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Levels of organochlorine pesticides in natural water along the Yangtze River,from headstream to estuary,and factors determining these levels 总被引:1,自引:0,他引:1
Chen Liu Guo-Li Yuan Zhong-Fang Yang Tao Yu Xue-Qi Xia Qing-Ye Hou Long Chen 《Environmental Earth Sciences》2011,62(5):953-960
Organochlorine pesticides (OCPs), including hexachlorocyclohexane and dichlorodiphenyltrichloroethane, were monitored in 37
samples of water collected along the Yangtze River, the third longest river in the world (6,300 km). The total concentration
of OCPs (∑OCPs) in the river water ranged from 0.11 to 27.37 ng/L. It was interesting to discover that, except for some sites
near industrial cities, levels of OCPs in the water samples were very similar along the whole river. Significantly, OCPs were
detected in Tuotuo River (the origin of Yangtze River) even though OCPs have never been used in this area because of its 4,540 m
height above sea level. Furthermore, it was found that ∑OCPs was related to temperature and altitude along the river. We assume
OCPs are transported along the Yangtze River, and the factors affecting this process are discussed. 相似文献
985.
A model for evaluating the influence of water and salt on vegetation in a semi-arid desert region,northern China 总被引:1,自引:0,他引:1
Dong Hui Cheng Wen Ke Wang Xun Hong Chen Guang Cai Hou Hong Bin Yang Ying Li 《Environmental Earth Sciences》2011,64(2):337-346
A model, influence of water and salt on vegetation (IWSV), was developed to evaluate their influence on plant species. The
main function of this model was to calculate a comprehensive index value for evaluating the suitability of plant growth. This
model consists of five explanatory variables (vadose zone moisture content, vadose zone salinity, vadose zone lithology, depth
to the water table, and groundwater mineralization) and two response variables (plant species and their cover). A set of independent
data on three plant species, Artemisia ordosica, Salix psammophila, and Carex enervis, which are dominant species in the Mu Us Desert of northern China, were used to validate the model. Validation results show
an overall correct prediction for the distribution of these three species. The results demonstrated that the IWSV model can
be a useful tool for groundwater management and nature conservation in a semi-arid desert region, especially for predicting
the vegetation distribution in areas with groundwater extraction. 相似文献
986.
Supercooled water with temperatures below freezing point,was identified from hydrographic data obtained by Chinese and Australian expeditions to Prydz Bay,Antarctica,during the austral summer.The study shows that most supercooled waters occurred at depths of 63-271 m in the region north of the Amery Ice Shelf(AIS) front.The maximum supercooling was 0.16°C below the in-situ freezing point.In temperature and salinity ranges of-2.14--1.96°C and 34.39-34.46,respectively,the water was colder and fresher than peripheral shelf water.The supercooled water had less variability in the vertical profiles compared to shelf water.Based on analysis of their thermohaline features and spatial distribution,as well as the circulation pattern in Prydz Bay,we conclude that these supercooled waters originated from a cavity beneath the AIS and resulted from upwelling just outside of the AIS front.Water emerging from the ice shelf cools to an extremely low temperature(about-2.0°C) by additional cooling from the ice shelf,and becomes buoyant with the addition of melt water from the ice shelf base.When this water flows out of the ice shelf front,its upper boundary is removed,and thus it rises abruptly.Once the temperature of this water reaches below the freezing point,supercooling takes place.In summer,the seasonal pycnocline at-100 m water depth acts as a barrier to upwelling and supercooling.The upwelling of ice shelf outflow water illuminates a unique mid-depth convection of the polar ocean. 相似文献
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1 INTRODUCTION Measuring the velocity of ocean currents is one of the most important tasks in physical oceanography research. Many centuries ago, mariners had begun to obtain the sea surface cur- rents from vessel drift records. As early as in 1870s instr… 相似文献
988.
给出并解释了星际介质中轻元素D,3He,4He和Li的最新观测数据.星际介质中轻元素的丰度观测结果可以用来检验标准大爆炸核合成理论,因此对这些元素的丰度研究具有重要的天体物理意义.到目前为止,轻元素丰度的观测结果基本上支持开放宇宙的观点.根据最新的观测结果,在本地星际介质中D丰度可能存在小尺度不均匀性,而对类星体吸收云的观测表明不同观测者所获得的原初D丰度结果最大差别可达一个量级.如果观测是可靠的,那么在目前的标准大爆炸核合成理论和星系化学演化模型框架下还不能解释这种结果.另外种种迹象表明太阳系丰度可能不代表45亿年前本地星际介质的丰度. 相似文献
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Kuang Wenhui Zhang Shuwen Du Guoming Yan Changzhen Wu Shixin Li Rendong Lu Dengsheng Pan Tao Ning Jing Guo Changqing Dong Jinwei Bao Yuhai Chi Wenfeng Dou Yinyin Hou Yali Yin Zherui Chang Liping Yang Jiuchun Xie Jiali Qiu Juan Zhang Hansong Zhang Yubo Yang Shiqi Sa Rigai Liu Jiyuan 《地理学报(英文版)》2022,32(9):1705-1723
Journal of Geographical Sciences - High-resolution mapping and monitoring of national land use/cover changes contribute significantly to the knowledge of the interaction between human activities... 相似文献