中国北方沙区城市风沙灾害危险度评价--基于遥感、地理信息系统和模型的研究

开展风沙灾害危险度评价研究,对促进中国北方沙区城市的安全与可持续发展具有重要意义。基于灾害系统理论,构建了城市风沙灾害系统动力学模型,对中国北方沙区城市风沙灾害危险度进行了评价。结果表明:中国北方沙区风沙灾害高危城市主要分布在新疆塔克拉玛干沙漠周边和古尔班通特沙漠南缘、甘肃省以及宁—陕—蒙3省区接壤区。重度危险以上的城市共计35个,占参评城市的51%,其中,极度危险的城市有12个,由西向东依次为乌鲁木齐、和田、中卫、乌海、包头、榆林、通辽等。近邻沙源是城市风沙灾害的主要诱因,应该加以重点治理;经济发达城市应该重点保护。减轻土壤风蚀的城市周边沙化土地利用格局优化的方法与技术应是防治城市风沙灾害的研究重点。

1990-2019年中国北方沙区太阳能资源评估

沙漠地区太阳能资源丰富且地表植被稀疏,非常适于太阳能资源开发。然而目前针对中国北方沙漠地区太阳能资源的评估仍然较少。本研究利用中国北方沙区(含沙漠、沙地、戈壁和盐碱地)46个太阳辐射站和189个常规气象站数据,基于极端梯度提升算法(xgboost)估算了太阳总辐射量,分析了总辐射量年、季和月的时空分布并进行太阳能资源评估。结果表明,中国北方沙区1990-2019年平均日照时数和太阳总辐射量为2927.90 h和5888.39 MJ·m^(-2),且以分别以22.48 h·(10a)^(-1)和8.66 MJ·m^(-2)·(10a)^(-1)的速率减少,但这种趋势并不显著(p>0.05)。日照时数和太阳总辐射量空间分布呈现出东西低中部高的特点,青海和甘肃河西的沙区总辐射量最高,在6300 MJ·m^(-2)以上,东北地区的沙地总辐射量最低,不足5300 MJ·m^(-2)。季节变化表现为夏季太阳总辐射量最大,春季次之,秋冬季最低。总体上看,青海和河西走廊西部沙区太阳能资源丰富,其他沙区较丰富,但就太阳能资源稳定度而言,仅青海、河西走廊南部沙区为较稳定,其他沙区为欠稳定或一般。因此,青海和甘肃河西沙区太阳能资源开发潜力最大,应加大对该区太阳能资源的开发投入,提高区域经济发展水平,改善沙区生态环境。

我国沙区6种蒿属植物的种子微形态特征

应用光镜和扫描电镜对我国沙区 6种蒿属植物的种子微形态结构进行了比较观察。结果表明 :其种子微形态特征在组间有一定分类学价值 ,近缘组和近缘种的种子微形态结构表现出极大的相似性 ;其种子体积小、重量轻、种皮富含胶质、表面纹饰呈凹凸不平的沟槽状 。

《中国沙漠植物志》厚壁荠属、四棱荠属、菘蓝属和独行菜属订正

通过对中国沙区厚壁荠属ＰａｃｈｙｐｔｅｒｙｇｉｕｍＢｕｎｇｅ、四棱荠属ＧｏｌｄｂａｃｈｉａＤＣ．、菘蓝属ＩｓａｔｉｓＬ．和独行菜属ＬｅｐｉｄｉｕｍＬ．植物的研究，认为《中国沙漠植物志》收录的密花厚壁荠ＰａｃｈｙｐｔｅｒｙｇｉｕｍｄｅｎｓｉｆｌｏｒｕｍＢｕｎｇｅ和多茎厚壁荠Ｐ．ｍｕｌｔｉｃａｕｌｅ（Ｋａｒ．ｅｔＫｉｒ．）Ｂｕｎｇｅ实为一种植物；短梗四棱荠Ｇｏｌｄｂａｃｈｉａｌａｅｖｉｇａｔａ（Ｍ．Ｂ．）ＤＣ．ｖａｒ．ｉｋｏｎｎｉｋｏｖｉ（Ｖａｓｓ．）ＫｕａｎｅｔＹ．Ｃ．Ｍａ应合并到正种四棱荠Ｇ．ｌａｅｖｉｇａｔａ（Ｍ．Ｂ．）ＤＣ．中；毛三肋菘蓝ＩｓａｔｉｓｃｏｓｔａｔａＣ．Ａ．Ｍｅｙｖａｒ．ｌａｓｉｏｃａｒｐａ（Ｌｅｄｅｂ．）Ｎ．Ｂｕｓｃｈ应改为毛果菘蓝Ｉ．ｔｉｎｃｔｏｒｉａＬ．ｖａｒ．Ｐｒａｅｃｏｘ（Ｋｉｔ．）Ｋｏｃｈ．；头花独行菜ＬｅｐｉｄｉｕｍｃａｐｉｔａｔｕｍＨｏｏｋ．ｆ．ｅｔＴｈｏｍｓ．中国沙区无分布。

我国北方沙区退化植被的恢复机理

通过讨论我国北方沙区退化植被的恢复机理,认为气候驱动机制、植被自我修复机制、土壤环境变化和景观格局的驱动机制是我国北方沙区退化植被自然恢复的四个主要机制。其中,气候机制决定着植被恢复演替的方向和终点,是植被恢复的外在驱动机制;植被的自我修复机制决定着植物恢复的起始速度和演替速度,是植被恢复的内在驱动机制;而景观驱动作用只发生于斑块较小且呈镶嵌分布的退化植被区,对于面积很大且连片分布的流沙裸地其作用微弱;土壤条件的改善既是植被对土壤作用的结果,又反馈于植被的演替,它决定着群落演替的阶段性和群落类型,自始自终伴随着植被的演替过程。

关于沙漠化概念的意见分歧及其成因浅析

针对当前学术界关于沙漠化概念意见分歧很大的现状,评述学者们提出的各种沙漠化概念,分析产生分歧的原因,得出:(1)沙漠化成因是沙漠化概念产生分歧的原因所在;(2)中国北方沙区沙漠化成因有自然因素,也有人为因素。在此基础上提出,沙漠化概念不应局限在成因问题上,沙漠化就是指在沙源丰富地区以风力作用形成的沙质荒漠化。

Partitioning of grain-size components of estuarine sediments and implications for sediment transport in southwestern Laizhou Bay, China

Sediment transport in estuarine systems has been of increasing interest for scientists during the past few decades. However, the mechanisms for sediment redistribution remain unclear. We characterized in detail sediment transport in the Xiaoqing River estuary using the mathematical Weibull function to partition grain-size components of surface sediments in the southwestern Laizhou Bay, Northeast China. Four partitioned components: finer than 4,4.6-12.5, 23.4-63.3, and 67.1-132.6 μm were interpreted in terms of hydrodynamic conditions. During sediment transport, silt grains were suspended and moved seaward from three depositional centers, whereas fine-grained sands moved generally landward. Overall, sediments are transported clockwise in a generally NNE direction near shore and then turn eastward offshore. The mathematical partitioning method showed a great potential for future estuarine environmental studies.

Chemical compositions and source apportionment of atmospheric PM_(10) in suburban area of Changsha, China

Source apportionment of particulate matters with aerodynamic diameter less than 10 μm （PM10） was conducted in the suburban area of Changsha, China. PM10 samples for 24 h collected with TEOM 1400a and ACCU system in July and October 2008 were chemically analyzed by the wavelength dispersive X-ray fluorescence （WD-XRF）. Source appointment was implemented by the principal component analysis/absolute principal component analysis （PCA/APCA） to identify the possible sources and to quantify the contributions of the sources to PM10. Results show that as the PM10 concentration is increased from （85.6±43.7） μg/m3 in July 2008 to （107.6±35.7） μg/m^3 in October 2008, the concentrations of the anthropogenic elements （P, S, C1, K, Mn, Ni, Cu, Zn, and Pb） are basically increased but concentrations of the natural elements （Na, Mg, Al, Si, Ca, Ti, and Fe） are essentially decreased. Six main sources of PM10 are identified in the suburban of Changsha, China： soil dust, secondary aerosols, domestic oil combustion, waste incineration, traffic emission, and industrial emission contribute 57.7%, 24.0%, 9.8%, 5.0%, 2.0%, and 1.5%, respectively. Soil dust and secondary aerosols are the two major sources of particulate air pollution in suburban area of Changsha, China, so effective measures should be taken to control these two particulate pollutants.

Geomorphological Evolution Revealed by Aeolian Sedimentary Structure in Badain Jaran Desert on Alxa Plateau, Northwest China

The Badain Jaran Desert,located in the Alxa Plateau,Northwest China,features mega-dunes and a unique dune-lake alternation landscape.This paper presented the aeolian sediment structures of three representative dunes in the Badain Jaran Desert using ground-penetrating radar (GPR).We processed and analyzed the GPR data and investigated the feasibility of using integrated GPR and sedimentological data to reconstruct dunes structure,sedimentary environment and geomorphological evolution.The results show that the internal structures of star dune and transverse dune represent various stages of mega-dune evolution: the main deposition processes of mega-dune are similar to those of transverse dunes but have a more complicated mechanism of sand transport and deposition because of the superimposition of dunes;the upper section of the mega-dune has a structure similar to that of star dune,with vertical aggradations on top.Diffraction hyperbolae in the GPR profile indicates that the presence of ancient dunes characterized by calcareous cementation layers is involved in the maintenance of mega-dunes,and water levels,shown by continuous,sub-horizontal GPR reflections,are supposed to be closely related to mega-dunes and the interdune lakes.Outcrop of wet sand and horizontal stratifications on the GPR image indicate moisture potentials with different levels inside mega-dunes.The multiplex geomorphology in the Badain Jaran Desert is the result of global climatic undulation,the unique geographical location,the geological structural features,etc.

Correlation of Dust Storms in China with Chlorophyll a Concentration in the Yellow Sea between 1997-2007

Based on daily observation data at 222 meteorological stations in China,the characteristics of dust storms between 1997 and 2007 were examined.Next,the relationship between dust events and chlorophyll (Chl) a concentration in the Yellow Sea was investigated.There were six regions with high annual frequencies of dust storms.The seasonal distribution of dust storms showed spatiotemporal variation.The six regions with highest annual frequencies also exhibited high frequencies of dust storms in spring.Dust storms in most regions occurred in spring.Of all dust storms in China,sixty-five percent of all dust storms occurred during the spring.The area and frequency of dust storms were smaller in fall and winter than in spring and summer.A significant correlation was found between dust events and Chl a concentration in the Yellow Sea.High correlation regions included Qinghai-Xizang region,part of the Hexi Corridor,the western Inner Mongolia and Hetao Regions,and the Hunshandake Desert.The high correlation may be induced by the high ratio of dust storms in the abovementioned regions that arrive over the Yellow Sea,as inferred through a forward trajectory analysis;especially notable is dust transported at a lower altitude (< 3 km).

The Jinsha River Groundwater Observation Network and Discussion about Its Earthquake Precursor Monitoring Capability

A groundwater observational network for monitoring seismic precursors has been established at the reservoirs on the lower reaches of the Jinsha River in southwestern China, where a series of hydropower stations are under construction. It is the second network in China that is operated by enterprises with the purpose to observe and study earthquake precursors in reservoir areas. This paper presents the layout and technical constitution of the network, features of its observational wells and aquifers and the preliminary result of its experimental operation. Its capability to monitor seismic precursor is evaluated based on an analysis of the well-aquifer system as well as the multiple-monthly, monthly, daily and hourly variations of water levels and water temperatures observed by this network.

Distribution of Organic Matter,Iron,Mangenese in Surface Sediments in the Nansha Islands Sea Area,South China Sea

Concentrations of organic matter, iron and manganese in the deep sea surface sediments in the Nansha Islands sea area, South China Sea are measured. Horizontal and vertical distributions of iron and manganese are discussed. The vertical distribution of iron and manganese in the sediments results from reduction, diffusion, and redeposition of manganese (or iron) oxide and hydroxide in the sediment. There are the maxima of iron and manganese in solid phase in the top of the sediment, which is caused by the penetration of O2 and the upward flux of Mn2+ ( or Fe2+ ). Manganese bacteria play a very important role in the cycle of solid-phase iron and manganese in the ocean environment. Manganese bacteria oxidize Mn2+ ( or Fe2+ ) in dissolved state to Mn4+ ( or Fe3+ ) in oxidized state under the aerobic condition, whereas they reduce iron and manganese in anaerobic conditions.

Cultivable Microfungal Communities Inhabiting Biological Soil Crusts in the Tengger Desert, China

Biological soil crusts are essential components of arid ecosystems. We examined the variations in microfungal communities inhabiting different biological crust types in the vicinity of the Shapotou Research Station in the Tengger Desert, China. A total of 134 species from 66 genera were isolated using the soil dilution plate method. The mycobiota of the crusts from the Tengger Desert, similar to that of the Negev Desert in Israel, was dominated by melanin-containing species with large multicellular spores. Abundance of these xeric species increased spatially with increasing xeric conditions from moss-dominated to cyanobacterial crusts. Density of microfungal isolates displayed the opposite trend and was positively correlated with chlorophyll content, indicating the possible significant influence of organic matter content and wetness duration on fungal biomass. Within a chronosequence of the localities of different periods after sand stabilization with revegetation, little variations were revealed in species composition and isolate density of the crust microfungal communities, while a tendency towards a decrease in the community diversity level with the crust age was noted Microfungal communities from stabilized localities differed from those of the natural localities in abundance of the dominant and some frequent species, and in the fluctuations of diversity characteristics between the cyanobacterial and moss-dominated crusts. The variations in mycobiotie parameters in the soil crusts of the Tengger Desert were apparently associated with the topographically induced variations in abiotic conditions, while the differences in microfungal community of soil crusts between the Tengger and Negev deserts, such as the significantly higher abundance of thermotolerant species in the crusts of the Tengger Deserts, were caused by the principal differences in their precipitation regimes, associated with different rainy seasons, winter and summer in the Negev and Tengger deserts, respectively.