Northeastern China Research Articles

Assessing global pine wilt disease risk based on ensemble species distribution models

Pine wilt disease (PWD), caused by the invasive pine wood nematode, is a major threat to global pine forests. This study utilized global PWD occurrence data alongside climatic, soil, and topographic variables to develop an ensemble of species distribution models. Using this ensemble model, we identified key factors influencing PWD and assessed the risk for current conditions and future periods (2041–2060 and 2071–2090) under three climate scenarios (SSP126, SSP370, and SSP585). The results indicate that key factors include the average temperature during the hottest quarter, clay content in soil, and precipitation during the hottest quarter, total annual precipitation, and precipitation during the coldest quarter. Currently, southern and northeastern China, central-southern Europe, and Southeast Asia are at high risks. With future climate changes, potential risk areas are expected to expand to higher latitudes, affecting regions like Hokkaido, Canada, and Northern Europe, especially under the SSP585 scenario. This study offers essential insights for global PWD prevention and forests resource conservation.

Mutations in target gene confers resistance to acetolactate synthase inhibitors in Echinochloa phyllopogon

Echinochloa phyllopogon is a noxious weed that can harm rice over prolonged periods. Recently, a penoxsulam-resistant variant of E. phyllopogon with a mutation in the acetolactate synthase (ALS) gene was collected in Northeastern China. In the present study, the molecular mechanism underlying herbicide resistance in mutant populations was evaluated. The GR50 and IC50 values of the herbicide-resistant mutant 1-11 were 27.0- and 21.4-fold higher than those of the susceptible population 2-31, respectively. In addition, pre-application of malathion reduced the GR50 value of the resistant population. Additionally, mutant populations developed cross-resistance to other ALS inhibitors. E. phyllopogon ALS sequencing showed a Trp-574-Leu mutation in ALS2 variant 1-11. Molecular docking showed that the Trp-574-Leu substitution reduced the number of hydrogen bonds and altered the interaction between penoxsulam and ALS2. Transgenic Arabidopsis plants harboring the ALS2 mutant gene also showed resistance to penoxsulam and other ALS inhibitors. Overall, our study demonstrated that the Trp-574-Leu mutation and P450-mediated metabolic resistance lead to the cross-resistance of E. phyllopogon to ALS inhibitors.

Contrasting foliar nitrogen nutrition of coexisting temperate and boreal trees across a modest temperature cline

The temperate-boreal forest ecotone represents a transition zone from temperate to boreal forest where nitrogen (N) is frequently limiting tree growth, which is highly sensitive to climate change. However, the spatial patterns and potential drivers of plant N nutrition and soil N availability remain poorly understood. To address this, we conducted a field investigation along a temperate-boreal forest ecotone in northeastern China, characterized by a modest mean annual temperature gradient (∼1°C) within the range of current climate warming. Our goal was to evaluate the spatial variation in foliar N nutrition and soil N availability, and the potential driving factors for Mongolian oak (Quercus mongolica) and Dahurian larch (Larix gmelinii), the dominant trees of the local temperate and adjacent boreal forests, respectively. Our results revealed no significant spatial trend in topsoil N availability across the sampling transect. Overall, foliar N concentration was significantly higher, but foliar δ15N was lower, for Mongolian oak than Dahurian larch. More important, foliar N concentration for Mongolian oak increased significantly toward the boreal forest, driven by lower mean annual temperatures and mean annual precipitation, with no significant trend observed for Dahurian larch. Additionally, foliar Δδ15N (foliar δ15N−soil δ15N) decreased significantly for Mongolian oak as it approached the boreal forest, while it increased significantly for Dahurian larch toward the temperate forest. Furthermore, the foliar N concentration, δ15N, and Δδ15N for Dahurian larch were all higher with an increasing basal area proportion of Mongolian oak. Our findings reveal contrasting patterns of foliar N nutrition between co-occurring temperate and boreal trees across a temperate-boreal forest ecotone which experiences a modest climatic gradient. These results underscore the importance of incorporating interspecific interactions to enhance our understanding of future N cycling in southern boreal forests in the context of climate warming.

Mineralogical Characteristics of Sapphire-Bearing Placers Associated with Cenozoic Alkali Basalts in Primorye and Northeastern China

Mineralogical Characteristics of Sapphire-Bearing Placers Associated with Cenozoic Alkali Basalts in Primorye and Northeastern China

Elucidating the Fundamental Process of Methyl-(5hydroxymethyl) Furan-2-Carboxylate Toxin Biosynthesis in Curvularia lunata Causing Maize Leaf Spot.

Maize leaf spot, which is caused by Curvularia lunata (Wakkre) Boedijn, was epidemic in the maize-growing regions of northeastern and northern China in the mid-1990s, where it led to large yield losses. Since then, the epidemic has evolved into a kind of common disease. In recent years, however, a tendency of becoming an epidemic disease again has been observed in some areas in China due to significant changes in climate, farming, systems and crop varieties. The significance of methyl-(5hydroxymethyl) furan-2-carboxylate (M5HF2C) as a nonspecific host toxin in causing maize leaf spot disease has been demonstrated in previous research. However, the key enzymes involved in M5HF2C toxin synthesis remain unclear. In our study, we demonstrate that the synthesis of M5HF2C toxin starts from a precursor substrate in the pathogen, furfural, which is then catalytically dehydrogenated into furoic acid via an alcohol dehydrogenase (CLADH6). The furoic acid was further confirmed as one of the raw materials for the biosynthesis of M5HF2C toxin based on deletion mutants of the alcohol dehydrogenase gene (Cladh6) in C. lunata, which had reduced M5HF2C toxin-producing ability; however, this ability could be restored in all deletion mutants through complementation with furoic acid, thereby confirming that furoic acid is an intermediate in the biosynthesis of M5HF2C toxin. In summary, the biosynthesis process of M5HF2C toxin in C. lunata involves three transformation steps: (1) from xylose to furfural; (2) then from furfural to furoic acid; and (3) eventually from furoic acid to M5HF2C toxin. Our research findings provide new clues in elucidating the major steps in the process of M5HF2C toxin biosynthesis in C. lunata.

Neighborhood structure, more than soil nutrients, influences net tree interactions among different functional types in a temperate forest

Tree-tree interactions are fundamental in shaping forest community dynamics, driven by factors such as nutrient availability and species composition. While recent research underscores the role of functional traits in influencing tree sensitivity to neighborhood interactions, a clear consensus is lacking on how these traits interact with biotic and abiotic factors. Based on a multi-level modeling approach, this study examines how specific leaf area (SLA), potential maximum tree height (Hmax), and wood density (WD) mediate the combined effects of soil nutrients and neighborhood biotic factors on net tree interactions among 4,210 individual stems for 13 species in a 30-ha temperate forest in northeastern China. The findings indicate that while functional traits independently account for a small portion of the variation in net tree interaction intensity (NIntC), they significantly mediate the effects of neighborhood crowding, neighborhood structure, and soil nutrients on NIntC. Specifically, only the response of growth NIntC of species with low-Hmax to available phosphorus (AP) was consistent with the stress gradient hypothesis. Conspecific neighborhood crowding consistently increases competitive NIntC, whereas heterospecific neighborhood crowding significantly facilitates survival NIntC. Moreover, the positive impact of heterospecific crowding on survival NIntC is significantly greater for high-Hmax species compared to low-Hmax species. Neighborhoods with higher tree species diversity, greater size heterogeneity, and more uniform distribution increase the facilitative NIntC of high-SLA or high-WD species but intensify the competitive NIntC of low-SLA or low-WD species. Our results also indicate that the relative importance of neighborhood structure exceeds that of soil nutrients in explaining variation in NIntC. When environmental conditions are difficult to change, adjusting the forest stand structure may be a more efficient way to regulate the intensity of interactions between trees and improve forest productivity.

Impacts of short-term rainfall and snowfall exclusions on hydraulic, economic and stomatal traits of Larix gmelinii in northeastern China

Impacts of short-term rainfall and snowfall exclusions on hydraulic, economic and stomatal traits of Larix gmelinii in northeastern China

Relationships between Tree Species Diversity and Aboveground Biomass Are Mediated by Site-Dependent Factors in Northeastern China Natural Reserves on a Small Spatial Scale

Relationships between Tree Species Diversity and Aboveground Biomass Are Mediated by Site-Dependent Factors in Northeastern China Natural Reserves on a Small Spatial Scale

Characteristics and risk assessments of mercury pollution in a county region undergoing industrialization in northeastern China: a case study in Gongzhuling

Mercury pollution in emerging industrial zones and surrounding areas, especially in industrial concentration areas, has attracted much attention. So as to clarify the characteristics of Hg in the environment in China’s small and medium-sized industrial emerging and surrounding areas, central urban area of Gongzhuling, a traditional agricultural town with a high degree of industrialization in northeast Changchun industrial base, is taken as the scope. Geological accumulation trin (Igeo) was used to study the degree of soil mercury contamination in Gongzhuling area, latent Er (ecological risk) trin was used to appraise the Er of soil Hg in the study area, and non-carcinogenic risk assessment of mercury in soil using human exposure risk assessment model. The results showed that 34% of soil samples had higher Hg content than the background value of the province’s soil (0.04 mg kg−1). The Igeo results showed that Hg pollution rate of soil in study area was 9% (index >0). In conclusion, the level of soil Hg pollution in Gongzhuling area was low, and the pollution area is mainly concentrated in the northwestern part of the study range. The highest and lowest Er values of soil Hg from the study sample were 2.23 and 214.83, and 24% of the samples had Er > 40, that means they pose a moderate or higher potential ecological risk, and most of these points are located in the northeast of the study range. The main route of human exposure to Hg is oral ingestion. The HQ (non-carcinogenic risk index) and HI (total non-carcinogenic risk value) of soil mercury were both much less than 1, it indicates that the present level of soil Hg in the study range does not pose a threat to local adult health for the time being. This study provides reference for other urban pollution risk assessment, and further defines the direction of future work.

Microbiota profile in organs of the horseflies (Diptera: Tabanidae) in Northeastern China.

Tabanids, commonly known as horseflies and belonging to the family Tabanidae, are blood-feeding arthropods (BFA) found worldwide. They are known for their ability to mechanically and biologically transmit various animal pathogens. Tabanids are potential vectors for diseases such as Francisella tularensis, Anaplasma marginale, Theileria spp., and contributors to lumpy skin diseases. Despite their involvement in common BFA studies, tabanids have not been extensively explored in microbiome research. In this study, the microbiota structure and composition in various organs of four distinct genera of tabanids: Atylotus, Haematopota, Tabanus, and Hybomitra were examined. High-throughput sequencing of the bacterial 16S rRNA gene was performed to gain insights into the microbial communities associated with the different tabanid species. Result display that microbiota composition and diversity, including Firmicutes, Proteobacteria, and Bacteroidetes, varied significantly among the different organs, with the ovaries exhibiting significantly higher diversity. Apart from the Haematopota genus, Tenericutes were enriched in the midgut of other tabanid species, whereas the Malpighian tubules exhibited a higher abundance of Bacteroides. Notably, the ovarian microbiota structure was conserved among the four tabanid species, indicating its potential association with reproductive development. Evaluation of the potential pathogen risk revealed putative pathogens in over 100 genera associated with these tabanid commensal organisms. Twenty genera were annotated as zoonotic agents with a high abundance of Citrobacter and Brucella, highlighting the presence of this important group of zoonotic pathogens. Functional predictions of vector-microbiota interactions indicate that microbiota significantly affects vector biological traits and can influence pathogen transmission via direct interactions or by regulating host immunity and nutrition. For the first time, the distribution characteristics and functions of four genera of horsefly microbiota were analyzed, revealing the presence of multiple potential pathogenic microorganisms. These findings provide valuable insights for future research and the development of symbiotic-based strategies to control insect-borne diseases among tabanids.

A Pn-wave spectral inversion technique based on trust region reflective algorithm

This paper suggests utilizing the trust region reflective (TRR) algorithm to address the inverse problem related to seismic spectrum analysis of Pn waves. By applying this approach, it becomes feasible to simultaneously deduce the seismic moment, corner frequency, tomographic model of Pn-wave attenuation, and site responses while incorporating appropriate constraints based on prior knowledge to ensure solution accuracy. The efficacy of this method has been validated using synthetic data. Specifically, the recorded Pn waves from four underground explosions in North Korea were employed to evaluate the performance of the proposed technique. The derived seismic moment and corner frequency for these events were found to align with the characteristics of the seismic data, earthquake magnitude calculations, and empirical data. The resulting tomographic model of Pn-wave attenuation revealed a spatial distribution of high and low attenuation, indicating significant lithospheric heterogeneity in northeastern China. Areas with low Q0 and low η, such as the Xialiaohe Basin and southwestern Changbai Mountain, suggest a high-temperature environment in the upper mantle cap layer or the presence of molten substances. Conversely, regions with high Q0 and high η, like the northern Changbai Mountain and the vicinity of the eastern Tanlu Fault Zone, characterized by high Pn-wave velocity and thick crust, indicate minimal modification or destruction in the lithosphere. Furthermore, site responses were determined for 75 seismic stations in northeastern China, with their characteristics preliminarily analyzed and interpreted in conjunction with geological context. The iterative process based on the TRR algorithm for Pn-wave spectral inversion proposed in this study demonstrates robust convergence and enhances the fitting accuracy of the observed spectrum. The inversion outcomes from this spectral technique yielded synthetic Pn-wave spectra that closely matched the observed spectra of the four underground explosions in North Korea across various frequency bands for over 90 % of the stations.

The Impacts of Urban Population Growth and Shrinkage on the Urban Land Use Efficiency: A Case Study of the Northeastern Region of China

In the context of rapid urbanization, urban population differentiation has become increasingly pronounced. Regional development strategies based on growth scenarios often lead to continuous expansion, regardless of urban population status. Such “one-size-fits-all” models exacerbate resource waste and negatively impact urban land use efficiency (ULUE). This study aims to explore the mechanisms by which urban population growth and shrinkage (UPGS) affect ULUE, with the goal of enhancing ULUE and promoting sustainable urban development. We analyzed 34 prefecture-level cities in China’s three northeastern provinces. First, we identified UPGS using population data. We then employed a three-stage SBM-DEA model to measure ULUE from 2000 to 2020. Spatial analysis methods were used to examine the spatiotemporal characteristics and correlations between UPGS and ULUE. Additionally, mediating effect models and spatial Durbin models were utilized to empirically test the impact processes, mechanisms, and spatial heterogeneity. Our findings reveal that: (1) Over the past 20 years, urban population shrinkage in northeastern China has intensified, and significant regional disparities in urban development are evident. (2) Population growth positively influences ULUE, while population shrinkage inhibits its improvement. (3) Economic development, technological innovation, and industrial structure upgrading are key factors in enhancing ULUE in this region, while the impact of public services on ULUE varies significantly at different stages of urban development. (4) Economic development, technological innovation, and industrial structure upgrading exhibit spatial spillover effects, whereas public services are constrained by regional limitations, resulting in minimal spatial spillover effects. To foster coordinated regional development, this study proposes policy recommendations, including strengthening support for resource-dependent cities, optimizing the allocation of public resources, and promoting technological innovation and industrial diversification.

Source Apportionment and Risk Assessment of Potentially Toxic Elements Based on PCA and PMF Model in Black Soil Area of Hailun City, Northeast China.

This study assessed the presence of potentially toxic elements (PTEs) in China's northeastern black soil belt, an area with limited prior research. We collected 304 soil samples (0-20 cm) from Gonghe Town, Hailun City, and analyzed the PTE contamination degree using the single-factor pollution index and Nemerow pollution index. The results demonstrated that the mean concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn) were 11.16, 0.11, 65.29, 22.56, 0.03, 27.07, 26.09, and 66.01 mg/kg, respectively. Source apportionment was conducted via correlation analysis, principal component analysis, and positive matrix factorization, identifying four main sources: natural (33.2%), irrigation (29.5%), fuel (23.4%), and fertilizer (13.2%). The ecological risk index indicated a slight ecological risk, while the human health risk showed that non-carcinogenic risks were negligible and carcinogenic risks were acceptable. Our findings emphasize the need to prioritize controlling PTEs from fertilizer, particularly cadmium, and to a lesser extent, irrigation and fuel sources, focusing on As, Pband Hg. This research provides critical insights for policymakers aiming to manage PTE contamination in black soils.

Comparison of chemical components and quality evaluation of Panax ginseng and its processed products from different habitats in Northeastern China

Ginseng (Panax ginseng C.A. Meyer) is a widely used dietary supplement in Traditional Chinese Medicine due to its numerous health-promoting properties. However, limited research is available on the distinctions in the chemical composition between different ginsengs. Hence, this study explores the chemical composition of different ginsengs obtained from different habitats in Northeastern China. The fresh, red, and white ginsengs were collected from different places in the Jilin province, China. Ginsenoside and non-ginsenoside contents in the ginseng extracts were analyzed by an Ultra-high performance liquid chromatography system & VION® ion mobility hybrid Quadrupole Time-of-Flight. The results show a notable difference in the ginsenoside content among the samples. The qualification ratio of ginsenoside Re, Rg1, and Rb was 46.2%, with Re being the most abundant, followed by Rg1 and Rb1 in all the ginseng analyzed. Furthermore, the study revealed that white and red ginseng had higher total ginsenosides (8.18 ± 0.04 mg/kg) and total polysaccharides (17.4%) content, respectively. The fresh ginseng samples exhibited higher protein content (20.02 ± 0.2 g/100g) and lower fat content (2.0 g/100g) than others. Further, the ginseng samples analyzed in this study met the requirements specified in the Chinese Pharmacopoeia for total ash, heavy metals, and organochlorine pesticide residues. This study offers a comprehensive comparative analysis of the chemical composition of P. ginseng sourced from various habitats in Northeastern China. It underscores the significance of making informed choices when selecting ginseng types for scientific evaluation.

Changes in Spatiotemporal Pattern and Its Driving Factors of Suburban Forest Defoliating Pest Disasters

Forest defoliating pests are significant global forest disturbance agents, posing substantial threats to forest ecosystems. However, previous studies have lacked systematic analyses of the continuous spatiotemporal distribution characteristics over a complete 3–5 year disaster cycle based on remote sensing data. This study focuses on the Dendrolimus superans outbreak in the Changbai Mountain region of northeastern China. Utilizing leaf area index (LAI) data derived from Sentinel-2A satellite images, we analyze the extent and dynamic changes of forest defoliation. We comprehensively examine the spatiotemporal patterns of forest defoliating pest disasters and their development trends across different forest types. Using the geographical detector method, we quantify the main influencing factors and their interactions, revealing the differential impacts of various factors during different growth stages of the pests. The results show that in the early stage of the Dendrolimus superans outbreak, the affected area is extensive but with mild severity, with newly affected areas being 23 times larger than during non-outbreak periods. In the pre-hibernation stage, the affected areas are smaller but more severe, with a cumulative area reaching up to 8213 hectares. The spatial diffusion characteristics of the outbreak follow a sequential pattern across forest types: Larix olgensis, Pinus sylvestris var. mongolica, Picea koraiensis, and Pinus koraiensis. The most significant influencing factor during the pest development phase was the relative humidity of the year preceding the outbreak, with a q-value of 0.27. During the mitigation phase, summer precipitation was the most influential factor, with a q-value of 0.12. The combined effect of humidity and the low temperatures of 2020 had the most significant impact on both the development and mitigation stages of the outbreak. This study’s methodology achieves a high-precision quantitative inversion of long-term disaster spatial characteristics, providing new perspectives and tools for real-time monitoring and differentiated control of forest pest infestations.

Wind erosion prevention and trans-boundary ecosystem service payments in the Hunshandake region

Research on ecosystem services flow has attracted increasing interest as they provide essential knowledge to payments for ecosystem services (PES) by developing the spatial relationship between service benefit area and service providing area. In this study, we calculated the wind erosion prevention service (WEPS) in the Hunshandake region using the RWEQ model, simulated the WEPS flow trajectories using the HYSPLIT model, investigated the flow process of WEPS and its monetary values to develop the relationship between the beneficiary areas and the Hunshandake region, with the aim of proposing an integrated PES framework that links beneficiary areas to the Hunshandake region. The results indicated that the WEPS in the Hunshandake region were 2.67 × 1012 kg yr−1, 2.18 × 1012 kg yr−1, and 3.26 × 1012 kg yr−1 in 2010, 2015 and 2018, respectively, and their monetary values were 3.94 × 109 USD yr−1, 3.50 × 109 USD yr−1, and 4.93 × 109 USD yr−1, respectively. Most WEPS were transferred along the track to northern and northeastern China and continued on to Mongolia, Russia, North Korea, South Korea and Japan, while some were transported through central and eastern China to southern China and Southeast Asian countries. The Chinese beneficiary regions received between 69.75% and 70.81% of the total transferred WEPS from the Hunshandake region, with beneficiary countries outside of China receiving the remainder. We developed an integrated ecological payment framework based on the transferred values of WEPS and their demands in the beneficiary areas. The total payments for WEPS from beneficiary areas were 503.91 × 106 USD yr−1, 422.83 × 106 USD yr−1, and 609.18 × 106 USD yr−1 in 2010, 2015 and 2018, respectively. The ecological payments due from the beneficiary countries except China, the beneficiary provinces in China and the actual payments made as ecological fiscal transfers (EFT) from the Government of China; their percentages were 10.24%, 35.42% and 54.34%, respectively. Actualization of payments from benefitting countries and provinces within China were simulated with the percentage of EFT to the total transferred benefits in China decreasing from 60.54% to 40% and 20%; the value of payments from government would then reduce from 95.71 × 106 USD yr−1 to 63.24 × 106 USD yr−1 and 31.62 × 106 USD yr−1, respectively, alleviating the financial burden of government substantially. This study could provide a scientific basis for the government of China to formulate policies for payments from beneficiary provinces to Hunshandake region within China and facilitate negotiations with other countries on their potential payments to Hunshandake region providing WEPS to their benefit.

Assessing the destabilization risk of ecosystems dominated by carbon sequestration based on interpretable machine learning method

Increasing carbon sequestration (CS) in soils and biomass is an important land-based solution in mitigating global warming. Ecosystems provide a wide range of ecosystem services (ESs). The necessity to augment CS may engender alterations in the interrelationships among ESs, thereby heightening the probability of ecosystem destabilization. This study developed a framework that integrates machine learning and interpretable predictions to evaluate the destabilization risk resulting from alterations in ecosystem service relationships dominated by CS. We selected Northeastern China as study area to estimate six ESs and identified areas of destabilization risk among the three services most relevant to CS, including food production (FP), soil retention (SR), and habitat quality (HQ). Subsequently, we compared three machine learning models (random forest, extreme gradient boosting, and support vector machine) and introduced the Shapley additive interpretation (SHAP) method for driving mechanism analysis. The results showed that: (1) CS-FP had 30.28% of its area at destabilization risk and is the most significant ecosystem service pair; (2) Heilongjiang Province was the region with the highest destabilization risk of CS, with CS-FP and CS-SR accounting for 44.76% and 52.89% of all regions, respectively; (3) a non-linear relationship and the presence of threshold features between socio-ecological factors and the prediction of destabilization risk. The study has potential practical value for destabilization risks prevention, while also providing a scientific basis for formulating comprehensive carbon management policies and maintaining ecosystem stability.

Freeze-thaw resistance and service life prediction of fly ash incorporated ultra-high ductility magnesium phosphate cement-based composites

To develop ultra-high ductility magnesium phosphate cement-based composites (UHDMC) suitable for cold areas and fully utilize solid waste, the effects of fly ash (FA) substitution and freeze-thaw cycles on the mechanical properties and freeze-thaw resistance of UHDMC specimens were explored. The mechanism of freeze-thaw damage was revealed by mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM). Freeze-thaw damage model for UHDMC was established to predict its service life. The results showed that, after 300 freeze-thaw cycles, the compressive strength retention rate of the UHDMC specimens with FA substitution from 10 % to 30 % was above 88.7 %, and the tensile strain maintained above 3.48 %, still presenting the characteristics of multi-cracking and strain hardening. Meanwhile, after 600 freeze-thaw cycles, the mass loss rate and the dynamic elastic modulus of UHMPC specimens with FA substitution from 10 % to 30 % were below 1.38 % and above 81.1 %, respectively. The mechanical properties were mainly related to the total porosity and macropores. The effect of the water solubility of prismatic struvite-K crystals and the secondary hydration production of filamentous struvite potassium crystals on the matrix presented well explanation for the excellent freeze-thaw resistance of UHDMC specimens with FA substitution from 10 % to 30 %. At last, a freeze-thaw damage model for UHDMC specimens with FA substitution below 30 % based on the Weibull probability distribution function was established, predicting that their service life was up to 232 years in the northeastern of China.

Changes in urban residential and agricultural sources induce a decrease in PM10 levels in cold clean area: A thirteen-year monitoring at the Longfengshan WMO/GAW regional background station in Northeast China

Atmospheric background monitoring provides insights into the long-term changes in atmospheric composition resulting from human activities on both global and regional scales. It is important to understand the local characteristics of key air pollutants to evaluate and manage air quality control policies effectively. This study analyzed 13 years of continuous data of PM10 (particulate matter with aerodynamic diameter ≤10 μm) concentration from the only atmospheric background station in Northeastern China, the Longfengshan (LFS) World Meteorological Organization (WMO)/Global Atmosphere Watch (GAW) regional station. The results revealed a significant decrease of 58.02% in PM10 concentrations in the LFS from 2007 to 2019, which was primarily influenced by transport from Changchun and Harbin. Over periods exceeding eight months, the correlation between PM10 levels at the LFS atmospheric background station and those in Changchun and Harbin became more pronounced. The observed decline in PM10 concentrations at the LFS atmospheric background station was largely attributed to reduced emissions from urban residential and agricultural sources. Emissions of carbon monoxide and ammonia from these sources, along with temperature and relative humidity (RH), significantly affected the PM10 concentrations. Using machine learning (ML) methods and PM10 data from the LFS atmospheric background station, this study effectively predicted PM10 concentrations in neighboring cities, demonstrating that the LFS atmospheric background station can effectively assess the trend of PM10 changes in Northeast China. This study quantified the influence of urban areas on atmospheric background stations, highlighting the effectiveness of existing environmental policies, and offering a reference for similar studies and forecasts in other regions.

Tropical tropospheric ozone distribution and trends from in situ and satellite data

Abstract. Tropical tropospheric ozone (TTO) is important for the global radiation budget because the longwave radiative effect of tropospheric ozone is higher in the tropics than midlatitudes. In recent decades the TTO burden has increased, partly due to the ongoing shift of ozone precursor emissions from midlatitude regions toward the Equator. In this study, we assess the distribution and trends of TTO using ozone profiles measured by high-quality in situ instruments from the IAGOS (In-Service Aircraft for a Global Observing System) commercial aircraft, the SHADOZ (Southern Hemisphere ADditional OZonesondes) network, and the ATom (Atmospheric Tomographic Mission) aircraft campaign, as well as six satellite records reporting tropical tropospheric column ozone (TTCO): TROPOspheric Monitoring Instrument (TROPOMI), Ozone Monitoring Instrument (OMI), OMI/Microwave Limb Sounder (MLS), Ozone Mapping Profiler Suite (OMPS)/Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2), Cross-track Infrared Sounder (CrIS), and Infrared Atmospheric Sounding Interferometer (IASI)/Global Ozone Monitoring Experiment 2 (GOME2). With greater availability of ozone profiles across the tropics we can now demonstrate that tropical India is among the most polluted regions (e.g., western Africa, tropical South Atlantic, Southeast Asia, Malaysia and Indonesia), with present-day 95th percentile ozone values reaching 80 nmol mol−1 in the lower free troposphere, comparable to midlatitude regions such as northeastern China and Korea. In situ observations show that TTO increased between 1994 and 2019, with the largest mid- and upper-tropospheric increases above India, Southeast Asia, and Malaysia and Indonesia (from 3.4 ± 0.8 to 6.8 ± 1.8 nmol mol−1 decade−1), reaching 11 ± 2.4 and 8 ± 0.8 nmol mol−1 decade−1 close to the surface (India and Malaysia–Indonesia, respectively). The longest continuous satellite records only span 2004–2019 but also show increasing ozone across the tropics when their full sampling is considered, with maximum trends over Southeast Asia of 2.31 ± 1.34 nmol mol−1 decade−1 (OMI) and 1.69 ± 0.89 nmol mol−1 decade−1 (OMI/MLS). In general, the sparsely sampled aircraft and ozonesonde records do not detect the 2004–2019 ozone increase, which could be due to the genuine trends on this timescale being masked by the additional uncertainty resulting from sparse sampling. The fact that the sign of the trends detected with satellite records changes above three IAGOS regions, when their sampling frequency is limited to that of the in situ observations, demonstrates the limitations of sparse in situ sampling strategies. This study exposes the need to maintain and develop high-frequency continuous observations (in situ and remote sensing) above the tropical Pacific Ocean, the Indian Ocean, western Africa, and South Asia in order to estimate accurate and precise ozone trends for these regions. In contrast, Southeast Asia and Malaysia–Indonesia are regions with such strong increases in ozone that the current in situ sampling frequency is adequate to detect the trends on a relatively short 15-year timescale.