Dispersion Normalized PMF Provides Insights into the Significant Changes in Source Contributions to PM2.5 after the COVID-19 Outbreak.

Factor analysis utilizes the covariance of compositional variables to separate sources of ambient pollutants like particulate matter (PM). However, meteorology causes concentration variations in addition to emission rate changes. Conventional positive matrix factorization (PMF) loses information from the data because of these dilution variations. By incorporating the ventilation coefficient, dispersion normalized PMF (DN-PMF) reduces the dilution effects. DN-PMF was applied to hourly speciated particulate composition data from a field campaign that included the start of the COVID-19 outbreak. DN-PMF sharpened the morning coal combustion and rush hour traffic peaks and lowered the daytime soil, aged sea salt, and waste incinerator contributions that better reflect the actual emissions. These results identified significant changes in source contributions after the COVID-19 outbreak in China. During this pandemic, secondary inorganic aerosol became the predominant PM2.5 source representing 50.5% of the mean mass. Fireworks and residential burning (32.0%), primary coal combustion emissions (13.3%), primary traffic emissions (2.1%), soil and aged sea salt (1.2%), and incinerator (0.9%) represent the other contributors. Traffic decreased dramatically (70%) compared to other sources. Soil and aged sea salt also decreased by 68%, likely from decreased traffic.

Characteristic Analysis and Health Risk Assessment of PM2.5 and VOCs in Tianjin Based on High-Resolution Online Data.

This study leveraged 2019 online data of particulate matter (PM2.5) and volatile organic compounds (VOCs) in Tianjin to analyze atmospheric pollution characteristics. PM2.5 was found to be primarily composed of water-soluble ions, with nitrates as the dominant component, while VOCs were predominantly alkanes, followed by alkenes and aromatic hydrocarbons, with notable concentrations of propane, ethane, ethylene, toluene, and benzene. The receptor model identified six major sources of PM2.5 and seven major sources of VOCs. The secondary source is the main contribution source, while motor vehicles and coal burning are important primary contribution sources in PM2.5. And, industrial processes and natural gas volatilization were considered major contributors for VOCs. A health risk assessment indicated negligible non-carcinogenic risks but potential carcinogenic risks from trace metals As and Cr, and benzene within VOCs, underscoring the necessity for focused public health measures. A risk attribution analysis attributed As and Cr in PM to coal combustion and vehicular emissions. Benzene in VOCs primarily originates from fuel evaporation, and industrial and vehicular emissions. These findings underscore the potential for reducing health risks from PM and VOCs through enhanced regulation of emissions in coal, industry, and transportation. Such strategies are vital for advancing air quality management and safeguarding public health.

Analysis and recognition of a novel experimental paradigm for musical emotion brain-computer interface.

Musical emotions have received increasing attention over the years. To better recognize the emotions by brain-computer interface (BCI), the random music-playing and sequential music-playing experimental paradigms are proposed and compared in this paper. Two experimental paradigms consist of three positive pieces, three neutral pieces and three negative pieces of music. Ten subjects participate in two experimental paradigms. The features of electroencephalography (EEG) signals are firstly analyzed in the time, frequency and spatial domains. To improve the effect of emotion recognition, a recognition model is proposed with the optimal channels selecting by Pearson's correlation coefficient, and the feature fusion combining differential entropy and wavelet packet energy. According to the analysis results, the features of sequential music-playing experimental paradigm are more different among three emotions. The classification results of sequential music-playing experimental paradigm are also better, and its average results of positive, neutral and negative emotions are 78.53%, 72.81% and 77.35%, respectively. The more obvious the changes of EEG induced by the emotions, the higher the classification accuracy will be. After analyzing two experimental paradigms, a better way for music to induce the emotions can be explored. Therefore, our research offers a novel perspective on affective BCIs.

Assessing emission-driven changes in health risk of source-specific PM2.5-bound heavy metals by adjusting meteorological covariates.

Heavy metals (HMs) in PM2.5 gain much attention for their toxicity and carcinogenic risk. This study evaluates the health risks of PM2.5-bound HMs, focusing on how meteorological conditions affect these risks against the backdrop of PM2.5 reduction trends in China. By applying a receptor model with a meteorological normalization technique, followed by health risk assessment, this work reveals emission-driven changes in health risk of source-specific HMs in the outskirt of Tianjin during the implementation of China' second Clean Air Action (2018-2020). Sources of PM2.5-bound HMs were identified, with significant contributions from vehicular emissions (on average, 33.4 %), coal combustion (26.3 %), biomass burning (14.1 %), dust (11.7 %), industrial boilers (9.7 %), and shipping emission and sea salt (4.7 %). The source-specific emission-driven health risk can be enlarged or dwarfed by the changing meteorological conditions over time, demonstrating that the actual risks from these source emissions for a given time period may be higher or smaller than those estimated by traditional assessments. Meteorology contributed on average 56.1 % to the interannual changes in source-specific carcinogenic risk of HMs from 2018 to 2019, and 5.6 % from 2019 to 2020. For the source-specific noncarcinogenic risk changes, the contributions were 38.3 % and 46.4 % for the respective periods. Meteorology exerts a more profound impact on daily risk (short-term trends) than on annual risk (long-term trends). Such meteorological impacts differ among emission sources in both sign and magnitude. Reduced health risks of HMs were largely from targeted regulatory measures on sources. Therefore, the meteorological covariates should be considered to better evaluate the health benefits attributable to pollution control measures in health risk assessment frameworks.

Incidence of Pediatric Urinary Tract Infections Before and During the COVID-19 Pandemic.

IMPORTANCE: Urinary tract infection (UTI) is common in children, but the population incidence is largely unknown. Controversy surrounds the optimal diagnostic criteria and how to balance the risks of undertreatment and overtreatment. Changes in health care use during the COVID-19 pandemic created a natural experiment to examine health care use and UTI diagnosis and outcomes. OBJECTIVES: To examine the population incidence of UTI in children and assess the changes of the COVID-19 pandemic regarding UTI diagnoses and measures of UTI severity. DESIGN, SETTING, AND PARTICIPANTS: This retrospective observational cohort study used US commercial claims data from privately insured patients aged 0 to 17 years from January 1, 2016, to December 31, 2021. EXPOSURE: Time periods included prepandemic (January 1, 2016, to February 29, 2020), early pandemic (April 1 to June 30, 2020), and midpandemic (July 1, 2020, to December 31, 2021). MAIN OUTCOMES AND MEASURES: The primary outcome was the incidence of UTI, defined as having a UTI diagnosis code with an accompanying antibiotic prescription. Balancing measures included measures of UTI severity, including hospitalizations and intensive care unit admissions. Trends were evaluated using an interrupted time-series analysis. RESULTS: The cohort included 13 221 117 enrollees aged 0 to 17 years, with males representing 6 744 250 (51.0%) of the population. The mean incidence of UTI diagnoses was 1.300 (95% CI, 1.296-1.304) UTIs per 100 patient-years. The UTI incidence was 0.86 per 100 patient-years at age 0 to 1 year, 1.58 per 100 patient-years at 2 to 5 years, 1.24 per 100 patient-years at 6 to 11 years, and 1.37 per 100 patient-years at 12 to 17 years, and was higher in females vs males (2.48 [95% CI, 2.46-2.50] vs 0.180 [95% CI, 0.178-0.182] per 100 patient-years). Compared with prepandemic trends, UTIs decreased in the early pandemic: -33.1% (95% CI, -39.4% to -26.1%) for all children and -52.1% (95% CI, -62.1% to -39.5%) in a subgroup of infants aged 60 days or younger. However, all measures of UTI severity decreased or were not significantly different. The UTI incidence returned to near prepandemic rates (-4.3%; 95% CI, -32.0% to 34.6% for all children) after the first 3 months of the pandemic. CONCLUSIONS AND RELEVANCE: In this cohort study, UTI diagnosis decreased during the early pandemic period without an increase in measures of disease severity, suggesting that reduced overdiagnosis and/or reduced misdiagnosis may be an explanatory factor.

The response of daytime nitrate formation to source emissions reduction based on chemical kinetic and thermodynamic model.

Particulate nitrate is an important component of particulate matter and poses a significant threat to the ecosystem and human health. The gas-phase formation pathway of nitrate is extremely important, which mainly comprises the NO2 oxidation process triggered by OH radicals and the nitrate partitioning process. The response of nitrate to source emission reduction during different pollution periods remains unclear. Here, we applied the chemical kinetic and thermodynamics model to explore the importance oxidation process and partitioning process during different pollution periods based on high-time resolution observation data. The result indicated that with the aggravation of pollution, the partitioning process gradually ceases to be a limiting step in the formation of nitrates. The results of the influencing factor analysis indicate that NO2 concentration and aerosol pH values play a more significant role in the formation of nitrates. Specifically, during the clean period, nitrate formation is sensitive to both NO2 concentration and pH values, but during the pollution period, it becomes sensitive only to NO2 concentration. By combining source apportionment, we explored the response of nitrate formation to source emission reduction, and the results showed that the control of vehicle exhaust emissions and coal combustion sources is more effective in mitigating nitrate pollution. Additionally, this study also emphasized the importance of early prevention and control of pollution sources. This research provides scientific evidence for the precise management and control of nitrates.

Atmospheric environment characteristic of severe dust storms and its impact on sulfate formation in downstream city.

This study comprehensively investigated the impact of dust storms (DSs) on downstream cities, by selecting representative DS events. In this paper, we discussed the characteristics of meteorological conditions, air pollutants, PM2.5 components, and their influence on sulfate formation mechanisms. During DSs, strong winds, reaching speeds of up to 10 m/s, led to significant increases in PM10 and PM2.5, with maximum concentrations of 2684.5 and 429 µg/m3, respectively. Primary gaseous pollutants experienced substantial reductions, with decline rates of 48.1, 34.9, 36.8, and 9.0 % for SO2, NO2, NH3, and CO, respectively. Despite a notable increase in PM2.5 concentrations, only 7.6 % of the total mass of PM2.5 was attributed to ionic and carbonaceous components, a much lower value than observed before the DSs (77.3 %). Concentrations of Fe, Ti, and Mn exhibited increases by factors of 6.5-14.1, 10.4-17.0, and 1.6-4.7, respectively. In contrast to the significant decrease of >76.2 % in nitrogen oxidation ratio (NOR), sulfur oxidation ratio (SOR) remained at a relatively high level, displaying a strong positive correlation with high concentrations of Fe, Mn, and Ti. Quantitative analysis revealed an average increase of 0.187 and 0.045 µg/m3 in sulfate from natural sources and heterogeneous generation, respectively. The heterogeneous reaction on mineral dust was closely linked to atmospheric humidity, radiation intensity, the form of metal existence, and concentrations of it. High concentrations of titanium dioxide and iron­manganese oxides in mineral dust promoted heterogeneous oxidation of SO2 through photocatalysis during the daytime and metal ion catalysis during the nighttime. This study establishes that the metal components in mineral dust promote heterogeneous sulfate formation, quantifies the yield of sulfate generated as a result, and provides possible mechanisms for heterogeneous sulfate formation.

Disparities in Guideline Adherence for Febrile Infants in a National Quality Improvement Project.

BACKGROUND: Interventions aimed to standardize care may impact racial and ethnic disparities. We evaluated the association of race and ethnicity with adherence to recommendations from the American Academy of Pediatrics' clinical practice guideline for febrile infants after a quality improvement (QI) intervention. METHODS: We conducted a cross-sectional study of infants aged 8 to 60 days enrolled in a QI collaborative of 99 hospitals. Data were collected across 2 periods: baseline (November 2020-October 2021) and intervention (November 2021-October 2022). We assessed guideline-concordance through adherence to project measures by infant race and ethnicity using proportion differences compared with the overall proportion. RESULTS: Our study included 16 961 infants. At baseline, there were no differences in primary measures. During the intervention period, a higher proportion of non-Hispanic white infants had appropriate inflammatory markers obtained (2% difference in proportions [95% confidence interval (CI) 0.7 to 3.3]) and documentation of follow-up from the emergency department (2.5%, 95% CI 0.3 to 4.8). A lower proportion of non-Hispanic Black infants (-12.5%, 95% CI -23.1 to -1.9) and Hispanic/Latino infants (-6.9%, 95% CI -13.8 to -0.03) had documented shared decision-making for obtaining cerebrospinal fluid. A lower proportion of Hispanic/Latino infants had appropriate inflammatory markers obtained (-2.3%, 95% CI -4.0 to -0.6) and appropriate follow-up from the emergency department (-3.6%, 95% CI -6.4 to -0.8). CONCLUSIONS: After an intervention designed to standardize care, disparities in quality metrics emerged. Future guideline implementation should integrate best practices for equity-focused QI to ensure equitable delivery of evidence-based care.

Insights into discharge argon-mediated biofilm inactivation.

Formation of bacterial biofilms at solid-liquid interfaces creates numerous problems in biomedical sciences. Conventional sterilization and decontamination methods are not suitable for new and more sophisticated biomaterials. In this paper, the efficiency and effectiveness of gas discharges in the inactivation and removal of biofilms on biomaterials were studied. It was found that although discharge oxygen, nitrogen and argon all demonstrated excellent antibacterial and antibiofilm activity, gases with distinct chemical/physical properties underwent different mechanisms of action. Discharge oxygen- and nitrogen-mediated decontamination was associated with strong etching effects, which can cause live bacteria to relocate thus spreading contamination. On the contrary, although discharge argon at low powers maintained excellent antibacterial ability, it had negligible etching effects. Based on these results, an effective decontamination approach using discharge argon was established in which bacteria and biofilms were killed in situ and then removed from the contaminated biomaterials. This novel procedure is applicable for a wide range of biomaterials and biomedical devices in an in vivo and clinical setting.

Source apportionment of fine particulate matter at a megacity in China, using an improved regularization supervised PMF model.

The source apportionment of particulate matter plays an important role in solving the atmospheric particulate pollution. Positive matrix factorization (PMF) is a widely used source apportionment model. At present, high resolution online datasets are increasingly rich, but acquiring accurate and timely source apportionment results is still challenging. Integrating prior knowledge into modelling process is an effective solution and can yield reliable results. This study proposed an improved source apportionment method for the regularization supervised PMF model (RSPMF). This method leveraged actual source profile to guide factor profile for rapidly and automatically identifying source categories and quantifying source contributions. The results showed that the factor profile from RSPMF could be interpreted as seven factors and approach to actual source profile. Average source contributions were also an agreement between RSPMF and EPAPMF, including secondary nitrate (26 %, 27 %), secondary sulfate (23 %, 24 %), coal combustion (18 %, 18 %), vehicle exhaust (15 %, 15 %), biomass burning (10 %, 9 %), dust (5 %, 4 %), industrial emission (3 %, 3 %). The solutions of RSPMF also exhibited good generalizability during different episodes. This study reveals the superiority of supervised model, this model embeds prior knowledge into modelling process to guide model for obtaining more reliable results.

Abundant nitrogen oxide and weakly acidic environment synergistically promote daytime particulate nitrate pollution.

Nitrate is formed through the chemical production of gas-phase nitric acid and subsequent partitioning to the aerosol phase during the daytime. Many studies in the past separated these two aspects, even though they occur simultaneously in the atmosphere. To better understand the nitrate formation mechanism and effectively mitigate its production, it is necessary to consider the synergy between these two mechanisms. For this, we analyze hourly-speciated ambient observations data, with EK&TMA (Empirical Kinetic & Thermodynamic Modeling Approach) map to comprehensively explore the factors controlling nitrate production. Results show that precursor NO2 concentration and aerosol pH, which are related to anthropogenic activities, are the two major factors for chemical kinetics production and gas/particle thermodynamic partitioning processes respectively. Abundant NO2 and weakly acidic environments are favorable conditions for daytime particulate nitrate pollution, thus collaborative control of coal source, vehicle source, and dust source is needed to alleviate nitrate pollution.

Seed endophytic ammonia oxidizing bacteria in Elymus nutans transmit to offspring plants and contribute to nitrification in the root zone.

Background: Ammonia oxidizing bacteria (AOB) in soil are of great biological importance as they regulate the cycling of N in agroecosystems. Plants are known to harbor AOB but how they occupy the plant is an unresolved question. Methods: Metabarcoding studies were carried out using Illumina MiSeq sequencing to test the potential of seed vectored AOB exchange between plants and soil. Results and discussion: We found 27 sequences associated with AOB strains belonging to the genera Nitrosospira, Nitrosovibrio, and Nitrosomonas inhabiting Elymus nutans seeds collected from four geographically distanced alpine meadows. Nitrosospira multiformis was the most dominant across the four locations. The AOB community in E. nutans seeds was compared with that of the leaves, roots and soil in one location. Soil and seeds harbored a rich but dissimilar AOB community, and Nitrosospira sp. PJA1, Nitrosospira sp. Nsp17 and Nitrosovibrio sp. RY3C were present in all plant parts and soils. When E. nutans seeds were germinated in sterilized growth medium under greenhouse conditions, the AOB in seeds later appeared in leaves, roots and growth medium, and contributed to nitrification. Testing the AOB community of the second-generation seeds confirmed vertical transmission, but low richness was observed. Conclusion: These results suggest seed vectored AOB may play a critical role in N cycle.

The role of source emissions in sulfate formation pathways based on chemical thermodynamics and kinetics model.

Sulfate is a major PM2.5 constituent and poses a significant threat to ecosystems and human health, which has attracted lots of attention to the sulfate formation mechanism. In recent years, there has been great scientific interest in the multiphase oxidation of SO2 in aqueous aerosol particles. Many factors are involved in the reaction process, including precursor SO2, oxidants/catalysts, and aerosol acidity, which are three channels closely related to the source emission. The conjoint analysis of source emissions and sulfate aqueous formation can provide a scientific basis for designing effective strategies, though the related research is extremely limited. Here, we applied an improved solute strength-dependent chemical Thermodynamics & Kinetics model (for aqueous pathway contribution) and the Partial Target Transformation-Positive matrix factor model (for source apportionment) to explore the role of source emission in sulfate aqueous formation. The results indicated H2O2 aqueous oxidation was the dominant pathway (65.9 %), and secondary nitrate source may grow together with sulfate formation from H2O2 pathway. H2O2 and TMI pathways were related to higher SOR (sulfur oxidation rate). TMI pathway was significant in summer (54.6 %) and increased with secondary sources and vehicle exhaust. NO2 pathway was more significant at low secondary source and high coal combustion (higher contribution of NO2 pathway appeared in winter, 24.7 %). While high formation rate of the O3 pathway always occurred at low source levels. Coal combustion and vehicle exhaust showed obvious effects on sulfate aqueous formation. Notably, aerosol acidity is a significant factor related to sources and plays a key role in sulfate formation. The result also suggested aerosol pH may be more important than the amounts of substances involved in the oxidation reaction. The findings in this work can provide useful information for better understanding sulfate aqueous formation and offer a scientific basis for designing strategies for air pollution control and sulfate mitigation.

Impact of sand and dust storms on the atmospheric environment and its source in Tianjin-China.

Sand and dust storms (SDS) frequently hit northern China and adversely impact both environment and health. The carbonaceous components, inorganic elements, water-soluble ions, and meteorological parameters of several severe SDS episodes have been measured in a supersite in Tianjin, which is a big and representative city located in SDS transmission pathway in northern China. Six SDS episodes were identified in Spring, 2021. The maximum PM10 mass concentration was 2684 and 1664 µg/m3 in SDS1 and SDS3, respectively. North and northwest wind was dominant and significant differences were found in wind speed and RH between the SDS and non-SDS episodes. North dust from Inner Mongolia and Mongolia was determined by back trajectory analysis as the probable source region. The mass concentration of SO42-, NO3-, and NH4+ decreased in PM2.5. Increase of Na+ and K+ and low SO42-SDS/ SO42-non-SDS indicate dust source for short length SDS transmission in northern China. The ratio of elements could also be used to distinguish SDS and non-SDS episodes identify north and northwest source for the SDS episodes. Pb/Al, Zn/Al, and Si/Al could be regarded as indicators for SDS and non-SDS episodes, Ca/Al and Ca/Si can help to indicate SDS source direction. This study provides a variety of evidences for the dust source identification and reveals the characteristics of the most severe SDS episodes of the decade in Tianjin during Spring 2021.

High level of conservation and diversity among the endophytic seed bacteriome in eight alpine grassland species growing at the Qinghai Tibetan Plateau.

Seed borne microorganisms play an important role in plant biology. Concerns have recently been raised about loss of seed microbial diversity by seed treatments, crop domestication and plant breeding. Information on the seed microbiomes of native plants growing in natural ecosystems is beneficial as they provide the best settings to detect indigenous plant microbe interactions. Here, we characterized the seed bacterial community of 8 native alpine grassland plants. First, seed bacterial diversity was examined using Illumina DNA sequencing, then 28 cultivable bacteria were isolated and potential functions were explored. Across 8 plant species, 343 different bacterial genera were identified as seed endophytes, 31 of those were found in all plant species, indicating a high level of conservation. Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes and Chloroflexi were the top five dominant phyla. Plant species identity was a key determinant shaping the seed endophytic bacteriome. ACC deaminase activity, siderophores production and secretion of lytic enzymes were common functions shown by isolated bacteria. Our results demonstrate that highly diverse and beneficial bacterial populations are hosted by seeds of alpine grassland species to ensure the establishment of best bacterial symbionts for the next generation. This information is useful for crop improvement by reinstating beneficial seed microbial diversities for high-quality forage and crop seeds.

Quantitative Evaluation of Aerosol Generation from Non-contact Tonometry and its Correlation with Tear Film Characteristics.

INTRODUCTION: Ophthalmologists are inevitably exposed to tears and ocular discharge during ophthalmologic examinations and are at high risk for SARS-CoV-2 infection. To understand the role of aerosols in disease transmission, we adopted a prospective cross-sectional study design and investigated the count and size distribution of aerosols generated by a non-contact tonometer and its correlation with individual tear film characteristics. METHODS: This study constituted two parts. The study population included outpatients who underwent an intraocular pressure examination in an intraocular pressure examination room (Part I) and 20 participants who underwent an intraocular pressure examination in a laboratory (Part II). The following main outcomes were measured: aerosol counts at 0, 50, 100, 150, and 200 cm from the non-contact tonometer (Part I); aerosol counts after each participant underwent non-contact tonometry, and lipid layer thickness score and tear film break-up time (Part II). RESULTS: The aerosol count decreased with increasing distance from the tonometer. The aerosol count at 0 cm had the highest value compared to that at other distances. For aerosols of diameters 0.25-0.5 µm and 0.5-1.0 µm, the count decreased at 50 cm and remained stable at further distances. For aerosols of diameters 1.0-2.5 µm and ≥ 2.5 µm, the count dropped progressively at all five distances. The aerosol count from each tonometer correlated positively with the lipid layer thickness score (r = 0.490, P = 0.028), whereas the aerosol count correlated negatively with the tear film break-up time (r = - 0.675, P = 0.001). CONCLUSIONS: Aerosols tended to coagulate during diffusion. A 50-cm distance from the tonometer could confer safety from aerosols with < 1.0-µm diameter. Aerosols generated during non-contact tonometry could contain a lipid layer component. Moreover, tear film stability could affect aerosol generation. Protective eyewear is recommended for reducing infection risk from aerosols. Individual tear film characteristics should be considered during non-contact tonometry.

[Characteristics of Ozone and Source Apportionment of the Precursor VOCs in Tianjin Suburbs in Summer].

From June to August 2018, a 1-hr resolution concentration dataset of ozone and its gaseous precursors (volatile organic compounds(VOCs) and NOx), and meteorological parameters were synchronously monitored by online instruments of the Nankai University Air Quality Research Supersite. The relationships and variation characteristics between ozone and its precursors were analyzed. According to the photochemical age, the initial concentrations of VOCs were calculated, and the photochemical loss of the concentration of VOCs during the daytime (06:00-24:00) was corrected. The initial and directly monitored concentrations of VOCs were incorporated into the PMF model for source apportionment. The results indicated that the mean concentration of O3 in Tianjin in summer was (41.3±25.7)×10-9, while that of VOCs was (13.9±12.3)×10-9. The average concentration of alkane (7.0±6.8)×10-9 was clearly higher than that of other VOC species. The species with high concentrations of alkanes were propane and ethane, accounting for 47% of the total alkane concentration. The average ozone formation potential (OFP) in summer was 52.1×10-9, and the OFP value of alkene was the highest and its contribution reached 57%. During the daytime, alkene loss accounted for 75% of the total VOC loss. The major sources of VOCs that were calculated based on the initial concentration data were the chemical industry and solvent usage (25%), automobile exhaust (22%), combustion source (19%), LPG/NG (19%), and gasoline volatilization (15%), respectively. Compared with the apportionment results based on directly monitored concentrations, the contribution of the chemical industry and solvent usage decreased by 4%, while automobile exhaust decreased by 5%. By combining the results of PMF apportionment and the OFP model to analyze the relative contributions of emission sources to ozone formation, and we found that the highest contribution source of ozone was the chemical industry and solvent usage (26%) in summer. Compared with the analysis results based on the directly monitored concentrations, the OFP values of the chemical industry and solvent usage decreased by 7%, while that of NG/LPG apparently decreased by 13%.

[Responses of soil extracellular enzyme activities to the anthropogenic transition from desert grassland to shrubland in eastern Ningxia, China]. / å®å¤ä¸œéƒ¨è’æ¼ è‰åŽŸå‘çŒä¸›åœ°äººä¸ºè½¬å˜è¿‡ç¨‹ä¸­åœŸå£¤èƒžå¤–é ¶æ´»æ€§å“åº”.

To understand the responses of soil extracellular enzyme activities to the desert grassland-shrubland anthropogenic transition, we examined soil properties and six extracellular enzyme activities, in soil under vegetation patches and bare interspaces in desert grassland, grassland edge, shrubland edge, shrubland in a typical anthropogenic desert grassland-shrubland mosaic in desert steppe of eastern Ningxia, China. The six measured enzymes included cellobiohydrolase, ß-1,4-xylosidase, ß-1,4-glucosidase, ß-1,4-N-acetylglucosaminidase, leucine aminopeptidase and alkaline phosphatase. We found that soil moisture, soil organic carbon, total nitrogen, total phosphorus, microbial biomass carbon and microbial biomass nitrogen decreased significantly by 26.0%-88.5% with the process of the desert grassland-shrubland anthropogenic transition. All soil properties, except soil organic carbon and soil moisture in grassland edge site, were 3.9%-82.3% higher under vegetation patches than those in bare interspaces in each site. The six extracellular enzyme activities also decreased by 22.1%-82.4% in the transition process, especially for leucine aminopeptidase and alkaline phosphatase, showing significant decrease by 82.4% and 75.5%, respectively. All extracellular enzyme activities but ß-1,4-N-acetylglucosaminidase in shrubland were significantly higher by 10.7%-42.7% under vegetation patches than those in bare interspaces in each site. The activities of six extracellular enzymes were all positively correlated with each other. All of them were positively correlated with soil properties. Moreover, activities of these soil extracellular enzymes responded more positively to the changes of microbial biomass carbon, microbial biomass nitrogen, and total nitrogen in the process of anthropogenic transition.