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71.
The emission of N2 is important to remove excess N from lakes, ponds, and wetlands. To investigate the gas emission from water, Gao et al. (2013) developed a new method using a bubble trap device to collect gas samples from waters. However, the determination accuracy of sampling volume and gas component concentration was still debatable. In this study, the method was optimized for in situ sampling, accurate volume measurement and direct injection to a gas chromatograph for the analysis of N2 and other gases. By the optimized new method, the recovery rate for N2 was 100.28% on average; the mean coefficient of determination (R2) was 0.9997; the limit of detection was 0.02%. We further assessed the effects of the new method, bottle full of water, vs. vacuum bag and vacuum vial methods, on variations of N2 concentration as influenced by sample storage times of 1, 2, 3, 5, and 7 days at constant temperature of 15°C, using indices of averaged relative peak area (%) in comparison with the averaged relative peak area of each method at 0 day. The indices of the bottle full of water method were the lowest (99.5%-108.5%) compared to the indices of vacuum bag and vacuum vial methods (119%-217%). Meanwhile, the gas chromatograph determination of other gas components (O2, CH4, and N2O) was also accurate. The new method was an alternative way to investigate N2 released from various kinds of aquatic ecosystems. 相似文献
72.
Impact of payments for environmental services and protected areas on local livelihoods and forest conservation in northern Cambodia 总被引:1,自引:0,他引:1
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The potential impacts of payments for environmental services (PES) and protected areas (PAs) on environmental outcomes and local livelihoods in developing countries are contentious and have been widely debated. The available evidence is sparse, with few rigorous evaluations of the environmental and social impacts of PAs and particularly of PES. We measured the impacts on forests and human well‐being of three different PES programs instituted within two PAs in northern Cambodia, using a panel of intervention villages and matched controls. Both PES and PAs delivered additional environmental outcomes relative to the counterfactual: reducing deforestation rates significantly relative to controls. PAs increased security of access to land and forest resources for local households, benefiting forest resource users but restricting households’ ability to expand and diversify their agriculture. The impacts of PES on household well‐being were related to the magnitude of the payments provided. The two higher paying market‐linked PES programs had significant positive impacts, whereas a lower paying program that targeted biodiversity protection had no detectable effect on livelihoods, despite its positive environmental outcomes. Households that signed up for the higher paying PES programs, however, typically needed more capital assets; hence, they were less poor and more food secure than other villagers. Therefore, whereas the impacts of PAs on household well‐being were limited overall and varied between livelihood strategies, the PES programs had significant positive impacts on livelihoods for those that could afford to participate. Our results are consistent with theories that PES, when designed appropriately, can be a powerful new tool for delivering conservation goals whilst benefiting local people. 相似文献
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针对深埋高地应力水平岩层掌子面开挖稳定性及支护结构失效问题,以大峡谷隧道为工程背景,通过现场测试、室内试验、数值模拟等方法,探究深埋高地应力水平岩层失稳机理及控制措施。研究结果表明:坚硬岩体被节理面切割后,在高地应力作用下容易发生挤压破碎,破碎岩体遇水发生软化,导致掌子面发生大范围塌方,初支和超前支护失效;隧道开挖后岩层发生不均匀沉降,浅部岩层最先发生弯折破坏,层内块体错动滑移,继而向上方岩层发展,并伴随层间分离和层内裂隙发育,最终形成宏观破裂面;提出的台阶法、2 m开挖进尺、砼喷层、双层小导管、提高初支强度的整体优化控制措施,可有效提高现场支护效果。 相似文献
74.
针对传统植被资源调查方法工作量大、成本高、效率低的问题,利用高分辨率无人机遥感影像,联合地物光谱-纹理-空间信息,构建了一种适用于描述城市不同植被种类的多维特征空间,在此基础上对三种应用广泛的分类算法(基于像素的、面向对象的支持向量机及深度学习Mobile-Unet语义分割模型)开展了对比分析研究.结果表明:本文提出的联合地物光谱-纹理-空间信息的特征空间构建方法能够有效地描述城市不同类型植被的特征差异,提升影像分割、植被分类的精度;在分类精度上,基于像素和面向对象的支持向量机分类结果的总体精度均超过90%,深度学习方法的总体分类精度为84%;在算法效率上,传统机器学习方法也优于深度学习方法.因此,得出结论针对城市小区域、小样本的植被精细分类,传统机器学习分类方法比深度学习方法效果更好. 相似文献
75.
Abstract: Hydrothermal vents are deep‐sea ecosystems that are almost exclusively known and explored by scientists rather than the general public. Continuing scientific discoveries arising from study of hydrothermal vents are concommitant with the increased number of scientific cruises visiting and sampling vent ecosystems. Through a bibliometric analysis, we assessed the scientific value of hydrothermal vents relative to two of the most well‐studied marine ecosystems, coral reefs and seagrass beds. Scientific literature on hydrothermal vents is abundant, of high impact, international, and interdisciplinary and is comparable in these regards with literature on coral reefs and seagrass beds. Scientists may affect hydrothermal vents because their activities are intense and spatially and temporally concentrated in these small systems. The potential for undesirable effects from scientific enterprise motivated the creation of a code of conduct for environmentally and scientifically benign use of hydrothermal vents for research. We surveyed scientists worldwide engaged in deep‐sea research and found that scientists were aware of the code of conduct and thought it was relevant to conservation, but they did not feel informed or confident about the respect other researchers have for the code. Although this code may serve as a reminder of scientists’ environmental responsibilities, conservation of particular vents (e.g., closures to human activity, specific human management) may effectively ensure sustainable use of vent ecosystems for all stakeholders. 相似文献
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77.
Preimplantation genetic diagnosis (PGD) was developed more than a decade ago to offer an alternative to prenatal diagnosis for couples at risk of transmitting an inherited disease to their offspring. Portuguese-type familial amyloidotic polyneuropathy (FAP type I), is an autosomal dominant disease presenting an inherited mutation in the gene encoding the plasma protein transthyretin (TTR). We here report the first protocol for single-cell detection of the Met30 mutation in FAP type I and its application to PGD. A nested PCR reaction for exon 2 of the TTR gene was developed. The PCR product was then analysed by restriction enzyme analysis and SSCP allowing the detection of the point mutation. Ten clinical cycles were performed in seven couples. From the 93 metaphase II (MII) injected oocytes, 82 were normally fertilized and 78 were biopsied. A positive signal in the nested PCR reaction was obtained in 61 blastomeres, corresponding to a DNA amplification efficiency of 78.2%. No allele dropout (ADO) or contamination were detected. A biochemical pregnancy was obtained in three cases and a clinical pregnancy in one couple is actually in normal evolution. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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80.
深水型水库热分层诱导水质及真菌种群结构垂向演替 总被引:9,自引:9,他引:0
水体真菌种群在调控水库生态系统健康过程中发挥重要作用,为探明热分层诱导深水型水库水体真菌种群结构垂向演替特征,采集金盆水库主库区0.5、10、25、40、60和70 m水深水样,分析水质参数、并运用高通量DNA测序技术诊断水库水体真菌种群结构垂向异质性.结果表明,金盆水库表层水温最高为22.33℃,底层最低为7.21℃(P0.05).水体溶解氧(DO)随水深增加显著降低(P0.05),电导率、总磷(TP)和铁含量随着水深增加显著升高(P0.05),垂向形成稳定的变温层、斜温层和等温层结构.水体真菌种群高通量DNA测序共发现1 247个OTUs,隶属4门14纲39属,主要包括接合菌门(Zygomycota)、担子菌门(Basidiomycota)、子囊菌门(Ascomycota)和壶菌门(Chytridiomycota).等温层水体真菌种群Shannon指数和Chao 1多样性指数最高,分别为3.45和360,显著高于斜温层水体(P0.05).红酵母属(Rhodotorula,27.23%)、链格孢属(Alternaria,24.28%)、分子孢子菌属(Cladosporium,22.98%)、链格孢属(Alternaria,32.00%)、亚隔孢壳属(Didymella,17.47%)和分子孢子菌属(Cladosporium,28.17%)分别是0.5、10、25、40、60、70 m的优势菌属,不同水深均存在大量未知真菌(Unclassified).热图(heat map)结果表明,热分层期间金盆水库水体真菌种群结构垂向分布差异显著、不同水层具有不同的真菌种群结构.主成分分析(PCA)表明水温、DO、TP、电导率是调控水体真菌种群结构垂向异质性的主要水质因子.该研究结果为水源水库热分层期间水质与真菌群落的偶联机制提供科学依据. 相似文献