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561.
于2018年—2019年在鄱阳湖区周边选取4个县(区)10个村庄的典型门塘开展浮游藻类采样调查。研究共鉴定出藻类6门83种,以蓝藻门、绿藻门和硅藻门为主;浮游藻类细胞密度全年范围为7.30×104个/L~2.78×1011个/L,年均值为1.4×1010个/L,其中夏季细胞密度最大,冬季细胞密度最小;优势种主要有小环藻、微囊藻、铜绿微囊藻、卵形隐藻等,且具有较为明显的季节演替,全年优势种为小环藻;藻类多样性指数(H′)年均值为1.49,丰富度指数(M)年均值为1.92,全年水体生物学评价结果为中度污染。  相似文献   
562.
近年来,由个人护理品及废旧塑料直接或间接产生的微塑料不断地在各种环境介质中被检出,且微塑料会对生态系统产生各种危害,因此对微塑料的研究受到越来越广泛的关注。阐述了微塑料在水体、沉积物、沙滩和生物体中的赋存情况,介绍了微塑料的采集与分离方法,以及定性与定量分析方法。指出微塑料对环境及生物体产生的危害,提出现阶段研究存在的主要问题,并对今后的研究方向进行了展望。  相似文献   
563.
Prospective, community-based surveillance systems for measuring birth, death, and population movement rates may have advantages over the ‘gold-standard’ retrospective household survey in humanitarian contexts. A community-based, monthly surveillance system was established in South Kivu, Democratic Republic of the Congo, in partnership with a local implementing partner and the national ministry of health. Data were collected on the occurrence of births, deaths, arrivals, and departures over the course of one year, and a retrospective survey was conducted at the end of the period to validate the information. Discrepancies between the two approaches were resolved by a third visit to the households with discordant records. The study found that the surveillance system was superior in terms of its specificity and sensitivity in measuring crude mortality and birth rates as compared to the survey, demonstrating the method's potential to measure accurately important population-level health metrics in an insecure setting in a timely, community-acceptable manner.  相似文献   
564.
近年来化工实验室事故屡禁不止,其中人的不安全行为是导致事故发生的主要原因.为评估实验人员可靠性,进一步管控化工实验室人的不安全行为,基于标准化工厂人因可靠性分析(SPAR-H)方法,结合化工实验室人因失误的特点,确定了更加适用于化工实验室的人因可靠性分析方法.首先依据"S-O-P"认知模型对人因失误类型进行划分;然后基...  相似文献   
565.
In this paper, an attempt has been made to highlight an experimental methodology for monitoring contaminant transport through locally available silty soil and commercially available clay in geotechnical centrifuge models, for different compaction states. Use of multiple depth sensors to determine depth distribution of sodium chloride in the soil column has been detailed. The obtained results have been compared with argentometric method. To validate the centrifuge modelling, modelling of models has been used. The test setup developed can simulate contaminant transport mechanisms through the soil mass, which is approximately 10 m deep, over a period of 600 days. R e and P e are found to be N times higher in the centrifuge models. These numbers are found to be several orders less than unity. This indicates that laminar flow prevails and the dominating Cl transport mechanism in centrifuge is diffusion. The study also highlights the fact that the geotechnical centrifuge modelling can be used as a viable alternative to field scale experimentation.  相似文献   
566.
This is the first comprehensive study of sources of variation in metal concentrations within the whole tissues of a shallow burrowing, filter-feeding intertidal clam, Austrovenus stutchburyi. Samples were collected from 12 sites in April, August, November and February in 1993–1994 in the vicinity of Otago Harbour and Peninsula, New Zealand. Total tissue trace metal concentrations (μg g−1 dry weight) were measured in individual animals for the essential metals : Mn, Cu, Zn, Ni and the non-essential Cr using trace-metal clean acid-digestion and ICP-OAES techniques. Average metal concentrations were 3–60 μg g−1 for Cu, 40–118 μg g−1 for Zn, 2–12 μg g−1 for Mn, 5–35 μg g−1 for Ni and 1–44 μg g−1 for Cr. These levels decreased with body weight and differed amongst sites except for Cr in February (mid-summer). Highest concentrations occurred at sites close to a city (Dunedin) and within the central harbour region although the Cu, Zn, Ni and Cr concentrations did not correlate with the environmental gradient or season. At one coastal site, samples of both the blue mussel Mytilus galloprovincialis and cockles gave similar trends in trace metal levels. These results suggest that the cockle could be a useful trace metal biomonitor within NZ estuaries.  相似文献   
567.
This paper mainly aims to study the linear element influence on the estimation of vascular plant species diversity in five Mediterranean landscapes modeled as land cover patch mosaics. These landscapes have several core habitats and a different set of linear elements -habitat edges or ecotones, roads or railways, rivers, streams and hedgerows on farm land- whose plant composition were examined. Secondly, it aims to check plant diversity estimation in Mediterranean landscapes using parametric and non-parametric procedures, with two indices: Species richness and Shannon index.Land cover types and landscape linear elements were identified from aerial photographs. Their spatial information was processed using GIS techniques. Field plots were selected using a stratified sampling design according to relieve and tree density of each habitat type. A 50×20 m2 multi-scale sampling plot was designed for the core habitats and across the main landscape linear elements. Richness and diversity of plant species were estimated by comparing the observed field data to ICE (Incidence-based Coverage Estimator) and ACE (Abundance-based Coverage Estimator) non-parametric estimators.The species density, percentage of unique species, and alpha diversity per plot were significantly higher (p < 0.05) in linear elements than in core habitats. ICE estimate of number of species was 32% higher than of ACE estimate, which did not differ significantly from the observed values. Accumulated species richness in core habitats together with linear elements, were significantly higher than those recorded only in the core habitats in all the landscapes. Conversely, Shannon diversity index did not show significant differences.  相似文献   
568.
Urban trees serve important environmental, social and economic functions, but similar to other natural endowments they are not customarily depicted in monetary terms. The needs to augment protection, funding and community support for urban greening call for proper valuation. Heritage trees (HTs), the cream of urban-tree stock, deserve special attention. Existing assessment methods do not give justice to outstanding trees in compact cities deficient in high-caliber greenery, and to their social-cultural-historical importance. They artificially separate evaluation from valuation, which should be a natural progression from the former. Review of tree valuation methods suggested the formula approach to be more suitable than contingent valuation and hedonic pricing, and provided hints on their strengths and weaknesses. This study develops an alternative formulaic expert method (FEM) that integrates evaluation and valuation, maximizes objectivity, broadly encompasses the key tree, tree-environment and tree-human traits, and accords realistic monetary value to HTs. Six primary criteria (dimension, species, tree, condition, location, and outstanding consideration) branched into 45 secondary criteria, each allocated numerical marks. Each primary criterion was standardized to carry equal weight, and a tree's maximum aggregate score is capped at 100. A Monetary Assignment Factor (MAF) to consign dollar value to each score unit was derived from three-year average per m2 sale price of medium-sized residential flats. The applicability of FEM was tested on selected HTs in compact Hong Kong. The aggregate score of a tree multiplied by MAF yielded monetary value, which was on average 66 times higher than the result from the commonly-adopted Council of Tree and Landscape Appraisers method. The computed tree values could be publicized together with multiple tree benefits to raise understanding and awareness and rally support to protect HTs. The property-linked FEM could be flexibly applied to other cities, especially to assess HTs in compact developing cities.  相似文献   
569.
碘量法测定水中溶解氧有关问题的探讨及改进   总被引:4,自引:0,他引:4  
碘量法测定溶解氧时,采用NH3·H2O—KI代替NaOH(KOH)—KI固定溶解氧,用H2SO4—H3PO(41+1)混合酸代替H2SO4溶解沉淀,使沉淀沉降速度加快,分界线明显,沉淀溶解也更完全。同时做样品空白实验,校正了氧化还原性物质产生的干扰,对废水有明显的抗干扰能力。通过对蒸馏水、自来水、池塘水、废水进行溶解氧测定,结果均非常满意。  相似文献   
570.
抗生素是环境中普遍存在的污染物,畜牧水产养殖是其主要来源之一.环境中可能同时存在多种抗生素残留,因此单一药物的毒性评价难以反映抗生素对生态环境的影响,应探究其混合物的毒性效应.本文在总结大量文献的基础上,介绍了兽用抗生素的残留现状,总结了兽用抗生素对生态环境的混合毒性研究进展,讨论了兽用抗生素残留对土壤生物和水生生物的...  相似文献   
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