Phosphorus-based soil prophylactics for managing Pb contamination in soil: Slow-release kinetics and microbiological effects.

Soil remediation poses significant challenges due to its spatial heterogeneity, surpassing the complexities of atmospheric and water remediation. This study introduces an innovative approach to prevent soil heavy metal pollution by developing three phosphorus slow-release heavy metal soil prophylactic agents (SLPs) - Sap-11, Sap-12, and Sap-21. At a liquid-to-solid ratio of 1:20, the three types of SLPs achieve phosphorus sustained slow release amounts of 1.586 g/L, 4.259 g/L, and 1.444 g/L within 30 days, respectively. Over a cultivation period of 120 days, after amendment with the three SLPs, the surface soil demonstrates stabilization capacities for Pb of 29.56 mg/g, 46.24 mg/g, and 25.77 mg/g, respectively, representing enhancements of 283.64 %, 500.12 %, and 250.74 % compared to the control. Firstly, the direct contribution of P (up to 3.778 mg/g) released from SLPs chemically binding with Pb, and secondly, a significant proportion of the indirect contribution originating from the microbial activity and soil organic matter. In summary, SLP emerges as an effective strategy for soil heavy metal management, stabilizing heavy metals by stimulating the soil's inherent physiological and biochemical reactions. This approach provides a practical solution for the application of P-containing materials and introduces novel perspectives for soil heavy metal management strategies.

In Vitro and In Vivo Evaluating Bioaccessibility, Bioavailability, and Antioxidant Activities of Butterfly Pea Flower Containing Bioactive Constitutes.

The antioxidant properties of butterfly pea flower (BF), which is rich in natural anthocyanins, have garnered significant attention. The impact of digestion and metabolism on BF extracts and evaluate their subsequent antioxidant activities in vivo were explored in the present study. After in vitro digestion, 42.03 ± 2.74% of total anthocyanins from BF extracts remained, indicating a negative influence of the digestion process on the bioaccessibility of phenolic compounds derived from BF. Furthermore, UPLC-LTQ-Orbitrap-MS2 analysis identified a total of four prototypes and twenty-seven metabolites in rat plasma or urine samples following the intake of BF extracts. The kinetics of key metabolites including delphinidin 3-glucoside (D3G), cyanidin-3-glucoside (C3G), and 4-hydroxybenzoic acid were subsequently determined in blood, and the Cmax values were 69.034 ± 8.05 nM and 51.65 ± 3.205 nM. These key metabolites derived from BF anthocyanins, including C3G and D3G, and flavonoid quercetin exhibited main antioxidant attributes that improved the plasmic and hepatic activities of various antioxidant enzymes and the total antioxidant capacity (T-AOC) and malondialdehyde (MDA) in a D-galactose-induced rat model. These findings provide insights into the bioaccessibility and bioavailability of bioactive constitutes derived from BF extracts, which are crucial for determining the actual efficacy of BF as well as developing functional foods based on BF.

Lineage frequency time series reveal elevated levels of genetic drift in SARS-CoV-2 transmission in England.

Genetic drift in infectious disease transmission results from randomness of transmission and host recovery or death. The strength of genetic drift for SARS-CoV-2 transmission is expected to be high due to high levels of superspreading, and this is expected to substantially impact disease epidemiology and evolution. However, we don't yet have an understanding of how genetic drift changes over time or across locations. Furthermore, noise that results from data collection can potentially confound estimates of genetic drift. To address this challenge, we develop and validate a method to jointly infer genetic drift and measurement noise from time-series lineage frequency data. Our method is highly scalable to increasingly large genomic datasets, which overcomes a limitation in commonly used phylogenetic methods. We apply this method to over 490,000 SARS-CoV-2 genomic sequences from England collected between March 2020 and December 2021 by the COVID-19 Genomics UK (COG-UK) consortium and separately infer the strength of genetic drift for pre-B.1.177, B.1.177, Alpha, and Delta. We find that even after correcting for measurement noise, the strength of genetic drift is consistently, throughout time, higher than that expected from the observed number of COVID-19 positive individuals in England by 1 to 3 orders of magnitude, which cannot be explained by literature values of superspreading. Our estimates of genetic drift suggest low and time-varying establishment probabilities for new mutations, inform the parametrization of SARS-CoV-2 evolutionary models, and motivate future studies of the potential mechanisms for increased stochasticity in this system.

Effect of voice training intervention on swallowing function in patients with head and neck cancer undergoing radiotherapy: A randomized controlled trial.

PURPOSE: We aimed to evaluate the effect of voice training in patients with head and neck cancer who were undergoing radiotherapy. METHOD: This study used a randomized controlled trial design. IBM SPSS 26.0 was used to randomly divide 74 patients into a control group and an experimental group. The control group followed a swallowing exercises program, and the experimental group additionally received ABCLOVE voice training. Both training programs continued throughout the entire radiotherapy cycle. We compared standardized swallowing assessment (SSA), maximum phonation time (MPT), the Voice Handicap Index-10, and incidence of complications such as difficulty opening the mouth, malnutrition, and aspiration between the two groups at T1 (0 radiotherapy sessions, before radiotherapy), T2 (15-16 radiotherapy sessions, middle of radiotherapy), and T3 (30-32 radiotherapy sessions, end of radiotherapy). RESULTS: 70 participants completed this study. Swallowing function and MPT intergroup and interaction effects were statistically significant between the two groups (P < 0.05). At the end of radiotherapy (T3), the SSA score (20.77 ± 1.96) and MPT (10.98 ± 1.75) s in the experimental group were superior to those in the control group (SSA: 22.06 ± 2.38 and MPT: 9.49±1.41 s), with statistical significance (P<0.05). Moreover, the incidence of malnutrition and aspiration in the experimental group was lower than that in the control group (P < 0.05). CONCLUSION: Voice training can improve swallowing function and MPT and reduce complications related to swallowing disorders in patients with head and neck cancer.

Assessment of sewer connectivity in the United States and its implications for equity in wastewater-based epidemiology.

Wastewater-based epidemiology is a promising public health tool that can yield a more representative view of the population than case reporting. However, only about 80% of the U.S. population is connected to public sewers, and the characteristics of populations missed by wastewater-based epidemiology are unclear. To address this gap, we used publicly available datasets to assess sewer connectivity in the U.S. by location, demographic groups, and economic groups. Data from the U.S. Census' American Housing Survey revealed that sewer connectivity was lower than average when the head of household was American Indian and Alaskan Native, White, non-Hispanic, older, and for larger households and those with higher income, but smaller geographic scales revealed local variations from this national connectivity pattern. For example, data from the U.S. Environmental Protection Agency showed that sewer connectivity was positively correlated with income in Minnesota, Florida, and California. Data from the U.S. Census' American Community Survey and Environmental Protection Agency also revealed geographic areas with low sewer connectivity, such as Alaska, the Navajo Nation, Minnesota, Michigan, and Florida. However, with the exception of the U.S. Census data, there were inconsistencies across datasets. Using mathematical modeling to assess the impact of wastewater sampling inequities on inferences about epidemic trajectory at a local scale, we found that in some situations, even weak connections between communities may allow wastewater monitoring in one community to serve as a reliable proxy for an interacting community with no wastewater monitoring, when cases are widespread. A systematic, rigorous assessment of sewer connectivity will be important for ensuring an equitable and informed implementation of wastewater-based epidemiology as a public health monitoring system.

Rediversification following ecotype isolation reveals hidden adaptive potential.

Microbial communities play a critical role in ecological processes, and their diversity is key to their functioning. However, little is known about whether communities can regenerate ecological diversity following ecotype removal or extinction and how the rediversified communities would compare to the original ones. Here, we show that simple two-ecotype communities from the E. coli long-term evolution experiment (LTEE) consistently rediversified into two ecotypes following the isolation of one of the ecotypes, coexisting via negative frequency-dependent selection. Communities separated by more than 30,000 generations of evolutionary time rediversify in similar ways. The rediversified ecotype appears to share a number of growth traits with the ecotype it replaces. However, the rediversified community is also different from the original community in ways relevant to the mechanism of ecotype coexistence-for example, in stationary phase response and survival. We found substantial variation in the transcriptional states between the two original ecotypes, whereas the differences within the rediversified community were comparatively smaller, although the rediversified community showed unique patterns of differential expression. Our results suggest that evolution may leave room for alternative diversification processes even in a maximally reduced community of only two strains. We hypothesize that the presence of alternative evolutionary pathways may be even more pronounced in communities of many species where there are even more potential niches, highlighting an important role for perturbations, such as species removal, in evolving ecological communities.

Identification and Validation of Reference Genes for RT-qPCR Analysis in Reed Canary Grass during Abiotic Stress.

Reed canary grass (Phalaris arundinacea L.) is known for its tolerance to drought, heavy metals, and waterlogging, making it a popular choice for forage production and wetland restoration in the Qinghai-Tibet Plateau (QTP). To accurately assess gene expression in reed canary grass under different abiotic stresses, suitable reference genes need to be identified and validated. Thirteen candidate reference gene sequences were selected and screened using RT-qPCR to detect their expression levels in reed canary grass leaves under drought, salt, cadmium, and waterlogging stresses. Four algorithms were used to assess the stability of the expression levels of the candidate reference genes. The most stably expressed genes were UBC and H3 under drought Cd, ETF and CYT under salt stress, and ETF and TUB under waterlogging stress. GAPDH was found to be less stable under abiotic stresses. PIP-1, PAL, NAC 90, and WRKY 72A were selected as response genes for quantitative expression assessment under drought, salt, Cd, and waterlogging stresses to confirm the accuracy of the selected stable reference genes. These results provide a theoretical reference for assessing gene expression in reed canary grass under abiotic stresses.

Quantification of bone quality and distribution of the proximal humerus with dual-energy computed tomography.

Background: The proximal humerus is a common site of osteoporotic fractures, and bone quality is a predictor of surgical reduction quality. Dual-energy computed tomography (DECT) is assuming an increasingly important role in the quantification of bone mineral density (BMD) due it is ability to perform three-material decomposition. We aimed to analyze the bone quality and distribution of the proximal humerus with DECT quantitatively. Methods: Sixty-five consecutive patients (average age 49.5±15.2 years; male: female ratio 32:33) without proximal humerus fractures who had undergone DECT were retrospectively selected. The humeral head was divided into 4 regions on a cross section in the medial plane between the greater tuberosity and the surgical neck. The quantitative parameters, including virtual noncalcium (VNCa) value, computed tomography value of calcium (CaCT), computed tomography value of mixed-energy images (regular CT value) (rCT), and relative calcium density (rCaD), were measured. The correlations between the quantitative parameters and age and body mass index (BMI) were analyzed, and the correlations of age, sex, BMI, region of the humeral head, and VNCa value on CaCT were evaluated. Results: The differences in CaCT, rCT, and rCaD between the 4 regions of proximal humerus were statistically significant (P<0.001), while the difference in VNCa values was not (P=0.688). The calcium concentration (CaCT and rCaD) was the densest in the posteromedial zone. The differences of CaCT, rCT, and rCaD between males and females in the 4 regions of proximal humerus were statistically significant (P<0.05), while those of the posterolateral zone were not (rCT; P>0.05). The differences in VNCa values between males and females were also not significant (P>0.05). Multivariable linear regression analysis indicated that sex, age, BMI, regions, and VNCa were significant (P<0.05) predictors of the CaCT value. Conclusions: The concentration of calcium was the densest in the posteromedial region of proximal humerus, and the VNCa value of DECT may be used for quantifying the BMD of the proximal humerus.

Considerable contribution of secondary aerosol to wintertime haze pollution in new target of the latest clean air actions in China.

Fine particulate matter (PM2.5) in Northeast China was targeted by national-level clean air policy for the first time in 2022, with the release of Action Plan to eliminate heavy air pollution events. In this study, we investigated sources of PM2.5 during three successive winters in Harbin, a megacity in Northeast China, based on observational results from several recent campaigns in 2018-2021. During the 2020-2021 campaign, daytime and nighttime samples were collected in specific months in addition to 24-h integrated measurements, and the two sets of samples were combined in different ways to run a positive matrix factorization model. The source apportionment results suggested that the resolved secondary organic carbon (SOCPMF) had an uncertainty of ∼12%. Secondary aerosols were found to show the following features for the typical winters without agricultural fires. First, SOCPMF could be properly constrained by results from another widely-used approach for SOC estimation, the elemental carbon-tracer method. Second, secondary PM2.5 calculated using SOCPMF and secondary inorganic ions were generally in line with the independent estimations based on air quality data. Third, secondary components accounted for more than 50% of PM2.5 on average and contributed even more significantly during severe haze episodes, which were the focus of the latest Action Plan. This study also found that the wintertime PM2.5 decreased more slowly during 2017-2021 compared to 2013-2017, by ∼1 and 10 µg/m3 per year, respectively, for the metropolitan area where Harbin is located at. Our results highlighted the importance of secondary aerosols for further improving air quality in Northeast China, and for avoiding heavy pollution as required by the latest Action Plan.

Anthocyanin-Rich Butterfly Pea Flower Extract Ameliorating Low-Grade Inflammation in a High-Fat-Diet and Lipopolysaccharide-Induced Mouse Model.

This study aimed to explore the enhancive effects of butterfly pea flower (BF) extracts on metabolic and immune homeostasis in a low-grade inflammation mouse model. The BF extract was found to contain mainly anthocyanins among other flavonoids. BF supplementation alleviated metabolic endotoxemia by lowering the plasma glucose, lipopolysaccharide (LPS), and tumor necrosis factor-α (TNF-α) levels and restored lipid metabolism and the balance between Treg and Th17 cells, thereby inhibiting the dysfunctional liver and abdominal white adipose tissues. BF extract increased the tight junction protein expression and reduced the expression of proinflammatory cytokines, therefore sustaining the colonic mucosa structure. Furthermore, BF extracts reshaped the gut microbiota structure characterized by significantly promoted SCFA-producing gut microbiota such as Akkermansia and Butyricicoccaceae. Additionally, BF extracts enhanced fecal primary bile acid (BA) levels and modulated bile acid signaling in the liver and ileum to facilitate BA synthesis for the restoration of lipid metabolism. In summary, anthocyanin-enriched BF extracts alleviated the profound negative dietary alterations and helped maintain the metabolic health by modulating the various aspects of the gut microenvironment and enhancing hepatic bile acid synthesis.

Agricultural fire impacts on brown carbon during different seasons in Northeast China.

Brown carbon (BrC) represents not only a major component of haze pollution but also a non-negligible contributor to positive radiative forcing, making it a key species for coordinating air quality and climate policies. In China, field observations on BrC remain limited given the highly variable emission sources and meteorological conditions across different regions. Here we focused on the optical properties of BrC in a distinct but rarely studied megacity in Northeast China, which is within a major agricultural region and experiences extremely cold winter. Agricultural fires were evident in April of 2021 and the fall of 2020, although open burning was strictly prohibited. Such emissions enhanced BrC's mass absorption efficiency at 365 nm (MAE365), more efficiently by the fall fires which were inferred to have relatively high combustion efficiencies (CE). After taking CE into consideration, the relationships between MAE365 and the levoglucosan to organic carbon ratio (a measure of the significance of agricultural fire influence) roughly converged for the fire episodes in different seasons, including those identified in February and March of 2019 by a previous campaign. Agricultural fires also influenced the determination of absorption Ångström exponent (AAE), by resulting in non-linearity for BrC's absorption spectra shown on ln-ln scale. Based on three indicators developed by this study, the non-linearity was inferred to be caused by similar chromophores although the fires were characterized by various CE levels in different seasons. In addition, for the samples without significant influence of open burning, coal combustion emissions were identified as the dominant influencing factor for MAE365, whereas none solid link was found between the solution-based AAE and aerosol source.

Rediversification Following Ecotype Isolation Reveals Hidden Adaptive Potential.

Microbial communities play a critical role in ecological processes, and their diversity is key to their functioning. However, little is known about if communities can regenerate ecological diversity following species removal or extinction, and how the rediversified communities would compare to the original ones. Here we show that simple two-ecotype communities from the E. coli Long Term Evolution Experiment (LTEE) consistently rediversified into two ecotypes following the isolation of one of the ecotypes, coexisting via negative frequency-dependent selection. Communities separated by more than 30,000 generations of evolutionary time rediversify in similar ways. The rediversified ecotype appears to share a number of growth traits with the ecotype it replaces. However, the rediversified community is also different compared to the original community in ways relevant to the mechanism of ecotype coexistence, for example in stationary phase response and survival. We found substantial variation in the transcriptional states between the two original ecotypes, whereas the differences within the rediversified community were comparatively smaller, but with unique patterns of differential expression. Our results suggest that evolution may leave room for alternative diversification processes even in a maximally reduced community of only two strains. We hypothesize that the presence of alternative evolutionary pathways may be even more pronounced in communities of many species, highlighting an important role for perturbations, such as species removal, in evolving ecological communities.

α-D-1,3-glucan from Radix Puerariae thomsonii improves NAFLD by regulating the intestinal flora and metabolites.

Radix Puerariae thomsonii, the root of the botanical family Fabaceae species Pueraria montana var. thomsonii (Benth.) MR Almeida, can be used as food or medicine. Polysaccharides are important active constituents of this root. A low molecular weight polysaccharide, RPP-2 having α-D-1,3-glucan as the main chain, was isolated and purified. RPP-2 could promote the growth of probiotics in-vitro. Therefore, the effects of RPP-2 on a high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) C57/BL6J mouse models were investigated. RPP-2 could reduce HFD-induced liver injury by reducing inflammation, glucose metabolism, and steatosis, thereby improving NAFLD. RPP-2 regulated the abundances of intestinal floral genera Flintibacter, Butyricicoccus, and Oscillibacter, and their metabolites Lipopolysaccharide (LPS), bile acids, and short-chain fatty acids (SCFAs), thereby improving inflammation, lipid metabolism, and energy metabolism signaling pathways. These results confirmed that RPP-2 play a prebiotic role by regulating intestinal flora and microbial metabolites, playing a multi-pathway and multi-target role in improving NAFLD.

Synergistically Achieving Superior Sodium Storage of Metal Selenides by Constructing N-Doped Carbon Foams and Utilizing Cu-Driven Replacement Reaction.

Metal selenides are considered as one of the most promising anode materials for Na-ion batteries owing to high specific capacity and relatively higher electronic conductivity compared with metal sulfides or oxides. However, such anodes still suffer from huge volume change upon repeated Na+ insertion/extraction processes and simultaneously undergo severe shuttle effect of polyselenides, thus leading to poor electrochemical performance. Herein, a facile chemical-blowing and selenization strategy to fabricate 3D interconnected hybrids built from metal selenides (MSe, M = Mn, Co, Cr, Fe, In, Ni, Zn) nanoparticles encapsulated in in situ formed N-doped carbon foams (NCFs) is reported. Such hybrids not only provide ultrasmall active nanobuilding blocks (≈15 nm), but also efficiently anchor them inside the conductive NCFs, thus enabling both high-efficiency utilization of active components and high structural stability. On the other hand, Cu-driven replacement reaction is utilized for efficiently inhibiting the shuttle effect of polyselenides in ether-based electrolyte. Benefiting from the combined merits of the unique MSe@NCFs and the utilization of the conversion of metal selenides to copper selenides, the as-obtained hybrids (MnSe as an example) exhibit superior rate capability (386.6 mAh g-1 up to 8 A g-1 ) and excellent cycling stability (347.7 mAh g-1 at 4.0 A g-1 after 1200 cycles).

Radix Puerariae thomsonii polysaccharide (RPP) improves inflammation and lipid peroxidation in alcohol and high-fat diet mice by regulating gut microbiota.

Polysaccharides are the important active constituents of Radix Puerariae thomsonii. Numerous studies have shown that polysaccharides can regulate gut microbiota, repair intestinal barrier, and affect the microbiota-intestine-liver axis, thereby showing therapeutic effects on metabolic disorders. In this study, Radix Puerariae thomsonii polysaccharide (RPP) was extracted from Radix Puerariae thomsonii. The average Mw of RPP was determined to be 1.09 × 105 Da and the monosaccharide composition showed it consisted of glucose. The effects and underlying mechanisms of RPP on fatty liver were studied using C57/BL6J mice induced by alcohol and high-fat diet. The results showed that the oral supplementation of RPP could alleviate alcohol and high-fat diet-induced hepatic injury and steatosis. RPP also promoted intestinal barrier integrity and reduced inflammation through NF-κB signaling pathway. RPP could ameliorate the lipid peroxidation by AMPK/NADPH oxidase signaling pathway. Additionally, these improvements might be related to the enrichment of intestinal bacteria Parabacteroides (promote intestinal barrier integrity) and Prevotellaceae UCG 001 (activation of AMPK signaling pathway). These results demonstrated that RPP could improve inflammation and lipid peroxidation in the alcohol and high-fat diet mouse by restoring the intestinal barrier integrity and regulating the gut microbiota. This suggested that RPP was a potential food supplement for the treatment of fatty liver disease.

FtUGT79A15 is responsible for rutinosylation in flavonoid diglycoside biosynthesis in Fagopyrum tataricum.

Tartary buckwheat shows health benefits with its high antioxidant activity and abundant flavonoid content. However, glycosylated flavonoid accumulation patterns and their molecular basis remain unidentified in Tartary buckwheat. Here, our metabolomics analysis revealed that F3'H branching was the major flavonoid metabolic flux in Tartary buckwheat. Interestingly, metabolome results also showed that the most abundant flavonoids were mainly in the glycosylated form, including flavonoid glycosides and flavonoid diglycosides in Tartary buckwheat. However, the flavonoid glycosides glycosyltransferase (GGT) gene catalyzing the second glycosylation step of flavonoid diglycoside has not been discovered yet in Tartary buckwheat. Thus, we explored GGT genes in the transcriptome-metabolome correlation network and confirmed that FtUGT79A15 showed the rhamnosyltransferase activity to catalyze quercetin 3-O-glucoside to rutin invitro and inplanta. Overall, FtUGT79A15 was identified to involve in the flavonoid diglycoside biosynthesis pathway in Tartary buckwheat.

Roles of microRNAs in metabolic reprogramming of breast cancer.

Breast cancer cells exhibit deregulated metabolism. They require increased glucose uptake and glycolysis-associated enzymes to produce adenosine triphosphate by aerobic glycolysis rather than oxidative phosphorylation. Glutamine metabolism and fatty acid synthesis are also enhanced to meet the rapid and sustained cell growth. Triple-negative breast cancer and human epidermal growth factor receptor-2-positive breast cancers demonstrate significant metabolic reprogramming with increased levels of glucose and glutamine metabolism. Increasing evidences also suggest that micro-ribonucleic acids play important roles in the regulation of metabolic enzymes of breast cancer cells in post-transcriptional manner. Human epidermal growth factor receptor-2 and oestrogen receptor signalling pathways could have crosstalk with micro-ribonucleic acids in metabolic regulation network. The current narrative review was planned to go through recent advances on the role of micro-ribonucleic acids on metabolic reprogramming in breast cancer cells.

Exploring chemical changes of the haze pollution during a recent round of COVID-19 lockdown in a megacity in Northeast China.

COVID-19 rebounded in China in January 2021, with Heilongjiang as one of the worst-affected provinces. This resulted in a new round of lockdown in Harbin, the capital city of Heilongjiang, from 20 January to 22 February of 2021. A field campaign was conducted to explore the responses of haze pollution in Harbin to the lockdown. Levoglucosan was used to reflect biomass burning emissions, while the molar ratio of sulfur (the sum of sulfur dioxide and sulfate) to nitrogen (the sum of nitrogen dioxide and nitrate), i.e., RS/N, was used as an indicator for the relative importance of coal combustion and vehicle emissions. Based on a synthesis of the levoglucosan and RS/N results, reference period was selected with minimal influences of non-lockdown-related emission variations. As indicated by the almost unchanged sulfur dioxide concentrations, coal combustion emissions were relatively stable throughout the lockdown and reference periods, presumably because the associated activities, e.g., heating supply, power generation, etc., were usually uninterruptible. On the other hand, as suggested by the increase of RS/N, vehicle emissions were considerably reduced during lockdown, likely due to the stay-at-home orders. Compared to results from the reference samples, the lockdown period exhibited higher levels of ozone and various indicators for secondary aerosol formation, pointing to an enhancement of secondary pollution. In addition, photochemistry-related reactions in aqueous phase appeared to be present during the lockdown period, which have not been reported in the frigid atmosphere over Northeast China.

New open burning policy reshaped the aerosol characteristics of agricultural fire episodes in Northeast China.

The massive agricultural sector in the Northeast Plain, which is of great importance for the food security in China, results in a huge amount of crop residues and thus substantial concern on haze pollution due to biomass burning (BB). To seek for effective control measures on BB emissions, a dramatic transition of open burning policy occurred in Heilongjiang Province, from the "legitimate burning" policy released in 2018 to the "strict prohibition" policy implemented in 2019 and beyond. Here we explored the BB aerosols during 2020-2021 in Harbin, the capital city of Heilongjiang. Although open burning was strictly prohibited by mandatory bans, agricultural fires were not actually eliminated, as indicated by the levoglucosan levels and fire count results. In general, the BB aerosols in Harbin were attributed to the overlaying of household burning and agricultural fire emissions. The former factor laid the foundation of biomass burning impacts, with BB contributions to organic carbon and elemental carbon (fBBOC and fBBEC) of 35 and 47%, respectively. The latter further enhanced the BB impacts during specific episodes breaking out in the spring of 2021 as well as the fall of 2020, when fBBOC and fBBEC increased to 64 and 57%, respectively. In addition, comparing to the fires of 2018-2019 which occurred in winter (in response to the "legitimate burning" policy), the agricultural fires were shifted to spring and fall in the 2020-2021 campaign, accompanied with an increase of combustion efficiency. This study illustrated how the agricultural fire emissions were influenced by the transition of open burning policy.

Primary nature of brown carbon absorption in a frigid atmosphere with strong haze chemistry.

Severe haze hovered over Harbin during the heating season of 2019-2020, making it one of the ten most polluted Chinese cities in January of 2020. Here we focused on the optical properties and sources of brown carbon (BrC) during the extreme atmospheric pollution periods. Enhanced formation of secondary BrC (BrCsec) was evident as relative humidity (RH) became higher, accompanied with a decrease of ozone but concurrent increases of aerosol water content and secondary inorganic aerosols. These features were generally similar to the characteristics of haze chemistry observed during winter haze events in the North China Plain, and indicated that heterogeneous reactions involving aerosol water might be at play in the formation of BrCsec, despite the low temperatures in Harbin. Although BrCsec accounted for a substantial fraction of brown carbon mass, its contribution to BrC absorption was much smaller (6 vs. 28%), pointing to a lower mass absorption efficiency (MAE) of BrCsec compared to primary BrC. In addition, emissions of biomass burning BrC (BrCBB) were inferred to increase with increasing RH, coinciding with a large drop of temperature. Since both the less absorbing BrCsec and the more absorbing BrCBB increased as RH became higher, the MAE of total BrC were largely unchanged throughout the measurement period. This study unfolded the contrast in the source apportionment results of BrC mass and absorption, and could have implications for the simulation of radiative forcing by brown carbon.