A factor analytic approach to the identification of geomorphic processes from soil particle size characteristics

Q-mode factor analysis of soil particle size data is used to identify the three dominant geomorphic processes responsible for the spatial variability of particle size in a catchment on the basaltic Darling Downs landsurface. Three factors are shown to account for 95 per cent of the textural variability of a suite of transported and sedentary materials. The spatial characteristics of groups of samples associated with the three factors suggests that the three factors are associated with suspended sediment transport and deposition, weathering, and bedload transport and deposition respectively. These interpretations are supported by the detailed graphical analysis of the cumulative particle size curves. The spatially variable influence of the three factors and related processes is given by their respective factor loadings which are mappable for the surface layer materials.     

A Three-year Study of Nonmethane Hydrocarbons in Surface Air over Saxony (Germany)

Measurements of the nonmethane hydrocarbon (NMHC) mixing ratio over a period of 42 months were carried out for the first time in the air of a research station situated in the former East Germany during the SANA project. Apart from four species, all other species analysed showed a statistically significant downward trend at the 95% significance level. The decrease of the hydrocarbon concentrations was superimposed by seasonal variations. A drop of about 40% of the annual mean values from 1993 to 1995 was observed. This development reflects the dramatic changes in traffic, industry, power economy, and agriculture in Saxony after the reunification of Germany. The remove of two-stroke engined cars is reflected in NMHC mixing ratio changes, as is the removal of obsolete chemical plants. Generally it was not possible to relate causes and effects of a single event, but in some cases major changes in concentrations and NMHC ratios occurred coincidentally with the disappearance of a specific emission source.     

Crack nucleation in saturated porous media

Crack nucleation has been the subject of important contributions in the last two last decades. However, it seems that few attention has been granted to the case of saturated porous media. This is the question addressed in the present paper which is devoted to nucleation in traction mode. From a physical point of view, nucleation is a sudden phenomenon, so that the material response is both adiabatic and undrained. In the spirit of the variational approach, the nucleated crack is viewed as the final state of a region of space in which the material undergoes a full damage process. In traction mode, the opening of a saturated crack in undrained condition induces a drop of fluid pressure. In case of low fluid compressibility, the presence of the fluid delays the brittle failure usually associated with nucleation, as long as the fluid pressure remains above the saturation vapor pressure. Nucleation is therefore possible only if a partial vaporization of the fluid takes place.     

Kimberlites: Their relation to mantle hotspots

Available age data support the hypothesis that kimberlite intrusions are formed by mantle hotspots. The hypothesis has been tested by inverting the volcanic traces formed by three hotspots to determine the post-Triassic motions of Africa, South America, and North America relative to these hotspots. Then, using these motions, the kimberlites intruded on these continents within the last 150 m.y. are relocated to their place of origin in the present hotspot reference frame. The result indicates that a majority of the kimberlites formed within 5° of a mantle hotspot. Statistical analysis shows that this kimberlite/hotspot correlation is significant at above the 90% level.     

China’s national carbon emissions trading scheme: lessons from the pilot emission trading schemes,academic literature,and known policy details

Upon completion, China’s national emissions trading scheme (C-ETS) will be the largest carbon market in the world. Recent research has evaluated China’s seven pilot ETSs launched from 2013 on, and academic literature on design aspects of the C-ETS abounds. Yet little is known about the specific details of the upcoming C-ETS. This article combines currently understood details of China’s national carbon market with lessons learned in the pilot schemes as well as from the academic literature. Our review follows the taxonomy of Emissions Trading in Practice: A Handbook on Design and Implementation (Partnership for Market Readiness & International Carbon Action Partnership. (2016). Retrieved from www.worldbank.org): The 10 categories are: scope, cap, distribution of allowances, use of offsets, temporal flexibility, price predictability, compliance and oversight, stakeholder engagement and capacity building, linking, implementation and improvements.

Key policy insights

• Accurate emissions data is paramount for both design and implementation, and its availability dictates the scope of the C-ETS.

• The stakeholder consultative process is critical for effective design, and China is able to build on its extensive experience through the pilot ETSs.

• Current policies and positions on intensity targets and Clean Development Mechanism (CDM) credits constrain the market design of the C-ETS.

• Most critical is the nature of the cap. The currently discussed rate-based cap with ex post adjustment is risky. Instead, an absolute, mass-based emissions cap coupled with the conditional use of permits would allow China to maintain flexibility in the carbon market while ensuring a limit on CO₂ emissions.

     

Summer temperature variability across four urban neighborhoods in Knoxville,Tennessee, USA

The urban heat island (UHI) is a well-documented effect of urbanization on local climate, identified by higher temperatures compared to surrounding areas, especially at night and during the warm season. The details of a UHI are city-specific, and microclimates may even exist within a given city. Thus, investigating the spatiotemporal variability of a city’s UHI is an ongoing and critical research need. We deploy ten weather stations across Knoxville, Tennessee, to analyze the city’s UHI and its differential impacts across urban neighborhoods: two each in four neighborhoods, one in more dense tree cover and one in less dense tree cover, and one each in downtown Knoxville and Ijams Nature Center that serve as control locations. Three months of temperature data (beginning 2 July 2014) are analyzed using paired-sample t tests and a three-way analysis of variance. Major findings include the following: (1) Within a given neighborhood, tree cover helps negate daytime heat (resulting in up to 1.19 ^°C lower maximum temperature), but does not have as large of an influence on minimum temperature; (2) largest temperature differences between neighborhoods occur during the day (0.38–1.16 ^°C difference), but larger differences between neighborhoods and the downtown control occur at night (1.04–1.88 ^°C difference); (3) presiding weather (i.e., air mass type) has a significant, consistent impact on the temperature in a given city, and lacks the differential impacts found at a larger-scale in previous studies; (4) distance from city center does not impact temperature as much as land use factors. This is a preliminary step towards informing local planning with a scientific understanding of how mitigation strategies may help minimize the UHI and reduce the effects of extreme weather on public health and well-being.     

Enhanced geochemical gradients in a marine shallow-water hydrothermal system: Unusual arsenic speciation in horizontal and vertical pore water profiles

The shallow marine hydrothermal vents near Ambitle Island in eastern Papua New Guinea discharge hot, slightly acidic, As-rich, chemically reduced fluid into cool, slightly alkaline, oxygenated seawater. Gradients in temperature, pH, and total As (As^T), among others, are established as the two aqueous phases mix. The hydrothermal fluid contained 900 μg/L As^T, almost exclusively present as the reduced As^III, while local seawater measured between 1.2 and 2.4 μg/L As, with approximately equal levels of As^III and As^V. Of particular interest in this study was As speciation and abundance in pore waters as a function of sediment depth and as a function of distance from the area of focused venting. With increasing distance, As^T concentration in the pore water decreased rapidly, but remained elevated up to 300 m from the area of focused venting when compared to a non-hydrothermal control site. As a function of depth (to 100 cm) As^T concentration in the pore water profiles was elevated and generally increased with depth. Surprisingly, aqueous As^V far exceeded aqueous As^III at almost all distances and depths investigated, while at the control site the As^III concentration exceeded that of As^V. In the Tutum Bay hydrothermal system, chemical disequilibria among As species provide potential metabolic energy for arsenite oxidizing microorganisms where hydrothermal fluid mixes with seawater near the vent orifice, and for arsenate reducing microorganisms with increasing distance and depth from the hydrothermal point source.