Comparison of Chemical Toxicity to Different Algal Species Based on Interspecies Correlation,Species Sensitivity,and Excess Toxicity          下载免费PDF全文

Xiao H. Wang  Yang Yu  Ling Fu  Hong W. Tai  Wei C. Qin  Li M. Su  Yuan H. Zhao 《洁净——土壤、空气、水》2016,44(7):803-808

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Shear-wave splitting in the crust: Regional compressive stress from polarizations of fast shear-waves          下载免费PDF全文

Yuan Gao  Yutao Shi  Jing Wu  Lingxue Tai 《地震科学（英文版）》2012,25(1):35-45

When propagating through anisotropic rocks in the crust, shear-waves split into faster and slower components with almost orthogonal polarizations. For nearly vertical propagation the polarization of fast shearwave (PFS) is parallel to both the strike of the cracks and the direction of maximum horizontal stress, therefore it is possible to use PFS to study stress in the crust. This study discusses several examples in which PFS is applied to deduce the compressive stress in North China, Longmenshan fault zone of east edge of Tibetan plateau and Yunnan zone of southeast edge of Tibetan plateau, also discusses temporal variations of PFS orientations of 1999 Xiuyan earthquake sequences of northeastern China. The results are consistent to those of other independent traditional stress measurements. There is a bridge between crustal PFS and the crustal principal compressive stress although there are many unclear disturbance sources. This study suggests the PFS results could be used to deduce regional and in situ principal compressive stress in the crust only if there are enough seismic stations and enough data. At least, PFS is a useful choice in the zone where there are a large number of dense seismic stations.  相似文献   

近50 a博斯腾湖逐年水量收支估算与水平衡分析   总被引：2，自引：0，他引：2       下载免费PDF全文

刘丽梅  赵景峰  张建平  彭文甫  范敬龙  张太西 《干旱区地理》2013,36(1):33-40

据博斯腾湖流域1958-2010年期间主要河流开都河、黄水沟、清水河、孔雀河的逐年流量资料,结合焉耆盆地降水、蒸发要素的同期观测资料,对大湖区的逐年水量收支进行计算,并依据水量平衡原理对博湖大湖区残差水量进行了逐年分析。结果表明：（1）1958-2010年期间年均入湖水量14.34×10⁸ m³/a,其中入湖河水约占95%;年均输出水量13.96×10⁸ m³/a,其中大湖区输入孔雀河水量约占43%,湖面蒸发耗水量占57%;湖区年均蓄水量71.57±3.92×10⁸ m³10⁸ m³/a,湖水年均水位为1 047.01±0.94 m;（2）极端水文年度水量平衡分析指出：1986年为最枯年份,入湖河水是多年平均值的62%,而出湖河水量是多年平均值的153%,导致年内湖区水位下降0.94 m;2002年最丰年份入湖河水是多年平均值的2.6倍,致使年内水位上升0.80 m;（3）残差水量逐年“正负”变化指出,湖水与地下水之间存在互补关系,过去53 a间湖水补给地下水的年均水量为0.87×10⁸ m³/a。  相似文献   

石羊河下游沙漠化的自然因素和人为因素及其位移   总被引：32，自引：5，他引：27  

常兆丰  韩福贵  仲生年  赵明  梁泰 《干旱区地理》2005,28(2):150-155

石羊河流域下游自汉代以来逐渐沙漠化,生态环境退化。其自然因素主要有：地形特征构筑了封闭的内陆河流域;水蚀是内陆河流域沙漠化的开始,上游集流区为中、下游提供了丰富的沙源;水资源的减少使得中、下游大面积湖积沙沙漠化。人为因素主要有：农业开发是引起水资源减少的关键,巩固边塞是引起河西走廊农业开发和耕地面积扩大的主要原因;战争对石羊河流域生态退化的影响不可忽视。石羊河下游民勤县在自汉代以来沙漠化和生态环境退化的漫长历史过程中,人为因素不断增强。20世纪中期以来,尤其是1958年红崖山水库建成以来,沙漠化过程中的人为因素占据了主导地位。  相似文献   

Tracing carbon transfer and assimilation by invertebrates and fish across a tropical mangrove ecosystem using stable isotopes          下载免费PDF全文

Nguyen Tai Tue  Tran Dang Quy  Mai Trong Nhuan  Luu Viet Dung  Nguyen Dinh Thai 《Marine Ecology》2017,38(5)

Mangroves are highly productive ecosystems that exhibit a diverse range of habitats, including tidal creeks and flats, forest gaps and interior forest with varying understory light intensity, tidal dynamics, geomorphological settings, and overall biological production. Within mangrove ecosystems, invertebrates and fish feed on heterogeneous food sources, the occurrence of which is unevenly distributed across the system. This provides a basis for testing models of carbon transfer across mangrove ecosystems. We hypothesized that the carbon transfer and assimilation by fish and invertebrates will vary across the different mangrove habitats and that such variations can be predicted by their stable isotope compositions. We analysed δ¹³C and δ¹⁵N signatures of consumers and their potential organic carbon sources across a tropical mangrove ecosystem in Vietnam. The δ¹³C values of crabs and snails significantly decreased from the tidal flat to interior forest, indicating that variations in carbon transfer and assimilation occurred at small scales <30 m. Reduced variation in δ¹³C of suspension‐feeding bivalves suggested that tidal water was a vector for large‐scale transport of carbon across the mangrove ecosystem. An analysis of co‐variance using habitat as a fixed factor and feeding habit and movement capacity of consumers as co‐variates indicated that habitat and feeding types were major features that affected the δ¹³C values of invertebrates and fish. The findings demonstrate that carbon transfer and assimilation across mangrove ecosystems occur as a diverse combination of small (<30 m) and large (>30 m) scale processes.  相似文献   

Dual-polarized ratio algorithm for retrieving Arctic sea ice concentration from passive microwave brightness temperature   总被引：1，自引：0，他引：1  

Shugang Zhang  Jinping Zhao  Karen Frey  Jie Su 《Journal of Oceanography》2013,69(2):215-227

We present a new algorithm for retrieving sea ice concentration from the AMSR-E data, the dual-polarized ratio (DPR) algorithm. The DPR algorithm is developed using vertically and horizontally polarized brightness temperatures at the same channel of 36.5 GHz. It depends on the ratio of dual-polarized emissivity, α, which is determined empirically at about 0.92 by remotely sensed brightness temperature in winter and used for the other seasons as well. The ice concentration retrieved by the DPR is compared with those by the NT2 and ABA algorithms. Since the main difference among these algorithms takes place in marginal ice zones, 17 marginal ice zones are chosen. The retrieved ice concentrations in these zones are examined by the ice concentration obtained by the MODIS data. The mean error, root-mean-square error and mean absolute error of the DPR algorithm are relatively better than those from the other two algorithms. The results of this study illustrate that the DPR algorithm is a more accurate algorithm for retrieving sea ice concentration from the AMSR-E brightness temperature, and can be used for operational purposes.  相似文献   

Quantitative characteristics of microorganisms in permafrost at different depths and their relation to soil physicochemical properties     

Wei Zhang  XiaoPei Dong  GuangXiu Liu  GaoSen Zhang  XiuKun Wu  XiSheng Tai  HaoZhi Long  BaoGui Zhang 《寒旱区科学》2012,4(2):0127-0131

Microorganisms in permafrost can live in cold environments due to coadapted physicochemical processes in this environment. In this paper, the relation between microbial number and soil physicochemical properties at the headwaters area of the Urumqi River is analyzed by using fluorescence microscopy counting and oligo-culture techniques. In total, 20 samples from a 200-cm permafrost core were used as study materials. The study reveals that the number of culturable bacteria has a significantly positive correlation with soil water content, total carbon and total nitrogen concentrations, and a significantly negative correlation with soil pH value. In addition, the ratio of culturable bacteria to total cell number decreases with depths. The results demonstrate that the number of culturable bacteria in permafrost is closely correlated with soil physicochemical properties and depositional age.  相似文献   

Livelihood differentiation between two villages in Yesanpo Tourism District in China   总被引：1，自引：0，他引：1  

Tai Huang  Jian-chao Xi  Quan-sheng Ge 《山地科学学报》2017,14(11):2359-2372

The rapidly developing rural tourism industry in China has deeply influenced the livelihoods of rural households. This study compares the impact of rural tourism development in poor areas on the farmers’ livelihoods, based on the Sustainable Livelihoods Framework proposed by the United Kingdom’s Department for International Development. Gougezhuang, a tourist village, and Jiaojiekou, a non-tourist village, both located in Yesanpo Tourism District in the state-level povertystricken Laishui County, Hebei Province, were selected as case studies. The livelihood models of the two villages show great differentiation after 20 years of tourism development. Gougezhuang Village has been driven by the tourism industry and farmers are employed locally, enjoying a relatively higher-income life, with a developmental livelihood model. In contrast, farmers in Jiaojiekou Village earn their living mainly by leaving home to work in the city. They have a low income, with a survival livelihood model, supported by part-time business. Considering that the two villages are adjacent and have similar development backgrounds, the analysis results indicate that rural tourism has an apparent locationspecific effect on poverty alleviation and socioeconomic development, but the development of rural tourism is limited regarding large-scale poverty alleviation efforts in poor areas. To implement a propoor- tourism strategy and achieve sustainable development, it is necessary to implement comprehensive management measures to change the local conditions of rural settlements and make full use of the spillover effect of tourist consumption.  相似文献   

川东北分水岭构造须家河组钻井提速技术研究与应用          下载免费PDF全文

甘心  侯树刚  赵俊峰  侯立云  张琳琳 《探矿工程》2019,46(2):17-22

针对川东北分水岭构造须家河组地层段机械钻速慢的钻井难题,开展了提速技术研究。首先通过工程地质特征分析,获取了须家河组地层矿物组分含量和岩石力学参数,并有针对性地提出提速技术思路和提速手段。从分3井现场应用效果看,气体钻井技术、螺杆钻具+混合钻头以及扭冲工具+混合钻头钻井技术均取得不同程度的提速效果,其中气体钻井技术平均机械钻速最高,达到4.78 m/h,与同井采用常规泥浆钻井相比提高4.49倍。  相似文献   

赣东北地区重要火成岩的40Ar／39Ar年龄   总被引：11，自引：0，他引：11  

赵崇贺 《地球科学》1997,22(3):257-260

在赣东北蛇绿混杂岩带发现含晚古生代放射虫硅夺，测定了该带内的和带外几个关键地点的火山岩和辉长岩的＾４０Ａｒ／＾３０Ａｒ同位素地南年龄，获得了以下结果：火山岩的坪年龄为４３４．９－４８６．７Ｍａ，辉长岩的坪年龄为２３２．５－２６６．３Ｍａ，因此可以肯定赣东北地区有早生代晚期的火山活动，证实了上述火成冉不是中、新元古代的产物，它们中的一部分与晚古生代硅质岩都是蛇绿岩套的成员，属该区晚古生代洋壳的组成部  相似文献