Sensitivities of ozone to its precursors during heavy ozone pollution events in the Yangtze River Delta using the adjoint method.

Although the concentrations of five basic ambient air pollutants in the Yangtze River Delta (YRD) have been reduced since the implementation of the "Air Pollution Prevention and Control Action Plan" in 2013, the ozone concentrations still increase. In order to explore the causes of ozone pollution in YRD, we use the GEOS-Chem and its adjoint model to study the sensitivities of ozone to its precursor emissions from different source regions and emission sectors during heavy ozone pollution events under typical circulation patterns. The Multi-resolution Emission Inventory for China (MEIC) of Tsinghua University and 0.25° × 0.3125° nested grids are adopted in the model. By using the T-mode principal component analysis (T-PCA), the circulation patterns of heavy ozone pollution days (observed MDA8 O3 concentrations ≥160 µg m-3) in Nanjing located in the center area of YRD from 2013 to 2019 are divided into four types, with the main features of Siberian Low, Lake Balkhash High, Northeast China Low, Yellow Sea High, and southeast wind at the surface. The adjoint results show that the contributions of emissions emitted from Jiangsu and Zhejiang are the largest to heavy ozone pollution in Nanjing. The 10 % reduction of anthropogenic NOx and NMVOCs emissions in Jiangsu, Zhejiang and Shanghai could reduce the ozone concentrations in Nanjing by up to 3.40 µg m-3 and 0.96 µg m-3, respectively. However, the reduction of local NMVOCs emissions has little effect on ozone concentrations in Nanjing, and the reduction of local NOx emissions would even increase ozone pollution. For different emissions sectors, industry emissions account for 31 %-74 % of ozone pollution in Nanjing, followed by transportation emissions (18 %-49 %). This study could provide the scientific basis for forecasting ozone pollution events and formulating accurate strategies of emission reduction.

DNA-bridged double gold nanoparticles-based immunochromatography for dual-mode detection of ochratoxin A.

A novel immunochromatography strip (ICS) based on the DNA-bridged double gold nanoparticles was established and evaluated for the dual-mode detection of ochratoxin A (OTA). For this purpose, the streptavidin was coupled with the big size of gold nanoparticle (40 nm, AuNP), the OTA monoclonal antibody and biotinylated DNA-SH were simultaneously immobilized on the small size of AuNP (20 nm), and then the enhanced ICS was self-assembled and evaluated. The dual-mode detection of semi-quantification and quantification had been achieved and performed by the proposed ICS. The LOD for semi-quantification (semi-Q-LOD) was 0.06 ng/mL by the directly naked eye (eightfold enhanced than conventional ICS). By the on-site reader, the LOD for quantification (Q-LOD) was 0.03 ng/mL (threefold enhanced), with the detection range between 0.03 and 1.2 ng/mL. The specificity, reliability, and practicability had been well represented. Furthermore, the OTA-positive results of the enhanced ICS method correlated well with those obtained by the referenced HPLC-MS/MS for the market samples. This study provided a new ICS pattern of semi-quantification and quantification for OTA contamination, which could be used as a valuable reference for improving the ICS technology and enhancing the sensitivity.

[Response of PM2.5 and O3 to Emission Reductions in Nanjing Based on Random Forest Algorithm].

High levels of fine particulate matter (PM2.5) and ozone (O3) in ambient air affect climate change and also endanger human health and ecosystems. Air pollution in Nanjing has been improving since the implementation of the "Air Pollution Prevention and Control Action Plan" in 2013. However, Nanjing still faces PM2.5 and O3 pollution. Evaluating the response of pollutant concentrations to the reductions in precursor emissions is helpful to obtain effective strategies of emission reduction to improve pollution levels. The sensitive simulations of emission perturbation in atmospheric chemistry models directly demonstrate the response of pollution to the reductions in emissions. Nevertheless, these sensitive simulations are limited in computing time and resources. The random forest algorithm was trained by using the simulation results of the atmospheric chemical transport model (GEOS-Chem) in 2015. The changes in daily PM2.5 and daily maximum eight-hour O3 (MDA8 O3) concentrations in Nanjing in 2019 were efficiently predicted under different reduction scenarios of anthropogenic emissions. The simulations showed that the seasonal average of ρ(PM2.5) in Nanjing would decrease by 2-4 µg·m-3 with the reduction in anthropogenic emissions of 10% in 2019 in China. In the case of controlling only local emissions in Nanjing, the concentrations of PM2.5 in Nanjing decreased significantly without local anthropogenic emissions. Additionally, the simulations showed that the annual average of ρ(PM2.5) in Nanjing could be lower than the national secondary limit (35 µg·m-3) when the anthropogenic emission reduction in China was higher than 20% in 2019. For ozone, the equal proportional emission reductions in nitrogen oxides (NOx) and volatile organic pollutants (VOCs) of O3 precursors in China likely led to the increase in seasonal average concentrations of O3 in Nanjing. For the proportional reduction of anthropogenic emissions by 10%-50% in China, the seasonal average of ρ(MDA8 O3) in Nanjing in 2019 would increase by 1-3 µg·m-3 in spring, 1-4 µg·m-3 in autumn, and 3-11 µg·m-3 in winter, respectively, compared with that in the base simulation. With the reduction in anthropogenic NOx emission by 10% and VOCs by 20%, the seasonal average of ρ(MDA8 O3) in Nanjing would decrease by 3-6 µg·m-3. On this basis, further increasing the proportion (30%) of VOCs emission reduction could reduce the annual average of ρ(MDA8 O3) in Nanjing by 7 µg·m-3. However, the annual average of ρ(MDA8 O3) of Nanjing in 2019 increased by 1 µg·m-3, with the local emission reduction of NOx by 10% and VOCs by 30%. Therefore, this showed that the key to alleviate ozone pollution in Nanjing is a reasonable control ratio of ozone precursor emissions and the implementation of regional joint prevention and control. In order to effectively reduce the O3 pollution in Nanjing, the emission reduction ratio of NOx and VOCs in China should be less than 1:2. The response of pollutant concentrations to reductions in precursor emissions were efficiently obtained by the random forest algorithm and GEOS-Chem model. The simulations would provide the scientific basis for the emission control strategy to alleviate air pollution.

An enhanced immunochromatography assay based on gold growth on the surface of E. coli carrier for the simultaneous detection of mycotoxins.

It is desired and urgently needed to improve the sensitivity of immunochromatography assay (ICA) for hazardous chemicals. In this work, an enhanced ICA strip was established and evaluated for simultaneous, semi-quantitative and quantitative detection of ochratoxin A (OTA) and aflatoxin B1 (AFB1). The signal strategy based on gold growth on the surface of the E. coli K12 carrier was recommended, which was successfully self-assembled on the enhanced ICA with a double test line pattern. When used as a novel carrier, the E. coli K12 could provide a larger surface area, better biocompatibility and high loading capacity, which was of great help to improve the performance of the ICA. By the naked eye, the semi-quantitative limit of detection (semi-Q-LOD) reached 0.03 ng/mL for both OTA and AFB1 (17-fold and 33-fold lower than the conventional ICA strip). By the digitized strip reader, the quantitative LODs (Q-LODs) were all identified as 0.01 ng/mL for two mycotoxins (10-fold improvement), with detection ranges of 0.01-0.5 ng/mL for OTA and 0.01-0.2 ng/mL for AFB1. Furthermore, the high reliability and applicability of the ICA were confirmed by its good correlation with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The advantages of the improved sensitivity, high efficiency and cost savings had been reflected for the ICA. This study could provide an important reference method for the sensitive, simultaneous, rapid and on-site monitoring of multicomponent contaminants.

[Light-absorbing Properties and Sources of PM2.5 Organic Components at a Suburban Site in Northern Nanjing].

The light absorption of organic components in PM2.5 was investigated at a suburban site in northern Nanjing from September 2018 to September 2019, and PM2.5 compositional data and principal component analysis (PCA) were used to identify the sources of light-absorbing organic carbon (brown carbon, BrC). The results showed that the average light absorption coefficients of water-soluble organic carbon (WSOC) and methanol extractable organic carbon (MEOC) were (3.22±2.18) Mm-1 (Abs365,w) and (7.69±4.93) Mm-1(Abs365,m), respectively. Significant correlations were observed between Abs365,w and mass concentrations of WSOC (r=0.72, P<0.01) and between Abs365,m and mass concentrations of MEOC (r=0.62, P=0.04). Both Abs365,w and Abs365,m exhibited seasonal variations, with higher values during winter than during summer,and higher diel variations at night than during the day. This can be attributed to meteorological characteristics during the winter and nighttime, i.e., decreased boundary layer height and increased atmospheric stability, enhanced primary emissions in winter,and stronger photobleaching effects during the summer and during the day. The annual average Abs365,m/Abs365,w ratio (2.60±0.92) was much larger than the average mass ratio of MEOC/WSOC (1.37±0.30), indicating that the water-insoluble fraction of MEOC had a stronger light absorption effect and dominated BrC absorption. No strong correlation (r<0.60) was observed between WSOC, MEOC, Abs365,m, and mass concentrations of K+, indication that biomass burning was not the main source of BrC in the study location. The mass absorption efficiency of WSOC (MAE365,w) and MEOC (MAE365,m) and their ratios (MAE365,m/MAE365,w) showed similar seasonal variations to Abs365. The average MAE365 value of the water-insoluble fraction of MEOC (4.10±5.15) m2·g-1 was 6.0 and 2.9 times higher than that of MAE365,w and MAE365,m, respectively, suggested that BrC absorption was primarily attributable to water-insoluble components. In comparison to the absorption Ångström exponent of WSOC (ÅWSOC), ÅMEOC displayed marked temporal variability, which might be related to the seasonal variation in the emission of water-insoluble chromophores. According to the PCA results, the light absorption of PM2.5 organic was mainly attributed to secondary formation and anthropogenic primary emissions rather than biomass burning.

Ultrasensitive monitoring strategy of PCR-like levels for zearalenone contamination based DNA barcode.

BACKGROUND: The ultrasensitive monitoring strategy of zearalenone (ZEN) is essential and desirable for food safety and human health. In the present study, a coupling of gold nanoparticles-DNA barcode and direct competitive immunoassay-based real-time polymerase chain reaction signal amplification (RT-IPCR) for ZEN close to the sensitivity of PCR-like levels is described and evaluated. RESULTS: The RT-IPCR benefited from the use of a DNA barcode and RT-PCR detection strategy, thus resulting in ultrasensitive and simple detection for ZEN. Under the optimal RT-IPCR, the linear range of detection was from 0.5 to 1000 pg mL-1 and the limit of detection was 0.5 pg mL-1 , which was 400-fold lower than the enzyme-linked immunosorbent assay. The detection procedure was simplified and the detection time was shortened. The specificity, accuracy and precision of the RT-IPCR confirmed a high performance. ZEN-positive contamination levels were from 0.056 to 152.12 ng g-1 by the RT-IPCR, which was demonstrated to be highly reliable by liquid chromatography-tandem mass spectrometry. CONCLUSION: The proposed RT-IPCR could be used as an alternative for detecting ZEN with satisfactory ultrasensitivity, simplicity, low cost and high-throughput. The present study could provide a strategy for the ultrasensitive detection of the small molecule with a simple and practical approach, which has significant appeal and application prospects.

Semi-quantitative and quantitative detection of ochratoxin A in agricultural by-products using a self-assembling immunochromatographic strip.

BACKGROUND: The toxicity and health risks of mycotoxins have encouraged increased awareness and strict monitoring of these contaminants in agricultural by-products. In this paper, we developed and tested a sensitive, selective, and self-assembling immunochromatographic (IC) strip for on-site detection of ochratoxin A (OTA). We were able to demonstrate semi-quantitative and quantitative detection of OTA in agricultural by-product samples. RESULTS: The optimized IC strip had a limit of detection (LOD) of 0.5 ng mL-1 OTA using the naked eye for semi-quantitative detection. When a digitized strip reader was used to achieve quantitative results, the LOD for OTA was reduced to 0.1 ng mL-1 with a linear detection range of 0.1-10 ng mL-1 . We also evaluated the specificity, stability, accuracy, and precision of the IC strip and demonstrated high performance in all of these areas. We then confirmed the ability of the IC strip to visually detect OTA contamination in authentic agricultural by-product samples from the markets in China. Furthermore, quantitative detection of OTA using the IC strip showed that the concentration of OTA ranged from 1.7 to 101.3 ng g-1 in the positive agricultural by-product samples, correlating well with the measurements obtained via liquid chromatography with tandem mass spectrometry. CONCLUSION: The results indicated that this proposed IC strip was capable of sensitive, semi-quantitative, quantitative, and on-site detection of OTA contamination in agricultural by-product samples. © 2020 Society of Chemical Industry.

Contamination of Zearalenone from China in 2019 by a Visual and Digitized Immunochromatographic Assay.

Zearalenone (ZEN) is a prevalent mycotoxin that needs intensive monitoring. A semi-quantitative and quantitative immunochromatographic assay (ICA) was assembled for investigating ZEN contamination in 187 samples of cereal and their products from China in 2019. The semi-quantitative detection model had a limit of detection (LOD) of 0.50 ng/mL with visual judgment and could be completely inhibited within 5 min at 3.0 ng/mL ZEN. The quantitative detection model had a lower LOD of 0.25 ng/mL, and ZEN could be accurately and digitally detected from 0.25-4.0 ng/mL. The ICA method had a high sensitivity, specificity, and accuracy for on-site ZEN detection. For investigation of the authentic samples, the ZEN-positive rate was 62.6%, and the ZEN-positive levels ranged from 2.7 to 867.0 ng/g, with an average ZEN-positive level being 85.0 ng/g. Of the ZEN-positive samples, 6.0% exceeded the values of the limit levels. The ZEN-positive samples were confirmed to be highly correlated using LC-MS/MS (R2 = 0.9794). This study could provide an efficiency and accuracy approach for ZEN in order to achieve visual and digitized on-site investigation. This significant information about the ZEN contamination levels might contribute to monitoring mycotoxin occurrence and for ensuring food safety.

Sources of black carbon during severe haze events in the Beijing-Tianjin-Hebei region using the adjoint method.

The Beijing-Tianjin-Hebei (BTH) region in China has been frequently suffering from severe haze events (observed daily mean surface fine particulate matter PM2.5 concentrations larger than 150 µg m-3) partially caused by certain types of large-scale synoptic patterns. Black carbon (BC), as an important PM2.5 component and a primarily emitted species, is a good tracer for investigating sources and formation mechanisms leading to severe haze pollutions. We apply GEOS-Chem model and its adjoint to quantify the source contributions to BC concentrations at the surface and at the top of the planetary boundary layer (PBL) during typical types of severe haze events for April 2013-2017 in BTH. Four types of severe haze events, mainly occurred in December-January-February (DJF, 62.3%) and in September-October-November (SON, 26.3%), are classified based on the associated synoptic weather patterns using principal component analysis. Model results reasonably capture the daily variations of BC measurements at three ground sites in BTH. The adjoint method attributes BC concentrations to emissions from different source sectors and from local versus regional transport at the model spatial and temporal resolutions. By source sectors, the adjoint method attributes the daily BC concentrations during typical severe haze events (in winter heating season) in Beijing largely to residential emissions (48.1-62.0%), followed by transportation (16.8-25.9%) and industry (19.1-29.5%) sectors. In terms of regionally aggregated source influences, local emissions in Beijing (59.6-79.5%) predominate the daily surface BC concentrations, while contributions of emissions from Beijing, Hebei, and outside BTH regions are comparable to the daily BC concentrations at the top of PBL (~200-400 m). Our adjoint analyses would provide a scientific support for joint regional and targeted control policies on effectively mitigating the particulate pollutions when the dominant synoptic weather patterns are predicted.

Zearalenone Contamination in Corn, Corn Products, and Swine Feed in China in 2016-2018 as Assessed by Magnetic Bead Immunoassay.

In total, 405 samples of corn, corn products, and swine feed from China in 2016-2018 were surveyed for zearalenone (ZEN) contamination using a magnetic bead immunoassay-coupled biotin-streptavidin system (BAS-MBI). The developed BAS-MBI had a limit of detection (LOD) of 0.098 ng mL-1, with half-maximal inhibition concentration (IC50) of 0.71 ng mL-1 in working buffer, and an LOD of 0.98 ng g-1; the detection range was from 0.98 to 51.6 ng g-1 in authentic agricultural samples. The BAS-MBI has been demonstrated to be a powerful method for the rapid, sensitive, specific, and accurate determination of ZEN. The ZEN positivity rate reached the highest level of 40.6% in 133 samples in 2016; ZEN levels ranged from 1.8 to 1100.0 ng g-1, with an average level of 217.9 ng g-1. In 2017, the ZEN positivity rate was the lowest at 24.5% in 143 samples; ZEN levels ranged from 1.1 to 722.6 ng g-1, with an average of 166.7 ng g-1. In 2018, the ZEN positivity rate was 31.8% in 129 samples; ZEN levels ranged from 1.3 to 947.8 ng g-1, with an average of 157.0 ng g-1. About 20% of ZEN-positive samples exceeded maximum limit levels. An alternative method of ZEN detection and a valuable reference for ZEN contamination in corn and its related products in China are provided. This survey suggests the need for prevention of serious ZEN contamination, along with management for food safety and human health.

Sources of particulate matter in China: Insights from source apportionment studies published in 1987-2017.

Particulate matter (PM) in the atmosphere has adverse effects on human health, ecosystems, and visibility. It also plays an important role in meteorology and climate change. A good understanding of its sources is essential for effective emission controls to reduce PM and to protect public health. In this study, a total of 239 PM source apportionment studies in China published during 1987-2017 were reviewed. The documents studied include peer-reviewed papers in international and Chinese journals, as well as degree dissertations. The methods applied in these studies were summarized and the main sources in various regions of China were identified. The trends of source contributions at two major cities with abundant studies over long-time periods were analyzed. The most frequently used methods for PM source apportionment in China are receptor models, including chemical mass balance (CMB), positive matrix factorization (PMF), and principle component analysis (PCA). Dust, fossil fuel combustion, transportation, biomass burning, industrial emission, secondary inorganic aerosol (SIA) and secondary organic aerosol (SOA) are the main source categories of fine PM identified in China. Even though the sources of PM vary among seven different geographical areas of China, SIA, industrial, and dust emissions are generally found to be the top three source categories in 2007-2016. A number of studies investigated the sources of SIA and SOA in China using air quality models and indicated that fossil fuel combustion and industrial emissions were the most important sources of SIA (total contributing 63.5%-88.1% of SO42-, and 47.3%-70% NO3-), and agriculture emissions were the dominant source of NH4+ (contributing 53.9%-90%). Biogenic emissions were the most important source of SOA in China in summer, while residential and industrial emissions were important in winter. Long-term changes of PM sources at two megacities of Beijing and Nanjing indicated that the contributions of fossil fuel and industrial sources have been declining after stricter emission controls in recent years. In general, dust and industrial contributions decreased and transportation contributions increased after 2000. PM2.5 emissions are predicted to decline in most regions during 2005-2030, even though the energy consumptions except biomass burning are predicted to continue to increase. Industrial, residential, and biomass burning sources will become more important in the future in the businuess-as-usual senarios. This review provides valuable information about main sources of PM and their trends in China. A few recommendations are suggested to further improve our understanding the sources and to develop effective PM control strategies in various regions of China.

Premixed injectable calcium phosphate cement with excellent suspension stability.

Premixed injectable calcium phosphate cement (p-ICPC) pastes have advantages over aqueous injectable calcium phosphate cement (a-ICPC) because p-ICPC remain stable during storage and harden only after placement into the defect. This paper focused on the suspension stability of p-ICPC paste by using fumed silica as a stabilizing agent and propylene glycol (PEG) as a continuous phase. Multiple light scanning techniques were first applied to evaluate the suspension stability. The results indicated that fumed silica effectively enhanced the suspension stability of p-ICPC pastes. The stabilizing effect of fumed silica results from the network structure formed in PEG because of its thixotropy. The p-ICPC could be eventually hydrated to form hydroxyapatite under aqueous circumstances by the unique replacement between water and PEG. p-ICPC (1) not only possesses proper thixotropy and compressive strength but has good injectability as well. p-ICPC (1) was cytocompatible and had no adverse effect on the attachment and proliferation of MG-63 cells in vitro. These observations may have applicability to the development of other nonaqueous injectable biomaterials for non-immediate filling and long-term storage.

In vitro osteoblast-like and endothelial cells' response to calcium silicate/calcium phosphate cement.

This study aims to investigate the interaction between calcium silicate/calcium phosphate cement (CS/CPC) and osteogenesis, in particular the in vitro osteoblast-like and endothelial cells' response to CS/CPC. The effect of CS/CPC on cell attachment, proliferation and differentiation of murine osteoblast-like cell MC3T3-E1, as well as the influence on the cell attachment and proliferation of human umbilical vein endothelial cell (HUVEC), was studied in detail. Our results indicated that CS/CPC exhibited excellent biocompatibility to the osteoblast-like cells. Moreover, the morphology and cytoskeleton organization of MC3T3-E1 cultured on the CS/CPC disks suggested that CS/CPC induced better cell adhesion and cell spreading. Simultaneously, cell proliferation and alkaline phosphatase (ALP) activity of MC3T3-E1 were significantly improved after 3 and 7 days of culture on CS/CPC disks in comparison with CPC disks. Additionally, on CS/CPC disks, HUVEC attached well on day 1 and cell proliferation was also greatly enhanced by day 7. Collectively, these results suggest that the introduction of calcium silicate may improve the cell response involved in the osteogenesis and thus may be beneficial to further modify CPC as a better bone repairing material.

Bismuth-doped injectable calcium phosphate cement with improved radiopacity and potent antimicrobial activity for root canal filling.

A bismuth-doped injectable calcium phosphate cement (BD-ICPC) with improved radiopacity, potent antimicrobial activity and sealability was developed by introducing bismuth salicylate basic (BSB) into the powder phase of the calcium phosphate cement (CPC). The results showed that the radiopacity and sealability of BD-ICPC were improved compared with pure ICPC. Although BSB had a retarding effect on the setting rate of the cement, the addition of BSB reduced the viscosity and yield stress of BD-ICPC, thus enhanced its injectability. It was noteworthy that BD-ICPC had a potent antimicrobial activity with improved sealability. In addition, BD-ICPC afforded a uniform and tight adaptation to the root canal wall. These results indicate that BD-ICPC possesses a combination of good in vitro radiopacity, high injectability, potent antimicrobial activity, improved sealability and tight adaptation to the root canal. It is expected to be used as a novel root canal filling material.