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831.
832.
橡胶种植对纳板河流域热带雨林生态系统的影响 总被引:1,自引:0,他引:1
通过实地调查数据对云南纵向岭谷区纳板河自然保护区热带雨林生态系统(包括不同海拔高度的3个样地),不同种植年限的人工橡胶林(分别为种植8 a、种植20 a和种植30 a的3个样地)及1个次生林样地,植被和土壤的比较研究,定量分析了橡胶种植对热带雨林生态系统的影响.研究结果表明,①热带雨林随海拔高度的下降,生物量和土壤养分含量均呈增加趋势;中海拔热带雨林物种丰富度最高,群落层次丰富.②热带雨林开采为橡胶林之后,群落层次结构简单化,物种多样性明显下降,地上生物量下降,土壤养分状况变劣,次生林介于二者之间.研究结果可以为该地区土地的持续利用与生物多样性保护提供依据. 相似文献
833.
上覆水中磷被结合到底泥中时,不同形态磷的数量将会改变, 由此导致磷的释放能力和生物有效性被显著改变.以富营养化河道上覆水和底泥为材料,考察了静态条件下,底泥中不同形态磷的变化规律及其对磷的生物有效性的影响.结果表明, 潜在活性磷(PMP)含量显著增加,NH4Cl-P、BD-P、NaOH-nrP分别增加了297.68%、1O.73%、30.49%.难释放态磷则基本保持不变.潜在活性磷对生物有效磷的形成具有显著的影响,4种生物有效磷中的3种(WSP、Olsen-P、AAP)均与其在a<0.01水平上显著正相关,并且其对AAP形成的影响最为显著.因此推测,静态条件下,当上覆水中磷向底泥迁移时,首先会形成潜在活性磷和生物有效磷. 相似文献
834.
Phosphates for Pb immobilization in soils: a review 总被引:9,自引:0,他引:9
In its soluble ionic forms, lead (Pb) is a toxic element occurring in waters and soils mainly as the result of human activities.
The bioavailability of lead ions can be decreased by complexation with various materials in order to decrease their toxicity.
Pb chemical immobilization using phosphate addition is a widely accepted technique to immobilize Pb from aqueous solution
and contaminated soils. The application of different P amendments cause Pb in soils to shift from forms with high availability
to the most strongly bound Pb fractions. The increase of Pb in the residual or insoluble fraction results from formation of
pyromorphite Pb5(PO4)3X where X = F, Cl, Br, OH, the most stable environmental Pb compounds under a wide range of pH and Eh natural conditions.
Accidental pyromorphite ingestion does not yield bioavailable lead, because pyromorphite is insoluble in the intestinal tract.
Numerous natural and synthetic phosphates materials have been used to immobilize Pb: apatite and hydroxyapatite, biological
apatite, rock phosphate, soluble phosphate fertilizers such as monoammonium phosphate, diammonium phosphate, phosphoric acid,
biosolids rich in P, phosphatic clay and mixtures. The identification of pyromorphite in phosphate amended soils has been
carried out by different non destructive techniques such as X-ray diffraction, scanning electron microscopy coupled with energy
dispersive X-ray spectroscopy, X-ray absorption fine structure, transmission electron microscopy and electron microprobe analysis.
The effectiveness of in situ Pb immobilization has also been evaluated by selective sequential extraction, by the toxicity
leaching procedure and by a physiologically based extraction procedure simulating metal ingestion and gastrointestinal bioavailability
to humans. Efficient Pb immobilization using P amendments requires increasing the solubility of the phosphate phase and of
the Pb species phase by inducing acid conditions. Although phosphorus addition seems to be highly effective, excess P in soil
and its potential effect on eutrophication of surface water, and the possibility of As enhanced leaching remains a concern.
The use of mixed treatments may be a useful strategy to improve their effectiveness in reducing lead phyto- and bioavailability. 相似文献
835.
836.
Louis Hautier Jean-Claude Grégoire Jérôme de Schauwers Gilles San Martin Pierre Callier Jean-Pierre Jansen Jean-Christophe de Biseau 《Chemoecology》2008,18(3):191-196
Summary. Under laboratory conditions, the multicolored Asian lady beetle, Harmonia axyridis is well known as an intraguild predator of other ladybirds. However the real impact of this exotic species on native species
was poorly investigated in the field. Because many ladybird species produce alkaloids as defensive compounds, we propose here
a new method of intraguild predation monitoring in coccinellids based on alkaloid quantification by GC-MS. In laboratory experiments,
adaline was unambiguously detected in fourth instar larvae of H. axyridis having ingested one egg or one first instar larva of Adalia bipunctata. Although prey alkaloids in the predator decreased with time, traces were still detected in pupae, exuviae and imagines of
H. axyridis having ingested one prey when they were fourth instar larvae. Analysis of H. axyridis larvae collected in two potato fields shows for the first time in Europe the presence of exogenous alkaloids in 9 out of
28 individuals tested. This new method of intraguild predation detection could be used more widely to follow the interactions
between predators and potential chemically defended insect preys. 相似文献
837.
838.
Erik Jeppesen Martin Appelt Kirsten Hastrup Bjarne Grønnow Anders Mosbech John P. Smol Thomas A. Davidson 《Ambio》2018,47(2):296-309
Based on lake sediment data, archaeological findings, and historical records, we describe rapid transformations, resilience and resistance in societies and ecosystems, and their interactions in the past in the North Water area related to changes in climate and historical events. Examples are the formation of the polynya itself and the early arrival of people, ca. 4500 years ago, and later major human immigrations (different societies, cultural encounters, or abandonment) from other regions in the Arctic. While the early immigrations had relatively modest and localised effect on the ecosystem, the later-incoming culture in the early thirteenth century was marked by extensive migrations into and out of the area and abrupt shifts in hunting technologies. This has had long-lasting consequences for the local lake ecosystems. Large natural transformations in the ecosystems have also occurred over relatively short time periods related to changes in the polynya. Finally, we discuss the future perspectives for the North Water area given the many threats, but also opportunities. 相似文献
839.
GuanNan Xiong YunHui Zhang YongHong Duan ChuanYang Cai Xin Wang JingYa Li Shu Tao WenXin Liu 《Environmental science and pollution research international》2017,24(23):18953-18965
Samples of ambient air (including gaseous and particulate phases), dust fall, surface soil, rhizosphere soil, core (edible part), outer leaf, and root of cabbage from eight vegetable plots near a large coking manufacturer were collected during the harvest period. Concentrations, compositions, and distributions of parent PAHs in different samples were determined. Our results indicated that most of the parent PAHs in air occurred in the gaseous phase, dominated by low molecular weight (LMW) species with two to three rings. Specific isomeric ratios and principal component analysis were employed to preliminarily identify the local sources of parent PAHs emitted. The main emission sources of parent PAHs could be apportioned as a mixture of coal combustion, coking production, and traffic tailing gas. PAH components with two to four rings were prevailing in dust fall, surface soil, and rhizosphere soil. Concentrations of PAHs in surface soil exhibited a significant positive correlation with topsoil TOC fractions. Compositional profiles in outer leaf and core of cabbage, dominated by LMW species, were similar to those in the local air. Overall, the order of parent PAH concentration in cabbage was outer leaf > root > core. Partial correlation analysis and multivariate linear stepwise regression revealed that PAH concentrations in cabbage core were closely associated with PAHs present both in root and in outer leaf, namely, affected by adsorption, then absorption, and translocation of PAHs from rhizosphere soil and ambient air, respectively. 相似文献
840.