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1.
J Oral Pathol Med ; 53(6): 358-365, 2024 Jul.
Article in English | MEDLINE | ID: mdl-38745372

ABSTRACT

BACKGROUND: To assess the influence of diagnosis and referral provided by specialists in oral diagnosis on disease-free survival and overall survival of patients with oral cancer. METHODS: A cohort of 282 patients with oral cancer treated at a regional cancer hospital from 1998 to 2016 was analyzed retrospectively. The referral register of the patients was analyzed and assigned to two groups: (1) those referred by oral diagnosis specialists (n = 129), or (2) those referred by nonspecialized professionals (n = 153). The cancer treatment evolution was assessed from the patients' records, and the outcome was registered concerning cancer recurrence and death. Sociodemographic and clinicopathological variables were explored as predictors of disease-free survival and overall survival. RESULTS: Group 1 exhibited lower T stages and a reduced incidence of regional and distant metastases. Surgery was performed in 75.2% of cases in Group 1, while in Group 2, the rate was 60.8%. Advanced T stages and regional metastases reduced the feasibility of surgery. Higher TNM stages and tumor recurrence were associated with decreased disease-free survival, while surgical intervention was a protective factor. Higher TNM stage had a negative impact on the overall survival. CONCLUSION: Specialized oral diagnosis did not directly impact disease-free survival and overall survival and did not influence the indication of surgery in oral cancer; however, it was associated with the diagnosis of early tumors and better prognosis.


Subject(s)
Mouth Neoplasms , Referral and Consultation , Humans , Mouth Neoplasms/pathology , Mouth Neoplasms/mortality , Mouth Neoplasms/therapy , Retrospective Studies , Male , Female , Middle Aged , Aged , Survival Rate , Neoplasm Staging , Neoplasm Recurrence, Local , Disease-Free Survival , Adult , Cohort Studies , Aged, 80 and over , Diagnosis, Oral
2.
Environ Technol ; : 1-12, 2024 Mar 06.
Article in English | MEDLINE | ID: mdl-38449387

ABSTRACT

Incidents of mining dam failure have compromised the water quality, threatening the water supply. Different strategies are sought to restore the impacted area and to guarantee the water supply. One example is water treatment plants that treat high-polluted waters within the required limits for their multiple usages. The current study assesses the integration of reverse osmosis (RO) to a river water treatment plant (RWTP) installed in Brumadinho (Minas Gerais, Brazil) to treat the water from the Ferro-Carvão stream impacted by the B1 dam rupture in 2019. The RWTP started eleven months after the mining dam rupture and is equipped with eight coagulation-flocculation tanks followed by eight pressurised filters. A pilot RO plant was installed to polish the water treated by the RWTP. Water samples were collected at different points of the water treatment plant and were characterised by their physical, chemical, and biological parameters (160 in total). The results were compared with the historical data (1997-2022) to reveal the alterations in the water quality after the rupture event. The compliance with both parameters was only achieved after the RO treatment, which acted as an additional barrier to 30 contaminants. The water quality indexes (WQI) suggested that the raw surface water, even eleven months after the incident, was unfit for consumption (WQI: 133.9) whereas the reverse osmosis permeate was ranked as excellent in the rating grid (WQI: 23.7).

3.
J Environ Manage ; 351: 119772, 2024 Feb.
Article in English | MEDLINE | ID: mdl-38147771

ABSTRACT

Phenolic compounds are one of the main contributors to water source contamination worldwide. In this review, the data collected on Elsevier, Scopus, and Pubmed, considering papers published between 2000 and 2023, showed more than 60 different phenols have been identified in water matrix (<0.065-179,000,000 ng L-1). The highest concentration reported was in surface water canals in India. The most recurrent and studied compound was bisphenol A (n = 93) in concentrations ranging from 0.45 to 2,970,000 ng L-1. The solid phase extraction (HBL Oasis cartridge) and methanol as solvent was the method of pre-concentration most used followed by gas chromatography for the determination of phenols in water samples. The importance of drinking water guidelines incorporating more phenolic compounds was emphasized given the variety of these compounds quantified in water matrix. The human health risk assessment (HRA) was performed for the min-max concentrations of the pollutants reported in the literature. High HRA even at the lowest concentrations for 2-nitrophenol, 2,6-dichlorophenol, 3,4,5-trichlorophenol, 2,3,4,6-tetrachlorophenol, and 2,4-dinitrophenol was recognized. The cancer risk estimated was considered possible for 3-methylphenol, 2,4-dimethylphenol, 2,4,6-trichlorophenol, pentachlorophenol, and 2,4-dinitrophenol in the highest concentrations. The in-depth discussion of mechanisms, advantages, challenges, and carbon footprint of membrane technologies in water treatment and phenols retention demonstrated the great potential and trends for the production of safe drinking water, highlighting reverse osmosis, as a mature technology, and membrane distillation, as an emergent technology.


Subject(s)
Drinking Water , Water Pollutants, Chemical , Humans , 2,4-Dinitrophenol/analysis , Water Pollutants, Chemical/analysis , Phenols/analysis , Technology
4.
Neotrop Entomol ; 52(6): 1155-1164, 2023 Dec.
Article in English | MEDLINE | ID: mdl-37861966

ABSTRACT

Neurotoxicant compounds interfere with the behaviour and biology of insects, significantly altering their locomotion patterns. However, little is known about the effect of organophosphates, neurotoxicants for agricultural, domestic and industrial use, on the larval movement of necrophagous flies, although being responsible for frequent cases of poisoning and accidental or intentional deaths. Thus, we aimed to study the influence of Terbufos (organophosphate) on the activity and mobility patterns of Lucilia eximia (Wiedemann 1819) (Calliphoridae) and Peckia (Peckia) chrysostoma (Wiedemann 1830) (Sarcophagidae) immatures collected from rat carcasses intoxicated with 5, 10 or 20 mg/kg of Terbufos, to evaluate (i) peristaltic movements and body contractions, and (ii) distance and shape of the trajectory travelled by the larva. Behavioural parameters were analysed in loco and through videos. We observed that the presence of Terbufos altered poisoned larvae's activity and body mobility in both taxon and dose-dependent manner. Lucilia eximia larvae were more active, with greater frequency of body movements and lateral contractions when intoxicated with high and intermediate doses of Terbufos. On the other hand, P. (P.) chrysostoma immatures were less active, with fewer body and lateral contractions when intoxicated with the high dose of the compound. This work experimentally demonstrates that the presence of Terbufos can alters the mobility and movement of intoxicated necrophagous Diptera, essential components of the cadaveric fauna.


Subject(s)
Diptera , Sarcophagidae , Humans , Animals , Rats , Organophosphates , Larva , Calliphoridae
6.
Leuk Lymphoma ; 64(11): 1771-1781, 2023.
Article in English | MEDLINE | ID: mdl-37462418

ABSTRACT

Altered metabolic fingerprints of Diffuse large B-cell lymphoma, not otherwise specified (DLBCL NOS) may offer novel opportunities to identify new biomarkers and improve the understanding of its pathogenesis. This study aimed to investigate the modified metabolic pathways in extranodal, germinal center B-cell (GCB) and non-GCB DLBCL NOS from the head and neck. Formalin-fixed paraffin-embedded (FFPE) tissues from eleven DLBCL NOS classified according to Hans' algorithm using immunohistochemistry, and five normal lymphoid tissues (LT) were analyzed by high-performance liquid chromatography-mass spectrometry-based untargeted metabolomics. Partial Least Squares Discriminant Analysis showed that GCB and non-GCB DLBCL NOS have a distinct metabolomics profile, being the former more similar to normal lymphoid tissues. Metabolite pathway enrichment analysis indicated the following altered pathways: arachidonic acid, tyrosine, xenobiotics, vitamin E metabolism, and vitamin A. Our findings support that GCB and non-GCB DLBCL NOS has a distinct metabolomic profile, in which GCB possibly shares more metabolic similarities with LT than non-GCB DLBCL NOS.


Subject(s)
Biomarkers, Tumor , Lymphoma, Large B-Cell, Diffuse , Humans , Biomarkers, Tumor/metabolism , Lymphoma, Large B-Cell, Diffuse/pathology , B-Lymphocytes/metabolism , Germinal Center/metabolism , Metabolic Networks and Pathways , Prognosis
7.
J Environ Manage ; 344: 118506, 2023 Oct 15.
Article in English | MEDLINE | ID: mdl-37418920

ABSTRACT

One of the impacts related to mining dam failures is the change in water quality downstream of the rupture and a knowledge gap is observed in terms of methodologies aimed at the prognosis of impact in water abstractions, a vulnerability that can be identified before a rupture event. Thus, the present work aims to describe a novel methodological proposal, not currently considered by control agencies, of a standard protocol that enables a comprehensive prognosis of the impacts on water quality impact in scenarios of dam failure. Initially, extensive bibliographic research was carried out on the main disruptions events since 1965 intended to better comprehend the impacts on water quality and to identify mitigatory actions proposed by the time. The information provided a framework to propose a conceptual model for the prognosis of water abstractions, with the suggestion of software and studies to comprehend the different scenarios in the event of dam failure. A protocol was prepared to obtain information on potentially affected inhabitants and a multicriteria analysis was developed using the Geographic Information System (GIS) to suggest the employment of preventive and corrective actions. The methodology was demonstrated in the Velhas River basin considering a hypothetical scenario of tailing dam failure. Changes in water quality would be observed in 274 km of its extension, mainly related to alterations in solids, metals, and metalloids' concentration, in addition to the impact on important water treatment plants. The map algebra and the results suggest the need for structuring actions in cases where the water abstraction is intended for human supply and in populations greater than 100,000 inhabitants. Populations smaller than these, or usages other than human supply, could be supplied by water tank trucks or mixed alternatives. The methodology pointed out the necessity for structuring supply actions with due notice, with the potential to prevent water shortages in scenarios of tailing dam failure and to complement the enterprise resource planning of mining companies.


Subject(s)
Metals , Water Pollutants, Chemical , Humans , Metals/analysis , Rivers , Water Quality , Environmental Monitoring , Water Pollutants, Chemical/analysis
8.
Sci Rep ; 13(1): 10343, 2023 Jun 26.
Article in English | MEDLINE | ID: mdl-37365221

ABSTRACT

We study the room-temperature electrical control of charge and spin transport in high-quality bilayer graphene, fully encapsulated with hBN and contacted via 1D spin injectors. We show that spin transport in this device architecture is measurable at room temperature and its spin transport parameters can be modulated by opening of a band gap via a perpendicular displacement field. The modulation of the spin current is dominated by the control of the spin relaxation time with displacement field, demonstrating the basic operation of a spin-based field-effect transistor.

9.
Nano Lett ; 22(23): 9566-9570, 2022 Dec 14.
Article in English | MEDLINE | ID: mdl-36449567

ABSTRACT

Recent experiments demonstrated that interfacial water dissociation (H2O ⇆ H+ + OH-) could be accelerated exponentially by an electric field applied to graphene electrodes, a phenomenon related to the Wien effect. Here we report an order-of-magnitude acceleration of the interfacial water dissociation reaction under visible-light illumination. This process is accompanied by spatial separation of protons and hydroxide ions across one-atom-thick graphene and enhanced by strong interfacial electric fields. The found photoeffect is attributed to the combination of graphene's perfect selectivity with respect to protons, which prevents proton-hydroxide recombination, and to proton transport acceleration by the Wien effect, which occurs in synchrony with the water dissociation reaction. Our findings provide fundamental insights into ion dynamics near atomically thin proton-selective interfaces and suggest that strong interfacial fields can enhance and tune very fast ionic processes, which is of relevance for applications in photocatalysis and designing reconfigurable materials.

10.
Chemosphere ; 309(Pt 1): 136618, 2022 Dec.
Article in English | MEDLINE | ID: mdl-36181845

ABSTRACT

With dam failure events, there can be changes in water quality and difficulties in the operation of water treatment plants (WTPs) since they were not designed for water treatment under severe pollution conditions. To avoid that, it was investigated two strategies based on pre-oxidation, ultrafiltration (UF) and reverse osmosis (RO) integrated into a conventional treatment process (coagulation, flocculation, and sand filtration) or with each other, with the potential to reduce the risks of drinking water shortage and guarantee a safe drinking water supply. The study considered the context of the Velhas river basin (Brazil), where water quality is compromised by high turbidities (500-3000 NTU) and excessive arsenic (∼0.4 mg/L), iron (∼50 mg/L), and manganese (∼3 mg/L) levels. They were only partially removed by conventional treatments (removals: 74 ± 21%) and potability standards were only achieved after the membrane separation processes were considered (As: <0.01 mg/L, Mn: <0.1 mg/L, and Fe: <0.3 mg/L). The high water quality after RO enables its blend with the stream obtained after sand filters and would allow for greater flexibility during the operation of WTPs operation. Despite the susceptibility to fouling and most frequent maintenance, the pre-oxidation-UF-RO system would also guarantee a safe drinking water supply. The decision for the most adequate strategy was then based on a multicriteria analysis. A retrofit of conventional WTPs by their integration with UF-RO was classified as the best strategy for centralized facilities, whereas pre-oxidation-UF-RO better fits the reality of decentralized treatments given the lower costs and deployment time. The methodology based on multicriteria analysis and water treatment technologies, exemplified by membranes in this study, presented satisfactory results for different scenarios of critical treatment.


Subject(s)
Arsenic , Drinking Water , Water Purification , Osmosis , Membranes, Artificial , Manganese , Ultrafiltration/methods , Filtration/methods , Water Purification/methods , Technology , Iron
11.
Sci Total Environ ; 852: 158536, 2022 Dec 15.
Article in English | MEDLINE | ID: mdl-36075437

ABSTRACT

Tailings dams have been built since 3000 BCE and despite the advancement of construction methods, mainly in the second half of the 21st century, their ruptures were still recorded. The main direct impacts are related to the loss of human lives, impairment of physical structures and changes in water quality. In this review, different dam failure events were critically analyzed considering their social and environmental impacts, besides the gaps in current regulations framework to appropriately charge the companies involved. These aspects differ the current review paper from those currently available, which also present advancements in the discussion of actions taken after the ruptures, the impacts on water quality, and the challenges related to the water supply. It has been noticed a lack of studies and methodologies capable to predict the water quality under scenarios of tailings contamination. Studies covering that aspect would be an important tool for planning emergency responses by stakeholders. With that in mind, the article discloses the pathway toward an effective strategy in scenarios of tailing dam failure that would mitigate the impacts on water quality and guarantee access to safe water.


Subject(s)
Water Quality , Water Supply , Humans , Environment , Rivers/chemistry
12.
Chemosphere ; 306: 135591, 2022 Nov.
Article in English | MEDLINE | ID: mdl-35798155

ABSTRACT

Despite the widespread use of membrane separation processes for water treatment, operation costs and fouling still restrict their application. Costs can be overcome by recycled membranes whereas fouling can be mitigated by membrane modification. In this work, the performance of recycled reverse osmosis membranes modified by greener titanium dioxide (TiO2) and graphene oxide (GO) in different modification routes were investigated and compared. The use of recycled membranes as a support acted more than a strategy for costs reduction, but also as an alternative for solid waste reduction. Low adhesion of nanoparticulate materials to the membrane surfaces were verified in depositions by self-assembly, whereas filtration and modification with dopamine generated membranes with well adhered and homogeneous layers. Considering the stability, permeability, and rejection efficiency of dyes as model substrates, the membranes modified with the aid of dopamine-TiO2-GO were the most promising. The nanomaterials increased the membrane hydrophilicity and formed a hydrated layer that repels the organic contaminants and reduces fouling. Besides membrane rejection, adsorption (contribution: ∼10%) and photocatalysis (contribution: ∼20%) were additional mechanisms for pollutants removal by the modified membranes. The photocatalytic membrane modified with dopamine-TiO2-GO was furthermore evaluated for the removal of six different pharmaceutical active compounds (PhACs), noticing gains in terms of removal efficiency (up to 95.7%) and fouling mitigation for the modified membrane compared to the original membranes. The photocatalytic activity still contributed to a simultaneous degradation of PhACs avoiding the generation of a concentrated stream for further disposal.


Subject(s)
Membranes, Artificial , Nanostructures , Dopamine , Graphite , Titanium/chemistry
13.
J Oral Pathol Med ; 51(7): 666-673, 2022 Aug.
Article in English | MEDLINE | ID: mdl-35706152

ABSTRACT

BACKGROUND: Giant cell granuloma of the jaws are benign osteolytic lesions of the jaws. These lesions are genetically characterized by mutually exclusive somatic mutations at TRPV4, KRAS, and FGFR1, and a fourth molecular subgroup which is wild-type for the three mutations. Irrespective of the molecular background, giant cell granulomas show MAPK/ERK activation. However, it remains unclear if these mutations lead to differences in their molecular signaling in giant cell granulomas. METHODS: Metabolomics, proteomics, and phosphoproteomics analyses were carried out in formalin-fixed paraffin-embedded samples of giant cell granuloma of the jaws. The study cohort consisted of five lesions harboring mutations in FGFR1, six in KRAS, five in TRPV4, and five that were wild-type for these mutations. RESULTS: Lesions harboring KRAS or FGFR1 mutations showed overall similar proteomics and metabolomics profiles. In all four groups, metabolic pathways showed similarity in apoptosis, cell signaling, gene expression, cell differentiation, and erythrocyte activity. Lesions harboring TRPV4 mutations showed a greater number of enriched pathways related to tissue architecture. On the other hand, the wild-type group presented increased number of enriched pathways related to protein metabolism compared to the other groups. CONCLUSION: Despite some minor differences, our results revealed an overall similar molecular profile among the groups with different mutational profile at the metabolic, proteic, and phosphopeptidic levels.


Subject(s)
Granuloma, Giant Cell , TRPV Cation Channels , Granuloma, Giant Cell/genetics , Granuloma, Giant Cell/metabolism , Humans , Jaw/metabolism , Jaw/pathology , Metabolomics , Mutation , Proteomics , Proto-Oncogene Proteins p21(ras)/genetics , Proto-Oncogene Proteins p21(ras)/metabolism , TRPV Cation Channels/genetics , TRPV Cation Channels/metabolism
14.
Nano Lett ; 22(3): 935-941, 2022 Feb 09.
Article in English | MEDLINE | ID: mdl-35089714

ABSTRACT

Spintronics involves the development of low-dimensional electronic systems with potential use in quantum-based computation. In graphene, there has been significant progress in improving spin transport characteristics by encapsulation and reducing impurities, but the influence of standard two-dimensional (2D) tunnel contacts, via pinholes and doping of the graphene channel, remains difficult to eliminate. Here, we report the observation of spin injection and tunable spin signal in fully encapsulated graphene, enabled by van der Waals heterostructures with one-dimensional (1D) contacts. This architecture prevents significant doping from the contacts, enabling high-quality graphene channels, currently with mobilities up to 130 000 cm2 V-1 s-1 and spin diffusion lengths approaching 20 µm. The nanoscale-wide 1D contacts allow spin injection both at room and at low temperature, with the latter exhibiting efficiency comparable with 2D tunnel contacts. At low temperature, the spin signals can be enhanced by as much as an order of magnitude by electrostatic gating, adding new functionality.

15.
J Environ Manage ; 303: 114117, 2022 Feb 01.
Article in English | MEDLINE | ID: mdl-34838381

ABSTRACT

Membrane distillation is a well-established technology for non-volatile components retention, but the removal of volatile and semi-volatile substances in trace concentration, such as phenols derivates commonly found in surface waters, requires further comprehension. In this context, the direct contact membrane distillation (DCMD) performance was assessed for the retention of fifteen phenolic compounds in surface water by different operating conditions of temperature (40, 50, and 60 °C), feed concentration (3, 5, 7, and 10 µg L-1), and permeate recovery rate (30, 50 and 70%). Kruskal Wallis confirmed a significant difference (p < 0.05) between the global removal of phenolic compounds at different temperatures. The increase in temperature led to a reduction in all compound's removal. As expected, a positive correlation (rSpearman>0.8) between the compounds' volatility and their losses was observed. Regarding the feed concentration and the recovery rate, there was no statistical difference between the removal values obtained for the phenolic compounds. This indicates the DCMD strength for that application. However, a trend for flux decay was noticed as the recovery rate (RR) increased, confirmed by temporal trend analysis and Mann-Kendall tests, although the flux decay was relatively low (J/J0 = 0.89). Aiming for a greater removal and to avoid a reduction in process performance, it is recommended to work with 40 °C as feed temperature and a RR prior to the flux decay (RR<30%). Nonetheless, the technology was efficient and did not compromise the permeate quality with >90% efficiency in pollutants removal, even for higher temperatures and RR.


Subject(s)
Distillation , Water Purification , Membranes , Membranes, Artificial , Phenols
16.
Oral Dis ; 28(8): 2219-2229, 2022 Nov.
Article in English | MEDLINE | ID: mdl-33978981

ABSTRACT

OBJECTIVE: We aimed to assess which metabolic pathways would be implicated in the phenotypic changes of the epithelial lining of odontogenic keratocyst after marsupialization, comparing pre- and post-marsupialized lesions with adjacent oral mucosa. MATERIALS AND METHODS: Eighteen formalin-fixed and paraffin-embedded tissues from six subjects were divided into three paired groups: odontogenic keratocyst pre- (n = 6) and post-marsupialization (n = 6), and adjacent oral mucosa (n = 6). The metabolic pathways found in these groups were obtained by high-performance liquid chromatography-mass spectrometry-based untargeted metabolomics performed. RESULTS: Through putative metabolite annotation followed by pathway enrichment and predictive analysis with automated algorithms (Mummichog and Gene Set Enrichment Analysis), we found differences in many cellular processes that may be involved in inflammation, oxidative stress response, keratinocyte-basal membrane attachment, differentiation, and proliferation functions, all relevant to odontogenic keratocyst pathobiology and the phenotype acquired after marsupialization. CONCLUSION: Our study was able to identify several metabolic pathways potentially involved in the metaplastic changes induced by marsupialization of odontogenic keratocysts. An improved comprehension of this process could pave the way for the development of targeted therapies.


Subject(s)
Odontogenic Cysts , Odontogenic Tumors , Formaldehyde , Humans , Odontogenic Cysts/pathology , Odontogenic Cysts/surgery , Pilot Projects
17.
Bioresour Technol ; 343: 126150, 2022 Jan.
Article in English | MEDLINE | ID: mdl-34678454

ABSTRACT

Several studies have investigated the removal of pharmaceutically active compounds (PhACs) by wastewater treatment technologies due to the risk that these compounds pose to the environment. In this sense, advanced biological processes have been developed for micropollutants removal, such as membrane bioreactors and moving bed biofilm reactors. Thus, this review holistically evaluated the biodegradation of 18 environmentally hazardous PhACs. Biological processes were assessed including removal efficiencies, environmental risk, and ecological footprint (consumption of resources and energy, atmospheric emissions, and waste generation). The maximum concentration of PhACs for a low or negligible risk scenario in treated wastewater and the potential of biological processes to meet this goal were assessed. Among the evaluated PhACs, the most biodegradable was paracetamol, while the most recalcitrant was diclofenac. Combination of conventional processes and advanced biological processes proved to be the most efficient way to remove several PhACs, mainly the osmotic membrane bioreactor.


Subject(s)
Pharmaceutical Preparations , Water Pollutants, Chemical , Water Purification , Risk Assessment , Waste Disposal, Fluid , Wastewater , Water Pollutants, Chemical/analysis
18.
Environ Sci Pollut Res Int ; 29(11): 16203-16212, 2022 Mar.
Article in English | MEDLINE | ID: mdl-34647211

ABSTRACT

The current work assessed the degradation degree and the degradation products derived from norfloxacin (NOR) and gentamicin (GEN) using iodosylbenzene and iodobenzene diacetate, in the presence of manganese porphyrin as catalysts. Better results for NOR degradation (> 80%) were obtained when more hydrophobic porphyrins were employed. ß-brominated manganese porphyrins showed a lower GEN degradation (~ 25%) than the non-brominated ones (~ 35%), probably due to their steric hindrance. In any case, complete mineralization was achieved neither for NOR nor for GEN, and the assignment of the generated products, complemented by the study of their toxicity, was an important step performed. From the obtained results, no correlation was found between the number of identified products and the reported toxicity value (rSpearman,NOR = 0.006; p value = 0.986 and rSpearman,GEN = - 0,198; p value = 0.583), which reinforces the idea of synergism and antagonistic phenomena. The higher degradation degree could have led to products of lower steric hindrance and easier penetration into the A. fischeri cells, which subsequently led to an increase in toxicity for these experiments. In most cases, the products presented higher toxicity than the original compound, which raises a concern about their occurrence in environmental matrices.


Subject(s)
Manganese , Porphyrins , Catalysis , Gentamicins , Norfloxacin , Oxidation-Reduction
19.
Water Sci Technol ; 84(12): 3780-3790, 2021 Dec.
Article in English | MEDLINE | ID: mdl-34928843

ABSTRACT

The high resilience to biological treatments from the landfill leachate is generally associated with the presence of humic substances (HS). The brown color characteristic of this effluent is also related to these substances. Landfill leachate with low biodegradability can make biological treatments unfeasible, which can drive up the cost for the treatment of large leachate volumes. In this context, this research aimed to characterize the leachate in different seasonal periods, and verify the influence of HS species on the biodegradability of the effluent to assist in the selection of adequate treatment techniques. The HS quantification was performed using the modified Lowry method and speciation through fractionation according to the molar masses of the HS species. The tropical regions can be the precursor for the rapid stabilization of biodegradable organic matter. The warmer climate contributed to a reduced BOD/COD ratio (0.03) and the predominance of compounds of lower mass (e.g.: fulvic acids). The tests showed an HS concentration of 26.9% of the total COD in the raw leachate in the rainy season, which increased to 37.3% in the dry season. Approximately 70% of HS species refer to fulvic acids, a fraction identified as having the highest biologic treatment resilience.


Subject(s)
Humic Substances , Water Pollutants, Chemical
20.
Environ Monit Assess ; 193(10): 687, 2021 Oct 02.
Article in English | MEDLINE | ID: mdl-34601622

ABSTRACT

Phenolic compounds are widely spread in surface water, mainly in developing countries, where sewage and wastewater treatment are still reduced. Thus, this work quantified these pollutants in the Doce River analyzing the associated risk for the environment and human health. This river is in the state of Minas Gerais in Brazil and was recently impacted by the collapse of a mining dam that compromised the resilience of the entire watershed. For that purpose, a methodology for simultaneous identification and quantification of 17 different phenols was developed. It was possible to verify phenolic compounds' occurrence with concentration ranging from 0.13 to 24.16 µg·L-1. 2-Nitrophenol and bisphenol A appeared in all samples analyzed. The analytical method was processed using solid-phase extraction (SPE) (C18 cartridge), gas chromatography with FID, and mass spectrometry to define the analytes' retention time. For case validation, the selectivity, linearity, detection and quantification limits, sensitivity, precision, accuracy, resolution, matrix effect, and peak quality were assessed. Four different solvents were tested in the recovery-grade trials, which were dichloromethane, methanol, acetonitrile, and ethyl acetate. Among them, methanol had a better performance and was used throughout all analyses. The phenolic compounds had a recovery degree higher than 50% after SPE, regardless of the matrices.


Subject(s)
Rivers , Water Pollutants, Chemical , Brazil , Environmental Monitoring , Gas Chromatography-Mass Spectrometry , Humans , Phenols/analysis , Water , Water Pollutants, Chemical/analysis
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