Comparison of two alluvial aquifers shows the probable role of river sediments on the release of arsenic in the groundwater of district Vehari,Punjab, Pakistan

The study was done to assess the effect of the river Sutlej on arsenic (As) contamination. Sampling was done from the alluvial plain with increasing distance from the river Sutlej in district Vehari and compared with the study done in the proximity of River Sutlej. Sixty (60) groundwater samples mostly from shallow depths were collected and analyzed for As concentrations. Multivariate statistical tools (PCA and CA), saturation index, piper plots and Gibbs diagrams were used to detect evidence about the interrelationship and sources of As and other water quality variables responsible for groundwater contamination. Results revealed that As concentration ranged from below detection limit to 156 µg/L indicating that 50% samples exceeding the WHO guidelines (10 µg/L) and 17% exceeding the Pakistan National Environmental Quality Standards (NEQS) limits (50 µg/L) Sutlej. The piper plot revealed that water chemistry of the study area was Ca–HCO₃^?, Ca–Mg–Cl, type. Correlations between As and HCO₃^? (r²?=?0.433) was positive, while negative correlations were observed between As–Mn²⁺ and As–Fe²⁺ (r²?=???0.102), (r²?=?0.107) respectively. Geochemical signatures of the groundwater in the study area showed that the As could be released by oxidative dissolution to some extent and elevated evaporation in the arid environment of the study area under the stimulus of alkaline water and high pH (range 7.1–8.4). Although the concentrations are exceeding the WHO limit in 50% of the water samples but, are less than the previous study done in Mailsi near River Sutlej. Further, the concentrations decreased as the distance from the River increased which shows the probable role of sediments deposited by the River Sutlej.     

Mechanical behavior and micro-structure of cement kiln dust-stabilized expensive soil

In this study, the effects of cement kiln dust (CKD) on the swelling properties, strength properties, and microstructures of CKD-stabilized expansive soil were investigated. Samples were prepared and stabilized with different CKD content ratios, ranging from 0 to 18% by dry mass. The results obtained show that the maximum swelling pressures decrease exponentially with increases in CKD content. Both the cohesion and unconfined compressive strength (UCS) increase at ratios below 10% CKD and then decrease slightly, above that ratio. CKD can also improve the strength of saturated, expansive soil. There is no visible change of UCS for soil without CKD when cured, while the UCS of a sample with 10% CKD content after curing for 90 days is higher than that after curing for only 1 day. This indicates that CKD can improve the long-term strength of expansive soil. Finally, microstructure analysis reveals that the addition of CKD reduces the montmorillonite content of expansive soil and decreases its swelling properties. The addition of CKD also changes the pore volume distribution, both the size and amount of macro-pores and micro-pores decrease with increase in CKD content. For saturated samples, the size of macro-pores is obviously reduced, while that of micro-pores is slightly increased for both treated and untreated soils. Hydration and saturation processes make the soil structure become dispersive which results in a lower strength, and adding CKD can restrain this process. The suggested optimal CKD content is between 10 and 14% and with a curing time of more than 27 days.     

粤东鸿沟山金矿区流纹斑岩锆石SHRIMP U-Pb定年、Lu-Hf同位素组成及其地质意义

鸿沟山矿区位于华南粤东莲花山钨矿床的中部,是近年来通过地质矿产调查新发现具有找寻金矿潜力的矿床之一。本文以与鸿沟山金等多金属矿化关系密切的流纹斑岩为研究对象,开展了锆石SHRIMP U-Pb定年、流纹斑岩和矿石岩石地球化学、锆石Lu-Hf同位素组成特征研究。获得流纹斑岩锆石206Pb/238U加权平均年龄为169.1±1.5Ma,说明岩体形成于中侏罗世。在微量元素特征方面,流纹斑岩都表现为相对亏损大离子亲石元素Ba、Sr和高强场元素Nb、P、Zr、Hf,富集大离子亲石元素Rb,高强场元素U、Ce、Sm和轻稀土元素La、Nd,流纹斑岩与矿石稀土元素特征基本相似,Eu具中等负异常,但随着矿化强度的增强稀土元素更加富集。流纹斑岩εHf(t)(-15.0~2.2)分布范围宽,二阶段模式年龄TDM2主要变化范围为0.82~0.93 Ga,表明成岩物质主要来源于新元古代古老地壳变质泥岩和变质砂岩部分熔融,并有幔源物质的加入。因此,围绕着该时间段的流纹斑岩岩体,对于找寻W、Cu、Pb、Zn、Bi、Au、稀土、稀有和稀散元素矿产具有重要意义。     

基于高分二号卫星数据的煤矿区地质灾害信息提取研究

随着遥感数据获取技术和能力的全面提高,遥感数据呈现出明显的大数据特征。发展适应于遥感大数据的智能分析和信息挖掘技术,成为当前遥感技术研究的前沿。高分二号（GF-2）卫星数据是我国首颗自主研发的亚米级高分辨率卫星数据,具有观测幅宽、重访周期短、高辐射精度、高定位精度等优势,为未来我国地质灾害的长期、动态地监测和研究提供了高精度、稳定可靠的数据源。本文选取安徽谢桥煤矿2015年1月8日的GF-2卫星影像为研究数据,在对煤矿区主要地质灾害遥感地学分析的基础上,采用面向对象的影像分析方法对研究区由采煤活动所诱发的地质灾害信息进行自动提取。结果表明：利用GF-2卫星数据能够有效地识别地质灾害体的位置、范围、形态等空间分布特征;面向对象的自动提取方法对于煤矿区大面积的积水塌陷盆地、小规模的塌陷坑和线性的地裂缝都有很高的提取精度,识别精度达90% 以上;基于逐层剔除的思路构建的提取规则,为GF-2数据在地质灾害调查和大数据分析中的应用提供了很好的技术支持,也为其它地物目标的提取提供了参考,但在特征的选择和阈值的设定上需要具体分析。     

Real-time identification of urban rainstorm waterlogging disasters based on Weibo big data

With the acceleration of urbanisation in China, preventing and reducing the economic losses and casualties caused by urban rainstorm waterlogging disasters have become a critical and difficult issue that the government is concerned about. As urban storms are sudden, clustered, continuous, and cause huge economic losses, it is difficult to conduct emergency management. Developing a more scientific method for real-time disaster identification will help prevent losses over time. Examining social media big data is a feasible method for obtaining on-site disaster data and carrying out disaster risk assessments. This paper presents a real-time identification method for urban-storm disasters using Weibo data. Taking the June 2016 heavy rainstorm in Nanjing as an example, the obtained Weibo data are divided into eight parts for the training data set and two parts for the testing data set. It then performs text pre-processing using the Jieba segmentation module for word segmentation. Then, the term frequency–inverse document frequency method is used to calculate the feature items weights and extract the features. Hashing algorithms are introduced for processing high-dimensional sparse vector matrices. Finally, the naive Bayes, support vector machine, and random forest text classification algorithms are used to train the model, and a test set sample is introduced for testing the model to select the optimal classification algorithm. The experiments showed that the naive Bayes algorithm had the highest macro-average accuracy.     

张广才岭南段两个侏罗纪花岗岩体的地球化学特征及其地质意义

通过LA-ICP-MS锆石U-Pb定年和岩石化学分析,研究了张广才岭南段上营北岩体和帽儿山岩体的形成年代,地球化学特征和形成环境。上营北岩体为中粗粒钾长花岗岩,帽儿山岩体为中细粒黑云母钾长花岗岩。上营北岩体的加权平均年龄为178.9±2.7 Ma,帽儿山岩体为183.7±2.4 Ma,均为早侏罗世侵入岩。上营北岩体和帽儿山岩体主量元素都具有Si O_2和K_2O含量较高,Ti O_2、Mg O、Ca O含量较低,TFe O/Mg O值较高的特点;上营北岩体A/CNK=0.98~1.08,里特曼指数σ=1.51~2.66;帽儿山岩体含铝指数A/CNK=1.00~1.01,里特曼指数σ=2.12~2.36。上营北岩体稀土元素配分模式为海鸥型,轻重稀土分馏不明显;帽儿山岩体稀土元素配分模式为右倾型,轻稀土较重稀土富集;两个岩体均富集Rb、K,Ba、Nb、Ta、Sr、Ti、P、Ho、Er、U、Eu等元素出现不同程度的亏损。地球化学特征分析显示上营北岩体和帽儿山岩体均为A_2型花岗岩,为后造山型花岗岩,形成于兴蒙造山带后造山的伸展环境。     

羌塘地块西南缘上侏罗统-下白垩统海相地层的发现

通过1∶5万区域地质调查,在青藏高原羌塘地块西南缘鸡夯地区原划上三叠统日干配错群中新识别出一套上侏罗统—下白垩统地层。本文根据该套地层的岩石组合以及古生物面貌特征,初步探讨了该套地层的沉积环境和沉积相特征,对其中发育的玄武岩夹层采用锆石U-Pb(LA-ICP-MS)同位素测年方法,获得其年龄为118.3±2.1Ma。在发育的生物碎屑灰岩夹层中采集了珊瑚、双壳类、腕足、腹足类化石,化石资料显示该套地层形成于晚侏罗世—早白垩世。这是首次在南羌塘地块发现该时期海相地层,这一发现证明南羌塘地块在晚侏罗世—早白垩世时期海水并未完全退出,而是局部发育海相三角洲。     

Estimating satellite phase fractional cycle biases based on Kalman filter

Phase fractional cycle biases (FCBs) originating from satellites and receivers destroy the integer nature of PPP carrier phase ambiguities. To achieve integer ambiguity resolution of PPP, FCBs of satellites are required. In former work, least squares methods are commonly adopted to isolate FCBs from a network of reference stations. However, it can be extremely time consuming concerning the large number of observations from hundreds of stations and thousands of epochs. In addition, iterations are required to deal with the one-cycle inconsistency among FCB measurements. We propose to estimate the FCB based on a Kalman filter. The large number of observations are handled epoch by epoch, which significantly reduces the dimension of the involved matrix and accelerates the computation. In addition, it is also suitable for real-time applications. As for the one-cycle inconsistency, a pre-elimination method is developed to avoid iterations and posterior adjustments. A globally distributed network consisting of about 200 IGS stations is selected to determine the GPS satellite FCBs. Observations recorded from DoY 52 to 61 in 2016 are processed to verify the proposed approach. The RMS of wide lane (WL) posterior residuals is 0.09 cycles while that of the narrow lane (NL) is about 0.05 cycles, which indicates a good internal accuracy. The estimated WL FCBs also have a good consistency with existing WL FCB products (e.g., CNES-GRG, WHU-SGG). The RMS of differences with respect to GRG and SGG products are 0.03 and 0.05 cycles. For satellite NL FCB estimates, 97.9% of the differences with respect to SGG products are within ±?0.1 cycles. The RMS of the difference is 0.05 cycles. These results prove the efficiency of the proposed approach.     

基于地理加权模型的农村居民点空间格局及影响因子分析——以湖北省麻城市为例

以湖北省麻城市2009年和2015年农村居民点为研究对象,采用区位指数和核密度测算法对农村居民点空间分布形态进行分析,运用传统最小二乘法和地理加权模型从全域和局部角度分析自然地貌、社会经济、生态限制等因素影响农村居民点空间演变的作用机制。研究得出:麻城市2009—2015年农村居民点用地面积增长率达6.92%,斑块主要以分散式外延扩张为主,空间结构演变总体上呈现沿沪汉蓉快速铁路和武麻公路向四周扩散的连续分布特征。从全域上看,农村居民点分布格局与坡度、公路、建制镇、风景名胜区、河流呈空间负相关关系;从局部影响程度来看,最大正向影响因子为人均收入和高程,负向影响因子主要是坡度和河流,其他影响因子随地理位置变化正负向影响均存在。