Measuring the hydraulic conductivity of shallow submerged sediments

The hydraulic conductivity of submerged sediments influences the interaction between ground water and surface water, but few techniques for measuring K have been described with the conditions of the submerged setting in mind. Two simple, physical methods for measuring the hydraulic conductivity of submerged sediments have been developed, and one of them uses a well and piezometers similar to well tests performed in terrestrial aquifers. This test is based on a theoretical analysis that uses a constant-head boundary condition for the upper surface of the aquifer to represent the effects of the overlying water body. Existing analyses of tests used to measure the hydraulic conductivity of submerged sediments may contain errors from using the same upper boundary conditions applied to simulate terrestrial aquifers. Field implementation of the technique requires detecting minute drawdowns in the vicinity of the pumping well. Low-density oil was used in an inverted U-tube manometer to amplify the head differential so that it could be resolved in the field. Another technique was developed to measure the vertical hydraulic conductivity of sediments at the interface with overlying surface water. This technique uses the pan from a seepage meter with a piezometer fixed along its axis (a piezo-seep meter). Water is pumped from the pan and the head gradient is measured using the axial piezometer. Results from a sandy streambed indicate that both methods provide consistent and reasonable estimates of K. The pumping test allows skin effects to be considered, and the field data show that omitting the skin effect (e.g., by using a single well test) can produce results that underestimate the hydraulic conductivity of streambeds.     

Sorption of yttrium and rare earth elements by amorphous ferric hydroxide: Influence of solution complexation with carbonate

The influence of solution complexation on the sorption of yttrium and the rare earth elements (YREEs) by amorphous ferric hydroxide was investigated at 25 °C over a range of pH (4.0-7.1) and carbonate concentrations . Distribution coefficients, defined as , where [MS_i]_T is the total concentration of sorbed YREE, M_T is the total YREE concentration in solution, and [S_i] is the concentration of amorphous ferric hydroxide, initially increased in magnitude with increasing carbonate concentration, and then decreased. The initial increase of is due to sorption of YREE carbonate complexes , in addition to sorption of free YREE ions (M³⁺). The subsequent decrease of , which is more extensive for the heavy REEs, is due to the increasing intensity of YREE solution complexation by carbonate ions. The competition for YREEs between solution complexation and surface complexation was modeled via the equation:

     

大贵州滩下三叠统岩石和化学地层对比

南盘江盆地中的大贵州滩为一个自晚二叠世末期开始发育,至晚三叠世初期停止生长的孤立型碳酸盐岩台地。早期的研究工作主要集中于台地内部、北部斜坡和盆地边缘,并认为大贵州滩下三叠统地层格架的几何形态近于对称。本次研究以下三叠统岩石地层对比为基础,借助早三叠世期间δ13C波动频繁且幅度较大的特点进行化学地层对比后发现：台地南缘二...     

Regional- and district-level drivers of timber harvesting in European Russia after the collapse of the Soviet Union

After the collapse of the Soviet Union, the forestry sector in Russia underwent substantial changes: the state forestry sector was decentralized, the timber industry was privatized, and timber use rights were allocated through short- and long-term leases. To date, there has been no quantitative assessment of the drivers of timber harvesting in European Russia following these changes. In this paper we estimate an econometric model of timber harvesting using remote sensing estimations of forest disturbance from 1990–2000 to 2000–2005 as our dependent variable. We aggregate forest disturbance to administrative districts – equivalent to counties in the United States – and test the impact of several biophysical and economic factors on timber harvesting. Additionally, we examine the impact that regions – equivalent to states in the United States and the main level of decentralized governance in Russia – have on timber harvesting by estimating the influence of regional-level effects on forest disturbance in our econometric model. Russian regions diverged considerably in political and economic conditions after the collapse of the Soviet Union, and the question is if these variations impacted timber harvesting after controlling for district-level biophysical and economic drivers. We find that the most important drivers of timber harvesting at the district level are road density, the percent of evergreen forest, and the total area of forest. The influence of these variables on timber harvesting changed over time and there was more harvesting closer to urban areas in 2000–2005. Even though district-level variables explain more than 70 percent of the variation in forest disturbance in our econometric model, we find that regional-level effects remain statistically significant. While we cannot identify the exact mechanism through which regional-level effects impact timber harvesting, our results suggest that sub-national differences can have a large and statistically significant impact on land-use outcomes and should be considered in policy design and evaluation.     

Using Stable Isotope Mixing in a Great Lakes Coastal Tributary to Determine Food Web Linkages in Young Fishes

We characterized stable isotope mixing along a river-Great Lake transition zone in the St. Louis River, an important fish nursery in western Lake Superior, and used it to identify food web linkages supporting young fish production. We observed a broad, spatial pattern in the carbon stable isotope ratio (δ¹³C); downriver enrichment in particulate organic carbon and aquatic vegetation δ¹³C, as well as pelagic, benthic and littoral invertebrate δ¹³C, reflected isotope mixing along the river-lake transition zone. Fishes with similarly enriched δ¹³C were used to identify benthopelagic and littoral trophic pathways. River and Lake Superior organic matter (OM) sources contributed to both pathways. Differences between the δ¹³C in fishes and invertebrate prey revealed that fish production was supported at multiple spatial scales. The result was that the food web specific to any location along the transition zone incorporated multiple OM sources from across the watershed.     

Petrogenetic relations among titanium‐rich minerals in an anatectic high‐P mafic granulite

The petrogenetic relations among Ti‐rich minerals in high‐grade metabasites is illuminated here through a detailed petrological investigation of an anatectic garnet–clinopyroxene granulite from the Grenville Province, Ontario, Canada containing rutile, titanite and ilmenite in distinct microtextural settings. Garnet porphyroblasts exhibit zoned Ti concentrations (up to 0.15 wt% TiO₂ in their cores), as well as a variety of rutile inclusion types, including clusters of small, variably elongate grains and thin (≤1 μm) oriented needles. Calcite inclusions in garnet, commonly observed surrounding garnet cores containing quartz and clinozoisite, indicate the presence of evolving C–O–H fluids during garnet growth and suggest that the rutile clusters may have formed from subsequent Ti diffusion and rutile precipitation within existing fluid inclusions. Titanite forms large subhedral crystals and typically occurs where the primary garnet–clinopyroxene assemblage is in contact with leucosome containing megacrystic hornblende, silvialitic scapolite and calcic plagioclase. Many titanite crystals exhibit marginal subgrains that correspond with sharp changes in their major and trace element composition, likely related to a dissolution–precipitation or recrystallization process following primary crystallization. Clinopyroxene–ilmenite symplectite coronas surround titanite in most locations, likely forming from reaction with the hornblende‐plagioclase matrix (±fluids/melt). Integration of multi‐equilibria thermobarometry and Zr thermometry in rutile and titanite with phase equilibrium modelling allows definition of a clockwise P–T path evolving to peak pressures of ~1.5 GPa at ~750°C during garnet and rutile growth, followed by peak temperature conditions of ~1.2 GPa and ~820–880°C associated with melt‐present titanite growth, and finally cooling and decompression to regional amphibolite facies conditions (~1.0 GPa and ~750°C) associated with the formation of clinopyroxene–ilmenite symplectites surrounding titanite. P–T pseudosections calculated for the pristine (leucosome‐ and titanite ‐free) metabasite bulk composition reproduce much of the prograde phase relations, but predict rutile as the stable Ti‐rich mineral at the peak thermal conditions associated with melt‐present titanite growth. The P–M(CaO) and T–M(CaO) models show that bulk CaO concentrations have a significant effect on the stability ranges of titanite and rutile. Increased bulk CaO tends to stabilize titanite to higher pressure and temperature at the expense of rutile, with a ≥15% increase in CaO producing the observed titanite‐bearing assemblage at high‐P granulite facies conditions. Thus, the model results are consistent with the textural observations, which suggest that titanite stability is associated with a chemical exchange between the host metabasite and a Ca‐rich melt.     

Emerging transitions in organic waste infrastructure in Aotearoa New Zealand

Aotearoa New Zealand is at a critical juncture in reducing and managing organic waste. Research has highlighted the significant proportion of organic waste sent to landfills and associated adverse effects such as greenhouse gas emissions and loss of valuable organic matter. There is current debate about what practices and infrastructure to invest in to better manage and use organic waste. We highlight the diversity of existing organic waste practices and infrastructures, focusing on Auckland, Wellington and Christchurch. We show how debates about organic waste practices and infrastructure connect across three themes: waste subjectivities, collective action in place and language.     

Health monitoring of fluid dampers for vibration control of structures: experimental investigation

This paper presents results from a comprehensive experimental program on medium-size and large-size fluid dampers in an effort to extract their force output during cyclic loading by simply measuring the strain on the damper housing and the end-spacer of the damper. The paper first discusses the stress path within the damper and, subsequently via the use of linear elasticity, shows that the experimental data obtained with commercially available strain gauges yield a force output of the damper that is in good agreement with the readings from the load cell. This comparison is achieved via the use of a position and velocity transducer, which combines good accuracy together with robust performance in a marine environment. The paper then examines the performance of a portable data acquisition system that can be used to collect and transmit data from a damper installed on a bridge to a nearby location (order of a km) where data are collected via either a wired or a wireless Local Area Network (LAN). Alternatively, the data may be transmitted to any remote location via mobile telecommunication networks; however, this requires leased telephone lines. The data show that the proposed arrangement is promising for monitoring in situ the force output of fluid dampers and detecting possible loss of their energy dissipation capability. Copyright © 2012 John Wiley & Sons, Ltd.