Interactions Between Environmental Selenium and Sulphoxy Radicals

Chemical interactions between sulphoxy radical anions and elemental Se were investigated to show the influence of SO₂ pollution on the atmospheric fate of selenium. Laboratory experiments were performed with elemental Se plates or fine powder exposed to sulphoxy radicals formed in situ during the autoxidation of SO₂ dissolved in water. Impacts of the radicals were followed examining the topographic surface changes of Se (atomic force microscopy, AFM) and measuring the S(IV) autoxidation rate, essentially decreased in the presence of Se (conductometry). The experiments showed that remobilization of water insoluble selenium (elemental Se) may take place not only in atmosphere (cloud waters), but also in surface waters, soil and sediments contacting with SO₂ polluted air. By scavenging radicals, selenium causes the retardation of the S(IV) autoxidation to sulphuric acid (acid rain), thus contributing to long-distance transport of unreacted S(IV). The more general problem of sulphoxy radical-induced atmospheric corrosion has been brought forward into consideration, as the radicals appear capable to damage diverse solid surfaces.     

矿物热膨胀的晶体化学研究综述

热膨胀是矿物材料的重要属性之一,对它的研究在矿物学及材料科学中具有重要意义。前人关于矿物的热膨胀系数和晶体化学参数之间关系的研究表明,矿物的 结构、成分、化学键及原子价态、配位数、外层电子结构等对热膨胀系数都有不同程度的影响。晶体化学方法是研究矿物热膨胀系数的有效方法,但由 于矿物的热膨胀系数和晶体化学参数之间的定量关系尚未完全弄清,目前仅仅能对简单结构矿物的热膨胀系数进行计算,结构、成分较复杂的矿物的热膨胀系数计算尚缺乏好的晶体化学模型。为达到精确计算矿物热膨胀系数的目的,必须对矿物按照晶体化学特性进行分类。 在分类的基础上,把晶体化学方法和理论计算方法有效地结合起来。矿物的热膨胀性可按照 受热时结构有无旋转划分为键膨胀型和结构旋转型,过渡金属阳离子所形成的化合物根据d电子层电子云的分布进行分类。通过以上的分类,在计算不同类型矿物热膨胀系数时 ,可按矿物类型处理。对键膨胀型的矿物只需估计键的膨胀情况,而对于结构旋转型除考虑 键的膨胀性以外还要考虑配位多面体旋转的情况。     

Accretion and tectonic erosion processes revealed by the mode of occurrence and geochemistry of greenstones in the Cretaceous accretionary complexes of the Idonnappu Zone, southern central Hokkaido, Japan

The Cretaceous accretionary complexes of the Idonnappu Zone in the Urakawa area are divided into five lithological units, four of which contain greenstone bodies. The Lower Cretaceous Naizawa Complex consists of two lithologic units. The Basaltic Unit (B‐Unit) is a large‐scale tectonic slab of greenstone, consisting of depleted tholeiite similar to that of the Lower Sorachi Ophiolite (basal forearc basin ophiolite) in the Sorachi‐Yezo Belt. The Mixed Unit of Naizawa Complex (MN‐Unit) contains oceanic island‐type alkaline greenstones which occur as slab‐like bodies and faulted blocks with tectonically dismembered trench‐fill sediments. Repeated alternations of the two units in the Naizawa Complex may have been formed by the collision of seamounts with forearc ophiolitic body (Lower Sorachi Ophiolite) in the trench. The Upper Cretaceous Horobetsugawa Complex structurally underlies the Naizawa Complex in its original configuration, and it also contains greenstone bodies. Greenstones in the MH‐Unit occur as blocks and sedimentary clasts in a clastic matrix, and exhibit depleted tholeiite and oceanic‐island alkaline basalt/tholeiite chemistry. This unit is interpreted as submarine slide and debris flow deposits. Greenstones in the PT‐Unit occur at the base of several chert‐clastic successions. Most of the greenstones are severely sheared and show normal‐type mid‐ocean ridge basalt composition. The PT‐Unit greenstones are considered to have been derived from abyssal basement peeled off during accretion. The different accretion mechanism of the greenstones in the Naizawa and Horobetsugawa complexes reflects temporal changes in subduction zone conditions. Seamount accretion and tectonic erosion were dominant in the Early Cretaceous, due to highly oblique subduction of the old oceanic crust and minimal sediment supply. Whereas, thick sediments with minor mid‐ocean ridge basalt and olistostrome accreted in the Late Cretaceous, due to near‐orthogonal subduction of young oceanic crust with voluminous sediment supply.     

Geochemical changes at the Bagni di Triponzo thermal spring during the Umbria-Marche 1997–1998 seismic sequence

After the earthquakes of September 26, 1997, that hit the Umbria-Marcheboundary (Apennine, Central Italy), with a maximum 6.0 M_w, aprogram of geochemical surveying together with a collection ofhydrogeological changes episodes was extended throughout theepicentre-area, taking the yearly period of the seismic sequence as a whole.After a first areal screening, the Bagni di Triponzo thermal spring wasselected for a discrete temporal monitoring (weekly and monthly basis),being the unique thermal spring throughout the epicentre area. This sitedeserves peculiar interest in deepening the knowledge about deep fluidscirculation changing during seismicity.Laboratory and on-field analyses included major, minor and trace elementsas well as dissolved gases (He, Ar, CH₄, CO₂, H₂S,²²²Rn, NH₄, As, Li, Fe, B, etc...) and selected isotopic ratios(C, H, O, He, Sr, Cl), meaningful from tectonic point of view.The chemistry and isotopic chemistry of the spring were fully outlined anddiscussed, pointing out the main process involving the thermal aquifer: thewater-rock interaction inside the Evaporite Triassic Basement (ETB),possibly involving also the Paleozoic Crystalline Basement. On theother hand, sudden and apparent geochemical and hydrogeologicalvariations during the seismic sequence ruled out an evolution in thewater-rock interaction processes. They occurred both at depth, i.e.,induced by fluid remobilization within the crust explained by the Coseismic Strain Model and by the Fault Valve Activity Model, and in the shallow part of the reservoir (i.e., meteoric watercontamination). A statistical multivariable analysis (Factor Analysis) wasaccomplished to better constrain the correlation between the paroxysmalphases of the seismic sequence and the observed trends and spike-likeanomalies. The groundwater variations was inferred to occur mainly insidethe ETB, from depth (1–2 km) up to surface, particularly in associationof the Sellano earthquake (14/10/1997) and of the seismic re-activationof the sequence at the end of March 1998 (Gualdo Tadino-Rigali andVerchiano areas). The lack of deeper input from below the ETB (slightsignature of PCB), as the lack of He mantle signature, during the seismicperiod as a whole, accounted for seismogenic fault segments rooted onlyin the crust. The results also provide useful information about theearthquake-related response mechanisms occurring at this site, thatrepresent the basic task for planning and managing the impendinghydro-geochemical network aimed at defining the relationships betweenseismic cycle, fluids and reliable earthquake forerunners.     

A modelling study of tropospheric distributions of the trace gases CFCl3 and CH3CCl3 in the 1980s

Interhemispheric transport is a key process affecting the accuracy of source quantification for species such as methane by inverse modelling, and is a source of difference among global three-dimensional chemistry transport models (CTMs). Here we use long-term observations of the atmospheric concentration of long-lived species such as CH₃CCl₃ and CFCl₃ for testing three-dimensional chemistry transport models (CTMs); notably their ability to model the interhemispheric transport, distribution, trend, and variability of trace gases in the troposphere. The very striking contrast between the inhomogeneous source distribution and the nearly homogeneous trend, observed in the global ALE/GAGE experiments for both CH₃CCl₃ and CFCl₃ illustrates an efficient interhemispheric transport of atmospherically long-lived chemical species. Analysis of the modelling data at two tropical stations, Barbados (13°N, 59°W) and Samoa (14°S, 124°W), show the close relationship between inter-hemispheric transport and cross-equator Hadley circulations. We found that cross-equator Hadley circulations play a key role in producing the globally homogeneous observed trends. Chemically, the most rapid interaction between CH₃CCl₃ and OH occurs in the northern summer troposphere; while the most rapid photolysis of CH₃CCl₃ and CFCl₃, and the chemical reactions between CFCl₃ and O(¹D), take place in the southern summer stratosphere. Therefore, the cross-equator Hadley circulation plays a key role which regulates the southward flux of chemical species. The regulation by the Hadley circulations hence determines the amount of air to be processed by OH, O(¹D), and ultraviolet photolysis, in both hemispheres. In summary, the dynamic regulation of the Hadley circulations, and the chemical processing (which crucially depends on the concentration of OH, O(¹D), and on the intensity of solar insolation) of the air contribute to the seasonal variability and homogeneous growth rate of observed CH₃CCl₃ and CFCl₃.     

我国矿物晶体结构与晶体化学研究进展及新成果(2000-2019)

矿物的晶体结构与晶体化学是矿物学的重要基础研究领域之一,21世纪以来,随着国家对地勘行业的重视,以及平面探测技术单晶衍射仪、微区、微量衍射等实验技术的应用与计算机软硬件能力的提高,我国矿物晶体结构与晶体化学研究得到飞速发展.矿物晶体结构测定与研究是伴随着新矿物的发现而发展的,新矿物的发现是矿物晶体结构研究的基石,又为新...     

基于PSR模型的珠江口海域富营养化特征与评价

本研究依据2020年4月(春季)和2020年10月(秋季)珠江口海域的调查数据,根据“压力-状态-响应”(PSR)模型对珠江口海域进行富营养化状况评价,并通过主成分分析以及相关性分析来说明各环境因子对珠江口富营养化的影响。结果表明：在“优、良、中、差、劣”5个富营养化等级中,珠江口PSR综合评价等级为“差”等级,近几年内变化趋于稳定。有机污染物与营养盐对珠江口富营养化的影响较大,其次为叶绿素a和溶解氧。珠江口营养盐与盐度呈显著负相关,与叶绿素a呈显著正相关。周边城市的陆源排放输入是导致珠江口富营养化的主要因素,河口稀释混合作用以及浮游植物对珠江口的富营养化程度有影响。     

闽江口海域氮磷营养盐含量的变化及富营养化特征

根据2007—2008年眷、夏、秋、冬8个航次的调查数据,对闽江口海域N、P营养盐分布状况与富营养化特征进行了研究．其结果表明,受闽江冲淡水影响,海水中的N、P营养盐含量的平面分布呈现近岸高而向外逐渐降低的趋势．在N、P营养盐中,PO4-P含量呈现较为明显的季节性变化,而DIN含量的季节性变化规律却不明显．在春、夏、秋、冬四季中NO3-N／DIN含量的比值分别高达79．60％、79．13％、90．54％、96．14％,主导该海域DIN含量的平面分布和污染程度．闽江口海域海水中DIN、PO4-P含量呈不同程度的超标状态,富营养化指数为0．17—41．73,N／P原子比均值为41．14,远远偏离Redfield值（16：1）,具有磷限制潜在性富营养化特征．     

^129I的海洋放射年代学及其他应用研究进展

应用^129I的海洋学研究可分为3个方面：（1）人工^129I的年代学,利用人工放射性在沉积物岩心中的记录,包括以核试验全球最大沉降年1963年为参考时间和利用切尔诺贝利核电站事故发生的1986年作为参考时间的年代测定．（2）利用宇生^129I的年代学,测年体系主要有地热流体、天然气水合物扣石油地质体系．（3）利用核燃料后处理厂排放的^129I进行的海洋环流与混合研究．核试验和核事故释放的^129I测定的是现代沉积物年代,测年时间尺度为50a．人们提出人类利用原子能之前地球表层初始^129I丰度为1．5×10^-12。,并以该值作为利用宇生^129I估算年代的初始丰度值．半哀期和丰度探测下限水平允许宇生^129I可测年的时间尺度为80Ma．本文综述了以上几方面的研究进展．海洋多金属结核和结壳的生长速率为毫米每兆年量级,一块1～10cm大小的多金属结核和结壳所能涵盖的时间尺度约为10～100Ma,刚好是^129I测年的时间尺度,所以本文提出了多金属结核和结壳可能是合适的^129I测年介质的观点．     

Physicochemical changes in sediments at Orplands Farm,Essex, UK following 8 years of managed realignment

Managed realignment (MR) is a ‘soft’ engineering technique that involves the deliberate landwards retreat of the existing line of coastal defence and subsequent tidal inundation of land. Managed realignment has been established worldwide for over 30 years and its goals may include habitat restoration, recovery of biodiversity and sustainable coastal defence. In southeast England in particular, an increasing number of MR sites (20–110 ha) have been commissioned in the last decade in response to increasing coastal habitat loss and sea-level rise. Following initial sea wall breaching and site flooding, monitoring of these sites is usually carried out for a period of 5 years and during this time changes in ecosystem structure can be easily observed. However, there is a poor understanding of the long-term effects of flooding on soil physicochemical parameters including sediment geochemistry and geochemical cycling, nutrient fluxes and soil maturation processes. Such physical and chemical changes may continue to take place over time-scales exceeding 5 years and therefore current monitoring practices may not be sufficient.