Biomass burning (BB) seriously affect air pollution, human health and global climate. A severe pollution episode (PE) caused by BB was investigated in the southern Sichuan Basin (SSB), one of the most polluted areas in China. Hourly variations in criteria air pollutants (PM2.5, PM10, SO2, NO2, CO, and O3), chemical components, and sources of PM2.5 before, during, and after the severe regional air PE were characterized at three sites, namely Neijiang (NJ), Zigong (ZG), and Yibin (YB). The results showed that combination of intensive pollution from BB, stable meteorological conditions, and the basin topography caused this severe regional PE in the SSB. The average daily concentrations of PM2.5 during the PE were 1.8–6 times those measured during the periods before and after the PE, and 4.0–7.4 times that of World Health Organization air quality guidelines in the SSB. The highest PM levels occurred in ZG, where the peak values of PM2.5 and PM10 reached 536 μg m−3 and 578 μg m−3 at night, respectively. PM10, NO2, and CO also increased dramatically at night in the SSB. O3 formation was affected by BB, showing lower levels at night but higher levels in the day during the PE than before and after the PE, whereas SO2 levels were not affected. Sulfate–nitrate–ammonium in PM2.5 was the main chemical compositions before the PE, whereas organic matter (OM) and K+ became characteristics compositions during and after the PE. Higher OC/EC and Kexcess/EC ratios were observed during the PE and Kexcess/EC ratio was a better indicator of BB in the SSB than OC/EC ratio. The results of a positive matrix factorization model indicated that BB was the most significant contributor to PM2.5 during the PE, accounting for 58% in NJ, 65% in ZG, and 56% in YB. Backward trajectory analysis confirmed that the SSB is susceptible to pollutants from Chongqing and other surrounding cities, especially in ZG and NJ, due to the unique topography of the basin. Our findings suggest that BB in the basin topography can cause severe regional air pollution events at night, thus supporting the critical need for BB control in the basin to improve regional air quality.
Phthalate esters, commonly used as plasticizers, can be found indoors in the gas phase, in airborne particulate matter, in dust, and on surfaces. The dynamic behavior of phthalates indoors is not fully understood. In this study, time-resolved measurements of airborne phthalate concentrations and associated gas-particle partitioning data were acquired in a normally occupied residence. The vapor pressure and associated gas-particle partitioning of measured phthalates influenced their airborne dynamic behavior. Concentrations of higher vapor pressure phthalates correlated well with indoor temperature, with little discernible influence from direct occupant activity. Conversely, occupant-related behaviors substantially influenced the concentrations and dynamic behavior of a lower vapor pressure compound, diethylhexyl phthalate (DEHP), mainly through production of particulate matter during cooking events. The proportion of airborne DEHP in the particle phase was experimentally observed to increase under higher particle mass concentrations and lower indoor temperatures in correspondence with theory. Experimental observations indicate that indoor surfaces of the residence are large reservoirs of phthalates. The results also indicate that two key factors influenced by human behavior—temperature and particle mass concentration—cause short-term changes in airborne phthalate concentrations.
Abstract We investigate source characteristics and emission dynamics of volatile organic compounds (VOCs) in a single-family house in California utilizing time- and space-resolved measurements. About 200 VOC signals, corresponding to more than 200 species, were measured during 8 weeks in summer and five in winter. Spatially resolved measurements, along with tracer data, reveal that VOCs in the living space were mainly emitted directly into that space, with minor contributions from the crawlspace, attic, or outdoors. Time-resolved measurements in the living space exhibited baseline levels far above outdoor levels for most VOCs; many compounds also displayed patterns of intermittent short-term enhancements (spikes) well above the indoor baseline. Compounds were categorized as ?high-baseline? or ?spike-dominated? based on indoor-to-outdoor concentration ratio and indoor mean-to-median ratio. Short-term spikes were associated with occupants and their activities, especially cooking. High-baseline compounds indicate continuous indoor emissions from building materials and furnishings. Indoor emission rates for high-baseline species, quantified with 2-hour resolution, exhibited strong temperature dependence and were affected by air-change rates. Decomposition of wooden building materials is suggested as a major source for acetic acid, formic acid, and methanol, which together accounted for \~75% of the total continuous indoor emissions of high-baseline species.
Carbonyl compounds (carbonyls) play important roles in atmospheric photochemistry, serving as reservoirs of radicals (OH, HO2, and RO2) and precursors of secondary organic aerosols (SOA). Field measurements of gaseous and particulate carbonyls were taken over urban Beijing during summer and winter, and field-measured gas-particle partitioning coefficients (Kp ) were determined. Compared with theoretical values, field-measured Kp values were 4–6 orders of magnitude higher for the six detected carbonyls, which underlined the importance of heterogeneous reactions. In winter, the Kp values of carbonyl compounds were one order of magnitude higher than those in summer owing to the effect of temperature. This study applied the positive matrix factorization (PMF) model to the source apportionment of carbonyl compounds. Five factors were identified for both summer and winter, whereas the biogenic factor was only identified in summer and coal burning was only found in winter. In summer, secondary formation was the largest contributor (39%) to the measured total carbonyl compounds levels. In contrast, vehicular exhaust was the largest source of the measured total carbonyl compounds in winter (37%), although secondary formation still had an important contribution of 31%. The contribution of coal burning to ambient carbonyls was reduced by half compared with prior results. As the most abundant carbonyl compound in the atmosphere, formaldehyde in summer mainly came from secondary production (42%) and primary anthropogenic emissions (48%), while biogenic sources had a minor contribution (10%). However, 78% of formaldehyde was attributed to primary anthropogenic emissions in winter, which indicated that these winter emissions were more important sources of carbonyl compounds. Glyoxal was always dominated by secondary formation, with contributions of 56% in summer and 52% in winter.
The efficient ternary all-polymer solar cells (PSCs) are designed and fabricated, using a polymer acceptor of NDP-V-C7 and analogue co-donors containing a chlorinated polymer PBClT and classical PTB7-Th. PBClT and PTB7-Th possess very similar chemical structure and matched energy levels to form the cascade of the co-donors. Meanwhile, benefiting from those analogous polymer structures, there is little influence of the morphology in blend film compared to their pristine polymer films. The binary PBClT:NDP-V-C7 devices exhibit a high open-circuit voltage (Voc) due to the deep HOMO level of PBClT. The Voc of all-PSCs could be finely manipulated by adjusting the content of PBClT in blend film. The ternary all-PSCs have the more balanced charge mobility and prolonged carrier lifetime compared to the binary devices. The PBClT also help improve the miscibility of ternary blend and suppress crystallization in films, bringing about favorable morphology with appropriate orientation and surface roughness in blend film. With the optimal processing, the champion ternary all-PSCs obtain a high PCE of 9.03%, which is about 10% enhancement compared to that of binary device. The results indicate that the ternary approach using analogue co-donors is a practical method to enhance the performance of all-PSCs.
Titanate nanotubes (TNTs) have been reported to show good adsorption performance for heavy metals, but researches on organic contaminants adsorption by TNTs are limited. In this study, co-adsorption of a heavy metal (Cu) and an emerging organic contaminant (ciprofloxacin, CIP) by TNTs was investigated in binary systems. TNTs could simultaneously remove the two contaminants, with a high adsorption capacity of 234.5 μmol/g for Cu(II) and 237.0 μmol/g for CIP at pH 4 in the binary system. pH greatly affected adsorption due to speciation variation of the contaminants and surface charge change of TNTs. Cu(II)-CIP complexes dominated adsorption capacity and mechanism. Adsorption of CIP was promoted by high concentration of Cu(II) at pH 3–8 due to formation of abundant Cu(CIP±)2+, while inhibited by low concentration of Cu(II) because of competitive adsorption. The adsorption affinity of CIP species to TNTs was ranked as: Cu(CIP±)2+ > CIP+ > CIP± > Cu(CIP±)2+ > Cu(CIP−·CIP±)+ > CIP−. In comparison, the co-existence of CIP slightly affected Cu(II) adsorption considering the strong affinity of Cu2+ to TNTs. X-ray photoelectron spectrometer (XPS) and Fourier transform infrared spectroscopy (FTIR) results further confirmed the formation of Cu(II)-CIP complexes through –NH2Cu/–COOCu linkages. This work not only proposed a feasible technology for co-removal of heavy metals and organics from water, but also presented insight into interaction mechanisms of different contaminants with nanomaterials during adsorption.
This paper investigates an optimal scheduling method for the operation of combined cycle gas turbines (CCGT). The objective is to minimize the CO2 emissions while supplying both electrical and thermal loads. The paper adopts a detailed model of the units in order to relate the heat and power outputs. The grid constraints as well as system losses are considered for both the electrical and thermal systems. Finally, the optimal power dispatch lies on the hybridization of a Mixed Integer Linear Programing (MILP) scheduling with a greedy search method. Different sets of simulations are run for a small 5-bus test case and a larger model of Jurong Island in Singapore. Several load levels are considered for the heat demand and the impact of the steam pipe capacities is highlighted.
Global livestock husbandry provides ecosystem goods and services but also emits 7.1 Gt CO2-eq. of greenhouse gases (GHGs) per year. To lower GHG emissions intensity, appropriate production management systems should be identified. Since the 1980s, grassland livestock husbandry in China has transformed gradually from pastoralism into individual household management under the Grassland Household Contract System Policy. However, little is known about how this transition influences GHG emissions. We selected two case study sites representing two different forms of rangeland management systems in Ruoergai county of the Qinghai-Tibet Plateau, viz. 1) household-based all year continuous grazing under the individual use of rangeland with fences demarcating boundaries; 2) community-based seasonal grazing under the common use of the whole rangeland. The objective was to examine the differences in greenhouse gas emission intensity between the two systems using life cycle assessment (LCA). The results showed that the transition from community-based seasonal grazing into household-based continuous grazing increased the GHG emissions intensity from -0.62 kgCO2-eq/kg meat to 10.51 kgCO2-eq/kg meat. The increase was primarily attributed to changes in soil carbon storage. Findings suggest that to minimize GHG emissions and environmental degradation, community-based seasonal grazing in the pastoral area of Qinghai-Tibet Plateau should be maintained. Enhancing soil carbon sequestration by adopting appropriate practices would further reduce the GHG emissions intensity arising from the livestock system.
In this letter, a distributed network model describing the effects of the border traps and distributed channel resistance on the impedance frequency dispersion of lateral MOS devices is proposed. The proposed model is verified using a gate recessed, normally-off Al2O3/GaN MOSFET structure operating as a MOS diode. The measured frequency-dependent capacitance and conductance curves of the MOS diode over a wide frequency range are found to be in good agreement with the proposed model. According to the intrinsic property of border traps to the ac signal, the proposed model is further modified to get the spatial distribution of border traps. The new insight derived from the impedance dispersion characteristics of lateral MOS devices is critical for quantitative analysis of the quality of III-V lateral MOS structures.
BACKGROUND: A 'mortality risk score' (MS) based on ten prominent mortality-related cytosine-phosphate-guanine (CpG) sites was previously associated with all-cause mortality, but has not been verified externally. We aimed to validate the association of MS with mortality and to compare MS with three aging biomarkers: telomere length (TL), DNA methylation age (DNAmAge) and phenotypic age (DNAmPhenoAge) to explore whether MS can serve as a reliable measure of biological aging and mortality. METHODS: Among 534 males aged 55-85 years from the US Normative Aging Study, the MS, DNAmAge and DNAmPhenoAge were derived from blood DNA methylation profiles from the Illumina HumanMethylation450 BeadChip, and TL was measured by quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS: A total of 147 participants died during a median follow-up of 9.4 years. The MS showed strong associations with all-cause, cardiovascular disease (CVD) and cancer mortality. After controlling for all potential covariates, participants with high MS (>5 CpG sites with aberrant methylation) had almost 4-fold all-cause mortality (hazard ratio: 3.84, 95% confidence interval: 1.92-7.67) compared with participants with a low MS (0-1 CpG site with aberrant methylation). Similar patterns were observed with respect to CVD and cancer mortality. MS was associated with TL and DNAmPhenoAge acceleration but not with DNAmAge acceleration. Although the MS and DNAmPhenoAge acceleration were independently associated with all-cause mortality, the former exhibited a higher predictive accuracy of mortality than the latter. CONCLUSIONS: MS has the potential to be a prominent predictor of mortality that could enhance survival prediction in clinical settings.
