Temporal variations in aerosol composition at Lanzhou City, Northwestern China

Although LanTAaou is one of the most heavily polluted cities in China, the composition of its air pollutants have not yet been studied in detail. The data of four months on the concentrations and compositions of ions from daily air-filter samples in the winter and spring during 2007-2008 were analyzed to investigate temporal trends and their possible causes. The results indicate that mean concentrations of almost all the aerosol components are greater in winter than in spring due to stronger emissions in winter and weaker localized dispersion. Spring dust storms are the major cause of the highest peak PM10 concentrations recorded during the study period; however, these elevated levels were transient. Ion concentrations related to coal combustion show the greatest reduction from winter to spring, while the concentrations of strong crustal components show a less-pronounced reduction. Strong cycles in the levels of particulate matter （PM） and all ions are also observed during the winter months due to meteorological conditions. Depending on the season, nine different ions accounted for 20%-50% of the PM concentration. The particle size of polluting ions was constant at times of increasing PM concentrations （particularly during winter）, whereas the particle size of crustal ions in- creased dramatically during spring dust storms. Local meteorological conditions （especially wind speed） have a strong influence on the levels of pollutants. Four dust storms were noted, including one during winter. In summary, the regional transport of desert dust from the Gobi can significantly affect air quality and the chemical composition of aerosols in Lanzhou. The dust storms can strongly increase concentration of crustal ions, which are characteristics of deserts in northwestern China. This observation is in agreement with back-trajectories, which show reduced levels of pollutant ions during dust storms. Data on nitrate：sulfate ratios indicate that stationary point sources are the main source of ions rather than mobile sources.

Spatiotemporal variations and driving factors of habitat quality in the loess hilly area of the Yellow River Basin:A case study of Lanzhou City,China

Rapid industrialization and urbanization have led to the most serious habitat degradation in China,especially in the loess hilly area of the Yellow River Basin,where the ecological environment is relatively fragile.The contradiction between economic development and ecological environment protection has aroused widespread concern.In this study,we used the habitat quality of Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST-HQ)model at different scales to evaluate the dynamic evolution characteristics of habitat quality in Lanzhou City,Gansu Province of China.The spatiotemporal variations of habitat quality were analyzed by spatial autocorrelation.A Geographical Detector(Geodetector)model was used to explore the driving factors that influencing the spatial differentiation of habitat quality,including natural factors,socio-economic factors,and ecological protection factors.The results showed that the habitat quality index of Lanzhou City decreased from 0.4638 to 0.4548 during 2000-2018.The areas with reduced the habitat quality index were mainly located in the Yellow River Basin and Qinwangchuan Basin,where are the main urban areas and the new economic development areas,respectively.The spatial distribution of habitat quality presented a trend of high in the surrounding areas and low in the middle,and showed a significant positive spatial autocorrelation.With the increase of study scale,the spatial distribution of habitat quality changed from concentrated to dispersed.The spatial differentiation of habitat quality in the study area was the result of multiple factors.Among them,topographic relief and slope were the key factors.The synergistic enhancement among these driving factors intensified the spatial differentiation of habitat quality.The findings of this study can provide a scientific basis for land resources utilization and ecosystem restoration in the arid and semi-arid land.

Statistical landslide susceptibility assessment in a dynamic environment:A case study for Lanzhou City,Gansu Province,NW China

This study presents a statistical landslide susceptibility assessment(LSA) in a dynamic environment. The study area is located in the eastern part of Lanzhou, NW China. The Lanzhou area has exhibited rapid urbanization rates over the past decade associated with greening, continuous land use change, and geomorphic reshaping activities. To consider the dynamics of the environment in the LSA, multitemporal data for landslide inventories and the corresponding causal factors were collected. The weights of evidence(Wof E) method was used to perform the LSA. Three time stamps, i.e., 2000, 2012, and 2016, were selected to assess the state of landslide susceptibility over time. The results show a clear evolution of the landslide susceptibility patterns that was mainly governed by anthropogenic activities directed toward generating safer building grounds for civil infrastructure. The low and very low susceptibility areas increased by approximately 10% between 2000 and 2016. At the same time, areas of medium, high and very high susceptibility zones decreased proportionally. Based on the results, an approach to design the statistical LSA under dynamic conditions is proposed, the issues and limitations of this approach are also discussed. The study shows that under dynamic conditions, the requirements for data quantity and quality increase significantly. A dynamic environment requires greater effort to estimate the causal relations between the landslides and controlling factors as well as for model validation.

Influence of Dust Weather on Air Quality in Lanzhou City

[Objective] The study aimed to discuss the effects of dust weather on air quality in Lanzhou City. [Met]hod] Under the influence of a strong sandstorm during March 8 -15, 2013 on air quality in Gansu Province, the changes of wind speed, atmospheric visibility and PM10 concentra- tion as well as air pollution in Lanzhou were analyzed. [ Result] The dust weather during March 8 -15, 2013 affected Lanzhou City for the longest time in recent 10 years, and the city suffered medium pollution on March 8 and heavy pollution during March 9 -15 under the influence of the dust weather, while PM10 was the pdmary pollutant. [ Condusion] The research could provide the corresponding technical support for the prevention and control of environmental pollution in Lanzhou City.

Formation Mechanism of Poor Settlements in Lanzhou City

Clarifying the formation mechanism of poor settlements is the " pathological" basis for urban regeneration and poverty governance.On the basis of scientific determination of 155 poor settlements in Lanzhou City,this paper classified their types and analyzed the characteristics of their quantity distribution and density distribution. From the perspective of spatial and social interaction,and combined the internal factors and external factors,this paper put forward the formation mechanism of poor settlements,namely,superposition of unit society collapse and physical environment degradation,interaction between differentiation of residents' income and reform of housing institution,interweaving between urban discontinuous planning and jumping construction,coupling between passive urbanization and active urbanization,and derivation of lagged economic development and unique regional culture.

Seismic Risk Assessment and Maximum Magnitudes of Potential Earthquakes on Active Faults near Lanzhou City

The Zhuanglang river and Baiyin Baiyangshu river faults are late Quaternary faults near Lanzhou city, which pose a threat to the safety of the city. However, the cause of medium- strong earthquakes along the fault is rather complicated and even uncertain. It is important for us how to assess the magnitudes of maximum potential earthquakes and the seismic risk of the faults. The authors make reference to the method that Wen Xueze, et ai. （2007） developed to assess the magnitudes of maximum potential earthquakes in sub-areas of moderately and weakly active faults in the eastern Chinese Mainland, and brought forward an empirical relationship between the maximum magnitudes Mmax and the at/b values of the sub-areas＇ frequency- magnitude relationships in the Lanzhou area. By using this empirical relationship, the authors have estimated the upper-limits Mu of the Zhuanglang river and Baiyin Baiyangshu river active faults near Lanzhou city as Ms6.9 and 6.3, respectively. In addition, they have assessed the average interval recurrence time and the probabilities of destructive earthquakes on the faults.

Analysis of the First Soaking Rain Process in Lanzhou City in 2011

[Objective]The research aimed to analyze the first soaking rain process in Lanzhou in 2011.[Method]By diagnostic analyses on weather scale,meso-scale system and physical quantity when the first soaking rain weather happened in Lanzhou City in 2011,formation reason and physical quantity characteristics of the soaking rain weather were discussed.[Result]Combination of the plateau low vortex and westerly cold trough was influence system of the first soaking rain.There was a southwest-southeast airflow from Sichuan Basin to Hexi in front of the trough at 700 hPa.It was commonly referred to as ＂ inverted-buckle wind＂,and provided sufficient water vapour for occurrence and maintaining of the precipitation.Convergence at the low layer and divergence at the high layer were favourable for vertical motion.Analyses on physical quantity and meso-scale system also proved important role of the ＂ inverted-buckle wind＂ at the low layer.[Conclusion]The research provided reference for real-time forecast business of the long drought turning rain in spring.

A Study of the Relationship between Air Pollutants and Inversion in the ABL over the City of Lanzhou

By analyzing the pollutant concentrations over the urban area and over the rural area of the city of Lanzhou, Gansu Province, China, the relationships between the daytime inversion intensity and the pollutant concentration in the atmospheric boundary layer （ABL） are studied with the consideration of wind speed and direction, potential temperature, specific humidity profiles, pollutant concentration in the ABL, the surface temperature, and global radiation on the ground. It was shown that the daytime inversion is a key factor in controlling air pollution concentration. A clear and positive feedback process between the daytime inversion intensity and the air pollutants over the city was found through the analysis of influences of climatic and environmental factors. The mechanisms by which the terrain and air pollutants affect the formation of the daytime inversion are discussed. The solar radiation as the essential energy source to maintain the inversion is analyzed, as are various out-forcing factors affecting the inversion and air pollutants. At last, a physical frame of relationships of air pollution with daytime inversion and the local and out-forcing factors over Lanzhou is built.

Evaluation of Rural Tourism Resources based on the Tourists Perspective: A Case Study of Lanzhou City, China

Rural tourism has become a hot spot in China’s tourism development. Based on the AHP model and the comprehensive evaluation method of fuzzy cognition, this paper builds an evaluation system for the evaluation of rural tourism resources, including resource value, environmental factors, reception conditions with three criterion layers, and 25 evaluation factors. We recovered 574 valid questionnaires through two online forms and field research in Lanzhou city, and then used them to complete the empirical analysis. The results show four main aspects of the tourists’ perspective on rural tourism resources. Firstly, rural tourists are concerned about higher service facilities. The evaluation of rural tourism resources pays more attention to the reception conditions, and tourists pay more attention to the facilities of the reception conditions. In addition, the reception condition value accounts for a more concentrated 8–10 points(61.4%), which is higher than environmental elements(58.87%) and the value of the resource itself(54.26%). Secondly, tourists’ attention to rural tourism resources mainly focuses on the pleasurable(0.1152), tour line design(0.1014), experience(0.0765), ornamental(0.0747) and other aspects. Thirdly, the degree of cognition mainly focuses on nature(4508), environmental safety(4469), pleasantness(4387), accommodation conditions(4367), tour line design(4363) and other aspects of the rural tourism resources. Fourthly, the cognition of rural tourism resources is basically given priority with 6–9 points, and environmental factors accounted for the highest portion. However, rural tourists have higher expectations for the popularization and education of rural tourism resources, but the sense of acquisition is relatively low. Through the further improvement and improvement of the naturalness of environmental resources, environmental safety of reception conditions, and the enjoyment of external traffic and resource value, the overall benefit of rural tourism resources is maximized. The results of this study can provide reference for the theoretical foundation of rural tourism resources.

Ground-based observation of aerosol optical properties in Lanzhou, China

Aerosol optical properties from August 2006 to July 2007 were obtained from ground-based and sky radiance measurements in Semi- Arid Climate and Environment Observatory of Lanzhou University （SACOL）, China. High aerosol optical thickness （AOT） associated with low .Angstrom exponent （α） was mainly observed in spring, which was consistent with the seasonal dust production from Hexi Corridor. The maximum monthly average value of AOT 0.56 occurred in March of 2007, which was two times larger than the minimum value of 0.28 in October of 2006. Approximately 60% of the AOT ranged between 0.3 and 0.5, and nearly 93% ofα value varied from 0.1 to 0.8, which occurred in spring. The significant correlation between aerosol properties and water vapor content was not observed. The aerosol volume size distribution can be characterized by the bimodal logarithm normal structure： fine mode （r 〈 0.6 μm） and coarse mode （r 〉 0.6 μm）. Aerosols in spring of SACOL were dominated by large particles with the volume concentration ratio of coarse to fine modes being 7.85. The average values of asymmetry factor （g） in the wavelength range 440-1020 nm were found to be 0.71, 0.67, 0.67 and 0.69 in spring, summer, autumn and winter, respectively.