Trisodium Citrate as a Double-Edged Sword: Selective Etching Prussian Blue Analog Nanocubes into Orthogonal Frustums and Their Derivatives for Supercapacitors.

The construction of novel structured Prussian blue analogs (PBAs) by chemical etching has attracted the most attention to PBA derivatives with outstanding performance. In this work, the unprecedented PBA orthogonal frustums are first prepared from nanocubes through a selective chemical etching approach using trisodium citrate as an etchant. The citrate ions can chelate with nickel species from the edges/corners of NiCo-PBA nanocubes and then disintegrate NiCo-PBAs resulting in the generation of NiCo-PBA orthogonal frustums. The derived CoNi2S4/Co0.91S composites still inherit the original orthogonal frustum structure and possess outstanding supercapacitor performance. This study develops a popularized method to construct novel structured PBAs and brings inspiration for designing PBA-based electrodes with advanced electrochemical performance.

Combined Transcriptomics and Metabolomics Identify Regulatory Mechanisms of Porcine Vertebral Chondrocyte Development In Vitro.

Porcine body length is closely related to meat production, growth, and reproductive performance, thus playing a key role in the profitability of the pork industry. Cartilage development is critical to longitudinal elongation of individual vertebrae. This study isolated primary porcine vertebral chondrocytes (PVCs) to clarify the complex mechanisms of elongation. We used transcriptome and target energy metabolome technologies to confirm crucial genes and metabolites in primary PVCs at different differentiation stages (0, 4, 8, and 12 days). Pairwise comparisons of the four stages identified 4566 differentially expressed genes (DEGs). Time-series gene cluster and functional analyses of these DEGs revealed four clusters related to metabolic processes, cartilage development, vascular development, and cell cycle regulation. We constructed a transcriptional regulatory network determining chondrocyte maturation. The network indicated that significantly enriched transcription factor (TF) families, including zf-C2H2, homeobox, TF_bZIP, and RHD, are important in cell cycle and differentiation processes. Further, dynamic network biomarker (DNB) analysis revealed that day 4 was the tipping point for chondrocyte development, consistent with morphological and metabolic changes. We found 24 DNB DEGs, including the TFs NFATC2 and SP7. Targeted energy metabolome analysis showed that most metabolites were elevated throughout chondrocyte development; notably, 16 differentially regulated metabolites (DRMs) were increased at three time points after cell differentiation. In conclusion, integrated metabolome and transcriptome analyses highlighted the importance of amino acid biosynthesis in chondrocyte development, with coordinated regulation of DEGs and DRMs promoting PVC differentiation via glucose oxidation. These findings reveal the regulatory mechanisms underlying PVC development and provide an important theoretical reference for improving pork production.

Simple and Rapid Way to a Multifunctionally Conductive Hydrogel for Wearable Strain Sensors.

Conductive hydrogels have gained increasing attention in the field of wearable smart devices. However, it remains a big challenge to develop a multifunctionally conductive hydrogel in a rapid and facile way. Herein, a conductive tannic acid-iron/poly (acrylic acid) hydrogel was synthesized within 30 s at ambient temperature by the tannic acid-iron (TA@Fe3+)-mediated dynamic catalytic system. The TA@Fe3+ dynamic redox autocatalytic pair could efficiently activate the ammonium persulfate to initiate the free-radical polymerization, allowing the gelation to occur easily and rapidly. The resulting hydrogel exhibited enhanced stretchability (3560%), conductivity (33.58 S/m), and strain sensitivity (gauge factor = 2.11). When damaged, it could be self-healed through the dynamic and reversible coordination bonds between the Fe3+ and COO- groups in the hydrogel network. Interestingly, the resulting hydrogel could act as a strain sensor to monitor various human motions including the huge movement of deformations (knuckle, wrist) and subtle motions (smiling, breathing) in real time due to its enhanced self-adhesion, good conductivity, and improved strain sensitivity. Also, the obtained hydrogel exhibited efficient electromagnetic interference (EMI) shielding performance with an EMI shielding effectiveness value of 24.5 dB in the X-band (8.2-12.4 GHz). Additionally, it displayed antibacterial properties, with the help of the activity of TA.

Biomass-Derived Carbon Materials for the Electrode of Metal-Air Batteries.

Facing the challenges of energy crisis and global warming, the development of renewable energy has received more and more attention. To offset the discontinuity of renewable energy, such as wind and solar energy, it is urgent to search for an excellent performance energy storage system to match them. Metal-air batteries (typical representative: Li-air battery and Zn-air battery) have broad prospects in the field of energy storage due to their high specific capacity and environmental friendliness. The drawbacks preventing the massive application of metal-air batteries are the poor reaction kinetics and high overpotential during the charging-discharging process, which can be alleviated by the application of an electrochemical catalyst and porous cathode. Biomass, also, as a renewable resource, plays a critical role in the preparation of carbon-based catalysts and porous cathode with excellent performance for metal-air batteries due to the inherent rich heteroatom and pore structure of biomass. In this paper, we have reviewed the latest progress in the creative preparation of porous cathode for the Li-air battery and Zn-air battery from biomass and summarized the effects of various biomass sources precursors on the composition, morphology and structure-activity relationship of cathode. This review will help us understand the relevant applications of biomass carbon in the field of metal-air batteries.

Significant contribution of secondary particulate matter to recurrent air pollution: Evidence from in situ observation in the most polluted city of Fen-Wei Plain of China.

Particulate matter (PM) pollution in high emission regions will affect air quality, human health and climate change on both local and regional scales, and thus attract worldwide attention. In this study, a comprehensive study on PM2.5 and its chemical composition were performed in Yuncheng (the most polluted city of Fen-Wei Plain of China) from November 28, 2020 to January 24, 2021. The average concentration of PM2.5 was 87.8 ± 52.0 µg/m3, which were apparently lower than those observed during the same periods of past five years, attributable to the clean air action plan implemented in this region. NO3- and organic carbon (OC) were the dominant particulate components, which on average contributed 22.6% and 16.5% to PM2.5, respectively. The fractions of NO3-, NH4+, OC and trace metals increased while those of crustal materials and elemental carbon decreased with the degradation of PM2.5 pollution. Six types of PM2.5 sources were identified by the PMF model, including secondary inorganic aerosol (35.3%), coal combustion (28.7%), vehicular emission (20.7%), electroplating industry (8.6%), smelt industry (3.9%) and dust (2.8%). Locations of each identified source were pinpointed based on conditional probability function, potential source contribution function and concentration weighted trajectory, which showed that the geographical distribution of the sources of PM2.5 roughly agreed with the areas of high emission. Overall, this study provides valuable information on atmospheric pollution and deems beneficial for policymakers to take informed action to sustainably improve air quality in highly polluted region.

Variation in PM2.5 sources in central North China Plain during 2017-2019: Response to mitigation strategies.

Central North China Plain (NCP) is one of the most important source region of air pollutants over the Beijing-Tianjin-Hebei (BTH) region. The national government has issued abatement measures to improve the air quality in this area from 2017. To examine the effects of control measures, observational analysis on PM2.5 characteristics was performed in a city of central NCP during 2017-2019 to investigate the variation in mass concentration, chemical composition, and emission source of PM2.5. Annual PM2.5 concentration significantly reduced by 16% from 2017 to 2019, implying substantial improvements in air quality. PM2.5 enriched in autumn-winter seasons was dominated by SNA (sum of sulfate, nitrate and ammonium; ~38%), followed by organic carbon matters (OM; ~24%) and fine soil (FS; ~12%). This chemical composition was different from that in a megacity in NCP (Beijing) where OM accounted for a comparable fraction to SNA. Approximately half of SNA was attributed to nitrate, indicating that SNA changed from sulfate-driven to nitrate-driven, and the considerable effects of coal combustion cutoff, in which sulfate was concentrated. Decreased mass fraction of SNA and increased OM fraction in PM2.5 were observed in 2018-2019 partly contributed to the decrease in PM2.5. A progressive increase in the contribution of heterogeneous formed SNA whilst a decrease in OM was observed as the pollution elevated from clean to heavily polluted. Six sources (soil dust, biomass burning, secondary emission, road traffic, coal combustion and industry) were identified by the Positive Matrix Factorization (PMF) model in both years and dominated by secondary aerosols, respectively contributing 39% and 41% to PM2.5. The decreasing concentrations (with reductions of 17%-61%) of the secondary source, coal combustion, soil dust and biomass burning largely accounted for the reduction in PM2.5, as a consequence of the recent abatement measures. By contrast, contributions of vehicle-related emissions, similar to the increasing contribution of vehicles at sites in NCP after 2013, should receive increased attention.

[Assay of 18 amino acids in Chuanmingshen violaceum roots by pre-column derivative HPLC].

The roots of Chuanmingshen violaceum is a commonly used Chinese herb and food, which contains rich amino acids. However, the kinds and amounts of amino acids are variety in this herb among the geographical location and ecological environment. Therefore, this study firstly developed a new pre-column derived HPLC method to quantify the levels of 18 amino acids in Ch. violaceum roots. Then 24 Ch. violaceum samples were harvested from its main cultivating areas in Sichuan, China. These samples were divided into 4 producing areas based on their geographical sites. The 18 kinds of amino acids were quantified in these sample by the developed method. The differences of these amino acids were further analyzed among these herbal samples and the 4 producing areas by t-test and principal component analysis(PCA). The result indicated the peaks of the 18 kinds of amino acids were separated well in 70 min.The correlation coefficients between peak areas and concentration of these amino acids were more than 0.999 1(n=6). All of their recoveries were in the range of 97.38%-101.3%(n=6).Their detection limit was in the range of 0.003-0.379 µg·mL~(-1).It demonstrates that the developed HPLC method can accurately quantify the amounts of multi-amino acids in this herb. The results of t-test analysis showed the contents of histidine, cystine, leucine, valine, tryptophan, phenylalanine and threonine were significantly different(P<0.05) among the 4 producing areas. But the differences of other amino acids were not significant.The first five factors were extracted by PCA to calculate the comprehensive score. The order of comprehensive score for the 4 producing areas was B(0.603, n=10), C(0.206, n=3), A(-0.283, n=7) and D(-1.167, n=4). The total content of amino acids in Ch. violaceum collected in B producing area was largest(12.5 mg·g~(-1)). It is concluded the Ch. violaceum contains multi-kinds of amino acids. On the basis of amino acid amount, Langzhong city and Cangxi county in Sichuan province(producing area B) is the suitable areas for cultivating Ch. violaceum.

The Stabilization Effect of CO2 in Lithium-Oxygen/CO2 Batteries.

The lithium (Li)-air battery has an ultrahigh theoretical specific energy, however, even in pure oxygen (O2 ), the vulnerability of conventional organic electrolytes and carbon cathodes towards reaction intermediates, especially O2 - , and corrosive oxidation and crack/pulverization of Li metal anode lead to poor cycling stability of the Li-air battery. Even worse, the water and/or CO2 in air bring parasitic reactions and safety issues. Therefore, applying such systems in open-air environment is challenging. Herein, contrary to previous assertions, we have found that CO2 can improve the stability of both anode and electrolyte, and a high-performance rechargeable Li-O2 /CO2 battery is developed. The CO2 not only facilitates the in situ formation of a passivated protective Li2 CO3 film on the Li anode, but also restrains side reactions involving electrolyte and cathode by capturing O2 - . Moreover, the Pd/CNT catalyst in the cathode can extend the battery lifespan by effectively tuning the product morphology and catalyzing the decomposition of Li2 CO3 . The Li-O2 /CO2 battery achieves a full discharge capacity of 6628 mAh g-1 and a long life of 715 cycles, which is even better than those of pure Li-O2 batteries.

Surface Coordination of Black Phosphorus with Modified Cisplatin.

Black phosphorus (BP) is a two-dimensional (2D) nanomaterial with high charge-carrier mobility, a tunable direct bandgap, and a unique in-plane anisotropic structure; however, the easiness of BP oxidation into P xO y species in ambient conditions largely limits its applications. In this study, modified cisplatin-Pt-NO3 [Pt(NH3)2(NO3)2] is used for surface coordination with BP nanosheets to generate Pt@BP, which maintains the surface morphology and properties of BP nanosheets for more than 24 h in ambient conditions. In addition, Pt@BP interacts with DNA both in vitro and in cell. Pt@BP shows a good cellular uptake rate and significantly increases the drug sensitivity of cisplatin-resistant cancer cell lines (A2780 and HepG2) compared with unmodified cisplatin. Our study is the first attempt to stabilize bare BP with cationic cisplatin species, and the generated Pt@BP could be used for potential synergistic photothermal/chemotherapy of cisplatin-resistant cancer.

Oral Delivery of Pingyangmycin by Layer-by-Layer (LbL) Self-Assembly Polyelectrolyte-Grafted Nano Graphene Oxide.

With the increasing development in scientific technology, building a nanocarrier system for cancer drugs has become a bliss for cancer patients. To allow for the oral administration of hydrophilic drugs, a nanocarrier that was based on negatively charged graphene oxide (GO) and prepared through the Layer-by-Layer (LbL) self-assembly of poly(acrylic acid)-cysteine (PAA-cys) and poly(allylamine hydrochloride) (PAH) was established. In the present study, we demonstrated the excellent biological properties of GO, the biological adhesiveness of PAA-cys, and the protection and controlled release profiles of polyelectrolyte. Pingyangmycin (PYM) was loaded onto the nanocarrier through non-covalent interactions. In vitro drug release studies of the prepared PAA-cys-PAH-GO-PYM were pH-sensitive and showed sustained release effects for over 8 h, before they were completely expelled by gastrointestinal peristalsis. Furthermore, cell viability experiments using A549 lung adenocarcinoma cells revealed that the IC50 of PAA-cys-PAH-GO-PYM, free drug, and GO-PYM were 159.241 µM, 134.960 µM, and 129.815 µM respectively, indicating the higher retention and cytotoxicity of PYM in vitro. When comparing the oral bioavailability of PYM with free drug, in vivo pharmacokinetics studies showed a 1.03-fold and 1.74-fold increase after GO loading and double-layer polyelectrolyte coating, respectively. Thus, PAA-cys-PAH-GO was successfully developed for oral delivery of PYM as anti-cancer therapy, and may provide further insight for oral administration of GO-based nanomaterials.

c-Fos Repression by Piwi Regulates Drosophila Ovarian Germline Formation and Tissue Morphogenesis.

Drosophila melanogaster Piwi functions within the germline stem cells (GSCs) and the somatic niche to regulate GSC self-renewal and differentiation. How Piwi influences GSCs is largely unknown. We uncovered a genetic interaction between Piwi and c-Fos in the somatic niche that influences GSCs. c-Fos is a proto-oncogene that influences many cell and developmental processes. In wild-type ovarian cells, c-Fos is post-transcriptionally repressed by Piwi, which destabilized the c-Fos mRNA by promoting the processing of its 3' untranslated region (UTR) into Piwi-interacting RNAs (piRNAs). The c-Fos 3' UTR was sufficient to trigger Piwi-dependent destabilization of a GFP reporter. Piwi represses c-Fos in the somatic niche to regulate GSC maintenance and differentiation and in the somatic follicle cells to affect somatic cell disorganization, tissue dysmorphogenesis, oocyte maturation arrest, and infertility.

An Illumination-Assisted Flexible Self-Powered Energy System Based on a Li-O2 Battery.

The flexible Li-O2 battery is suitable to satisfy the requirements of a self-powered energy system, thanks to environmental friendliness, low cost, and high theoretical energy density. Herein, a flexible porous bifunctional electrode with both electrocatalytic and photocatalytic activity was synthesized and introduced as a cathode to assemble a high-performance Li-O2 battery that achieved an overpotential of 0.19 V by charging with the aid of solar energy. As a proof-of-concept application, a flexible Li-O2 battery was constructed and integrated with a solar cell via a scalable encapsulate method to fabricate a flexible self-powered energy system with excellent flexibility and mechanical stability. Moreover, by exploring the evolution of the electrode morphology and discharge products (Li2 O2 ), the charging process of the Li-O2 battery powered by solar energy and solar cell was demonstrated.

In Situ CVD Derived Co-N-C Composite as Highly Efficient Cathode for Flexible Li-O2 Batteries.

To promote the development of high energy Li-O2 batteries, it is important to design and construct a suitable and effective oxygen-breathing cathode. Herein, activated cobalt-nitrogen-doped carbon nanotube/carbon nanofiber composites (Co-N-CNT/CNF) as the effective cathodes for Li-O2 batteries are prepared by in situ chemical vapor deposition (CVD). The unique architecture of these electrodes facilitates the rapid oxygen diffusion and electrolyte penetration. Meanwhile, the nitrogen-doped carbon nanotube/carbon nanofiber (N-CNT/CNF) and Co/CoNx serve as reaction sites to promote the formation/decomposition of discharge product. Li-O2 batteries with Co-N-CNT/CNF cathodes exhibit superior electrochemical performance in terms of a positive discharge plateau (2.81 V) and a low charge overpotential (0.61 V). Besides, Li-O2 batteries also present a high discharge capacity (11512.4 mAh g-1 at 100 mA g-1 ), and a long cycle life (130 cycles). Meanwhile, the Co-N-CNT/CNF cathode also has an excellent flexibility, thus the assembled flexible battery with Co-N-CNT/CNF can work normally and hold a wonderful capacity rate under various bending conditions.

Highly time-resolved aerosol characteristics during springtime in Weizhou Island.

A single particle aerosol mass spectrometer was deployed to measure the changes of single particle species and sizes during March 2015 in Weizhou Island of the Beibu Gulf, Guangxi province, South China. In this campaign, a total of 3,100,597 particles were sized, and 25.8% particles with both positive and negative mass spectrum were collected and 24.8% characterized in combination with the ART-2a neural network algorithm. The distribution of sized particles was mainly in from 520 to 600nm, and the diameters ranging from 340 to 1000nm accounted for above 90%. Eight types of particles were classified: Elemental Carbon containing (EC), Organic Carbon containing (OC), EC and OC combined containing particles, Na containing particles, K containing particles (K), Levoglucosan containing particles, mineral containing particles, and Heavy Metal containing particles (HM). EC, OC and K were the major containing particles, which accounted for 84.3% in the eight types particles. The relative ratio and size distribution of the three types were EC (48.1%, 620nm), OC (12.7%, 440nm), and K (23.5%, 600nm), respectively. The three types of particles were a bit increasing ratios compared with those in clean periods during haze pollution periods. Combined with the back-trajectory results from the Hysplit-4 model and local pollution sources revealed that the ambient air quality on the Weizhou Island may be influenced by biomass burning in the Indochina Peninsula (biomass burning in the Indochina Peninsula) from the transportation on higher level atmospheric layer and by mainland of south China located northeast of Weizhou Island on the ground.

Ultrathin, Lightweight, and Wearable Li-O2 Battery with High Robustness and Gravimetric/Volumetric Energy Density.

An ultrathin, lightweight, and wearable Li-O2 battery with a novel segmented structure is first fabricated by employing a "break up the whole into parts" strategy. Superior battery performance including low overpotential, high specific capacity, good rate capability, excellent cycle stability, and high gravimetric/volumetric energy density (294.68 Wh kg-1 /274.06 Wh L-1 ) is successfully achieved even under repeatedly various deformation.

Migrant elders in Hainan, China, report better health and lower depression than local-born elderly residents.

BACKGROUND: The number of migrant elders is increasing due to ageing of the global population and increasing life expectancy. There is accumulating evidence of the impact of internal or international migration on health. AIM: To compare the health and depression of local and migrant elders in Hainan province. SUBJECTS AND METHODS: Health and depression were assessed by the Self-Rated Health Measurement Scale Version 1.0 (SRHMS V1.0) and the Geriatric Depression Scale (GDS), respectively. The relationship between health and depression was investigated, along with the three sub-scales of SRHMS and the potential independent variables. RESULTS: In total, 564 valid questionnaires were returned. Migrant elders were younger, had higher education levels and monthly income, and lower prevalence rates of chronic diseases than the local elders. The SRHMS scores were significantly higher, while the GDS scores were statistically lower in the migrant elders than the locals. Depression was negatively correlated with health (r = -0.674, p = 0.0000). Moreover, the three sub-scales of SRHMS were correlated with age, birth place, marital status, chronic diseases, GDS and/or educational level. CONCLUSION: Migrant elders self-reported better health and lower depression compared to the local elders. Differences in age, education, monthly income and chronic diseases might be influencing factors.

Novel p-Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells.

Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu9S5 nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6-30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS2, CIGSe, CZTS, etc.), for their performance improvement.

Boundary extension: Insights from signal detection theory.

After viewing a scene, people often remember having seen more of the world than was originally visible, an error referred to as boundary extension. Despite the large number of studies on this phenomenon, performance has never been considered in terms of signal detection theory (SDT). We report two visual memory experiments that allowed us to explore boundary extension in terms of SDT. In our experiments, participants first studied pictures presented as close-up or wide-angle views. At test, either the identical view or a different view (a closer or wider angle version of the same scene) were presented and participants rated the test image as being the same or different than before on a 6-point scale. We found that both discrimination sensitivity and bias contributed to the boundary extension effect. The discrimination sensitivity difference was at least 28%, and its presence refuted the hypothesis that boundary extension was due solely to participants' response bias to label test pictures as more wide-angled. Instead, our results support the idea that participants' responses reflect false memory beyond the view (i.e., a more wide-angle view of the world).

Aircraft measurements of SO2, NOx, CO, and O3 over the coastal and offshore area of Yellow Sea of China.

In order to investigate long-range transport of the air pollution in the East Asia, air pollutants, including SO2, NOx, CO, and O3, were observed by aircraft measurement over the coastal and offshore area of Yellow Sea of China in April 2011. NOx and SO2 seemed to become moderate in recent years, and the concentrations during the whole observations ranged from 0.49 to 9.57 ppb and from 0.10 to 16.02 ppb, respectively. The high concentrations of CO were measured with an average value of 0.98 ppm. The measured O3 average concentration was 76.25 ppb, which showed a higher level comparing with the results from some previous studies. Most of the results for the concentration values generally followed the typical characteristic of vertical and spatial distribution, which were "low altitude > high altitude" and "land/coastal > sea," respectively. Transport of polluted air mass from the continent to the aircraft measurement area was confirmed in some days during the observation by the meteorological analysis, while the measurement results supposed to represent the background level of the pollutants in rest days. Additionally, some small-scale air pollution plumes were observed. Significant positive correlations between NOx and SO2 indicated that these two species originated from the same region. On the other hand, good positive correlations between NOx and O3 found during 2-day flight suggested that the O3 formation was probably under "NOx-limited" regime in these days.

Characteristics of particulate-bound polycyclic aromatic hydrocarbons emitted from industrial grade biomass boilers.

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic or mutagenic and are important toxic pollutants in the flue gas of boilers. Two industrial grade biomass boilers were selected to investigate the characteristics of particulate-bound PAHs: one biomass boiler retro-fitted from an oil boiler (BB1) and one specially designed (BB2) biomass boiler. One coal-fired boiler was also selected for comparison. By using a dilution tunnel system, particulate samples from boilers were collected and 10 PAH species were analyzed by gas chromatography-mass spectrometry (GC-MS). The total emission factors (EFs) of PAHs ranged from 0.0064 to 0.0380 mg/kg, with an average of 0.0225 mg/kg, for the biomass boiler emission samples. The total PAH EFs for the tested coal-fired boiler were 1.8 times lower than the average value of the biomass boilers. The PAH diagnostic ratios for wood pellets and straw pellets were similar. The ratio of indeno(1,2,3-cd)pyrene/[indeno(1,2,3-cd)pyrene+benzo(g,h,i)perylene] for the two biomass boilers was lower than those of the reference data for other burning devices, which can probably be used as an indicator to distinguish the emission of biomass boilers from that of industrial coal-fired boilers and residential stoves. The toxic potential of the emission from wood pellet burning was higher than that from straw pellet burning, however both of them were much lower than residential stove exhausts.