Contributions of local emissions and regional background to summertime ozone in central China.

Source contributions and regional transport of maximum daily average 8-h (MDA8) O3 during a high O3 month (June 2019) in Henan province in central China are explored using a source-oriented Community Multiscale Air Quality (CMAQ) model. The monthly average MDA8 O3 exceeds ∼70 ppb in more than half of the areas and shows a clear spatial gradient, with lower O3 concentrations in the southwest and higher in the northeast. Significant contributions of anthropogenic emissions to monthly average MDA8 O3 concentrations of more than 20 ppb are predicted in the provincial capital Zhengzhou, mostly due to emissions from the transportation sector (∼50%) and in the areas in the north and northeast regions where industrial and power generation-related emissions are high. Biogenic emissions in the region only contribute to approximately 1-3 ppb of monthly average MDA8 O3. In industrial areas north of the province, their contributions reach 5-7 ppb. Two CMAQ-based O3-NOx-VOCs sensitivity assessments (the local O3 sensitivity ratios based on the direct decoupled method and the production ratio of H2O2 to HNO3) and the satellite HCHO to NO2 column density ratio consistently show that most of the areas in Henan are in NOx-limited regime. In contrast, the high O3 concentration areas in the north and at the city centers are in the VOC-limited or transition regimes. The results from this study suggest that although reducing NOx emissions to reduce O3 pollution in the region is desired in most areas, VOC reductions must be applied to urban and industrial regions. Source apportionment simulations with and without Henan anthropogenic emissions show that the benefit of local anthropogenic NOx reduction might be lower than expected from the source apportionment results because the contributions of Henan background O3 increase in response to the reduced local anthropogenic emissions due to less NO titration. Thus, collaborative O3 controls in neighboring provinces are needed to reduce O3 pollution problems in Henan effectively.

[Characterization of biochar by X-ray photoelectron spectroscopy and 13C nuclear magnetic resonance].

The wood (willow branch) and grass (rice straw) materials were pyrolyzed at different temperatures (300, 450 and 600 °C) to obtain the biochars used in the present study. The biochars were characterized using elementary analysis, X-ray photoelectron spectroscopy (XPS) and solid state 13C cross-polarization and magic angle spinning nuclear magnetic resonance spectroscopy (13C NMR) to illuminate the structure and composition of the biochars which were derived from the different thermal temperatures and biomass. The results showed that the H/C, O/C and (O+N)/C ratios of the biochars decreased with the increase in the pyrolysis temperatures. The surface polarity and ash content of the grass-derived biochars were higher than those of the wood-derived biochars. The minerals of the wood-derived biochars were mainly covered by the organic matter; in contrast, parts of the mineral surfaces of the grass-derived biochars were not covered by organic matter? The 13C NMR of the low temperature-derived biochars revealed a large contribution of aromatic carbon, aliphatic carbon, carboxyl and carbonyl carbon, while the high temperature-derived biochars contained a large amount of aromatic carbon. Moreover, the wood-derived biochars produced at low heat treatment temperatures contained more lignin residues than grass-derived ones, probably due to the existence of high lignin content in the feedstock soures of wood-derived biochars. The results of the study would be useful for environmental application of biochars.

Isolation and characterization of different organic matter fractions from a same soil source and their phenanthrene sorption.

Four humic acids (HAs) including de-ashed HAs (D-HAs), two humins (HMs), nonhydrolyzable carbons, and demineralized fraction (DM) were isolated separately from two soils and characterized detailedly; then their sorption of phenanthrene (Phen) was examined. The sequence of removal of HAs and minerals affected molecular composition of HMs. After de-ashing, thermal stability of HAs was improved; however, sorption (logKoc) also decreased due to removal of amorphous alkyl-C. Significant correlations between CO2 surface area of HAs with their sorption coefficients (n and Koc) suggested that pore filling could dominate Phen sorption. Alkyl-C could facilitate elevated thermal stability of OM and Phen sorption, supporting that thermal stability of OM was correlated with Phen sorption. The OM fraction composed of aromatic moieties (AMs) did not produce the highest logKoc, providing strong evidence to dispute the dominant role of AMs in Phen sorption. No correlations between the Koc values of Phen by all tested sorbents and their bulk or surface polarity were observed, suggesting that the role of bulk or surface polarity of OM fractions in regulating Phen sorption was dependent on soil sources. This work shows the major influence of bulk and surface composition of OM and amorphous alkyl-C isolated from a soil sample on hydrophobic organic compounds sorption.

Impact of deashing treatment on biochar structural properties and potential sorption mechanisms of phenanthrene.

Knowledge of the mineral effects of biochars on their sorption of hydrophobic organic contaminants (HOCs) is limited. Sorption of phenanthrene (PHE) by plant-residue derived biochars (PLABs) and animal waste-derived biochars (ANIBs) obtained at two heating treatment temperatures (HTTs) (450 and 600 °C) and their corresponding deashed biochars was investigated. The decreased surface polarity and increased bulk polarity of biochars after deashing treatment indicated that abundant minerals of biochars benefit external exposure of polar groups associated organic matter (OM). Organic carbon (OC)-normalized distribution coefficients (K(oc)) of PHE by biochars generally increased after deashing, likely due to enhancement of favorable and hydrophobic sorption sites caused by mineral removal. Positive correlation between PHE log K(oc) by PLABs and bulk polarity combined with negative correlation between PHE log K(oc) values by ANIBs and surface polarity suggested PLABs and ANIBs have different sorption mechanisms, probably attributed to their large variation of ash content because minerals influenced OM spatial arrangement within biochars. Results of this work could help us better understand the impact of minerals, bulk/surface polarity, and sorption domain arrangement of biochars on their HOCs sorption and predict the fate of HOCs in soils after biochar application.

Effect of cadmium on the physiological parameters and the subcellular cadmium localization in the potato (Solanum tuberosum L.).

The pollution of agricultural soils with cadmium (Cd) has become a serious problem worldwide. The potato (Solanum tuberosum L.) was used to investigate how different concentrations of Cd (1, 5, and 25mgkg(-1)) affected the physiological parameters and the subcellular distribution of Cd in the potato. The analyses were conducted using scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX). The results suggest that the leaf is the organ with the highest accumulation of Cd. The malondialdehyde (MDA) content increased and the chlorophyll content decreased in response to high level of Cd. The SEM-EDX microanalysis revealed that Cd was primarily deposited in the spongy and palisade tissues of the leaf. Furthermore, Cd was also detected in the cortex and the adjacent phloem and was observed inside the intercellular space, the interior surface of the plasma membrane, and on the surface of the elliptical starch granules in the tubers of the potato. Although low concentrations of Cd migrated from the root to the tuber, the accumulation of Cd in the tuber exceeded the standard for food security. Therefore, the planting of potato plants in farmland containing Cd should be seriously evaluated because Cd-containing potatoes might present high health risk to humans.

Evaluation of a highly condensed SAPRC chemical mechanism and two emission inventories for ozone source apportionment and emission control strategy assessments in China.

The response of summertime O3 to changes in the nitrogen oxides (NOx) and volatile organic compounds (VOC) emissions, and contributions of different NOx and VOC sources to O3 in China are studied using a highly condensed photochemical mechanism in the Statewide Air Pollution Research Center (SAPRC) family (CS07A) and two popular anthropogenic emission inventories, the Multi-resolution Emission Inventory for China (MEIC) and Regional Emission inventory in ASia (REAS). Although CS07A predicts slightly lower O3 concentrations than the standard fix-parameter version of the SAPRC-11 mechanism, the two mechanisms predict almost identical relative responses to daily maximum 8-hour O3 (O3-8h) due to NOx and VOC emission reductions. A source-oriented version of the CS07A is applied to determine source contributions of NOx and VOCs to O3 using MEIC and REAS. The two inventories lead to similar model performance of O3, with MEIC predicting higher O3 in Beijing and Shanghai, especially on high O3 days. Source apportionment results show that industry and transportation are the top two contributors to non-background O3 for both inventories, followed by power and biogenic emissions. In general, the two inventories lead to similar source contribution estimations to O3 attributable to NOx. However, their estimations of relative contributions to VOC-related O3 differ for the industrial and transportation sectors. Differences in the source apportionment results are more significant in some urban areas, although both emissions capture the spatial variations in the source contributions. Our results suggest that future emission control policies should be assessed using multiple emission inventories, and the condensed CS07A is suitable for policy applications when a large number of simulations are needed.

Homogenous Cr and C Doped 3D Self-Supporting NiO Cellular Nanospheres for Hydrogen Evolution Reaction.

Hydrogen evolution reaction (HER) is one promising technique to obtain high-purity hydrogen, therefore, exploiting inexpensive and high-efficiency HER electrocatalysts is a matter of cardinal significance under the background of achieving carbon neutrality. In this paper, a hydrothermal method was used to prepare the Cr-NiC2O4/NF (Ni foam) precursor. Then, the NiO-Cr-C/NF self-supporting HER catalyst was obtained by heating the precursor at 400 °C. The catalyst presents a 3D cellular nanospheres structure which was composed of 2D nanosheets. Microstructure characterization shows that Cr and C elements were successfully doped into NiO. The results of electrochemical measurements and density functional theory (DFT) calculations show that under the synergy of Cr and C, the conductivity of NiO was improved, and the Gibbs free energy of H* (∆GH*) value is optimized. As a result, in 1.0 M KOH solution the NiO-Cr-C/NF-3 (Ni:Cr = 7:3) HER catalyst exhibits an overpotential of 69 mV and a Tafel slope of 45 mV/dec when the current density is 10 mA·cm-2. Besides, after 20 h of chronopotentiometry, the catalytic activity is basically unchanged. It is demonstrated that C and Cr co-doping on the lattice of NiO prepared by a simple hydrothermal method and subsequent heat treatment to improve the catalytic activity and stability of the non-precious metal HER catalysts in an alkaline medium is facile and efficient.

On the Relevancy of Observed Ozone Increase during COVID-19 Lockdown to Summertime Ozone and PM2.5 Control Policies in China.

In February 2020, China's strict lockdown policies led to significant reductions in anthropogenic nitrogen oxides (NOx) emissions, and notable increases in surface ozone (O3) followed in many urban areas, raising concerns about potential rises in summertime O3 due to NOx emission controls. On the basis of O3 isopleths from a series of air quality simulations under different levels of NOx and volatile organic compound (VOC) emission reductions, we found that such concerns are not necessary. As NOx emissions have been reduced in recent years for particulate matter control, future NOx reductions are generally favorable for summertime maximum daily average 8-h (MDA8) O3 reductions. Decreases in summertime O3 due to NOx reductions will also lead to lower atmospheric oxidation capacity, characterized by decreased OH and NO3 concentrations, resulting in further reduction of secondary inorganic aerosols (nitrate, sulfate, and ammonium ion, NSA) formation. VOC emission reductions help to further reduce MDA8 O3 and are needed to control HCHO and primary air toxics simultaneously, but they are ineffective in reducing NSA. This study indicates that a nationwide NOx emission reduction policy has great potential in controlling O3 and PM2.5 simultaneously. However, its effectiveness could be greatly reduced when applied on a limited spatial scale.

Characterization and source apportionment of marine aerosols over the East China Sea.

Awareness of the importance of marine atmosphere for accurately estimating global aerosol budget and climate impacts has arisen recently. However, studies are limited due to the difficulty and inconvenience in sampling as well as the diversity of sources. In this study, the Community Multiscale Air Quality (CMAQ) model was applied to investigate the fine particulate matter (PM2.5) and its chemical components over the East China Sea (ECS) and offshore regions. In spite of slight under-predictions, model predictions agree well with observations over the ECS and along the coast. PM2.5 and its major components in the mainland are higher than in marine area, suggesting Asian continent is a major emitter of marine aerosols. PM2.5 and its components in marine regions show higher abundance during daytime than nighttime, while it is opposite in continental regions. Aerosol phase SO42- is the most abundant component of PM2.5 over the ECS with an average concentration of 5.12 µg m-3, followed by NH4+ (1.02 µg m-3) and primary organic aerosol (POA) (0.92 µg m-3). Industry and ship emissions are the top two contributors to primary (PPM) and total PM2.5 over the ECS, while industry and agriculture sectors are major sources for secondary inorganic aerosols (SIA), followed by ship emissions. For terrestrial regions, industry and agriculture are predominant sources of PM2.5 and SIA, while industry and residential activities are the top two contributors to PPM. This study improves the understanding of transport and accumulation of air pollutants over the ECS and adjacent regions, and provides useful information for designing efficient control strategies.

Primary biogenic and anthropogenic sources of organic aerosols in Beijing, China: Insights from saccharides and n-alkanes.

Sugars and n-alkanes are important organic constituents of atmospheric fine particulate matter (PM2.5). For better understanding their sources and seasonal variations in urban atmosphere, sugar compounds (anhydrosugars, sugars and sugar alcohols) and homologue n-alkanes (C18-C37) were studied in PM2.5 samples collected from September 2013 to July 2014 in Beijing, China. In general, all measured compounds showed the lowest levels in summer. Higher concentrations of sugar compounds and n-alkanes were observed in winter, probably due to elevated combustion emissions (e.g., coal, biofuel and agricultural residue burning) and stable meteorological conditions during heating season. Levoglucosan was the major sugar species in all seasons particularly in autumn and winter, highlighting the significant contribution of biomass burning to fine organic aerosols throughout the whole year especially in cold seasons. Plant waxes contributed to n-alkanes the most in late spring (54.5%) and the least in winter (11.6%); while fossil fuel combustion had the largest contribution in winter (385 ng m-3). The weak odd-carbon predominance of n-alkanes in wintertime aerosols also suggests fossil fuel combustion as the important source of organic aerosols in the heating season. Soil resuspension, fossil fuel combustion and biomass burning, and secondary sources are the main sources of OC in PM2.5 at Beijing. The seasonal variation in source contributions indicates that meteorological condition is a key factor in controlling PM2.5 levels. Furthermore, dust storms in spring can strongly enhance the atmospheric level of fine organic matter in Beijing.

The organic molecular composition, diurnal variation, and stable carbon isotope ratios of PM2.5 in Beijing during the 2014 APEC summit.

Organic tracers are useful for investigating the sources of carbonaceous aerosols but there are still no adequate studies in China. To obtain insights into the diurnal variations, properties, and the influence of regional emission controls on carbonaceous aerosols in Beijing, day-/nighttime PM2.5 samples were collected before (Oct. 15th - Nov. 2nd) and during (Nov. 3rd - Nov. 12th) the 2014 Asia-Pacific Economic Cooperation (APEC) summit. Eleven organic compound classes were analysed using gas chromatography/mass spectrometry (GC/MS). In addition, the stable carbon isotope ratios (δ13CTC) of total carbon (TC) were detected using an elemental analyser/isotope ratio mass spectrometry (EA/irMS). Most of the organic compounds were more abundant during the night than in the daytime, and their concentrations generally decreased during the APEC. These features were associated with the strict regional emission controls and meteorological conditions. The day/night variations of δ13CTC were smaller during the APEC than those before the APEC the summit, suggesting that regionally transported aerosols are potentially played an important role in the loading of organic aerosols in Beijing before the APEC summit. The source apportionment based on the organic tracers suggested that biomass burning, plastic and microbial emissions, and fossil fuel combustion were important sources of organic aerosols in Beijing. Furthermore, a similar contribution of biomass burning to OC before and during the APEC suggests biomass burning was a persistent contributor to PM2.5 in Beijing and its surroundings.

Influence of continental organic aerosols to the marine atmosphere over the East China Sea: Insights from lipids, PAHs and phthalates.

Total suspended particle (TSP) samples were collected during a marine cruise in the East China Sea from May 18 to June 12, 2014. They were analyzed for solvent extractable organic compounds (lipid compounds, PAHs and phthalates) using gas chromatography/mass spectrometry (GC/MS) to better understand the sources and source apportionment of aerosol pollution in the western North Pacific. Higher concentrations were observed in the terrestrially influenced aerosol samples on the basis of five-day backward air mass trajectories, especially for aerosols collected near coastal areas. Phthalates were found to be the dominant species among these measured compound classes (707±401ngm-3 for daytime and 313±155ngm-3 for nighttime), followed by fatty acids, fatty alcohols, n-alkanes and PAHs. In general, the daytime abundances for these compounds are higher than nighttime, possibly attributable to more intensive anthropogenic activities during the daytime. The factor analysis indicates that biomass burning, fungal activities and fossil fuel combustion maybe the main emission sources for organic aerosols over the East China Sea. This study demonstrates that the East Asian continent can be a natural emitter of biogenic and anthropogenic organics to the marine atmosphere through long-range transport, which controls the chemical composition and concentration of organic aerosols over the East China Sea.

Properties of biochar-amended soils and their sorption of imidacloprid, isoproturon, and atrazine.

Biochars produced from rice straw, wheat straw and swine manure at 300, 450 and 600°C were added to soil at 1, 5, 10, or 20% levels to determine whether they would predictably reduce the pore water concentration of imidacloprid, isoproturon, and atrazine. The sorption capacity of the mixtures increased with increasing biochar amounts. The enhanced sorption capacity could be attributed to the increased organic carbon (OC) content and surface area (SA) as well as the decreased hydrophobicity. Biochar dominated the overall sorption when its content was above 5%. The OC contents of the mixtures with 10% and 20% biochar were generally lower than the predicted values. This implies possible interaction between soil components and biochar and/or the effect of biochar oxidation. For soils amended with biochars produced at 300°C, the N2 SA (N2-SA) values were underestimated. The predicted CO2 SA (CO2-SA) values of the mixtures at the biochar content of 10% and 20% were generally higher than the experimental values. Sorption of imidacloprid to the soils amended with biochar at 10% and 20% levels, excluding the soils amended with rice (SR300) and wheat (SW300) straw-derived biochar produced at 300°C, was lower than the predicted value. For SR300 and SW300, the intrinsic sorption capacity of biochar was enhanced by 1.3-5.6 times, depending on the biochar, solute concentration, and biochar dose. This study indicates that biochars would be helpful to stabilize the soil contaminated with imidacloprid, isoproturon, and atrazine, but the sorption capacity of the mixtures could exceed or fall short of predicted values without assuming a cross-effect between soil and biochar.

Size distributions of n-alkanes, fatty acids and fatty alcohols in springtime aerosols from New Delhi, India.

Size-segregated aerosol samples were collected in New Delhi, India from March 6 to April 6, 2012. Homologous series of n-alkanes (C19C33), n-fatty acids (C12C30) and n-alcohols (C16C32) were measured using gas chromatography/mass spectrometry. Results showed a high-variation in the concentrations and size distributions of these chemicals during non-haze, haze, and dust storm days. In general, n-alkanes, n-fatty acids and n-alcohols presented a bimodal distribution, peaking at 0.7-1.1 µm and 4.7-5.8 µm for fine modes and coarse modes, respectively. Overall, the particulate matter mainly existed in the coarse mode (≥2.1 µm), accounting for 64.8-68.5% of total aerosol mass. During the haze period, large-scale biomass burning emitted substantial fine hydrophilic smoke particles into the atmosphere, which leads to relatively larger GMDs (geometric mean diameter) of n-alkanes in the fine mode than those during the dust storms and non-haze periods. Additionally, the springtime dust storms transported a large quantity of coarse particles from surrounding or local areas into the atmosphere, enhancing organic aerosol concentration and inducing a remarkable size shift towards the coarse mode, which are consistent with the larger GMDs of most organic compounds especially in total and coarse modes. Our results suggest that fossil fuel combustion (e.g., vehicular and industrial exhaust), biomass burning, residential cooking, and microbial activities could be the major sources of lipid compounds in the urban atmosphere in New Delhi.

Variation in sorption of propiconazole with biochars: The effect of temperature, mineral, molecular structure, and nano-porosity.

Sorption behavior of propiconazole (PROPI) by plant-residue derived biochars (PLABs) and animal waste-derived biochars (ANIBs) obtained at three heating treatment temperatures (HTTs) (300, 450 and 600 °C) (e.g., BCs300, BCs450, and BCs600) and their corresponding de-ashed BCs450 was investigated. PLABs belonged to high- or medium-C biochars and ANIBs were low-C biochars. Surface C concentrations of the tested biochars were generally higher than their corresponding bulk C. Surface polar groups were mainly composed of O-containing groups of minerals within biochars. The nonlinearity coefficients (n) of propiconazole (PROPI) sorption isotherms ranged from 0.23 to 0.64, which was significantly and negatively related to organic carbon (OC)-normalized CO2-surface area (CO2-SA/OC) of biochars. This correlation along with the positive relationship between CO2-SA/OC and aromaticity indicates that pore-filling in nanopores within aromatic C dominate nonlinear PROPI sorption. HTTs or C contents do not necessarily regulate PROPI sorption. Removal of minerals from BCs450 elevated PROPI sorption because minerals may exert certain influence on sorption via impacting spatial arrangement of polar groups and/or organic matter (OM)-mineral interactions. This study helps to better understand sorption behavior of PROPI to biochars and evaluate the potential role of biochar in water treatment systems.

Single-solute and bi-solute sorption of phenanthrene and dibutyl phthalate by plant- and manure-derived biochars.

The spatial arrangement of biochar and the exact underlying interaction mechanisms of biochar and hydrophobic organic compounds both remain largely unknown. The sorption of dibutyl phthalate (DBP) and phenanthrene (PHE) to plant- and manure-derived biochars in both single- and bi-solute systems was investigated. The significant positive relation between surface polarity and ash content suggests that minerals benefit the external distribution of polar groups on particle surfaces. PHE and DBP sorption by the biochars was regulated by their surface polarity. The PHE generally displayed a pronounced enhancement of DBP sorption, likely resulting from the formation of biochar-PHE-DBP complexes, suggesting that DBP and PHE had different sorption sites on the biochars. The enhancement of Cd(2+) (a soft Lewis acid) on DBP sorption implied that π-π interactions should not dominate DBP sorption by biochars. The influence of Cd(2+) on PHE sorption by biochars would depend on the balance between suppressive sorption by Cd(2+)PHE bonding and enhanced sorption by Cd(2+)-complexed functionalities, and the amounts of Cd(2+) adsorbed by biochars determined the relative role of increased sorption by Cd(2+) in the overall PHE sorption.

Sorption of phthalic acid esters in two kinds of landfill leachates by the carbonaceous sorbents.

Sorption of phthalic acid esters (PAEs: diethyl phthalate, DEP: dibutyl phthalate, DBP as model compounds) in landfill leachates by activated carbon (AC), carbon nanotubes (CNTs), and biochars, were examined. The young leachate (YL) and old leachate (OL) were synthesized to imitate acetogenic and methanogenic phases, respectively, and glucose (GLU) and fulvic acid (FA) were selected to represent dissolved organic matter (DOM). GLU in leachates generally facilitated the sorption of PAEs while FA restrained sorption of PAEs, suggesting the type of DOM associated with leachates possibly regulated the removal efficiency of PAEs from leachates. The pores and organic carbon of carbonaceous sorbents should be major factors in influencing the sorption of PAEs in leachates. The data showed PAEs in acetogenic leachates was removed more easily than those in methanogenic leachates and CNTs have the less advantage to remove PAEs from methanogenic leachates compared to AC.