痕量价态金的载炭泡塑吸附分离研究

研究了载炭泡塑对不同价态金的吸附选择性。当ＨＣｌ溶液浓度１％－１０％时，载炭泡塑对纳克量Ａｕ（Ⅲ）吸附率为９６．３％－９６．８％，而对Ａｕ（Ⅰ），Ａｕ（０）不产生吸附，分别在溶液和残渣中的Ａｕ（Ⅰ）和Ａｕ（０）经过滤分离，用王水处理后，由载炭泡塑分别吸附，其回收率分别为９６．５％和９８．９％。     

贵州山区土壤微生物生物量的碳同位素组成与有机碳同位素效应

选择贵州岩溶区3个不同海拔高度上的旱地作为实验点,进行了绿肥(紫花光叶苕,C3豆科植物)的输入实验,目的是了解通过输入绿肥之后土壤微生物生物量碳(SMBC)的响应,以及微生物生物量中碳同位素比值的变化,来判断植物分解作用期间有机碳的同位素效应,即微生物分解对13C的分馏作用和微生物对有机质的选择性利用.实验结果表明,在实验地里加入绿肥之后,年平均气温较高的实验地的SMBC响应较快,并且其值高于其余两个年平均气温较低的实验地,说明SMBC主要来源于植物残留物,其值的大小受控于气温.在加入绿肥之后,并未在各自的实验地和对照地之间出现δ¹³C值的差异,而是在植物残留物的分解达到一定程度后实验地的δ¹³C值才高于对照地,但在年平均气温较低的实验点上始终未出现这种差异,说明植物残留物的分解程度和质量将影响SMBC的δ¹³C值,这种现象也进一步说明土壤有机碳的同位素效应是微生物对13C的分馏和对有机质的选择性利用并存的过程.3个实验点上的土壤有机碳的δ¹³C值大小的顺序与SMBC的δ¹³C值大小的顺序相一致,表明SMBC的δ¹³C值能够反映相应样品中的土壤有机质δ¹³C值的总的变化趋势,并可能是控制土壤有机质的δ¹³C值大小的主要的影响因素.     

A comparative analysis of enzyme leach and mobile metal ion selective extractions; case studies from glaciated terrain, northern Ontario

The enzyme leach and MMI (mobile metal ion) selective digestions are rapidly gaining popularity in the exploration community because of their successful track record in non-glaciated, arid and tropical climatic regions. Few successful case studies from high-latitude, temperate regions have been published to date. Also lacking is a comprehensive discussion of the constraints and limitations of these geochemical methods and how they affect the successful interpretation of selective-leach survey results in glaciated regions. This paper evaluates each method using specific examples from four case studies undertaken in the glaciated region of northern Ontario. The case studies clearly demonstrate that both the MMI and enzyme leach selective digestions provide the explorationist with useful information, which, when used in conjunction with other exploration tools, can assist with the identification of potential diamond drill targets. Notwithstanding this, the techniques do not appear to work well as ‘stand alone' methods. The importance of following strict sampling protocols and obtaining high-quality observational information on the sampling site and media collected cannot be overstressed. It is only by filtering out the many variables that arise in any sampling program that a sound interpretation of the data can be made. The case studies have drawn attention to some of the apparent shortfalls of the techniques. Of these, issues such as the ability to reproduce survey results from year to year and the recognition of anomalous element associations which specifically target blind mineralisation are probably those which require significant follow-up work. Clearly, additional case studies are required from the glaciated regions of the world to assist with the optimisation of geochemical response of MMI and enzyme leach selective extractions. The mechanisms responsible for the formation of surface geochemical anomalies over deeply buried mineralisation are not well understood. The observed patterns of geochemical response in surface soils and both shallow and deep ground waters over concealed mineralisation should assist with the development of new dispersion models.     

Detection of subtle deforestation due to logging using satellite remote sensing in wet and dry savanna woodlands of Southern Africa

Tropical deforestation through logging activities poses a direct threat to biodiversity. However, the detection of logging has remained a challenge. Based on study sites in Zimbabwe and Zambia, we tested whether the Normalized Difference Vegetation Index (NDVI) and the Coefficient of Variation in NDVI (CVNDVI) derived from high and medium spatial resolution satellite data could be used to detect logging in dry and wet miombo woodlands. Separately, we integrated NDVI and CVNDVI in logistic regression to test whether each can be used to successfully predict logging in the study sites. We tested whether the spatial resolution of satellite data has an effect in detection of logging using NDVI and CVNDVI derived from Landsat 8 and Worldview-2. Based on the ROC curves, we concluded that remotely sensed data could provide an effective predictive tool for detecting logging. However, in wet miombo woodlands the predictive power of remotely sensed data is weak.     

济南西部地区不同类型污染源作用下土壤各类元素含量特征及选择性种植浅析

通过分析研究区不同类型污染源条件下各类土壤元素含量的顺序,认为重金属在各类污染源土壤剖面中含量的顺序主要为:垃圾堆放污染类污水排放污染类禽畜粪便污染类;水溶性相对较强的K+,Mg2+,Na+,Cl-,SO2-4等离子,受污水排放类污染的影响明显,含量顺序为:污水排放污染类禽畜粪便污染类垃圾堆放污染类;NO-3在土壤中含量的顺序为:禽畜粪便污染类污水排放污染类垃圾堆放污染类;土壤主要常量养分在土壤中含量的顺序为:污水排放污染类垃圾堆放污染类禽畜粪便污染类。选择性种植的观点认为,在土壤肥力充足但重金属元素富集的土地,选择对该重金属元素富集较少的蔬菜(瓜果)进行种植,一方面充分利用了土壤肥力,另一方面较好地规避了重金属对作物的污染。     

锑的地球化学行为以及锑同位素研究进展

火山和成矿地质现象表明硼可以在含水流体和气体中运移,本文应用离子选择电极法测定水热气体中硼的溶解度,以揭示硼的气态迁移能力。使用氟硼酸盐选择电极,测定了经氟硼酸化的硼酸标准溶液和含硼气体凝结水的电位,当硼含量处于地质流体的主要范围内（0.52～524.50 mg/L）时,电极电位与硼浓度的对数呈现出灵敏度很高的能斯特线性关系,标准曲线具有很好的稳定性和重现性。本方法测定硼的检出限为0.13 mg/L,低于饮用水标准规定的硼含量限值,适用于测定水热气体中的硼含量。硼酸挥发实验显示,硼在150℃、0.37 MPa水蒸气中的含量可达0.65%～0.72%,与富硼火山喷气的硼含量相符,显示硼在高温水热条件下可在气相中显著迁移,且H₃BO₃气态分子是硼的主要迁移形式之一。矿床地质特征和实验表明,硼的气态迁移和电气石化与稀有金属型伟晶岩的形成和矿化以及某些热液-气成型Sn-W、Mo矿床和斑岩型Cu、Au矿床的形成密切相关。     

Empirical determination of geometric parameters for selective omission in a road network

Selective omission in a road network is a necessary operation for road network generalization. Most existing selective omission approaches involve one or two geometric parameters at a specific scale to determine which roads should be retained or eliminated. This study proposes an approach for determining the empirical threshold for such a parameter. The idea of the proposed approach is to first subdivide a large road network, and then to use appropriate threshold(s) obtained from one or several subdivisions to infer an appropriate threshold for the large one. A series of experiments was carried out to validate the proposed approach. Specifically, the road network data for New Zealand and Hong Kong at different scales (ranging from 1:50,000 to 1:250,000) were used as the experimental data, and subdivided according to different modes (i.e. administrative boundary data, a regular grid of different sizes, different update years, and different road network patterns). Not only geometric parameters, but also structural and hybrid parameters of existing selective omission approaches were involved in the testing. The experimental results show that although the most appropriate thresholds obtained from different subdivisions are not always the same, in most cases, the appropriate threshold ranges often overlap, especially for geometric parameters, and they also overlap with those obtained from the large road network data. This finding is consistent with the use of different subdivision modes, which verifies the effectiveness of the proposed approach. Several issues involving the use of the proposed approach are also addressed.     

How many samples are needed? An investigation of binary logistic regression for selective omission in a road network

ABSTRACT

Selective omission in a road network (or road selection) means to retain more important roads, and it is a necessary operator to transform a road network at a large scale to that at a smaller scale. This study discusses the use of the supervised learning approach to road selection, and investigates how many samples are needed for a good performance of road selection. More precisely, the binary logistic regression is employed and three road network data with different sizes and different target scales are involved for testing. The different percentages and numbers of strokes are randomly chosen for training a logistic regression model, which is further applied into the untrained strokes for validation. The performances of using the different sample sizes are mainly evaluated by an error rate estimate. Significance tests are also employed to investigate whether the use of different sample sizes shows statistically significant differences. The experimental results show that in most cases, the error rate estimate is around 0.1–0.2; more importantly, only a small number (e.g., 50–100) of training samples is needed, which indicates the usability of binary logistic regression for road selection.     

黄河宁蒙段河道粗细双组分泥沙分选沉积特征

黄河宁蒙段河道淤积严重,阐明近源粗泥沙和远源细泥沙分选沉积规律对于河道淤积治理有重要意义。本研究基于120根河道钻孔泥沙样品,通过粒径分布和元素矿物组成,分析了河道>0.05 mm、>0.08 mm和>0.1 mm粗泥沙沿河分选沉积变化特征,并定量评估了近源粗泥沙和远源细泥沙沉积对于河道泥沙淤积的贡献。结果表明：黄河宁蒙段河道淤积的主要是来源于近源沙漠及其下伏砒砂岩区>0.08 mm的粗泥沙,而来源于上游黄土区<0.05 mm的细泥沙主要沉积在河道滩地,对河道淤积的贡献小于30%。因此,风水复合侵蚀引起的沿黄沙漠和下伏砒砂岩粗泥沙入黄是黄河宁蒙沙漠河段河道淤积的根源,也是该河段“悬河”的治理重点。