Climate warming, water storage, and Chinook salmon in California’s Sacramento Valley

The Chinook salmon (Oncorhynchus tshawytscha) spawns and rears in the cold, freshwater rivers and tributaries of California’s Central Valley, with four separate seasonal runs including fall and late-fall runs, a winter run, and a spring run. Dams and reservoirs have blocked access to most of the Chinook’s ancestral spawning areas in the upper reaches and tributaries. Consequently, the fish rely on the mainstem of the Sacramento River for spawning habitat. Future climatic warming could lead to alterations of the river’s temperature regime, which could further reduce the already fragmented Chinook habitat. Specifically, increased water temperatures could result in spawning and rearing temperature exceedences, thereby jeopardizing productivity, particularly in drought years. Paradoxically, water management plays a key role in potential adaptation options by maintaining spawning and rearing habitat now and in the future, as reservoirs such as Shasta provide a cold water supply that will be increasingly needed to counter the effects of climate change. Results suggest that the available cold pool behind Shasta could be maintained throughout the summer assuming median projections of mid-21st century warming of 2°C, but the maintenance of the cold pool with warming on the order of 4°C could be very challenging. The winter and spring runs are shown to be most at risk because of the timing of their reproduction.     

Plume Detachment and Recession Times in Fractured Rock

The influence of source zone concentration reduction on solute plume detachment and recession times in fractured rock was investigated using new semianalytical solutions to transient solute transport in the presence of advection, dispersion, sorption, matrix diffusion, and first-order decay. Novel aspects of these solutions are: (1) the source zone concentration behavior is simulated using a constant concentration with the option for either an instantaneous reduction to zero concentration or an exponentially decaying source zone concentration initiated at some time (t^*) after the source is introduced, and (2) different biodegradation rates in the fracture and rock matrix. These solutions were applied for sandstone bedrock and revealed that biodegradation in the matrix, not the fracture, may be the most significant attenuation mechanism and therefore may dictate remediation time scales. Also, instantaneous and complete source concentration reduction in aged plumes may not be beneficial with respect to plume response because back-diffusion can sustain plume migration for long periods of time. Moderate source zone concentration reduction has a similar impact on the rate of advance of the leading edge of the plume as aggressive concentration reduction. If the source zone concentration reduction half-life is less than the plume decay half-life, then volatile organic compound (VOC) mass sequestered in the rock matrix will ultimately dictate plume persistence and not the presence of the source zone.     

伊犁京希—伊尔曼德金矿床的热液蚀变及成矿流体演化特征

京希－伊尔曼德金矿床的热液蚀变在空间上有明显的分带性，中心蚀变带以强烈的硅化为主，典型的蚀变矿物组合为石英或玉髓和地开石，中间带为高级泥化带，以地开石－高岭石－石英或玉髓为特征；外带为以蒙脱石－高岭石－伊利石－其他粘土矿物等矿物组合为主的泥化带，蚀变强度和矿物组合的分带性是温度、压力和化学梯度的反映，是流体在不断的水或流体－岩石反应和成分交换的产物。该矿床成矿流体演化过程为：早期酸性（pH=2-3)含矿流体在沿断裂上升过程中，受围岩灰岩中的流体（pH为中性）缓冲，在其进入高渗透性的碎屑岩层时，流速和水－岩石或流休－岩石反应大大加快，并在与大气降水的混合作用下，pH值逐步升高（3－5），产生了流体的温度及成分梯度，在温度和压力迅速下降的条件下，金及蚀变矿物沉淀、结晶生长，形成了蚀变空间分带，中心带保存完好的多孔状石英和地开石等高级泥化矿物组合说明该矿床是高硫化热液体系作用下的产物。     

Development of a probabilistic approach for rock wedge failure

For rock slope engineering, uncertainty and variability are inherent in data collected on orientation and strength of discontinuities, yielding a range of results. Unfortunately, conventional deterministic analysis based on the factor of safety concept, requires a fixed representative value for each parameter without regard to the degree of uncertainty involved. Therefore, the deterministic analysis fails to properly represent uncertainty and variability, so common in engineering geology studies. To overcome this shortcoming, the probabilistic analysis method was proposed and used for more than a decade in rock slope stability analysis. However, most probabilistic analyses included a deterministic model as part of the analysis procedure causing subsequent problems, which went uncorrected. The objectives of this paper are to develop a solution for these difficulties in probabilistic analyses and to propose an appropriate simulation procedure for the probabilistic analysis of rock wedge failures. As part of the solution, probability of kinematic instability and probability of kinetic instability are evaluated separately to provide a proper, combined evaluation for failure probability. To evaluate the feasibility of this new probabilistic approach, the procedure is applied to a practical example, a major, highway rock cut in North Carolina, USA. Results of the probabilistic approach are compared to those of the deterministic analysis; findings are significantly different, indicating that the deterministic analysis does not depict rock slope variations, particularly where significant scatter in parameter data occurs.     

Infant feeding in North East England: contested spaces of reproduction

Decisions about infant feeding are commonly viewed as an issue of personal choice made in the light of information about the benefits of breastfeeding. A pilot study of first-time parents' decisions and experiences in Newcastle upon Tyne, England, suggests that local cultural contexts, in particular how men and women are seen to be parenting in different spaces, have a profound influence on infant feeding.     

Glonass Laser Ranging Accuracy With Satellite Signature Effect

GLONASS satellites have been tracked by the worldwide laser ranging networkas well as by the GLONASS-borne microwave-based technique. Owing to thelarge size of their corner cube reflector arrays, the amount of ranging data is enough to determine their orbits from laser ranging data alone. We found, however, that the large size of the array affected the accuracy of measurement to an extent that is dependent on the characteristics of the ranging systems. An azimuthal variation of the reflector array response was also detected in observations from single-photon laser ranging. Orbital analysis reveals that the effect makes the measured range on average 22 mm shorter than expected in the absence of the large array, which explains more than half of the offset of 39 mm previously discovered between microwave and laser orbits.     

Ion microprobe evidence for the mechanisms of stable isotope retrogression in high-grade metamorphic rocks

Retrograde interdiffusion is widely proposed as the dominant factor in producing the stable isotopic fractionation among minerals in slowly cooled igneous and metamorphic rocks. Mineral zonation consistent with interdiffusion of stable isotopes has never been directly observed, however, leaving doubt as to the mechanism responsible for the bulk-mineral isotopic compositions commonly measured. Ion microprobe analyses of oxygen isotope ratios in magnetite were combined with conventional bulk mineral analyses and diffusion modeling to document the relationship between mineral zonation and the mechanism of retrogression inferred from bulk mineral data. Two samples of magnetitebearing, quartzo-feldspathic Lyon Mountain gneiss from the Adirondack mountains, N.Y. were studied in detail. Conventional stable isotope analysis of both samples indicates that isotope thermometers are discordant and were reset by as much as 200°C from the estimated peak temperature of 750°C. The relative order of apparent temperatures recorded by various thermometers differs between the two samples, however, with T _qtz-fsp≫T _mt-qtz and T _mt-fsp in one sample and T _qtz-fsp<T _mt-qtz and T _mt-fsp in the other. Diffusion modeling using the Fast Grain Boundary model shows that the former pattern of apparent temperatures is consistent with closed system interdiffusion during cooling, whereas the latter is not. The modeling predicts that 0.5 mm diameter magnetite grains common to this rock type will contain isotopic zonation of 1‰ (rims lower in δ¹⁸O than cores), and that the cores of smaller (0.1 mm) grains will be similarly lower than to the cores of large (0.5 mm) grains. Ion microprobe analysis reveals that the zoning patterns of magnetite grains from the first sample contain clear core to rim zonation in multiple grains (Δcore-rim=1.1±0.4‰) and predicted grain-size vs core composition variations, consistent with diffusion-controlled resetting of bulk mineral fractionations. In contrast, the second sample shows irregular inter-and intra-granular variations over an 8‰ range, consistent with open system alteration. These results provide direct documentation of the importance of interdiffusion in affecting stable isotope distributions in slowly cooled rocks. The correlations of bulk-mineral resetting with zonation show that bulk mineral data, when interpreted with detailed modeling, can be used to determinate what processes controlling retrogression.