Trace element contamination in fish impacted by bauxite red mud disposal in the Cassidaigne canyon (NW French Mediterranean).

From 1966 to 2015, the Gardanne alumina refinery discharged some 20 million tons of bauxite residue (called red mud) into the Cassidaigne Canyon (northwest French Mediterranean) with impacts on local ecosystem functioning. Although these red muds contained high levels of trace elements (TE), in particular titanium (Ti), vanadium (V), aluminum (Al) and arsenic (As), surprisingly, their impacts on fish contamination levels and the risk related to fish consumption have been little studied until now. Here, 11 trace elements (Al, As, Cd, Cr, Co, Cr, Mn, Ni, Pb, Ti and V) were analyzed in muscle and, when possible, liver, from 1308 fish of 26 species from an impacted zone in the vicinity of the Cassidaigne Canyon and a reference zone, unaffected by red mud disposals. Moreover, 66 arsenic speciation analyses were performed. Although the impact of human activities on the levels of fish contamination by trace elements is generally not easy to assess in situ because it is blurred by interaction with biological effects, we highlighted significant contamination of the fish species collected from the Cassidaigne Canyon, especially by the main trace elements attributable to the discharges of the Gardanne alumina refinery, namely Al, V and Ti. Moreover, inorganic toxic As concentrations were higher in the impacted zone. The results of this baseline research also confirmed the concern previously raised regarding Hg in Mediterranean organisms and that trace element contamination levels in fish are generally negatively related to fish length for all TE except Hg.

Construction of an Yucatec Maya soil classification and comparison with the WRB framework.

BACKGROUND: Mayas living in southeast Mexico have used soils for millennia and provide thus a good example for understanding soil-culture relationships and for exploring the ways indigenous people name and classify the soils of their territory. This paper shows an attempt to organize the Maya soil knowledge into a soil classification scheme and compares the latter with the World Reference Base for Soil Resources (WRB). METHODS: Several participative soil surveys were carried out in the period 2000-2009 with the help of bilingual Maya-Spanish-speaking farmers. A multilingual soil database was built with 315 soil profile descriptions. RESULTS: On the basis of the diagnostic soil properties and the soil nomenclature used by Maya farmers, a soil classification scheme with a hierarchic, dichotomous and open structure was constructed, organized in groups and qualifiers in a fashion similar to that of the WRB system. Maya soil properties were used at the same categorical levels as similar diagnostic properties are used in the WRB system. CONCLUSIONS: The Maya soil classification (MSC) is a natural system based on key properties, such as relief position, rock types, size and quantity of stones, color of topsoil and subsoil, depth, water dynamics, and plant-supporting processes. The MSC addresses the soil properties of surficial and subsurficial horizons, and uses plant communities as qualifier in some cases. The MSC is more accurate than the WRB for classifying Leptosols.

Radar remote sensing of wind-driven land degradation processes in northeastern Patagonia.

Wind-driven land degradation negatively impacts on rangeland production and infrastructure in the Valdes Peninsula, northeastern Patagonia. The Valdes Peninsula has the most noticeable dunefields of the Patagonian drylands. Wind erosion has been assessed at different scales in this region, but often with limited data. In general, terrain features caused by wind activity are better discriminated by active microwaves than by sensors operating in the visible and infrared regions of the electromagnetic spectrum. This paper aims to analyze wind-driven land degradation processes that control the radar backscatter observed in different sources of radar imagery. We used subsets derived from SIR-C, ERS-1 and 2, ENVISAT ASAR, RADARSAT-1, and ALOS PALSAR data. The visibility of aeolian features on radar images is mostly a function of wavelength, polarization, and incidence angle. Stabilized sand deposits are clearly observed in radar images, with defined edges but also signals of ongoing wind erosion. One of the most conspicuous features corresponds to old track sand dunes, a mixture of active and inactive barchanoid ridges and parabolic dunes. This is a clear example of deactivation of migrating dunes under the influence of vegetation. The L-band data reveal details of these sand ridges, whereas the C-band data only allow detecting a few of the larger tracks. The results of this study enable us to make recommendations about the utility of some radar sensor configurations for wind-driven land degradation reconnaissance in mid-latitude regions.

Remote sensing of land degradation: experiences from Latin America and the Caribbean.

Land degradation caused by deforestation, overgrazing, and inappropriate irrigation practices affects about 16% of Latin America and the Caribbean (LAC). This paper addresses issues related to the application of remote sensing technologies for the identification and mapping of land degradation features, with special attention to the LAC region. The contribution of remote sensing to mapping land degradation is analyzed from the compilation of a large set of research papers published between the 1980s and 2009, dealing with water and wind erosion, salinization, and changes of vegetation cover. The analysis undertaken found that Landsat series (MSS, TM, ETM+) are the most commonly used data source (49% of the papers report their use), followed by aerial photographs (39%), and microwave sensing (ERS, JERS-1, Radarsat) (27%). About 43% of the works analyzed use multi-scale, multi-sensor, multi-spectral approaches for mapping degraded areas, with a combination of visual interpretation and advanced image processing techniques. The use of more expensive hyperspectral and/or very high spatial resolution sensors like AVIRIS, Hyperion, SPOT-5, and IKONOS tends to be limited to small surface areas. The key issue of indicators that can directly or indirectly help recognize land degradation features in the visible, infrared, and microwave regions of the electromagnetic spectrum are discussed. Factors considered when selecting indicators for establishing land degradation baselines include, among others, the mapping scale, the spectral characteristics of the sensors, and the time of image acquisition. The validation methods used to assess the accuracy of maps produced with satellite data are discussed as well.

Posterior composite and glass ionomer/composite laminate restorations: 2-year clinical results.

The purpose of this investigation was to evaluate and compare the clinical performance of two posterior composite materials, and two placement techniques, unlaminated and laminated to glass ionomer base. Forty Class II carious lesions were randomly assigned for restoration with one of two composites: Status or Ful-Fil; and using one of two techniques: with and without a glass ionomer base. In the 20 restorations using the laminate technique, the glass ionomer base covered the dentin and extended to the cavosurface in the gingival third of the proximal box. The restorations were evaluated clinically at 24 hours, 6 months, 12 months and 24 months. The clinical parameters used for the examination were: anatomic form, marginal adaptation, color, secondary caries, marginal discoloration and contact. Bitewing radiographs were taken at 24 hours and at 24 months to evaluate gingival margin discrepancy. Impressions of the restorations were made for fabrication of stone dies. Of the 40 restorations, 38 (95%) were available for evaluation at 24 months. For both materials there was a deterioration in anatomic form, in marginal adaptation, and in marginal discoloration. Anatomic form was significantly worse with Status (P less than 0.05). Of the 20 restorations placed using the laminate technique, two had observable loss of the glass ionomer material. Radiographic radiolucencies were observed for both materials and with both techniques. For the laminate technique, all radiolucencies were between the glass ionomer and the composite. The radiographic observations did not change after the initial evaluation. All the restorations were functioning well at 24 months, but longer observation will be required to determine whether there is a clinically significant difference between the two placement techniques.

Chemomechanical caries removal--a clinical evaluation.

The aim of this investigation was to evaluate the efficacy and convenience of decayed dentine removal with N-monochloro-DL-2 aminobutyrate (CARIDEX) in all classes of cavities. Fifty-seven patients, each with two teeth having similarly sized carious cavities, participated in this study. One cavity in each patient was treated with the chemomechanical CARIDEX technique and the other cavity was treated with conventional mechanical drilling. The cavities were restored with either amalgam, composite or glass ionomer restorative materials. The time taken for access and caries removal was noted and the efficacy of caries removal with each technique was evaluated. The chemomechanical caries removal technique was effective in removing 90-100% of decayed dentine in 98% of the cavities treated. Multiple regression adjusted access and caries removal time to account for volume of caries removed. This adjusted time was operator dependent, and ranged from 4 to 10 minutes longer for CARIDEX than for the conventional technique. Ninety-three per cent of patients preferred the chemomechanical method of caries removal over the conventional technique (highly significant P less than 0.001). Even though the chemomechanical removal of caries is slower than the conventional technique, the efficacy of CARIDEX and its high patient acceptance provides a viable alternative method for dentinal caries removal in all classes of cavities.

The effectiveness of opaquer and color-modifier materials: a laboratory study.

New, direct bonding composite resin products are available for esthetic and restorative dentistry. As in vitro study was conducted to evaluate the stain-masking effectiveness of 57 opaquers or color modifiers. Results of the testing on 265 specimens are reported, ranging from minimal to excellent masking.

Preparation and purity measurement of extremely pure helium gas.

A procedure is described for the production, storage, and handling of very pure helium gas and for the measurement of its purity in the part per 10(11) range.