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961.
珀金埃尔默公司分析科学部 《岩矿测试》2008,27(6):483-484
溴是一种在自然水体中都含有的元素,通常以B r-的形式存在。目前最常用的水净化方式就是向水中通入臭氧以杀灭细菌;而臭氧分解的副产物即为B r-转换成的B rO3-,这是一种公认的致癌物质。本实验室曾使用阴离子交换高效液相色谱(HPLC)与等离子体质谱(ICP-MS)联用分析B rO3-和B r-,方法虽能有效地将这两种溴形态分离,但分析每个样品需8 m in。本文试图建立新的方法缩短分析时间,并验证该方法应用于实际水样分析时测定其他含溴化合物的能力。1实验部分1.1高效液相色谱分析条件表1列出了等度淋洗和梯度淋洗两种模式下HPLC的分析条件,完成形态的分离。等度淋洗和梯度淋洗在分析中显示出不同 相似文献
962.
In multi-functional mountainous landscapes worldwide, conservation of natural values is a major task. Here, pro-active policies can be a way forward. National Environmental Quality Objectives (EQO) to solve environmental problems for future generations, however, often wrestle with being too visionary and lacking specificity, which complicates their implementation. The EQO 相似文献
963.
SAUTER Isabel KIENAST Felix BOLLIGER Janine WINTER Benjamin PAZÚR Robert 《山地科学学报》2019,61(12):2793-2809
Ecosystem services (ES) are highly impacted by human-induced land-use change. Progressive urbanization and agricultural land abandonment in Western Europe necessitate assessments of future land-change impacts on ES to ensure sustainable service management. The present study aims at evaluating future demand and supply of three key services (flood protection, nearby recreation and biodiversity) in the mountainous region of Vorarlberg, Austria. We mapped the ES for the referenced time step 2016 and two scenarios for 2050, assuming the continuation of current land-change trends and pressure on landscape development. Results for the referenced landscape in 2016 show the highest ES supply for intermediate levels, while ES supply was low in the lowlands and valley bottoms and in high-elevation areas. We found a high positive correlation of ES with the distribution of forested areas. In contrast, service demand was highest in low-elevation areas and decreased with increasing elevation. This indicates that densely settled and intensively used agricultural areas currently suffer from ES undersupply. The projected future development of land use showed an increase in both supply and demand of the selected ES. The overall service supply increased more than the respective demand due to some reforestation of open land. As forests were found to be important synergistic areas for overall service provision, we expect decreasing demand on related services. Locally, demand was found to exceed the supply of ES, especially in the densely populated Rhine valley- requiring further policy interventions. Such ES-related information may contribute to regional policy making and ensure the long-term provision of ESs for future generations. 相似文献
964.
965.
The snow cover over the Taurus Mountains affects water supply, agriculture, and hydropower generation in the region. In this study, we analyzed the monthly Snow Cover Extent (SCE) from November to April in the Central Taurus Mountains (Bolkar, Aladağlar, Tahtalı and Binboğa Mountains) from 1981 to 2021. Linear trends of snow cover season (November to April) over the last 41 years showed decreases in SCE primarily at lower elevations. The downward trend in SCE was found to be more pronounced and statistically significant for only November and March. SCE in the Central Taurus Mountains has declined about -6.3% per decade for 2500-3000 m in November and about -6.0% per decade for 1000-1500 m and 3000+ m in March over the last 41 years. The loss of SCE has become evident since the 2000s, and the lowest negative anomalies in SCE have been observed in 2014, 2001, and 2007 in the last 41 years, which are consistent with an increase in air temperature and decreased precipitation. SCE was correlated with both mean temperature and precipitation, with temperature having a greater relative importance at all elevated gradients. Results showed that there is a strong linear relationship between SCE and the mean air temperature (r = -0.80) and precipitation (r = 0.44) for all elevated gradients during the snow season. The Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), and the Mediterranean Oscillation (MO) winter indices were used to explain the year-to-year variability in SCE over the Central Taurus Mountains. The results showed that the inter-annual variability observed in the winter SCE on the Central Taurus Mountains was positively correlated with the phases of the winter AO, NAO and MO, especially below 2000 m elevation. 相似文献
966.
An average of eight snowfall events occur each year in the eastern Lesotho Highlands. These snowfall events are typically associated with cut-off low (CoLs) systems and mid-latitude cyclones. However, the moisture sources of the snowfall are unclassified and unclear. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, an air mass back trajectory model, has been used to evaluate moisture source waters locally in southern Africa and internationally in China and Europe. This study uses HYSPLIT to determine the source moisture of snow in Lesotho. A list of all 82 snowfall events in Lesotho spanning 2017 to 2022 was compiled using the Snow Report SA Instagram page, including the date and location of snowfall. A 72-hour back trajectory for each snowfall event was initiated for both Afriski and the whole of Lesotho. This amounts to models of moisture source trajectories for 28 and 82 snowfall days, respectively. These air mass pathways are classified according to their frequency per snowfall event, per month in the snow season, per year and for the full period. From this, associated moisture source regions and dominant air mass trajectories were identified. This study reports that the air mass trajectories associated with Afriski and Lesotho as a whole are very similar. The most common pathway of air mass trajectories transporting snow-bearing moisture to Lesotho was an inland trajectory from the northern regions of southern Africa. This pathway makes up 16.6% of all trajectories reported and is associated with the Angola Low, the Congo Air Boundary and the St. Helena High Pressure. 相似文献
967.
Despite the high efficiency of remote sensing methods for rapid and large-scale detection of subsidence phenomena, this technique has limitations such as atmospheric impact and temporal and spatial decorrelation that affect the accuracy of the results. This paper proposes a method based on an artificial neural network to improve the results of monitoring land subsidence due to groundwater overexploitation by radar interferometry in the Aliabad plain (Central Iran). In this regard, vertical ground deformations were monitored over 18 months using the Sentinel-1A SAR images. To model the land subsidence by a multilayer perceptron (MLP) artificial neural network, four parameters, including groundwater level, alluvial thickness, elastic modulus, and transmissivity have been applied. The model’s generalizability was assessed using data derived for 144 days. According to the results, the neural network estimates the land subsidence at each ground point with an accuracy of 6.8 mm. A comparison between the predicted and actual values indicated a significant agreement. The MLP model can be used to improve the results of subsidence detection in the study area or other areas with similar characteristics. 相似文献
968.
The glacial history of Pico de Orizaba indicates that during the Last Glacial Maximum, its icecap covered up to ~3000 m asl; due to the air temperature increasing, its main glacier has retreated to 5050 m asl. The retraction of the glacier has left behind an intense climatic instability that causes a high frequency of freeze-thaw cycles of great intensity; the resulting geomorphological processes are represented by the fragmentation of the bedrock that occupies the upper parts of the mountain. There is a notable lack of studies regarding the fragmentation and erosion occurring in tropical high mountains, and the associated geomorphological risks; for this reason, as a first stage of future continuous research, this study analyzes the freezing and thawing cycles that occur above 4000 m asl, through continuous monitoring of surface ground temperature. The results allow us to identify and characterize four zones: glacial, paraglacial, periglacial and proglacial. It was found that the paraglacial zone presents an intense drop of temperature, of up to ~9℃ in only sixty minutes. The rock fatigue and intense freeze-thaw cycles that occur in this area are responsible for the high rate of rock disintegration and represent the main factor of the constant slope dynamics that occur at the site. This activity decreases, both in frequency and intensity, according to the distance to the glacier, which is where the temperature presents a certain degree of stability, until reaching the proglacial zone, where cycles are almost non-existent, and therefore there is no gelifraction activity. The geomorphological processes have resulted in significant alterations to the mountain slopes, which can have severe consequences in terms of risk and water. 相似文献
969.
The accumulation processes of loess in northeastern (NE) China record the varying characteristics of the East Asian Monsoons (EAM) and the evolution of the local environment. In this study, grain size end-member analysis of the Dajiugang (DJG) section deposited since the Last Glacial in Chifeng City, NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE China. Results showed that the Chifeng loess comprises three grain size end-members (EM), EM1 (7.38 μm), EM2 (49.4 μm) and EM3 (90.00 μm), indicating the three transport dynamics of dust delivered to the region. The EM1 represents atmospheric dust as the background. The EM2, mainly derived from relatively distant-sources deposition, and EM3, material transported over a short distance, correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon (EAWM), respectively. Results of climate reconstruction, combined with other records, showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon (EASM) during the stadial-period [Marine Isotope Stage (MIS) 4 and MIS 2 stage]. The climate was predominantly warm and humid, with weak EAWM and surface winds and strong EASM in interstadial- period (MIS 3 and MIS 1 stage). Comparisons between indicators, e.g., EM3, the LR04 benthic δ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation. 相似文献
970.
Knowledge of seasonal variation in soil structural and related properties is important for the determination of critical periods during which soil is susceptible to accelerated erosion and other degradative processes. The purpose of this research was to evaluate the magnitude of seasonal variations in selected soil and deposited sediment properties in relation to soil erodibility for a Miamian silt-loam soil (Typic Hapludalf) in central Ohio. Erosion plots (USLE-type) were established on a 4·5% slope and maintained under bare, ploughed conditions from 1988 to 1991. Particle size distribution, bulk density(ρb), percentage water stable aggregates (WSA), soil organic carbon (SOC), and total soil nitrogen (TSN) of both soil and sediment samples were monitored between Autumn 1989 and Spring 1991. The soil and sediment particle size distributions followed no clear seasonal trends. Soil ρb increased following tillage (1·20 Mg m−3) and was highest (1·45 Mg m−3) during the autumn owing to soil slumping and consolidation upon drying. Low winter and spring values of ρb and %WSA (20–50% lower than in autumn) were attributed to excessive wetness and freeze–thaw effects. Both SOC and soil TSN contents progressively declined (from 2·18 to 1·79% and 1·97 to 1·75 g kg−1, respectively) after ploughing owing to maintenance of plots under bare, fallow conditions. Spring highs and autumn lows of sediment SOC (3·12 vs. 2·44%) and TSN (2·70 vs. 1·96 g kg−1) contents were a result of the combined effects of soil microbial activity and rainfall erosivity. Soil properties such as bulk density, SOC and WSA, which vary seasonally, can potentially serve as predictors of seasonal soil erodibility, which, in turn, could improve the predictive capacity of soil erosion prediction models. © 1998 John Wiley & Sons, Ltd. 相似文献