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41.
Aquatic sediments often remove hydrophobic contaminants from fresh waters. The subsequent distribution and concentration of contaminants in bed sediments determines their effect on benthic organisms and the risk of re-entry into the water and/or leaching to groundwater. This study examines the transport of simazine and lindane in aquatic bed sediments with the aim of understanding the processes that determine their depth distribution. Experiments in flume channels (water flow of 10 cm s(-1)) determined the persistence of the compounds in the absence of sediment with (a) de-ionised water and (b) a solution that had been in contact with river sediment. In further experiments with river bed sediments in light and dark conditions, measurements were made of the concentration of the compounds in the overlying water and the development of bacterial/algal biofilms and bioturbation activity. At the end of the experiments, concentrations in sediments and associated pore waters were determined in sections of the sediment at 1 mm resolution down to 5 mm and then at 10 mm resolution to 50 mm depth and these distributions analysed using a sorption-diffusion-degradation model. The fine resolution in the depth profile permitted the detection of a maximum in the concentration of the compounds in the pore water near the surface, whereas concentrations in the sediment increased to a maximum at the surface itself. Experimental distribution coefficients determined from the pore water and sediment concentrations indicated a gradient with depth that was partly explained by an increase in organic matter content and specific surface area of the solids near the interface. The modelling showed that degradation of lindane within the sediment was necessary to explain the concentration profiles, with the optimum agreement between the measured and theoretical profiles obtained with differential degradation in the oxic and anoxic zones. The compounds penetrated to a depth of 40-50 mm over a period of 42 days. 相似文献
42.
通过对植物检疫、栽培园艺控制技术、生态控制技术、生物控制等技术措施综合分析,表明因地制宜协调运用各种控制措施,实施有害生物的综合治理,可最终达到经济、生态和社会效益的统一。 相似文献
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南海涛 《林业机械与木工设备》2012,(12):16-18
概述了近年来内蒙古大兴安岭林区外来有害生物的危害及分布情况,分析了该林区发展现状和面临外来有害生物入侵带来的问题和挑战,提出建立外来有害生物基因库,加强植物检疫宣传,科学调种、引种,加强公共防范意识,开展外来有害生物长效监控机制等5个方面工作来防御和治理林区外来生物入侵,为大兴安岭林区外来有害生物的预防和防治提供理论依据。 相似文献
47.
Patricio A. Díaz Beatriz Reguera Manuel Ruiz-Villarreal Yolanda Pazos Lourdes Velo-Suárez Henrick Berger Marc Sourisseau 《Marine drugs》2013,11(8):2964-2981
In 2012, there were exceptional blooms of D. acuminata in early spring in what appeared to be a mesoscale event affecting Western Iberia and the Bay of Biscay. The objective of this work was to identify common climatic patterns to explain the observed anomalies in two important aquaculture sites, the Galician Rías Baixas (NW Spain) and Arcachon Bay (SW France). Here, we examine climate variability through physical-biological couplings, Sea Surface Temperature (SST) anomalies and time of initiation of the upwelling season and its intensity over several decades. In 2012, the mesoscale features common to the two sites were positive anomalies in SST and unusual wind patterns. These led to an atypical predominance of upwelling in winter in the Galician Rías, and increased haline stratification associated with a southward advection of the Gironde plume in Arcachon Bay. Both scenarios promoted an early phytoplankton growth season and increased stability that enhanced D. acuminata growth. Therefore, a common climate anomaly caused exceptional blooms of D. acuminata in two distant regions through different triggering mechanisms. These results increase our capability to predict intense diarrhetic shellfish poisoning outbreaks in the early spring from observations in the preceding winter. 相似文献
48.
Because domoic acid, a neurotoxic secondary metabolite produced by marine diatoms in the genus Pseudo-nitzschia, is hypothesized to be part of a high affinity iron uptake system, we investigated whether domoic acid could improve the competitive ability of Pseudo-nitzschia delicatissima, and whether the availability of iron changed the outcome of competition experiments. We found that domoic acid had a slight negative effect on growth of the diatom Skeletonema marinoi when it was grown in monocultures. However, when S. marinoi was cultured with P. delicatissima the presence of domoic acid resulted in a reduction of S. marinoi cells by up to 38% and an increase in P. delicatissima cell numbers by up to 17% under iron replete conditions. Similar effects were not observed in low iron treatments. Domoic acid was not taken up by P. delicatissima cells. Overall, our results indicate that domoic acid can improve the competitive ability of Pseudo-nitzschia spp. and that iron is likely to be involved. This study provides an unusual example of indirect inhibition of competitor growth mediated by a secondary metabolite. 相似文献
49.
指出了作为生态环境的主体,在环境保护过程中,森林资源发挥着关键性的作用。然而,随着社会经济的不断发展,对森林资源的乱砍滥伐现象也变得越来越严重,这就威胁了人们的生存与发展。因此,加强林业资源的保护具有重要的现实意义。基于此,围绕营林技术进行了分析,就其对林业有害生物的控制效果进行了探究,提出了相应的对策。 相似文献
50.
松材线虫病的发生原因、危害症状及防治策略 总被引:1,自引:0,他引:1
松材线虫病能够引起大面积松树出现枯死现象,对松树林产生毁灭性伤害,属于世界性病害。为了有效促进我国林业发展,需要对松材线虫病加强防治。而目前我国在防治松材线虫病过程中难度相对较大,防治技术也比较滞后,资金不足等问题导致难以高效控制松材线虫病。基于此,深入探究松材线虫病的发生原因、危害症状,并提出了有效的防治策略。 相似文献