Main Controlling Factors of Organic Matter Richness in a Permian Section of Guangyuan, Northeast Sichuan     

解习农  李红敬  熊翔  黄俊华  颜佳新  秦建中  腾格尔  李武 《中国地质大学学报(英文版)》2008,19(5):507-517

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Analysis and speciation of selenium ions in mine environments   总被引：2，自引：1，他引：1  

S. Sharmasarkar  G. F. Vance  F. Cassel-Sharmasarkar 《Environmental Geology》1998,34(1):31-38

 Aqueous extracts of five mine soil samples and a set of selenite (SeO₃ ^2–)–selenate (SeO₄ ^2–) solutions (0.5, 1, 5, 10 and 25 mg/l) were speciated using atomic absorption spectroscopy with hydride generation (AAS-HG) and ion chromatography (IC) to compare these methods for Se speciation. In another experiment, a SeO₃ ^2––SeO₄ ^2––SO₄ ^2– solution (25 mg/l) was reacted with CaO, MgO, MnO₂, CuO, La₂O₃, and WO₃ to evaluate the relative distribution of the Se species and SO₄ ^2– in the SORB (sorbed ions that were desorbed by NaOH), SOLN (equilibrium concentrations), CMPX (irreversibly sorbed and neutral ion pair complexes) fractions. The AAS-HG method was capable of analyzing Se as low as 0.002 mg/l, which was below the detection limit of IC. High concentration of SO₄ ^2– affected the chromatographic Se speciation either by shifting or overlapping Se peaks, in which AAS-HG was more useful. However, IC was capable of speciating aqueous SeO₃ ^2––SeO₄ ^2– directly without any sample pretreatment, whereas AAS-HG measured SeO₃ ^2–+SeO₄ ^2–, and SeO₃ ^2– in separate runs and SeO₄ ^2– was calculated from the difference, i.e., spectrophotometric speciation was an indirect method. For both Se species, AAS-HG and IC data were comparable within detection standard deviations. Ratios of different Se species at measured soil pH and pe indicated that SeO₃ ^2– or SeO₄ ^2– would be the dominant Se species; the p(SeO₄ ^2–/SeO₃ ^2–) values further suggested SeO₄ ^2– would be the major solution species. Except for CaO and MgO treatments, the %SeO₃ ^2– in the SORB fraction was ≥%SeO₄ ^2–. In the SOLN fraction %SeO₄ ^2– was ≥%SeO₃ ^2– for all oxides but CaO, whereas in the CMPX fraction this order was observed for only CaO and MnO₂. The %SeO₃ ^2– was highest in the SOLN fraction for all oxides but MgO and La₂O₃ for these two oxides SeO₃ ^2– dominated in CMPX and SORB fractions, respectively. The SOLN fraction also contained the highest %SeO₄ ^2– for all oxides but MgO which retained SeO₄ ^2– primarily in the SORB fraction. The %SeO₃ ^2– and %SeO₄ ^2– in the CMPX fraction were highest for MgO, thus, suggesting a possible formation of MgSeO₃ ⁰ and MgSeO₄ ⁰. A similar trend of SORB %SO₄ ^2– and SORB %SeO₄ ^2– was attributed to the analogous adsorption mechanisms (outer-sphere complexation). For all oxides but MgO, %SO₄ ^2– was <%SeO₄ ^2– in the SOLN fraction and ≥%SeO₄ ^2– in the CMPX fraction. Comparative ionic distributions provide an overall picture of the relative abundance of different Se species in various fractions associated with different oxides present in micro- and macrolevels in soils and geological materials. Received: 27 December 1995 · Accepted: 29 April 1997  相似文献   

Responses of diatoms to iron-enrichment (SEEDS) in the western subarctic Pacific, temporal and spatial comparisons     

Atsushi Tsuda  Hiroshi Kiyosawa  Akira Kuwata  Mamiko Mochizuki  Naonobu Shiga  Hiroaki Saito  Sanae Chiba  Keiri Imai  Jun Nishioka  Tsuneo Ono 《Progress in Oceanography》2005,64(2-4):189

Phytoplankton species composition was analyzed inside and outside of the iron-enriched patch during the SEEDS experiment. Before the iron-enrichment, the phytoplankton community consisted of similar proportions of pico-, nano- and micro-sized phytoplankton, and the micro-phytoplankton was dominated by the pennate diatom Pseudo-nitzschia turgidula. Although all the diatoms, except the nano-sized Fragilariopsis sp., increased during the two weeks of the observation period, the flora in the patch dramatically changed with the increase of phytoplankton biomass to a centric diatom-dominated community. Neritic diatoms, especially Chaetoceros debilis, showed higher growth rates than other diatoms, without any delay in the initiation of growth after the enrichment, and accounted for 90% of the micro-phytoplankton after day 9. In contrast, the oceanic diatoms showed distinct delays in the initiation of growth. We conclude that the responses of the diatoms to the manipulation of iron concentration were different by species, and the fast and intensive response of the phytoplankton to iron-enrichment resulted from the presence of a small amount of neritic diatoms at the study site. The important factors that determine the dominant species in the bloom are the potential growth rates under an iron-replete condition and the growth lag. Abundant species in the patch are widely distributed in the North Pacific and their relative contributions in the Oyashio area and at Stn KNOT are high from spring to summer. However, a characteristic difference of species composition between the SEEDS bloom and natural blooms was the lack of Thalassiosira and Coscinodiscus species in the patch, which usually account for a major part of the phytoplankton community under blooming conditions in the western North Pacific.  相似文献   

Quantifying Spatial Patterns of Intertidal Biodiversity: Is Movement Important?   总被引：2，自引：1，他引：2  

Ian C. Davidson  Anne C. Crook  & David K. A. Barnes 《Marine Ecology》2004,25(1):15-34

Abstract.  Small-scale patterns of low-, mid- and high-shore intertidal species density, richness and abundance were systematically examined to assess the potential influence of 'mobility' on spatial community dynamics and diversity. Mobile taxa outnumbered sessile species by approximately 2:1, whereas sessile individuals were over 12 times as numerous as mobile ones over the entire study site. Patterns of density, richness and abundance differed with shore level and substratum. The results also highlighted the importance of clearly distinguishing between species density and species richness when examining spatially quantitative data. The rank order of habitats from highest to lowest species density was not the same when analysed in order of species richness. The potential for the mobile proportion of assemblages to influence small-scale diversity assessment through movement was greater at mid- and high-shore zones because the ratio of mobile species was higher and abundance (relative to the lower shore) was low. These observations might reflect the relative influence of the land–sea gradient of immersion on diversity and mobility in intertidal communities. The influence of mobile organisms on marine ecosystem function may be significant because small-scale patterns of movement are known to positively influence biodiversity. High richness paired with low abundance, however, may result in underestimating the functional role of mobile intertidal species.  相似文献   

Environmental factors and pattern of riparian vegetation along the downstream sections of the Lower Ogun River,Nigeria     

《Singapore journal of tropical geography》2018,39(2):215-223

The River Continuum Concept (RCC) is an existing theory regarding the distribution of plant communities along riverbanks. This study is concerned with the pattern of riparian vegetation along the Lower Ogun River (LOR) in relation to the observed downstream variation of various environmental factors (bank height, width, gradient, distance, cross‐sectional area and particle size). The LOR transits between undisturbed and disturbed sections. Forty‐eight cross sections were established at bankfull stage along the river channel stretch of about 90 km. Environmental variables distribution were determined using standard field procedures. Gradient was estimated from a 1:50 000 topographical map. At each corridor along the study sites, a 0.1 ha sampling site was chosen, in which 10 transects of 100 m² were demarcated. In all, 332 individuals stratified under 80 species were recorded across the transects. The study revealed that total species richness (TSR) downstream decreases exponentially. TSR is significantly correlated with channel width, suggesting that hydraulic variable contributes more to the variation in TSR. The downstream total environmental factors revealed that width is inversely significant with downstream distance, suggesting that the river channel is narrower downstream. This affects plant life form distribution downstream and confirms why there is appearance of anthropogenic induced species downstream as against those in the upper course.  相似文献   

Above ground biomass and tree species richness estimation with airborne lidar in tropical Ghana forests     

《International Journal of Applied Earth Observation and Geoinformation》2016

Estimates of forest aboveground biomass are fundamental for carbon monitoring and accounting; delivering information at very high spatial resolution is especially valuable for local management, conservation and selective logging purposes. In tropical areas, hosting large biomass and biodiversity resources which are often threatened by unsustainable anthropogenic pressures, frequent forest resources monitoring is needed. Lidar is a powerful tool to estimate aboveground biomass at fine resolution; however its application in tropical forests has been limited, with high variability in the accuracy of results. Lidar pulses scan the forest vertical profile, and can provide structure information which is also linked to biodiversity. In the last decade the remote sensing of biodiversity has received great attention, but few studies focused on the use of lidar for assessing tree species richness in tropical forests.This research aims at estimating aboveground biomass and tree species richness using discrete return airborne lidar in Ghana forests. We tested an advanced statistical technique, Multivariate Adaptive Regression Splines (MARS), which does not require assumptions on data distribution or on the relationships between variables, being suitable for studying ecological variables.We compared the MARS regression results with those obtained by multilinear regression and found that both algorithms were effective, but MARS provided higher accuracy either for biomass (R² = 0.72) and species richness (R² = 0.64). We also noted strong correlation between biodiversity and biomass field values. Even if the forest areas under analysis are limited in extent and represent peculiar ecosystems, the preliminary indications produced by our study suggest that instrument such as lidar, specifically useful for pinpointing forest structure, can also be exploited as a support for tree species richness assessment.  相似文献   

Changes of Acute Toxicity of Organic Chemicals to Daphnia magna in the Presence of Dissolved Humic Material (DHM)     

C. E. W. Steinberg  A. Sturm  J. Kelbel  S. Kyu Lee  N. Hertkorn  D. Freitag  A. A. Kettrup 《洁净——土壤、空气、水》1992,20(6):326-332

With a series of substituted anilines, a series of substituted phenols as well as diazinon and tetrabromobisphenol-A alterations of short-term acute toxicity to the waterflea Daphnia magna have been studied in the presence of dissolved humic material (DHM). The results may be categorised as follows: No alteration in acute toxicity occurred with: tetrabromobisphenol-A, o-toluidine, 3,4-dichloroaniline, and pentachlorophenol. Toxicity decreases significantly with: diazinon, 4-chloroaniline, and 4-nitrophenol. Significant toxicity increases were observed with 2,4-dichlorophenol and 2,4,5-trichlorophenol. As demonstrated for diazinon, our study reveals that in the presence of DHM and light the chemical speciation of this chemical is altered and daughter products are produced most likely via photoactive species of DHM. Most probably the toxicity of both the parent and daughter compounds is changed as well. Alterations in acute toxicity of organic chemicals may thus be attributed to the adsorption to DHM as well as to the photoactive species mediated production of daughter products with toxicity different from that of the parent compounds.  相似文献   

美国弗蒙特州两种濒危鸟类保护成效研究     

王直军 《云南地理环境研究》1992,4(1):69-76

本文以美国弗蒙特(Vermont)州濒危鸟类游隼(Falco peregrinus)和潜鸟(Gavia immer)为例,反映鸟类与环境的关系,说明人类活动对环境及野生动物的影响,濒危动物的拯救工作应把环境综合治理放在重要位置。  相似文献   

2013年我国近海赤潮引发种种类和分布研究   总被引：1，自引：0，他引：1  

黄海燕  康林冲  杨翼  杨璐  刘书明  王秋璐  李潇 《海洋科学》2016,40(11):17-27

对2013年全国海洋环境监测1626个站位生物数据进行分析, 以近2001年～2013年在我国近海海域明确发生赤潮的生物作为赤潮引发种, 开展其种类组成和数量分布研究。结果显示: (1)我国近海赤潮引发种隶属于8门60种, 其中产毒种12种, 甲藻27种, 硅藻20种。(2)2013年共监测到上述赤潮引发种50种, 各监测站位种类数在0～25种之间, 平均密度在84～1.16×10¹¹个/m³之间, 赤潮引发种种类数、密度分布大致都呈现近岸至远海递减的趋势, 但在长江口及其邻近海域, 呈现先增大后减小趋势。(3)2013年各海区赤潮引发种种类数在36～42之间, 平均密度渤海>东海>南海>黄海, 多样性指数渤海>黄海>南海>东海, 都以中肋骨条藻(Skeletonema costatum)为优势种。(4)作为高频赤潮引发种,2013年中肋骨条藻(S. costatum)主要分布在我国近岸及近海海域; 夜光藻(Noctiluca scintillans)在我国近岸、近远海海域都有分布; 东海原甲藻(Prorocentrum donghaiense)主要分布在黄海和东海的近岸和近海海域; 米氏凯伦藻(Karenia mikimotoi)分布较为广泛, 但出现的站位较少; 红色中缢虫(Mesodinium rubrum)、赤潮异弯藻(Heterosigma akashiwo)、红色赤潮藻(Akashiwo sanguinea)只在很少区域有分布。该研究结果有助于摸清我国近海海域赤潮生物种类和分布状况, 可为赤潮的预警及其防灾减灾提供基础科学依据。  相似文献   

Ecological and species diversity of arid Mediterranean grazing land vegetation   总被引：7，自引：0，他引：7  

M. Noor Alhamad   《Journal of Arid Environments》2006,66(4):698-715

This study was conducted in the arid Mediterranean Reserve located in northern Jordan, representing a continuous grazed arid rangeland ecosystem. Quantitative analyses on species diversity in addition to phytogeographical analysis were conducted. Some ecological parameters such as, life forms, growth forms, species density and frequency were investigated. A total of 93 vascular plant taxa belonging to 78 genera and 26 families were reported. This constitutes about 4.3% of the total flora of Jordan. Reported taxa include 13 species of grasses, 69 forbs and 10 shrubs and semi-shrubs. The botanical survey pointed to the presence of four rare species in Jordan. Plant species were classified into 28 functional groups. Pairwise correlation analyses among the most abundant species, showed that neutral associations dominated (75%) those communities, followed by positive associations (19%), while only (6%) showed negative association. Positive association may be attributed to direct facultative mutualism, or to physical environmental heterogeneity. Such a positive cooperation in the plant community can significantly maintain species diversity in adverse environments.The relationship between primary productivity and species richness showed a humpbacked pattern. Maximum richness corresponded to a biomass level of 300–400 g m⁻². However, a sinusoidal curve-fitting model explained the relationship between graminoids biomass and species richness. These findings pointed to the adaptation of plant taxa to livestock grazing and to the small-scale spatial and environmental heterogeneity in arid Middle Eastern Mediterranean rangelands. Results suggest that optimal biodiversity conservation for the arid Middle Eastern grazing lands should consider their high level of spatial heterogeneity. Rangeland managers should adopt grazing plans that apply a range of grazing pressure across the area so as to maintain diversity at local and regional scales.  相似文献