Identification and Parametrization of Key Factors Affecting Levoglucosan Emission During Solid Fuel Burning.

Levoglucosan (LG) is a pyrolysis product of cellulose and hemicellulose at low combustion temperatures. However, LG release cannot be determined only by considering the contents of cellulose and hemicellulose exclusively due to the complexity of combustion processes and the physical-chemical properties of the fuel. This study detected the emission factors (EFs) of LG from 22 different solid fuel samples (including coal and biomass) by considering 18 different fuel properties and five combustion parameters. The average LGEFs during solid fuel burning varied in a range of 0.03-136 mg kg-1, with a magnitude difference of 1-4 orders. While the variations in cellulose (59.5-368 mg g-1) and hemicellulose (73.5-165 mg g-1) contents of fuel samples were only one- to 6-fold. A short combustion duration (<150 min) and a medium combustion temperature (200-400 °C) influenced by volatile and ash contents are crucial for the generation and accumulation of LG. A random forest coupled with the Akaike information criterion stepwise regression model successfully explained 96% of the total LG emission variation using three variables (ash content, cellulose content, and modified combustion efficiency). The ash content promoted coke formation and LG chain cracking by increasing the pyrolysis temperature and is considered the most important factor. The alkali metal in ash can reduce the energy barrier of intramolecular ring contraction reactions and inhibit the dehydration reactions, which led to additional heat being utilized by the competitive pathways of LG formation. This study provided a method to address the parametrization and release mechanisms of combustion source emissions.

Enrichment and Quantitative Determination of 5-(Hydroxymethyl)-2'-deoxycytidine, 5-(Formyl)-2'-deoxycytidine, and 5-(Carboxyl)-2'-deoxycytidine in Human Urine of Breast Cancer Patients by Magnetic Hyper-Cross-Linked Microporous Polymers Based on Polyionic Liquid.

5-(Hydroxymethyl)-2'-deoxycytidine (5-hmdC), 5-(formyl)-2'-deoxycytidine (5-fodC), and 5-(carboxyl)-2'-deoxycytidine (5-cadC) are crucial intermediate products of the DNA demethylation pathway, which can also act as potential biomarkers reflecting the diagnosis and prognosis in multiple tumors. Detecting 5-hmdC, 5-fodC, and 5-cadC in human urine has various advantages including readily available samples and being noninvasive to patients. However, few works have reported the detection of 5-fodC and 5-cadC due to their trace amounts. Here we developed a novel magnetic hyper-cross-linked microporous polymer (HMP) material based on polyionic liquid (PIL) for the enrichment of 5-hmdC, 5-fodC, and 5-cadC. These magnetic PIL-HMP materials provided specific enrichment superiority for three modified cytidines. After enrichment, the signal intensity of 5-hmdC, 5-fodC, and 5-cadC increased 10-75-fold with lower limits of quantitation (LLOQ) of 0.049, 0.781, and 0.781 ng/mL, respectively. The recoveries were approximately 86.5-95.2% for 5-hmdC, 95.2-107.8% for 5-fodC, and 99.4-102.4% for 5-cadC under the relative standard deviation (RSD) of 0.2-10.3%. Finally, we successfully applied magnetic PIL-HMP materials coupled with high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) in enrichment and quantitative determination of 5-hmdC, 5-fodC, and 5-cadC in human urine of 10 breast cancer patients and 10 healthy people. We found that the level of 5-hmdC decreased in breast cancer patients ( p < 0.05), while the levels of 5-fodC and 5-cadC increased ( p < 0.05, p < 0.01). Our results demonstrated that the levels of metabolic 5-hmdC, 5-fodC, and 5-cadC in human urine are closely related to breast cancer, which could contribute to the clinical diagnosis and investigation of breast cancer and its occurrence and development mechanisms.

Metagenomics reveals the influence of small microplastics on microbial communities in coastal sediments.

The ecological impact of microplastics (MPs) in coastal environments has been widely studied. However, the influence of small microplastics in the actual environment is often overlooked due to measurement challenges. In this study, Hangzhou Bay (HZB), China, was selected as our study area. High-throughput metagenomic sequencing and micro-Raman spectrometry were employed to analyze the microbial communities and microplastics of coastal sediment samples, respectively. We aimed to explore the ecological impact of MPs with small sizes (≤ 100 µm) in real coastal sediment environments. Our results revealed that as microplastic size decreased, the environmental behavior of MPs underwent alterations. In the coastal sediments, no significant correlations were observed between the detected MPs and the whole microbial communities, but small MPs posed potential hazards to eukaryotic communities. Moreover, these small MPs were more prone to microbial degradation and significantly affected carbon metabolism in the habitat. This study is the first to reveal the comprehensive impact of small MPs on microbial communities in a real coastal sediment environment.

Prevalence of small-sized microplastics in coastal sediments detected by multipoint confocal micro-Raman spectrum scanning.

Microplastics have become global emerging issue and received widespread attention in recent years. Due to their chemical persistence, plastic particles can be broken into smaller items but accumulated for long time in the environment like sediment. However, limited by current detection technologies, the distribution and characteristics of small-sized microplastics in coastal sediment remain uncertain. In this study, we established a new method based on micro-Raman spectroscopy for detecting small-sized microplastics, namely multipoint confocal micro-Raman spectrum scanning (MCmRSS). The MCmRSS was first applied in detecting microplastics in the sediment samples collected from three bays of the East China Sea. The minimum size of microplastics was 4 µm and average microplastics concentration was 91 ± 55 items /g dry weight sediment, with fragment and polyethylene as the most common shape and polymer type, respectively. The spatial variation of microplastics was in accordance with the strength of coastal human activities and marine dynamics. In all the microplastic items, the small-sized ones (<10 µm) accounted for 67%; and the relationship between microplastic concentration and its size followed a power-exponential equation. Compared with previous studies, the number of microplastics in coastal sediments detected by the MCmRSS increased by 2 orders of magnitude, which was benefited from the advantages of multipoint scanning in the fixed identification areas and high resolution of micro-Raman spectrum. Our findings would summon the re-evaluation of the potential risks of small-sized microplastics in the coastal environment.