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The optical and microphysical properties of aerosols remain one of the greatest uncertainties associated with evaluating the climate forcing attributed to aerosols. Although the trends in aerosol optical depth (AOD) at global and regional scales have been widely examined, little attention has been paid to the trends in type-dependent AODs related to aerosol particle properties. Here, using the aerosol optical component dataset from the Multi-angle Imaging SpectroRadiometer (MISR) instrument, we investigate decadal-scale trends in total aerosol loading as well as AODs for five aerosol components by particle size and morphology during 2003–2018 over land. Relationships between the total AOD (TAOD) trends and type-dependent AOD changes were examined, and the relative contribution of each type-dependent AOD to the overall TAOD trends was quantified. By dividing the TAOD values into four different aerosol pollution levels (APLs) with splits at 0.15, 0.40, and 0.80, we further explored the relationships between TAOD changes and interannual variations in the frequency-of-occurrences (FoOs) of these APLs. Long-term trends in FoOs in the different APLs show that there was a significant improvement in air quality between 2003 and 2018 in most land areas, except South Asia, corresponding to a shift from lightly polluted to clean conditions. However, the effects of different APLs on TAOD changes are regionally dependent and their extent of correlation varied spatially. Moreover, we observed that the annual mean TAOD has decreased by 0.47% a−1 over land since 2003 (P

The high density and poor thermal insulation of traditional wood-plastic composites limited the application in the field of building materials. In this paper, wood fiber (WF) and PLA were used as raw materials and azodicarbonamide was used as the foaming agent. Lightweight WF/PLA composites were prepared by the hot-pressing foaming method, aiming to obtain renewable, low-density material with high strength-to-weight ratio and thermal insulation performance. The results showed that after adding 20 % WF into PLA, the cell morphology was excellent and the cell size was uniform. The magnification reached the minimum value of 0.36 g/cm

The development of appropriate analytical screening techniques for pharmaceuticals and personal care products (PPCPs) is the basis for studying the distribution and environmental impact of emerging contaminants (ECs). Mass spectrometry-based screening methods vary with the complexity of the target compounds. It is challenging to balance both positive and negative ion quantification with a low detection limit. To establish a set of experimental methods including extraction, chromatography-separation and mass spectrometry screening is one of the most important topics in PPCP research. This paper describes a universal and efficient qualification and quantification protocol for the simultaneous detection of 34 PPCPs in different environmental samples in a single analytical data acquisition run.Thirty-four representative PPCPs, which are widely distributed in the environment with high ecological toxicity and complex chemical structures, were selected as representative target ECs. The extraction of the target PPCPs was achieved using only one solid-phase extraction cartridge without the need to adjust the pH of samples. The enriched samples were detected by LC-MS/MS in both positive and negative ion modes simultaneously. The protocol was evaluated based on the accuracy, precision, detection limits and matrix effects.This method achieved simultaneous detection of PPCPs in both positive and negative ion modes, with a single analytical cycle of 12 min. The observed SPE recoveries were between 40% and 115%. The instrumental detection limits (IDL) varied from 0.01 to 1 pg, and the method detection limits (MDL) were between 0.002 and 3.323 ng/l in different matrices. Most of the PPCPs were subjected to matrix suppression below 30%. The method was successfully applied for quantitative analysis of the PPCPs in different environmental samples, including river samples, wastewater treatment plant (WWTP) samples and soil samples.This protocol developed a rapid and efficient detection method to simultaneous qualitative and quantitative 34 representative PPCPs in the environment. The IDL ranged from 0.01 to 1 pg and the MDL ranged from 0.002 to 3.323 ng/l in different matrices. The detection limit was one order of magnitude lower compared to previous studies. The protocol also provided a wide application range for different environmental matrices, which permitted the migration and transformation of PPCPs to be explored.

Notable warming trends have been observed in the Arctic, with tropospheric aerosols being one of the key drivers. Here the seasonal cycles of three-dimensional (3D) distributions of aerosol extinction coefficients (AECs) and frequency of occurrences (FoOs) for different aerosol subtypes in the troposphere over the Arctic from 2007 to 2019 are characterized capitalizing on Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) Level-3 gridded aerosol profile product. Seasonal contributions of total and type-dependent aerosols through their partitioning within the planetary boundary layer (PBL) and free troposphere (FT) are also quantified utilizing the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) PBL height data. The results show substantial seasonal and geographical dependence in the distribution of aerosols over the Arctic. Sulfate, black carbon (BC), and organic carbon (OC) contribute most of the total AEC, with Eurasia being the largest contributor. The vertical structure of AECs and FoOs over the Arctic demonstrates that the vertical influence of aerosols is higher in eastern Siberia and North America than in northern Eurasia and its coasts. When the total aerosol optical depth (TAOD) is partitioned into the PBL and FT, results indicate that the contributions of TAOD within the FT tend to be more significant, especially in summer, with the FT contributes 64.2% and 69.2% of TAOD over the lower (i.e., 60° N-70° N) and high (i.e., north of 70° N) Arctic, respectively. Additionally, seasonal trend analyses suggest Arctic TAOD exhibits a multi-year negative trend in winter, spring, and autumn and a positive trend in summer during 2007-2019, due to an overall decrease in sulfate from weakened anthropogenic emissions and a significant increase in BC and OC from enhanced biomass burning activities. Overall, this study has potential implications for understanding the seasonal cycles and trends in Arctic aerosols.

Although a remarkable reduction in the frequency of sand and dust storms (SDSs) in the past several decades has been reported over northern China (NC), two unexpected mega SDSs occurred on 15–20 and 27–29 March 2021 (abbreviated as the “3.15” and “3.27” SDS events), which has reawakened widespread concern. This study characterizes the optical, microphysical, and radiative properties of aerosols and their meteorological drivers during these two SDS events using the Sun photometer observations in Beijing and a comprehensive set of multiple satellite (including MODIS, VIIRS, CALIOP, and Himawari-8) and ground-based observations (including the CMA visibility network and AD-Net) combined with atmospheric reanalysis data. Moreover, a long-term (2000–2021) dust optical depth (DOD) dataset retrieved from MODIS measurements was also utilized to evaluate the historical ranking of the dust loading in NC during dust events. During the 3.15 and 3.27 events, the invasion of dust plumes greatly degraded the visibility over large areas of NC, with extreme low visibility of 50 and 500 m recorded at most sites on 15 and 28 March, respectively. Despite the shorter duration of the 3.27 event relative to the 3.15 event, sun photometer and satellite observations in Beijing recorded a larger peak AOD (∼2.5) in the former than in the latter (∼2.0), which was mainly attributed to the short-term intrusion of coarse-mode dust particles with larger effective radii (∼1.9 µm) and volume concentrations (∼2.0 µm3 µm−2) during the 3.27 event. The shortwave direct aerosol radiative forcing induced by dust was estimated to be −92.1 and −111.4 W m−2 at the top of the atmosphere, −184.7 and −296.2 W m−2 at the surface, and +92.6 and +184.8 W m−2 in the atmosphere in Beijing during the 3.15 and 3.27 events, respectively. CALIOP observations show that during the 3.15 event the dust plume was lifted to an altitude of 4–8 km, and its range of impact extended from the dust source to the eastern coast of China. In contrast, the lifting height of the dust plume during the 3.27 event was lower than that during the 3.15 event, which was also confirmed by ground-based lidar observations. The MODIS-retrieved DOD data registered these two massive SDS events as the most intense episode in the same period in history over the past 2 decades. These two extreme SDS events were associated with both atmospheric circulation extremes and local meteorological anomalies that favored enhanced dust emissions in the Gobi Desert (GD) across southern Mongolia and NC. Meteorological analysis revealed that both SDS events were triggered by an exceptionally strong Mongolian cyclone generated at nearly the same location (along the central and eastern plateau of Inner Mongolia) in conjunction with a surface-level cold high-pressure system at the rear, albeit with differences in magnitude and spatial extent of impact. In the GD, the early melting of spring snow caused by near-surface temperature anomalies over dust source regions, together with negative soil moisture anomalies induced by decreased precipitation, formed drier and barer soil surfaces, which allowed for increased emissions of dust into the atmosphere by strongly enhanced surface winds generated by the Mongolian cyclone.

Chromium (Cr(VI)) pollution poses a serious threat to the ecological environment and biological health; therefore, there is an urgent need to develop advanced technologies for Cr(VI) detection and removal. Here, a novel fluorescent wood sponge (citric acid modified wood sponge decorated with carbon dots, CA/WS-CDs) was constructed combining hierarchical porous wood sponge (WS) and carbon dots (CDs) via chemical bonding, which could simultaneously detect and remove hexavalent Cr(VI) in an aqueous medium. The chemical and physical structure of the fluorescent wood sponge was characterized, and its detection and adsorption performances for Cr(VI) were studied. The results demonstrated that the CA/WS-CDs showed excellent performance for Cr(VI) detection and removal. After being immersed in a Cr(VI) solution (50 mL, 50 mg L−1) at 25 °C for 24 h, the strong blue fluorescence of CA/WS-CDs-3 under 365 nm light weakened and fluorescence quenching started to occur, which makes the fluorescent wood sponge a detector of Cr(VI). Moreover, this novel fluorescent wood sponge had a higher adsorption ability for Cr(VI) (maximum adsorption capacity, 450.5 mg g−1), and its sorption performance met Langmuir and pseudo-second-order models. Furthermore, FTIR and XPS analysis confirmed that the hierarchical structure of the fluorescent wood sponge provided many effective sorption sites and ion transport channels, thereby guaranteeing the selective detection and efficient adsorption properties for Cr(VI). Such intriguing Cr(VI) warning and sorption performance make the proposed CA/WS-CDs hold huge prospects for practical environmental remediation.

Feedstock recovery plays a crucial role in the further application of polylactic acid (PLA), yet it still lacks efficient ways, resulting from an unclear understanding of PLA pyrolysis. Hence, the co-pyrolysis of PLA and the major components of biomass additives cellulose, hemicellulose and lignin was carried out to enhance the feedstock lactide yield and explore the pyrolysis mechanism. Compared to cellulose/PLA and hemicellulose/PLA, the co-pyrolysis of lignin/PLA had the strongest synergistic effects. Based on in situ FTIR and Py-GC/MS, the promoting mechanism was as follows: 4-ethyl-2-methoxy-phenol produced by the pyrolysis of lignin provided additional free radicals for the free radical reaction of PLA so that the production of lactide increased by 162.8%. The activation energy of co-pyrolysis was 30.6% and 13.8% lower than those of lignin and PLA, respectively, which was also due to the fact that lignin promoted the free radical reaction of PLA. It was indicated that co-pyrolysis required less energy than that of single pyrolysis. In addition, the generated lactide was not well-compatible with other bio-oils and solidified at room temperature, so it could be recycled by simple physical separation. This work provided a new method for the reuse of large amounts of waste PLA and lignin waste such as papermaking black liquor.

The Hunga Tonga-Hunga Ha'apai eruption on January 15, 2022 was one of the most explosive volcanic eruptions of the 21st century and has attracted global attention. Here we show that large numbers of the volcanic aerosols from the eruption broke through the tropopause into the lower stratosphere, forming an ash plume with an overshooting top at 25-30 km altitude. In the four days following the eruption, the ash plume moved rapidly westward for nearly 10,000 km under stable stratospheric conditions characterized by strong tropical easterlies, weak meridional winds and weak vertical motion. The intrusion of the ash plume into the stratosphere resulted in a marked increase in atmospheric aerosol loading across northern Australia, with the aerosol optical depth (AOD) observed by satellites and sun-photometers peaking at 1.5 off the coast of northeastern Australia; these effects lasted for nearly three days. The ash plume was characterized by fine-mode particles clustered at a radius of about 0.26 µm, with an observed peak volume of 0.25 µm

East Asian dust aerosols play a vital role in the local and regional climate through its direct, indirect, and semidirect effects, but the dominant factors affecting the interannual variation of dust aerosols over East Asia and their regional differences remain unclear. This study verified the accuracy of MEERA-2 dust data in East Asia, analyzed the interannual trends of dust in East Asia from 2000 to 2019 using the MERRA-2 dust column mass density (DCMD) and identified the dominant factors affecting the interannual variation during the dusty season (March–July) by developing the regional multiple linear regression models, combined with correlation and partial correlation analysis. The comparison with the dust index (DI) calculated from ground-based observations of dust events frequency indicated that MERRA-2 DCMD exhibited high spatial agreement (R > 0.8) with ground-based observations in most regions (especially in the dust source region of North China). The trend analysis revealed that DCMD in East Asia decreased significantly after 2000, particularly in the dusty season (March–July). These significant decreases were generally highly correlated with increases in normalized differential vegetation index (NDVI), volumetric soil moisture (VSM), and precipitation (PPT) and with decreases in wind speed (WS). Furthermore, WS dominated the interannual variation in the dust concentration over the East Asian dust source regions and their downstream. By contrast, PPT, through its wet deposition effect, dominated the variation in the rest of the regions away from the dust source regions. The study findings may help clarify the associations between local meteorological and surface factors and long-term variations in dust aerosols over East Asia.

Frequent oil-spill accidents have posed serious threats to ecosystem balance and the efficiency of resources use. Hydrophobic adsorbents that can adsorb and recover oil without causing secondary pollution are ideal candidates for the remediation of oil contamination in water. However, these composites are inefficient for crude oil-spills cleanup because crude oil has low liquidity of at room temperature. Increasing the temperature can effectively enhance the flowability of crude oil. To achieve efficient crude-oil heating and removal in situ, wood aerogels were immersed in Ti

Although a remarkable reduction in the frequency of sand and dust storms (SDSs) in the past several decades has been reported over northern China (NC), two unexpected mega SDSs occurred on March 15–20, 2021 and March 27–29, 2021 (abbreviated as the “3.15” and “3.27” SDS events), which has reawakened widespread concern. This study characterizes the origins, transport processes, magnitudes of impact, and meteorological causes of these two SDS events using a long-term (2000–2021) dust optical depth (DOD) dataset retrieved from MODIS measurements and a comprehensive set of multiple satellite and ground-based observations combined with atmospheric reanalysis data. During the 3.15/3.27 event, the invasion of dust plumes greatly degraded the air quality over large areas of NC, reaching extremely hazardous levels, with the maximum daily mean PM10 concentration of 7058 µg m−3 (2670 µg m−3) recorded on March 15 (28). CALIOP observations show that during the 3.15 event the dust plume was lifted to an altitude of 4–8 km, and its range of impact extended from the dust source to the eastern coast of China. In contrast, the lifting height of the dust plume during the 3.27 event was lower than that during 3.15 event, which was also confirmed by ground-based Lidar observations. The MODIS-retrieved DOD data registered these two massive SDS events as the most intense episode in the same period in history over the past two decades. These two extreme SDS events were associated with both atmospheric circulation extremes and local meteorological anomalies that favored enhanced dust emissions in the Gobi Desert (GD) across southern Mongolia and NC. Meteorological analysis revealed that both SDS events were triggered by an exceptionally strong Mongolian cyclone generated at nearly the same location (along the central and eastern plateau of Inner Mongolia) in conjunction with a surface-level cold high-pressure system at the rear, albeit with differences in magnitude and spatial extent of impact. In the GD, the early melting of spring snow caused by near-surface temperature anomalies over dust source regions, together with negative soil moisture anomalies induced by decreased precipitation, formed drier and barer soil surfaces, which allowed for increased emissions of dust into the atmosphere by strongly enhanced surface winds generated by the Mongolian cyclone.

Globally gridded aerosol extinction data from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) during 2007–2019 are utilized to investigate the three-dimensional (3D) climatological distribution of tropospheric type-dependent aerosols, and to identify the trends in column aerosol optical depth (AOD), partitioned within different altitude regimes, and their meteorological drivers. Using detection samples of layer aerosols, we also yield a 3D distribution of the frequency-of-occurrence (FoO) of aerosol sub-types classified by CALIOP. The results show that the aerosol extinction coefficient (AEC) shows contrasting vertical distribution patterns over land and ocean, with the former possessing significant geographical dependence, while the enhancement of AEC in the latter is mainly located below 1 km. The vertical structures of the type-dependent AECs, however, are strongly dependent on altitude. When the total AOD (TAOD) is partitioned into the planetary boundary layer (PBL) and the free troposphere (FT), results demonstrate that the PBL and FT contribute 61.86 % and 38.13 %, respectively, of the global tropospheric TAOD averaged over daytime and nighttime. Yet, this CALIOP-based partitioning of the different aerosol sub-types in the PBL and FT varies significantly. Among all 12 typical regions of interest analyzed, more than 50 % of TAOD is located in the lower troposphere (0–2 km), while the contribution is less than 2 % above 6 km. In global average terms, we found the aerosol FoO averaged over all layers is 4.45 %, with the largest contribution from ‘clean marine’ (1.79 %) and the smallest from ‘clean continental’ (0.05 %). Overall, the FoO vertical structures of the aerosol layer exhibit a distribution pattern similar to that of AEC. The resulting trend analyses show that CALIOP accurately captures significant regional anomalies in TAOD, as observed in other satellite measurements and aerosol reanalysis. Our correlation analysis between meteorological factors and TAOD suggests the interannual variability of TAOD is related to the variability of precipitation (PPT), volumetric soil moisture (VSM), and wind speed (WS) in the particular regions. For instance, the positive TAOD trend over the equatorial central Pacific is mainly attributable to the increased PPT and decreased WS. In contrast, in dry convective regions dominated by dust and smoke, the interannual variability/trend in TAOD is largely modified by the VSM driven by the PPT. Additionally, we further found these significant regional correlations are more robust within the PBL and significantly weakened or even reversed within the FT. This highlights the superiority of using the TAOD partitioned within the PBL as a proxy variable for the widely applied TAOD to explore the relationships between atmospheric pollution and meteorology.

This study utilized a long-term (2001-2018) aerosol optical component dataset retrieved from the Multiangle Imaging Spectroradiometer (MISR), Version 23, to perform comprehensive analyses of the global climatology of seasonal AODs, partitioned by aerosol types (including small-size, medium-size, large-size, spherical, and non-spherical). By dividing eight different AOD bins and performing trend analysis, the seasonal variability and trends in these type-segregated AODs, as well as in the frequency occurrences (FOs) for different AOD bins, globally and over 12 regions of interest, were also investigated. In terms of particle size, small-size aerosol particles (diameter0.7 μm) contribute the largest to global extinction in all three seasons except winter. A similar globally dominant role is exhibited by spherical aerosols, which contribute 68.5%, 73.3%, 71.6% and 70.2% to the global total AOD (TAOD) in spring, summer, autumn and winter, respectively, on a global average scale. FOs with different aerosol loading levels suggested that the seasonal FOs tend to decrease progressively with increasing aerosol loading, except for Level 1 (TAOD0.05). Examination of the seasonal distribution of FOs revealed that the FO at Level 1 (Level 2, 0.05TAOD0.15) is much larger in summer/winter (winter/autumn) than in spring/autumn (spring/summer) over most areas of the world. However, the FOs for Level 3 (0.15TAOD0.25) to Level 8 (TAOD1.0) generally exhibit greater intensity in spring/summer than in autumn/winter. Temporal trend analyses showed that the seasonal TAOD experiences a significant decline during 2001-2018 in most regions globally, except in South Asia, the Middle East, and North Africa. Opposite seasonal trends in the above regions are closely related to the increase in FOs in the range of 0.4TAOD1.0. The global average TAOD shows the most pronounced decline in spring, falling by -10.4% (P0.05). Examination of the trends in type-segregated AODs further revealed that the decreases in size-segregated (shape-segregated) AODs all contribute to the decrease in seasonal TAOD, with small-size AOD (spherical AOD) contributing most significantly.

This study used the MERRA-2 reanalysis dataset and ground-based and satellite observational data to comprehensively analyze a typical dust storm event in east Asia on 2−7 May 2017 which engulfed most of China as well as ocean and Japan, and explore the accuracy and comprehensiveness of the MERRA-2 dataset in the analysis of dust processes. The results of comparison show that the description of the spatiotemporal distribution and evolution of the dust aerosols in the dust event using the MERRA-2 data is consistent with the data of AERONET, National Urban Air Quality Real-time Publishing Platform and Hamawari-8. Gobi Deserts was the most influential source area of this dust event with the highest emissions reaching 1.9 × 106 μg/m3. The vertical motion of the atmosphere can lift dust from the source area above 500 hPa. There were low-pressure troughs at 500 and 850 hPa and the winds behind and in front of the trough led to the high-altitude, long-distance transport of dust. Dust gradually affected the northwest China, north China, northeast China, and even the ocean and Japan on 2−7 May. This study demonstrates that although there is some uncertainty about the source of dust emission in the MERRA-2 model, the data accurately simulated the evolution of the dust event and analyze it comprehensively, while the accuracy of simulating the long-term evolution of dust requires further evaluation.