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1.
Chemosphere ; 262: 127612, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32750590

RESUMO

Widely used conazole fungicides (CFs) belong to the most frequently detected pesticides in Central European arable soils. However, data on their environmental behaviour and bioavailability to soil organisms are surprisingly scarce. In the present laboratory microcosm study prochloraz, tebuconazole, epoxiconazole and flusilazole were applied to 12 different agricultural soils at background levels. Bioaccumulation to earthworm E. andrei and lettuce L. sativa roots and leaves was evaluated in non-aged (biota exposure after addition of pesticides) and aged (exposure started three months later) systems. In contrast with expectations from ageing effect (decrease of bioavailability), bioaccumulation in E. andrei was both reduced and enhanced after ageing depending on soil properties. The reduction of bioaccumulation correlated positively to the percentage of clay but negatively to soil organic matter. The affinity of compost worm E. andrei towards organic matter where hydrophobic pesticide molecules are sorbed is discussed as a possible explanation. An apparent effect of ageing (reduction of bioavailability) was particularly observed in lettuce roots, where bioaccumulation was significantly reduced in time. However, bioaccumulation in leaves changed ambiguously in aged variants among CFs, possibly as a combined result of bioconcentration, dilution by plant growth and metabolism. This study brings first insights into how the bioaccumulation of conazole fungicides is affected by sequestration in agricultural soils. The results indicate that in complex systems, the ageing is not necessarily connected with decrease of bioaccumulation.


Assuntos
Fungicidas Industriais/metabolismo , Poluentes do Solo/metabolismo , Agricultura , Animais , Bioacumulação , Disponibilidade Biológica , Argila , Compostos de Epóxi , Fungicidas Industriais/análise , Alface/metabolismo , Oligoquetos/metabolismo , Praguicidas/análise , Silanos , Solo/química , Poluentes do Solo/análise , Triazóis
2.
Indian J Dent Res ; 31(4): 562-568, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33107457

RESUMO

Context: Dental tissue remains are the toughest, and chemically, the most stable tissue in the body. Its high resilience in the events of fire and bacterial decomposition makes them vital for DNA analysis by PCR method. Aims: Determination of sex of children through molecular analysis of pulp tissue of exfoliated deciduous teeth stored in different media and analyzed after a different time period. Settings and Design: Sixty samples of deciduous teeth were divided into three groups. Group IA and Group IIA were stored in natural soil and wet clay for 1 month, respectively. Group IB and Group IIB were stored in natural soil and wet clay for 6 months, respectively. Group III was analyzed immediately after extraction. Methods and Material: Sex determination was carried out in five steps: Pulp tissue removal, DNA isolation, DNA quantification, PCR amplification, Sex determination. X and Y specific chromosomes from each sample were amplified and compared. Statistical Analysis Used: Kruskal-Wallis test, Dunn's test, and Wilcoxon signed rank test. Results: Group III revealed the highest amount of DNA quantified. Amount of DNA quantified after 6 months of storage in natural soil and wet clay decreased in both the groups with the samples stored in wet clay showing a maximum decrease. Results of the PCR analysis also showed 100% accuracy rate in the samples of Group III. Conclusions: Sex determination from pulp tissue depends a lot on the quality and quantity of DNA extracted. Sex could be effectively determined among the samples evaluated immediately after extraction. This ability decreases as the storage condition changes and the time period increases. Samples stored in wet clay were found to show the least sex identification ability than dry soil.


Assuntos
Argila , Solo , Criança , Humanos , Reação em Cadeia da Polimerase , Análise para Determinação do Sexo , Dente Decíduo
3.
ACS Chem Neurosci ; 11(20): 3188-3190, 2020 10 21.
Artigo em Inglês | MEDLINE | ID: mdl-33006886

RESUMO

SARS-CoV-2 is a positive stranded-RNA human viral pathogen that attacks the central nervous system (CNS), causing interminable diseases. Although alcohol-based hand sanitizers (ABHS) control the widespread transmission of such pathogens through dermal contact, excessive exposure to alcohol mists and vapors causes CNS disorders, apart from skin infections and negative impacts on the useful microbiome. Herein, we propose bentonite paste, which interacts strongly with different +RNA viruses such as SARS-CoV-2/poliovirus, for dermal sanitization. Repeated hand cleansing with bentonite paste not only provides complete protection against any viruses but also improves the skin condition. The proposed method is useful for contact isolation and as a strict infection control tool in hospital settings and in public.


Assuntos
Bentonita/farmacologia , Infecções por Coronavirus/prevenção & controle , Desinfecção das Mãos/métodos , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Betacoronavirus , Argila , Humanos
4.
J Environ Qual ; 49(1): 172-183, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33016355

RESUMO

Use of recycled concrete aggregate (RCA) as highway basecourse material conserves virgin aggregate, reduces energy consumption and CO2 emissions, and may also decrease costs during construction. However, concerns remain over possible negative environmental impacts associated with high pH (>11) effluent from RCA in contact with water. This study examines the reactive transport of high-pH and high-alkalinity water, modeled on RCA leachate, through model subgrade soils. By developing an understanding of the reactions controlling effluent neutralization, this study aims to quantify the change in pH from the discharge site through surrounding subgrade soils. Four types of subgrade soils with a range of mineral composition, Atterberg limits, and cation exchange capacities (CECs) are examined. They include a clayey sand (SC10), low-plasticity clays (M14, SC25), and a high-plasticity clay (CH38). Batch reaction experiments are used to develop kinetic parameters describing the neutralization of high-pH and -alkalinity leachate by clay minerals through mineral dissolution and reprecipitation. Given this information, a reactive transport model incorporating advection, diffusion, and reaction is used to model the change in pH as a function of distance traveled through model subgrade soils and is applied to laboratory-scale column experiments. The rate at which the high pH front travels is directly related to a soil's clay mineral content. Soils with high CECs effectively delay the propagation of hydroxide front by the dissolution of clay minerals. This study demonstrates that common subgrade soils with moderate clay content will effectively neutralize high pH leachate initially produced by RCA.


Assuntos
Poluentes do Solo/análise , Solo , Argila , Concentração de Íons de Hidrogênio , Reciclagem
5.
Polim Med ; 50(1): 33-40, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33125195

RESUMO

BACKGROUND: Co-processing starch with clay nanocomposite has been shown to yield a new class of materials, potentially with better properties than pristine starch, that could be used as directly compressible excipients in tablet formulations. OBJECTIVES: In this study, starches from 3 botanical sources, i.e., millet starch from Pennistum glaucum (L) RBr grains, sorghum starch from Sorghum bicolor L. Moench grains and cocoyam starch from Colocasia esculenta L. Schott tubers, were co-processed with montmorillonite clay (MMT) and evaluated as a directly compressible excipient in tramadol tablet formulations. The effects of different starch-to-clay ratios on the material and drug release properties of the resulting tablets were evaluated. MATERIAL AND METHODS: The starch-clay composites were prepared by heating a dispersion of the starch in distilled water, then precipitating the dispersion with an equal volume of 95% ethanol. The starch-clay composites were characterized and used as direct compression excipients for the preparation of tramadol tablets. The mechanical and drug release properties of the tablets were evaluated. RESULTS: Co-processing MMT with the starches yielded starch-clay composites with different material and tablet properties than the pristine starches. The co-processed starch-MMT biocomposites exhibited improved flowability and compressibility over the pristine starches. The mechanical and drug release properties of tramadol tablets containing starch-clay composites were significantly better than those containing only pristine starches. The properties of the starch-clay composites were not related to the botanical source of the starches. CONCLUSIONS: The study showed that starch-clay biocomposites could be used in the controlled release of tramadol.


Assuntos
Argila , Excipientes , Amido , Comprimidos , Tramadol , Composição de Medicamentos , Solubilidade
6.
Chemosphere ; 254: 126881, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957288

RESUMO

Application of biochar (BC) derived from rice straw has generated increasing interest in long-term storage of soil organic carbon (SOC), however its carbon (C) sequestration potential vary widely among agricultural soils despite the same BC dose used. These discrepancies in the ability of soils to sequester C after BC application are poorly understood. Metabolic quotient (qCO2) is a reflection of "microbial efficiency" and linked to SOC turnover across ecosystems. Therefore, we investigated the SOC sequestration and qCO2 in a Yellow River alluvium paddy soil (YP) and a quaternary red clay paddy soil (QP) under rice-wheat annual rotation following 4-year of BC application rate of 11.3 Mg ha-1 per cropping season. BC application consistently brought 65.3 Mg C ha-1 into the soils over 4-year experimental period but increased SOC by 57.6 Mg C ha-1 in YP and 64.5 Mg C ha-1 in QP. Calculating SOC mass balance showed 11.7% of BC-C losses from YP and only 1.16% from QP. BC application stimulated the G+ bacterial, fungi, and actinomycetes by increasing O-alkyl C content in YP, while decreased the same microorganisms by decreasing anomeric C-H content in QP. Importantly, higher clay and amorphous Fe (Feo) contents in QP after BC application protected SOC from further decomposition, which in turn decreased microorganisms and resulted in higher SOC sequestration than YP. Our results indicated that soil properties controlled the extent of SOC sequestration after BC application and site-specific soil properties must be carefully considered to maximize long-term SOC sequestration after BC application.


Assuntos
Agricultura/métodos , Sequestro de Carbono , Carvão Vegetal/química , Carbono/metabolismo , Argila , Ecossistema , Oryza/metabolismo , Solo/química
7.
Chemosphere ; 258: 127213, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32947655

RESUMO

Worldwide, the aquatic environment is contaminated by micro-pollutants, such as ingredients of personal care products, pesticides and pharmaceuticals. This contamination is one of the major environmental issues of global concern. Adsorption is one of approach, which has been most extensively discussed within recent years for the reduction of the input of micro-pollutants into the environment. In the present study, the natural clay classified as Na-montmorillonite, was characterized and tested for its potential to remove four model compounds representing different polarity and ionizability: i) diatrizoic acid (DAT), ii) iopamidol (IOP), iii) metformin (MTF), and iv) carbamazepine (CBZ). The adsorption efficiency of clay was evaluated by initial compound concentration, effect of pH, contact time and temperature. The results indicated that clay was able to remove the pharmaceuticals from aqueous medium with an efficiency of 70% for CBZ and MTF. In contrast, clay showed a lower removal of 30% for DAT and no removal for IOP. The results indicate that clay could rapidly and efficiently reduce the concentration of CBZ and MTF, which could provide a solution to remove some substances, without undesirable by-product generation. However, this study clearly demonstrated that removal rates strongly depend on the compound. Albeit chemical structure may play a role for the different degree of removal, this study could not completely explain the sorption mechanism between sorbent-sorbate interactions.


Assuntos
Bentonita/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Adsorção , Carbamazepina , Argila , Concentração de Íons de Hidrogênio , Temperatura , Águas Residuárias
8.
ACS Chem Neurosci ; 11(18): 2786-2788, 2020 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-32870651

RESUMO

Herein, we propose the use of novel adsorbents, namely micelle clay complexes comprising the clay montmorillonite, coupled with activated carbon for effective eradication of neuropathogenic microbes such as SARS-CoV-2 and Naegleria fowleri from water supplies for ablution/nasal irrigation. These can be incorporated easily to water collection devices, i.e., taps and water bottles, in the domestic setting. These filters are low cost, easy to install, and ideal disinfection systems. Such strategies are particularly useful for communities who have lack of access to safe water supplies, rely heavily on water storage tanks, or lack adequate water sanitation facilities, especially in developing countries.


Assuntos
Infecções por Coronavirus/prevenção & controle , Filtração/métodos , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Purificação da Água/métodos , Bentonita , Betacoronavirus , Infecções Protozoárias do Sistema Nervoso Central/prevenção & controle , Carvão Vegetal , Argila , Filtração/instrumentação , Humanos , Naegleria fowleri , Lavagem Nasal , Purificação da Água/instrumentação
9.
Ecotoxicol Environ Saf ; 203: 111023, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32888592

RESUMO

Tembotrione is a triketone group herbicide having worldwide applications for weed management in maize. It is considered to be less stable in the environment and its degradation products may have toxicological consequences due to longer persistence and off-site movements. We studied the persistence behavior and leaching potential of tembotrione and its major metabolite TCMBA in clay loam and sandy loam soils having different physico-chemical properties. The rapid transformation of parent tembotrione to degradation products and their high interactions with soil provided challenging task of residues separation from complex soil matrix. Therefore, a novel sample preparation method (modified QuEChERS) was optimized for trace estimation of tembotrione and TCMBA which offered 86.6-95.6% recoveries with limit of detection (LOD) and quantification (LOQ) as 0.001 and 0.003 µg/g, respectively in both soils without any matrix interference. A first order dissipation kinetics was followed by tembotrione and TCMBA residues with half-life ranged from 7.2 to 13.4 days in both soils. Residues reached below detectable limit on 45-60 days after treatments in two application doses. Leaching experiment revealed maximum retention of tembotrione residues from 15 to 25 cm depth in both soils whereas TCMBA show appreciable leaching potential. It was concluded that tembotrione can be phytotoxic to the succeeding crops if applied at late post-emergence stage. TCMBA can contaminate surface and ground water due to continuous and prolonged use of tembotrione particularly in light textured soils.


Assuntos
Benzoatos/análise , Cicloexanonas/análise , Herbicidas/análise , Resíduos de Praguicidas/análise , Poluentes do Solo/análise , Solo/química , Sulfonas/análise , Argila/química , Produtos Agrícolas/crescimento & desenvolvimento , Cinética , Limite de Detecção , Zea mays/crescimento & desenvolvimento
10.
Ecotoxicol Environ Saf ; 205: 111374, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32977284

RESUMO

Phenazines, a large group of nitrogen-containing heterocycles with promising bioactivities, can be widely used as medicines and pesticides. But phenazines also generate toxicity risks due to their non-selective DNA binding. The environmental fate of phenazines in soils is the key to assess their risks; however, hitherto, there have been very few related studies. Therefore in the present study, the degradation, adsorption and leaching behaviors of a typical natural phenazine-phenazine-1-carboxamide (PCN) in agricultural soils from three representative places in China with different physicochemical properties were, for the first time, systematically studied in laboratory simulation experiments. Our results indicated that the degradation of PCN in all the tested soils followed the first order kinetics, with half-lives ranging from 14.4 to 57.8 d under different conditions. Soil anaerobic microorganisms, organic matter content and pH conditions are important factors that regulating PCN degradation. The adsorption data of PCN were found to be well fitted using the Freundlich model, with the r2 values above 0.978. Freundlich adsorption coefficient Kf of PCN ranged from 5.75 to 12.8 [(mg/kg)/(mg/L)1/n] in soils. The retention factor Rf values ranged from 0.0833 to 0.354, which means that the mobility of PCN in the three types of soil is between immobile to moderately mobile. Our results demonstrate that PCN is easily degraded, has high adsorption affinity and low mobility in high organic matter content and clay soils, thus resulting in lower risks of contamination to groundwater systems. In contrast, it degraded slowly, has low adsorption affinity and moderately mobile in soils with low organic matter and clay content, therefore it has higher polluting potential to groundwater systems. Overall, these findings provide useful insights into the future evaluation of environmental as well as health risks of PCN.


Assuntos
Fenazinas/análise , Poluentes do Solo/análise , Adsorção , Agricultura , China , Argila , Água Subterrânea , Cinética , Praguicidas , Solo/química
11.
Bull Environ Contam Toxicol ; 105(4): 656-664, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32865632

RESUMO

Methiozolin is a novel herbicide for controlling annual bluegrass. After applying 14C labelled methiozolin in two sediment (clay loam and sand)-water systems under aerobic conditions, its distribution, half-life, and metabolites within 300 days were investigated. The mass balance ranged within 92.0%-104.4% of applied radioactivity (AR). Radioactivity in the water declined sharply from 94.4% to 0.5% AR, while in the sediment it increased to 83.9% AR at 14 days before declining to 9.1% AR. The volatiles were minimal (< 0.5% AR), and the evolved labelled CO2 accounted for up to ~ 33.4% AR. From Radio-HPLC analysis, labelled methiozolin in water decreased from 108.9% to 0% AR, while a maximum of 15.1% AR remained in the sediment at the end. Eight metabolites were detected, all at minor levels and accounting for < 5.5% AR. The half-life of labelled methiozolin in the total sediment-water systems were 50.7 and 38.7 days for clay loam and sand, respectively.


Assuntos
Herbicidas/análise , Isoxazóis/análise , Tiofenos/análise , Cromatografia Líquida de Alta Pressão , Argila , Meia-Vida , Herbicidas/metabolismo , Poa , Água
12.
Chemosphere ; 254: 126904, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957297

RESUMO

Estimating bioaccessible content of mercury in soils is essential in evaluating risks that contaminated soils pose. In this study, soil samples spiked with HgCl2 through adsorption were used to test the effects of liming, soil organic matter, soil depth, and Hg concentration on the following bioaccessibility tests: dilute nitric acid at room temperature, dilute nitric acid at body temperature, Simplified Bioaccessibility Extraction Test (SBET) method, and gastric phase of the In vitro Gastrointestinal (IVG) protocol. Soil and sediment samples from Descoberto, Minas Gerais (Brazil), a city with a well-known record of Hg contamination from artisanal mining, were subjected to these bioaccessibility tests for the first time, and the different methods of estimating bioaccessible content were compared. Bioaccessible fractions in spiked samples ranged from 10% to 60%, and this high bioaccessibility was due to the highly soluble species of Hg and the short time under adsorption. In general, clay and organic matter decreased bioaccessible content. Although the soil in Descoberto is undoubtedly polluted, mercury bioaccessibility in that area is low. In general, dilute nitric acid estimated higher bioaccessible content in soil samples, whereas the SBET method estimated higher bioaccessible content in sediment samples. In multivariate analysis, two groups of bioaccessibility tests arise: one with the two nitric acid tests, and the other with SBET and the gastric phase of the IVG protocol. The addition of pepsin and glycine in the last two tests suggests a more reliable test for assessing mercury bioaccessibility.


Assuntos
Argila/química , Substâncias Húmicas/análise , Mercúrio/análise , Mineração , Poluentes do Solo/análise , Solo/química , Adsorção , Disponibilidade Biológica , Brasil , Cidades , Mucosa Gástrica/metabolismo , Humanos , Mucosa Intestinal/metabolismo , Mercúrio/metabolismo , Modelos Biológicos , Ácido Nítrico/química , Poluentes do Solo/metabolismo
13.
Water Res ; 186: 116380, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32919139

RESUMO

Filamentous fungi are believed to remove a wide range of environmental xenobiotics due to their characteristically non-specific catabolic metabolisms. Nonetheless, irregular hyphal spreading can lead to clogging problems in treatment facilities and the dependence of pollutant bioavailability on hyphal surface features severely limits their applicability in water treatment. Here, we propose a scalable and facile methodology to structurally modify fungal hyphae, allowing for both the maximization of pollutant sorption and fungal pellet morphology self-regulation. Halloysite-doped mycelium architectures were efficiently constructed by dipping Aspergillus fumigatus pellets in halloysite nanotube-dispersed water. Ultrastructure analyses using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy revealed that the nanotubes were mainly attached to the outer surface of the pellets. Fungal viability and exoenzyme production were hardly affected by the halloysites. Notably, nanotube doping appeared to be extremely robust given that detachments rarely occurred even in high concentrations of organic solvents and salt. It was also demonstrated that the doped halloysites weakened hyphal growth-driven gelation, thus maintaining sphere-like pellet structures. The water treatment potential of the hybrid fungal mycelia was assessed through both cationic toxic organic/inorganic-contaminated water and real dye industry wastewater clean-ups. Aided by the mesoporous halloysite sites on their surface, the removal abilities of the hybrid structures were significantly enhanced. Moreover, inherent low sorption ability of HNT for heavy metals was found to be overcome by the aid of fungal mycelia. Finally, universal feature of the dipping-based doping way was confirmed by using different filamentous fungi. Given that traditional approaches to effectively implement fungus-based water treatment are based mostly on polymer-based immobilization techniques, our proposed approach provides a novel and effective alternative via simple doping of living fungi with environmentally-benign clays such as halloysite nanotubes.


Assuntos
Nanotubos , Purificação da Água , Cerâmica , Argila , Hifas
14.
J Environ Manage ; 271: 110978, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32778277

RESUMO

Geosynthetic clay liners (GCL) are increasingly being used as a major component of barrier systems replacing compacted clay liners due to their very low permeability and speed of installation. Researchers and practitioners have identified the critical role of the GCL overlap that presents constant challenges encountered in maintaining the designed hydraulic conductivity. This study presents a series of flow box tests conducted to evaluate and improve understanding of the combined effect of each of the four contributing factors, namely, overlap width, supplemental bentonite applied at the overlap, the overburden confining stress, and the hydraulic head acting on the GCL overlap. The findings reveal that the overlap width is the most significant parameter affecting the design hydraulic conductivity. The application of a minimum overburden stress to maintain the designed hydraulic performance is also recognised as important. The effect of confinement due to higher hydraulic heads is of interest to practitioners. The supplemental bentonite has the least effect on the GCL overlap hydraulic performance even though it enhances the function of the overlap seam. This knowledge addresses the inadequacy of published GCL overlap experimental data comparing the effect of different factors affecting its hydraulic performance. It also assists industry practitioners to design and specify the overlap criterion for a specific application depending on the product specifications and site conditions. The results of this research will help minimise failures of liner systems in barrier applications such as landfills, mines, tailing dams substantially to reduce the potential risk of groundwater contamination.


Assuntos
Argila , Eliminação de Resíduos , Silicatos de Alumínio , Condutividade Elétrica , Instalações de Eliminação de Resíduos
15.
J Environ Manage ; 271: 111019, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32778301

RESUMO

Kaolinite nanotubes were synthesized by a simple scrolling process and decorated by ZnO nanoparticles as a novel nanocomposite (ZnO/KNTs). The synthetic ZnO/KNTs composite was characterized as an effective photocatalyst in the oxidation of levofloxacin pharmaceutical residuals in the water resources. The composite displays a surface area of 95.4 m2/g, average pore diameter of 5.8 nm, and bandgap energy of 2.12 eV. It is of high catalytic activity in the oxidation of levofloxacin in the presence of visible light source. The complete oxidation for 10 mg/L of levofloxacin was recognized after 55 min, 45 min, and 30 min with applying 30 mg, 40 mg, and 50 mg of ZnO/KNTs as catalyst dosage, respectively. Additionally, it achieved complete oxidation for 20 mg/L and 30 mg/L of levofloxacin after 45 min and 75 min, respectively using 50 mg as catalyst dosage. The degradation efficiency was confirmed by detecting the residual TOC after the treatment tests and the formed intermediate compounds were identified to suggest the degradation pathways. In addition to the oxidation pathway, the mechanism was evaluated based on the active trapping tests that proved the dominance of hydroxyl radicals as the essential active species. Finally, the ZnO/KNTs composite is of promising recyclability properties and achieved better results than several studied photocatalysts in literature.


Assuntos
Nanotubos , Preparações Farmacêuticas , Óxido de Zinco , Argila , Levofloxacino , Luz , Água
16.
PLoS One ; 15(8): e0235421, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32756552

RESUMO

We investigated rock varnish, a thin, manganese- and iron-rich, dark surface crust, on basaltic lava flows and petroglyphs in the Owens and Rose Valleys (California) by portable X-ray fluorescence (pXRF) and femtosecond laser-ablation inductively-coupled-plasma mass spectrometry (fs-LA-ICPMS). The major element composition of the varnish was consistent with a mixture of Mn-Fe oxyhydroxides and clay minerals. As expected, it contained elevated concentrations of elements that are typically enriched in rock varnish, e.g., Mn, Pb, Ba, Ce, and Co, but also showed unusually high enrichments in U, Cu, and Th. The rare earth and yttrium (REY) enrichment pattern revealed a very strong positive cerium (Ce) anomaly and distinct negative europium (Eu) and Y anomalies. The light rare earth elements (REE) were much more strongly enriched than the heavy REY. These enrichment patterns are consistent with a formation mechanism by leaching of Mn and trace elements from aeolian dust, reprecipitation of Mn and Fe as oxyhydroxides, and scavenging of trace elements by these oxyhydroxides. We inferred accumulation rates of Mn and Fe in the varnish from their areal densities measured by pXRF and the known ages of some of the lava flow surfaces. The areal densities of Mn and Fe, as well as their accumulation rates, were comparable to our previous results from the desert of Saudi Arabia. There was a moderate dependence of the Mn areal density on the inclination of the rock surfaces, but no relationship to its cardinal orientation. We attempted to use the degree of varnish regrowth on the rock art surfaces as an estimate of their age. While an absolute dating of the petroglyphs was not possible because of the lack of suitable calibration surfaces and a considerable amount of variability, the measured degree of varnish regrowth on the various petroglyphs was consistent with chronologies based on archeological and other archaeometric techniques. In particular, our results suggest that rock art creation in the study area continued over an extended period of time, possibly starting around the Pleistocene/Holocene transition and extending into the last few centuries.


Assuntos
Argila/química , Hidróxidos/análise , Ferro/análise , Manganês/análise , California , Meio Ambiente , Monitoramento Ambiental , Espectrometria de Massas , Metais Terras Raras/análise , Espectrometria por Raios X , Propriedades de Superfície , Erupções Vulcânicas , Ítrio/análise
17.
Environ Monit Assess ; 192(9): 562, 2020 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-32754777

RESUMO

The Digha-Shankarpur area in West Bengal suffers from the problem of saline water intrusion in the near-surface to shallow subsurface aquifers. In the present study, geophysical surveys were conducted and integrated with measured hydrogeological parameters to delineate the possible locations of saline water-invaded zones in the shallow aquifers. One hundred eighty-eight groundwater samples were collected, and parameters like salinity, EC, total dissolved solids (TDS), pH, temperature, and water level were measured. The geophysical survey, such as resistivity profiling, self-potential, and electrical resistivity imaging techniques, was applied. High TDS, salinity, and EC were observed in various places. Resistivity profiling survey indicates a low resistivity zone (< 10 Ωm), self-potential anomaly indicates a positive anomaly and resistivity imaging survey indicated very low resistivity zones (0-3 Ωm) in near-surface to shallow subsurface locations which are concurrent with the other coastal aquifers in the eastern part of India. These low resistivity zones are interpreted as saline water intrusion zone mixed with clay/sand layers up to a depth of 15 m possibly due to the ingression of seawater and also due to anthropogenic activities. Hence, protection from seawater intrusion from the canals into the coastal aquifers (shallow and deep) and human-made activities should be restricted to minimize the effect of saline water pollution.


Assuntos
Argila , Água Subterrânea , Monitoramento Ambiental , Índia , Salinidade , Areia , Água do Mar
18.
Environ Pollut ; 266(Pt 2): 115249, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32738727

RESUMO

Tremendous efforts have been devoted by researchers on air particulate matter pollution for the increasing harm, however, the Air Pollution Index (API) from "good" to "excellent" is something hard to achieve. Here, halloysite nanotubes/polyvinyl alcohol (HNTs/PVA) hybrid membrane with surface micro-nano structure processing using a one-step method for efficient PM2.5 capture was prepared. The filtration efficiency is 45.35% and the pressure drop is 41.57 Pa of composite membrane with a 60 wt% halloysite dosage. Specially, it resulted in a relatively safer PM index value of about 16.54, which tends to be more stringent than the restriction by Government of China (PM2.5 < 35 µg/m3). The filtration performance was mainly attributed to the controllable microroughness surface as well as the hierarchical structure constructed by one-step method, which has a functional role in obstruction and adsorption for diluted PM2.5. The methodology can employ halloysite onto various polymers, like polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyacrylonitrile (PAN) and also polycaprolactone (PCL) to yield hybrid membranes with the similar modification of surface and structure. Such versatile membrane filters can be purposely designed and scaled up, which endows the existing hybrid membrane with great potentials in both residential and public areas pollution control to achieve a healthier living environment.


Assuntos
Poluição do Ar/análise , Material Particulado/análise , China , Argila , Álcool de Polivinil
19.
Ecotoxicol Environ Saf ; 202: 110915, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32800250

RESUMO

Benzobicyclon is a systemic herbicide that was officially registered in China in 2018. The environmental behaviors of benzobicyclon hydrolysate (BH), the main metabolite and active product of benzobicyclon, remain poorly understood in paddy fields. Here, agricultural soil samples were collected from paddy fields in Jiangxi (Ferralsols), Shandong (Alisols), Hebei (Luvisols), Heilongjiang (Phaeozems), Zhejiang (Anthrosols), Sichuan (Gleysols), Hainan (Plinthosols), and Hubei (Lixisols) across China. The equilibrium oscillation method was used to study the adsorption-desorption behaviors of BH in the eight soils. The relationships between BH adsorption and soil physicochemical properties, environmental factors (temperature and initial solution pH), and other external conditions (addition of humic acid, biochar, and metal ions) were quantified. The adsorption-desorption parameters of BH in all soils were well fitted by the Freundlich model. The adsorption constant of BH varied between 0.066 and 4.728. The BH adsorption capacity decreased in the following order: Phaeozems > Alisols > Ferralsols > Lixisols > Plinthosols > Anthrosols > Luvisols > Gleysols. The Freundlich adsorption and desorption constants of BH were linearly positively correlated with soil clay content (R2 = 0.711 and 0.709; P = 0.009 and 0.009, respectively), organic carbon content (R2 = 0.684 and 0.672; P = 0.011 and 0.013, respectively), and organic matter content (R2 = 0.698 and 0.683; P = 0.010 and 0.011, respectively); however, their linear relationships with soil cation exchange capacity were not significant (R2 = 0.192 and 0.192; P = 0.278 and 0.278, respectively). The adsorption and desorption constants of BH had negative, albeit not significant, correlations with soil pH (R2 = 0.104 and 0.100; P = 0.437 and 0.445, respectively). The adsorption of BH by soil occurred spontaneously and was mainly based on physical adsorption. Either low or high temperature reduced the ability of the soil to adsorb BH. The addition of humic acid to the soil increased BH adsorption, while the addition of biochar increased the solution pH, resulting in decreased BH adsorption. Cation type and ionic strength also had strong effects on BH adsorption. With the exception of Phaeozems, BH exhibited intermediate or high mobility in the agricultural soils and thus poses risks to surface water and groundwater.


Assuntos
Compostos Bicíclicos com Pontes/química , Herbicidas/química , Poluentes do Solo/química , Sulfonas/química , Adsorção , Agricultura , China , Argila , Água Subterrânea , Herbicidas/análise , Solo/química , Poluentes do Solo/análise
20.
J Environ Radioact ; 222: 106362, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32858445

RESUMO

A general approach is presented to derive probabilistic radionuclide distribution coefficients (Kd) in soils from a Kd dataset. The main aim was to derive informed estimates with a low inherent uncertainty by restricting the Kd value data to subsets based on key soil factors and the experimental approach used to calculate the Kd value (e.g., sorption and desorption tests). As an example, the general approach was applied to uranium (U) Kd values that are part of a critically reviewed dataset containing more than 5000 soil Kd entries for 83 elements and an additional 2000 entries of Kd data for 75 elements gathered from a selection of other, non-soil, geological materials. The overall soil U Kd dataset included 196 values spanning a range of four orders of magnitude (1-67,000 L kg-1), with additional 50 entries for other geological materials. Whereas the effect of the experimental approach could be disregarded, major factors in decreasing U Kd variability were pH and organic matter content (OM). Limitation in the number of entries made it difficult to use texture information (sand, silt, clay) to further decrease U Kd variability. The integrated combination of pH + OM permitted some soil groups to have U Kd confidence intervals as narrow as two orders of magnitude. Specifically for U Kd, data in the Mineral (< 20% OM) and Organic (≥ 20% OM) partial datasets were significantly different. Analogue data from geological materials other than soils, such as subsoil, till and gyttja (a lacustrine mud having elevated organic matter (OM) contents), were also statistically evaluated to determine whether they could be used to fill U Kd data gaps. It was shown that U Kd from subsoils and tills, but not gyttjas, could be used to enhance soil U Kd datasets. Selection of probabilistic Kd values for risk modelling can be made more reliably and with less uncertainty by using appropriate geochemical data representative of the study site to narrow the wide range of potential Kd values.


Assuntos
Monitoramento de Radiação , Poluentes Radioativos do Solo , Poluentes do Solo , Urânio , Adsorção , Argila , Solo , Poluentes Radioativos do Solo/análise , Urânio/análise
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