A geostatistically based inverse model for three-dimensional variably saturated flow

We present a geostatistically based inverse model for characterizing heterogeneity in parameters of unsaturated hydraulic conductivity for three-dimensional flow. Pressure and moisture content are related to perturbations in hydraulic parameters through cross-covariances, which are calculated to first-order. Sensitivities needed for covariance calculations are derived using the adjoint state sensitivity method. Approximations of the conditional mean parameter fields are then obtained from the cokriging estimator. Correlation between parameters and pressure – moisture content perturbations is seen to be strongly dependent on mean pressure or moisture content. High correlation between parameters and pressure data was obtained under saturated or near saturated flow conditions, providing accurate estimation of saturated hydraulic conductivity, while moisture content measurements provided accurate estimation of the pore size distribution parameter under unsaturated flow conditions.     

Concentration and spatial variability of mercury and other heavy metals in surface soil samples of periurban waste mine tailing along a transect in the Almadén mining district (Spain)

Mercury (Hg) is one of the elements with increasing environmental significance. A total of 22 samples (soils, rocks and gels) were collected along a 6 km transect around the Valdeazogues River valley in the southwest of the Iberian Peninsula (Almadén, Spain). Samples were characterized by different soil types of depositional sequences associated with mining tailings, type and system tracts: 15 surface soil samples included in the transect; 3 of a Haploxerept soil profile developed on slates; 2 of quartzite and slates rocks (reference rocks in the area). Moreover, two of a gel substance (in the lower tract of the river). Soil samples were analyzed for Hg, Cu, Ni, Cr, V, Pb, Cd and As, as well as for organic matter, pH abrasion and calcium carbonate content. All samples were collected from the Almadén mining district. The level of occurrence of the elements (especially Hg) and the effect of some properties on its concentration distributions were investigated. The total mercury contents varied in the range 7,315–3.44 mg kg⁻¹. The mean concentration of total mercury in soils and rocks was 477.03 mg kg⁻¹dry mass. This value is very high compared to the regional background value of other areas. Only rarely is it higher than 1%: in one sample (7,315 mg kg⁻¹) it was almost eight times in comparison with the affected zones, with a high value of 1,000 mg kg⁻¹. Significant differences between samples were found in the total content of mercury. A large percentage of the samples registered detectable levels of V, Cr, Ni, Pb, As and Cu. Cd readings were below the detectable range for all samples tested. Cr mean concentration was 216.95 mg kg⁻¹ (minimun concentration 86, maximun 358); V mean concentration was 119.09 mg kg⁻¹ (minimun concentration 69, maximun 1,209); As mean concentration was 51.24 mg kg⁻¹ (minimun 13.3 and maximun 319.4); Ni mean concentration was 45.64 mg kg⁻¹ (minimun concentration 21.2 and maximun 125.6); Cu mean concentration was 33.25 mg kg⁻¹ (minimun concentration 19.3 and maximun 135); Pb mean concentration was 15.19 mg kg⁻¹ (minimun 1.12 and maximun 1013). Metal distribution generally showed spatial variability ascribed to significant anthropogenic perturbation by mining tailing type. Hg showed vertical profile characterized by surface enrichment, with concentrations in the upper layer (93.7–82.2 mg kg⁻¹ in front of 3.4 of the rock value) exceeding, in several occasions, the background value. The results obtained denote a potential toxicity of some heavy metals in some of the studied samples. Water-soluble mercury could enter the aquatic system and accumulate in sediments. Mercury and other heavy metals contamination depended on the duration and intensity of mining activities.     

Climate policies after Fukushima: three views

The 2011 Japanese earthquake and tsunami, and the consequent accident at the Fukushima nuclear power plant, have had consequences far beyond Japan itself. Reactions to the accident in three major economies Japan, the UK, and Germany, all of whom were committed to relatively ambitious climate change targets prior to the accident are examined. In Japan and Germany, the accident precipitated a major change of policy direction. In the UK, debate has been muted and there has been essentially no change in energy or climate change policies. The status of the energy and climate change policies in each country prior to the accident is assessed, the responses to the accident are described, and the possible impacts on their positions in the international climate negotiations are analysed. Finally, the three countries' responses are compared and some differences between them observed. Some reasons for their different policy responses are suggested and some themes, common across all countries, are identified

Policy relevance

The attraction of nuclear power has rested on the promise of low-cost electricity, low-carbon energy supply, and enhanced energy independence. The Fukushima accident, which followed the Japanese tsunami of March 2011, has prompted a critical re-appraisal of nuclear power. The responses to Fukushima are assessed for the UK, Germany, and Japan. Before the accident, all three countries considered nuclear as playing a significant part in climate mitigation strategies. Although the UK Government has continued to support nuclear new build following a prompt review of safety arrangements, Japan and Germany have decided to phase out nuclear power, albeit according to different timescales. The factors that explain the different decisions are examined, including patterns of energy demand and supply, the wider political context, institutional arrangements, and public attitudes to risk. The implications for the international climate negotiations are also assessed.     

Mobile Pb-isotopes in Proterozoic sedimentary basins as guides for exploration of uranium deposits

Lead isotope ratios and associated trace element concentrations (U, Th and Pb) extracted by partial-leaching with 2% nitric acid from Proterozoic sandstones and basement rocks reveal much about the fluid evolution of sedimentary basins hosting unconformity-type uranium deposits. In addition, these techniques have great potential as a guide for exploration of uranium and other types of deposits in basins of any age. Isotope ratios of Pb in Proterozoic sandstones from basins known to contain high-grade uranium deposits are radiogenic at key geological localities and settings distal to known mineralization and particularly in altered zones proximal to mineralization. Sandstones completely cemented by quartz overgrowths typically have non-radiogenic Pb isotope ratios, indicating early closure of porosity and isolation of these rocks from later fluid events. Alternatively, the unconformity served as both a source of uranium and radiogenic Pb as well as an avenue for late-stage (<250–900 Ma) fluid flow. The mafic volcanic units, which are relatively reducing lithologies and therefore have removed uranium from basinal brines, have uranium-supported radiogenic Pb isotope ratios. Comparison of ²³⁸U/²⁰⁶Pb and ²⁰⁶Pb/²⁰⁴Pb ratios is useful in determining the timing and nature of U and Pb migration before, during and after mineralization in these basins. This comparison can be used to delineate the presence of radiogenic Pb isotope ratios that are not internally supported by uranium and thorium in rocks, eventually providing the explorationist with geochemical vectors that point toward sites of high potential for economic uranium mineralization.     

Is Australia becoming more unequal?

Several researchers have argued that Australia is becoming more unequal. This paper briefly explores the reasons why this might be the case before undertaking a social indicator based examination of whether income inequality extends to well‐being generally. Using 176 regions and eight social indicators and focusing on the period 1976–91, the paper shows that inequality has increased, particularly in the last intercensal period. The pattern of ‘winning’ and ‘losing’ is a complex one that suggests increasing differentiation between regions. This finding is set in the context of the social differentiation inherent in postmodern society. Regional policy based on the devolution of spending and responsibility is advocated as one way of helping disadvantaged regions.     

A new method for estimating high-frequency radar error using data from Central San Francisco Bay

This study offers a new method for estimating High-Frequency (HF) radar surface current velocity error in data comparisons with other types of instrumentation. A new method is needed in order to remove the zero-mean random spatial and temporal fluctuations present in surface-current measurements from all sensors. Conventional methods for calculating radar error when comparing with another instrument have included their root mean square differences and scatter plots that provide correlation coefficient and slope/intercept of the regression line. It seems that a meaningful estimate of radar error should attempt to remove both sensors’ zero mean random fluctuations, inasmuch as possible. We offer and compare a method that does this. The method was tested on data collected in the Central San Francisco Bay, where GPS surface-drifter deployments were conducted within the coverage of four 42 MHz radars over six days in October of 2008. Drifters were continuously deployed in these areas over the sampling days, providing 525 usable drifter measurements. Drifter and radar measurements were averaged into thirty-minute time bins. The three-day long-term averages from the sampling areas were then subtracted from the thirtyminute averages to remove biases associated with comparisons done with short, disjoint time-sample periods. These were then used to develop methods that give radar error or bias after the random fluctuations have been removed. Results for error estimates in this study are commensurate with others where random fluctuations have been filtered, suggesting they are valid. The estimated error for the radars in the SF Bay is low, ranging from ?7.57 cm/s to 0.59 cm/s.     

Patterns and dynamics of urban forests in relation to land use and development history in Guangzhou City, China

Trees in cities display a varied pattern that is often moulded by a city's physical fabric and its evolution through time. The town plan expressed in spatial dimension as land use, and in temporal sense as development history, furnishes a framework to evaluate the intricate association between city and trees. Guangzhou city, the premier metropolis of south China, has been established for 2800 years, and has a long history of urban greening and heterogeneous land use. Five urban districts, which represent old, middle-aged and young stages of development and cover the bulk of the city's built-up zones, form the study area. Interpretation of aerial photographs is used as a basis to classify the urban forest into three types, and to design a sampling scheme for studying trees in urban parks, institutional grounds and roadsides. District history has bequeathed a plethora of configurations in terms of buildings, roads and land uses, accompanied by plantable spaces of dissimilar dimensions, geometry and quality. The districts display diverse tree attributes such as frequency, density and species diversity. Young districts, with lower density, more institutional uses and wider roads, present more opportunities for greening. Recent shifts in landscape fashion have introduced a significantly different treescape. A few exceptionally large parks and institutional sites play a pivotal role in the city's tree assets. Parks, roadsides and institutional forests have different tree-stocking rates and species assemblages. Implications for future planting and management of urban trees in different situations, and for the greening of other cities in China, and other developing countries, are explored.