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.

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.

[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.

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.

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.

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.

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.

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.

Enhanced reductive defluorination and inhibited infiltration of fluoroglucocorticoids in a river receiving reclaimed water amended by nano zero-valent iron-modified biochar: Performance and mechanisms.

The main aim of this study was to investigate the effect of a nano zero-valent iron-modified biochar-amended composite riverbed (nZVI@BC-R) on inhibited infiltration and enhanced biodegradation of fluoroglucocorticoids (FGCs) in a river receiving reclaimed water. The results demonstrated that the removal efficiency of triamcinolone acetonide (TA), a representative FGC, increased from 38.40% and 77.91% to 91.60% in the nZVI@BC-R compared with that of a natural soil riverbed (S-R) and biochar-amended soil riverbed (BC-R). The main removal mechanismwas attributedto adsorption and biodegradation, of which the contribution rates were 32.2% and 59.4% in nZVI@BC-R, 18.9% and 19.5% in S-R, and 24.4% and 53.5% in BC-R, respectively. The removal process could be described by a two-compartment, first-order dynamic model with decay rate constants for adsorption and biodegradation of 4.02700, 22.44400, and 29.07300 d-1 and 0.00286, 0.01562, and 0.03484 d-1 in the S-R, BC-R and nZVI@BC-R, respectively. The mechanism of defluorination accounted for 42.2% of biodegradation in the nZVI@BC-R, which was accompanied by side-chain rupture, oxidation, and ringopening. Functional microbes with iron oxidizing ability and reductive dehalogenating genera, namely Pseudoxanthomonas, Pedobacter, and Bosea, contributed to the high removal rate of TA, particularly in the nZVI@BC-R. Overall, the nZVI@BC-R provided an effective method to inhibit glucocorticoids infiltration into groundwater.

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.

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.

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.

Influence of rainfall duration and intensity on particulate matter removal from plant leaves.

Rainfall influences removal of airborne particulate matter (PM) from leaf surfaces through a process called wash off resulting in throughfall that carries PM to the ground. The present study examined the effects of rainfall characteristics on PM wash-off mass and rate from the foliage of four broadleaf species, to investigate retention of PM pollution. In a controlled rainfall simulation experiment, rainfall intensity was set to 15, 30, and 50mmh-1, and sampling intervals for the three rainfall intensities were divided into 10, 5, and 3min, respectively. Of the plants examined, the evergreen shrub Euonymus japonicus had the greatest surface PM accumulation before rainfall (165µgcm-2), maximum wash-off during the first 2.5mm of rain (30µgcm-2), and maximum surface PM retention after rainfall (24µgcm-2). Fitting observations with the Box Lucas regression model, cumulative PM wash-off rates increased with cumulative rainfall amount, until the curves tended to become steady after rain exceeded 12.5mm. Wash off removed 51 to 70% of surface PM accumulation. As rainfall intensity increased, the duration of PM wash-off decreased, and wash-off rates were highest during the first rainfall interval. However, there was no significant difference between PM wash-off rates for rainfall intensities of 30 and 50mmh-1 in each rainfall interval. In addition, rain did not remove all PM completely, and PM retention following rainfall differed with rainfall intensity, except for Populus tomentosa.

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).

Analysis of organic and elemental carbon in heating and non-heating periods in four locations of Beijing.

The concentrations of elemental carbon (EC) and organic carbon (OC) in PM2.5 atmospheric aerosol were measured at four different sites in Beijing: Beijing Olympic Forest Park (OF), Jiufeng National Forest Park (JF), Beijing Forestry University campus lawn (G), and roads near the Beijing Forestry University (S). The winter heating period concentrations were 30-45% higher than the spring non-heating period. Possible reasons for this could be the severe convective weather in spring due to the temperate monsoon, deposition of PM2.5 to plants in spring, stable atmospheric conditions in winter, and/or a greater number of sources of carbonaceous aerosols in winter. The proportion of total carbon (i.e. EC + OC) in PM2.5 in Beijing is high. The OC/EC value was 2.45 (OF) and 2.39 (JF) in winter and 1.6 (OF) and 1.43 (JF) in spring. These ratios and the high correlation of OC with EC in the winter samples indicate a strong primary source of OC. Eight carbon fractions from the four different sampling locations were analysed, and the OC1-4 values were found to vary considerably. In winter, the OC1 values from all four sites were higher than the spring values. Although there were differences at each site, the percentages of OC2, OC3, EC1-OP, and EC2 were the largest. Secondary organic carbon (SOC) formed during long-range transport from the emission sources to the monitoring sites, and the increase of OC2 and OC3 concentrations could be associated with SOC.

Assessing the Capacity of Plant Species to Accumulate Particulate Matter in Beijing, China.

Air pollution causes serious problems in spring in northern China; therefore, studying the ability of different plants to accumulate particulate matter (PM) at the beginning of the growing season may benefit urban planners in their attempts to control air pollution. This study evaluated deposits of PM on the leaves and in the wax layer of 35 species (11 shrubs, 24 trees) in Beijing, China. Differences in the accumulation of PM were observed between species. Cephalotaxus sinensis, Euonymus japonicus, Broussonetia papyriferar, Koelreuteria paniculata and Quercus variabilis were all efficient in capturing small particles. The plants exhibiting high amounts of total PM accumulation (on leaf surfaces and/or in the wax layer), also showed comparatively high levels of PM accumulation across all particle sizes. A comparison of shrubs and trees did not reveal obvious differences in their ability to accumulate particles based on growth form; a combination of plantings with different growth forms can efficiently reduce airborne PM concentrations near the ground. To test the relationships between leaf traits and PM accumulation, leaf samples of selected species were observed using a scanning electron microscope. Growth forms with greater amounts of pubescence and increased roughness supported PM accumulation; the adaxial leaf surfaces collected more particles than the abaxial surfaces. The results of this study may inform the selection of species for urban green areas where the goal is to capture air pollutants and mitigate the adverse effects of air pollution on human health.