Abstract Foliar stable nitrogen (N) isotopes (δ15N) generally reflect N availability to plants and have been used to infer about changes thereof. However, previous studies of temporal trends in foliar δ15N have ignored the influence of confounding factors, leading to uncertainties on its indication to N availability. In this study, we measured foliar δ15N of 1811 herbarium specimens from 12 plant species collected in southern China forests from 1920 to 2010. We explored how changes in atmospheric CO2, N deposition and global warming have affected foliar δ15N and N concentrations ([N]) and identified whether N availability decreased in southern China. Across all species, foliar δ15N significantly decreased by 0.82‰ over the study period. However, foliar [N] did not decrease significantly, implying N homeostasis in forest trees in the region. The spatiotemporal patterns of foliar δ15N were explained by mean annual temperature (MAT), atmospheric CO2 (PCO2), atmospheric N deposition, and foliar [N]. The spatiotemporal trends of foliar [N] were explained by MAT, temperature seasonality, PCO2, and N deposition. N deposition within the rates from 5.3 to 12.6 kg N ha−1 year−1 substantially contributed to the temporal decline in foliar δ15N. The decline in foliar δ15N was not accompanied by changes in foliar [N] and therefore does not necessarily reflect a decline in N availability. This is important to understand changes in N availability, which is essential to validate and parameterize biogeochemical cycles of N.
A molecule featuring two distinct cooperatively grown J-aggregates is investigated. Interestingly, when cooling a hot monomer solution, the thermodynamically less stable J1 is exclusively formed even at a particularly slowed temperature dropping rate, which transforms to the more stable J2 at room temperature with very slow kinetics. This observation is ascribed to the differed nucleus sizes of J1 and J2 . During the cooling process, smaller J1 nuclei are formed first at a higher temperature, favored by the entropy effect. At intermediate temperatures, the elongation of J1 out-competes the nucleation of J2 . Then, below the elongation temperature of J2 , the formation of this thermodynamically stable aggregate is hindered kinetically, due to the depletion of monomer by the slow dissociation of J1 . Additional evidence proving the larger nucleus size of J2 is also identified with the varied-temperature spectral analyses and mathematic simulations.
Monitoring field-scale CO2 geological utilizations is of paramount importance but challenging due to the complexities in microscopic heterogeneity. In this paper, complex geological characterizations and fluid properties are specifically analysed and a prediction model is developed, which is capable to track the dynamic behaviour of miscible CO2 multiphase flow in microscopically-heterogeneous porous media. More specifically, first, pore-throat sizes and distributions were characterised from the constant-rate mercury injection and the CO2-displacement seepage resistance was evaluated from a capillary bundle model. The differences of seepage resistance caused from the throat changing and coupling diffusion-dissolution effects and viscosity-resistance reductions were specifically studied in the process of continuous miscible CO2 displacement. Accordingly, a comprehensive mathematical model was developed with the time-node analysis method and validated through comparison with the experimental results. The leading edge of CO2 displacement as well as the timing of gas breakthrough and displacement completion are determined to be different with varying throat sizes. It is further found that the gas breakthrough time and the time required to complete the displacement are reduced with increasing throat size and their differences also decrease. Moreover, the interval area of injection and production wells could be characterised as pure CO2, diffusion and pure oil zones, whose positions could be dynamically tracked from the recovery performance. The calculated oil recovery and gas-oil ratio from the developed model share good agreement with experimental results, with deviations of 2.2 and 0.7%. Such the validated mathematical model is then applied to successfully predict the dynamic performance of an actual reservoir (H3).
Largely limited by measurement technique, dynamics of semivolatile organic compounds (SVOCs) in the indoor air is not well understood. This study reports time-resolved measurements of airborne concentration of di-2-ethylhexyl phthalate (DEHP) in an office, using semivolatile thermal desorption aerosol gas chromatography (SV-TAG). The measurements were conducted in two separate periods during the summer-to-fall transition in 2020, each for more than 10 days. The indoor gas-plus-particle DEHP concentration varied by more than one order of magnitude in each observation period, and the temporal pattern exhibited possible influences of the indoor temperature, particle mass concentration, and outdoor DEHP concentrations. Further analysis focusing on window-closed conditions (i.e., with less outdoor contribution) reveals that the DEHP dynamics was primarily driven by variations in the indoor temperature (R2 = 0.85) during the first, warmer period (24–29 °C), and by variations in the particle mass concentration (R2 = 0.83) during the subsequent cooler period (20–23 °C). The unexpected transition of the key driving factor with change of the temperature was qualitatively justified by a simplified mechanistic model. Moreover, the particle fraction of DEHP was measured during the latter, cooler period, and it exhibited strong dependence on particle concentration, which can be fitted assuming gas-particle equilibrium partitioning, with a best-fit apparent partitioning coefficient of 0.053 ± 0.006 m3/$μ$g at 20 ± 1 °C. Overall, these results improve our understanding of real-world SVOC dynamics.
Many ecological restoration programs have been implemented in China during the last two decades. At the same time, the vegetation has turned green significantly in China. However, few studies have directly evaluated the contribution of the ecological restoration programs to vegetation greening in comparison with the contribution of climate change using high-resolution data of afforestation areas at the national scale. We used newly compiled high-resolution data on yearly forest plantation and mountain closure, the daily climate data from the 2480 meteorological stations and GIMMS 3g NDVI data. We used a multiple linear regression model to compare the influence of temperature, precipitation, and ecological restoration programs on NDVI dynamics. We then used the hierarchical variance partitioning method to evaluate the relative contribution of temperature, precipitation, and ecological restoration programs on NDVI dynamics. We found a significant greening trend in China from 1999 to 2015 with an annual increase rate of 0.0017 yr−1 in the mean growing season NDVI. The ecological restoration programs dominated the vegetation greening in northern China and the southern coastal regions, indicating a good performance of restoration programs in these regions. In contrast, temperature or precipitation dominated the vegetation greening in southwestern China, Inner Mongolia and the implementation regions of several ecological restoration programs in northeastern China. Among the ecological restoration programs except the Three-North Shelterbelt Forest Program, the effect of ecological restoration programs on vegetation greening was stronger than the total effects of temperature and precipitation changes. Our study presents a systematic assessment on the contribution of ecological restoration programs to the vegetation greening in China, accessed the role on vegetation greening of different ecosystem restoration programs. We analyzed the reasons for the differences in the contribution of different ecological restoration programs to vegetation greening and provided insights facilitating policy makers to prioritize future restoration planning.
{ A series doses (0–1.0 g/L) of titanium dioxide (TiO2) and titanate nanotubes (TNTs) were added into the sequencing batch reactor (SBR) to investigate the biological effect of titanium nanomaterials. TNTs and TiO2 showed a moderate suppressing effect on SBR performance, while TiO2 seemed to be more toxic. Further, 0.04 g/L TiO2 resulted in significant inhibition on the removal of methylene blue (p < 0.05
Carbon dioxide miscible flooding has been proven to be one of the most effective enhanced oil recovery (EOR) technologies, particularly for light and medium oil reservoirs. However, specific effects of pore structure on CO2 miscible flooding recovery in low permeability reservoir lack in-depth understandings. In this paper, pore structures are specifically studied by means of the molecular mechanics to evaluate their effects on the CO2 EOR in the low permeability reservoir. First, a series lab experiments are performed for the pore and fluid characterization. More specifically, the pore throat size and distribution frequency are measured from the high-pressure mercury injection and nuclear magnetic resonance. The minimum miscibility pressure is determined from the slim-tube tests with known oil compositions tested from gas chromatography analysis. Second, the regularity of CO2 extraction is explored on the basis of molecular mechanics and the thickness of raffinate is calculated. Finally, the raffinate volume and recovery ratio in the pores are calculated after the CO2 miscible flooding. The results show that a raffinate-layer with thickness of 0.13 μm remains on the surface of the pore after the CO2 miscible flooding, which would cause the oil to be immobile since the throat could be blocked when the throat radius is smaller than 0.26 μm. The recoveries of cores C-1 and C-2 are 70.1 % and 61.4 % from calculations and 68.4 % and 59.8 % from experiments, whose errors are 2.5 % and 2.7 %, respectively. This study would be beneficial to analyze the CO2 miscible flooding in reservoirs with different pore structures and provide technical support for improving CO2 utilization efficiency.
Fe3(PO4)2·8H2O (Vivianite) is one of the potential phosphorus recovery products from wastewater treatment plant (WWTP). In this study, we first discovered that vivianite can effectively photoactivate peroxodisulfate (PDS) to produce some reactive oxygen species (ROS) for tetracycline antibiotics (TCs) degradation. The results demonstrated that vivianite could efficiently activate PDS to achieve 100% removal of TCs under LED UV light (UVL), visible light (VL) or real solar light (SL) irradiation within 10 min, respectively. More importantly, ca. 80%, 78% and 40%∼58% of TOC removal efficiencies were achieved under UVL, VL and SL irradiation within 30 min, respectively. As well, toxicological simulation and antibacterial studies showed that the aquatic toxicity of the TCs intermediates was lower than those of the original TCs. This work provided new insights into the application of photoactivated sulfate radical-advanced oxidation process (SR-AOP) for organic pollutants degradation over vivianite, which may encourage the recovery and utilization of vivianite in the wastewater treatment process.
Drinking alcohol is cited as a way for men to cope with stress, with most of the research emanating from western countries. However, in the East, limited scientific research has been conducted on the relationship between stress and alcohol consumption. Thus, this study aimed to explore the influence of life stress on alcohol use among Chinese men.Our data were drawn from the 2012 China Family Panel Studies that comprised representative samples of the Chinese population. In total, 15,373 Chinese men participated in this study, and their weekly alcohol intake and life stress were evaluated using computer assisted personal interviews. It was found that the greater the overall life pressure experienced by the Chinese men, the less likely they were to engage in both general (OR = 0.977) and heavy drinking (OR = 0.975). Although severe life stress that interfered with daily life did not affect general drinking, it had a negative effect on heavy drinking. As for less severe life stresses, feeling down and sad had an inhibitory effect on male general and heavy drinking, and experiencing loneliness had a similar effect on general drinking but no effect on heavy drinking. Further, perceiving unfriendliness from others had no influence on male drinking behavior. Although feeling disliked by others had no effect on male drinking behavior, it had a significant, positive effect on male heavy drinking. This study found that in China, stress did not increase male alcohol consumption, but rather, inhibited it. Alcohol consumption is not a preferred strategy for Chinese men dealing with stress.
In this study, the previously overlooked effects of contaminants’ molecular structure on their degradation efficiencies and dominant reactive oxygen species (ROS) in advanced oxidation processes (AOPs) are investigated with a peroxymonosulfate (PMS) activation system selected as the typical AOP system. Averagely, degradation efficiencies of 19 contaminants are discrepant in the CoCaAl-LDO/PMS system with production of SO4•–, •OH, and 1O2. Density functional theory calculations indicated that compounds with high EHOMO, low-energy gap (ΔE = ELUMO – EHOMO), and low vertical ionization potential are more vulnerable to be attacked. Further analysis disclosed that the dominant ROS was the same one when treating similar types of contaminants, namely SO4•–, 1O2, 1O2, and •OH for the degradation of CBZ-like compounds, SAs, bisphenol, and triazine compounds, respectively. This phenomenon may be caused by the contaminants’ structures especially the commonly shared or basic parent structures which can affect their effective reaction time and second-order rate constants with ROS, thus influencing the contribution of each ROS during its degradation. Overall, the new insights gained in this study provide a basis for designing more effective AOPs to improve their practical application in wastewater treatment.
Abstract We performed a cross-sectional survey of 2143 female students in a university in Tianjin, China regarding perceived air quality (PAQ) and sick building syndrome (SBS) symptoms in the student dormitory. The prevalence of general, mucosal, and skin symptoms was 22.1%, 21.9%, and 26.3%, respectively. The three most prevalent PAQ complaints were ?dry air? (48.9% often), ?stuffy odor? (18.2%), and ?other unpleasant odors? (5.1%), and they were significant risk factors for 11?12 out of 12 SBS symptoms (adjusted odds ratios [AOR]: 1.6?5.8). Survey data of 1471 undergraduates, whose dorms were of uniform layout and furnishing, were used to further investigate the influences of occupancy level and occupant behaviors on PAQ and SBS symptoms. Frequent use of air freshener/perfume was a significant risk factor for ?dry air,? less frequent room cleaning and higher occupancy density were significant risk factors for ?stuffy odor,? and less natural ventilation was a significant risk factor for both ?stuffy odor? and ?pungent odor.? These factors were also significantly associated with some SBS symptoms. In particular, the use of air freshener/perfume exhibited a significant dose?response pattern with ?fatigue? (sometimes: AOR 1.3; often: AOR 2.0) and with ?irritated, stuffy, or runny nose? (sometimes: AOR 1.6; often: AOR 2.2).
Current research focuses on introducing additional energy or reducing agents to directly accelerate the formation of Fe(IV) and Fe(V) from ferrate (Fe(VI)), thereby ameliorating the oxidation activity of Fe(VI). Interestingly, this study discovers that colloid manganese dioxide (cMnO2) can remarkably promote Fe(VI) to remove various contaminants via a novel surface-promoted pathway. Many lines of evidence suggest that high-valent Fe species are the primary active oxidants in the cMnO2−Fe(VI) system, however, the underlying activation mechanism for the direct reduction of Fe(VI) by cMnO2 to generate Fe(IV)/Fe(V) is eliminated. Further analysis found that Fe(VI) can combine with the vacancies in cMnO2 to form precursor complex (cMnO2−Fe(VI)*), which possesses a higher oxidation potential than Fe(VI). This makes cMnO2−Fe(VI)* is more vigorous to oxidize pollutants with electron-rich moieties through the electron transfer step than alone Fe(VI), resulting in producing Fe(V) and Fe(IV). The products of Fe(VI) decay (i.e., Fe(II), Fe(III), and H2O2) are revealed to play vital roles in further boosting the formation of Fe(IV) and Fe(V). Most importantly, the catalytic stability of cMnO2 in complicated waters is superior to popular reductants, suggesting its outstanding application potential. Taken together, this work provides a full-scale insight into the surface-promoted mechanism in Fe(VI) oxidation process, thus providing an efficient and green strategy for Fe(VI) activation.