Magnetic properties of surface sediments as proxies of recent anthropogenic pollution in the Anllóns riverbed (NW Spain)     

Vincenzo Costanzo-Álvarez  Rosa Devesa-Rey  Milagrosa Aldana  María Teresa Barral  Diego López-Rodríguez  Belkys Andrade 《Environmental Earth Sciences》2017,76(13):454

A study of surface sediments from the Anllóns riverbed (northwestern Spain) was conducted to assess the use of their magnetic properties as proxies of recent trace element contamination (i.e., As, Zn, Pb, Cr, Ni and Cu). Thermomagnetic curves, hysteresis parameters, specific magnetic susceptibility χ, frequency-dependent magnetic susceptibility κ _FD%, magnetic remanence and saturation isothermal remanent magnetization ratios (i.e., S and SIRM/χ) reveal the presence of mostly fine-grained magnetite and maghemite in these samples. The Tomlinson Pollution Load Index (PLI), as well as the magnetic parameters χ, κ _FD%, SIRM/χ and S-ratios, vary more or less in agreement to each other when they are sequentially arranged throughout a 30-km-long transect that goes from the town of Carballo to the river mouth in Ponteceso. From that profile, it is possible to identify an anomaly of χ that lies between two small peaks of the PLI and seems to define a contaminated area probably linked to a diffuse low-impact source of pollution. There is also a conspicuous peak of the PLI that is likely associated to a nearby gold mine. The variations of the κ _FD%’s along the transect are the ones that best reflect the changes in the PLI values, regardless of the level of contamination. This result suggests that adsorption is the main mechanism of trace elements removal by Fe oxides in these samples. Direct signal analyses, used to decompose the isothermal remanent magnetization curves, reveal the presence of four magnetic fractions, with varying relative concentrations all over the profile, namely single-domain magnetite, close to the superparamagnetic threshold (SD/SP) and/or maghemite (\(\log B_{1/2}\) ca 1.2), single-domain magnetite (\(\log B_{1/2}\) ca 2), hematite (\(\log B_{1/2}\) ca 2.5) and goethite (\(\log B_{1/2}\) ca 3.5). Integrating all the available information, it was sketched out a likely sequence of events that included magnetic minerals neoformation in parent soils, their subsequent chemical transformations and the contamination episodes that affected the region.  相似文献   

Shallow groundwater temperature in the Turin area (NW Italy): vertical distribution and anthropogenic effects     

Arianna Bucci  Diego Barbero  Manuela Lasagna  M. Gabriella Forno  Domenico Antonio De Luca 《Environmental Earth Sciences》2017,76(5):221

This study investigated the thermal regime of shallow groundwater in the Turin area (NW Italy), where the large energy demand has motivated a new interest for renewable sources, such as the use of ground-source heat pumps for domestic heating and cooling. The vertical variability of the groundwater temperature between the ground surface and 10–20 m was detected: deeper temperatures were higher than shallow temperatures in spring, while a decrease with depth occurred in autumn. These variations are connected with the heating and cooling cycles of the ground surface due to the seasonal temperature oscillation. Variations below the seasonal oscillation are likely to be connected with the presence of advective heat transport due to the groundwater flow, according to the hydraulic features of a shallow aquifer. Temperature values mostly ranged between 12 and 14 °C in rural areas, while the values were between 14 and 16 °C below the Turin city. This groundwater warming is attributed to a widespread urban heat island phenomenon linked to warmer land surface temperatures in Turin city. Sparse warm outliers are connected with point heat sources and site-specific conditions of land and subsurface use, which may cause the aquifer temperature to rise. A relatively stable temperature below the seasonal fluctuation zone combined with high productivity and legislated limits for deeper groundwater use represent favourable conditions for a large-scale diffusion of groundwater heat pumps within the shallow aquifer. Moreover, this heat surplus should be regarded as a resource for future geothermal installations.  相似文献   

Functional diversity of fish and invertebrates in coral and rocky reefs of the Eastern Tropical Pacific          下载免费PDF全文

Georgina Ramírez‐Ortiz  Luis E. Calderon‐Aguilera  Hector Reyes‐Bonilla  Arturo Ayala‐Bocos  Luis Hernández  Francisco Fernández Rivera‐Melo  Andres López‐Pérez  Arturo Dominici‐Arosamena 《Marine Ecology》2017,38(4)

To define the functional groups of fish and macroinvertebrates in the Eastern Tropical Pacific (ETP), visual censuses were performed in 18 areas of four biogeographic provinces: Cortés, Mexican, Panamic and Oceanic Islands. A total of 257 fish and macroinvertebrate species were recorded, and from them, 27 morpho‐functional groups (MFGs) were constructed on the basis of trophic level, maximum size, taxonomy and morphology. Biomass, richness, diversity and evenness of MFGs were calculated for each province and compared statistically; a regression analysis between taxonomic and functional diversity was conducted to observe the relationship between these two indicators. There were significant differences in all ecological indices (p < .002), highlighting the high biomass and richness of MFGs in the Cortés and Oceanic Islands provinces (>400 g/m²), associated with the influence of cold currents in the northernmost region and less fishing pressure in protected areas. A decreasing pattern of MFG richness towards the tropics was observed, which demonstrates that in the ETP, the relationship between habitat heterogeneity and species diversity has been translated into functional complexity. The Mexican province was the most functionally diverse (biomass well distributed in the MFG; H′ = 0.46 ± 0.009). Related to this, it is predicted that biomass is biased towards certain functional groups (i.e., large carnivores), which shows that the H′ index of the MFG is not a good indicator of the conservation status of ETP reefs. Finally, regression analysis suggests that functional diversity increases at low species diversity but eventually reaches an asymptote (almost all possible functions are represented).  相似文献   

Emplacement age of the Markagunt gravity slide in southwestern Utah,USA     

McKenna E. Holliday  Tiffany Rivera  Brian Jicha  Robin B. Trayler  Robert F. Biek  Michael J. Braunagel  W. Ashley Griffith  David B. Hacker  David H. Malone  Danika F. Mayback 《地学学报》2023,35(1):66-72

The Markagunt gravity slide (MGS) is a large-volume landslide in southwestern Utah that originated within the Oligocene-Miocene Marysvale volcanic field. Gravity slides are single emplacement events with long runout distances and are now recognized as a new class of volcanic hazard. Accumulation of volcanic material on a structurally weak substrate along with voluminous shallow intrusive events led to collapse. Here, ⁴⁰Ar/³⁹Ar data for landslide-generated pseudotachylyte, the landslide-capping Haycock Mountain Tuff and the deformed Osiris Tuff are combined with a Bayesian age model to determine an emplacement age of 23.05 + 0.22/−0.20 Ma for the MGS. The results suggest a lag time of <200 kyr between the caldera-forming eruption of the Osiris Tuff, additional buildup of the unstable volcanic pile and subsequent mass movement.  相似文献