Multiple Sulfur Isotope Constraints on Sources and Formation Processes of Sulfate in Beijing PM2.5 Aerosol.

Recently air pollution is seriously threatening the health of millions of people in China. The multiple sulfur isotopic composition of sulfate in PM2.5 samples collected in Beijing is used to better constrain potential sources and formation processes of sulfate aerosol. The Δ33S values of sulfate in PM2.5 show a pronounced seasonality with positive values in spring, summer and autumn and negative values in winter. Positive Δ33S anomalies are interpreted to result from SO2 photolysis with self-shielding, and may reflect air mass transport between the troposphere and the stratosphere. The negative Δ33S signature (-0.300‰ < Δ33S < 0‰) in winter is possibly related to incomplete combustion of coal in residential stoves during the heating season, implying that sulfur dioxide released from residential stoves in more rural areas is an important contributor to atmospheric sulfate. However, negative Δ33S anomalies (-0.664‰ < Δ33S ← 0.300‰) in winter and positive Δ33S anomalies (0.300‰ < Δ33S < 0.480‰) in spring, summer, and autumn suggest sulfur isotopic equilibrium on an annual time frame, which may provide an implication for the absence of mass-independent fractionation of sulfur isotopes (S-MIF) in younger sediments. Results obtained here reveal that reducing the usage of coal and improving the heating system in rural areas will be important for efficiently decreasing the emissions of sulfur in China and beyond.

Source contributions to two super dust storms over Northern China in March 2021 and the impact of soil moisture.

Two extremely devastating super dust storms (SDS) hit Mongolia and Northern China in March 2021, causing many deaths and substantial economic damage. Accurate forecasting of dust storms is of great importance for avoiding or mitigating their effects. One of the most critical factors affecting dust emissions is soil moisture, but its value in desert exhibits significant uncertainty. In this study, model experiments were conducted to simulate dust emissions using four soil moisture datasets. The results were compared with observations to assess the effects of soil moisture on the dust emission strength. The Integrated Source Apportionment Method (ISAM) was used to track the dust sources and quantify the contribution from each source region to the dust load over the North China Plain (NCP), Korea peninsula, and western Japan. The results show large differences in the dust load depending on the soil moisture datasets used. The high soil moisture in the NCEP dataset results in substantial underestimation of the dust emission flux and PM10 concentration. Despite a minor overestimation of PM10 concentrations in many Northern China cities, the ERA5 dataset yields the best simulation performance. During the two SDS events, about 7.5 Mt dust was released from the deserts in Mongolia and 2.8 Mt from the deserts in China. Source apportionment indicates that the Mongolian Gobi Desert is the dominant source of PM10 in the NCP, Korea peninsula, and western Japan, accounting for 60 %-80 %, while Inner Mongolia contributed 10 %-20 %.

Slight transition in Chinese atmospheric Pb isotopic fingerprinting due to increasing foreign Pb.

Atmospheric lead (Pb) pollution negatively affects human health and ecosystem, and extensive research is required to identify its sources and develop robust mitigation methods. In this study, the concentration and isotopic composition of Pb in fine particulate matter (PM2.5) at five sites in the China's Beijing-Tianjin-Hebei (BTH) region were analyzed. The results showed that the Pb concentration in the BTH region declined along the northwest direction in winter owing to the East Asian monsoon. Pb isotopic signatures confirmed that anthropogenic activities significantly contributed to Pb pollution, compared with natural sources. With the increasing import of foreign Pb (with a relatively lower 208Pb/206Pb ratio) to China, we hypothesized that the unique isotopic signature of Pb in Chinese aerosols may decline over time. Therefore, the application of the isotopic approach for quantifying Pb transported from China should be carefully appraised in future research to provide a realistic estimate of the contribution of local sources and the transboundary effect consistent with air mass trajectories analysis. This study provides a theoretical reference for supporting the utilization of Δ208Pb values for better clarify the transboundary impact of Pb pollution and to reduce international disputes.

Increase of antibiotic resistance genes via horizontal transfer in single- and two-chamber microbial electrolysis cells.

Microbial electrolysis cells (MECs) have been applied for antibiotic degradation but simultaneously induced antibiotic resistance genes (ARGs), thus representing a risk to disseminate antibiotic resistance. However, few studies were on the potential and risk of ARGs transmission in the MECs. This work assessed conjugative transfer of ARGs under three tested conditions (voltages, cell concentration, and donor/recipient ratio) in both single- and two-chamber MECs. The results indicated that voltages (> 0.9 V) facilitated the horizontal frequency of ARGs in the single-chamber MECs and anode chamber of two-chamber MECs. The donor cell number (donor/recipient ratio was 2:1) increased the transfer frequency of ARGs. Furthermore, voltages ranged from 0.9 to 2.5 V increased reactive oxygen species (ROS) production and cell membrane permeability in MECs. These findings offer new insights into the roles of ARG transfer under different applied voltages in the MECs, which should not be ignored for horizontal transfer of antibiotic resistance.

Atmospheric lead pollution in a typical megacity: Evidence from lead isotopes.

Atmospheric lead (Pb) pollution has adverse health effects on humans, while the sources and atmospheric process of Pb are key scientific problems. In this study, the concentrations and isotopic composition of Pb in fine particulate matter (PM2.5), coal and street dust samples collected from a typical megacity Beijing were analyzed to identify the sources of atmospheric Pb. Results showed that the Pb concentrations in PM2.5 were high in winter (168.1 ± 32.0 ng/m3) and low in summer (27.7 ± 9.1 ng/m3), whereas Pb isotopic values presented opposite variation trends. The abnormally elevated Pb concentrations in winter were probably related to coal combustion, while declined Pb concentration in summer may be attributed to favorable meteorological parameters such as high temperature, high wind speed, and frequent rain events. Pb isotopic ratios indicated that anthropogenic sources (coal combustion and vehicle exhaust) and natural sources were the main contributors to Pb in PM2.5. Combined with the binary model, the anthropogenic sources predominantly contributed to Pb in the Beijing atmosphere by approximately 85% annually, while the natural sources accounted for the rest of 15%. More specifically, the contribution of natural sources was about 9.4% in spring, 29.7% in summer, 16.0% in autumn and 6.1% in winter, suggesting that natural sources might contribute more lead into the atmosphere during clear days. Furthermore, the contribution of the vehicle exhaust to atmospheric Pb was nonnegligible in megacity, highlighting that the ownership of motor vehicles in megacity should be regulated and more efforts should be paid to strengthen vehicle emission standard. This study may enrich the reservoir of Pb isotopic composition in nature and provides a new method to investigate the Pb migration and transformation in the environment, and also serve as a theoretical reference for pollution control measures.

Monoclinic dibismuth tetraoxide (m-Bi2O4) for piezocatalysis: new use for neglected materials.

Piezocatalysis is a promising approach for environmental pollutant removal. Monoclinic dibismuth tetraoxide (m-Bi2O4) was first applied to piezocatalyze organics under ultrasonic vibration. The built-in electric field with ultrasonic stress drives the separation of holes and electrons in m-Bi2O4. Its excellent piezocatalytic activity, reusability and chemical stability make m-Bi2O4 a new candidate of piezocatalysis.

[Quantitative remote sensing retrieval for algae in inland waters].

Chlorophyll is a very important indictor for the eutrophication status of lake water body. Using remotely sensed data to achieve real-time dynamic monitoring of the spatial distribution of chlorophyll has great importance. This paper aims to find the best band for the hyperspectral ratio model of chlorophyll-a, and take advantage of this model to implement remote sensing retrieval of algae in Taihu Lake. By the analysis of the spectral reflectance and water quality sampling data of the surface water body, the regression model between the ratio of reflectance and chlorophyll-a was built, and it was showed that the ratio model between the wavelengths around 700 and 625 nm had a relatively high coefficient value of determination (R2), while the ratio model constructed with 710 nm and visible wavelengths showed a descended R2 following with the increment of the visible wavelengths. Combined with in-situ water samplings analysis and spectral reflectance measurement, the results showed that it's possible to retrieve algae water body using the MODIS green index (GI). The spatial distributions of chlorophyll-a and algae in Taihu Lake were extracted successfully using MODIS data with the algorithm developed in this paper.

Fluoride removal efficiencies and mechanism of schwertmannite from KMnO4/MnO2-Fe(II) processes.

Fluoride has an adverse effect on both the environment and industrial production. In particular, wastewater from smelting systems containing high concentrations of fluoride is a major cause of fluoride pollution. Based on the characteristics of such wastewater, a targeted and integrated method for removal fluoride using schwertmannite is proposed. The schwertmannite, prepared from the oxidation of Fe(II) by KMnO4 (Ksw) and MnO2(Msw), effectively removed fluoride within 30 min under certain conditions. Under most experimental conditions, the removal efficiency of F ion by Ksw was always 13 % higher than that by Msw, which is attributed to the different concentrations of OH- and SO42- for ion exchange. The calculations showed that the chemical formulas of Ksw and Msw are Fe8O8(OH)5.42±0.04(SO4)1.29±0.02 and Fe8O8(OH)5.28±0.04(SO4)1.36±0.02, respectively. In the Ksw system, 0.70 mol of OH- and 0.30 mol of SO42- were released per mole of F ions sorbed; those released for the Msw system were 0.69 mol and 0.31, respectively. The results showed that OH- played a primary role in the ion exchange and the schwertmannite showed good practicability for actual industrial wastewater.

Seasonal and long-term trends of sulfate, nitrate, and ammonium in PM2.5 in Beijing: implication for air pollution control.

Particulate matter pollution in Beijing is a serious environmental problem. In response to this, the Beijing government has implemented comprehensive emission reduction measures in recent years. To assess the effectiveness of these measures, the seasonal and long-term trends in chemical compositions of PM2.5 in Beijing have been studied based on daily samples collected from July 2015 to April 2016 and literature investigation (2000-2014). Results show that the concentrations of sulfate, nitrate, and ammonium in PM2.5 have significant seasonal variations, which are related to the changes in meteorological conditions and emission intensities. In addition, the long-term data display that the concentrations of sulfate, nitrate, and ammonium have significantly decreased between 2013 and 2016, which are consistent with the reduction in PM2.5 levels (~ 11.2 µg/m3 per year). The declines could not be interpreted by the meteorological factors. It suggests that the air pollution control measures in Beijing (2013-2016), especially the decreasing consumption of coal, can effectively decrease the mass concentration of fine particles. To further improve the air quality, similar measures should be adopted in the areas around Beijing. These air pollution control measures taken in Beijing can provide invaluable guidance for mega-cities in China and other developing countries to decrease their PM2.5 concentration and reduce health risk from particulate pollution.

Degradation of 2,4-dinitrophenol by combining sonolysis and different additives.

Based on the effects of various additives on ultrasonic degradation of 2,4-dinitrophenol (DNP) in aqueous solution, the degradation mechanisms and reaction kinetics of DNP in different processes were proposed. The results showed that some additives, such as CuO, CCl(4), O(3), NaCl and KI, were favorable for DNP sonochemical degradation. On the contrary, DNP degradation efficiency was restrained by Na(2)CO(3), indicating that OH radicals oxidation played an important role in DNP ultrasonic removal. The significant increases in DNP degradation in US/CuO/H(2)O(2), US/CCl(4) and US/O(3) systems were also related to the intermediates formed during the reactions, such as HO(2)/O(2)(-) radicals, chlorine-containing radicals and HClO. In addition, DNP ultrasonic removal was observed to behave as pseudo-first-order kinetics under different experimental conditions tested in the present work.

[Sulfur Sources and Oxidation Pathways in Summer Aerosols from Nanjing Northern Suburbs Using S and O Isotopes].

The sulfur and oxygen isotopic compositions of sulfate in PM2.5 were determined by EA-IRMS to study the sulfur sources and oxidation formation pathways of sulfates in PM2.5 from Nanjing northern suburbs during July 2014. The results indicated that δ34 S values of sulfate ranged from 1.7‰ to 4.8‰ with an average of 3.2‰±1.0‰, while δ18O values ranged from 7.5‰ to 12.9‰ with an average of 9.3‰±1.7‰. Comparing the δ34 S values of aerosol sulfate and potential pollution sources, we concluded that the sulfur source of PM2.5 was mainly local coal combustion and vehicle exhaust. In addition, the secondary sulfate was dominant in PM2.5, and 59.3% of the formation of the secondary sulfate was caused by SO2 homogeneous oxidation. In addition, the heterogeneous oxidation of SO2 in the atmosphere was dominated by ferrous iron oxidation in excess O2. The main mechanisms of homogeneous oxidation include oxidation in the presence of electric discharge (presumably forming O3) and NO2.

[Chemical Constitution and Carbon Isotopic Compositions of PM2.5 in the Northern Suburb of Nanjing in Spring].

PM2.5 is an important atmospheric pollution component and has a complicated composition. The chemical constitution of PM2.5 in Nanjing northern region during March 2016 was analyzed using the Dinoex ICS-3000 and ICS-2000 ion chromatograph and DRI Model 2001A thermal/optical carbon analyzer, and the carbon isotopic compositions were analyzed using EA-IRMS from Thermo Scientific in order to explore pollution behaviors and source apportionment of PM2.5. The results showed that the mean concentration of atmospheric PM2.5 was (106.16±48.70) µg·m-3, which equated with heavy pollution. Meanwhile, 88% of the samples exhibited the presence of the secondary organic pollutants. The average concentration of secondary organic carbon (SOC) was (3.58±2.78) µg·m-3 and this high concentration was attributed to the reaction of O3 with atmospheric hydrocarbons under ultraviolet light on sunny days. In addition, δ13CTC in PM2.5 ranged from -26.56‰ to -23.75‰ and the mean was (-25.47‰±0.63‰). Combining the various analyses, we concluded that atmospheric PM2.5 for the study area was mainly derived from coal combustion, vehicle exhaust, geology (natural sources) and biomass burning.

Improvement in properties of coal water slurry by combined use of new additive and ultrasonic irradiation.

Coal water slurry (CWS) was prepared with a newly developed additive from naphthalene oil. The effects of ultrasonic irradiation on coal particle size distribution (PSD), adsorption behavior of additive in coal particles and the characteristics of CWS were investigated. Results showed that ultrasonic irradiation led to a higher proportion of fine coal in CWS and increased the saturated adsorption amount of additive in coal particles. In addition, the rheological behavior and static stability of CWS irradiated by ultrasonic wave were remarkably improved. The changes on viscosity of CWS containing 1% and 2% additive are qualitatively different with the increasing sonication time studied. The reason for the different effect of sonication time on CWS viscosity is presented in this study.

Phosphorus removal from aqueous solution in parent and aluminum-modified eggshells: thermodynamics and kinetics, adsorption mechanism, and diffusion process.

Parent and aluminum-modified eggshells were prepared and characterized with X-ray diffraction, specific surface area measurements, infrared spectroscopy, zeta potential, and scanning electron microscope, respectively. Besides, phosphorus adsorptions in these two eggshells at different temperatures and solution pH were carried out to study adsorption thermodynamics and kinetics as well as the mechanisms of phosphorus adsorption and diffusion. The results indicated that high temperature was favorable for phosphorus adsorption in parent and aluminum-modified eggshells. Alkaline solution prompted phosphorus adsorption in parent eggshell, while the maximum adsorption amount was achievable at pH 4 in aluminum-modified eggshell. Adsorption isotherms of phosphorus in these eggshells could be well described by Langmuir and Freundlich models. Phosphorus adsorption amounts in aluminum-modified eggshell were markedly higher compared to those in parent eggshell. Adsorption heat indicated that phosphorus adsorption in parent eggshell was a typically physical adsorption process, while chemical adsorption mechanism of ion exchange between phosphorus and hydroxyl groups on the surface of eggshells was dominated in aluminum-modified eggshell. The time-resolved uptake curves showed phosphorus adsorption in aluminum-modified eggshell was significantly faster than that in parent eggshell. Moreover, there existed two clear steps in time-resolved uptake curves of phosphorus in parent eggshell. Based on pseudo-second order kinetic model and intraparticle diffusion model, we inferred more than one process affected phosphorus adsorption. The first process was the diffusion of phosphorus through water to external surface and the opening of pore channel in the eggshells, and the second process was mainly related to intraparticle diffusion.

Gamma irradiation-induced decomposition of sulfamethoxazole in aqueous solution: the influence of additives, biological inhibitory, and degradation mechanisms.

Sulfamethoxazole (SMX) was decomposed by using gamma irradiation in the presence of different additives such as NO3-, NO2-, Cr(VI), 2-propanol, and tert-butanol. The results demonstrated that NO3-, NO2-, 2-propanol, and tert-butanol inhibited SMX radiolytic removal. However, there existed a synergetic effect for radiolytic removal of the mixture containing SMX and Cr(VI). At an absorbed dose of 150 Gy, the removal percentages of SMX and Cr(VI) in the mixture were 73.5 and 84.6%, respectively, which was higher than the removal percentages of 70.6 and 4.1% for the single component of SMX and Cr(VI). This provides us an insight into treating the combined pollution in micro-polluted water. The SMX radiolytic removal followed a pseudo first-order reaction kinetic model, and the rate constant ratios of ·OH, eaq-, and H· towards SMX radiolysis were 10.4:1:2.9. In addition, 24-h bio-inhibitory to the macroalgae of SMX solution during gamma irradiation reached the maximum of 0.85 at an adsorbed dose of 100 Gy, then gradually decreased with the increasing adsorbed dose. Based on LC-MS analysis and quantum chemical calculation, the degradation intermediates were determined and concluded that SMX radiolytic removal was mainly via ·OH radical attack and direct decomposition of SMX molecule by gamma ray.

Nitrate removal, spatiotemporal communities of denitrifiers and the importance of their genetic potential for denitrification in novel denitrifying bioreactors.

Nitrate treatment performance and denitrification activity were compared between denitrifying biological filters (DNBFs) based on dewatered alum sludge (DAS) and neutralized used acid (NUA). The spatiotemporal distribution of denitrifying genes and the genetic potential associated with denitrification activity and nitrate removal in both DNBFs were also evaluated. The removal efficiency of NUA-DNBF increased by 8% compared with that of DAS-DNBF, and the former NUA-DNBF emitted higher amount of N2O. Analysis of abundance and composition profiles showed that denitrifying gene patterns varied more or less in two matrices with different depths at three sampling times. Burkholderiales, Rhodocyclales, and Rhizobiales were the most commonly detected in both media during stable periods. Denitrification was determined by the abundance of specific genes or their ratios as revealed by controlling factors. The enhanced nitrate removal could be due to increasing qnosZ or decreasing ∑qnir/qnosZ. Furthermore, NUA-DNBF solely reduced nitrate by increasing the denitrification enzyme activity.

Sonodegradation of halomethane mixtures in chlorinated drinking water.

Ultrasonic degradation of halomethane mixtures, with very low initial concentration in chlorinated drinking water was investigated. It was observed that the removal efficiencies of four halomethanes after 1 h ultrasonic irradiation followed the increasing order: CHCl(3) < CHBr(2)Cl < CHBrCl(2) < CCl(4) and the degradation reactions of the halomethanes were well described by the pseudo-first-order kinetics model. Molecular polarity was found to be an important factor controlling the sonodegradation of halomethane mixtures. Increasing acoustic intensity enhanced the removal of halomethanes in chlorinated drinking water. In addition, ultrasonic irradiation led to a slightly decrease of pH and TOC of chlorinated drinking water.

Aqueous Cr(VI) photo-reduction catalyzed by TiO2 and sulfated TiO2.

TiO(2) and sulfated TiO(2) (SO(4)(2-)/TiO(2)) catalysts with different textural properties were prepared under different calcination temperatures and the photo-reduction of Cr(VI) to Cr(III) catalyzed by these catalysts was investigated. For the photocatalytic reduction of Cr(VI), the photocatalytic activities of the TiO(2) samples were found to be strongly dependent of the calcination temperature and TiO(2) calcined at 400 degrees C showed a higher catalytic activity compared to other TiO(2) catalysts. In contrast, sulfation of TiO(2) stabilized the catalytic activities of SO(4)(2-)/TiO(2) catalysts. At low calcination temperature, SO(4)(2-)/TiO(2) catalysts exhibited catalytic activities almost comparable with that of TiO(2) and the catalytic activities of SO(4)(2-)/TiO(2) catalysts were markedly higher than TiO(2) under high calcination temperature. In addition, the removal of surface SO(4)(2-) of SO(4)(2-)/TiO(2) catalyst led to a marked decrease of the catalytic activity for Cr(VI) photo-reduction, suggesting that the presence of surface SO(4)(2-) provided an acid environment over the catalyst surface and favored the photo-reduction of Cr(VI).

[Investigations on Sulfur and Carbon Isotopic Compositions of Potential Polluted Sources in Atmospheric PM2.5 in Nanjing Region].

Potential pollution sources of atmospheric PM2.5 in Nanjing region were collected, and sulfur and carbon isotopic compositions were determined by EA-IRMS synchronously. The results showed that δ³4S and δ¹³C values ranged from 1.8‰-3.7‰ and -25.50‰- -23.57‰ in coal soot particles; 4.6‰-9.7‰ and -26.32‰- -23.57‰ in vehicle exhaust; 5.2‰-9.9‰ and -19.30‰- -30.42‰ in straw soot particles, respectively. Besides, the δ¹³C value of dust was -13.45‰. It can be observed that sulfur isotopic compositions in coal soot were lower, while the carbon isotopic composition in dust was higher. Comparing with δ³4S and δ¹³C values in domestic and foreign polluted sources, we found that sulfur and carbon isotopes in atmospheric PM2.5 in Nanjing region presented an obvious regional characteristics. Therefore, the source spectrum of sulfur and carbon isotopic compositions in Nanjing region might provide an insight into source apportionment of atmospheric PM2.5.

[Nitrogen Removal and the Characteristics of Denitrification Bacteria Using NUA-DAS Ecofilter].

A small-scale combined ecofilter was constructed using neutralized-used acid residue (NUA) and dewatered alum sludge (DAS), and the nitrogen removal for wastewater treatment and characteristics of denitrification bacteria using the NUA-DAS ecofilter were studied. After the system was stabilized, the average removal rates of COD, TN, NO3--N in the final effluents were 60%, 70% and 95%, respectively, and the range of NO3--N concentration in the effluents was only 0.02-0.55 mg·L-1. Furthermore, the richness and similarity of three types of functional genes (nirS, nirK and nosZ) for denitrification in different substrates during the operation period were analyzed using PCR-DGGE method. These results showed that the richness of all denitrification bacteria at NUA and DAS increased remarkably after operation for 30 and 60 days compared to that in fresh substrate, and the richness was basically the same for the same kind of gene at the identical substrate regardless of depth gradient and operation period. The richness of nirS, nirK and nosZ detected in the NUA and DAS followed the order of nosZ > nirK > nirS. It was also revealed that spatial location had an apparent influence on the community structure of denitrifying bacteria (nirS, nirK and nosZ) but operation time had no obvious effect. Finally, nirK might be the most suitable for the environment in the system, and the adaptive capacity of denitrification bacteria (nirS, nirK and nosZ) in NUA could be superior to that in DAS.