Prediction of carbon emissions peak and carbon neutrality based on life cycle CO2 emissions in megacity building sector: Dynamic scenario simulations of Beijing.

In order to design an optimal carbon peak and carbon neutralization pathway for the high-density building sector, a dynamic prediction model is established using system-dynamics coupled building life cycle carbon emission model (SD-BLCA) with consideration of future evolutionary trajectory and time constraints. The model is applied in Beijing using the SD-BLCA combined with scenario analysis and Monte Carlo methods to explore optimal trajectory for its building sector under 30-year timeframe. The results indicate that by increasing the proportion of renewable energy generation by 7% and retrofitting 60 million m2 of existing buildings, these two mature measures can offset the growth of carbon emissions and achieve the peak target by 2025. However, achieving carbon neutrality necessitates a shift from isolated technologies to a comprehensive net-zero emissions strategy. The study proposes a time roadmap that integrates a zero-carbon energy supply system and the carbon reduction measures of the whole life cycle. This strategy primarily relies on renewable sources to provide heat, power, and hydrogen, resulting in estimated reductions of 29.8 Mt, 28.1 Mt, and 0.7 Mt, respectively. Zero energy buildings, green buildings, and renovated buildings can reduce carbon emissions through their own energy-saving measures by 8.4, 18.2, and 11.8 kg/m2, respectively.

Reviews of emission of biogenic volatile organic compounds (BVOCs) in Asia.

Biogenic volatile organic compounds (BVOCs) in the atmosphere play important roles in the formation of ground-level ozone and secondary organic aerosol (SOA) in global scale and also in regional scale under some condition due to their large amount and relatively higher reactivity. In places with high plant cover in the tropics and in China where air pollution is serious, the effect of BVOCs on ozone and secondary organic aerosols is strong. The present research aims to provide a comprehensive review about the emission rate, emission inventory, research methods, the influencing factors of BVOCs emissions, as well as their impacts on atmospheric environment quality and human health in recent years in Asia based on the summary and analysis of literatures. It is suggested to use field direct measurement method to obtain the emission rate and model method to calculate the emission amount. Several recommendations are given for future investigation and policy development on BVOCs emission.

Emission patterns of biogenic volatile organic compounds from dominant forest species in Beijing, China.

Biogenic volatile organic compounds (BVOCs) have significant effects on atmospheric chemistry, ozone formation and secondary organic aerosol formation. Considering few investigations about BOVCs emissions in north China where is facing serious air pollution in recent years, emissions of various BVOCs from 24 dominant forest species in Beijing were measured from June to September in 2018, using a dynamic headspace sampling method. More than one hundred BVOCs in the collected samples were identified by using an automatic thermal desorption-gas chromatography/mass spectrometry, and their emission rates based on leaf biomass were calculated. Isoprene and monoterpenes were verified to be the dominant BVOCs emitted from the tree species, accounting for more than 50% of the total BVOCs. Generally, broad-leaved species displayed high isoprene emission rates, especially the Platanus occidentalis (21.36 µg/(g⋅hr)), Robinia pseudoacacia (11.55 µg/(g⋅hr)), and Lonicera maackii (9.17 µg/(g⋅hr)), while coniferous species emitted high rates of monoterpenes, such as Platycladus orientalis (27.18 µg/(g⋅hr)), Pinus griffithii (23.11 µg/(g⋅hr)), and Pinus armandii (7.42 µg/(g⋅hr)). High emission rates of monoterpenes from the broad-leaved species of Buxus megistophylla (13.07 µg/(g⋅hr)) and Ligustrum vicaryi (5.74 µg/(g⋅hr)), and high isoprene emission rate from the coniferous tree of Taxus cuspidata (5.86 µg/(g⋅hr)) were also observed. The emission rates of sesquiterpenes from each tree were usually 10-100 times smaller than those of isoprene and monoterpenes. Additionally, relatively high emission rates of oxygenated volatile organic compounds and other alkenes than isoprene and monoterpenes were also found for several tree species.

Characteristics and influence factors of NO2 exchange flux between the atmosphere and P. nigra.

Nitrogen dioxide (NO2) is an important substance in atmospheric photochemical processes and can also be absorbed by plants. NO2 fluxes between the atmosphere and P. nigra seedlings were investigated by a double dynamic chambers method in Beijing from June 15 to September 3, 2017. The range of NO2 exchange fluxes between P. nigra seedlings and the atmosphere was from -14.6 to 0.8 nmol/(m2·sec) (the positive data represent NO2 emission from trees, while the negative values indicate absorption). Under ambient concentrations, the mean NO2 flux during the fast-growing stage (Jun. 15-Aug. 4) was -3.0 nmol/(m2·sec), greater than the flux of -1.5 nmol/(m2·sec) during the later growth stage (Aug. 8-Sept. 3). The daily exchange fluxes of NO2 obviously fluctuated. The fluxes were largest in the morning and decreased gradually over time. Additionally, the NO2 fluxes were larger under high light intensities than under low light intensities during the whole growth period. The effects of temperature on NO2 fluxes were different under two growth periods. The NO2 exchange fluxes were larger in a range of temperatures close to 44°C in the fast-growing stage, whereas there were no evident differences in NO2 exchange fluxes under widely differing temperatures in the later growth stage. Under polluted conditions, the uptake ability of NO2 was weakened. Additionally, the compensation point of NO2 was 5.6 ppb in the fast-growing stage, whereas it was 1.4 ppb in the later growth stage. The deposition velocities of NO2 were between 0.3 and 2.4 mm/sec.

Activity maintenance of the excised branches and a case study of NO2 exchange between the atmosphere and P. nigra branches.

The efficient maintenance of the activity of excised branches is the powerful guarantee to accurately determine gas exchange flux between the detached branches of tall trees and the atmosphere. In this study, the net photosynthetic rate (NPR) of the excised branches and branches in situ were measured simultaneously by using two photosynthetic instruments to characterize the activity of the excised branches of Phyllostachys nigra. The ratio of normalized NPR of excised branches to NPR in situ was used to assess the photosynthetic activity of detached branches. Based on photosynthetic activity, an optimal hydroponics protocol for maintaining activity of excised P. nigra branches was presented: 1/8 times the concentration of Gamborg B5 vitamin mixture with pH = 6. Under the best cultivation protocol, photosynthetic activity of excised P. nigra branches could be maintained more than 90% within 6 hr in the light intensity range of 200-2000 µmol/(m2·sec) and temperature range of 13.4-28.7°C. The nitrogen dioxide (NO2) flux differences between in situ and in vitro branches and the atmosphere were compared using double dynamic chambers. Based on the maintenance method of excised branches, the NO2 exchange flux between the excised P. nigra branches and the atmosphere (from -1.01 to -2.72 nmol/(m2·sec) was basically consistent with between the branches in situ and the atmosphere (from -1.12 to -3.16 nmol/(m2 sec)) within 6 hr. Therefore, this study provided a feasible protocol for in vitro measurement of gas exchange between tall trees and the atmosphere for a period of time.

17α-Ethynylestradiol biodegradation in different river-based groundwater recharge modes with reclaimed water and degradation-associated community structure of bacteria and archaea.

This study investigated 17α-ethynylestradiol (EE2) biodegradation process and primary metabolic pathways associated with community structures of microorganism during groundwater recharge using reclaimed water. The attenuation rate is 1.58 times higher in wetting and drying alternative recharge (WDAR) than in continual recharge (CR). The primary biotransformation pathways of EE2 in WDAR system began with the oxidation of C-17 on ring D to form a ketone group, and D-ring was subsequently hydroxylated and cleaved. In the CR system, the metabolic pathway changed from the oxidation of C-17 on ring D to hydroxylation of C-4 on ring A, and ring A or B subsequently cleaved; this transition was related to DO, and the microbial community structure. Four hundred fifty four pyrosequencing of 16s rRNA genes indicated that the bacterial communities in the upper layer of the WDAR system were more diverse than those found in the bottom layer of the CR system; this result was reversed for archaea. Unweighted UniFrac and taxonomic analyses were conducted to relate the change in bacterial community structure to the metabolic pathway. Microorganism community diversity and structure were related to the concentrations of dissolved oxygen, EE2 and its intermediates in the system. Five known bacterial classes and one known archaeal class, five major bacterial genera and one major archaeal genus might be involved in EE2 degradation. The findings of this study provide an understanding of EE2 biodegradation in groundwater recharge areas under different recharging modes and can facilitate the prediction of the fate of EE2 in underground aquifers.

Atmospheric isoprene and monoterpenes in a typical urban area of Beijing: Pollution characterization, chemical reactivity and source identification.

Continuous observation of isoprene, α-pinene and ß-pinene was carried out in a typical urban area of Beijing from March 2014 to February 2015, using an AirmoVOC online analyzer. Based on the analysis of the ambient level and variation characteristics of isoprene, α-pinene and ß-pinene, the chemical reactivity was studied, and their sources were identified. Results showed that the concentrations of isoprene, α-pinene and ß-pinene in the urban area of Beijing were lower than those in richly vegetated areas; the concentrations of isoprene were at a moderate level compared with those of previous studies of Beijing. Concentrations of isoprene, α-pinene and ß-pinene showed different seasonal, monthly, daily and diurnal variations, and all of the three species showed higher level at night than those in the daytime as a whole, the variations of isoprene, α-pinene and ß-pinene mainly influenced by emission of sources, photochemical reaction, and meteorological parameters. Isoprene was the largest contributor to the total OFP values than α-pinene and ß-pinene. α-Pinene was the largest contributor to the total SOAFP values than isoprene and ß-pinene in autumn, while isoprene was the largest one in other seasons. Isoprene, α-pinene and ß-pinene were derived mainly from biological sources; and α-pinene level were also affected by industrial sources. To reduce the concentrations of isoprene, α-pinene and ß-pinene, it is necessary to scientifically select urban green plant species, and more strict control measures should be taken to reduce the emission of α-pinene from industrial sources, such as artificial flavors and resins synthesis processes.

Heterogeneous Interaction of Isopropanol with Natural Gobi Dust.

The adsorption of isopropanol on Gobi dust was investigated in the temperature (T) and relative humidity (RH) ranges of 273-348 K and <0.01-70%, respectively, using zero air as bath gas. The kinetic measurements were performed using a novel experimental setup combining Fourier-Transform InfraRed spectroscopy (FTIR) and selected-ion flow-tube mass spectrometry (SIFT-MS) for gas-phase monitoring. The initial uptake coefficient, γ0, of isopropanol was measured as a function of several parameters (concentration, temperature, relative humidity, dust mass). γ0 was found independent of temperature while it was inversely dependent on relative humidity according to the empirical expression: γ0 = 5.37 × 10-7/(0.77+RH0.6). Furthermore, the adsorption isotherms of isopropanol were determined and the results were simulated with the Langmuir adsorption model to obtain the partitioning constant, KLin, as a function of temperature and relative humidity according to the expressions: KLin = (1.1 ± 0.3) × 10-2 exp [(1764 ± 132)/T] and KLin = 15.75/(3.21+RH1.77). Beside the kinetics, a detailed product study was conducted under UV irradiation conditions (350-420 nm) in a photochemical reactor. Acetone, formaldehyde, acetic acid, acetaldehyde, carbon dioxide, and water were identified as gas-phase products. Besides, the surface products were extracted and analyzed employing HPLC; Hydroxyacetone, formaldehyde, acetaldehyde, acetone, and methylglyoxal were identified as surface products while the formation of several other compounds were observed but were not identified. Moreover, the photoactivation of the surface was verified employing diffuse reflectance infrared fourier transform spectroscopy (DRIFTs).

Reversibility of the structure and dewaterability of anaerobic digested sludge.

The reversibility of the structure and dewaterability of broken anaerobic digested sludge (ADS) is important to ensure the efficiency of sludge treatment or management processes. This study investigated the effect of continuous strong shear (CSS) and multipulse shear (MPS) on the zeta potential, size (median size, d50), mass fractal dimension (D(F)), and capillary suction time (CST) of ADS aggregates. Moreover, the self-regrowth (SR) of broken ADS aggregates during slow mixing was also analyzed. The results show that raw ADS with d50 of 56.5 µm was insensitive to CSS-SR or MPS-SR, though the size slightly decreased after the breakage phase. For conditioned ADS with d50 larger than 600 µm, the breakage in small-scale surface erosion changed to large-scale fragmentation as the CSS strength increased. In most cases, after CSS or MPS, the broken ADS had a relatively more compact structure than before and d50 is at least 200 µm. The CST of the broken fragments from optimally dosed ADS increased, whereas that corresponding to overdosed ADS decreased. MPS treatment resulted in larger and more compact broken ADS fragments with a lower CST value than CSS. During the subsequent slow mixing, the broken ADS aggregates did not recover their charge, size, and dewaterability to the initial values before breakage. In addition, less than 15% self-regrowth in terms of percentage of the regrowth factor was observed in broken ADS after CSS at average velocity gradient no less than 1905.6 sec(-1).

Adsorption and biodegradation of three selected endocrine disrupting chemicals in river-based artificial groundwater recharge with reclaimed municipal wastewater.

Endocrine disrupting chemical (EDC) pollution in river-based artificial groundwater recharge using reclaimed municipal wastewater poses a potential threat to groundwater-based drinking water supplies in Beijing, China. Lab-scale leaching column experiments simulating recharge were conducted to study the adsorption, biodegradation, and transport characteristics of three selected EDCs: 17ß-estradiol (E2), 17α-ethinylestradiol (EE2) and bisphenol A (BPA). The three recharge columns were operated under the conditions of continual sterilization recharge (CSR), continual recharge (CR), and wetting and drying alternative recharge (WDAR). The results showed that the attenuation effect of the EDCs was in the order of WDAR>CR>CSR system and E2>EE2>BPA, which followed first-order kinetics. The EDC attenuation rate constants were 0.0783, 0.0505, and 0.0479 m(-1) for E2, EE2 and BPA in the CR system, respectively. The removal rates of E2, EE2, and BPA in the CR system were 98%, 96% and 92%, which mainly depended on biodegradation and were affected by water temperature. In the CR system, the concentrations of BPA, EE2, and E2 in soil were 4, 6 and 10 times higher than in the WDAR system, respectively. According to the DGGE fingerprints, the bacterial community in the bottom layer was more diverse than in the upper layer, which was related to the EDC concentrations in the water-soil system. The dominant group was found to be proteobacteria, including Betaproteobacteria and Alphaproteobacteria, suggesting that these microbes might play an important role in EDC degradation.

CH4 emission and conversion from A2O and SBR processes in full-scale wastewater treatment plants.

Wastewater treatment systems are important anthropogenic sources of CH4 emission. A full-scale experiment was carried out to monitor the CH4 emission from anoxic/anaerobic/oxic process (A20) and sequencing batch reactor (SBR) wastewater treatment plants (WWTPs) for one year from May 2011 to April 2012. The main emission unit of the A2O process was an oxic tank, accounting for 76.2% of CH4 emissions; the main emission unit of the SBR process was the feeding and aeration phase, accounting for 99.5% of CH4 emissions. CH4 can be produced in the anaerobic condition, such as in the primary settling tank and anaerobic tank of the A2O process. While CH4 can be consumed in anoxic denitrification or the aeration condition, such as in the anoxic tank and oxic tank of the A2O process and the feeding and aeration phase of the SBR process. The CH4 emission flux and the dissolved CH4 concentration rapidly decreased in the oxic tank of the A2O process. These metrics increased during the first half of the phase and then decreased during the latter half of the phase in the feeding and aeration phase of the SBR process. The CH4 oxidation rate ranged from 32.47% to 89.52% (mean: 67.96%) in the A2O process and from 12.65% to 88.31% (mean: 47.62%) in the SBR process. The mean CH4 emission factors were 0.182 g/ton of wastewater and 24.75 g CH4/(person x year) for the A2O process, and 0.457 g/ton of wastewater and 36.55 g CH4/(person x year) for the SBR process.

Estimation of PM10 in the traffic-related atmosphere for three road types in Beijing and Guangzhou, China.

The levels of roadside PM10 in Beijing, China, were investigated in 2011 and 2012 on a seasonal basis to estimate the population exposure to particulates for three road types. The measurements of PM10 were also conducted in the southern Chinese megacity of Guangzhou for comparison purposes. The results showed that roadside PM10 in Beijing correlated strongly with the PM10 background in the urban atmosphere. The levels of PM10 in street canyons were markedly higher than those along the open roads and in crossroad areas because of limited ventilation. An elevation of PM10 was observed in April, which was possibly due to the sand storms that frequently occur in the spring. Based on these observations, roadside PM10 in Beijing could have multiple origins and was to some extent dispersion-governed. In Guangzhou, the roadside PM10 did not closely relate to the background values. The PM10 pollution was greatly affected by local traffic conditions. The simulation of PM10 for different road types was completed during the study period using the Motor Vehicle Emissions Factor Model (MOBILE6.2) as an emission model and the California Line Source Dispersion Model (CALINE4) and Operational Street Pollution Model (OSPM) as dispersion models. The MOBILE6.2/CALINE4 software package was demonstrated to be sufficient for the simulation of PM10 in the open roads and crossroad areas in both Beijing and Guangzhou, and the simulation results of roadside PM10 in the street canyons by the MOBILE6.2/OSPM package were in close agreement with those of the measurements.

Design and preparation of reticular superabsorbent hydrogel material with nutrient slow-release and high shear strength for ecological remediation of abandoned mines with steep slopes.

In order to solve ecological remediation issues for abandoned mines with steep slopes, a kind of hydrogels with high cohesion and water-retaining were designed by inorganic mineral skeleton combining with polymeric organic network cavities. This eco-friendly hydrogel (MFA/HA-g-p(AA-co-AM)) was prepared with acrylic acid (AA)-acrylamide (AM) as network, which was grafted with humic acids (HA) as network binding point reinforcement skeleton and polar functional group donors, KOH-modified fly ash (MFA) as internal supporter. The maximum water absorption capacities were 1960 g/g for distilled water, which followed the pseudo-second-order model. This super water absorption was attributed to the first stage of 62 % fast absorption due to the high specific surface area, pore volume and low osmotic pressure, moreover, the multiple hydrophilic functional groups and network structure swell contributed to 36 % of the second stage slow adsorption. In addition, the pore filling of water in mesoporous channels contributed the additional 2 % water retention on the third stage. The high saline-alkali resistance correlated with the electrostatic attraction with MFA and multiple interactions with oxygen-containing functional groups in organic components. MFA and HA also enhanced the shear strength and fertility retention properties. After 5 cycles of natural dehydration and reabsorption process, these excellent characteristics of reusability and water absorption capacity kept above 97 %. The application of 0.6 wt% MFA/HA-g-p(AA-co-AM) at 15° slope could improve the growth of ryegrass by approximately 45 %. This study provides an efficient and economic superabsorbent material for ecological restoration of abandoned mines with steep slopes.

Biogenic volatile organic compounds in forest therapy base: A source of air pollutants or a healthcare function?

Air pollution poses a significant threat to public health, while biogenic volatile organic compounds (BVOCs) play a crucial role in both aspects. However, the unclear relationship between BVOCs and air pollutants in the under-canopy space limits the accuracy of air pollution control and the exploitation of forest healthcare functions. To clarify the variation of BVOCs in forest therapy bases, and their impacts on ozone (O3) and fine particulate matter (PM2.5) at nose height, total VOCs (TVOCs) in the forest were collected during typical sunny days, while air pollutants and meteorological factors were observed simultaneously. The results showed that the branch-level emissions of P. tabuliformis were dominated by healthcare-effective monoterpenoids, with only α-pinene having relative air concentrations of over 5 % in forest air samples. The correlation between concentrations of under-canopy TVOCs and emission rates of BVOCs from P. tabuliformis was weak (p > 0.09) in all seasons. However, the correlation between concentrations of TVOCs and the concentrations of O3 and PM2.5 showed clear seasonal differences. In spring, TVOCs only showed a significant negative correlation with PM2.5 in the forest (p < 0.01). In summer and autumn, TVOCs were significantly negatively correlated with both O3 (p < 0.001) and PM2.5 (p < 0.01). Specifically, the negative linear relationships were more pronounced for O3 and oxygenated VOCs in autumn (R2 = 0.40, p < 0.001) than for other relationships. The relationship between air pollutant concentrations inside and outside the forest also showed significant seasonal differences, generally characterized by a weaker correlation between them during seasons of strong emissions. Therefore, BVOCs in coniferous forests are health functions as they can provide healthcare effects and mitigate the concentration of air pollutants in the forest, and the establishment of forest therapy bases in rural areas with low NOx can be a sensible approach to promote good health, well-being, and sustainable development.

Assessment of surface ozone production in Qinghai, China with satellite-constrained VOCs and NOx emissions.

The implementation of the western development strategy of China and the migration of air pollutants from eastern China might lead to a rapid increase in volatile organic compounds (VOCs) concentrations in the Qinghai-Tibet Plateau (QTP) and an amplified role of Nitrogen Oxides (NOx) in ozone (O3) pollution. Qinghai province, situated on the northeast of the QTP, had fewer human activities compared to eastern China, while ozone pollution worsened over the years. To better capture recent emission trends and improve the accuracy of O3 simulation in Qinghai, this study proposed a top-down method, which combined the air quality modeling system RAMS-CMAQ, with formaldehyde (HCHO) and nitrogen dioxide (NO2) columns derived from TROPOMI as the constraints to improve the emission estimates of VOCs and NOx in July 2020, respectively. Through a series of sensitivity experiments, better quantified emission estimates of VOCs and NOx were obtained to be 1.33 and 0.34 Tg/yr, 2.5 and 2.1 times larger than the bottom-up ones. The results demonstrated the effectiveness of the top-down method and satellite observations constraints in improving VOCs and NOx emission estimates, resulting in a reduction in the differences between the observed and modeled HCHO and NO2 columns to 0.7 and 0.2 × 1015 molec/cm2, respectively. As a result, the simulated maximum daily 8-h average (MDA8) O3 concentrations increased from 58.9 to 81.6 µg/m3, which were closer to observations (85.4 µg/m3), the normalized mean bias (NMB) and normalized mean error (NME) values of hourly O3 concentrations changed from -24.7 % to -2.9 % and from 29.9 % to 22.3 %, respectively. This study showed the potential of top-down estimates to aide in the development of emission scenarios, which were critical for accurately simulating the O3 pollution and pollution control policy studies.

Full profile contamination process simulation and risk prediction of synthetic musk from reclaimed water receiving river to groundwater via vadose zone: A case study of Chaobai River.

Long-term infiltration from river receiving reclaimed water will pose potential risk to vadose zone and groundwater because of the persistent and highly toxic contaminants. In order to predict the spatio-temporal distribution of ecological and health risk, a coupled model of HYDRUS-GMS combined risk quotient was proposed. The model can accurately predict water flow, solute transport and risk with model due to the acceptable efficiency (E:0.99), mean absolute error (MAE:0.031 m) and root-mean-square error (RMSE:0.039 m). The content of galaxolide (HHCB), a typical pharmaceutical and personal care product with hydrophobicity and refractory in reclaimed water, increased in vadose zone at an accumulative rate of 6.1 ng g-1 year-1 with infiltration time extension. The accumulation will pose ecological risk after 53 years infiltration. The potential risk will extent to groundwater once penetrate through vadose zone, and mainly diffuse along groundwater flow direction. The migration rate along horizontal direction of groundwater flow is 0.03396 m d-1, which is 9.7 and 1.1 times higher than longitudinal and vertical rates due to the variation of driving force in three directions. The migration rate of HHCB was 2.6% of groundwater flow due to hydrophobicity (LogKow = 5.9). The complete biochemical decomposition of HHCB will take approximately 0.38 year through metabolite within 182.65 m distance. The persistence was attributed to the high chronic toxicity and the low bio-availability. The major biochemical metabolism of HHCB was enzymatic hydrolysis, ring opening, decarboxylation, which was decomposed and carbonized within approximately 0.38 year after 182.65 m migration distance. This study provided a new approach to predict the spatio-temporal risk distribution due to reclaimed water reuse.

Detoxification of fluoroglucocorticoid by Acinetobacter pittii C3 via a novel defluorination pathway with hydrolysis, oxidation and reduction: Performance, genomic characteristics, and mechanism.

Biological dehalogenation degradation was an important detoxification method for the ecotoxicity and teratogenic toxicity of fluorocorticosteroids (FGCs). The functional strain Acinetobacter pittii C3 can effectively biodegrade and defluorinate to 1 mg/L Triamcinolone acetonide (TA), a representative FGCs, with 86 % and 79 % removal proportion in 168 h with the biodegradation and detoxification kinetic constant of 0.031/h and 0.016/h. The dehalogenation and degradation ability of strain C3 was related to its dehalogenation genomic characteristics, which manifested in the functional gene expression of dehalogenation, degradation, and toxicity tolerance. Three detoxification mechanisms were positively correlated with defluorination pathways through hydrolysis, oxidation, and reduction, which were regulated by the expression of the haloacid dehalogenase (HAD) gene (mupP, yrfG, and gph), oxygenase gene (dmpA and catA), and reductase gene (nrdAB and TgnAB). Hydrolysis defluorination was the most critical way for TA detoxification metabolism, which could rapidly generate low-toxicity metabolites and reduce toxic bioaccumulation due to hydrolytic dehalogenase-induced defluorination. The mechanism of hydrolytic defluorination was that the active pocket of hydrolytic dehalogenase was matched well with the spatial structure of TA under the adjustment of the hydrogen bond, and thus induced molecular recognition to promote the catalytic hydrolytic degradation of various amino acid residues. This work provided an effective bioremediation method and mechanism for improving defluorination and detoxification performance.

Investigation of biogenic volatile organic compounds emissions in the Qinghai-Tibetan Plateau.

Biogenic volatile organic compounds (BVOCs), which are produced and emitted by plants, have significant chemical reactivity in the atmosphere and impacting climate change. Qinghai Province, a vital component of the plateau, has abundant vegetation resources, primarily grasslands and forests, yet BVOCs emissions and their impact on air quality remain understudied. In this study, the emissions rates and compositions of BVOCs from seven dominant vegetation types in Qinghai Province were sampled and analyzed using a closed-loop stripping dynamic headspace sampling approach combined with GC-MS, and the total emissions of BVOCs in Qinghai province in 2021 were estimated by using G95 model. At the same time, the emission characteristics of various vegetation types were also analyzed. The results showed that the emissions rates and compositions of BVOCs differed significantly among vegetation types, with monoterpenes being the dominant emission composition in coniferous forests, which accounted for >70 % of the total BVOCs emissions, while isoprene being the main composition in alpine meadow, accounting for 84.96 %. The emissions of three typical vegetation types, Picea asperata, alpine meadow and alpine steppe, were monitored daily, revealing significant diurnal and clear unimodal patterns. The study also found that the annual average BVOCs emissions from vegetation sources in Qinghai Province were estimated to be 1550.63 Gg yr-1, with isoprene contributing the highest proportion of emissions, accounting for 56.94 %. Grassland was the largest BVOCs emission source in Qinghai Province, with an annual average emission of 1438.52 Gg yr-1. Additionally, BVOCs emissions in Qinghai Province showed strong seasonal and daily variation patterns, with the highest emissions occurring in summer, with the peak in July. These findings provide the characteristics of BVOCs emissions from vegetation sources in the Tibetan Plateau, which will contribute to a better understanding of their impact on atmospheric chemistry and climate change.

[Pollution Characteristics and Source Apportionment of VOCs in Urban Areas of Liaocheng in Summer].

Based on the online monitoring data of volatile organic compounds(VOCs) and ozone(O3) in Liaocheng in June 2021, the concentration levels, compositional characteristics, daily variation characteristics, and ozone formation potential(OFP) of VOCs on polluted days and clean days were systematically analyzed. Potential source areas of VOCs were identified by the potential source contribution function(PSCF) and concentration-weighted trajectory(CWT). The sources of VOCs in Liaocheng were analyzed using the characteristic species ratio and positive matrix factorization(PMF). The results showed that the hourly mean values of VOCs concentrations on polluted days and clean days in Liaocheng in June 2021 were(115.38±59.12) µg·m-3 and(88.10±33.04) µg·m-3, respectively, and the concentration levels of VOCs in each category showed that oxygenated volatile organic compounds(OVOCs)>alkanes>halogenated hydrocarbons>aromatic hydrocarbons>alkenes>alkynes>organosulfur. VOCs species with large differences in concentrations between polluted and clean days were among the top ten species of the hourly mean VOCs concentrations. The daily trends of concentrations of total VOCs, alkanes, alkynes, aromatic hydrocarbons, halogenated hydrocarbons, and organosulfur showed that the daytime concentrations were lower than the nighttime concentrations, and the daily changes in OVOCs concentrations showed the characteristics of high in the daytime and low at nighttime. The OFP was 285.29 µg·m-3 on polluted days and 212.00 µg·m-3 on clean days, and OVOCs, alkenes, and aromatic hydrocarbons contributed significantly to ozone formation. The PSCF and CWT results found that the potential source areas of VOCs in Liaocheng were concentrated in the northern and northeastern part of Dongchangfu District and the central and southwestern part of Chiping District. The results of the characteristic species ratio indicated that the VOCs in Liaocheng might have been more from coal combustion, gasoline volatilization, and motor vehicle exhaust. The results of PMF showed that industrial emission sources(30.57%), motor vehicle exhaust and oil and gas volatilization sources(19.44%), combustion sources(17.23%), air aging and secondary generation sources(13.69%), solvent usage sources(12.75%), and natural sources(6.32%) were the main sources of VOCs in Liaocheng.

Nitrous oxide emissions from a maize field during two consecutive growing seasons in the north China plain.

Nitrous oxide (N2O) emissions from a maize field in the North China Plain (Wangdu County, Hebei Province, China) were investigated using static chambers during two consecutive maize growing seasons in the 2008 and 2009. The N2O pulse emissions occurred with duration of about 10 days after basal and additional fertilizer applications in the both years. The average N20 fluxes from the CK (control plot, without crop, fertilization and irrigation), NP (chemical N fertilizer), SN (wheat straw returning plus chemical N fertilizer), OM-1/2N (chicken manure plus half chemical N fertilizer) and OMN (chicken manure plus chemical N fertilizer) plots in 2008 were 8.51, 72.1, 76.6, 101, 107 ng N/(m2 x sec), respectively, and in 2009 were 33.7, 30.0 and 35.0 ng N/(m2 x sec) from CK, NP and SN plots, respectively. The emission factors of the applied fertilizer as N20-N (EFs) were 3.8% (2008) and 1.1% (2009) for the NP plot, 3.2% (2008) and 1.2% (2009) for the SN plot, and 2.8% and 2.2% in 2008 for the OM-1/2N and OMN plots, respectively. Hydromorphic properties of the investigated soil (with gley) are in favor of denitrification. The large differences of the soil temperature and water-filled pore space (WFPS) between the two maize seasons were suspected to be responsible for the significant yearly variations. Compared with the treatments of NP and SN, chicken manure coupled with compound fertilizer application significantly reduced fertilizer loss rate as N2O-N.