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231.
Polychlorinated biphenyls (PCBs) levels in crucian carp were determined at 20 locations along four major river systems, several small-scale rivers and a wetland in Korea. Twenty-eight congeners, ranging from tri- to hepta-CBs were detected. A gas chromatograph with a mass selective detector was used to quantify the individual PCB congeners. The objectives of this study were to investigate the levels of contamination of PCBs in freshwater fish and to observe the pattern of their distribution. The sampling locations were chosen among 31 sampling sites that are currently used as environmental residue checkpoints by the Korean Ministry of Environment. Concentrations of individual congeners ranged from not detectable (n.d.) to 0.75 ng g(-1) on a wet weight basis. The total concentrations of PCBs at each site ranged from n.d. to 5.41 ng g(-1) of wet weight. The most heavily contaminated site was the Nakdong estuary located near the Shinpyung-Janglim factory district. The PCB 153 and 138 were the principal congeners and penta- and hexa-chlorinated biphenyls comprised the main congener groups. 相似文献
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特种设备作业人员具备一定的安全知识和必要的操作技能,是保障特种设备安全运行的重要因素。分析了培训、考核、发证、用人单位等环节的现状及存在问题,并对特种设备作业人员培训考核工作提出了改革建议。 相似文献
235.
磷系阻燃剂对人体的潜在毒性作用引起了国内外研究者的广泛关注。肾脏是机体重要的排毒器官,若肾脏细胞受损,可能影响肾脏功能的正常发挥。本研究以人胚肾细胞HEK293为研究对象,结合传统毒理学实验,筛选出磷酸三苯酯(TPP)及磷酸三(2-氯异丙基)酯(TCPP)诱导人胚肾细胞HEK293凋亡的关键靶标基因p53。在此基础上采用分子对接模拟和光谱法分析发现,TPP和TCPP分别以嵌插方式和沟槽方式结合p53-DNA,改变基因片段的框架结构,启动分子起始事件,通过影响相关基因(Bax、Hrk、Bcl-2和Bad)的表达量,导致线粒体途径释放cyt c,最终激活Caspase 7实现细胞凋亡。研究结果阐明了此类污染物诱导凋亡的作用机制,为毒害化学品的污染防控提供理论依据。 相似文献
236.
Zhiqiang Chen Lizhi Zhao Ye Ji Qinxue Wen Long Huang 《Frontiers of Environmental Science & Engineering》2019,13(4):54
237.
The High Plains aquifer (HPA) is the primary water source for agricultural irrigation in the US Great Plains. The water levels in many locations of the aquifer have declined steadily over the past several decades because the rate of water withdrawals exceeds recharge, which has been a serious concern to the water resources management in the region. We evaluated temporal trends and variations in agricultural water use and hydroclimatic variables including precipitation, air temperature, reference evapotranspiration, runoff, groundwater level, and terrestrial water storage across the HPA region for different periods from 1985 to 2020 at the grid, county, or region scale. The results showed that water withdrawals decreased from 21.3 km3/year in 1985 to 18.2 km3/year in 2015, while irrigated croplands increased from 71,928 km2 in 1985 to 78,464 km2 in 2015 in the entire HPA. The hydroclimatic time-series showed wetting trends in most of the northern HPA, but drying and warming trends in the southern region from 1985 to 2020. The groundwater level time-series indicated flat trends in the north, but significant declining in the central and southern HPA. Trends in irrigation water withdrawals and irrigation area across the HPA were controlled by the advancement of irrigation systems and technologies and the management of sustainable water use, but also were affected by dynamical changes in the hydroclimatic conditions. 相似文献
238.
Cao Yanmei Li Zhe Ji Wei Ma Meng 《Environmental science and pollution research international》2021,28(23):29467-29483
Environmental Science and Pollution Research - The aerodynamic noise around the high-speed railway bridge is studied by the train-bridge-flow field numerical model and theory analysis. With the... 相似文献
239.
Juan Tao Chengzhi Ding Jinnan Chen Liuyong Ding Sébastien Brosse Jani Heino Virgilio Hermoso Ruidong Wu Ziwang Wang Jiaxin Hu Rongxiao Che Xiaowei Jin Songhao Ji Dekui He 《Conservation biology》2023,37(3):e14036
The lack of high-resolution distribution maps for freshwater species across large extents fundamentally challenges biodiversity conservation worldwide. We devised a simple framework to delineate the distributions of freshwater fishes in a high-resolution drainage map based on stacked species distribution models and expert information. We applied this framework to the entire Chinese freshwater fish fauna (>1600 species) to examine high-resolution biodiversity patterns and reveal potential conflicts between freshwater biodiversity and anthropogenic disturbances. The correlations between spatial patterns of biodiversity facets (species richness, endemicity, and phylogenetic diversity) were all significant (r = 0.43–0.98, p < 0.001). Areas with high values of different biodiversity facets overlapped with anthropogenic disturbances. Existing protected areas (PAs), covering 22% of China's territory, protected 25–29% of fish habitats, 16–23% of species, and 30–31% of priority conservation areas. Moreover, 6–21% of the species were completely unprotected. These results suggest the need for extending the network of PAs to ensure the conservation of China's freshwater fishes and the goods and services they provide. Specifically, middle to low reaches of large rivers and their associated lakes from northeast to southwest China hosted the most diverse species assemblages and thus should be the target of future expansions of the network of PAs. More generally, our framework, which can be used to draw high-resolution freshwater biodiversity maps combining species occurrence data and expert knowledge on species distribution, provides an efficient way to design PAs regardless of the ecosystem, taxonomic group, or region considered. 相似文献
240.
在TSG T7001-2009《电梯监督检验和定期检验规则——曳引与强制驱动电梯》2号修改单执行后,电梯旁路装置作为电梯的重要装置,极大地方便了维保人员维护保养电梯,以及排除相关的故障.本文通过旁路装置的相关要求,结合实例,描述了旁路装置的形式、常见故障,以及检验时的注意事项. 相似文献