Phytoaccumulation of trace elements (As, Cd, Co, Cu, Pb, Zn) by Nicotiana glauca and Euphorbia segetalis growing in a Technosol developed on legacy mine wastes (Domingo Rubio wetland, SW Spain)

Sulfidic mine wastes have the potential to generate acid mine drainage (AMD) and release acid leachates containing high levels of iron, sulfate and potentially toxic elements (PTEs). Soils receiving AMD discharges are generally devoid of vegetation. Only a few metal-tolerant plant species can survive under such adverse soil conditions. This work investigates two plant species, Nicotiana glauca and Euphorbia segetalis, that have successfully colonized an AMD-impacted wetland area in south-western Spain. The uptake of PTEs from the soil by roots and their transfer and accumulation in the above-ground biomass were quantified. Results showed that these pioneer plants grew in patches of neutral soil within the wasteland despite the high concentrations of PTEs in the rhizosphere soil (up to: 613 mg kg-1 As, 18.7 mg kg-1 Cd, 6370 mg kg-1 Cu, 2210 mg kg-1 Pb and 5250 mg kg-1 Zn). The target organs of As, Cu and Pb accumulation were: root > leaf > stem in N. glauca, and root > stem > leaf in E. segetalis. Zinc and Cd showed a significant decrease in roots relative to aerial parts of N. glauca, and Co was preferentially partitioned in stems of N. glauca and leaves of E. segetalis. The soil-plant transfer coefficient values of PTEs in all parts of both plants were well below unity with the only exception of Cd in leaves of N. glauca (1.254), suggesting that roots acted as a barrier limiting the uptake of PTEs by plants. Interestingly, under the same soil conditions, N. glauca absorbed Cd in considerable proportions from soil and accumulated it in its leaves, while E. segetalis was not effective in transferring PTEs from roots shoots except for Co. In conclusion, soil pH and plant-related factors greatly influence the stabilization of PTE in the rhizospheric soil and produce inconsistencies in PTE phytoavailability. The findings of this study provide criteria to assist in natural remediation in other legacy contaminated sites worldwide.

Pyrolysis of municipal solid waste compost: Pilot plant evaluation as a sustainable practise of waste management

To evaluate the potential of compost based on municipal solid waste (MSW) and 20% legume pruning under a pyrolysis process, generated products, including solids (biochar), liquids (bio-oil), and gases (non-condensable gases), through experimentation in a pilot plant with a fluidized bed reactor at 450°C and gas chromatography/mass spectrometry have been analysed. In addition, the compost kinetic behaviour by thermogravimetric analysis (TGA), using the Flynn-Wall-Ozawa (FWO) method, has been investigated. Four different reaction zones, associated with lignocellulosic materials (hemicellulose, cellulose, and lignin) with a first step for water evaporation, in TGA curve have been observed. A biochar with low stability and aromaticity, considering high and low O/C and H/C ratios, respectively, has been obtained. The obtained pyrolytic liquids contain a high concentration of phenolic compounds because of a significant presence of lignins and other high molecular weight compounds in the original material. Moreover, the generated non-condensable gases consist mainly of short-chain compounds, such as alcohols, aldehydes, and alkenes produced from hemicellulose, cellulose, and proteins.

Comparative study of the combustion, pyrolysis and gasification processes of Leucaena leucocephala: Kinetics and gases obtained

Leucaena leucocephala is a fast-growing leguminous biomass with great energetical and value-added chemical compounds potential (saccharides, biogas, bio-oil, etc.). Using the thermogravimetric and derivative thermogravimetric curves, the different trends followed by L. leucocephala during pyrolysis, 0.25 equivalence ratio (ER) of gasification, 0.50 equivalence ratio of gasification and combustion were analyzed, and the activation energies were obtained by Distributed Activation Energy Model (DAEM) method. Gas samples were collected through adsorption tubes during the gasification at 0.25 ER and 0.50 ER to observe the distribution of the main chemical products in this process by gas chromatography/mass spectrometry and were compared with pyrolysis products. It was found that small amounts of oxygen have changes in the kinetics of the process, leading to significant decreases in the activation energy at the beginning of the degradation of components such as cellulose (from 170 to 135 kJ mol-1 at 0.25 conversion at 0.50 ER gasification). The activation energy of lignin disintegration was also reduced (342 kJ mol-1), assimilating the beginnings of gasification processes such as the Boudouard reaction. 0.50 ER gasification is potentially an interesting process to obtain quality bio-oil, since a large amount of hexane is detected (44.96%), and value-added oxygenated intermediates such as alcohols and glycols. Gasification at 0.25 ER, on the other hand, is much more similar to pyrolysis, obtaining a wide variety of short-chain compounds resulting from the disintegration of the main lignocellulosic components, especially ketones such as 1-hydroxypropan-2-one (19.48%), and notable amount of furans and anhydrosugars like d-allose (5.50%).

L-arginine-containing mesoporous silica nanoparticles embedded in dental adhesive (Arg@MSN@DAdh) for targeting cariogenic bacteria

Dental caries is the major biofilm-mediated oral disease in the world. The main treatment to restore caries lesions consists of the use of adhesive resin composites due to their good properties. However, the progressive degradation of the adhesive in the medium term makes possible the proliferation of cariogenic bacteria allowing secondary caries to emerge. In this study, a dental adhesive incorporating a drug delivery system based on L-arginine-containing mesoporous silica nanoparticles (MSNs) was used to release this essential amino acid as a source of basicity to neutralize the harmful acidic conditions that mediate the development of dental secondary caries. The in vitro and bacterial culture experiments proved that L-arginine was released in a sustained way from MSNs and diffused out from the dental adhesive, effectively contributing to the reduction of the bacterial strains Streptococcus mutans and Lactobacillus casei. Furthermore, the mechanical and bonding properties of the dental adhesive did not change significantly after the incorporation of L-arginine-containing MSNs. These results are yielding glimmers of promise for the cost-effective prevention of secondary caries.

Dental emergency care in Spain during the state of alarm due to COVID-19 pandemic

Background

The first state of alarm due to COVID-19 in Spain led to limit dental treatment exclusively to emergencies. The objective of the survey was to evaluate the amount and type of emergencies attended during this period, as well as to know how they were solved, and what measures were adopted to carry out dental care in these exceptional circumstances.

Material and Methods

This cross-sectional study included 312 Spanish dentists, who fulfilled an online questionnaire with 22 closed questions, divided into five sections regarding to various aspects of professional dental profile and emergency care. Descriptive statistic and Chi-square tests were performed (p<0.05).

Results

75.64% of respondents attended emergencies in person only when required, being dental pain the main emergency (90.38%). Dental emergency care in person involved a prior telephone triage of the patient to identify possible COVID-19 symptoms, as well as protective measures implementation for both, the patient and the dentist, at dental office.

Conclusions

The number of dental emergencies decreased during the state of alarm, being dental pain the main cause of dental assistance via telephone or in person. Triage of patients before scheduling an in-person appointment and protective measures implementation were common features in dental emergency care during the first state of alarm period.

Key words:Dental emergencies, COVID-19, state of alarm, survey.

Effect of a hydrophobic bonding resin on the 36-month performance of a universal adhesive-a randomized clinical trial

OBJECTIVES

To evaluate if the addition of a layer of a hydrophobic bonding resin to the recommended application sequence of a universal adhesive improves the respective clinical behavior in non-carious cervical lesions (NCCLs) after 36 months.

MATERIALS AND METHODS

Scotchbond Universal Adhesive (SBU, 3M Oral Care) was applied in NCCLs of 39 subjects using four adhesion strategies: (1) three-step ER (etch-and-rinse), (2) two-step ER, (3) two-step SE (self-etch), and (4) one-step SE. An extra layer of a hydrophobic bonding resin was applied for strategies three-step ER and two-step SE. The same composite resin (Filtek Supreme XTE, 3M Oral Care) was used for all strategies. Restorations were evaluated at baseline and 18 and 36 months using the modified United States Public Health Service (USPHS) criteria. Kruskal-Wallis, Mann-Whitney U, Friedman, and Wilcoxon non-parametric tests were computed.

RESULTS

The cumulative failure rate was 8.6%. The 36-month retention rates were 100% for both 3-ER and 2-ER, 76.0% for 2-SE, and 86.2% for 1-SE. A lower retention rate was observed for two-step SE at 36 months compared with both three-ER (p < 0.01) and two-ER (p < 0.01). Identical retention rates were measured for the two SE groups. When retention rate was compared at baseline versus 36 months for each adhesion strategy, a significant decrease was observed for 2-SE. The restorations performed with 3-ER, 2-SE, and 1-SE had a significant deterioration in marginal discoloration at the 18-month recall.

CONCLUSIONS

The 36-month clinical performance of Scotchbond Universal Adhesive improved for both etch-and-rinse strategies.

CLINICAL RELEVANCE

Phosphoric acid etching is still recommended to provide retention to composite restorations in NCCLs.

Clinical Evaluation of a Low-shrinkage Composite in Posterior Restorations: One-Year Results

Objectives

The aim of this study was to compare the one-year clinical performance of three restorative systems, which included a novel low-shrinkage composite and two bonding strategies.

Materials and Methods

Twenty-five patients received three Class I (occlusal) or Class II restorations performed with one of three restorative systems: Filtek Silorane Restorative System (FS); Adper Scotchbond 1 XT, a two-step etch-and-rinse adhesive, with Filtek Z250 (XT); and Adper Scotchbond SE, a two-step self-etch adhesive, with Filtek Z250 (SE). All materials were applied following the manufacturer's instructions. Two independent observers evaluated the restorations at baseline, after six months, and after one year, according to the United States Public Health System modified criteria. The Kruskal-Wallis test and the Mann-Whitney U-test were computed to compare the behavior of the restorative systems; Friedman and Wilcoxon tests were used to analyze the intrasystem data (α=0.05).

Results

All restorations were evaluated at one year. FS and XT performed statistically similarly at one year, but marginal staining for SE was statistically worse. Intrasystem comparisons between baseline and one year also showed deterioration of marginal staining for SE, while a deterioration of the marginal adaptation was recorded for both SE and FS. XT was the only system for which there was no statistical change of the parameters measured in this study.

Conclusions

Both restorative systems using self-etch adhesives showed a tendency to degradation of marginal adaptation after one year of clinical use, compared to baseline values. Although the clinical performance of FS was deemed acceptable after one year, this study did not find any advantage of the silorane-based composite over the methacrylate-based composite. The low-shrinkage associated with FS may not be a determinant factor for clinical success.

Biofiltration of composting gases using different municipal solid waste-pruning residue composts: monitoring by using an electronic nose

The concentration of volatile organic compounds (VOCs) during the composting of kitchen waste and pruning residues, and the abatement of VOCs by different compost biofilters was studied. VOCs removal efficiencies greater than 90% were obtained using composts of municipal solid waste (MSW) or MSW-pruning residue as biofilter material. An electronic nose identified qualitative differences among the biofilter output gases at very low concentrations of VOCs. These differences were related to compost constituents, compost particle size (2-7 or 7-20mm), and a combination of both factors. The total concentration of VOCs determined by a photoionization analyser and inferred from electronic nose data sets were correlated over an ample range of concentrations of VOCs, showing that these techniques could be specially adapted for the monitoring of these processes.

Organotin contamination in the Atlantic Ocean off the Iberian Peninsula in relation to shipping

Imposex in female snails, a bioindicator of TBT contamination, and the presence of organotins in snails' tissue and sediments were studied at nine sites off the western Iberian Peninsula. The study was part of a European project (acronym HIC-TBT) co-financed by the EU-LIFE programme, intending to investigate and communicate the impact of organotins from ships in marine ecosystems. Snails and sediments were sampled during two cruises in May/June 1999 and in January 2000 in areas of high, intermediate and low-shipping density. Imposex was found in female snails from several sampling sites, some of which had an imposex incidence of 100%. Differences in sensitivity were found between species; hence comparison of imposex levels between locations where different species were collected was not straightforward. Total organotin concentrations in sediments (sum of butyl and phenyltin compounds) ranged from 21 to 185 ng Sn g(-1) with higher values for most sites sampled in the vicinity of shipping lanes. Organotin concentration in snails' tissue ranged from <5 to 196 ng Sn g(-1), which are similar to those found in snails from other offshore areas contaminated by TBT. Overall, these results give further support to the recent ban on the use of organotin based antifouling paints to all ship size.

Determination of polychlorinated biphenyls in biota samples using simultaneous pressurized liquid extraction and purification

In order to reduce time and cost of analysis, a new pressurised liquid extraction method that automatically and rapidly achieves quantitative and selective (i.e., lipid-free) extraction of polychlorinated biphenyls (PCBs) in biota tissues was optimized. It consists of on-line clean-up by inclusion of sorbents in the extraction cell. The freeze-dried sample is dispersed with Florisil and loaded in the extraction cell containing an extra amount of Florisil. The extraction is performed under mild conditions using 55 ml of a dichloromethane-pentane (15:85) mixture, a temperature of 40 degrees C, a static extraction time of 10 min and two extraction cycles. The Florisil retains coextracted lipids from the matrix, and the extract, after pre-concentration, is clean enough for direct injection into GC-MS and GC-electron-capture detection (ECD). Quantitative recoveries (from 90 to 106%) are obtained for both native and spiked PCB congeners in samples with a high lipidic content (up to 42% dry mass, in spoonbill eggs). The reproducibility of replicate extractions was better than 11% relative standard deviation. Method detection limits were in the ranges of 0.001-0.004 and 0.002-0.07 ng g(-1) dry mass for GC-ECD and GC-MS-MS, respectively. The method was validated using the standard reference material SRM 2974 (a mussel tissue) from the US National Institute of Standards and Technology, compared to Soxhlet and matrix solid-phase dispersion extraction methods, and used to evaluate the contamination by PCBs in bivalves from South of Spain.

Sample treatment in chromatography-based speciation of organometallic pollutants

Speciation analysis is nowadays performed routinely in many laboratories to control the quality of the environment, food and health. Chemical speciation analyses generally include the study of different oxidation state of elements or individual organometallic compounds. The determination of the different chemical forms of elements is still an analytical challenge, since they are often unstable and concentrations in different matrices of interest are in the microg l(-1) or even in the ng l(-1) range (e.g., estuarine waters) or ng g(-1) in sediments and biological tissues. For this reason, sensitive and selective analytical atomic techniques are being used as available detectors for speciation, generally coupled with chromatography for the time-resolved introduction of analytes into the atomic spectrometer. The complexity of these instrumental couplings has a straightforward consequence on the duration of the analysis, but sample preparation to separate and transfer the chemical species present in the sample into a solution to be accepted readily by a chromatographic column is the more critical step of total analysis, and demands considerable operator skills and time cost. Traditionally, liquid-liquid extraction has been employed for sample treatment with serious disadvantages, such as consumption, disposal and long-term exposure to organic solvent. In addition, they are usually cumbersome and time-consuming. Therefore, the introduction of new reagents such as sodium tetraethylborate for the simultaneous derivatization of several elements has been proposed. Other possibilities are based in the implementation of techniques for efficient and accelerated isolation of species from the sample matrix. This is the case for microwave-assisted extraction, solid-phase extraction and microextraction, supercritical fluid extraction or pressurized liquid extraction, which offer new possibilities in species treatment, and the advantages of a drastic reduction of the extraction time and the embodiment into on-line flow analysis systems. This new generation of treatment techniques constitutes a good choice as fast extraction methods for feasible species-selective analysis of organometallic compounds under the picogram level, that can be used for national regulatory agencies, governmental and industrial quality control laboratories, and consequently, for manufacturers of analytical instrumentation.

Column-switching system for selenium speciation by coupling reversed-phase and ion-exchange high-performance liquid chromatography with microwave-assisted digestion-hydride generation-atomic fluorescence spectrometry

Speciation of selenocysteine (SeCys), selenomethionine (SeMet), selenoethionine (SeET), selenite (Se(IV)) and selenate (Se(VI)) has been accomplished using high-performance liquid chromatography, with the aid of an anion exchange column and a reversed-phase column, both connected through a six-port switching valve. On-line microwave-assisted digestion and hydride generation steps were performed prior to the atomic fluorescence detection. The elution of the seleno amino acids was accomplished in the reversed-phased column using water as mobile phase. Selenite and selenate were separated in the anion exchange column, using gradient elution with an acetate buffer. The separation of the five selenium compounds took place in 15 min. The detection limits obtained ranged between 0.6 and 0.9 microg l(-1). Values of r>0.998 were obtained for linear fit graphs. A commercial available urine sample was analyzed, in which SeCys and Se(IV) were quantified.

Temporal fluctuations of tributyltin in the bivalve Venerupis decussata at five stations in southwest Spain

Filter feeding clams, Venerupis decussata, were sampled every 4 months for 8 years at five locations on the southwest Spain coast and analysed for organotins. All the stations showed a significant sinusoidally shaped seasonal evolution pattern for tributyltin (TBT) superimposed upon a linear decreasing tendency. The amplitude and frequency of fluctuations differed among stations and were correlated to the harbour activities. Fluctuations were greatest at stations with the greatest TBT presence. The long-term trend of TBT in clams indicated half-life values of about 7-14 years. During 1993, water and sediment samples were also collected at monthly intervals and analysed. Correlations between TBT bivalve contents and water concentrations were higher than those found between biota and sediments.

Comparison of the feasibility of three extraction procedures for trace metal partitioning in sediments from south-west Spain

The feasibility of three sequential extraction schemes (a modification of the Tessier procedure, the scheme proposed by Meguellati and the protocol designed by BCR (now called the Standards, Measurements and Testing Programme, M&T) have been compared to study the distribution of As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn in sediment samples. The comparison has been performed by analyzing Certified Reference Material (CRM-601), a test material (S-12) and seven sediments from the Odiel Marshes Natural Park (located at the Atlantic coast of southern Spain). Samples were classified as sandy (with low iron oxide and organic matter contents) and clay-silty (with high iron oxide and organic matter contents) sediments. A higher metal mobility, especially under reducing conditions, was more properly assessed using the modified Tessier scheme compared to both the BCR and Meguellati procedures, these two later presenting comparative results for the reducible and residual phases. Significant Hg losses were found using the BCR procedure but the quantification of the acid phase for Cd, Cr and Ni was more reliable than that obtained with the modified Tessier and Meguellati schemes.

A comparison between ICP-MS and AFS detection for arsenic speciation in environmental samples

Performances of two atomic detectors, Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Atomic Fluorescence Spectrometry (AFS) have been compared for arsenic speciation in environmental samples. Instrumental couplings, based on the use of high performance liquid chromatography (HPLC), hydride generation (HG), and the two atomic detectors were used for the speciation of arsenite, arsenate, dimethylarsinic acid and monomethylarsonic acid. Optionally, arsenobetaine was also determined using on-line ultraviolet (UV) photooxidation. The detection limits ranging from 0.1 to 0.3 mug l(-1) (as As) and the precision >10% RSD obtained with HPLC-(UV)-HG-AFS were comparable with those obtained with HPLC-(UV)-HG-ICP-MS. Both instrumental coupling were applied to the NRCC-TORT-1 and several environmental samples, such as seawater, freshwater, sediments, bivalves and bird eggs, taken from two areas with different degrees of pollution. No influence of the sample matrix was observed on the results using external calibration and standard additions methods, for both coupled techniques.

Determination of dialkyldiselenides in water by gas chromatography-mass spectrometry using 1-fluoro-2,4-dinitrobenzene as derivatization reagent

The feasibility of gas chromatography-mass spectrometry for the speciation of traces of dialkyldiselenides in the presence of dialkylselenides and inorganic selenium species is described, and the procedure is applied to environmental samples. The analysis is based on the reaction of dialkyldiselenide species with 1-fluoro-2,4-dinitrobenzene after volatilization of selenium species as alkylselenols using a volatilization and trap device. Parameters affecting the volatilization and derivatization of the selenium compounds are discussed, and the performance of the method is described. The approach reaches detection limits in the order of nanograms (after a preconcentration step) and has been applied to the analysis of dimethyldiselenium and diethyldiselenium in natural waters.

Stability and storage problems in organotin speciation in environmental samples

The stability of both tributyltin (TBT) and triphenyltin (TPT) in water, sediment, oysters and cockles was studied over a period of 18 months using several storage conditions. Butyltins were stable in unacidified sea-water stored in polycarbonate bottles in the dark at 4 degrees C for 7 months, but half of the TBT concentration was lost after 540 d. A comparable preservation time was achieved for butyltins stored on C18 cartridges at room temperature. However, phenyltins extracted from sea-water were stable for only 60 d stored on cartridges and even more pronounced losses (about 90% after 540 d) occurred when they were stored in either polycarbonate or Pyrex glass bottles. Losses of organotins were observed in sediments after air drying and pasteurization treatments using a freeze-dried sediment as a comparator, whereas both butyltin and phenyltin species remained stable in sediments stored at -20 degrees C for the 18 months tested, irrespective of the treatment used for stabilization. Air drying followed by pasteurization was shown to be superior to other treatments for the stabilization of organotin compounds in sediments stored at higher temperatures, but 30% of TBT was lost after 540 d at 25 degrees C. Finally, butyltins were stable in both frozen cockles and oysters in the dark over a 7 month period and in freeze-dried samples stored at 4 degrees C for 5 months, but TBT losses of about 70% were observed after 540 d.