.39%和30.72%,塑限分别为21.92%和20.23%);稳定型崩岗崩壁下部土壤液塑限最小(液限为33.78%,塑限为22.47%);随着崩岗发育逐渐稳定,各部位土壤界限含水率总体呈增加趋势。黏粒、有机质、总孔隙度和毛管孔隙度与土壤液塑限及塑性指数呈极显著正相关关系,其中,总孔隙度对土壤液塑限的影响最显著。总孔隙度、黏粒、有机质、毛管孔隙度对界限含水率变化起主导作用,总孔隙度、黏粒和毛管孔隙度分别是土壤液塑限、塑性指数和液性指数的主要影响因子。此研究结果可进一步明确崩岗侵蚀危害并确定高侵蚀风险部位,为崩岗危害预防与治理提供相关理论支撑。  相似文献   

8.
基于分形理论模拟花岗岩崩岗剖面土壤水分特征曲线   总被引:1,自引:0,他引:1  
崩岗是我国南方花岗岩地区特殊的土壤侵蚀现象,给山区经济造成了严重的影响.为了探索南方花岗岩地区崩岗侵蚀剖面的水分特性,明确水分与崩岗发育的关系,本研究采用野外调查采样与室内分析的方法,运用土壤粒径分形理论,并结合Brooks and Corey模型,模拟花岗岩崩岗剖面土壤水分特征曲线.选择通城县花岗岩崩岗剖面5个层次(表土层、红土层、过渡层、砂土层和碎屑层)采集土样,通过对土壤粒径分布和土壤含水量的测定,分析分形维数与土壤粒径之间的关系.同时,应用土壤粒径分形理论,模拟土壤水分特征曲线,基于估算结果与实测结果的比较,探讨分形方法估算土壤水分特征曲线的可行性.结果表明:崩岗剖面土壤黏粒质量分数越大,土壤粒径分维值越大;土壤粒径分维值越大,土壤水分特征曲线的分维值则越大,两者之间线性关系较好;运用分形理论,模拟土壤水分特征曲线的预测值与实测值具有良好的一致性,模拟结果的精度随土层的深度增加而增加,模拟效果以土壤黏粒和粉粒质量分数较少、砂粒质量分数较多的土壤效果较好.研究结果为花岗岩崩岗机理的探索奠定了基础,对崩岗水分的研究具有指导意义.  相似文献   

9.
崩岗侵蚀对土壤速效养分质量分数及化学计量比的影响   总被引:2,自引:0,他引:2  
为揭示崩岗侵蚀对土壤速效养分及化学计量比的影响,选取福建省长汀县黄泥坑崩岗群微度、中度和强度崩岗3处为研究对象,测定和分析了0 ~ 30 cm土层集水坡面、崩壁、崩积体以及沟道部位的土壤基本物理性质、速效养分及化学计量特征.结果表明:1)随着侵蚀强度的增加,硝态氮和速效磷质量分数表现为强度>中度>微度,中度侵蚀崩岗铵态氮质量分数最低,速效钾质量分数最高;从水平方向上,各速效养分质量分数表现为速效钾(AK)>铵态氮>硝态氮>速效磷(AP);垂直方向上,各速效养分质量分数大致随着土层深度而降低,但同一侵蚀强度内各质量分数差异较小.2)土壤速效氮为铵态氮与硝态氮的总和(AN),AN/AP比表现为微度>强度>中度,微度与中度差异显著(P <0.05);AK/AN比为中度>微度>强度,中度与强度差异显著(P <0.05);AK/AP比为微度>中度>强度,微度与中度差异显著(P<0.05).3)从集水坡面、崩壁、崩积体至沟道,3种类型崩岗的铵态氮和硝态氮平均值都呈降低的趋势,速效磷逐渐升高,速效钾在崩积体处最低,其他3个部位变化不大;土壤AN/AP、AK/AP比呈降低的趋势,AK/AN比在沟道处最高.4)速效养分化学计量比与砂粒、粉粒、pH和有机质皆密切相关,黏粒、容重和含水率对其影响相对较小.  相似文献   

10.
鄂东南花岗岩崩岗剖面土壤液塑限特征及影响因子分析   总被引:4,自引:0,他引:4  
崩岗是鄂东南花岗岩地区普遍存在的土壤侵蚀现象,给农业生态与经济发展带来了严重影响.研究崩岗剖面土壤液塑限特征不仅有利于崩岗侵蚀机理的研究,也为崩岗水土流失的防治改良提供理论依据.以通城县五里镇典型的花岗岩崩岗剖面为对象,通过室外采样结合室内液塑限联合测定实验,以及土壤理化性质测定,分析花岗岩崩岗剖面土壤液塑限规律及其影响因子,并探讨其与崩岗发育的关系.结果表明:花岗岩崩岗不同层次间的土壤液塑限差异显著,淋溶层和淀积层的液限值均大于50%,塑限值为30%左右,显著高于母质层;土壤液塑限值受黏粒质量分数、有机质质量分数、容重、游离氧化铁质量分数等影响,并随各因子的增大而增大,均呈正相关关系;其中,黏粒质量分数、游离氧化铁质量分数对土壤液塑限的影响更加显著(R2=0.860“,R2=0.908”).花岗岩崩岗土壤液塑限过渡层、母质层相对较低,在遇到降雨冲刷时,土体状态极易发生改变,易发生水土流失.利用土壤基本理化性质,可以对土壤液塑限进行预测,并为加强崩岗侵蚀机理研究及其治理提供依据.  相似文献   

11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响   总被引:2,自引:2,他引:0  
【目的】以富士(Fuji)、 秦冠(Qinguan)嫁接在平邑甜茶(Malus hupehensis Rehd.)上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水(ZZ)、 低氮正常水(DZ)、 正常氮干旱(ZG)、 低氮干旱(DG)。氮素和水分均设置两个水平,分别为正常氮(6 mmol/L NO-3-N)、 低氮(0.3 mmol/LNO-3-N)、 正常供水(保持盆中砂子相对含水量为饱和含水量的80%~85%)、 干旱处理(保持盆中砂子相对含水量为饱和含水量的60%~65%)。【结果】富士和秦冠的生物量(茎和叶)、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水(ZZ)>低氮正常水(DZ)>正常氮干旱(ZG)>低氮干旱(DG),并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水(ZZ)>低氮正常水(DZ)>正常氮干旱(ZG)>低氮干旱(DG); 氮、 钾元素含量在植株各部位的分布顺序依次是叶>根>茎,磷元素则是根>叶>茎;光合氮素利用效率(PNUE)和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水(DZ)处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱(DG)处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。  相似文献   

12.
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.  相似文献   

13.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,  相似文献   

14.
Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.  相似文献   

15.
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.  相似文献   

16.
李聃枫  朱春梧 《土壤》2020,52(3):561-566
自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。  相似文献   

17.
Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.  相似文献   

18.
Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.  相似文献   

19.
We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.  相似文献   

20.
Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.  相似文献   

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