Semiconducting Mineral Photocatalytic Regeneration of Fe²⁺ Promotes Carbon Dioxide Acquisition by Acidithiobacillus ferrooxidans     

LI Yan  LU Anhuai  WANG Xin  DING Hongrui  WANG Changqiu 《《地质学报》英文版》2013,87(3):761-766

Chemoautotrophic organisms have once been excluded from the development of universally applicable CO2 fixation technology due to its low production yields of biomass. In this study, we used Acidithiobacillus ferrooxidans (A.f.) as a model chemoautotrophic microorganism to test the hypothesis that exogenetic photoelectrons from semiconducting mineral photocatalysis can enable the regeneration of Fe2+ that could be then used by A.f. and support its growth. In a simulated electrochemical system, where exogenetic electrons were provided by an electrochemical approach, an accelerated growth rate of A.f. was observed as compared with that in traditional batch cultivation. In a coupled system, where light-irradiated natural rutile provided the primary electron source to feed A.f., the bacterial growth rate as well as the subsequent CO2 fixation rate was demonstrated to be in a light-dependent manner. The sustaining flow of photogenerated electrons from semiconducting mineral to bacteria provided an inexhaustible electron source for chemoautotrophic bacteria growth and CO2 fixation. This finding might contribute to the development of novel effective CO2 fixation technology.  相似文献   

大口径瓦斯抽排井注浆固管过程套管稳定性分析     

陈江红  孙家应 《中国煤炭地质》2012,(10):57-59,69

为了研究大口径瓦斯抽排钻井注浆固管过程中套管的稳定性,应用伯努利方程分析了注浆固管过程中浆液的动压力的变化规律。分析认为：注浆固管期间,若注浆管内过流面积小于套管与孔壁之间的过流面积,随着泵量的增加,导致套管外流体压力增加;当套管外与套管内压力差大于套管抗外挤强度时,套管发生失稳（瘪管）。结合工程实例,对套管失稳机理进行分析,提出了在固管过程中要控制泵量的建议。  相似文献   

Influence of understory removal, thinning and P fertilization on N₂fixation in a mature mesquite (Prosopis glandulosavar.glandulosa) stand     

Guillermo M López Villagra  Peter Felker 《Journal of Arid Environments》1997,36(4):591-610

The natural abundance¹⁵N/¹⁴N method was used to estimate the influence of silvicultural and P fertilization treatments on N accretion, N₂fixation and N partitioning among tissues in a mature mesquiteProsopis glandulosavar.glandulosastand in Texas. The silvicultural treatments consisted of understory removal, herbicide treatment of brushy resprouts, thinning trees to single stems and 100 kg ha⁻¹P fertilization. The trees had a mean basal diameter of 17·8 cm with 8 to 35 cm range. The stand was slow growing with the increase in dry matter ranging from 0·465 Mg ha⁻¹year⁻¹to 0·701 Mg ha⁻¹year⁻¹for the 8 years after the treatments were applied. N accretion after 8 years ranged from 3·1 kg ha⁻¹year⁻¹to 4·4 kg ha⁻¹year⁻¹.Due to the range in δ¹⁵N of the leaves, twigs, branches and trunk, we used the weighted (by biomass) average δ¹⁵N per tree in calculations of the percent N derived from N₂fixation (%Ndfa). There was considerable variability in δ¹⁵N of the reference plants, i.e. from 3·3 to 5·9. In contrast there was low variability in the background δ¹⁵N of nearby soils (7·0±1·0). As the total above-ground biomass δ¹⁵N of a grass grown outside the influence of mesquite (7·8±0·58) had the same δ¹⁵N as the soil (7·5±1·0), we used the grass outside the influence of mesquite and the weighted tree mean δ¹⁵N to calculate % of N derived from N₂fixation.The decrease in intraspecific competition by thinning multistemed trees to single stemmed trees was the only treatment that significantly (p= 0·0001) increased growth. Interspecific competition, i.e. understory removal, did not increase growth. There were no significant differences in total N production or N fixation among treatment means. The most striking result was the highly positive correlation between tree δ¹⁵N and total N per tree and biomass per tree (R²= 0·90,F= 164·4, df. = 18, mean square error (MSE) = 0·155,p= 0·0001). This implies that the younger trees colonizing infertile soils relied more heavily on N₂fixation than larger trees which accumulated 1200 kg ha⁻¹more N under their canopies. The percentage N derived from N₂fixation ranged from 63 to 73% in the various treatments. Despite the high percentage of N derived from N₂fixation, the N₂fixation of the stand was very low, i.e. 1·98 to 2·80 kg N ha⁻¹year⁻¹, due to the low growth of the stand. We believe that comparisons of the whole tree weighted δ¹⁵N to background soil δ¹⁵N provides a more reasonable approach to estimate % N₂fixation than comparisons of leaves of fixers and reference plants.  相似文献   

The nitrogen cycle of an East Coast, U.K. saltmarsh: II. Nitrogen fixation, nitrification, denitrification, tidal exchange     

S. Azni b Abd. Aziz  D. B. Nedwell 《Estuarine, Coastal and Shelf Science》1986,22(6)

Measurements of nitrogen fixation (acetylene reduction) showed greatest rates in the saltmarsh pans with a benthic layer of cyanobacteria present. The smallest amount of nitrogen fixation occurred on the marsh surface where a Puccinellia maritima/Halimione portulacoides plant association shaded the underlying sediment. Phototrophic nitrogen fixation was always greater than dark, chemotrophic, bacterial fixation.Only a small proportion of the total amount of ammonium, which was formed during detrital breakdown, was nitrified to nitrate. Although there is a high capacity for bacterial nitrate reduction in these sediments, the process is limited by low nitrate availability and most nitrate upon reduction is converted to ammonium rather than being denitrified to gaseous products. Denitrification does not, therefore, result in any great loss of nitrogen from the saltmarsh.There was little net import or export of nitrogen on an annual basis, although nitrate and organic-N in small particulate material was removed from tidal water by the marsh, and there was net annual export of ammonium, dissolved organic-N and organic-N in large particulate material. Losses of nitrogen by the small net tidal export and by denitrification were approximately balanced by nitrogen fixation. It was concluded that the nitrogen cycle of the Colne Point saltmarsh was balanced on an annual basis, with most nitrogen being recycled within the marsh. The saltmarsh did not apparently act as a net source of nitrogen for the adjacent estuary, although it may act as an important processor of nitrogen, removing some forms of nitrogen such as nitrate from tidal water while exporting other forms of nitrogen such as dissolved organic-N.  相似文献   

A 9-year increasing trend in mesozooplankton biomass at the Hawaii Ocean Time-series Station ALOHA   总被引：2，自引：0，他引：2  

Sheridan  Cecelia C; Landry  Michael R 《ICES Journal of Marine Science》2004,61(4):457-463

  相似文献   

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects     

Troussellier M.  Courties C.  Zettelmaier S. 《Estuarine, Coastal and Shelf Science》1995,40(6)

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.  相似文献   

Sources and transformations of N in reclaimed coastal tidelands: evidence from soil δ<Superscript>15</Superscript>N data     

Jin-Hyeob Kwak  Woo-Jung Choi  Sang-Sun Lim  Seung-Heon Lee  Sang-Mo Lee  Scott X. Chang  Jae-Woon Jung  Kwang-Sik Yoon  Soo-Myung Choi 《Environmental Geology》2008,53(6):1331-1338

Electrical conductivity of saturated soil extracts (EC_e) in three reclaimed tideland (RTL) soils on the west coast of Korea decreased with time since reclamation, indicating natural desalinization through leaching of salts by precipitation water. Soil N concentration increased with decreasing EC_e. With the increase in soil N concentration, the δ¹⁵N decreased, likely caused by the input of ¹⁵N-depleted N sources. As N₂-fixing plant species were found in the oldest RTL, atmospheric N₂ fixation likely contributed to the increase in soil N concentration in the oldest RTL. Negative δ¹⁵N (−7.1 to −2.0‰) of total inorganic N (NH₄ ⁺+NO₃ ⁻) and published data on N deposition near the study area indicate that atmospheric N deposition might be another source of N in the RTLs. Meanwhile, the consistently negative δ¹⁵N of soil NO₃ ⁻ excluded N input from chemical fertilizer through groundwater flow as a potential N source, since NO₃ ⁻ in groundwater generally have a positive δ¹⁵N. The patterns of δ¹⁵N of NH₄ ⁺ (+2.3 to +5.1‰) and NO₃ ⁻ (−9.2 to −5.0‰) suggested that nitrification was an active process that caused ¹⁵N enrichment in NH₄ ⁺ but denitrification was probably minimal which would otherwise have caused ¹⁵N enrichment in NO₃ ⁻. A quantitative approach on N budget would provide a better understanding of soil N dynamics in the studied RTLs.  相似文献   

Influence of high-fluorine environmental background on crops and human health in hot spring-type fluorosis-diseased areas     

De Lan  Daishe Wu  Ping Li  Tengsheng Wang  Chengguang Chen  Wuyi Wang 《中国地球化学学报》2008,27(4):335-341

Drinking water-type fluorosis is the most harmful endemic disease in China with the largest number of sufferers. Although the implementation of the policy to alter water sources to lower fluoride level has effectively controlled the spread of this kind of endemic disease, its prevalence could not thoroughly be stopped because the high-fluoride environmental background in these endemically diseased areas could still do harm to human health through food chain. Therefore, it is necessary to conduct a more deep-going study on the drinking water-type fluorosis. To investigate the effect of high fluorine environmental background on crops and human health in the hot spring-type fluorosis-diseased areas, local water, paddy soil, rice, whole vegetables and soils around their roots were sampled for analysis. The results were compared with those of the control groups in fluorosis-free areas which are similar to the fluorosis-diseased areas both in natural background and in social background. It is indicated that rice and vegetables can accumulate water-soluble fluorine either in soils or in irrigating water, and different crops have different abilities of fixing fluorine. The contents of fluorine in different parts of vegetables in the fluorosis-diseased and fluorosis-free areas were statistically categorized. The results showed that the fluorine contents of roots, tubers, leaves and flowers of vegetables in the fluorosis-diseased areas are 3.56, 1.17, 3.07 and 3.23 mg/kg, respectively. However, comparisons showed that in the fluorosis-free areas, the fluorine contents are 2.17, 0.70, 1.91 and 2.52 mg/kg, respectively. Moreover, different parts of a crop also show significantly different fluorine fixation abilities. It is demonstrated that the fluorine contents of the strongly metabolic parts are relatively high. For example, the fluofine contents of roots, leaves and flowers of vegetables are much higher than those of stems. The fluorine fixation ability of seeds is very weak. In order to reduce the risk of human body＇s  相似文献   

近35年三北防护林体系建设工程的防风固沙效应   总被引：3，自引：0，他引：3  

黄麟  祝萍  肖桐  曹巍  巩国丽 《地理科学》2018,38(4):600-609

通过分析三北工程区生态系统防风固沙服务量变化,进而评价工程的防风固沙效应。结果表明：① 近35 a,三北工程区林地面积持续增加、草地面积持续减少,特别是半干旱风沙区和黄土高原区。植被覆盖度在前20 a持续增加,近15 a则呈现先下降而后略微增加趋势。②土壤风蚀模数持续减少,近15 a减幅远高于前20 a,沙地、草地、其它类型转林地或转草地区域的减幅尤为明显。生态系统防风固沙服务保有率呈上升态势,干旱荒漠区增幅显著。草地和沙地为工程区生态系统防风固沙服务总量贡献了71%,且转草地区域的贡献高于转林地区域。③ 考虑到植被好转同时受气候变化和人类活动的影响,以风场减弱为主的气候变化导致土壤风蚀力减弱与三北防护林等生态工程对生态系统防风固沙服务变化的贡献率分别介于85%~89%和11%~15%之间。  相似文献   

腾格里沙漠东南缘生物土壤结皮对土壤理化性质的影响   总被引：3，自引：1，他引：2  

都军  李宜轩  杨晓霞  李云飞  马晓俊 《中国沙漠》2018,38(1):111-116

生物土壤结皮是荒漠生态系统地表景观的重要组成部分,在沙化土地恢复和流沙固定中起着重要作用。研究了腾格里沙漠东南缘固沙植被区不同类型生物土壤结皮理化性质及结皮发育对下层土壤性质的影响。结果表明：结皮层厚度、孔隙度、黏粉粒和田间持水量以及有机碳、无机碳、全氮、碱解氮、速效磷、速效钾含量和电导率均表现为藓类结皮 > 混生结皮 > 地衣结皮 > 藻类结皮;砂粒含量和容重表现为藻类结皮 > 地衣结皮> 混生结皮 > 藓类结皮。结皮下0~2 cm和2~5 cm土层理化性质表现出与结皮层相同的变化规律。总体上,生物土壤结皮对下层土壤理化性质的影响表现为藓类结皮和混生结皮大于地衣结皮和藻类结皮;而结皮对下层土壤理化性质的影响随土壤深度的增加而减小。生物土壤结皮的拓殖和发育是荒漠生态系统成土过程和土壤质量的关键影响因素。  相似文献