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481.
Potential allelopathic interactions between Skeletonema costatum and Alexandrium minutum were investigated using mixed cultures and culture filtrate in nutrient-replete medium. A. minutum growth was inhibited when grown in S. costatum filtrate, with the inhibitory effect directly proportional to the percentage of filtrate added. This demonstrates that the release of allelopathic compounds caused the growth inhibition. In contrast, the filtrate of A. minutum exerted no allelopathic activity on S. costatum. An autoinhibitory compound (15(S)-HEPE) extracted and purified from S. costatum culture was added to cultures of both S. costatum and A. mintum. This substance could depress S. costatum growth, but showed no significant inhibitory activity on A. minutum. This documented a second type of allelochemical interaction, termed auto-allelopathy, caused by a different compound from the one or ones that affected A. minutum in the co-cultures with added crude filtrate. Further studies are needed to explore the relative importance of these two types of allelopathy as factors influencing the competition between S. costatum and A. minutum in the field. Furthermore, given the observed decrease in diatom dominance relative to dinoflagellates with increasing eutrophication, one can predict that toxic species like A. minutum might become more prevalent in the future in the East China Sea if the trend of increasing pollution of coastal waters continues. 相似文献
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483.
Xiaojun Wang Mingsheng Jia Xiaohai Chen Ying Xu Xiangyu Lin Chih Ming Kao Shaohua Chen 《Waste management (New York, N.Y.)》2014,34(7):1156-1164
With limited assessment, leachate treatment of a specified landfill is considered to be a significant source of greenhouse gas (GHG) emissions. In our study, the cumulative GHG emitted from the storage ponds and process configurations that manage fresh or aged landfill leachate were investigated. Our results showed that strong CH4 emissions were observed from the fresh leachate storage pond, with the fluxes values (2219–26,489 mg C m?2 h?1) extremely higher than those of N2O (0.028–0.41 mg N m?2 h?1). In contrast, the emission values for both CH4 and N2O were low for the aged leachate tank. N2O emissions became dominant once the leachate entered the treatment plants of both systems, accounting for 8–12% of the removal of N-species gases. Per capita, the N2O emission based on both leachate treatment systems was estimated to be 7.99 g N2O–N capita?1 yr?1. An increase of 80% in N2O emissions was observed when the bioreactor pH decreased by approximately 1 pH unit. The vast majority of carbon was removed in the form of CO2, with a small portion as CH4 (<0.3%) during both treatment processes. The cumulative GHG emissions for fresh leachate storage ponds, fresh leachate treatment system and aged leachate treatment system were 19.10, 10.62 and 3.63 Gg CO2 eq yr?1, respectively, for a total that could be transformed to 9.09 kg CO2 eq capita?1 yr?1. 相似文献
484.
Maria Tengö Eduardo S. Brondizio Thomas Elmqvist Pernilla Malmer Marja Spierenburg 《Ambio》2014,43(5):579-591
Indigenous and local knowledge systems as well as practitioners’ knowledge can provide valid and useful knowledge to enhance our understanding of governance of biodiversity and ecosystems for human well-being. There is, therefore, a great need within emerging global assessment programs, such as the IPBES and other international efforts, to develop functioning mechanisms for legitimate, transparent, and constructive ways of creating synergies across knowledge systems. We present the multiple evidence base (MEB) as an approach that proposes parallels whereby indigenous, local and scientific knowledge systems are viewed to generate different manifestations of knowledge, which can generate new insights and innovations through complementarities. MEB emphasizes that evaluation of knowledge occurs primarily within rather than across knowledge systems. MEB on a particular issue creates an enriched picture of understanding, for triangulation and joint assessment of knowledge, and a starting point for further knowledge generation. 相似文献
485.
采用分光光度法和连续碘量法研究了二氧化氯(ClO2)氧化二价铁离子的反应动力学。研究结果表明,该化学反应计量关系为:5Fe2++ClO2+4H+→5Fe3++Cl-+2H2O,建立了ClO2氧化二价铁离子的反应动力学方程为-rFe2+≈1.6678×106EXP(-5179.7/T)[ClO2][Fe2+](pH=6.0);在pH=6.0和T=293 K的条件下,该反应对于ClO2和二价铁离子均为一级,总反应级数为二级,二级反应速率常数k值为0.03556×103L/(mol.s),该反应活化能Ea为43.1 kJ/mol;表明ClO2除铁的氧化反应在一般水处理条件下即能进行。 相似文献
486.
为更好地研究环境中高氯酸盐离子(ClO-4)与硝酸盐氮(NO-3-N)混合污染的共同降解。选用pcrA、cld基因表征参与高氯酸盐降解的细菌,NirS基因表征反硝化细菌,16S rRNA基因表征整个细菌群落的活性。通过对高浓度硝酸盐氮与高氯酸盐混合污染降解体系内不同时间点不同种基因的表达分析,实时定量的反应复杂环境中混合污染物生物降解机理。结果表明,在外源添加足够的醋酸盐作为电子供体条件下,NO-3-N与ClO-4质量浓度比为5∶1时,硝酸盐氮的存在不会完全抑制ClO-4的降解,当NO-3-N降解完全时,可以加快ClO-4的降解过程。在有硝酸盐氮存在的混合降解体系内,pcrA和cld基因与ClO-4的浓度变化之间的相关性不是很高,证明该功能基因对复杂环境中特定生物群落的表征有一定局限性。 相似文献
487.
选取南盘江流域3个水文站52 a(1961~2012年)的逐月径流资料,联合两个相邻站点,分别计算标准化径流指数(SSFI),运用游程理论识别52 a来不同站点干旱特征,并用Pair copula函数计算不同站点的联合重现期。结果表明:(1)52 a来3个站点干旱特征值的最大值都出现在2011~2012年;从单个站点看,52 a来沾益站的干旱次数、最大干旱历时、最大干旱烈度均大于高谷马站和江边街站,最大干旱峰值出现在江边街站;从联合站点看,中游以上高谷马站和沾益站的干旱特征值均大于中游以下高谷马站和江边街站,3个站点联合识别的干旱特征值大于中下游站点联合识别干旱特征值,小于中上游站点联合识别干旱特征值,上游干旱更严重;(2)Frank Pair copula函数的RMSE、AIC和BIC值最小,拟合程度最高,适合运用于南盘江流域干旱频率分析中;(3)运用Frank Pair copula函数计算得到3个水文站点2009~2012年的连续干旱重现期都在100~200 a,是52 a来最严重的一次干旱 相似文献
488.
Haibo Zhang Yongming Luo Ying Teng Hongfu Wan 《Environmental science and pollution research international》2013,20(8):5150-5159
Polychlorinated biphenyls (PCBs) contamination in tropical and sub-tropical areas and the associated risks have attracted great concern. A total of 69 samples representing five distinct land types were collected to assess PCB concentrations in the Pearl River Delta (PRD), South China, including spatial distributions in soils of the area, the probable anthropogenic sources, and related potential risks. PCBs concentrations in soils of the PRD ranged from 0.3 to 202 ng?g?1. More severe PCBs contamination was presented in the western part than in the eastern part of the PRD region. The PCBs were dominated by low-chlorinated biphenyls; however, the proportion of higher-chlorinated biphenyls was elevated with the influence of industrial activities. Principal component analysis indicated that PCBs contamination in soils of the PRD region was mainly associated with 1#PCBs, while 2#PCB and e-waste emission in South China also accounted for it partly, especially to the industrial activity severely impacted areas. Toxic equivalent (TEQ) of the dioxin-like PCBs in the soils indicated that higher risk of PCB contamination was presented in the Dongjiang River Valley (55 ng?TEQ?kg?1, on average) than in the Xijiang River Valley, and were mostly contributed by the congener of PCB126. 相似文献
489.
490.