Fast and eco-friendly synthesis of carbon dots from pinecone for highly effective detection of 2,4,6-trinitrophenol in environmental samples.

2,4,6-Trinitrophenol (TNP) has high explosive risks and biological toxicity, and there has been considerable concern over the determination of TNP. In the present work, fluorescent carbon dots (CDs) stemmed from a green carbon source of pinecone by the facile hydrothermal approach. A novel environment- friendly fluorescent probe was developed to efficiently detect TNP by using the obtained CDs with remarkable fluorescence stability. The fluorescent CDs exhibited obvious excitation dependence with the highest peaks for excitation and emission occurring at 321 and 411 nm, respectively. The fluorescence intensity is significantly reduced by TNP owing to the inner filter effect with the CDs. The probe exhibited good linearity with TNP concentrations in the range of 0.025-20 µg mL-1, and the limit of detection was as low as 8.5 ng mL-1. Additionally, the probe proved successful in sensing TNP quantitatively in actual environmental samples with satisfied recoveries of 95.6-99.6%. The developed fluorescent probe offered an environment-friendly, efficient, rapid, and reliable platform for detecting trace TNP in the environmental field.HighlightsNovel carbon dots were synthesised from green precursors of pineal powder.The highly effective quenching process was put down to the inner filter effect.The as-constructed fluorescent probe was successfully utilised for sensing 2,4,6-trinitrophenol in environmental samples.The proposed method was simple, rapid, efficient, economical, and eco-friendly.

[Pollution Characteristics, Source Apportionment, and Meteorological Response of Water-soluble Ions in PM2.5 in Xinxiang, North China].

Pollution variation, source characteristics, and meteorological effects of water-soluble inorganic ions (WSIIs) in PM2.5 were analyzed in Xinxiang city, Henan Province. PM2.5 samples and their chemical components were monitored online by using URG-9000 in four seasons:winter (January, 2022), spring (April, 2022), summer (July, 2022), and fall (October, 2022). The results showed that the TWSIIs had the same seasonal fluctuations as PM2.5. The average seasonal concentrations of WSIIs ranged from 19.62-72.15 µg·m-3, accounting for more than 60% of PM2.5, demonstrating that WSIIs were the major components of PM2.5. The annual concentration value of NO3-/SO42- was 2.11, which showed an increasing trend, suggesting predominantly mobile sources for secondary inorganic aerosols (SNA). Further, the molar concentration value [NH4+]/[NO3-] was 1.95, demonstrating that agriculture emissions were the dominant contributors to atmospheric nitrogen. Furthermore, the backward trajectory analysis showed that the concentrations of Ca2+ and Mg2+ were higher when the northeasterly wind prevailed and the wind speed was high. High values of SOR and NOR were correlated with low temperatures and high relative humidity (T < 8℃, RH > 60%), demonstrating that more gaseous precursors were converted into sulfate and nitrate. At high temperatures (T > 24℃), there was no apparent high NOR value like that for SOR, mainly due to the decomposition of NH4NO3 at high temperatures. Finally, backward trajectories associated with the PMF-resolved results were used to explore the regional transport characteristics. The results illustrated that dust sources in the study areas were mainly influenced by air trajectories originating from the northwest regions, whereas secondary sulfate, secondary nitrate, and biomass sources contributed more to WSIIs when wind speed and altitude air masses were low in the area surrounding the observation site.

Fast and efficient "on-off-on" fluorescent sensor from N-doped carbon dots for detection of mercury and iodine ions in environmental water.

A kind of nitrogen doped carbon dots (N-CDs) was facilely fabricated from polyethyleneimine and anhydrous citric acid, and which was adopted to develop a neoteric "on-off" and "off-on" fluorescent sensor for rapidly and efficiently sensing Hg2+ and I-. The fluorescence of N-CDs was notably quenched (off) in the existence of Hg2+ derived from strong interaction and the electron transfer between N-CDs and Hg2+, while the quenched fluorescence of the N-CDs and Hg2+ system was strikingly regained by addition of I- (on) resulted from the separation of N-CDs and Hg2+ due to the higher binding preference between Hg2+ and I-. Under optimal conditions, the linear detection ranges were 0.01-20 µM for Hg2+ and 0.025-7 µM for I-, respectively. Meanwhile, the detection limits could be down to 3.3 nM for Hg2+ and 8.5 nM for I-, respectively. Satisfied recoveries had also been gained for measuring Hg2+ and I- in practical water samples. The constructed "on-off-on" fluorescent sensor provided a simple, rapid, robust and reliable platform for detecting Hg2+ and I- in environmental applications.

[Seasonal Variation, Source Identification, and Health Risk of PM2.5-bound Metals in Xinxiang].

This study analyzed the seasonal variation, sources, and source-specific health risks of PM2.5-bound metals in Xinxiang city, Henan province. A total of 112 daily PM2.5 samples were collected over four consecutive seasons during 2019-2020. In total, 19 elements were identified using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The annual concentrations of PM2.5 and 11 heavy metals were calculated to be (66.25±35.73) µg·m-3 and (1.32±0.84) µg·m-3, respectively. Strong seasonal variations were observed in PM2.5 concentrations and the concentrations of associated metal elements, with the lowest concentrations all occurring in summer. The highest concentrations of dust-related elements (e.g., Al, Ca, Fe, Mg,and Ti) were recorded in spring, differing significantly from other elements, which all exhibited the highest mass concentrations in winter. The results apportioned from positive matrix factorization (PMF) and potential source contribution function (PSCF) models showed that the major sources of PM2.5-bound elements were Ni-and Co-related emissions (5.8%), motor vehicles (13.7%), Cd-related emissions(5.1%), combustion emissions (18.2%), and dust (57.3%). Health risk models showed that there were no obvious non-carcinogenic risks associated with these metals, because their hazard quotient (HQ) values were all below 1. Lifetime carcinogenic risks of the five apportioned sources were all higher than the acceptable level (1×10-6). Of these five sources, combustion emissions were the largest contributors to cancer risk (8.74×10-6, 36.9%) and non-cancer risk (0.60, 25.6%). This study suggests that control strategies to mitigate exposure risk in Xinxiang should emphasize reducing the sources of combustion emissions.

Green preparation of carbon dots from Momordica charantia L. for rapid and effective sensing of p-aminoazobenzene in environmental samples.

p-Aminoazobenzene (pAAB) is a hazardous azo dye that causes considerable harm to human health and the environment. The development of novel and sensitive sensors for the rapid detection of pAAB is in high demand. In this study, a simple fluorescent sensor for pAAB detection is designed based on carbon dots (CDs) which are prepared using green carbon source of Momordica charantia L. via a facile hydrothermal approach. The fluorescence spectra of CDs exhibit considerable overlap with the absorption band of pAAB, and the fluorescence is specifically suppressed in the presence of pAAB ascribed to the inner filter effect. Good and wide linearity is observed in the pAAB concentration range of 0.01-12.5 µg mL-1 with a lower detection limit of 3.9 ng mL-1. The established method achieves good results with a rapid analysis of pAAB in different practical water and soil samples. The as-constructed fluorescent sensor provides a simple, rapid, economical and eco-friendly platform and possesses prospective applications for the effective, selective and sensitive detection of pAAB in the environmental field.

Temporal variation characteristics and source apportionment of metal elements in PM2.5 in urban Beijing during 2018-2019.

To explore high-resolution temporal variation characteristics of atmospheric metal elements concentration and more accurate pollution sources apportionment, online monitoring of metal elements in PM2.5 with 1-h time resolution was conducted in Beijing from August 22, 2018 to August 21, 2019. Concentration of 18 elements varied between detection limit (ranging from 0.1 to 100 ng/m3) and nearly 25 µg/m3. Si, Fe, Ca, K and Al represented major elements and accounted for 93.47% of total concentration during the study period. Compared with previous studies, airborne metal pollution in Beijing has improved significantly which thanks to strict comprehensive control measures under the Clean Air Action Plan since 2013. Almost all elements present higher concentrations on weekdays than weekends, while concentrations of elements associated with dust sources during holidays are higher than those in working days after the morning peak, and there is almost no concentration difference in the evening peak period. Soil and dust, vehicle non-exhaust emissions, biomass, industrial processes and fuel combustion were apportioned as main sources of atmospheric metal pollution, accounting for 63.6%, 18.4%, 16.8%, 1.0% and 0.18%, respectively. Furthermore, main occurrence season of metal pollution is judged by characteristic radar chart of varied metal elements proposed for the first time in this study, for example, fuel combustion type pollution mainly occurs in winter and spring. Results of 72-h backward trajectory analysis of air masses showed that, except for local emissions, atmospheric metal pollution in Beijing is also affected by regional transport from Inner Mongolia, Hebei, the Bohai Sea and Heilongjiang.

Seasonal variations in the mass characteristics and optical properties of carbonaceous constituents of PM2.5 in six cities of North China.

Carbonaceous constituents have various adverse impacts on human health, visibility, and climate change. Although comprehensive studies on the characteristics of carbonaceous constituents have been conducted recently, systematic studies covering both the mass characteristics and light-absorption properties of carbonaceous constituents on a regional scale in China are quite limited. In this study, current seasonal measurements of organic carbon (OC) and elemental carbon (EC) in PM2.5 were investigated during autumn and winter (1-30 October 2017 and December 18, 2017 to January 17, 2018) in six selected cities located at the eastern foot of the Taihang Mountains: Beijing, Baoding, Shijiazhuang, Handan, Xinxiang, and Zhengzhou. Seasonal variations were similar when Beijing was excluded. The lowest concentrations of OC (18.33 ± 9.39 µg/m3) and EC (7.66 ± 5.64 µg/m3) were observed in Xinxiang (autumn) and Beijing (winter), respectively, while the highest concentrations of OC (38.43 ± 62.10 µg/m3) and EC (12.24 ± 24.67 µg/m3) occurred in Baoding during winter mainly due to elevated fuel combustion for space heating. The results of the potential source contribution function (PSCF) analysis suggested that border zones between several provinces in North China should be highlighted in order to strengthen pollution control. Moreover, by separating the optical properties of brown carbon from those of black carbon, we were able to estimate the contributions of brown carbon to the PM2.5 total light-absorption coefficient. The results show that the brown carbon absorption coefficient (at 405 nm) in winter at six sites accounted for 21.2%, 33.3%, 34.7%, 39.1%, 48.6%, and 23.3% of the PM2.5 light absorption, which are values that are comparable to the contribution of black carbon in Xinxiang. These results provide a more comprehensive understanding of carbonaceous constituents on a regional scale.

Fine particulate matter pollution in North China: Seasonal-spatial variations, source apportionment, sector and regional transport contributions.

Large areas of mainland China have been suffering frequently from heavy haze pollution during the past years, which feature high concentrations of fine particulate matter (PM2.5, particulate matters with aerodynamic diameters less than 2.5 µm) and low visibility. Moreover, these areas manifested strong regional complex pollution characteristics, particularly in North China including Beijing and the five surrounding provinces (BSFP). In this study, by using the localized comprehensive emission inventory of BSFP region in 2012 as an input, the Comprehensive Air Quality Model with Extensions-Particulate Matter Source Apportionment Technology (CAMx/PSAT) was used to assess the seasonal variations and source apportionment of PM2.5 in the highly polluted BSFP region, with a specific focus on the sectoral and sub-regional contributions to PM2.5 in Beijing during winter and summer. Results showed that the PM2.5 concentrations of BSFP region was higher in winter than that in summer. And the heavily polluted area in BSFP region shrinked noticeably in summer, compared with winter. As for source apportionment of PM2.5, residential and remaining industrial sectors constituted the top two sources of PM2.5 mass concentrations in Beijing. In addition, agricultural source represented a major contributor to ammonium, whereas transportation and power sectors constituted major sources to nitrates. In terms of contributions from sub-regions, the local sources ranked as the dominant contributors to PM2.5 in Beijing, while the main external contributions originated from the surrounding areas, such as Hebei and Shandong. Results of daily source apportionment to PM2.5 in Beijing showed that sub-regional long-distance transport became stronger when haze pollution was severe, in which contribution from remaining industrial sector would be higher than that of other periods. The results will allow for an improved understanding of the causes and origins of heavy regional PM2.5 pollution, and thus will benefit the development of effective joint control policies and identification of key polluting emission categories in North China and ultimately serve as references for other highly polluted megacities in the world.

A quantitative assessment of atmospheric emissions and spatial distribution of trace elements from natural sources in China.

Natural sources, such as soil and wind-erosion dust (SWD), biomass open burning (BOB), sea salt spray (SSAS) and biogenic source (BIO), are major contributors to atmospheric emissions of trace elements (TEs) globally. In this study, we used a comprehensive approach to account for area-, production- and biofuel consumption-based emission factor calculation methods, and thus developed an integrated high-resolution emission inventory for 15 types of TEs (As, B, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, V and Zn) originated from natural sources in China for the year 2015. The results show that national emissions of TEs in 2015 range from 7.45 tons (Hg) to 1, 400 tons (Zn) except for the extremely high emissions of Mn (10, 677 tons). SWD and BIO are identified as the top two source contributors, accounting for approximately 67.7% and 26.1% of the total emissions, respectively. Absolute emissions of TEs from natural sources are high in the Xinjiang, Inner Mongolia and Tibet autonomous regions with large areas of bare soil and desert. However, emission intensity of TEs per unit area in the Southern provinces of China is higher than those in Northern China and Southwestern China, with the Yunnan and Sichuan provinces displaying the highest emission intensity. Our results suggest that controlling SWD can play a significant role in reducing fugitive particulate matter and the associated emissions of TEs from natural sources in China; and desertification control is particularly critical in the Northwest provinces where the majority of deserts are located.

Migration and Emission Characteristics of Ammonia/Ammonium through Flue Gas Cleaning Devices in Coal-Fired Power Plants of China.

To investigate the up-to-date migration and emission characteristics of NH3/NH4+ in coal-fired power plants (CFPPs) after implementing ultralow emission retrofitting, typical air pollution control devices (APCDs) in CFPPs, including flue gas denitrification, dust collectors, combined wet flue gas desulfurization (WFGD), and wet precipitators are involved in field measurements. The results show that most of the excessive injected and/or unreacted ammonia from the flue gas denitrification system, whether selective catalytic reduction (SCR) or selective noncatalytic reduction (SNCR), is converted into particle-bound NH4+ (>91%), and the rest (less than 9%) is carried by flue gas in the form of gaseous NH3, with a concentration value of 0.15-0.54 mg/(N m3) at the denitrification outlet. When passing through dust collectors, particle-bound NH4+ concentration decreases substantially along with the removal of particle matter. In WFGD, the dissolution and volatilization effects affect the gaseous ammonia concentration, which decreases when using limestone slurry and a 20% solution of ammonia as a desulfurization agent, while liquid ammonia solution with a high concentration (99.8%) may cause the flue gas NH3 concentration to increase considerably by 13 times. Particle-bound NH4+ concentration is mainly influenced by the relative strength of desulfurization slurry scouring and flue gas carrying effects and increases 2.84-116 times through ammonia-based WFGD. Furthermore, emission factors of NH3 for combinations of APCDs are discussed.

Seasonal variation, formation mechanisms and potential sources of PM2.5 in two typical cities in the Central Plains Urban Agglomeration, China.

In order to probe the seasonal variation, formation mechanisms as well as geographical origins of fine particles and its chemical components in two cities (Zhengzhou, ZZ and Xinxiang, XX) in Central Plains Urban Agglomeration, daily PM2.5 aerosol samples were collected for four consecutive seasons during 2017-2018. The annual average concentrations of PM2.5 (particulate matter with an aerodynamic diameter smaller than 2.5 µm) were calculated at 70.5 ±â€¯50.8 and 69.0 ±â€¯46.3 µg m-3 at ZZ and XX, respectively. Daily ambient PM2.5 concentrations ranged from 18.2 to 303.0 µg m-3, among which >81% of the total sampling days exceeded the National Ambient Air Quality Standard of China (NAAQS, 35 µg m-3 as an annual average). Additionally, concentrations of PM2.5 and its major chemical components were seasonally dependent, usually with the highest mass concentration in winter. Compared with previous studies, higher NO3-/SO42- were observed in this study depicted that air pollution caused by motor vehicle exhaust cannot be ignored. OC concentration was higher at ZZ than XX during sampling campaign likely partially caused by larger number of motor vehicles, chemical pesticide and solvent used in ZZ. Both homogeneous and heterogeneous reactions played an important role in the formation of nitrate, while heterogeneous reactions dominated the formation of sulfate. We also found a faster increase in nitrate than in sulfate during the evolution of haze. The characteristics of long-range transportation of PM2.5 and its major chemical components and gaseous precursors were observed at both sites through back trajectories and WPSCF analysis, suggesting the complexity of air pollution and the multi-influence among cities.

Atmospheric emission inventory of multiple pollutants from civil aviation in China: Temporal trend, spatial distribution characteristics and emission features analysis.

A detailed comprehensive emission inventory of multiple air pollutants from civil aviation in China for the historical period of 1980-2015 is developed by using an approach of combining bottom-up with top-down for the first time. Annual emissions of various pollutants present a rapidly ascending trend along with the increase of economic volume and population, which are estimated at approximately 4.77 kt HC, 59.63 kt CO, 304.77 kt NOx, 59,961 kt CO2, 19.04 kt SO2, 3.32 kt PM2.5, 1.59 kt BC, 1.06 kt OC and 5.44 t heavy metals (HMs), respectively, by the year 2015. We estimate the local emissions in 208 domestic civil airports and allocate the total cruise emissions onto 299 main domestic flight segments with surrogate indexes, such as route distance, cargo and passenger turnover. The results demonstrate that emission intensities in central and eastern China are much higher than those in northeastern and western China, and these regions are characterized with high population density, huge economy volume, as well as transit convenience. Furthermore, we have explored emission characteristics of multiple pollutants under different operation modes in 2015. For PM2.5, SO2/CO2/HMs and NOx, the emissions from cruise process constitute the dominant contributor with a share of 89%, 92% and 81%, of the associated total emissions, respectively, comparing with 76% and 71% of the total CO and HC emissions release from Landing and Take-off (LTO) process. Consequently, there are notably different emission characteristics from different flight processes due to various combustion status of aviation fuel. In addition, we predict the future trends of multi-pollutants emissions from China's civil aviation industry through 2050 under three scenarios, and the results indicate that the reduction from the improvement of new technology or new national standards would be largely offset by the rise in multi-pollutants emissions from rapidly aviation fuel growth.

Effects of Wet Flue Gas Desulfurization and Wet Electrostatic Precipitators on Emission Characteristics of Particulate Matter and Its Ionic Compositions from Four 300 MW Level Ultralow Coal-Fired Power Plants.

To achieve ultralow-emission (ULE) standards, wet electrostatic precipitators (WESP) installed downstream from wet flue gas desulfurization (WFGD) have been widely used in Chinese coal-fired power plants (CFPPs). We conducted a comprehensive field test study at four 300 MW level ULE CFPPs, to explore the impact of wet clean processing (WFGD and WESP) on emission characteristics of three size fractions of particulate matter (PM: PM2.5, PM10-2.5, and PM>10) and their ionic compositions. All these CFPPs are installed with limestone-based/magnesium-based WFGD and followed by WESP as the end control device. Our results indicate that particle size distribution, mass concentration of PM, and ionic compositions in flue gas change significantly after passing WFGD and WESP. PM mass concentrations through WFGD are significantly affected by the relative strength between desulfur slurry scouring and flue gas carrying effects. Concentrations of ions in PM increase greatly after passing WFGD; especially, SO42- in PM2.5, PM10-2.5, and PM>10 increase on average by about 1.4, 3.9, and 8.3 times, respectively. However, WESP before the stack can effectively reduce final PM emissions and their major ionic compositions. Furthermore, emission factors (kg/(t of coal)) of PM for different combinations of air pollution control devices are presented and discussed.

Spatial-temporal variation characteristics of air pollution in Henan of China: Localized emission inventory, WRF/Chem simulations and potential source contribution analysis.

Henan is the most populous province and one of the most seriously polluted areas in China at present. In this study, we establish an integrated atmospheric emission inventory of primary air pollutants in Henan province for the target year of 2012. The inventory developed here accounts for detailed activity levels of 11 categories of primary anthropogenic emission sources, and determines the best available representation of emission factors. Further, we allocate the annual emissions into a high spatial resolution of 3km×3km with ArcGIS methodology and surrogate indices, such as regional population distribution and gross domestic product (GDP). Our results show that the emissions of VOCs, SO2, PM10, PM2.5, NOX, NH3, CO, BC and OC are about 1.15, 1.24, 1.29, 0.70, 1.93, 1.05, 7.92, 0.27 and 0.25milliontons, respectively. The majority of these pollutant emissions comes from the Central Plain Urban Agglomeration (CPUA) region, particularly Zhengzhou and Pingdingshan. By combining with the emission inventory with the WRF/Chem modeling and backward trajectory analysis, we investigate the temporal and spatial variability of air pollution in the province and explore the causes of higher pollutants concentrations in the region of CPUA during the heavily polluted period of January. The results demonstrate that intensive pollutants emissions and unfavorable meteorological conditions are the main causes of the heavy pollution. Besides, Weighted Potential Source Contribution Function (WPSCF) analysis indicates that local emissions remain the major contributor of PM2.5 in Henan province, although emissions from the neighboring provinces (e.g. Shanxi, Shaanxi, Anhui, and Shandong) are also important contributors.

Temporal-spatial characteristics and source apportionment of PM2.5 as well as its associated chemical species in the Beijing-Tianjin-Hebei region of China.

PM2.5 and its major chemical compositions were sampled and analyzed in January, April, July and October of 2014 at Beijing (BJ), Tianjin (TJ), Langfang (LF) and Baoding (BD) in order to probe the temporal and spatial characteristics as well as source apportionment of PM2.5 in the Beijing-Tianjin-Hebei (BTH) region. The results showed that PM2.5 pollution was severe in the BTH region. The average annual concentrations of PM2.5 at four sampling sites were in the range of 126-180 µg/m3, with more than 95% of sampling days exceeding 35 µg/m3, the limit ceiling of average annual concentration of PM2.5 regulated in the Chinese National Ambient Air Quality Standards (GB3095-2012). Additionally, concentrations of PM2.5 and its major chemical species were seasonally dependent and demonstrated spatially similar variation characteristics in the BTH region. Concentration of toxic heavy metals, such as As, Cd, Cr, Cu, Mn, Ni, Pb, Sb, Se, and Zn, were higher in winter and autumn. Secondary inorganic ions (SO42-, NO3-, and NH4+) were the three-major water-soluble inorganic ions (WSIIs) of PM2.5 and their mass ratios to PM2.5 were higher in summer and autumn. The organic carbon (OC) and elemental carbon (EC) concentrations were lower in spring and summer than in autumn and winter. Five factors were selected in Positive Matrix Factorization (PMF) model analysis, and the results showed that PM2.5 pollution was dominated by vehicle emissions in Beijing, combustion emissions including coal burning and biomass combustion in Langfang and Baoding, and soil and construction dust emissions in Tianjin, respectively. The air mass that were derived from the south and southeast local areas around BTH regions reflected the features of short-distant and small-scale air transport. Shandong, Henan, and Hebei were identified the major potential sources-areas of secondary aerosol emissions to PM2.5.