Microplastics (MPs), the appearance of which has gained considerable interest, can act as vectors to transport other pollutants such as metals into organisms. In this study, the sorption isotherms of ...three model heavy metals (i.e., Cu2+, Cd2+, and Pb2+) on four virgin plastic particles including chlorinated polyethylene (CPE), PVC, and two polyethylene plastic particles (i.e., LPE and HPE). HPE and LPE were investigated. The results showed that MPs can load high amounts of Pb2+, Cu2+ and Cd2+. The sorption affinity of the three metals to the model MPs followed the sequence of CPE > PVC > HPE > LPE. The adsorption process was affected by the chemical structure and electronegativity of the sorbents, and seemed irrelevant to the crystallinity of MPs. For the three metals, Pb2+ exhibited significantly stronger sorption than did Cu2+ and Cd2+ due to the strong electrostatic interaction. Moreover, pH can significantly affect the sorption of metals on MPs, but ionic strength exerted a relatively slight effect on this process. In brief, the electrostatic interaction played an important role in the sorption of Pb2+ to model MPs. For Cd2+ and Cu2+, sorption was determined by electrostatic interaction together with surface complexation onto the plastic surface. This study indicates that depending on the surface physicochemical properties of MPs the adsorption behavior can vary significantly. Therefore, the adsorption process of metals on MPs should be readily affected by other environmental mediums in the environment. The study provides additional insight into the behavior of MPs as a vector of metals.
•Sorption of Cu2+, Cd2+, and Pb2+ on four virgin plastic particles was investigated.•The sorption strength followed the order of Pb2+>Cu2+>Cd2+.•PH and ionic strength can affect the sorption of metals on MPs.•Electrostatic interaction played an important role in the sorption of Pb2+ to MPs.•Electrostatic interaction and complexation determined the sorption of Cd2+ and Cu2+.
Iron-impregnated activated carbons have been found to be very effective in arsenic removal. Oxyanionic arsenic species such as arsenate and arsenite adsorb at the iron oxyhydroxide surface by forming ...complexes with the surface sites. Our goal has been to load as much iron within the carbon pores as possible while also rendering as much of the iron to be available for sorbing arsenic. Surface oxidation of carbon by HNO
3/H
2SO
4 or by HNO
3/KMnO
4 increased the amount of iron that could be loaded to 7.6–8.0%; arsenic stayed below 10
ppb until 12,000 bed volumes during rapid small-scale tests (RSSCTs) using Rutland, MA groundwater (40–60
ppb arsenic, and pH of 7.6–8.0). Boehm titrations showed that surface oxidation greatly increased the concentration of carboxylic and phenolic surface groups. Iron impregnation by precipitation or iron salt evaporation was also evaluated. Iron content was increased to 9–17% with internal iron-loading, and to 33.6% with both internal and external iron loading. These iron-tailored carbons reached 25,000–34,000 bed volumes to 10
ppb arsenic breakthrough during RSSCTs. With the 33.6% iron loading, some iron peeled off.
Content-based image retrieval for medical images is a primary technique for computer-aided diagnosis. While it is a premise for computer-aided diagnosis system to build an efficient medical image ...database which is paid less attention than that it deserves. In this paper, we provide an efficient approach to develop the archives of large brain CT medical data. Medical images are securely acquired along with relevant diagnosis reports and then cleansed, validated and enhanced. Then some sophisticated image processing algorithms including image normalization and registration are applied to make sure that only corresponding anatomy regions could be compared in image matching. A vector of features is extracted by non-negative tensor factorization and associated with each image, which is essential for the content-based image retrieval. Our experiments prove the efficiency and promising prospect of this database building method for computer-aided diagnosis system. The brain CT image database we built could provide radiologists with a convenient access to retrieve pre-diagnosed, validated and highly relevant examples based on image content and obtain computer-aided diagnosis.
It is of great interest to elucidate the biogeographic patterns of soil microorganisms and their driving forces, which are fundamental to predicting alterations in microbial‐mediated functions ...arising from environmental changes. Although the vertical movement of dissolved organic matter (DOM) drives the cycle of nutrients such as soil carbon, in the restored ecosystem, the relationship between DOM and soil microbial nutrient utilization remains to be determined. Here, we investigated the changes of soil microbial community at 0–40 cm depth profile in three stages (10, 30, 50 years) of succession in Larix olgensis plantations and the fluorescence spectrum composition of DOM. With the increase of soil depth, the signal source of microorganisms increases. In a coniferous forest soil environment, the possible main source of DOM in deep soil is the production of microbial metabolism. Difficulty in the decomposition of organic matter determines the distribution and composition of microorganisms. Increasing forest age makes bacteria and fungi more specific and bacterial‐fungal associations greater. Overall, our work contributes to the understanding of factors underlying microbial community distribution in plantation forests and the importance of DOM quality in the building microbial community.
The environmental behavior of microplastics (MPs) has attracted global attention. Research has confirmed that MPs can strongly absorb almost every kind of pollutant and can serve as vectors for ...pollutant transport. In this research, the sorption isotherms of six organic pollutants with different structure on four virgin plastic particles with different crystallinity were determined. Results indicated that the hydrophobicity (
K
OW
) of organic pollutants and the crystallinity of MPs were the two key factors that affected the sorption process of organic pollutants on MPs. Strong correlations were observed between
K
OW
and the partition coefficient. Hydrophobic partition was one of the major mechanisms regardless of the type of organic chemical (hydrophobic, polar, or dissociable). What is more, the influence of the crystallinity of MPs on the sorption process increased with increasing hydrophobicity of the chemical. Combining this result with analyzing the related literature on the effect of crystallinity, it was concluded that the effect of crystallinity on the sorption of chemicals with strong hydrophobicity was obvious, whereas this effect was negligible for chemicals with weak hydrophobicity. The influence of the crystallinity of MPs on sorption could even exceed the influence of MPs type, so crystallinity should be considered carefully when discussing the sorption capacity of MPs. This study enhances the understanding of the sorption of organic pollutants by MPs.
Graphical Abstract
This case study investigated the distribution and fate of organic pollutants in aquatic environments based on laboratory experiments and modeling. Pyrene (Pyr) is a hydrocarbon pollutant with adverse ...effects on aquatic ecosystems and human health, and was thus selected for this case study. The movement of Pyr was primarily influenced by its sorption from water onto sediment, and its desorption from sediment into water. Its elimination was mainly via biodegradation by microorganisms in sediment and by volatilization from water into air. The transport and elimination rates for Pyr were considerably influenced by temperature and moisture. Results of modeling with Markov chains revealed that the elimination of Pyr from water/sediment systems was the most rapid under wet conditions. Under average conditions, a Pyr concentration of 100 μg/L of in water in such a system declined to a negligible level over 250 h. Under wet conditions, this decrease occurred over 120 h. Finally, under dry conditions, it took 550 h to achieve the same degree of elimination.
Complex disorders usually affect multiple symptom domains measured by several outcomes. The importance of these outcomes is often different among patients. Current approaches integrate multiple ...outcomes without considering patient preferences at the individual level. In this article, we propose a new composite Desirability of Outcome Ranking (DOOR) that integrates individual level ranking of outcome importance and define a winning probability measuring the overall treatment effect. Stratified randomization can be performed based on the participants' baseline outcome rankings. A Wilcoxon-Mann-Whitney U-statistic is used to average the pairwise DOOR between one treated and one control patient, considering the difference in these patients' ranking of outcome importance. We use both theoretical and empirical methods to examine the statistical properties of our method and to compare with conventional approaches. We conclude that the proposed composite DOOR properly reflects patient-level preferences and can be used in pivotal trials or comparative effectiveness trials for a patient-centered evaluation of overall treatment benefits.
Arsenic of over 50 ppb level in drinking water could cause a lifetime risk of dying from cancer for the consumer. Although, conventional granular activated carbon (GAC) has a very limited capacity ...for removing arsenic, it was found that tailoring GAC by preloading iron could enhance its bed life, when the iron tailored GAC was coupled with precorroded iron, the GAC’s bed life could greatly enhanced. For carbon tailoring, incipient wetness method and organic-iron preloading method were employed. 1–3% Fe loading was achieved with organic-iron preloading method and 3–6% Fe loading was achieved via incipient wetness method. Compared with virgin GAC, the citric acid-iron preloaded GAC could extend the GAC’s bedlife by over 20 times to 7000 bed volumes of 50 ppb arsenic containing water processed before 10 ppb breakthrough. The incipient wetness method could further extend the GAC’s bedlife by 2 times. Precorroded iron material, coupled with Organic carboxyl-Fe preloaded granular activated carbons (GAC), have been appraised as an innovative technique for removing arsenic from groundwater. The effective precorroded iron materials have included Galvanized Steel Fittings and Perforated Steel Sheets. Rapid Small Scale Column Tests (RSSCT’s) and mini column tests had been conducted to evaluate the arsenic removal capacity of the procorroded iron coupled with tailored carbon. The arsenic was found to be removed by both the iron column and the GAC column, with GAC column as the major absorber. The pH, idling and precorrosion protocol affect the iron release and arsenic removal. The combination of a precorroded iron column followed by a iron – tailored GAC column removed arsenic to below 10 ppb for as much as 248,000 bed volumes (BVs) at pH 6. These tests employed Rutland, MA groundwater with native As of 47 ∼ 55 ppb. Idling the system for one time extended the bed life of by 2 time, but caused a short period arsenic breakthrough after column restart. Arsenic removal in the GAC column was proportional to the iron amount accumulated in the GAC column. The iron amount accumulated in the GAC column was generally controlled by the operating pH, but was also affected by the precorrosion conditions of the iron and the idling of the system. The arsenic removal in the iron column was generally higher with lower pH. Moreover, as the column just started up, the removal was also controlled by the iron pre-corrosion condition. A longer precorrosion period has promoted arsenic removal in the iron column. The arsenic removal was generally lower with aged PSSs as the column just started, this was attributed to the release of iron (hydr)oxides particles from the iron column; but with longer aging period of more than 10 days, arsenic removal by aged PSSs could be greatly increased. The precorrosion protocol influenced the formation of surface corrosion layer of the iron, which in turn, affected how the iron was released and accumulated in the GAC column, especially when the column just restarted. The morphology and structure of surface corrosion products on precorroded steel sheets were studied via scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) method. The results showed that the morphology of surface corrosion products was highly related to iron release and arsenic removal. Fresh precorroded steel sheets have a uniform surface, while aged precorroded steel sheets exhibited a heterogeneous surface with some areas covered with thick, porous scales. Lepidocrocite (γ-FeOOH), humboditine (FeC2O4(H2O)2) and clinoferrosilite (Fe1.5Mg0.5Si2O6) are the mainly component on the fresh precorroded steel sheet, while goethite (α-FeOOH), lepidocrocite and magnetite (Fe3O4) are the primary component of the aged precorroded steel sheet surface. After they were employed in the column for arsenic removal, the primary phase on precorroded steel sheet changed to goethite and magnetite, calcite was also detected. Arsenic extracted from precorroded steel in iron columns contain only As(III) when the column was operated at pH < 7 and had been idled. XAFS study of the GAC in pH 7.5 column indicated the presence of reduced iron phases such as FeO and green rust, some As(V) has also been reduced to As(III). Idling the columns for 7 days is promoted a reduction reaction in both the iron and the GAC columns.
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