铁炉坪银铅矿床银赋存状态及其选矿工艺探讨

采用人工重砂、光薄片、Ｘ粉晶衍射、扫描电镜及电子探针等综合方法，查明铁炉坪银铅矿床中的独立银矿物有银黝铜矿、自然银、辉银矿、硫铜银矿、硫锑银矿、硫锑铜银矿和溴氯角银矿等７种。在原生矿石中，银黝铜矿为主要银矿物，并以包裹体形式分布在方铅矿之中；在氧化矿石中，辉银矿、自然银、溴氯角银矿等均占一定比例。矿石中的银主要赋存在独立银矿物之中。银矿物粒度细小，形态复杂，选矿时宜采用浮选法或浮选—重选联合流程。对氧化矿石也可采用先硫化、然后浮选的流程     

太平洋结核结壳中的锶铅同位素关系研究

依据多金属结核、铁锰结壳的记录 ,研究了太平洋海水结核结壳中锶、铅同位素的关系 ,结果表明 ,太平洋海水中锶同位素与铅同位素无明显的相关性。作者认为这是由于太平洋海水中锶、铅的滞留时间相差很大 ,达 4个数量级 ,锶同位素记录了 10 0 0 0 0 a至百万年时间尺度上全球性大洋范围内海水物质来源的变化 ,而铅同位素能在较小的时间尺度上反映局部的大洋海水物质来源的信号 ,是高分辨率的物源示踪剂     

Application of a stochastic model to estimate children’s short-term residential exposure to lead

The Cumulative and Aggregate Simulation of Exposure (CASE) framework is an innovative simulation tool for exploring non-dietary exposures to environmental contaminants. Built upon the Dermal Exposure Reduction Model (DERM) and established methods for collecting detailed human activity patterns, the CASE framework improves upon its predecessor. Although prompted in part by the Food Quality Protection Act of 1996 and the need to assess aggregate exposure to pesticides, the framework was designed to be flexible enough to assess exposure to other contaminants. This paper examines features of the CASE framework in an illustrative application estimating children’s dermal and non-dietary ingestion exposure to lead in the residential environment. Concentration values in various media are taken from a nationwide study and exposure factors are obtained from the literature. Activity pattern input includes sequential micro-level activities collected for 20 children (ages 1 through 6). Modeled results are explored via classification trees and sensitivity analysis. Results of each exposure route are also compared to independent data. Median dermal exposure estimates were 589 and 558 μg/m³ for the right and left hands, respectively, with the resulting output most sensitive to exposure factor terms. The simulation estimated a median non-dietary ingestion rate of 9.5 μg of lead per day with estimates most sensitive to the surface area of mouthed objects.     

厦门西港表层沉积物对铅的吸附作用

在海水介质中,模拟研究了厦门西港沉积物对Pb吸附过程的热力学和动力学性质,提出相应的定量模式,测定饱和吸附量、吸附速率常数和表观活化能等重要物化参数。结果表明,沉积物-Pb的吸附以化学作用为主,静电作用为辅。其吸附性质与水合氧化铁-Pb的吸附类似。     

Sensitivity of open-water ice growth and ice concentration evolution in a coupled atmosphere-ocean-sea ice model

A coupled atmosphere-ocean-sea ice model is applied to investigate to what degree the area-thickness distribution of new ice formed in open water affects the ice and ocean properties. Two sensitivity experiments are performed which modify the horizontal-to-vertical aspect ratio of open-water ice growth. The resulting changes in the Arctic sea-ice concentration strongly affect the surface albedo, the ocean heat release to the atmosphere, and the sea-ice production. The changes are further amplified through a positive feedback mechanism among the Arctic sea ice, the Atlantic Meridional Overturning Circulation (AMOC), and the surface air temperature in the Arctic, as the Fram Strait sea ice import influences the freshwater budget in the North Atlantic Ocean. Anomalies in sea-ice transport lead to changes in sea surface properties of the North Atlantic and the strength of AMOC. For the Southern Ocean, the most pronounced change is a warming along the Antarctic Circumpolar Current (ACC), owing to the interhemispheric bipolar seasaw linked to AMOC weakening. Another insight of this study lies on the improvement of our climate model. The ocean component FESOM is a newly developed ocean-sea ice model with an unstructured mesh and multi-resolution. We find that the subpolar sea-ice boundary in the Northern Hemisphere can be improved by tuning the process of open-water ice growth, which strongly influences the sea ice concentration in the marginal ice zone, the North Atlantic circulation, salinity and Arctic sea ice volume. Since the distribution of new ice on open water relies on many uncertain parameters and the knowledge of the detailed processes is currently too crude, it is a challenge to implement the processes realistically into models. Based on our sensitivity experiments, we conclude a pronounced uncertainty related to open-water sea ice growth which could significantly affect the climate system sensitivity.     

Green Electronics through Legislation and Lead Free Soldering

Management of used electrical and electronic equipment (EEE) is becoming a major issue as each year around 20 to 50 million tonnes of electronic waste (e‐waste) is generated worldwide. EEE contains over 1000 materials of which lead (Pb) has been one of the targets of the regulators forcing manufacturers to adopt lead free products. Industry has come up with several lead free solders with preference given to alloys containing tin, silver, and copper but there is no ,drop‐in' substitute to leaded solder. Issues with lead free solders such as temperature, intermetallics, tin whisker, tin pest, and reliability are yet to be resolved. The paper investigated the contribution of lead free soldering to green electronics in a holistic way. Global lead free movement has reached a point of no return. However, it is necessary to make sure that life span of EEE is not shortened thereby resulting in an unforeseen increase in e‐waste or problem shifting does not occur by shifting a problem from one life cycle to another or from one category/media to another.     

Lateral force distributions for the linear static analysis of base-isolated buildings

This paper presents a new approach for the evaluation of accurate lateral force distributions for the Linear Static Analysis (LSA) of Base Isolated (BI-) buildings. In essence, the proposed lateral force distributions depend on a factor measuring the degree of non- linearity of the Isolation System (IS) and on the ratio between the effective period of the BI-structure (T_is) and the fundamental period of the Fixed Based (FB-) structure (T_fb). The proposed approach is fully compatible with the Direct Displacement-Based Design (DDBD) method, recently developed by Priestley and co-workers. The proposed lateral force distributions have been derived from the results of a large number of Nonlinear Time-History Analyses (NTHA), carried out on six numerical models of multi-storey buildings, differing in storey number (3, 5 and 8, respectively) and fundamental period of vibration (from 0.25 to 0.8 s) in the fixed-base configuration. A great variety of Isolation Systems (ISs), characterised by either Elasto-Plastic with Hardening (EPH) or Flag-Shaped (FS) force-displacement behaviour, have been considered in the NTHA. The numerical parameters of the IS models have been varied in such a way as to reproduce the actual mechanical behaviour of the main currently used ISs, including: (i) Lead Rubber Bearings (LRB), (ii) High-Damping Rubber Bearings (HDRB), (iii) Friction Pendulum Bearings (FPB), (iv) combinations of flat Sliding Bearings (SB) and Low-Damping Rubber Bearings (LDRB) and (v) Combinations of flat SB and re-centring devices based on Shape Memory Alloys (SMA). Comparisons between the storey shear forces derived with the proposed method and those obtained from NTHA clearly show the great improvements in the accuracy of LSA predictions, when using the proposed lateral force distributions.     

Event chronostratigraphy: A high-resolution tool for dating the recent past

The most recent part of the geological timescale presents us with some of the greatest challenges for dating. With the exception of ²³⁰Th/²³⁴U methods, whose use is restricted to rather specific depositional environments, there is no established geochronometric tool capable of dating more than a fraction of the recent past at a resolution adequate to tackle the environmental issues of this period. Event stratigraphy, the investigation of comparatively rare and abrupt occurrences that leave some trace in the stratigraphic record, has been widely employed as a means of correlation and dating of older geological strata. Yet this approach has frequently been overlooked in efforts to establish chronologies of the recent past. It is ironic, therefore, that because of the acceleration of human activity, stratigraphic events have almost certainly occurred with greater frequency over the last few centuries than at any preceding time in Earth history. Because the history of human-induced events is usually well-established, the markers of such events have immense chronostratigraphic value. They may be employed in circumstances in which radiometric techniques may not be suitable, and may offer higher-resolution dates than those associated with conventional dating methods. Dated event horizons may also provide the essential means by which to validate geochronometric analyses of the recent past.Event markers may be divided into those that produce discontinuities in the rock record and those (of much greater value in the terrestrial deposits that are the focus of most investigations of the recent past) that leave some tangible signal in the rocks. These signals may be the result of either natural factors or human-induced processes, and may occur in a range of temporal contexts. They may mark the instant of occurrence of a short-lived phenomenon, or they may represent the abrupt disappearance or sudden appearance of some feature. This paper reviews each of these markers, focussing specifically on their application to the chronology of the recent past and the global environmental transformation that has taken place during this time.     

Adsorption studies of aqueous Pb(II) onto a sugarcane bagasse/multi-walled carbon nanotube composite

Adsorption of Pb²⁺ from aqueous solution onto a sugarcane bagasse/multi-walled carbon nanotube (MWCNT) composite was investigated by using a series of batch adsorption experiments and compared with the metal uptake ability of sugarcane bagasse. The efficiency of the adsorption processes was studied experimentally at various pH values, contact times, adsorbent masses, temperatures and initial Pb²⁺ concentrations. A pH of 4.5 was found to be the optimum pH to obtain a maximum adsorption percentage in 120 min of equilibration time. The composite showed a much enhanced adsorption capacity for Pb²⁺ of 56.6 mg g⁻¹ compared with 23.8 mg g⁻¹ for bagasse at 28 °C. The Langmuir adsorption isotherm provided the best fit to the equilibrium adsorption data. The pseudo first-order, pseudo second-order, intraparticle diffusion and Elovich kinetics models were used to analyse the rate of lead adsorption and the results show that the Elovich model is more suitable. The thermodynamic parameters of adsorption, namely ΔG°, ΔH° and ΔS°, were determined over the temperature range of 20–45 °C. The adsorption of Pb²⁺ onto both bagasse and the sugarcane bagasse/MWCNT composite was found to be spontaneous but for the former adsorbent it was enthalpy-driven whereas for the latter it was entropy-driven. Desorption of the lead-loaded adsorbents was fairly efficient with 0.1 mol dm⁻³ HCl. Overall this composite has the potential to be a good adsorbent for the removal of Pb²⁺ from wastewaters.     

210Pb in the ocean: A pilot tracer for modeling particle reactive elements

We discuss the basic requirements for a successful modeling of²¹⁰Pb in the ocean as a test tracer for at least other lead isotopes, but also of other elements that behave similarly to lead. With the aid of realistic models of the oceanic circulation and the major biogeochemical cycles in it, the result is a dynamically consistent model of lead cycling that reproduces observed profiles within 10%.