考虑空间尺度效应的云南异龙湖流域主要入湖河流污染源解析     

袁梦祥  赵洛琪  高雨晗  黄律  马旭东  沈春节  刘嫦娥  付登高  段昌群 《湖泊科学》2024,36(3):770-781

定量解析污染源对水质影响的贡献是水环境精细化管理的重要基础。目前多通过水质和土地利用类型的关系以解析水体污染源的研究,忽略了空间尺度的差异性,引发景观配置不合理的后果。为此,本研究依据考虑空间尺度效应的污染源解析方法,基于异龙湖流域3条主要入湖河流的入湖口监测断面对雨季和旱季的水质数据进行研究。同时利用绝对主成分—多元线性回归模型(APCS-MLR)和bioenv分析揭示河道不同尺度缓冲区的土地利用变化对水质的影响并解析河流主要污染源。研究结果表明:(1)异龙湖主要入湖河流水质表现出季节性差异,旱季期间3条主要入湖河流的浊度、化学需氧量(COD_Cr)、氨氮(NH₃-N)、总磷(TP)和总氮(TN)浓度平均值相比于雨季减幅分别为39.53%、39.93%、94.48%、38.29%和1.72%。其中,入湖河流水体中的TN在旱季和雨季的超标率分别为58%和74%,成为首要污染物;(2)在旱季,20 m缓冲区尺度内河流水质受耕地和裸地占比影响较大,随着空间尺度的扩大,至50～300 m缓冲区尺度时建设用地、林地及水体占比对水质的影响增加;在雨季,C...  相似文献   

浅谈地面、探空测报内在质量与管理     

吴立群  温金翠  刘艳  段炯杰 《内蒙古气象》2009,(5):49-50

测报业务是气象预报、科研和气象服务工作的基础。地面、探空测报工作看似简单,但要真正达到高质量实为不易。工作中出错是不可避免的,但责任性事故是完全可以杜绝的。现就从管理及人才方面探讨如何提高地面、探空测报的内在质量及杜绝重大差错的发生。  相似文献   

绵阳机场低能见度气候统计特征     

段炼  王勇 《高原山地气象研究》2005,25(3)

利用绵阳机场最近10年逐时能见度资料,对低能见度的气候特征进行了统计,并对造成低能见度障碍的天气现象和影响系统作了普查分折.结果表明:绵阳机场低能见度有明显的季节变化和闩变化:造成低能见度障碍的天气现象主要是雾.  相似文献   

Palaeoceanographic change in the northeastern South China Sea during the last 15000 years     

Kuo-Yen Wei  Meng-Yang Lee  Weiwu Duan  Chaoyun Chen  Chung-Ho Wang 《第四纪科学杂志》1998,13(1):55-64

The sedimentary succession of piston core RC26-16, dated by ¹⁴C accelerator mass spectrometry, provides a nearly continuous palaeoceanographic record of the northeastern South China Sea for the last 15000 yr. Planktic foraminiferal assemblages indicate that winter sea-surface temperatures (SSTs) rose from 18°C to about 24°C from the last glacial to the Holocene. A short-lived cooling of 1°C in winter temperature centred at about 11000 ¹⁴C yr ago may reflect the Younger Dryas cooling event in this area. Summer SSTs have remained between 27°C and 29°C throughout the record. The temperature difference between summer and winter was about ca. 9°C during the last glacial, much higher than the Holocene value of ca. 5°C. During the late Holocene a short-lived cooling event occurred at about 4000 ¹⁴C yr ago. Oxygen and carbon isotopic gradients between surface (0–50 m) and subsurface (50–100 m) waters were smaller during the last glacial than those in the Holocene. The fluctuation in the isotopic gradients are caused most likely by changes in upwelling intensity. Smaller gradients indicate stronger upwelling during the glacial winter monsoon. The fauna-derived estimates of nutrient content of the surface waters indicate that the upwelling induced higher fertility and biological productivity during the glacial. The winter monsoon became weaker during the Holocene. The carbonate compensation depth and foraminiferal lysocline were shallower during the Holocene, except for a short-lived deepening at about 5000 ¹⁴C yr ago. A preservation peak of planktic foraminifera and calcium carbonate occurred between 13400 and 12000 ¹⁴C yr ago, synchronous to the global preservation event of Termination I.  相似文献   

Facies and depositional model of alluvial fan dominated by episodic flood events in arid conditions: An example from the Quaternary Poplar Fan,north-western China     

Chonglong Gao  Youliang Ji  Chenliang Wu  Jun Jin  Ying Ren  Zhao Yang  Dawei Liu  Zhijun Huan  Xiaobing Duan  Yuqi Zhou 《Sedimentology》2020,67(4):1750-1796

Alluvial fans are usually constructed through episodic flood events. Despite the significance of these ephemeral floods on the morphodynamics of alluvial fans, depositional responses to the variations in flood conditions are still poorly documented. This greatly limits the ability to interpret ancient sedimentary successions of fans and the associated flood hydrodynamics. The Quaternary Poplar Fan from endorheic Heshituoluogai Basin provides an optimal case for addressing this issue. Based on the variations in facies associations and flood conditions, three depositional stages – namely; lobe building stage, channel building stage and the abandonment stage – are identified. During the lobe building stage the Poplar Fan is predominately constructed through incised channel flood, sheetflood and unconfined streamflood, with coeval development of distal surficial ephemeral ponds. The channel building stage is characterized by the development of gravelly braided rivers. However, only scour pool fill deposits are preferentially preserved in the Poplar Fan. During the abandonment stage, erosional lags and aeolian sands randomly occur throughout the fan, while gully deposits can only be found in the distal fan. The distinctive facies architecture of the Poplar Fan is likely to be the result of periodicity of climate fluctuations between wetter and drier conditions during the Late Pleistocene to Holocene. The ephemeral floods formed under wetter conditions usually show high discharge and sediment concentrations which facilitate the lobe building processes. During the drier periods, only gravelly braided rivers can be developed through ephemeral floods as the intensity and frequency in precipitation, discharge and sediment concentrations of the flood flows significantly decrease. The abandonment stage of the fan may occur between recurring flood episodes or during the driest periods. Furthermore, the long-term (10⁵ to 10⁶ year) geomorphic evolution of the Poplar Fan shows the influence of tectonic activities. The ongoing thrust uplift tectonic activities have caused destruction of the fan but can also facilitate the fan-head trench/incision of the fan, which in turn facilitate the progradation of the fan. This study proposes a new depositional model for alluvial fans constructed through episodic flood events, which shows the character of both sheet-flood dominated and stream-flow dominated end members of alluvial fans. These findings supplement the understanding of the variability of the alluvial fans and provide means to characterize rock record of alluvial fans and their associated flood and climate conditions.  相似文献   

Early Paleozoic mantle evolution of East Kunlun Orogenic Belt in Qinghai,NW China: evidence from the geochemistry and geochronology of the Late Ordovician to Late Silurian mafic-ultramafic rocks in the Qimantag region     

Xue-Peng Duan  Li-Hui Jia 《International Geology Review》2020,62(15):1883-1903

ABSTRACT

Subduction-related basaltic rocks in active continental margins should record information about the lithospheric mantle. Mafic rocks from the Qimantag region of the East Kunlun Orogenic Belt (EKOB), NW China, can be used to constrain the evolution of mantle sources. The Heishan basalts (445 Ma) and Xiarihamu gabbros (427 Ma) display distinct geochemical and isotopic features, with basalts yielding relatively lower Na₂O+K₂O (1.48–4.16 wt.%) and Mg^# (0.50–0.57) than gabbros (Na₂O+K₂O = 2.96–4.07 wt.%, Mg^# = 0.65–0.81). Although the basalts and gabbros show similar enrichment of LILE and depletion of HFSE, the gabbros have higher Th/Y and lower Sm/Th and Nb/U ratios than the basalts, indicative of derivation from a more enriched mantle source. The Heishan basalts have relatively positive εNd(t) values (+4.7 to +5.8) whereas the Xiarihamu gabbros have negative εNd(t) values ranging from ?5.5 to ?3.8. Crustal contamination played an insignificant role in the formation of the basalts and gabbros. Our data suggest that the basalts originated from a depleted mantle source, slightly enriched by subduction-related fluids, whereas the gabbros originated from an enriched mantle source. These findings support a subduction-related progressive lithospheric mantle enrichment model over ~20 Ma beneath the Qimantag region in the Early Palaeozoic.  相似文献   

Assessment of aeolian desertification trends from 1975's to 2005's in the watershed of the Longyangxia Reservoir in the upper reaches of China's Yellow River     

C.Z. Yan  X. Song  Y.M. Zhou  H.C. Duan  S. Li 《Geomorphology》2009,112(3-4):205-211

Global climate change will affect the ecology and environment of the Qinghai–Tibet Plateau, thus increasing attention is being paid to the aeolian desertification that is occurring in the watershed that supplies the Longyangxia Reservoir in the upper reaches of China's Yellow River. We must assess the aeolian desertification trends before developing a plan to restore the region's degraded eco-environment. In this study, land suffered from aeolian desertification was classified into four levels (slight, moderate, severe, and extremely severe) using a series of indices. Interpretation of Landsat MSS and TM data from 1975's, 1989's, and 2005's was used to establish databases of aeolian desertified land at these three times. We then derived the aeolian desertification trends during the study period by overlaying the consecutive databases, and we analyzed the driving factors responsible for the observed aeolian desertification. The results show a total of 1,721,478.02 ha of aeolian desertified land in 2005's, accounting for 13% of the region's total area. From 1975's to 1989's, the area of aeolian desertified land increased by 229,307.26 ha, which represents a 15% increase compared to the 1975's area; and from 1989's to 2005's, the area of aeolian desertified land decreased by 19,079.87 ha, which represents a 1% decrease compared to the 1989's area. The main driving factors responsible for this increased aeolian desertification were climate factors (high wind velocity and an increase in annual temperature, combined with low precipitation and high evaporation) as well as unsustainable human activities and inappropriate policy measures. A series of key national projects initiated to combat degradation of the study area's eco-environment led to a decrease of aeolian desertified land through obvious restoration of vegetation.  相似文献   

中国基本公共服务效率与城镇化质量的时空耦合关系研究   总被引：1，自引：1，他引：0  

尹鹏  王富喜  段佩利 《地理科学》2021,41(4):571-579

以2007-2017年中国31个省区(未含港澳台地区)为研究对象,在厘清基本公共服务效率与城镇化质量耦合机理基础上,构建基本公共服务效率与城镇化质量评价指标体系,运用数据包络分析模型和熵值法测算基本公共服务效率与城镇化质量水平,运用耦合协调度模型和障碍度模型,分析两者耦合协调的时空特征及其主要障碍因子.结果表明:①中国...  相似文献   

云南盐津2006地震群的强震动应急观测研究     

周挚  李世成  崔建文  高东  包一峰  毛燕  段建新  张潜 《国际地震动态》2008,(11)

2006年7月22日09时10分21.6秒,云南省昭通市盐津县境内(28°01′N,104°08′E)发生Ms5.1地震,震源深度9km.极震区烈度为Ⅵ度,个别Ⅶ破坏点,等震线形状呈椭圆形,长轴走向北东向.地震造成22人死亡,13人重伤,35428户、151168人受灾.2006年8月25日13时51分41.1秒,盐津县(28°03′N,104°07′E)再次发生5.1级地震,震源深度7km,较7月22日地震略浅.微观震中由722地震位置向西北偏移约4km.由于震中位置基本相同,故地震灾害相互叠加,出现灾害加重现象和灾情范围扩大趋势,地震造成2人死亡,重伤7人,1万多户、4.5万多人需要紧急转移安置,房屋倒塌1500多间,其中170所学校的校舍不同程度受损.  相似文献   

Analysis of elastoplasticity and rheology due to mining subsidence     

Xiong Wu  XiaoGang Wang  QingWei Duan  ZhiXin Jia  NengXiong Xu  YanDong Sun 《中国科学D辑(英文版)》2008,51(6):826-836

At present, as the easily mining resources are being increasingly depleted, the exploitation of coal under buildings, water-bodies and railways is imminent for the sustainable production. Probability in-tegral method is a general method for mining subsidence in the coal system. Because of poor under-standing of mining subsidence for other sections, the authors suggest probability integral method for the study of coal mining under buildings, water-bodies and railways. Moreover, the calculation result of probability integral method should be corrected by numerical simulation method. Based on practical projects, the impact has been evaluated on the security of Xifeihe left embankment under coal mining. Combining with the results of probability integral method, we propose that the 600 m far from em-bankment is a good rationality. This article provides the basis for the rational exploitation of coal re-source which is a major practical problem under the premise of Water Infrastructure Security. Fur-thermore, it also can be served as a reference for the similar projects, such as mining Xiaolangdi res-ervoir area, mining Yuecheng reservoir and mining the major channels of Middle Route South to North Water Transfer.  相似文献