Some critical factors for engineering and environmental microgravity investigations

The gravity method is one of the geophysical tools used for engineering and environmental investigations where the detection of cavities, karst phenomena, subsoil irregularities, or landfills is essential. In many cases, deep or small-scale heterogeneities generating low-amplitude anomalies have to be detected and the reliability of further interpretation requires highly accurate measurements, carefully corrected for any quantifiable disturbing effects. The purpose of this study is to investigate the factors likely to limit measurement quality and how to make improvements.Calibrations of a Scintrex gravimeter were made between French relative and absolute base stations, and the relative uncertainties on the calibration factors were estimated for these links. Ranging from 10⁻³, for calibration on an old gravity net, to 10⁻⁴, for a high amplitude absolute base line, this accuracy will be generally sufficient for microgravity surveys.Continuous gravity recordings of Scintrex gravimeters, installed at the same stable site, enabled the estimation of the stability and accuracy of the instruments and revealed that some of the time variations of g measurements, such as instrumental drift, tidal effects and seismic noise, are not entirely removed by standard processing procedures. The accuracy of corrected gravity measurements is mainly limited by inadequate corrections of tidal effects and by a poor estimation of ocean loading effects. In comparison with residual defaults in tidal corrections, instrumental and seismic noises are taken more properly into account by statistical data processing.In field operation, residual tidal effects are generally integrated into an experimental terrain drift estimated on the basis of frequent repeated measurements. A differential gravity approach, based on a fixed gravimeter reference whose recordings are used to correct measurements made with a mobile gravimeter, has also been investigated at a test site. Compared to standard processing, this method can help improve repeatability of gravity measurements.Microgravity surveys in the urban environment require effective and accurate consideration of the effects of infrastructures, nearby buildings and basements, as well as those of topography, in the vicinity of a gravity station. Correction procedures, applied at the same experimental site, where gravity points are located close to buildings, walls and basement slope, appear to have almost totally eliminated these disturbances.     

关于环境岩土工程

回顾了环境岩土工程的发展历史 ,讨论了其定义、与传统岩土工程的区别以及研究内涵 ,介绍了国际上的发展现状和活动 ,指出了我国在这一领域中的差距 ,最后列出了环境岩土工程的一些重要课题。     

东北亚区域国际合作中跨境交通走廊的发展及其对环境退化的影响

东北亚区域跨境交通走廊由于图们江地区国际合作开发的深入而得到迅速发展，其对区域环境退化已经形成和将要形成重大的影响。本文在对东北亚区域国际合作中跨境交通走廊的运行及其发展进行深入研究的基础上，对跨境交通走廊的发展对区域环境退化的影响作了战略性的评价与分析，并对其未来发展提出若干建议。     

速度谱资料整理专家系统

人工整理地震速度谱资料是比较繁琐的。速度谱资料整理专家系统的研制成功,可使这一工作实现自动化。该系统将人们分析、解释速度谱的大量经验整理成专家系统的知识,通过知识源、调度源协调工作的推理策略,实现了反复择优的过程,解决了能量因智能选择的难点。它既可进行单谱分析,也可进行多谱综合分析。试用的结果表明,其整理解释的结果与领域专家的水平相当。     

Climatization of environmental degradation: a widespread challenge to the integrity of earth science

ABSTRACT

To guide scientists and society regarding the hydrologic consequences of anthropogenic climate change, earth scientists increasingly develop qualitative predictions and quantitative ensembles of models, some of which have important economic or (geo)political implications. However, with unprecedented human population, environmental degradation, and water scarcity, climatic factors are increasingly invoked falsely to explain failures of environmental governance, a phenomenon termed climatization. We propose a first typology of climatization in hydrology. Scientific climatization occurs when – during the normal course of a scientific investigation – a hydrologic state is falsely attributed to climatic factors, often due to a conceptual model that excludes human impacts or a simplified methodology that fails to quantify uncertainty. In contrast, securitization-aligned climatization occurs when a securitizing state actor requires that scientists attribute observed hydrologic states to climatic factors. Maintaining the credibility of earth science requires that earth scientists vigorously contest both scientific climatization and securitization of global change hydrology.     

Optimal season for discriminating C3 and C4 grass functional types using multi-date Sentinel 2 data

ABSTRACT

The ability of remote sensing systems to optimally discriminate and map C3 and C4 grass species varies over time, due to environmental changes, which influence their phenological, physiological and morphological characteristics. In this regard, the discrimination of C3 and C4 grasses is insufficient when using a single image acquired at a specific period. In this study, multi-date Sentinel 2A MultiSpectral Instrument (MSI) data were explored to determine the optimal period for classifying and mapping Festuca costata, C3 and Themeda Triandra, C4 grasses in the montane grasslands of South Africa. The study further assessed how seasonal variations in species classification can be explained by climatic variability (rainfall and temperature). Results showed that image acquisition dates influence the discrimination accuracy, spatial representation of the two grass species, as well as the performance of spectral bands. The winter period also presents a better temporal window for discriminating C3 and C4 target grass species, with higher overall classification accuracies (between 91.8% and 95.3%), than summer (between 81.4% and 90.3%). Lower omission (between 2.8% and 11.6%) and commission (between 2.5% and 14.2%) errors were also observed when discriminating using winter images, as compared to those acquired in summer. Summer images showed large grass species areal coverage (e.g. in November and March, C3 and C4 covered ±25%), whereas in winter (mainly August), a notable decrease was observed. Overall, findings of the study have demonstrated the relevance of multi-date Sentinel data in discriminating C3 and C4 grass species. There is, however, a need to explore the classification ability of Sentinel 2 derivatives, especially during early summer and winter fall.     

重庆市大气混合层厚度的计算和分析

应用国家标准ＧＢ／Ｔ１３２０１９１规定的方法计算分析了重庆市１９８１～１９０年大气混合层厚度;并用罗氏法计算了重庆市１９８８年的大气混合层厚度;并对２种方法所得结果进行了对比分析。结果表明：重庆市大气混合层厚度多年的平均值为３４６ｍ;逐年变化不明显;季节变化明显;日变化非常明显;大气稳定度是决定大气混合层厚度的主要因子。罗氏法因考虑的因子比较多,故较准确,因此在有常规观测资料的地方应用罗氏法较好     

在垃圾焚烧厂规划中地理信息系统的应用

德国萨克森-安哈特州（Sachsen-Anhalt）州府玛葛得堡市（Magdeburg）计划在其北部2县4880km²的地域内建立一个垃圾焚烧厂,焚烧厂厂址规划要符合《环境质量影响评价法》.理想的厂址应该是一片包含环境质量影响评价要素最少的“空地”;为垃圾运输方便,厂址与主要交通干线的距离不应超过5km.由于规划区内土地利用覆盖复杂,常规的实地勘察和资料研究难以把各方面的评价要素信息考虑周全,因此利用地理信息系统（PC ARC/INFO）帮助解决问题,比如专题图件比例尺不统一的问题、信息叠加程度过高的问题等.通过多种比例尺机助制图、比较研究,共找出6个潜在的厂址,可以考虑建厂.编辑了6幅“潜在厂址”专题图,本文以其中1幅举例描述.     

Stochastic evolution of hydraulic geometry relations in the lower Yellow River of China under environmental uncertainties

Hydraulic geometry relations comprise a classic way to understand characteristics of a river. However, environmental changes pose large uncertainties for the reliability of such relations. In the current study, on the basis of the ordinary differential equations (ODEs) formed through linear treatment of the deterministic power-law hydraulic geometry relations, a set of stochastic differential equations (SDEs) driven by Fractional white noise and Poisson noise are developed to simulate the historical dynamic probability distributions of typical hydraulic geometry variables such as slope, width, depth, and velocity with bankfull discharge variation over time in the lower Yellow River of China. One group of possible stochastic average behaviors within the next 50 years are calculated under three different design incoming water-sediment conditions (including 300, 600, and 800 million t of annual average sediment discharge). In each part of the lower reaches, after estimation of the SDE parameters using a nonparametric maximum likelihood estimation (MLE) method, the model is carefully examined using Monte Carlo simulation as compared with the deterministic control models. The results of this comparison reveal the potential responses of hydraulic geometry characteristics to environmental disturbances, and the average trends mainly agree with the measurements. Comparisons among the three different prediction results reveal the stochastic average solution generally is greater than the deterministic solution. The results also confirm the severe negative impacts that result from the condition of 300 million t of incoming sediment, thus, pointing out the need to raise the level of river evolution alert for the lower Yellow River of China in the future. Moreover, with the help of the stochastic computation, the stream power and hydraulic width/depth ratio could be representative of an effective systematic measure for river dynamics. The proposed stochastic approach is not only important to development in the field of fluvial relations, but also beneficial to the practical design and monitoring of a river system according to specified accuracy requirements.