Quantum-mechanical calculation of the vibrational spectrum of beryl (Al4Be6Si12O36) at the Γ point

A quantum-mechanical calculation of the zone-centre phonon spectrum of beryl has been performed, by using an hybrid HF/DFT Hamiltonian (B3LYP). An excellent agreement with the experiment has been obtained, being the difference between the calculated and the experimental vibrational frequencies (Raman, IR-TO and IR-LO) less than 5 cm^?1 on average. In the few cases where a relatively large disagreement between calculated and experimental data is observed, an explanation can be found which attributes the reason of the discrepancies to the experimental data rather than to the calculated ones. The calculation (i) allows the identification, in the experimental spectra, of the peaks corresponding to fundamental modes, overtones, combination bands and leakage; (ii) solves problems of band assignements due to the presence of LO–TO splitting in the IR spectra; (iii) provides the frequencies of silent modes; (iv) permits a full analysis of the atomic motion corresponding to each normal mode.     

Types, Characteristics, and Geodynamic Settings of Mesozoic Epithermal Gold Deposits in Eastern China

Mesozoic epithermal gold deposits in eastern China are divided into calc‐alkaline and alkaline magma‐related gold deposits, and are also grouped as low‐sulfidation, intermediate‐sulfidation and high‐sulfidation types, of which the first two predominate. These gold deposits are distributed in the Tianshan–Yinshan–Great Xing’anling Variscan fold belt of North China craton, Qinling‐Dabie Indo‐Sinian fold belt of Yangtze craton, and South China fold belt or Cathaysian block, from north to south along the eastern China continent. Most of the epithermal gold orebodies are hosted either in volcanic rocks or their related granitoids, and volcanic breccia pipes. These orebodies are mainly associated with adularia–chalcedony–sericite, and alunite–kaolinite–quartz alteration. These orebodies formed in four mineralization pulses at 175, 145–135, 127–115, and 110–94 Ma. The first three pulses correspond to the post‐collision period between the North China and Yangtze cratons, an extension period during late‐stage rotation of the principal compressional stress from N‐S to E‐W, and a dramatic thinning period of the lithosphere, respectively. The last mineralizing pulse was the result of another extension in South China. Although the mineralizing pulses occurred at different times, they all occurred in extensional settings and were accompanied by crust and the mantle interaction.     

Can oyster restoration reverse cultural eutrophication in Chesapeake Bay?

We investigated the hypothesis that effects of cultural eutrophication can be reversed through natural resource restoration via addition of an oyster module to a predictive eutrophication model. We explored the potential effects of native oyster restoration on dissolved oxygen (DO), chlorophyll, light attenuation, and submerged aquatic vegetation (SAV) in eutrophic Chesapeake Bay. A tenfold increase in existing oyster biomass is projected to reduce system-wide summer surface chlorophyll by approximately 1 mg m⁻³, increase summer-average deep-water DO by 0.25 g m⁻³, add 2100 kg C (20%) to summer SAV biomass, and remove 30,000 kg d⁻¹ nitrogen through enhanced denitrification. The influence of osyter restoration on deep extensive pelagic waters is limited. Oyster restoration is recommended as a supplement to nutrient load reduction, not as a substitute.     

安徽宣城矿集区长山铅锌多金属矿床成矿流体特征及成因

长山铅锌多金属矿床位于长江中下游成矿带宣城矿集区东北部,文章在对该矿床开展详细的地质调查和岩相学研究基础上,对代表性矿化蚀变矿物(石英、方解石)开展了流体包裹体测温、激光拉曼光谱和氢、氧、碳稳定同位素分析。长山铅锌多金属矿床矿化蚀变组合从早到晚可以分为矽卡岩-氧化物阶段、早硫化物阶段和晚硫化物阶段。矿物流体包裹体温度和盐度测算显示,长山矿床的成矿流体温度和盐度从矽卡岩-氧化物阶段(315～382℃,w(NaCl)_eq为14.04%～16.24%)→早硫化物阶段(220～347℃,w(NaCl)_eq为4.49%～15.86%)→晚硫化物阶段(163～306℃,w(NaCl)_eq为1.40%～11.10%)逐渐降低。石英和闪锌矿中包裹体的δD和δ¹⁸O值分别为-89.5‰～-67.8‰和-3.2‰～7.62‰,方解石中δ¹³C和δ¹⁸O值分别是-6.8‰～-1‰和10.6‰～17.1‰,同位素特征指示长山矿床的成矿流体为岩浆水与海相碳酸盐中富含有机质流体混合,...     

Petrographic and geochemical characterization of weathered materials developed on BIF from the Mamelles iron ore deposit in the Nyong unit,South-West Cameroon

Acta Geochimica - Iron ore deposits hosted by Precambrian banded iron formation (BIF) are the most important source of mineable iron. In Cameroon, they are located in the southern part of the...     

Dust pollution caused by an extreme Santa Ana wind event

In arid and semiarid regions from the southwestern USA and vast areas of northwestern Mexico, Santa Ana wind events modify the environment with high temperatures, very low humidity, and dust storms representing a recurrent phenomenon that triggers asthma and other respiratory diseases. While research has emphasized Santa Ana wind effects on the USA side, northwestern Mexico has been less investigated. Numerical modeling of a severe dust storm in November 2018, applying the Weather Research and Forecasting model coupled with a chemistry module (WRF-Chem), revealed that erosion, transport, and dust storms extend along the peninsula and the Gulf of California. Santa Ana winds eroded large areas, transported desert conditions to urban zones, causing high dust concentrations and reducing the relative humidity below 10%, deteriorating climatic conditions favorable to wellness. In Tijuana, Mexicali, Ensenada, San Diego, and Los Angeles, PM10 and PM2.5 concentrations (particle matter with diameter below 10 µm and 2.5 µm) reached values over 2000 µg/m3 for PM10, with daily mean concentrations well above national standards, leading to poor air quality and representing a health threat even in short-term exposure. This Santa Ana event transported dust particles several hundreds of kilometers over urban areas, the Gulf of California, and the Pacific Ocean. Severe soil deterioration was simulated within the study area, reaching dust emissions above 700,000 t, including croplands from the northern part of Baja California and Sonora's coastal area.

     

Thinking Outside the Boxcar: Effective and Sustainable Combined Remedies Using Single Application of Multifunctional Amendments

The combined remedy approach to groundwater remediation optimizes contaminated site cleanup as measured by technical efficacy and sustainability. Regardless of the potential for improving site cleanups, there are several obstacles limiting the implementation of combined remedies. The obstacles primarily stem from an inability of liability owners to easily determine if economic costs are synergistic or additive and from regulatory hesitancy to codify needed timing and technology sequencing flexibility within design documents. These obstacles can often be circumvented by employing multicomponent and multifunctional remedial amendment formulations delivered with a single application. Case studies are presented that demonstrate efficacy of this combined remedies approach. The sustainability of the approach is also assessed by evaluation of economic viability, social productivity, and environmental protection. The case studies include combined abiotic and biotic degradation of chlorinated ethene and ethane compounds, combined reductive, and microaerophilic treatment of chlorinated benzenes, and combined chemical oxidation and biodegradation of petroleum compounds. Case studies are supported with conventional concentration trends and advanced diagnostics including compound specific isotope analysis (CSIA) and genetic‐based molecular biological tools (MBTs).     

Observational Constraints on Cloud Feedbacks: The Role of Active Satellite Sensors

Cloud profiling from active lidar and radar in the A-train satellite constellation has significantly advanced our understanding of clouds and their role in the climate system. Nevertheless, the response of clouds to a warming climate remains one of the largest uncertainties in predicting climate change and for the development of adaptions to change. Both observation of long-term changes and observational constraints on the processes responsible for those changes are necessary. We review recent progress in our understanding of the cloud feedback problem. Capabilities and advantages of active sensors for observing clouds are discussed, along with the importance of active sensors for deriving constraints on cloud feedbacks as an essential component of a global climate observing system.