U-Th-Pb behavior of zircons under high-grade metamorphic conditions:A case study of zircon dating of meta-diorite near Qixia,eastern Shandong

This paper carried out a study on U--Th--Pb behavior of zircons in a ＂dry＂ rock system during high-grade metamorphism in the Archean basement of eastern Sbandong. The studied sample has a mineral assemblage of plagioclase ＋ K-feldspar ＋ clinopyroxene ＋ biotite ＋ quartz and its pro- tolith is considered to be diorite. The zircons are stubby, equant or irregular in shape and show fir-leaf, sectorial, banded or oscillatory zoning. They contain inclusions, including mineral assemblages of clinopyroxene ＋ orthopyroxene ＋ hornblende ＋ quartz and plagioclase ＋ K-feldspar ＋ biotite ＋ quartz. Fifty SHRIMP analyses were performed on 34 zircon grains, which commonly yielded high Th/U ratios （mostly 〉0.5）. Most analyses are distributed along concordia from 2.54 to 2.25 Ga, with the youngest age being - 1.95 Ga. Compositions and ages show large variations even in a same zircon grain. Combined with early studies, conclusions can be drawn as follows： 1） the diorite underwent two episodes of high-grade metamorphism, at the end of the Neoarchean and the Paleoproterozoic （-2.50 Ga and 1.95 Ga or slightly later）; 2） high-grade metamorphism in a ＂dry＂ rock system may partially reset the U--Th--Pb system of zircons and, in this case, the ages between the oldest and youngest are chronologically meaningless; and 3） high Th/U ratios may be common features of zircons formed during high-grade metamorphic conditions.

Adaptation models of mountain glacier tourism to climate change: a case study of Mt. Yulong Snow scenic area

Mountain glaciers have an obvious location advantage and tourist market condition over polar and high latitude glaciers. Due to the enormous economic benefit and heritage value, some mountain glaciers will always receive higher attention from commercial media, government departments and mountain tourists in China and abroad. At present, more than 100 glaciers have been devel- oped successfully as famous tourist destinations all over the world. However, global climate change seriously affects mountain glaciers and its surrounding environment. According to the current accelerated retreat trend, natural and cultural landscapes of some glaciers will be weakened, even disappear in the future. Climate change will also inevitably affect mountain ecosystems, and tourism routes under ice and glacier experience activities in these ecosystems. Simultaneously, the disappearance of mountain glaciers will also lead to a clear reduction of tourism and local economic benefits. Based on these reasons, this paper took Mr. Yulong Snow scenic area as an example and analyzed the retreat trend of a typical glacier. We then put forward some scientific and rational response mechanisms and adaptation models based on climate change in order to help future sustainable development of mountain glacier tourism.

Risk prevention and control strategies for the severely affected areas of snow disaster in the Three Rivers Source Region(TRSR), China

Historically,frequent and heavy snow disaster(SD)has caused serious livestock death and casualties,resulting in a devastating impact on animal husbandry development in the Three Rivers Source Region(TRSR).From winter in 2018 to spring in 2019,the largest SD occurred in this area over the past 10 years,especially in core zones of the Lancang River Source Region.Field research results show that the main causes of the major SD include weak infrastructure(i.e.,roads,communications,warm sheds,and insufficient forage reserve),low rate of domestic animals for sale before the SD,and low loss settlement rate.SD occurrence could furtherly reduce the ability of disaster prevention,mitigation and relief of disaster loss.In the future,heavily affected SD areas should improve the forecasting ability of snowfall incidents,strengthen infrastructure construction,implement grass and livestock balance strategies,optimize livestock structure,improve loss settlement rate,and develop a modern compound model of animal husbandry development model that combines breeding,slaughtering and deep processing of animal product.

Frontier Grassland Degradation and Its Countermeasures

Firstly, the status quo of Hulunbuir Grassland degradation was introduced, and then the main reasons for the degradation were discussed, such as overgrazing, excessively mining mineral resources and so forth. Finally some targeted countermeasures, like improving grassland legislation and policy as well as grassland ecological compensation system, actively implementing ecological animal husbandry and reasonably exploiting mineral resources, were put forward to restore the ecological environment of Hulunbuir Grassland.

Characteristics of total suspended particulates in the atmosphere of Yulong Snow Mountain,southwestern China

The measurement of black carbon （BC） and organic carbon （OC）, dust in total suspended particulates （TSP） was carried out at Yulong Snow Mountain （Mt. Yulong） and Ganhaizi Basin, in the Mt. Yulong region, southwestern China. TSP samples were analyzed using a thermal/optical reflectance carbon analyzer. Results show that average BC and OC concentrations in TSP in the Mt. Yulong region were 1.61±1.15 μg/m3 and 2.96±1.59 μg/m3, respectively. Statistical results demonstrated that there were significant differences in mean BC and OC contents between Ganhaizi Basin and Mt. Yulong at the 0.05 level. Strong correlations between BC and OC indicate their common dominant emission sources and transport processes. Temporal variations ofBC, OC, and optical attenuation （ATN） values were consistent with each other in carbonaceous aerosols. The ratios of OC/BC in monsoon season were significantly higher than in non-monsoon in aerosols from Ganhaizi, which is closely related to the formation of secondary organic carbon （SOC） and extensive motor vehicle emissions from tourism activities. The temporal variations of BC, OC and ATN in carbonaceous aerosols in Ganhaizi and Mt. Yulong were totally different, probably due to elevation difference and diverse tourism activity intensity between the two sites. Time-averaged aerosol optical depth （AOD） at the wavelength of 550 nm in Mt. Yulong was higher than that of the inland of the Tibetan Plateau （TP）. Source apportionment indicated that intensive exhaust emissions from tourism vehicles were the main local sources of atmospheric pollutant in the Mt. Yulong region. Biomass-burning emissions released from South Asia could penetrate into the inland of the TP under the transport of summer monsoon. Further study is needed to assess light absorption and radiative forcing of carbonaceous aerosols, and modeling research in combination with long-term in-situ observations of light-absorbing particulates （LAPs） in the TP is also urgently needed in future work.

The SARS-CoV-2 main protease induces neurotoxic TDP-43 cleavage and aggregates

Dear Editor,Neurologic manifestations associated with many COVID-19 patients,including acute infection with severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)and long COVID,have been proven by increasing evidence.1 To date,most studies have focused on how SARS-CoV-2 invades the nervous system and the consequent neuropathological changes.2,3 In contrast,the specific mechanism by which SARS-CoV-2 infection leads to neurological disease remains unclear.

全球冰冻圈灾害高风险区:影响与态势

20世纪70年代以来,全球增温显著,冰冻圈快速变化事件发生频率在增加,由此引发和即将引发的冰冻圈灾害危害巨大.冰冻圈不同灾种成灾机理、承灾体及其孕灾环境各异,灾害分布具有明显的空间分异特征.基于已有研究成果,较系统地阐述了冰冻圈灾害成灾机理,梳理了冰冻圈灾害类型、时间尺度、空间分异及其类型区划.在此基础上,揭示了全球冰冻圈灾害高风险区的综合影响及其态势.冰冻圈变化-冰冻圈灾害风险-冰冻圈风险管控链条关系紧密,亟需加强冰冻圈变化对社会经济系统的综合风险分析、评估和理解,以期针对性地调整未来冰冻圈灾害高风险区经济社会活动轨迹,有差别地制定冰冻圈灾害高风险区防灾减灾规划,以降低冰冻圈灾害风险和提高可持续发展能力.

Glacial Lake Outburst Flood Disasters and Integrated Risk Management in China

High-risk areas for glacial lake outburst flood(GLOF) disasters in China are mainly concentrated in the middle-eastern Himalayas and Nyainqe?ntanglha(Nyenchen Tanglha Mountains), Tibetan Plateau. In the past 20 years, glaciers in these regions have retreated and thinned rapidly as a response to regional climate warming,leading to the formation of new glacial lakes and the expansion of existing glacial lakes. These areas are located in the border belt between the Indian and the Eurasian plates, where tectonic seismic activity is also frequent and intense. Earthquakes have often compromised the stability of mountain slopes, glaciers, and moraine dams, resulting in an imbalance in the state of glacial lakes and an increase of loose materials in valleys. It is foreseeable that the possibility of GLOFs and disaster occurrence will be great in the context of frequent earthquakes and continued climate warming. This article presents the temporal and spatial characteristics of GLOF disasters, as well as the conditions and mechanisms of GLOF disaster formation,and proposes an integrated risk management strategy to cope with GLOF disasters. It aims to facilitate the mitigation of the impacts of GLOF disasters on mountain economic and social systems, and improve disaster risk analysis, as well as the capability of risk management and disaster prevention and reduction.

Spatial-Temporal Characteristics of a Temperate-Glacier's Active-Layer Temperature and Its Responses to Climate Change: A Case Study of Baishui Glacier No. 1, Southeastern Tibetan Plateau

Based on the historical documents and measured data from the active-layer temperature （ALT） at A, B and C locations （4 670, 4 720 and 4 770 m a.s.l.） on Baishui Glacier No. 1, southeastern Tibetan Plateau, this paper analyzed spatial-temporal characteristics of ALT and its relationship with air temperature, and revealed the response of the active layer ice temperature towards climate change in the monitoring period. The results showed that the influence of air temperature on the active-layer ice temperature had a hysteresis characteristic on the upper of ablation zone and the lag period in- creased gradually with the altitude elevating. The decrease amplitude of ALT in the accumulation pe- riod was far below its increase magnitude in the ablation period. At the same time, the mean glacier ice temperatures at 10 m depth （T10） in A, B and C profile were obviously higher than most of glaciers previously studied. Measured data also showed that the mean ALT increased by 0.24℃ in 0.5-8.5 m depth of the C profile during 28 years from July 11, 1982 to July 10, 2009.

Air route network optimization in fragmented airspace based on cellular automata

Air route network optimization,one of the essential parts of the airspace planning,is an effective way to optimize airspace resources,increase airspace capacity,and alleviate air traffic congestion.However,little has been done on the optimization of air route network in the fragmented airspace caused by prohibited,restricted,and dangerous areas（PRDs）.In this paper,an air route network optimization model is developed with the total operational cost as the objective function while airspace restriction,air route network capacity,and non-straight-line factors（NSLF） are taken as major constraints.A square grid cellular space,Moore neighbors,a fixed boundary,together with a set of rules for solving the route network optimization model are designed based on cellular automata.The empirical traffic of airports with the largest traffic volume in each of the 9 flight information regions in China's Mainland is collected as the origin-destination（OD） airport pair demands.Based on traffic patterns,the model generates 35 air routes which successfully avoids 144 PRDs.Compared with the current air route network structure,the number of nodes decreases by 41.67%,while the total length of flight segments and air routes drop by 32.03% and 5.82% respectively.The NSLF decreases by 5.82% with changes in the total length of the air route network.More importantly,the total operational cost of the whole network decreases by 6.22%.The computational results show the potential benefits of the model and the advantage of the algorithm.Optimization of air route network can significantly reduce operational cost while ensuring operation safety.