Ways of investigating radionuclide migration processes in the lithosphere and hydrosphere

In Russia, until recently, it was considered that groundwater was protected from surface radioactive contamination by soil and rocks in the zone aeration. Groundwater was not a subject of radiation control. The accident at the Chernobyl Nuclear Power Plant showed, however, that groundwater is vulnerable to radioactive contamination. In this connection, the vulnerability of groundwater to and the problems of protecting groundwater from radioactive contamination became urgent. The assessment of natural protection of groundwater from radioactive contamination is now considered a top priority. The zone of aeration is generally considered to be the zone separating groundwater from surface contamination. In respect to radioactive contamination, soils that may fix a large quantity of radionuclides serve as a protection zone of a higher order. The mapping of protectibility was done for each radionuclide taking into consideration the specific structure of the flow medium and migration properties of a radionuclide.⁹⁰Sr and¹³⁷Cs have different mechanisms of transport; convective transport is characteristic of the former and diffusive transfer of the latter. This is conditioned by different physico-chemical properties of the radionuclides and principally by their sorption capacities. The coefficient of distribution of⁹⁰Sr is in many times less than the coefficient of distribution of¹³⁷Cs. The environmental protection problem in regions with nuclear power plants and in areas subjected to radioactive contamination may be solved using a monitoring, system including interrelated systems of observation and prediction of the lithosphere and the hydrosphere. The problem of mathematical modeling of migration processes is related to the complexities of modeling the processes of flow, mass transfer, and the accompanying physicochemical processes in zones of full and partial saturation, as well as difficulties in mathematical calculations.     

现代海底热液区重晶石的地球化学特征及其影响因素

重晶石是海底热液活动产物之一,其化学元素及Sr、S、O同位素组成可以有效地揭示热液流体的演化过程。本文通过分析研究全球23个热液区中重晶石的化学元素和Sr、S、O同位素组成,探讨了热液区重晶石的元素富集特征,以及沉积物、岩浆、微生物对重晶石的影响因素。结果表明：高温比低温使Sr更容易进入重晶石晶格,重晶石晶型和元素组成特征指示了不同的成矿条件;板状重晶石具有较高的SrO/BaO比值,反映了较高温的成矿条件;柱状重晶石具有较低的SrO/BaO比值,反映了较低温的成矿条件。研究推测Ca类质同象替代Ba的程度可能也受温度的影响。重晶石中的⁸⁷Sr/⁸⁶Sr、δ³⁴S、δ¹⁸O值变化范围较大,分别为0.703 73~0.717 49、3.7‰~36.1‰、3.3‰~18.8‰,表明不同热液区成矿流体受沉积物、岩浆作用、微生物作用等多种因素的影响。受沉积物来源影响的Sr、S使重晶石的⁸⁷Sr/⁸⁶Sr值及δ³⁴S值偏高,温度和热液—沉积物反应程度是主要控制因素;受岩浆来源的SO₂的歧化作用和后期H₂S的氧化作用影响重晶石的δ³⁴S值,扩张中心的演化程度是岩浆影响重晶石δ³⁴S值的主要控制因素;微生物还原作用伴随着S、O同位素分馏,直接影响重晶石的δ³⁴S和δ¹⁸O值,沉积环境条件和初级生产力是主要控制因素。

     

Analysis of seepage from a pond

A semi-analytical solution has been derived for predicting the time of emptying a pond due to seepage. The time for the seeping water to reach the water table since the pond was initially filled has been calculated applying the Green-Ampt infiltration theory. The recharge rate after the wetting front joins the water table has been computed using a non-linear relationship between seepage head and recharge rate proposed by earlier investigators. The maximum rise in the water table beneath the center of the pond consequent to the time-varying recharge is calculated applying kernel coefficients obtained from solution of the linearized Boussinesq equation. It was observed that a pond with 50-m initial diameter at the water surface and 3-m maximum depth of water is dry after 168 days, where the subsoil is sandy clay. If the subsoil happens to be clay, the depth of water in the pond at the end of 9 months, i.e., after completion of the non-monsoon period, is 0.62 m. The maximum mound heights beneath the pond for constant recharge rate and uniform recharging area calculated from the present solution compare well with existing numerical as well as analytical solutions.     

Upper-mantle structure and nature of deep processes in island arcs and trench systems

Upper-mantle structure and heat flow and gravity data are considered. It is shown that crustal isostasy disturbance is compensated for by inhomogeneities in the density of the upper mantle; compaction beneath trenches and discompaction under island arcs. On the basis of the available data an upper-mantle density model is constructed which is represented by a seismoactive layer with a surplus density of from 0.05 to 0.1 g/cm³ and a discompacted zone overlying that layer with a density deficiency of 0.05 g/cm³ beneath the island arc and 0.01 g/cm³ in the remaining area. The available data are in poor agreement with the concept of “new global tectonics”, therefore the formation of density inhomogeneities is associated with gravity differentiation of the mantle material. A scheme of this process is proposed according to which heated differentiates of the mantle material rise along deep faults or weakened zones from depths of 700 km and more. Upper-mantle material differentiation occurs mainly in several levels, but mostly at depths down to 150–200 km within the interval of 350–450 km. Separation of heavy components as a result of differentiation and the “zone melting process” causes a high velocity and correspondingly a denser inclined layer. Discompaction of the upper mantle overlying the focal plane is associated with its being heated by high-temperature melts circulating over the inclined fault.     

Geochemical controls on sediment reactivity and buffering processes in a heterogeneous aquifer

The injection and recovery of oxic water into deep anoxic aquifers may help to alleviate short- and long-term imbalance between freshwater supply and demand. The extent and structure of physical and geochemical heterogeneity of the aquifer will impact the water quality evolution during injection, storage and recovery. Water–sediment interactions within the most permeable parts of the aquifer, where the bulk of the injectant will penetrate, may dominate, however, water quality may also be impacted by interactions within the finer-grained, less permeable but potentially highly reactive media. In this study, the heterogeneity of the reductive capacity of an aquifer selected for water reuse projects was characterised, the amount, type and reactivity of the sedimentary reductants present determined, and the relationship between reductive capacity and sedimentary lithologies quantified. The average potential reductive capacities (PRC_TOT), based on total organic C and pyrite concentrations of the sediment, were quantified for sands (382 μmol O₂ g⁻¹), clays (1522 μmol O₂ g⁻¹), and silts (1957 μmol O₂ g⁻¹). Twenty-seven samples, spanning the three different lithologies, were then incubated for 50 days and the measured reductive capacities (MRC) determined for the sands (29.2 μmol O₂ g⁻¹), silts (136 μmol O₂ g⁻¹), and clays (143 μmol O₂ g⁻¹). On average, the MRC were 10% of the PRC_TOT. The main consumers of O₂ were pyrite (20–100%), sedimentary organic matter (SOM; 3–56%), siderite (3–28%) and Fe(II)-aluminosilicates (8–55%). The incubation data plus hydrogeochemical modelling, indicated that pH-buffering was controlled firstly by dissolution of trace level carbonates, followed by dissolution of feldspars. Zinc, Co, Ni, Cd and Pb were readily mobilized during incubation.     

Geochemical characteristics affecting the cultivation and quality of Longjing Tea

Geochemical environment, landscape and climate conditions are important factors affecting the distribution and quality of agricultural products. Methods and techniques of exploration geochemistry were applied to study geochemical rock and soil characteristics which affect the cultivation and quality of world famous Longjing Tea. The study shows that soil type and its total and bioavailable element content directly affect the quality of Longjing Tea. Geochemical factors can be used in recommending the siting of Longjing Tea plantations to obtain high quality tea, and to assist in tea-garden management.     

Climate change,environmental degradation and migration

Climate change will have a progressively increasing impact on environmental degradation and environmentally dependent socio-economic systems with potential to cause substantial population displacement. The key concerns in Less Developed Countries (LDCs) will include serious threats to food security and health, considerable economic decline, inundation of coastal areas, and degradation of land and fresh water resources (Reuveny in Polit Geogr, 2007). The relationship between environmental change and potential humanitarian crises has been captured by: McGregor (Geography and refugees: patterns and processes of change, Belhaven Press, London, pp 159–70, 1993), Kibreab (Environment and Population Change, International Union for the Scientific Study of Population, Liège, 1994), Kibreab (Disasters 21(1):20–38, 1997), Myers (Bioscience 43:752–761, 1993), Myers and Kent (Environmental exodus: an emergent crisis in the global arena, Climate Institute, Washington, DC, 1995), Black (New Issues in Refugee Research, Working Paper no. 34, 2001), Lee (Environmental matters: conflict, refugees and international relations, World Human Development Institute Press, Seoul and Tokyo, 2001), Castles (Environmental Change and Induced Migration: Making Sense of the Debate Working Paper No. 70, 2002), Christian Aid (Human tide: the real migration crisis, Christian Aid, London, 2007), and Massey et al. (, 2007). However, we know little about the interplay between environmental change and stresses on ecological systems, resulting socio-economic vulnerability and potential outcomes in terms of population displacement or induced migration. So far these relationships are poorly conceptualized, lack systematic investigation, and are reduced to simplistic causal explanations. This leads to misleading conclusions that deny the complex multivariate processes—environmental, political, social, and economic— which are the root causes of environmentally induced migration and/or conflict. When people are faced with severe environmental degradation they have one of three options: (1) stay and adapt to mitigate the effects; (2) stay, do nothing and accept a lower quality of life; or (3) leave the affected area. The process of movement and migration is usually subject to a complex set of push and pull forces, where push forces relate to the source area while pull factors relate to the destination. These forces are in constant flux, as much as environmental change, and interact with socio-economic and political conditions including state or government decision making powers, which can tip the balance at any point by either denying movement or the right to settle elsewhere. The paper focuses on how environmental change and environmental hazards contribute to the migration by exploring the mechanisms through which vulnerability and migration are linked—via livelihoods, relocation policies, and other factors. The paper begins by outlining important definitions of what is environmentally induced migration. The paper also considers the question of whether migration is a process that reduces or increases vulnerability. The paper draws on multidisciplinary literature including ecology, environment, and climate change; sociology of migration; anthropology of displacement; and economics; but also on preliminary from various case studies in Egypt, Vietnam, and Mozambique.     

填埋场中气体运移的非稳定耦合渗流数学模型

基于多孔介质渗流力学和流固耦合理论，建立了填埋场内挥发性气体在土壤中迁移气－固耦合数学模型，并根据数学模型的非线性特征，采用摄动法求出模型的拟解析解。通过解析求解研究了挥发性气体在土壤中耦合与非耦合渗流情况下孔隙压力分布动态特征，为预测和预报挥发性气体在土壤中的扩散状况，以及对环境污染的治理，控制污染的扩散理论了理论依据。     

Study of two alteration systems as natural analogues for radionuclide release and migration

U-deposit hosted in hydrothermally altered tuffs in Mexico, together with weathering profiles from Cameroon were studied as natural analogues of radionuclide release and migration. Using petrological and spectroscopic methods (infrared and electron paramagnetic resonance), we have distinguished successive secondary mineral parageneses and the behaviour of radionuclides.

In the U-deposit, the mineral parageneses show that uranium migration is mainly controlled by the redox potential and silica activity of the altering solutions. The high silica content of the solutions is caused by the intense alteration of volcanic rocks. Two types of secondary clay mineral parageneses are evidenced: a kaolinization, intense where uranium is accumulated in the welded tuffs, and a smectitization mainly developed in the underlying weakly welded tuffs.

Several types of kaolinite have been defined according to their genesis (fillings in fissures and feldspar pseudomorphs), their location relative to a breccia pipe where uranium has accumulated (core and rim of the pipe; surrounding rhyolitic tuffs), and particle morphology, structural order and substitutional Fecontent. It is shown that the variations of the concentration of paramagnetic defect centres, always more than ten times as important than those measured in weathering kaolinites, are only correlated to the location of the kaolinites. The highest values correspond to the breccia pipe kaolinites, e.g. kaolinites located in the uranium accumulation zones. Moreover, one or two main defects centres are detected depending on the intimate association of kaolinites with uranium-bearing minerals. Besides, in weathering kaolinites from U-depleted laterites, defect centre concentrations are correlated to the total Fe203 content in bulk samples. This means that the defect centre acts as a memory of the travel of uranium when this element was sorbed onto iron gels in the first stage of weathering.

It is concluded that paramagnetic defect centres in kaolinites might allow an efficient fingerprint of successive irradiations in the natural analogues under study and could be an useful tool to control radionuclides migration through kaolinite-containing clayey materials such as those used for waste repository.

A better understanding of radiation efficiency as well as accurate dose-ratekaolinite-containing clayey materials such as those used for waste reposit estimation are needed for a quantitative tracing of the migration ofA better understanding of radiation efficiency as well as accurate dose-ratekaolin radionuclide elements. With this aim, a simulation has been undertaken withestimation are needed for a quantitative tracing of the migration of various radiations sources. We have determined for each irradiation the parameters of the paramagnetic centres created in order to understand the way they are forming. The knowledge of the parameters governing the formation and the stability of the radiation centres in kaolinites allow to use this mineral as a natural dosimeter.     

Geochemical processes controlling fluoride-bearing groundwater in the granitic aquifer of a semi-arid region

The aim of the present study is to identify the geochemical processes responsible for higher fluoride (F^–) content in the groundwater of the Yellareddigudem watershed located in Nalgonda district, Andhra Pradesh. The basement rocks in the study area comprise mainly of granites (pink and grey varieties), which contain F-bearing minerals (fluorite, biotite and hornblende). The results of the study area suggest that the groundwater is characterized by Na⁺: HCO facies. The F^– content varies from 0.42 to 7.50 mg/L. In about 68% of the collected groundwater samples, the concentration of F^– exceeds the national drinking water quality limit of 1.5 mg/L. The weathering of the granitic rocks causes the release of Na⁺ and HCO ions, which increase the solubility of ions. Ion exchange between Na+ and Ca²⁺, and precipitation of CaCO₃ reduce the activity of Ca²⁺. This favours dissolution of CaF₂ from the F-bearing minerals present in the host rocks, leading to a higher concentration of F^– in the groundwater. The study further suggests that the spatial variation in the F^– content appears to be caused by difference in the relative occurrence of F-bearing minerals, the degree of rockweathering and fracturing, the residence time of water in the aquifer materials and the associated geochemical processes. The study emphasizes the need for appropriate management measures to mitigate the effect of higher F groundwater on human health.     

Geochemical processes and solute transport at the seawater/freshwater interface of a sandy aquifer

Geochemical processes occurring at a seawater/freshwater interface were studied in a shallow coastal siliclastic aquifer containing minor amounts of calcite. Data were collected from 106 piezometers in a 120-m transect from the coastline and landward. In the first 40 m from the coastline, a wedge of saltwater is intruding below the freshwater aquifer. The aquifer is strongly reduced with mineralization of organic matter by methanogenesis in the freshwater aquifer, and sulfate reduction dominating in the most seaward part of the saline aquifer. The spatial separation of cations in the aquifer indicated a slow freshening process where Ca²⁺ from freshwater displaced the marine cations Na⁺ and Mg²⁺ from the exchanger complex. The resulting loss of Ca²⁺ from solution decreases the saturation state for calcite and possibly causes calcite dissolution. A storm-flooding event was recorded where pulses of dense seawater sank through the fresh aquifer. As a result, the terminal electron accepting process switched from methanogenesis to sulfate reduction. The pulses of sinking seawater also triggered cation exchange reactions where Ca²⁺ was expelled from the exchanger by seawater Na⁺ and Mg²⁺. The released Ca²⁺ is being flushed from the aquifer by groundwater flow, and this export of Ca²⁺ will, in the long term, cause decalcification of the sediment. The water composition in the aquifer is in a transient state as the result of various processes that operate on different timescales. Oxidation of organic matter occurs continuously but at a rate decreasing on a geological time scale. The freshening of the aquifer operates on the timescale of a few years. The episodic flooding and sinking of seawater through the aquifer proceeds in the course of days to weeks, but occurs irregularly with years in between.     

影响四会沙糖桔生长及果实品质的地球化学特征

四会地区是中国重要的沙糖桔产区,重点对威整、地豆和江谷三处沙糖桔园进行了生态地球化学调查,采集了沙糖桔园表层土壤以及沙糖桔叶、果实以及配套根系土样品,实测了营养、有益和有害元素.通过计算沙糖桔各部位元素吸收系数、果实品质与根系土营养元素的相关性,获知影响沙糖桔生长及果实品质的特征元素,它包括常量组分SiO2、Fe2O3、MgO、K2O、CaO、OrgC、Na2O和微量元素S、B、V、Co.最后通过分析特征元素在评价区分布状况,获知种植沙糖桔理想区域为泥盆纪地层分布区.     

济南市土壤元素地球化学特征及环境质量

以济南市土壤为研究对象,采用R-2.6.1程序、半方差函数模型和因子分析法对区内土壤元素含量统计特征、结构特征和分布特征进行了分析研究,并对土壤环境质量进行评价。结果表明:研究区土壤中多数元素含量总体受自然空间格局控制,但人类活动对市区土壤Cd、Hg、Pb、Se、As、p H值等元素(指标)含量有明显影响,表层土壤p H值呈现从外围向市区中心增加的碱化趋势;盛行风向对表层土壤重金属的分布叠加也产生影响,沿顺风向产生漂移。受人类活动(主要为工业污染)历史长短及强度的不同,济南市区、历城区和章丘市总体为轻度污染,局部存在Hg、Cu、Cr、Cd等中度或重度污染,污染区分布与各类工业空间布局相吻合,而长清、济阳土壤环境质量较好,总体属警戒限级。按土壤综合污染指数排序,土壤综合环境质量从优到劣为济阳长清章丘历城市区。     

Chemical processes affecting alkalis and alkaline earths during continental weathering

The alkali and alkaline earth concentrations in the Toorongo Granodiorite weathering profile are controlled by two competing processes; leaching of cations from primary minerals during their degradation to clays; fixation, by exchange and adsorption, of the same cations onto the secondary clay minerals. Degradation and leaching dominate the early weathering stages whereas during the advanced stages, exchange and adsorption onto clays are of most influence.The alkali and alkaline earth compositional changes in the Toorongo Granodiorite weathering profile are typical of changes occurring during weathering of the continents, consequently the following generalizations apply to continental weathering. Ca, Sr and Na are most rapidly and most strongly removed (as dissolved species) during weathering of fresh continental rocks. Although large quantities of Mg are transported to the marine environment as dissolved species, appreciable amounts remain (fixed in secondary clay minerals) at the weathering site to be removed during mass wasting of continental weathering profiles. Large quantities of Rb, Cs and Ba, fixed in continental weathering profiles by exchange and adsorption onto secondary clays, are transported from the continents only during mass wasting of the continents.     

Geochemical and environmental factors controlling exposure to cerium and magnesium in Uganda

The presence of elevated levels of dietary Ce and deficient levels of dietary Mg in southern India have been assigned as potential environmental cofactors in the aetiology of endomyocardial fibrosis. However, environmental exposure to Ce in tropical environments, where EMF is prevalent, is poorly understood because of wide variation in geochemical environments and local dietary habits. This paper describes collaborative studies based in Uganda to define environmental exposure pathways within a region where EMF is endemic, and represents the most common form of infantile heart condition. Data are presented from a survey of major foodstuffs, soils and waters which indicate that the most probable pathway for Ce exposure is from dust and inadvertent carriage of soil. In addition to substantiating observations made in southwestern India, detailed studies of Ugandan soils, dusts and waters indicate that Ce within the Ugandan environment is controlled by the presence of sub-20 μm particles in the soil. These are probably present as secondary rare earth minerals rather than monazite as assumed by workers in India.     

Geochemical Evolution and Environmental Changes of Qinghai—Xizang Plateau Since Late Cenozoic

Long-and short-term climatic curves were preliminarily established based on the comprehensive analysis of geochemical information since the Late Cenozoic in the Qinghai Xizang(Qinghai-Tibet)Plateau.The curves show that the climate in the plateau was alternatively dry-warm and cold-wet during the period of 30-3.4 Ma when the plateau was not uplifted to an enough altitude and the monsoon was not completely formed either,In the period of 3.4-0.73 Ma.the climate fluctuated between dry-cold and wet-warm when the plateau was rapidly uplifted and the Asian monsoon was consequently formed.Since 0.73 Ma.the climate became even drier when the plateau continuously rose.In the Holocene period.the climate alternatively changed with a complex model of being cool-dry,warm-wet and cold-wet.     

Legal and environmental concerns affecting electric utility involvement in cogeneration

The National Energy Act of 1978 included cogeneration as one of the leading strategies to help solve the nation's energy problems. As a result many new regulations have been formulated to encourage the development of industrial cogeneration facilities. These regulations are aimed at reducing oil imports, conserving nonrenewable resources, and preserving air quality. The electric utilities are uncertain whether the regulations will accomplish these goals. They are concerned that the regulations will lead to the proliferation of small industrial cogeneration facilities giving rise to increased air pollution and other adverse environmental impacts. The utilities are also concerned that, because of the way the regulations are written, they will discourage the electric utilities from fully participating in the cogeneration process.