中国地幔结构及物性研究的进展

对2004——2007年中国地球物理学家在地幔内部结构和物质性质方面的研究工作进行了总结. 对地幔结构的地震波速度成像,地幔介质的各向异性,地幔间断面,地幔对流,以及地幔介质物性进行了综述,指出了各方面的主要内容,使用的主要方法和主要结果. 从这4年的研究可以发现,一些原有的研究领域工作更加深入,方法更加先进,而且进行了广泛的国际合作,合作的范围也逐渐扩大,方式多样,并出现了一些新的研究方向.      

Study on the velocity structure of the crust in Southwest Yunnan of the north-south seismic belt—Results from the Menghai-Gengma-Lushui deep seismic sounding profile

Southwest Yunnan, located in the southern segment of the north-south seismic belt, is one of the regions with strong tectonic movement and seismic activity in China. Study on the characteristics of tectonic setting and deep geophysical field in the region is an important issue in basic science. In 2013, we conducted a 600-km-long Menghai-Gengma-Lushui profile of deep seismic wide-angle reflection/refraction and high-resolution seismic refraction in Southwest Yunnan. In this paper, we use 6 groups of clear intracrustal P-wave phases picked from the seismic record sections of 11 shots to build a velocity structure model of basement and 2D crustal P-wave of the region by using finite difference inversion and ray travel time forward fitting technology. The results show that, from south to north, the crust gradually thickens along the profile and its basement shows a significant lateral heterogeneity. In the vicinity of the Nanting River fault, the basement structure shows the character of alternate depressions and uplifts, and the shallowest basement is about 1.0 km. In the vicinity of Tengchong and Lancang, the basement is about 5.0 km deep. The velocity of the middle and lower crust in the region generally increases with the increasing of depth. At the block boundary and beneath the fault tectonic belt, the velocity contours show apparent irregularity and the P-wave velocity changes sharply. In this region, the Moho gradually deepens from south to north with relatively large lateral undulations. The shallowest point of the Moho is located near Menghai at a depth of about 32.0 km. The deepest point of the Moho is located near Tengchong at a depth of about 40.5 km. Between Gengma and Yongde, the Moho shows significantly fast uplifting and depressing with an amplitude of about 4.0 km. Beneath the Nanting River fault, Longling-Ruili fault, Dayingjiang fault and Tengchong volcano, the basement velocity structure, 2D crustal P-wave velocity structure, distribution of average profile velocity and intracrustal interface spreading also show significant changes from the basement to the top of the Moho, indicating that the crustal velocity and medium physical properties beneath the fault tectonic belt are apparently different from the crustal materials on its both sides, which suggests that these faults should be in a certain scale and may extend to the lower crust or the top of the upper mantle. The earthquakes in the region mainly occurred at a depth of 10–20 km, and the seismic activity is related to the intracrustal medium velocity difference and fault belt distribution. The results can serve as the important data of the crust-mantle structure for the analysis of the deep tectonic setting, earthquake precise positioning, seismogenic structure modeling of the seismic activities in Southwest Yunnan, as well as the important reference for the evaluation of seismic hazard and the planning of earthquake disaster mitigation of this region.     

Accuracy assessment of approaches to spatially explicit reconstruction of historical cropland in Songnen Plain,Northeast China

To understand historical human-induced land use/cover change (LUCC) and its climatic effects, it is essential to reconstruct historical land use/cover changes with explicit spatial information. In this study, based on the historically documented cropland area at county level, we reconstructed the spatially explicit cropland distribution at a cell size of 1 km × 1 km for the Songnen Plain in the late Qing Dynasty (1908 AD). The reconstructions were carried out using two methods. One method (hereafter, referred to as method I) allocated the cropland to cells ordered from a high agricultural suitability index (ASI) to a low ASI, but they were all within the domain of potential cropland area. The potential cropland area was created by excluding natural woodland, swamp, water bodies, and mountains from the study area. The other method (hereafter, method II) allocated the cropland to cells in the order from high ASI to low ASI within the domain of cropland area in 1959. This method was based on the hypothesis that the cropland area domain in 1959 resulted from enlargement of the cropland area domain in 1908. We then compared these two reconstructions. We found that the cropland distributions reconstructed by the two methods exhibit a similar spatial distribution pattern. Both reconstructions show that the cropland was mostly found in the southern and eastern parts of the Songnen Plain. The two reconstructions matched each other for about 68% of the total cropland area. By spatially comparing the unmatched cropland cells of the two reconstructions with the settlements for each county, we found that unmatched cropland cells from method I are closer to settlements than those from method II. This finding suggests that reconstruction using method I may have less bias than reconstruction with method II.     

Quantitative characterization and comprehensive evaluation of regional water resources using the Three Red Lines method

Based on the synergetic development of new industrialization, rapid urbanization and agricultural modernization (IUAM), and from the viewpoint of interactive relationships between water resources and regional population, eco-environment, economy and society, the concepts of water resources intensity (WRI), water environment intensity (WEI), water resources relative efficiency (WRRE) and water environment relative efficiency (WERE) are defined with reference to energy intensity, resources efficiency and environment efficiency theory. On the basis of benchmarking theory, the quantitative characterization and evaluation method of “Three Red Lines” (the upper limit of water resources allocation, the baseline of utilization efficiency of water resources and the upper limit of sewage discharge) is proposed. According to these concepts and models, an empirical analysis of the Three Red Lines of water resources on the Chinese mainland between 2003 and 2012 was carried out. The results showed that total water consumption in eastern, central and western parts of China possesses “club convergence” characteristics, which means these areas have similar internal conditions appeared convergence in the development. Inter-provincial differences in water consumption continue to decrease, but the north–south differentiation characteristics in the eastern and central regions were still relatively obvious, while provincial differences in the eastern part were at a minimum and the central region had the largest. Water Resources Efficiency (WRE) of all four sectors in the Southwest rivers and Huaihe River basins were generally high. Industrial WRRE in the Songhua River, Yangtze River and Pearl River basins, agricultural WRRE in the Songhua River, Yellow River and northwestern river basins and domestic WRRE in the Liaohe River, Yangtze River and Pearl River basins were all low. Eco-environmental WRRE in the southeastern rivers and Yangtze River basins were low but showed an upward trend. Other river basins, except for the Northwestern rivers basin, had high eco-environmental WRRE with a downward trend. Western China, especially the northwestern part, had a low relative intensity of the water environment (WERI) and high integrated water environment management (IWEM) performance, but the relative intensities of the water resources (WRRI) were fairly high, and the comprehensive performance of integrated water resources management (IWRM) in these regions was low. In southern China, especially the southeastern part, the IWEM was fairly high, but the overall IWRM was lower.     

Toxic effects of zinc on four species of freshwater fish

The toxic effects of Zn²⁺ on Silver Carp (Hypophthalmichthyps molitrix C. et V.), Big Head Carp (Aristrichthys nobilis Richardson), Grass Carp (Ctenopharyngodon ilellus C. et V.), and Blunt Snout Bream (Megalobrama aimbly-cephala Yih) are studied. The test results are: (1) There are linear correlations between 24h LC₅₀ and 48h LC₅₀ of Zn²⁺ for Silver Carp fingerling and temperature. 24h LC₅₀, 48h LC₅₀ and 96h LC₅₀ of Zn²⁺ for fry of the four species are also determined; (2) There are logarithmic correlations between the growth rates of the fry and the concentrations of Zn²⁺ and between expansion of fish egg membranes after absorbing water and concentrations of Zn²⁺; (3) The tolerance of fry of the four species to Zn²⁺ is in the following order: Grass Carp>Silver Carp>Blunt Snout Bream>Big Head Carp; (4) The safe concentrations of Zn²⁺ are: Big Head Carp: 0.008 mg/L, Grass Carp: 0.046 mg/L, Blunt Snout Bream: 0.010 mg/L, Silver Carp: 0.012 mg/L, Silver Carp fingerling: 0.09 mg/L.     

EFFECTS OF DCMU ON CHLOROPHYLL FLUORESCENCE RATIO F685/F735 IN MARINE RED,BROWN AND GREEN ALGAE

The chorophyll fluorescence ratio F685/F735 in vivo can be a useful indicator for stress detection inhigher plants and seaweed. DCMU [3 - (3, 4 - dichlorophenyl ) - 1, 1 - dimethylurea] treatment influencesthis ratio. Th effects of DCMU on F685/F735 of marine red, brown and green algae under excitationlight of different wavelengths were investigted. In the brown algae, Laminaria japonica and Undariapinnatifida,DCMU did not increase this ratio under blue light excitation but increased the ratio slightlyunder excitation by green light. For the red algea, Halymenia sinensis, DCMU increased the ratiomarkedly under both blue and green ligh excitation. The percentage increase could reach 50% (undergreen light excitation) and was due to unequal enhancement at the two emission maxima by DCMU. Afraction of chlorophyll which contributed to fluorescence in the 735 nm region was less sensitive toDCMU and was likely from photosystem I of red algae. In the green alga, Ulva pertusa, DCMU causeda slight increase in F685     

RELATION BETWEEN WATER TEMPERATURE, WATER EXCHANGE AMOUNT, FEED AND PRAWN DISEASE

ImooUrnONTheedycarsePiddricofprawndiscaseintheprawnculturecoastalarmsofChi-naandsoutheastAsiaresultedinnoproduCtinnoutputfromrnostprawnpondsandheaVyerenoAnclosscyumbull,l994).Upt0now,devemeasimtopreventandtreatthediseasehavenotbopresental,althoughwaterenvironmentdeteriorationisconunn-lyknowntobethekcyfactorcausingthisdhase(Jiang,l994).ThispreliIninrystudyonthereati0nsbetweenprawndiseaseandfactorsthatseriouslyaffodwatetenvirDimtalquality(WaterteInPeratllre,waterexchangeamount,andarnountSa…     

北极黄河站地区不同基底中真菌的分离培养及初步鉴定

为了探索北极陆域真菌的多样性,进一步揭示其生态学角色,本研究对中国第5次北极科学考察采集自黄河站区附近的24份样品进行了真菌的分离培养及鉴定,样品涂布划线后共分离得到60株真菌,其中腐殖质样品中分离到的真菌种类和数量最多;对选取的28株代表菌株进行了真菌ITS区序列鉴定,结果表明它们分属于4个纲,12个属,分别为散囊菌纲、粪壳菌纲、座囊菌纲和微藻菌纲,其中地丝霉属为优势类群。该结果表明北极地区具有丰富的真菌物种多样性。通过对代表土壤理化性质的测定,探究了真菌多样性和土壤理化参数的相关性,其中有机碳氮及可溶性营养盐含量是影响北极土壤真菌多样性的重要指标。     

Lyase Activities of Heterologous CpcS and CpcT for Phycocyanin Holo-β-subunit from Arthrospira platensis in Escherichia coli

Arthrospira platensis is an economically important cyanobacterium; and it has been used widely in food and pharmaceutical industries. The phycocyanin(PC) from A. platensis is extremely valuable in medicine and molecular biology due to its antioxidation and anti-tumoring activity and applicability as fluorescence protein tag. In present study, two recombinant plasmids, one contained the phycocyanobilin(PCB)-producing genes(hox1 and pcyA) while the other contained the phycobiliprotein gene(cpcB) and the lyase gene(either cpcS/U or cpcT), were constructed and synchronically transferred into E. coli in order to test the the activities of relevant lyases for catalysing PCB addition to CpcB during synthesizing fluorescent PC holo-β-subunit(β-PC) of A. platensis. As was evidenced by the fluorescence emitted at a peak specific for PC, CpcB was successfully synthesized in E. coli, to which co-expressed PCBs attached though at a relatively low efficiency. The results showed that the attachment of PCBs to CpcB were carried out mainly by co-expressed CpcS/U but CpcB also showed some autocatalytic activity. Currently, no CpcT activity was detected in this E. coli expression system. Further studies will be conducted to improve the efficiency of fluorescent PC synthesis in E. coli.