Trace metals in atmospheric particulate matter (PM) are a serious threat to public health. Although pollution from toxic metals has been investigated in many Chinese cities, the spatial and temporal patterns in PM2.5 remain largely unknown. Long-term PM2.5 field sampling in 11 cities, combined with a systemic literature survey covering 51 cities, provides the first comprehensive database of 21 PM2.5-bound trace metals in China. Our results revealed that PM2.5 elemental compositions varied greatly, with generally higher levels in North China, especially for crustal elements. Pollution with Cr, As, and Cd was most serious, with 61, 38, and 16 sites, respectively, surpassing national standards, including some in rural areas. Local emissions, particularly from metallurgical industries, were the dominant factors driving the distribution in polluted cities such as Hengyang, Yuncheng, and Baiyin, which are mainly in North and Central China. Elevated As, Cd, and Cr levels in Yunnan, Guizhou Province within Southwest China were attributed to the high metal content of local coal. Diverse temporal trends of various elements that differed among regions indicated the complexity of emission patterns across the country. The results demonstrated high non-carcinogenic risks for those exposed to trace metals, especially for children and residents of heavily cities highly polluted with As, Pb, or Mn. The estimated carcinogenic risks ranged from 6.61 × 10−6 to 1.92 × 10−4 throughout China, with As being the highest priority element for control, followed by Cr and Cd. Regional diversity in major toxic metals was also revealed, highlighting the need for regional mitigation policies to protect vulnerable populations.
Morphological variation of leaves is a key indicator of plant response to climatic change. Leaf size and shape are associated with carbon, water and energy exchange of plants with their environment. However, whether and how leaf size and shape responded to climate change over the past decades remains poorly studied. Moreover, many studies have only explored inter- but not intraspecific variation in leaf size and shape across space and time.We collected over 6000 herbarium specimens spanning 98 years (1910–2008) in China for seven representative dicot species and measured their leaf length and width. We explored geographical patterns and temporal trends in leaf size (i.e., leaf length, leaf width and length x width product) and shape (i.e., length/width ratio), and investigated the effects of changes in precipitation and temperature over time and space on the variation in leaf size and shape.After accounting for the effects of sampling time, leaf size decreased with latitude for all species combined, but the relationship varied among species. Leaf size and shape were positively correlated with temperature and precipitation across space. After accounting for the effects of sampling locations, leaf size of all species combined increased with time. Leaf size changes over time were mostly positively correlated with precipitation, whereas leaf shape changes were mostly correlated with temperature. Overall, our results indicate significant spatial and temporal intraspecific variation in leaf size and shape in response to climate. Our study also demonstrates that herbarium specimens collected over a considerable period of time provide a good resource to study the impacts of climate change on plant morphological traits.
This paper compiled a new speciated NMVOCs emission inventory for the industrial sources at the county-level by using a bottom-up approach in 2016, as well as estimated the ozone formation potential (OFP) and investigated its spatial characteristics in China. Results indicated that the total NMVOCs emissions from industrial sources estimated as 21.04 Tg in 2016. The five major source categories including “production of VOCs”, “storage and transportation”, “industrial processes using VOCs as raw material”, “processes using VOCs-containing products”, and “industrial fossil fuel combustion processes” generated 1.92 Tg, 0.94 Tg, 6.54 Tg, 10.04 Tg, and 1.60 Tg VOCs, respectively, in 2016. According to our estimates, aromatics were the largest contributor of industrial NMVOCs emissions in 2016, accounting for 36% of total NMVOCs, followed by Alkanes (29%), OVOCs (22%), Alkenes (7%), Halocarbons (4%), and Alkynes (2%). Styrene, m/p-xylene, ethylbenzene, toluene, and ethyl acetate were the top five VOC species from industrial sources in terms of abundance in 2016. Aromatics have a high potential for ozone formation, and accounted for 70% of total OFP, followed by Alkenes (14%), Alkanes (10%), and OVOCs (6%). Styrene, p-xylene, toluene, ethylbenzene, 1,3-butadiene were the five species that had the largest potential to form ozone, and plastic industry, coke industry, household appliances industry, and architectural decoration were the key contributing sectors. The emissions displayed distinct spatial characteristics, with significantly higher emissions and OFPs in coastal regions than in other inland areas of China.
The electron-transporting materials (ETMs), 2,7-bis(3,5-di (pyridin-3-yl)phenyl)-9,9'-spirobi [fluorene] (3-4PySF) and 2,7-bis(3,5-di (pyridin-4-yl)phenyl)-9,9'-spirobi [fluorene] (4-4PySF) were designed and synthesized by combining spirobifluorene moiety with di(pyridine-3-yl)phenyl and di(pyridine-4-yl)phenyl, respectively. The spimbifluorene moiety improves materials' rigid twisted structure to ensure the morphological stability of amorphous film, and pyridine acts as electron acceptor to enhance electron-transporting ability of materials. The dependence of electron-transporting property on the position of substituted pyridine rings was studied. The melting point (T-m) of 4-4PySF is estimated to be 41 degrees C higher than that of 3-4PySF. And the higher current density in the electron only devices exhibited by 4-4PySF revealed the effect of nitrogen atom position on the charge-transporting properties. Green PhOLEDs based on bis(2-phenylpyridine)iridium (III) (2,2,6,6-tetramethylheptane-3,5-diketonate) (Ir (ppy)(2)tmd) as the emitter and 3-4PySF, 4-4PySF and 1,3,5-tris(N-phenylbenzimid azol-2-yl-benzene (TPBi) as ETMs were fabricated. Compared to the device based on the conventional ETM TPBi, the devices based on new ETMs exhibited a higher maximum external quantum efficiency (EQE) of 20.5% and a lower turn-on voltage (V-on) of 2.6 V.
Using a three-dimensional semiclassical method, we theoretically investigate frustrated double ionization (FDI) of Ar atoms subjected to strong laser fields. The double-hump photoelectron momentum distribution generated from FDI observed in a recent experiment [S. Larimian et al., Phys. Rev. Research 2, 013021 (2020)] is reproduced by our simulation. We confirm that the observed spectrum is due to recollision. The laser intensity dependence of FDI is investigated. We reveal that the doubly excited states of Ar atoms and excited states of Ar+ are the dominant pathways for producing FDI at relatively low and high intensities, respectively. The information of which pathway leads to FDI is encoded in the electron momentum distributions. Our work demonstrates that FDI is a general strong-field physical process accompanied with nonsequential double ionization and it can be well understood within the context of recollision scenario.
Abstract The long-term effects of increased temperatures on sediment fluxes in cold regions remain poorly investigated. Here, we examined the multidecadal changes in runoff and sediment fluxes in the Tuotuohe River, a headwater river of the Yangtze River on the Tibetan Plateau (TP). The sediment fluxes and runoff increased at rates of 0.03 ± 0.01 Mt/yr (5.9 ± 1.9%/yr) and 0.025 ± 0.007 ? km3/yr (3.5 ± 1.0%/yr) from 1985 to 2016, with net increases of 135% and 78% from 1985?1997 to 1998?2016, respectively. The increases are primarily due to warming temperature (+1.44°C) and intensified glacier-snow-permafrost melting, with enhanced precipitation (+30%) as a secondary cause. Sediment fluxes are much more susceptible to climate warming than runoff in this undisturbed cold environment. The substantially increased sediment fluxes from the headwater region could threaten the numerous constructed reservoirs and influence the aquatic ecosystems of the TP and its marginal areas.
Silver is an important and efficient bactericide. Nanoscale silver has a large specific surface area, high target adhesion, strong permeability and high bactericidal activity. At present, the control of plant bacterial diseases is difficult, and the resistance of plant bacterial pathogens develops rapidly. Silver nanoparticles are expected to become a new generation of agrochemical to control plant bacterial diseases. In this study, a simple and green natural sunlight-induced method was used to prepare carboxymethylcellulose sodium-stabilized silver nanoparticles (CMC-SNs) with a particle size of around 13.53 +/- 4.72 nm. CMC-SNs were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), energy-dispersive spectrometry (EDS), X-ray diffraction (XRD) and UV-vis spectroscopy and found to be spherical and evenly dispersed. The bacteriostatic activity of the CMC-SNs toward Xanthomonas oryzae pv. oryzae (Xoo) was tested. The minimum inhibitory concentration (MIC) of CMC-SNs to Xoo was 1 mg/L, and the minimum bactericidal concentration (MBC) was 2 mg/L. In addition, the antibacterial mechanism was studied by scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM), which confirmed that the CMC-SNs had high antibacterial activity. In order to verify its impact on the environment, we conducted an acute toxicity test on zebrafish and found that Half lethal concentration (LC(50)) > 100 mg/L in zebrafish, or no acute toxicity. The ability of CMC-SNs to control rice bacterial blight was verified by a pot experiment.
Arsenic contamination has attracted worldwide concerns, owing to its toxicity and severe threat to human and environment. It is urgent to develop efficient adsorbents to remove arsenic pollutants. Within this paper, both pristine MIL-88A(Fe) and MIL-88A(Fe) decorated on cotton fibers were successfully fabricated using an eco-friendly method. The pristine MIL-88A(Fe) displayed outstanding adsorption performances towards four selected arsenic pollutants, in which the adsorption capacities toward As(III), As(V), ROX and ASA were 126.5, 164.0, 261.4 and 427.5 mg g−1, respectively. Additionally, MIL-88A(Fe) exhibited excellent removal efficiencies in a wide pH range and with the presence of different co-existing ions. It was proposed that the coordinative interactions of As–O–Fe between arsenic pollutants and MIL-88A(Fe) contributed to the superior adsorption performances. Furthermore, two MIL-88A(Fe)/cotton fibers composites were synthesized by both post synthesis (MC-1) and in-situ synthesis (MC-2), which demonstrated identically outstanding adsorption activities toward four selected arsenic pollutants. MC-1 and MC-2 enhanced the stability and reusability of MIL-88A(Fe), which was challenging issues of pristine MIL-88A(Fe) powder. Additionally, the fixed-bed column packed by MC-1 or MC-2 can continuously eliminate arsenic pollutants from the water flow. This work provided a new possibility of metal-organic frameworks to accomplish potentially large-scale application to purify the arsenic-contaminated water.
Measurements by semivolatile thermal desorption aerosol gas chromatography (SV-TAG) were used to investigate how semivolatile organic compounds (SVOCs) partition among indoor reservoirs in (1) a manufactured test house under controlled conditions (HOMEChem campaign) and (2) a single-family residence when vacant (H2 campaign). Data for phthalate diesters and siloxanes suggest that volatility-dependent partitioning processes modulate airborne SVOC concentrations through interactions with surface-laden condensed-phase reservoirs. Airborne concentrations of SVOCs with vapor pressures in the range of C13 to C23 alkanes were observed to be correlated with indoor air temperature. Observed temperature dependencies were quantitatively similar to theoretical predictions that assumed a surface-air boundary layer with equilibrium partitioning maintained at the air-surface interface. Airborne concentrations of SVOCs with vapor pressures corresponding to C25 to C31 alkanes correlated with airborne particle mass concentration. For SVOCs with higher vapor pressures, which are expected to be predominantly gaseous, correlations with particle mass concentration were weak or nonexistent. During primary particle emission events, enhanced gas-phase emissions from condensed-phase reservoirs partitioned to airborne particles, contributing substantially to organic particulate matter. An emission event related to oven-usage was inferred to deposit siloxanes in condensed-phase reservoirs throughout the house, leading to the possibility of reemission during subsequent periods with high particle loading.